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Preparation, regulation and biological application of a Schiff base fluorescence probe
Accepted Manuscript Title: Application of carbohydrate polymers as corrosion inhibitors for metal substrates in different media: A review Author: Saviour A. Umoren Ubong M. Eduok PII: DOI: Reference:
S0144-8617(15)01216-3 http://dx.doi.org/doi:10.1016/j.carbpol.2015.12.038 CARP 10636
To appear in: Received date: Revised date: Accepted date:
19-9-2015 11-12-2015 15-12-2015
Please cite this article as: Umoren, S. A., and Eduok, U. M.,Application of carbohydrate polymers as corrosion inhibitors for metal substrates in different media: A review, Carbohydrate Polymers (2015), http://dx.doi.org/10.1016/j.carbpol.2015.12.038 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Highlights
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-Different carbohydrate polymers used as metal corrosion inhibitors have been discussed
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-Effect of halide ion additives on corrosion inhibition with carbohydrate polymers highlighted
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- Mechanism of inhibition action by the carbohydrate polymers highlighted
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- Theoretical approach to corrosion monitoring have been recommended for future studies
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Application of carbohydrate polymers as corrosion inhibitors for metal
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substrates in different media: A review
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Saviour A. Umoren1*, Ubong M. Eduok2
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Petroleum & Minerals, Dhahran 31261, Saudi Arabia.
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Saudi Arabia
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Abstract
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Naturally occurring polysaccharides are biopolymers existing as products of biochemical
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processes of living systems. A wide variety of them have been employed for various material
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applications; as binders, coatings, drug delivery, corrosion inhibitors etc. This review describes
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the application of some green and benign carbohydrate biopolymers and their derivatives for
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inhibition of metal corrosion. Their modes and mechanisms of protection have also been
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described as directly related to their macromolecular weights, chemical composition and their
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unique molecular and electronic structures. For instance, cellulose and chitosan possess free
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amine and hydroxyl groups capable of metal ion chelation and their lone pairs of electrons are
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readily utilized for coordinate bonding at the metal/solution interface. Some of the carbohydrate
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Center of Research Excellence in Corrosion, Research Institute, King Fahd University of
Department of Chemistry, King Fahd University of Petroleum & Minerals, Dhahran 31261,
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polymers reviewed in this work is either pure or modified forms; their grafted systems and
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nanoparticle composites with multitude potentials for metal protection applications have also
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been highlighted. Few inhibitors grafted to introduce more compact structures with polar groups
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capable of increasing the total surface energy of the surface have also been mentioned. Exudate
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gums,
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substituted/modified chitosans, carrageenan, dextrin/ cyclodextrins and alginates have been
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elaborately reviewed, including the effects of halide additives on their anticorrosion
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performances. Aspects of computational/theoretical approach to corrosion monitoring have been
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recommended for future studies. This non-experimental approach to corrosion could foster a
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better understanding of the corrosion inhibition processes by correlating actual inhibition
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mechanisms with molecular structures of these carbohydrate polymers.
hydroxyethyl
cellulose,
starch,
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Keywords: Carbohydrate polymers; Green inhibitors; Polysaccharides; Corrosion; Metal substrates; Corrosion inhibition. * Corresponding author. Email: [email protected]; Tel.: +966-3-8609702; Fax: +966-38603996.
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carboxymethyl
Table of contents
Pages
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Introduction …………………………………………………………………………………. 2
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Green carbohydrate polymers application for metal protection…………………………….. 5
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Exudate gums……………………………………………………………………… 6
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Carboxymethyl and Hydroxyethyl cellulose……………………………………… 11
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Starch……………………………………………………………………………… 15
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Pectin and pectate………………………………………………………………….. 18
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Chitosan and substituted/modified chitosans……………………………………..
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Carrageenan………………………………………………………………………
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Greenness: A prerequisite requirement for selection of inhibitor compounds……. 3
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Dextrin and cyclodextrins……………………………………………………….
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Alginates…………………………………………………………………………
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Effect of halide ion additives on corrosion inhibition with carbohydrate polymers…….
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Future perspective: computational approach to corrosion evaluation…………………..
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Concluding remarks……………………………………………………………………..
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References……………………………………………………………………………….
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Introduction
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Metals corrode, and this electrochemical process has huge implication on their end-use and
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consequently, the economics of maintenance and repairs for industrial applications. Several
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forms of corrosion products and all possible reactions, including stable phases, are revealed in
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the Pourbaix diagram of metals showing their susceptibility to corrosion depending on the pH.
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The rate of metal corrosion is greatly influenced by substrate and surface chemistries as well as
69
some environmental influences (e.g. temperature, solution concentration (pH) etc.), and by
70
understanding these factors, adequate control method can be employed to revert its degradation
71
kinetics. By studying corrosion, researchers worldwide aim at discovering more reliable methods
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and strategies of preventing, or at least minimizing its spontaneous dynamics. The use of
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corrosion inhibitor compounds (single/multiple component, composites and blends etc.) is by far
74
one of the most applied corrosion control strategy in oil-fields. This operation is effective if the
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adsorption mechanism(s) of the adsorbed inhibitor compound at the metal surface is rightly
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defined. Generally, a common mechanism of action of most inhibitor compounds involves the
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formation of passivation layer that prevents the passage of corrosive ions to the metal surface.
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However, the effectiveness of this layer depends on the environment to which the compound has
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been applied, the metal type as well as the fluid composition, quantity of water, and flow regime
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(Gräfen et al. 2002). Normally in the field, these compounds are added in small concentrations to
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coolants, hydraulic fluids, or any other fluid (liquid or gas) surrounding the metal substrate,
82
like alkylaminophosphates and zinc dithiophosphates in fuel oil. Phosphates, and other inorganic
83
substances (e.g. chromates, dichromate and arsenates) are known to have detrimental
84
environmental effect and man health impact, as such their usage is against modern safety
85
regulation for the industrial chemicals with severe criticism. Currently, there is an increasing
86
quest for limiting field applications involving toxic compounds, hence the search for greener
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alternatives by reformulating the existing products or by identifying new chemistries for
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developing safer products (Killaars and Finley 2001).
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Greenness: A prerequisite requirement for selection of inhibitor compounds
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The general requirements of the selection of compounds are not limited to the chemical
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structural pre-requite in Scheme 1, but must also include eco-friendliness and benignity (Umoren
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et al. 2009a; Okafor et al. 2008; Umoren et al 2008a; Obot et al. 2009; Umoren et al. 2011). In
93
recent times, owing to global interest on environment safety as well as the effect of impacting
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industrial activities of man’s health and ecological balance, the use of toxic chemicals and
95
operations that emit them have been minimized. On this note, the inorganic inhibitors and some
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of their hazardous organic counterparts, though effective for the reduction of metal corrosion at
97
lower concentration, are gradually replaced by greener substances. Generally, eco-friendly, or
98
simply green, corrosion formulations (inhibitors and coatings) are those chemical products that
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meet the required reduced level of hazardous substance generation, and the processes involving
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their usage are governed by sustainable chemistry without direct or indirect negative
101
environmental or health impacts. Since recommended anticorrosive coating systems are expected
102
to be green and purely cured granules/powders with very low volatile organic compound (VOC)
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content and without heavy metals, their inhibitor counterparts should also meet these green label
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compliant standards. With the banning of chromates, corrosion control programs with greener
105
inhibitor compounds (chromate-free inhibitor formulations) in most oil field applications are
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designed to effectively meet safety standards and also efficiently protect the targeted metal
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substrates in their service environments. Health defects of chromates ranges from mild skin
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allergic reactions and rashes to nasal bleeding; with arsenates, alteration of genetic material may
109
occur at higher dosages as well as nervous breakdown and cancer. The US National Institute for
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Occupational safety and Health (NIOSH) have reduced the permissible exposure limit (PEL) for
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arsenates and chromates to 0.002 and 0.05 milligrams per cubic meter of air, respectively.
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(https://www.osha.gov/OshDoc/data_General_Facts/hexavalent_chromium.pdf;https://www.cdp
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h.ca.gov/programs/hesis/Documents/arsen2.pdf).
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Scheme 1. General pre-requite requirements for the selection of inhibitor compounds.
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Green carbohydrate polymers application for metal protection
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Organic corrosion inhibitors are generally used as replacements for inorganic compounds
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in the control of dissolution of the metals in aqueous media. Huge interest in this class of
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compounds has continued to grow in the last decade as naturally occurring and some synthetic
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biopolymers as well as their products meet the environmental requirements for safe product
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application with good corrosion inhibiting potential with infinitesimally small/reduced or zero
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pollution risk. Carbohydrate polymers are widely used as metal linings, and protective coatings.
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In corrosion inhibition, they represent a set of chemically stable, biodegradable and ecofriendly
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macromolecules with unique inhibiting strengths and mechanistic approaches to metal surface
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and bulk protection (Raja et al. 2013), with those extracted from natural sources (e.g. floral)
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regraded as low cost, renewable and readily available alternatives with essential and active 5
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ingredients responsible for the corrosion inhibition (Rahim et al. 2008). Generally, some of these
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carbohydrate biopolymers are relatively high molecular mass compounds with unique colloidal
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properties. Gum Arabic, for instance, readily forms low viscous suspensions and/or gels that can
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absorb water to a great extent when dissolved in appropriate solvent (Umoren et al. 2006). In
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solution, since the initial adsorption of inhibitor compounds could be affected by foreign surface
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active molecules, the potential of these polymers to actually reduce corrosion on the surface of a
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metal depends also on the adhesion of their moieties on the metal surface, either by physical
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forces or chemical bond. To really understand the surface chemistry, the potential for inhibition
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of these compounds is explained in terms of their macromolecular weights, chemical
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composition and the nature of the substrate’s surface. Some carbohydrate biopolymers normally
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can restrict the rate of anodic dissolution by forming blankets on the metal surface or deters
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associated cathodic reactions by active site blocking which may largely also depend on nature
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(structural and chemical characteristics) of the adsorption layers formed (Eddy et al. 2009;
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Umoren et al 2014, 2015a). Scheme 2 shows possible mechanisms of inhibition with
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carbohydrate biopolymers (Arthur et al. 2013). Because of their versatility as non-metallic
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materials, some carbohydrate biopolymers are widely replacing corrosive resistance alloyed
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steels and nonferrous metals in many industrial applications with anticorrosion roles especially in
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protection of metal parts (e.g. screws) subjected to corrosion, erosion and cavitation (Klinov
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1962).
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Scheme 2. Possible mechanisms of inhibition with carbohydrate polymers.
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This unique class of polymers has been widely reported as corrosion inhibitors due to their
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enormous functional groups and their ability to complex with ions of metals at surfaces. By
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covering large surface areas of metals in aqueous media, these complexes virtually “blankets” 6
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the surface from attack by corrosive molecules and ions thereby offering the needed protection.
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The efficacy of carbohydrate biopolymers as inhibitors varies with their class depending on their
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molecular weights, cyclic rings as well as the availability of bond-forming groups (e.g. sulphonic
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acid groups) and abundance of centers of adsorption (e.g. heteroatoms) (Rajendran et al. 2005).
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The presence of non-bonded/lone pairs of electrons (as well as pi electrons) on the molecules of
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these polymeric compounds allows for inhibitor-metal electron transfer with formation of bond
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whose strength is a function of the polarizability of the electron-donating group.
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Exudate gums
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Exudate gums are generally viscous tree (not excluding larger shrub) polysaccharides secretions
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that feel relatively moisten and/or sticky when wet and harden when they are dried. This unique
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physical property makes them useful oil and gas industrial adhesives and binders (Chaires-
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Martínez et al. 2008); and are used in the food industries as hydrocolloids due to their thickening
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and stabilizing properties (Douiare and Norton 2013). Gums are also widely used as
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microencapsulating agents in pharmaceuticals. Their solubility aids their usage as gelling and
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emulsifying agents as well. Depending on their compositions and floral sources, some gums
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possess faint to very pungent scents, and are generally soluble in water with gentle stirring in
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small concentrations. It is not strange that some galactomannan gums are also found in few
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leguminous seed endosperm like locust bean and guar gums extracted from Ceratonia siliqua
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and Cyamopsis tetragonoloba, respectively (Busch et al. 2015). Researches involving various
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gum types, both natural and synthetic, abound in the literature. Kim et al (2015) have
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investigated the solubility of three gum types from tapioca starch pastes, Gum arabic, k-
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carrageenan, gellan in water, alongside solvent effect on their humidity stability and mechanical
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properties. The degradation of locust bean gum by ultrasonication at room temperature has been
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studied by Li and Feke (2015) with the rate of aqueous dissociation observed to be dependent on
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changes on molecular conformation of the gum as well as ionic conditions in the saline media
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used. Depending on the gum type, their intrinsic viscosities are widely studied by simple
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rheological measurements. Gums are either natural or synthetic with varying viscosities and
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compositions. Natural gums are classified based on their sources; they are either charged (ionic;
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e.g. Agar extracted from seaweeds) or virtually uncharged (e.g. Guar gum from Guar bean seeds)
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polymers. Because of their unique chemical composition, gums from natural sources are
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effective corrosion inhibitors, and their evolution has greatly attracted attention considerably in
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the corrosion field. Gums of this class are greener, and renewable, without threat to the
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environment to which they are used (Umoren et al. 2006). Gum Arabic (GA) has been employed
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as corrosion inhibitor for some metal substrates, and available reports in the literature show that
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it protects metals to a great extent in aqueous acid and alkaline media. GA is water soluble, a
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dirty sticky and wet exudate extracted from Acacia tree (Leguminosae) sap material; and it is a
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mixture of some polysaccharides, sucrose, oligosaccharides, arbinogalactan and glucoproteins
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conceived to have the needed corrosion inhibition potential for metal substrate protection
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(Verbeken et al. 2003). The use of GA for aluminium and mild steel corrosion inhibitor in 1M
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sulphuric acid has been reported using the classical corrosion monitoring techniques (Umoren
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2008). Results from weight loss and thermometric techniques revealed that GA protected both
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metals remarkably in the solution of the aerated acid with the inhibition efficiency (% η ) and the
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degree of surface coverage (θ) increasing with the concentration of GA. Physical and chemical
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adsorption mechanisms where proposed for MS and Al corrosion, respectively, in the presence
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of GA, and its spontaneous adsorption was approximated with Temkin and El-Awady et al.
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adsorption isotherm models. From the results obtained, GA was concluded as a more effective
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inhibitor for Al in the acid solution than mild steel. In alkaline (0.1 M NaOH) medium, the
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effectiveness of GA towards the corrosion inhibition of Al with and without iodide ion (as KI)
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additives has also been studied by Umoren (2009) and Umoren et al. (2006) at 30 and 40 oC,
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using hydrogen evolution and thermometric techniques. The corrosion inhibition of GA of Al in
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0.1 M NaOH was enhanced in the presence of the iodide ions due to synergistic effect. In the
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absence of KI, the inhibition of Al corrosion by GA was GA-concentration and temperature
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dependent, chemisorption mechanism was proposed for GA inhibition and its adsorption on Al
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substrates followed Langmuir and Freundlich adsorption isotherms.
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Guaran, or simply, Guar gum (GG), extracted from guar bean seed endosperm is another
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class of anticorrosion gum reported in the literature. Abdallah (2004) was the first to report its
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anticorrosion behaviour for carbon steel (L-52 grade) in 1 M H2SO4 containing NaCl as the
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corrodent using Tafel polarization and weight loss techniques. His research results revealed GG
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as a mixed type inhibitor and values of inhibition efficiency (% η) increased with its
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concentration for both corrosion monitoring techniques. GG adsorption on L-52 substrate 8
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followed Langmuir adsorption isotherm and the pitting corrosion potential (Epit) was found to
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vary with chloride ion concentration in the solution of the electrolyte. The applications of
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exudate gums from plants sources are inexhaustive. Ameh’s group has reported the corrosion
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inhibition of gum exudates extracted from Ficus glumosa (GFG), Ficus Benjamina (GFB) and
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Acacia Sieberiana (GAS) for mild steel (MS), Al and Zn corrosion in 0.1 M H2SO4 and 1 M HCl
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(Ameh et al. 2012; Ameh and Eddy 2014; Eddy et al. 2014). Corrosion inhibition of GF for mild
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steel followed chemical adsorption mechanism and its adsorption was approximated with
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Langmuir adsorption model (Ameh et al. 2012). Using classical (weight loss, gasometric and
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thermometric) and surface analytical (scanning electron microscopy, SEM) techniques, authors
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claimed that the inhibiting properties of GFB could be largely attributed to a multiple adsorption
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of its chemical constituents (tannins, polysaccharides and glucoproteins characterized by Gas
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chromatography-Mass spectrometry (GC-MS) and Fourier transform infra-red spectroscopic
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(FTIR) techniques) on MS. Results followed the same trend for Al corrosion except that GFG
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adsorption on Al followed Frumkin and Dubinin-Radushkevich adsorption models (Eddy et al.
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2014). In sulphuric acid, zinc corrosion inhibition has also been studied using GAS with weight
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loss, thermometric and scanning electron microscopic techniques. GAS adsorption was
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approximated with Frumkin adsorption model, and its corrosion inhibition was found to be
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concentration and temperature dependent. Protective inhibitor layer on the surface of the metal
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substrate was revealed by SEM (Ameh and Eddy 2014). The chemical composition of gum
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exudate extracted from Daniella olliverri (GDO) has been determined using GCMS and FTIR to
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contain stearic and phthalate acids, sucrose, 2,6-dimethyl-4-nitrophenol and (E)-hexadec-9-enoic
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acid, and mild steel corrosion inhibition with GDO has been attributed to the adsorption of these
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compounds in 0.1 HCl (Eddy et al. 2012). In this study, authors investigated the adsorption and
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thermodynamic behaviour of GDO. While results from weight loss technique reveals a
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dependence of % η on the concentration of the exudate gum, its adsorption followed Langmuir
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adsorption isotherm and the inhibition of GDO was entirely by physical adsorption. Abu-Dalo et
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al. (2012) have also studied the inhibition effect of exudate gum extracted from Acacia trees
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(GAT) on MS corrosion in 0.5─2 M HCl and H2SO4. A concentration range of 0.1─0.6 mg/L
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GAT was chosen for this study investigated using weight loss, hydrogen evolution, and
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electrochemical polarization, X-ray photoelectron spectroscopy (XPS), FTIR and SEM. For both
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acid corrodents, values of % η increased with inhibitor concentration but GAT inhibited
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corrosion in HCl more than H2SO4. The magnitude of % η was found to increase with external
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magnetic field in the presence of GAT also revealed to be a mixed type inhibitor. Steel corrosion
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inhibition was attributed to the adsorption of GDO films on the surface of the metal substarte,
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and this was confirmed by results from FTIR, SEM and XPS. Investigated with classical and
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electrochemical techniques, Behpour et al. (2011) have reported the effects of exudate gum
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extracts from Ferula assa-foetida (GFF) and Dorema ammoniacum (GDA) on the corrosion
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inhibition of MS corrosion in 2 M HCl solution. From Tafel curves, the authors concluded that
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the gums from both sources exhibited mixed type behaviour, and their adsorptions followed
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Langmuir isotherm. The magnitude of % η for steel in the solution of the acid electrolyte
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decreased with temperature for both gum resins. Inhibition of MS in the presence of GFF and
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GDA was attributed to adsorption of components of the gums unto the metal substrate in the
254
corrodent; authors further performed quantum chemical calculations (by the semi-empirical
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method/Austin Model (AM1) method) illustrating the adsorption processes of some of these
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chemical components. SEM results revealed more surface pitting for MS substrate in the
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corrosion media containing GFF compared to GDA. Umoren et al. (2009a) have reported the
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corrosion inhibition of Al in HCl in the presence of exudate gum from Raphia hookeri (GRH) at
259
30–60 oC. Results from weight loss and thermometric techniques show that the performance of
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GRH improved with concentration and not with temperature. The physical adsorption
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mechanism of GRH was approximated with Temkin adsorption isotherm and Kinetic–
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Thermodynamic Model of ElAwady et al. Al corrosion inhibition in the presence of GRH was
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also attributed to the adsorption of its phytoconstituents. Biswas et al. (2015) have recently
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reported the inhibition effect of Xanthan exudate gum (Figure 1) and its graft polyacrylamide co-
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polymer on MS corrosion in a very high concentration of acid (15% HCl) using chemical,
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electrochemical and surface analytical techniques. For all the techniques used in this study,
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values of % η increased with inhibitor concentration and the gum inhibited HCl induced
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corrosion up to 92% inhibition efficiency ─ remarkably higher for this corrodent concertation
269
(15% HCl). The gum inhibition system acted as a mixed type inhibitor with molecular adsorption
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at the metal surface initiating corrosion inhibition as confirmed by SEM analysis.
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inhibition was revealed in the presence of polyacrylamide. Inhibition mechanism was elucidated
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by means of thermodynamic and kinetic parameters and Xanthan gum adsorption and in
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combination with the copolymer on the metal surface followed Langmuir isotherm model.
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Improved
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Authors also correlated the experimental results with theoretical evaluation of associated
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monomeric units using DFT in other to correlate inhibitor molecular structure with corrosion
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inhibition. The inhibition performance of exudate gum extracted from Dacroydes edulis
277
(Umoren et al. 2008b) including exudate gum extracts from other floral sources investigated in
278
acidic and alkaline media are presented in Table 1, well as their corrosion behaviors for
279
respective metal substrates as reported in the literature. Apart from the unique chemical
280
constituents of individual gums from different sources, their solubility in aqueous media allows
281
for their wide application in corrosion inhibition. In aqueous media, dried gum matters adsorb
282
water and gradually swell, then gel, dissolving without agitation since the consist of complex
283
mixtures of polysaccharides. Peter et al. (2015) have recently given a comprehensive review of
284
some green gums for corrosion inhibition in order of class/source as well as their solubility in the
285
media. Table 1 features reviewed examples of other exudate gums reported in the literature
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Figure 1. Molecular structure (repeat unit) of Xanthan gum
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Carboxymethyl and Hydroxyethyl cellulose
Cellulose gum or simply, Carboxymethyl cellulose (CMC), is available as a sodium salt.
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It has structural features of normal cellulose but with reactive carboxymethyl groups attached to
304
the hydroxyl groups of its cellulosic glucopyranyl moiety (Figure 2) (Peter et al. 2015).
305
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Figure 2. Molecular structure of Carboxymethyl cellulose [R=H or CH2COOH] and
307
Hydroxyethylcellulose [R=H or CH2CH2OH].
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Derived from molecular cellulose, CMC could be one of the most abundant water-insoluble
309
polysaccharide used in similar industrial applications as exudate gums as they are better binders,
310
thickener, stabilizers for food and pharmaceutics (Solomon et al. 2010). CMC is widely
311
synthesized via alkali-assisted cellulose/chloroacetic acid reaction. In acid-induced corrosion
312
inhibition, the protective ability of CMC on steel is alleged to be due to a possible physisorption
313
of protonated CMC via molecular attraction with the negative charged mild electrode weakly
314
adsorbed by hydrated ions of electrolyte anions. CMC protonation occurs primarily at the
315
carbonyl group, normally forming polycations. The anti-corrosive properties of CMC have been
316
widely studied for mild steel in different acid solutions. Bayol et al (2008) have studied the
317
adsorptive behavior of CMC on MS in HCl solutions. Solomon et al (2010) and Umoren et al
318
(2010) have reported the inhibition potential of CMC for sulphuric acid corrosion of MS and also
319
the effects of synergism and antagonism of halide ions with CMC on corrosion inhibition. Table
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2 presents a list of substituted cellulosic compounds deployed for metal corrosion reduction in
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various aggressive media. In the work by Solomon et al. (2010), CMC have been assessed as a
322
green corrosion inhibitor for MS in 2 M H2SO4 by means of chemical techniques (weight loss,
323
hydrogen evolution and thermometric methods) at 30–60 oC. It was found that values of % η
324
greatly increased with CMC concentration and not with temperature. This physical mode of
325
adsorption followed Dubinin–Radushkevich and Langmuir adsorption isotherms; and the
326
inhibition mechanism was corroborated by experimentally derived activation/kinetic parameters.
327
Under the same experimental condition, authors further studied the effect of halide ions (Cl─,
328
Br─, and I─) additives on the performance of CMC in the acid medium (Umoren et al. 2010). The
329
corrosion inhibition by CMC was enhanced in the presence of Iodide ions, showing synergistic
330
effect, while the opposite was the case in the presence of chloride ions (antagonistic effect). The
331
magnitude of % η increased with immersion time of MS in the solution of the electrolyte
332
containing CMC and the iodide ions, and for all the other halide ions. Adsorption of the halide
333
ions followed similar isotherm model reported by Solomon et al. (2010), and the trend in
334
thermodynamic and kinetic parameters was explained accordingly with respect to each halide
335
ions. Bayol et al (2008) have reported similar findings in 1 M HCl using chemical (weight loss
336
method) and electrochemical (potentiodynamic polarization, linear polarization resistance (LPR),
337
and EIS) techniques. Inhibition of MS corrosion was found to be concertation dependent and
338
CMC was revealed as a mixed type inhibitor. The adsorption behavior reported in this study
339
follows the same trend as those previously reported for CMC (Solomon et al. 2010; Umoren et
340
al. 2010). SEM analysis was employed in studying the adsorption of CMC on the MS surface at
341
room temperature. The corrosion inhibition of a planar cadmium disc electrode in 0.5 M HCl in
342
the presence of CMC alongside five other polymers has been reported by Khairou and El-Sayed
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(2003) using EIS and Tafel techniques. The inhibitive action of CMC affected only the
344
associated cathodic processes, indicating that it was a cathodic type inhibitor at higher
345
concentrations. CMC’s physical adsorption mode followed Temkin adsorption isotherm, and the
346
increase in values of % η with CMC concentration was attributed to molecular adsorption on the
347
cadmium disc surface. Using weight loss technique, Rajendran et al (2002) have also reported
348
the effect of CMC on the inhibition properties of 1-hydroxyethanole-1/1-diphosphonic
349
acid(HEDP)─Zn2+ binary system for MS in neutral chlorine ion (60 ppm Cl─) saturated media.
350
Values of % η for this system stood at 40% in the presence of 300 ppm HEDP and 10 ppm Zn2+
351
but increased to 80 % with the addition of 50 ppm CMC being the peak concentration. Inhibition
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of MS corrosion in this neutral medium was attributed to the adsorption of Zn(OH)2,
353
Fe2+─HEDP type and Fe2+ ─CMC complexes/films on the surface of the metal substrate. This
354
was confirmed with X ray diffraction (XRD) and FTIR. Another CMC─Zn2+ binary system in
355
neutral chlorine ion (120 ppm Cl─) saturated media has been studied for carbon steel corrosion
356
using weight loss, EIS and potentiodynamic polarization techniques (Antony et al. 2010). A % η
357
magnitude of 97 % was achieved at pH 7 in the presence of 250 ppm CMC and 100 ppm Zn2+,
358
though decreased at extremely low and high pH values. CMC─Zn2+ binary system displayed a
359
mixed type protection but dominantly anodic controlled. Like the work reported by Rajendran et
360
al. (2002), inhibition of MS corrosion in corrodent was attributed to the adsorption of a
361
Fe2+─CMC type complexes/protective films. This mechanism was confirmed by AC impedance
362
spectra and AFM studies. Values of % η magnitude as high as 95 and 98 % have also been
363
recorded in the presence of 250 ppm CMC (in combination with 25 and 50 ppm Zn2+,
364
respectively) for aluminuim and carbon steel substrates in ground water using chemical and
365
electrochemical techniques at pH 11 (Kalaivania et al. 2013; Manimaran et al. 2013). CMC in
366
the presence of Zn2+ synergistically inhibited steel corrosion, and inhibition was attributed to
367
Zn2+─CMC type complexes adsorption on metal surface characterized by SEM and AFM.
368
Corrosion inhibition was attributed to complex formation at the metal surface with polarization
369
result revealing that this process was predominantly cathodic. Rajeswari et al (2013) have
370
accessed the corrosion inhibition of Glucose, gellan gum, and hydroxypropyl cellulose for cast
371
iron in 1 M HCl by electrochemical and chemical methods. Corrosion inhibition was found to be
372
dependent of temperature and on the concentration of CMC (as well as that of other inhibitors).
373
Greater protection of cast iron was observed at increased inhibitor concentrations, lower
374
temperatures and prolonged immersion time. CMC was revealed as a mixed type inhibiting
375
system, while its adsorption followed Langmuir adsorption isotherm. Physical adsorption
376
mechanism was proposed form thermodynamic/kinetics parameters. Recently, the corrosion
377
inhibition of methyl cellulose in 0.1 M NaOH has been reported for aluminum and aluminum
378
silicon alloys investigated with electrochemical techniques (Eid et al. 2015). Results from
379
potentiodynamic polarization technique revealed that the inhibitive action of this compound
380
system predominantly affected the anodic process, indicating that the methyl cellulose was an
381
anodic type inhibitor. Authors attributed corrosion inhibition by this compound to adsorption via
382
multiple sites at the metal surface and the physical displacement of corrosive molecules across
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the metal/solution interface. Corrosion of the alloys was found to reduce with the concentration
384
of methyl cellulose but not with temperature. Cellulose’s physisorption at the metal surface
385
followed Langmuir adsorption isotherm, and kinetic/thermodynamic parameters were calculated
386
to further explain the mechanism of molecular adsorption.
ip t
383
Just like CMC, Hydroxyethylcellulose (HEC) is also derived from cellulose and used
388
primarily as a thickening, binding and gelling/stabilizing agents, and employed medically for
389
gastrointestinal fluids drug dissolution (https://en.wikipedia.org/wiki/Hydroxyethyl_cellulose).
390
The molecular structure of HEC is displayed in Figure 2. It has structural features similar to
391
CMC except for the replacement of the carboxymethyl with Hydroxyethyl groups still attached
392
to the hydroxyl groups of cellulosic glucopyranyl moiety in the same position. The success of
393
this carbohydrate polymer as a corrosion inhibitor in different media is drawn from these unique
394
functional groups (OH, COOH) on its cellulose backbone as well as its large molecular size
395
which ensures greater coverage of metal surface, deterring corrosive ions and molecules. El-
396
Haddad (2014) have reported a corrosion inhibition efficiency (% η ) in the magnitude of 97 %
397
for 5 mM HEC for 1018 grade carbon steel in 3.5 wt% NaCl solution. The anticorrosion
398
properties of this carbohydrate polymer were investigated using EIS, potentiodynamic
399
polarization and electrochemical frequency modulation (EFM). Electrochemical polarization
400
result revealed that HEC was a mixed-type inhibitor under this experimental condition, and
401
corrosion inhibition was induced by molecular adsorption on the steel surface confirmed by
402
SEM/ energy dispersive X-ray (EDX) analysis. Adsorption of HEC followed Langmuir
403
adsorption isotherm. Adsorption mechanism was supported by DMol3 quantum chemical
404
calculations as well as the computation of thermodynamic parameter and activation parameters.
405
Arukalam et al. (2015) have also reported similar study in an aerated 0.5 M H2SO4 solution using
406
both gravimetric and electrochemical techniques for mild steel corrosion. Corrosion inhibition
407
was found to increase with HEC concentration and with temperature. Potentiodynamic
408
polarization result revealed that HEC was a mixed type inhibitor while its adsorption on the steel
409
surface gradually decreased double layer capacitance (Cdl). Quantum chemical calculations with
410
density functional theory (DFT) were used to correlate the corrosion inhibition with HEC
411
molecular structure; inhibition was attributed to its adsorption behavior on the steel surface from
412
computed activation/kinetic parameters. HEC adsorption followed the Freundlich isotherm
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model. Corrosion inhibition was enhanced in the presence of KI in the solution of the acid
414
electrolyte. A corrosion inhibition of magnitude 69.62% and 58.15% in 1 and 1.5 M HCl,
415
respectively, has been reported by Arukalam (2012) for HEC using investigated by weight loss
416
technique. He found that HEC inhibited steel corrosion by increasing its concentration and
417
attributed inhibition to HEC molecular adsorption/elastic film formation on the steel substrate.
418
With the ban of mercury as corrosion inhibitor for zinc batteries due to its inherent toxicity and
419
environmental impact, researcher worldwide have focus more attention of organic compounds as
420
alternative (Qu 2006). Deyab (2015) has investigated the anticorrosion ability of HEC as
421
inhibitor for zinc-carbon battery using electrochemical techniques. HEC was found to inhibit
422
corrosion up to 92% for 300 ppm HEC at 30 oC. Tafel polarization revealed that HEC was a
423
mixed-type inhibitor, and its ability to inhibit Zn corrosion was attributed to its adsorption on the
424
Zn surface. Langmuir isotherm and thermodynamic parameters were employed in explaining
425
HEC adsorption (both physisorption and chemisorption), as well as FTIR and SEM for
426
characterization of the adsorbed carbohydrate biopolymeric film.
427
Starch
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Starch is a very large carbohydrate molecule with glycosidic bonds chemically
429
connecting its numerous glucose units. Normally, starch is consists of varying percentages by
430
weight of amylose (linear and helical) and amylopectin (branched) molecules depending on the
431
source from which it is derived (Brown and Poon 2005). Figure 3 displays the molecular
432
structures of starch. Starch biochemically provides the needed body energy to both higher
433
animals especially as it is being indirectly consumed from green plant sources. For these plants
434
to biosynthesize starch, series chemistry is involved: initially, adenosine triphosphate is
435
employed to convert glucose-phosphate to adenosine diphosphate-glucose via enzymatic
436
catalyzed oxidation using adenylyltransferase (Smith 2001). Virtually every human diet taken
437
daily contains starch in relatively enormous abundance (in yams, cassava, cereals, potatoes, oats,
438
peas, nuts, etc.). Starch is basically used as common food additive but also processed for use to
439
simple sugars, thickeners and glues for use in food and other industries. This white and tasteless
440
polysaccharide is sparingly soluble in warm water but completely undissolved in cold water and
441
alcoholic solvents.
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(a)
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Figure 3. Chemical structures of the amylose (a) and amylopectin (b) molecules of starch.
M
444
(b)
The use of molecular starch as corrosion inhibitor lacks wide application due to its
446
reduced solubility and surface adhesion strength. Some reports involving its application in acid
447
and neutral media for metal inhibition have been reported based on either physical or chemical
448
modification in other to improve its anticorrosion ability. The corrosion inhibiting ability of
449
starch can be linked to its unique molecular structures (Figure 3); bearing electron-rich hydroxyl
450
groups capable of coordinate bonding by filling the empty or partially occupied orbitals of iron
451
in ferrous substrates, hence corrosion inhibition. Brindha et al. (2015) have recently reported the
452
use of starch in combination with 2,6-diphenyl-3-methylpiperidin-4-one (DPMP) for mild steel
453
in 1 N HCl using chemical and electrochemical techniques. Steel corrosion rate was found to
454
reduce with the concentrations of these compounds, with both compounds synergistically
455
inhibited steel corrosion by combine molecular adsorption at the metal surface. The corrosion
456
inhibition by starch was greatly enhanced by the addition of 0.2mM DPMP independent of the
457
study temperature and the immersion time. Authors also attributed corrosion inhibition to the
458
formation of protective layer confirmed with Fourier transform Infra-red spectroscopy.
459
Experimental results were further collaborated with theoretical evaluation of the relationship of
460
molecular structure and corrosion inhibition at the B3LYP/631G(d) level. Results from weight
461
loss techniques were also collaborated with thermodynamic and adsorption isotherm models. In
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another work, starch in combination with sodium dodecyl sulfate and cetyltrimethyl ammonium
463
bromide have been studied using weight loss and potentiodynamic polarization techniques for
464
mild steel in 0.1 M H2SO4 (Mobin et al. 2011). Results from potentiodynamic polarization
465
revealed that these starch─surfactant conjugates were a mixed type system (though
466
predominantly anodic) and recorded 66.21% inhibition efficiency at 30 oC with only 200 ppm
467
starch. Just as reported by Brindha et al. (2015), author linked corrosion inhibition of both
468
systems to synergistic or combine molecular adsorption at the metal surface. Adsorption of these
469
conjugates at steel surface followed Langmuir adsorption isotherm at the range of temperature
470
and concentration under study. Physical adsorption phenomenon was proposed and results were
471
also collaborated with thermodynamic parameters to further explain the inhibition mechanism.
472
Bello et al. (2010) have studied the effect of physically (activated starch) and chemically
473
(carboxymethylated) modified starch cassava starch on the corrosion of XC 35 carbon steel in
474
alkaline 200 mg/l NaCl medium using electrochemical impedance spectroscopy. Inhibitor
475
molecular adsorption due to the presence of starch at the surface of steel was concluded as the
476
principal cause of corrosion inhibition; this was confirmed with atomic force microscopy in the
477
presence and absence of starch. Corrosion inhibition increased with the concentration of starch in
478
both cases, with carboxymethylated starch being the less performed inhibitor due to molecular
479
substitution of its active hydroxyl groups. To further explain reason for this unique behaviour by
480
carboxymethylated starch, the monomeric units were theoretically mapped (electrostatic
481
potential mapping) to observe possible ionic interactions at the molecular level. Malaysian
482
cassava (tapioca) starch has been employed in reducing the corrosion of AA6061 alloy in
483
seawater (sourced from Terengganu port, Malaysia) using chemical and electrochemical
484
techniques (Rosliza and Nik 2010). The presence of starch in the neutral corrodent was observed
485
to greatly reduce metal corrosion rate with huge effects on double layer capacitance and
486
corrosion current densities. Potentiodynamic polarization results revealed starch inhibition
487
process influenced both cathodic and anodic reactions. Corrosion reduction was inhibition
488
concentration─dependent. Corrosion inhibition was attributed to physical coverage as well as
489
molecular adsorption of starch at the metal surface; further confirmed with SEM analysis.
490
Theoretical approach to corrosion inhibition was also employed by authors in correlating
491
inhibiting mechanism with molecular structure. Adsorption of starch followed Langmuir
492
adsorption isotherm model. The effect of chemical grafting of acryl amide to cassava starch for
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corrosion inhibition of cold rolled steel in 1 M H2SO4 has been investigated using chemical and
494
electrochemical techniques (Li and Deng 2015). The improved protection from this grafted
495
conjugate was due to a synergy between both compounds by combine molecular adsorption at
496
the metal surface (with the adsorption further confirmed with SEM). From the Tafel behaviour,
497
this grafted starch─acryl amide conjugate was observed to be a mixed type inhibitor though
498
predominantly anodic and cathodic at lower and higher temperatures, respectively. Langmuir
499
adsorption isotherm was employed in fitting the adsorption of the inhibitor adsorbed at the metal
500
surface. The use of cerium (IV) ammonium nitrate modified potato-starch has been deployed as a
501
primer coatings (and polyurethane top-coat) of 6061─T6 aluminium with remarkable
502
anticorrosion properties in 0.5 N NaCl electrolyte at 25oC. Corrosion tests were conducted using
503
salt-spray tests, EIS and surface analytical techniques (FTIR and XPS). An improved protective
504
property of this composite was attributed to the formation of cerium-bridged carboxylate
505
complexes by carboxylate functional group with Ce4 ions at the metal/coating interface. The
506
coating was found to loss of adhesion on polyurethane compared to aluminium substrates
507
(Sugama, 1997).
508
Pectin
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Pectin is a complex set of heteropolysaccharide with molecular structure not restricted to
510
Figure 4. It is naturally abundant in cell walls of non-woody terrestrial plants and commercially
511
available as white or brownish powders/granules (depending of the methods of synthesis and
512
purification) (Keppler et al. 2006). In nature, the structure and composition of floral pectin
513
depend on the plant and even the plant parts; and during fruit ripening, pectin is reduced to
514
pectinesterase by pectinase (Equation 1). Pectic polysaccharides are abundant with galacturonic
515
acid.
516 517
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509
Pectin
pectinase
Pectinesterase
(1)
19
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ip t
518
Figure 4. Molecular structure of pectic acid
520
Pectic is commonly extracted from citrus and apples, and used as gelling and thickening agents
521
in food industries and as stabilizers in some confectionaries, as well as in drinks (Sakai et al.
522
1993). Since pectin normally increases the amount and viscosity of human stool, it is medically
523
used against some chronic cases of constipation and diarrhea. Like other polysaccharides enlisted
524
in this review for inhibition, pectin’s ability to reduce metal corrosion is drawn from its
525
chemistry. Pectin possess carboxylic (―COOH) and carboxymethyl (―COOCH3) functional
526
groups on its carbohydrate backbone making it a possible candidate compound for corrosion and
527
scaling reduction in different media (Chauhan et al. 2012). Pectin is a biodegradable, benign and
528
green corrosion inhibitor. We have recently reported the anticorrosion ability of pectin
529
(commercial pectin from apple) in our laboratory against X60 pipeline steel in HCl medium
530
using chemical and electrochemical techniques (Umoren et al. 2015b). The corrosion inhibition
531
efficiency (% η ) was found to be temperature and pectin concentration dependent; higher
532
magnitudes of % η were obtained at increased concentration of pectin (79% being the highest
533
recorded % η for 1000 ppm pectin) and temperature. Potentiodynamic polarization results
534
revealed pectin inhibition influenced both cathodic and anodic reactions, but dominantly
535
cathodic. Inhibition of X60 pipeline steel corrosion was attributed to adsorption of protective
536
pectin film on the metal surface, and this was further confirmed by SEM and water contact angle
537
measurements. Pectin adsorption followed Langmuir adsorption isotherm, and quantum chemical
538
calculations by DFT was employed to explain pectin’s adsorption-inhibition activity. Fares et al
539
(2012a) have studied the application of pectin (from citrus peel) for Al metal reduction in acidic
540
(0.5-2 M HCl) media. The magnitude of % η greater than 91% was attained for 8.0 g/L pectin at
541
10 oC and was observed to slowly decrease with temperature. Values of % η increased with
542
pectin concentration, and this was consequently reflected in corresponding values of activation
543
energy, enthalpy and entropy. Corrosion inhibition by pectin was attributed to its adsorption on
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the metal surface and this was confirmed by SEM analysis. Its adsorption in this acidic media
545
followed Langmuir isotherm. Fiori-Bimbi et al. (2015) have reported a multi-step acid extraction
546
of pectin from fresh lemon peel. The pectin extract was tested for anticorrosion ability for mild
547
steel in 1 M HCl using chemical and electrochemical methods. Mild steel corrosion was found to
548
reduce with the addition of pectin, and this continued as the temperature increased. Tafel results
549
revealed that pectin in this study is mixed-type inhibitor, and the reason for pectin inhibition was
550
due to geometric blocking effect caused by chemisorbed pectin─Fe2+ type complexes/species at
551
the metal/solution interface was confirmed by UV-spectroscopic analysis. Thermodynamics and
552
kinetics of adsorption were considered directly from the electrochemical results and the trend in
553
values further added insights into the mode of adsorption. The most recent pectin application for
554
corrosion protection is the work by Grassino et al (2016). Authors extracted pectin for the first
555
time using tomato (Lycopersicum esculentum) waste. Characterization of pectin after extraction
556
from this source proceeded with FTIR and nuclear magnetic resonance spectroscopy (NMRS)
557
analyses as well as colour and rheological determination. Results were compared to a
558
commercially available pectin standard. The extracted pectin was methoxy pectin type based on
559
the degree of esterification result (about 82%). The pectin extract was employed in studying tin
560
corrosion inhibition, and values of % η up to 73% was recorded at very low concentrations (4
561
g/L) using EIS and potentiodynamic polarization technique in 2% NaCl, 1% acetic acid and
562
0.5% citric acid solution. Tafel results revealed that pectin in this study is mixed-type inhibitor.
563
Pectin extract from Opuntia cladodes has also been employed in reducing mild steel corrosion in
564
1 M HCl using weight loss, potentiodynamic polarization and electrochemical impedance
565
spectroscopy techniques (Saidia et al. 2015). Corrosion inhibition increased with the pectin
566
concentration as revealed in variation in values of charge-transfer resistance and the reduction
567
double-layer capacitance. Pectin from this source acted as a mixed inhibitor with the highest % η
568
(96%) attained at 35 oC in the presence of 1g/l pectin. Pectin adsorption on the metallic substrate
569
followed Langmuir adsorption isotherm. Corrosion researches involving pectin inhibition is not
570
limited to acid-induced media, Prabakaran et al. (2015) have reported the synergistic pectin
571
inhibition with propyl phosphonic acid (PA) and Zn2+ ions in neutral medium for carbon steel
572
using chemical and electrochemical techniques. The presence of pectin in this study enhanced
573
the inhibition ability of the secondary components (PA and Zn2+ additives). Result from weight
574
loss technique revealed the optimum concentration of pectin, also showing that the presence of
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PA and Zn2+ synergistic improved corrosion protection by pectin. Potentiodynamic polarization
576
results revealed pectin inhibition influenced both cathodic and anodic reactions, and its
577
adsorption was marked with decrease in values of corrosion current density. Spectroscopic
578
(FTIR) and surface analytical (SEM, AFM, and XPS) techniques were employed to ascertain the
579
formation of pectin-type complexes/film on carbon steel. The corrosion inhibition of
580
pectin/ascorbic acid for tin in a neutral NaCl solution has been investigated (Nada et al. 1996).
581
Greater corrosion inhibitive effect for the binary system was observed at 200 ppm ascorbic acid
582
in combination with pectin at room temperature. The inhibitory effect for was due to the
583
formation of protective complex at the tin/solution interface. Results from potentiodynamic
584
polarization technique showed that the inhibitive action of the system affected only the cathodic
585
process, indicating that the pectin/ascorbic acid binary system was cathodic type inhibitor. Like
586
other carbohydrate biopolymers, pectin can be modified for many applications by carefully
587
altering its functional chemistry. With some anticorrosive polymers, structural modifications
588
improves the overall material performances by coupling single or multiple adsorption sites
589
capable of metal surface bonding and physically displacement of corrosive molecules like water
590
across the metal/solution interface. For mild steel inhibition in 3.5 wt% NaCl solution, pectin has
591
been grafted to polyacrylamide and polyacrylic acid, and the final materials protected steel more
592
than 85% (Geethanjali et al. 2014). The graft polymerization procedure slightly differs from
593
those reported by Mishra et al. (2007), except for modification in the final pH sensitive hydrogel
594
products with acrylic and acrylamide acids, and pectin still used as precursors. Polymer synthesis
595
and modification were followed by corrosion testing using EIS and Tafel polarization, and then
596
surface analytical evaluations (with FTIR and SEM) of the protective film formed on the steel
597
surface. Pectin modification products have also been reported as being used as antiscalants for
598
water treatment (Chauhan et al. 2012). This procedure was only designed to lower the molecular
599
weight of pectin by acid hydrolysis before grafting to acrylamide, thereby making copolymer-
600
graft with an antiscalant potential for carbonates, sulfates and phosphates. The outcome of the
601
scaling remediation experiment with the final hydrolyzed pectin-based grafted material was
602
outstanding against the carbonates precipitation, but this reaction was temperature and pH
603
independent. SEM and XRD techniques were employed in studying the precipitates’ crystal
604
morphology.
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605
Pectate Pectic acid (or polygalacturonic acid), like pectin is also present in plants, but dominantly
607
in ripened fruits (Sakai et al. 2003). Its derivatives, particularly pectates, obtained from structural
608
modification of pectin and pectic acid, could be better emulsifying and foaming agents for food
609
and medical industries. Pectates are salts or esters of pectic acid. Hromádková et al. (2008) have
610
reported the synthesis of some pectates (pectate alkyl amides) from citrus pectin via
611
alkylamidation of esterified pectin from this source, followed by alkaline hydrolysis. These
612
pectate amides were also tested for their foam stabilizing abilities. Schweiger (1962) has reported
613
some routes for the substitution at hydroxyl groups of pectic substances, like nitropectin without
614
the rigorous conventional catalyzed reaction involving acetic anhydride or acetyl chloride in
615
pyridine. Just like other pectic substances, pectates have also been involved in corrosion
616
inhibition in some media in a view to utilizing their free alcoholic groups for metal surface
617
bonding. Zaafarany (2012) has reported corrosion inhibition of pectates (with alginates) anionic
618
polyelectrolytes for Al in 4 M NaOH using chemical methods. The presence of pectate in
619
solution of the electrolyte markedly reduced the corrosion rate of Al, and an inhibition efficiency
620
(% η ) magnitude up to 88% was recorded for 1.6% pectate in the solution of the alkaline
621
electrolyte using weight loss technique. Corrosion inhibition was found to be inhibitor
622
concentration and temperature dependent but the study was without an explanation of the
623
possible
624
kinetics/thermodynamic modelling. Recently, Zaafarany’s group has revisited this work using
625
sodium alginate and sodium pectate for pure Al substarte in the same corrodent (Hassan et al.
626
2013; Hassan and Zaafarany, 2013). The corresponding magnitudes of corrosion rate derived
627
from the techniques used in this study were computed and showed negligible difference.
628
Corrosion inhibition by Na pectate was ascribed to physical molecular adsorption with the
629
mechanism elucidated by means of thermodynamic and kinetic parameters. Pectate adsorption on
630
the metal surface followed Langmuir and Freundlich isotherm models.
Ac ce pt e
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corrosion
inhibition
mechanism,
electrochemically
or
by
means
of
631
632
Chitosan and substituted/modified chitosans
23
Page 23 of 74
Chitosan is a hydrophilic carbohydrate polymer naturally occurring in chitin-rich
634
exoskeletons of marine crustaceans and in shrimps and crabs, and can also be extracted by N-
635
deacetylation of fungal cell-wall chitin via alkaline treatment as well as chitins from simple
636
arthropods. It is being widely used against skin infections due to its antibacterial and fungal
637
properties, and as drug-carriers in modern therapeutics (https://en.wikipedia.org/wiki/Chitosan).
638
The antibacterial activities of chitosan as well as its combination with other polymers have been
639
studied for a range of Gram-positive and negative bacterial infections (Rabea et al. 2003; Gabriel
640
et al. 2015; Aziz et al. 2012; Chung et al. 2011; Feng et al. 2014a). Chitosan is also employed in
641
the textile, paper and food industries for various applications. Chitosan’s anticorrosion ability
642
could be drawn from its molecular structure (Figure 5); it bears electron-rich hydroxyl and amino
643
groups capable of metal surface bonding subsequent corrosion inhibition via coordinate bonding
644
as these electrons are donated to the empty or partially occupied Fe orbitals. The grafting of
645
these polar groups unto surfaces increases total surface energy components thereby further aiding
646
corrosion inhibition (Umoren et al. 2013). Chitosan is a polysaccharide bearing β-(1-4)-linked
647
and N-acetyl- D-glucosamine units in its monomeric moiety.
648 649
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633
Figure 5. Molecular structure of chitosan.
650
Earlier reports on the corrosion inhibition of chitosan are those previously reported in acid-
651
induced conditions for copper and mild steel (El-Haddad 2013; Cheng et al. 2007; Fekry and
652
Mohamed 2010; Mohamed and Fekry 2011). Using chemical and electrochemical techniques,
653
the corrosion inhibition of copper has been investigated in 0.5 M HCl using chitosan by El-
654
Haddad (2013). Chitosan was revealed as being a mixed-type inhibitor in the acidic condition
655
from its unique Tafel behavior. Electrochemical impedance results revealed steady decrease in
656
capacitance and increase in resistance with increasing concentration of chitosan. Inhibition of 24
Page 24 of 74
copper corrosion in HCl was attributed to molecular absorption of this biopolymer unto the metal
658
surface, and this was approximated with Langmuir isotherm and also evaluated with SEM and
659
FTIR. Quantum chemical calculations were also used to correlate the corrosion inhibition with
660
the molecular structure of chitosan. Cheng et al. (2007) have reported the effectiveness of
661
Carboxymethylchitosan-Cu2+ mixture for inhibition of mild steel in 1 M HCl gravimetric
662
(between 298 and 353K) and electrochemical techniques. Steel corrosion inhibition by this
663
mixture was attributed to synergistic effect from both polymeric and ionic components; as
664
individual components inhibited less than a combination of both. The magnitude of % η greater
665
than 90% was obtained for Carboxymethylchitosan-Cu2+ mixture, with 86 and 14% obtained for
666
20 mg/L Carboxymethyl chitosan and 0.01 ppm Cu2+, respectively. Corrosion inhibition of mild
667
steel in the presence of this mixture was also attributed molecular adsorption of chitosan, and its
668
inhibition mechanism was further investigated with conductometry. Physical adsorption
669
mechanism was also proposed from thermodynamic/kinetics parameters. Fekry and Mohamed
670
(2010) have reported the anticorrosion ability of Acetyl thiourea chitosan conjugate polymer,
671
synthesized by first preparing acetyl thiocyanate before adding to dissolve chitosan solution (in
672
dimethyl formamide/ acetic acid mixture at 100 ◦C). Using polarization and EIS techniques,
673
corrosion studies with this chitosan–derived conjugate polymer was conducted for mild steel in
674
aerated 0.5 M H2SO4. Corrosion rate of mild steel greatly reduced in the presence of this
675
conjugate polymer but increased with temperature. Corrosion resistance was found to increase
676
with immersion time, revealing that mild steel corrosion inhibition by chitosan was due to
677
molecular adsorption on prolonged immersion. A % η value of 94.5% was obtained for 0.76 mM
678
concentration of this conjugated biopolymer in the solution of the acidic electrolyte. SEM was
679
employed in studying the surface morphology of the steel substrate, in terms of the prevalence of
680
deep localized pits and the formation of protective film, in the absence and presence of inhibitor,
681
respectively. Fekry and Mohamed (2011) have also reported the corrosion inhibition of chitosan-
682
crotonaldehyde schiff’s base for AZ91E alloy inhibition in artificial sea water using EIS and
683
Tafel techniques. Corrosion resistance in the saline solution was found to increase with the
684
immersion time and concentration of the schiff’s base but decreased with temperature. AZ91E
685
alloy corrosion inhibition was attributed to the adsorption of inhibitor films on the surface of the
686
metal substrate, and this was confirmed by results from SEM. Chitosan-crotonaldehyde schiff’s
687
base was also used to adsorb Congo red dye and Maxilon Blue dyes, and its antimicrobial
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activities were investigated against Escherichia coli, Staphylococcus aureus, Aspergillus niger
689
and Candida albicans. Umoren et al. (2013) have investigated the role of a synthetically-derived
690
chitosan in 0.1 M HCl for mild steel corrosion using chemical, electrochemical and surface
691
analytical techniques. Corrosion inhibition was found to increase with the concentration of
692
chitosan, with values of % η greater than 90 % recorded at low concentrations of the
693
biopolymer. Its Tafel behavior revealed a mixed-type inhibition for the range of concentrations
694
studied. Authors attributed steel corrosion inhibition to the formation of film at the surface of the
695
substrate, and this was confirmed by SEM and UV spectroscopy. Chitosan’s chemisorption at the
696
metal surface followed Langmuir adsorption isotherm, and kinetic/thermodynamic parameters
697
were calculated to further explain the mechanism of molecular adsorption. In another study, the
698
anticorrosion properties of O-fumaryl-chitosan on low carbon steel has been investigated in
699
aqueous HCl using weight loss and electrochemical techniques (Sangeetha et al. 2015b).
700
Potentiodynamic polarization results revealed this modified chitosan biopolymer influenced both
701
cathodic and anodic reactions, and recorded a 93% inhibition efficiency at 500 ppm. For all the
702
techniques employed in this study, the corrosion rate of the metal substrate reduced with the
703
concentration of the chitosan inhibitor. The trend in corrosion resistance and double layer
704
capacitance with the concentration of the inhibitor was evaluated from the impedance results.
705
Steel inhibition in the presence of this compound was attributed to the film formation and
706
adhesion of complexes at the surface of the metal via molecular adsorption. This was confirmed
707
with surface analytical techniques (SEM, AFM and FTIR), with the mechanism of inhibition
708
proposed from electrochemical findings including zero charge potential evaluation. The
709
corrosion mechanism was also evaluated by means of adsorption isotherm plots and the
710
assessment of the thermodynamics of the inhibition process.
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711
More applications of modified chitosans and their composites also abound in the
712
literature. Heptanoate anions have been encapsulated into chitosan-modified beidellite coating
713
for corrosion protection of galvanized steel (Aghzzaf et al. 2012). The coating system was
714
designed to initiate continuous releasing of inhibiting heptanoate molecules to the surface
715
thereby healing any inherent micro-cracks. Diffuse reflectance infrared Fourier transform
716
spectroscopy (DRIFTS), TG coupled MS and XRD techniques were employed in studying the
717
coating prior to corrosion test with EIS in 3 wt% NaCl for the coated galvanized steel. The steel
26
Page 26 of 74
corrosion protection of this modified chitosan hybrid inhibitor was compared to a commercially
719
available anticorrosive pigment (Triphosphate aluminium). The improved corrosion inhibition
720
for this class of coating was attributed to leaching of hepatanoate ions at the metal/coating
721
interface. Li et al. (2015) have synthesized and investigated the anticorrosion properties of some
722
methyl acrylate grafted and triethylene tetramine/ethylene diamine chitosan copolymers for
723
Q235-grade carbon steel in 5% HCl at 25oC for 72 h using chemical and electrochemical
724
techniques. The improved corrosion inhibition of these hybrid chitosan systems was attributed to
725
high chemical grafting; ethylene diamine chitosan copolymers gave a 90% corrosion inhibition
726
efficiency (% η ) compared to the triethylene tetramine grafted system (% η = 85%). Steel
727
corrosion inhibition was also attributed to the adsorption of grafted polymeric molecules to the
728
surface of the metallic substarte; this was confirmed by metallographic microscopy and SEM.
729
Thiocarbohydrazide graft chitosan has been synthesized and its anticorrosion properties
730
investigated against 304 steel and Cu sheet corrosion in stagnant 2% acetic acid electrolyte
731
containing the modified chitosan inhibitor (Li et al. 2014a). Electrochemical polarization result
732
reveals the compound as a mixed type inhibitor with a magnitude of % η greater than 85% at
733
concentration of 30 mg/L. Thiocarbohydrazide graft chitosan was also used by authors to extract
734
some heavy metal (As, Ni, Cu, Cd, Pb) ions up to an adsorption efficiency of 60–99% at pH 9.
735
Using the same metal substrates and in the same test electrolyte, authors have also investigated
736
the corrosion inhibiting abilities of some thiosemicarbazide and thiocarbohydrazide modified
737
chitosan derivatives (Li et al. 2014b). They were reported to be mixed-typed systems as well, and
738
with a magnitude of % η greater than 90% at concentration of 60 mg/L. An adsorption efficiency
739
of 60–99% for As, Ni, Cu, Cd, Pb ions at pH 9 was also reported for both compounds were
740
employed as aqueous phase absorbents. Recently, Liu et al. (2015) have investigated the efficacy
741
of β-cyclodextrin modified natural chitosan for carbon steel corrosion in 0.5 M HCl using
742
chemical and electrochemical techniques. Corrosion inhibition was found to increase with
743
concentration of inhibitor at 30 oC. Potentiodynamic polarization results revealed this modified
744
carbohydrate biopolymer influenced both cathodic and anodic reactions with magnitude of % η
745
greater than 95%. Corrosion inhibition by this compound was attributed to its molecular
746
adsorption unto the metal surface, and this was approximated with Langmuir adsorption isotherm
747
also involving both physisorption and chemisorption protection mechanism. Metal surface
748
adsorption was confirmed with SEM/EDS. Chitosan films has also been involved in synthesis of
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Page 27 of 74
protective coating for corrosion inhibition. In a recent report, chitosan has been deposited on
750
mild steel substrates by solution electrophoresis via the application of a 15 V potential for 15
751
mins in a binary solution of chitosan/acetic acid with glutaraldehyde employed as the cross linker
752
(Ahmed et al. 2012). FTIR and SEM techniques were employed for surface characterization of
753
the film after electrodeposition before corrosion test using EIS and polarization methods with the
754
coated substrates immersed in 0.5 M H2SO4. Corrosion resistance of the chitosan coating was
755
found to decrease with immersion time in the solution of the electrolyte, and a % η value of 98%
756
was obtained at the experimental condition under study compared to bare steel. A self-healing
757
chitosan-based hybrid coating doped with cerium (Cs) ions has also been synthesized for
758
aluminium alloy AA 2024 (Zheludkevich et al. 2011). Cs ions served as an encapsulated
759
corrosion inhibitor in the bulk of the coating thereby enhancing the material’s mechanical and
760
protective strength. Optical microscopy, SVET, SEM/EDS and FTIR techniques were used in
761
analyzing the undoped chitosan, and Ce-doped chitosan coating, before and after immersion in
762
the solution of the electrolyte after different exposure period in 0.05 M NaCl solution. EIS
763
results reveal prolonged corrosion protection for the hybrid chitosan coating in the presence of
764
Cs ions doped in the pre-layer of the coating. Its self-healing ability at specific micro-confined
765
defects were assessed via localized electrochemical study. The protective properties of
766
Chitosan/Zn composite coating electrodeposited on mild steel from zinc sulphate/sodium
767
chloride binary solution has been reported by Vathsala et al. (2010). The effect of variation of
768
principal electrolyte components as well as the concentration of Zn ions was investigated vis-à-
769
vis superior protection. Corrosion test was conducted in 3.5 wt% NaCl for this class of coating
770
using chemical and electrochemical techniques, as well as salt spray test. The enhance corrosion
771
protection of this coating was attributed to synergistic inhibitive action of Zn ions in the coating,
772
this was evident in the increased corrosion resistance in the presence of the Zn ions using EIS.
773
SEM was also employed in studying the surface morphologies and crystallinity in the presence
774
of chitosan. El-Sawy et al. (2001) have reported the synthesis of Poly(DEAEMA)-chitosan-graft-
775
copolymer, poly(COOH)- chitosan-graft-copolymer, poly(V-OH)-chitosan-graftcopolymer, and
776
carboxymethyl-chitosan for the corrosion protection of steel panels uniformly coated at room
777
temperature. Corrosion protection was reported to increase in more highly grafted coatings, and
778
their protection mechanism was attributed to their bulk properties as well as the strength
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Page 28 of 74
779
coating/metal bonding (adhesion). These compounds were also used in adsorbing metals ions
780
and dyestuffs from aqueous solutions. The modification of chitosan molecules also involves the syntheses of its nanoparticle
782
composites for metal protection, and a few of them has been reported in the literature. Atta et al.
783
(2015) have synthesized hydrophobic chitosan nanogels with unsaturated fatty acids before
784
grafting them with polyoxyethylene aldehyde monomethyl ether to prepare amphiphilic chitosan
785
surfactant (ACS). Nanoscaled particles of this surfactant were later made from emulsification
786
and crosslinking reactions using methylene chloride with sodium tripolyphosphate, respectively.
787
Hydrophobicity, functional group and particle size analyses were carried out using appropriate
788
analytical techniques. Characterization of the grafted nanoparticles was followed by
789
electrochemical corrosion tests using EIS and Tafel methods. Values of Cdl decreased while the
790
corrosion resistance of carbon steel rode was found increase with the concentration of the
791
nanogel in the HCl (1 M) electrolyte, with values of % η greater than 85% recorded at a
792
nanoscale concentration of 250 mg/L. Corrosion inhibition of this nanogel was attributed to the
793
formation of active protective film carrying chitosan molecules at the metal/solution interface;
794
this was further confirmed by SEM analysis. John et al. (2015) have also reported the synthesis
795
of nanostructured chitosan/ZnO nanoparticles by sol-gel method, and its anticorrosion ability
796
evaluated electrochemically by Tafel and EIS techniques for mild steel in 0.1 N HCl. Improved
797
metal surface protection was revealed for compacted films in the presence of ZnO, and this
798
further enhanced increased values of inhibition efficiency (% η >70% and < 40% was obtained in
799
the presence and absence of ZnO, respectively). Formation of nanofilms on steel was concluded
800
as the principal cause of corrosion inhibition of steel, and this was characterized with UV–vis,
801
FTIR, XRD and SEM/EDX. Luckachan and Mittal (2015) have recently reported the protective
802
of layer-by-layer chitosan/poly vinyl butyral coating on steel investigated using electrochemical,
803
spectroscopic and SEM. This corrosion resistant property of this hybrid coating was evaluated
804
after 2 h immersion in 0.3 M NaCl, with the formation of passive oxide layer (Fe3O4 and γ -
805
Fe2O3 oxide) on the metal substrate confirmed by SEM and Raman spectroscopy. Barrier
806
protection by this coating was found to improve due to the chitosan middle layer sandwiched
807
between poly vinyl butyral bilayers on the metal substrate, as well as the incorporating
808
glutaraldehyde within the chitosan layer. This was not observed with graphene and vermiculite
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Page 29 of 74
incorporated with the same chitosan matrix in the same condition. Other anticorrosion
810
applications involving pectic acid/pectates and modified chitosans and their composites reported
811
in the literature are presented in Table 3.
812
Carrageenan
813
Carrageenan is a group of gel-like and mostly linear polysaccharides bearing sulfated b-D-
814
galactose and 3,6-anhydro-a-D-galactose backbone and commonly found in seaweeds (family:
815
Rhodophyceae). Figure 6 displays the molecular structure (iota), though other structures (e.g.
816
Mu, Kappa, Nu, Lambda forms) do exist in nature. Carrageenan can also be classified according
817
to the degrees of linear chain sulfation as well as the degree of the substitution occurring at the
818
free hydroxyl groups on the linear polysaccharide chain. Their molecular symmetry is flexible,
819
forming unstable helical conformations, thereby making most carrageenans exist as gels at room
820
temperature. This unique physical structures aids in their application as food thickeners and
821
stabilizers (van de Velde et al. 2005). Nanaki et al. (2015) have reported the synthesis of
822
modified carrageenans at different concentrations for aqueous state Metoprolol ((1-
823
(isopropylamino)-3-[4-(2-methoxyethyl)phenoxy]propan-2-ol)) removal at room temperature.
824
The kinetics of carrageenan oxidation (iota and lambda forms) by permanganate in perchlorate
825
solutions have also been reported by Hassan et al. (2011). In the same acidic solution, this group
826
has also investigated the effect of hydrogen ion concentrations on chromic acid oxidation rate of
827
k-carrageenan (Zaafarany et al. 2009). Carrageenans are green and biodegradable carbohydrate
828
polymers with the potentials for corrosion protection just like other carbohydrate polymers
829
discussed in this series. They are benign and due to their unique chemical structures and
830
functional groups, they possess the ability of complexing ions of metals at surfaces, thereby
831
inhibiting aqueous corrosion. The sulphonic acid groups on these biopolymers are endowed with
832
π-orbital character of donating electron to the empty 3d orbital of the Fe substrates. The
833
investigation of the corrosion inhibition potential of i-carrageenan for aluminium sheets in
834
presence of a mediator has been reported using weight loss technique after 2 h immersion in
835
different concentrations of HCl (1.0–2.0 M) (Fares et al 2012b). Al corrosion inhibition by i-
836
carrageenan was found to improved greatly in the presence of pefloxacin mesylate (inhibition
837
mediator); magnitude of % η increasing from 66.7% to 91.8%. This metal inhibition
838
enhancement was attributed to the synergistic adsorption of i-carrageenan/ pefloxacin mediator
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Page 30 of 74
compact film on the surface of the metal (Al). This was confirmed by SEM analysis, while the
840
corrosion inhibition mechanism by molecular adsorption was further explained with kinetics and
841
thermodynamics evaluation in the presence of the inhibitor and mediator. Inhibitor molecular
842
adsorption followed Langmuir adsorption isotherm model. Zaafarany (2006) has also studied the
843
corrosion inhibition of low carbon steel in 1 M HCl using weight loss and galvanostatic
844
polarization techniques with i, k, µ─ carrageenan. Corrosion inhibition was found to decrease
845
temperature but increased with the concentration of these polysaccharide biopolymers. Corrosion
846
inhibition was attributed to the blocking the steel surface by carrageenans’ molecular adsorption.
847
The adsorption of the inhibitors on the metal substrate followed Langmuir adsorption isotherm.
848
These compounds were revealed as being anodic-type inhibitors for steel in the acidic medium
849
studied, and kinetics and activation thermodynamic parameters were computed to add insights
850
into the corrosion inhibition mechanism.
an
us
cr
ip t
839
M
851 852
Ac ce pt e
d
853 854 855
Figure 6. Molecular structures of carrageenan repeat unit.
856 857 858 859
860
Dextrin and cyclodextrins
861
Dextrin is a class of low molecular weight carbohydrate polymers structurally characterized by
862
glucose (D) units linked by glycosidic bonds [α-(1→4) or α-(1→6)]; Figure 7. They occur
863
naturally in the human digestive system via amylases catalyzed starch hydrolysis in the human
864
mouth;
it
can
also
be
synthesized
by
heat
treatment
in
acidic
solutions
31
Page 31 of 74
(https://en.wikipedia.org/wiki/Dextrin). Various forms of dextrin exist in nature ranging from
866
maltodextrin, amylodextrin, α , β -dextrin, cyclic and highly branched cyclic dextrin compounds.
867
Apart from being employed as food additives and in brewing, short chain dextrin as well as the
868
highly branched cyclic derivatives have been deployed as corrosion inhibitors in various
869
corrosive media (Jayalakshmi and Muralidharan, 1997); earlier researches date back between the
870
late 1970’s and the early 1980’s for titanium and aluminium/copper alloys, respectively (Shibad
871
and Balachandra, 1976; Patel et al. 1981; Talati and Modi, 1976).
cr
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865
an
us
872
873
Figure 7: Molecular structure of dextrin
875
Loto and Loto (2014) have reported the effect of dextrin and thiourea additives on the corrosion
876
of steel (low carbon grade) after electroplating the surface with zinc by applying negative
877
potential between with a zinc electrode connected to the steel test substrate in ZnCl2 solution.
878
The corrosion test was conducted in an acid chloride electrolyte. The electroplating procedure
879
revealed densely packed zinc crystals on steel without pores but the substrates possessed
880
different surface morphologies for every plating period under study. Dextrin in combination with
881
thiourea additive demonstrated remarkable superior protection at the highest plating period
882
compared to the rest of the matrices as examined by SEM/ EDS. The anticorrosion properties of
883
β-cyclodetrin-modified acrylamide polymer have been investigated 0.5 M H2SO4 for X70 steel
884
grade by electrochemical and surface analytical techniques. Potentiodynamic polarization results
885
revealed that this modified carbohydrate influenced both cathodic and anodic reactions with a
886
magnitude of % η greater than 84.9% for 150 mg/l at 303 K. Adsorption of the hybrid polymer
887
on metal surface followed Langmuir adsorption isotherm and corrosion inhibition was explained
888
by means of thermodynamic and kinetics parameters. Corrosion inhibition was attributed to
889
molecular adsorption at the metal surface, confirmed by SEM/EDS (Zou et al. 2014a). Zou et al.
890
(2014b) have investigated the efficacy of bridged β-cyclodextrin-polyethylene glycol (β-DP) for
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874
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Page 32 of 74
Q235 carbon steel in 0.5 M HCl using chemical and electrochemical techniques. β-DP was
892
characterized by FTIR reacting after being synthesized via a reaction between β-cyclodextrin
893
with polyethylene glycol. Tafel polarization curves revealed that this hybrid biopolymer was a
894
mixed type inhibitor compound in the solution of the electrolyte while corrosion inhibition was
895
attributed the formation of protective β-DP film at the surface of the metal; this was confirmed
896
by SEM/EDX. Recently, authors have also reported the scale inhibition using β-DP composite
897
for produced-water in shale gas well with up to 89.1% maximum scaling inhibition efficiency for
898
180 mg/l (Liu et al. 2016). Yan et al. (2014) have reported the effectiveness of polyacrylamide
899
modified β-cyclodextrin composite for inhibition of X70 steel corrosion in in 0.5 M H2SO4 using
900
electrochemical and chemical methods and surface analytical techniques. Corrosion inhibition in
901
the presence of this composite was found to increase with its concentration but not with
902
temperature while the trend in Tafel polarization data revealed that polyacrylamide/β-
903
cyclodextrin composite was a mixed type inhibitor system. Corrosion inhibition was attributed to
904
molecular (chemisorption) adsorption of this composite on the metal surface and the adsorption
905
phenomenon followed Langmuir isotherm. SEM results revealed the formation of
906
polyacrylamide/β-cyclodextrin composite protective film on X70 steel surface. Liu et al. (2015)
907
have studied the anticorrosion properties of chitosan-grafted β-cyclodextrin composite for carbon
908
steel corrosion in 0.5 M HCl using weight loss, potentiodynamic polarization, EIS and
909
SEM/EDS techniques. DC polarization curves reveal that the presence of this inhibitor
910
composite affected both cathodic and anodic reaction with 96.02% as the highest inhibition
911
efficiency at 230 ppm. Corrosion inhibition of carbon steel in the presence of this composite was
912
also attributed molecular adsorption, and its adsorption process was approximated with
913
Langmuir adsorption isotherm. Physisorption/chemisorption adsorption mechanism was also
914
proposed from the variation in thermodynamic parameters. Fan et al. (2014) have reported the
915
synthesis of hydroxypropyl-β-cyclodextrin/ octadecylamin supramolecular complex with
916
anticorrosion properties for Q235A steel. Corrosion study was conducted in CO2 saturated
917
deionized water (at 5.6 pH) at room temperature using chemical and electrochemical techniques
918
after the characterization of the synthesized supramolecular complex with FTIR, XRD and NMR
919
spectroscopy. Corrosion inhibition efficiency of 95% was obtained for the synthesized complex
920
and the inhibition process was attributed to the formation of passive inhibitor layer as well as
921
hydrophobic octadecylamin inherent in the supramolecular complex at the metal surface. The
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Page 33 of 74
complex acted predominantly anodic than cathodic from the trend of Tafel polarization results
923
with 90% inhibition efficiency obtained for 50 mg/l complex.
924
Alginates
925
This acid-type anionic polysaccharide is the principle component in the colloidal gum found in
926
the cell walls of algae and seaweeds where it binds with molecular water. Alginate is a group of
927
sugars also called alginic acid (due to the carboxylic acid functional group attached to their
928
molecular structure) or algin; they are linear copolymers with covalently bound (1-4)-linked β-D-
929
mannuronate and C-5 epimer α-L-guluronate homopolymeric blocks (Figure 8). Alginates have
930
numerous forms depending on their salts (principally alkaline or alkaline salts). Na alginate
931
extracts from brown seaweeds are widely deployed as dental gelling agents, and their usage is
932
common in pharmaceutical as well as food industries. K and Ca alginates are used as industrial
933
alternatives to Na alginates while the organic forms of this compound have also been synthesized
934
with various applications.
935 936
Ac ce pt e
d
M
an
us
cr
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922
Figure 8. Molecular structure of alginate.
937
Alginates have also been widely reported as corrosion inhibitors for various metals in different
938
media, and one of the earliest reports with regards to alginate is the one by the Desai’s in the late
939
70’s (Desai and Desai, 1970) where the effect of Na alginate on the cathode and anode potentials
940
of A1-3S in 0.2 N NaOH was evaluated. Sriram et al. (2014) have studied the anticorrosion
941
properties of Na alginate extracts from a brown seaweed (Turbinaria ornate) for aluminium
942
alloy (AA 7075 grade) in 3.5 wt% NaCl using potentiodynamic polarization technique. This
943
extract was found to inhibit aluminium corrosion to a great extent, with 95% inhibition
944
efficiency obtained at 2000 ppm after 24 h. Authors attributed this to the adsorption of
945
inhibition-inducing functional groups found on the extract; this was also confirmed with FTIR
946
spectroscopy. This compound has also been reported for carbon steel corrosion in 0.5 M HCl
947
investigated by chemical and electrochemical techniques (Al-Bonayan, 2014). Corrosion 34
Page 34 of 74
inhibition was found to increase with the concentration of Na alginate but not with temperature;
949
this was attributed to the adsorption of sodium alginate at the metal surface. Molecular
950
adsorption was explained by means of isotherm and activation parameters derived from results of
951
the chemical technique, while the effect of concentration of the inhibitor on the charge transfer
952
resistance and capacitance of double layer was also explained. Zaafarany (2012) have also
953
reported the application of alginate (apple derived)-anionic polyelectrolytes as corrosion
954
inhibitors for pure aluminum in 4 M NaOH at 25 oC using gravimetric and gasometric
955
techniques. A corrosion inhibition efficiency of 86.66% was recorded for 1.6% alginate at 30 oC
956
in the alkaline test solution. Al corrosion reduction in this medium was attributed to the unique
957
functional chemistry on the inhibitor, and the mechanism of inhibition was explained in terms of
958
kinetic and thermodynamic parameters. Deployed form magnesium test substrate (AZ31 alloy
959
grade), Na alginate have also been recently studied by another group of authors in 3.5 wt% NaCl
960
(Dang et al. 2015). They found that corrosion inhibition increased with concentration of Na
961
alginate though a decrease in magnesium protection was also observed after prolonged
962
immersion in the solution of the inhibitor. A corrosion inhibition efficiency of 90% was obtained
963
for 500 ppm Na alginate, and this was attributed to molecular adsorption and subsequent
964
formation of compact film (freshly generated magnesium hydroxide) on the metal surface.
965
Tawfik (2015) has synthesized and appropriately characterized alginate surfactant derivatives for
966
anticorrosion application. These surfactants were deployed as corrosion inhibitors for carbon
967
steel in 1 M HCl using chemical, electrochemical and surface analytical techniques. Corrosion
968
inhibition increased with the concentration of these compounds and with temperature, with a
969
96.27% inhibition efficiency obtained for 5 mM alginate derived cationic surfactant complexed
970
with copper. Tafel curves revealed that these inhibitors were mixed type though predominantly
971
cathodic. Parameters derived from thermodynamic and activation evaluations of the trend in
972
experimental results were employed to investigate the inhibition mechanism. Wang et al (2015)
973
have recently investigated the anticorrosion properties of Ca alginate gel loaded with imidazoline
974
quaternary ammonium salts; this composite was prepared by piercing-solidifying method
975
designed to automatically release these imidazoline corrosion inhibitors at the metal surface
976
(P110 steel) immersed in CO2-saturated 3.5 wt% NaCl medium. Corrosion studies were
977
conducted by EIS while UV-Vis spectroscopy and SEM complemented the electrochemical
978
technique as surface analytical techniques. This auto-release inhibition type system was effective
Ac ce pt e
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to a great extent as the corrosion inhibitors were released from the gel as it swells in the solution
980
of the corrosive electrolyte. BaSO4 was also encapsulated within alginate/ imidazoline composite
981
in order to aid sinking and improved corrosion retardation was well. Hydroxyl propyl alginate,
982
an organic type alginate derivative, have been deployed to reduce mild steel corrosion in 1 M
983
HCl at room temperature using chemical and electrochemical techniques. Corrosion inhibition
984
was found to increase with the concentration of this compound due to molecular (physisorption)
985
adsorption at the metal surface; confirmed by SEM, AFM and FTIR as adsorbed film. Results
986
from Tafel polarization revealed that corrosion inhibition in the presence of this compound
987
affects both anodic and cathodic reactions. Inhibitor adsorption was also explained in terms of
988
adsorption isotherm, thermodynamic and kinetic parameters (Sangeetha et al. 2016). Typical
989
examples of inhibition systems involving dextrin, alginates and their derivatives deployed for
990
metal corrosion reduction in various aggressive media are presented in Table 4.
991
Effect of halide ion additives on corrosion inhibition with carbohydrate polymers
992
In many aggressive media, depending of the service environment to which an organic inhibitor is
993
being deployed, corrosion inhibition is normally aimed at achieving the maximum reduction in
994
metal dissolution with the utmost efficiency (Eduok et al. 2013; Eduok and Khaled 2014, 2015).
995
With this in mind, the improvement of the performance of any inhibition system employed
996
becomes a very importance aspect of the whole corrosion reduction program. Researchers
997
worldwide over the years have developed a number of additives to synergistically aid corrosion
998
reduction in the presence of organic compounds regardless of their modes of action and surface
999
chemistries; almost of these additives are halides (Eduok et al. 2012; Umoren et al 2008c). The
1000
application of some halides with organic inhibitors have been widely reported as having greater
1001
total inhibition effect compared to when only one of inhibitors used independently; hence
1002
synergism (Caliskan and Bilgic 2000; Ridhwan et al. 2012; Tang et al. 2006; Bouklah et al 2006;
1003
Bentiss et al. 2002). This unique property of halides has been largely linked with the formation
1004
of ion-pairs between the organic inhibitors and the halide ions leading to increased surface
1005
coverage. Since molecular adsorption is a key factor in corrosion inhibition, the ionic radii as
1006
well as the electronegativity of these ions have been conceived to contribute immensely to
1007
corrosion inhibition. Synergistic effect of halide ions have been found to follow this order
1008
depending on their ionic radii (pm): I─ (206) > Br─ (182) > Cl─ (167). Iodides, in particular, have
Ac ce pt e
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Page 36 of 74
been known for improved inhibition due to their hydrophobicity and the stabilization of adsorbed
1010
ions with the cations of most organic polymers leading to increased metal surface coverage
1011
(Bouklah et al. 2006). The initial adsorption of iodide ions on the surface of metal substrate aids
1012
further molecular adsorption of organic inhibitor by coulombic attraction thereby forming more
1013
stable protective film at the metal/solution interface (Musa et al. 2011; Harek and Larabi 2004).
1014
Since most organic inhibitors are thermally unstable, their usage in combination with halides
1015
becomes necessary, prompting enhanced metal surface protection from aggressive ions and
1016
molecules at increased temperature. Umoren and Solomon (2015) have recently reported a
1017
comprehensive review on the some inhibitor─halide systems for metal inhibition, yet studies
1018
involving the effects of halide ions on the corrosion inhibition of biopolymers are a scare,
1019
although there have been more investigations (Umoren et al. 2010; Rajeswari et al. 2013;
1020
Arukalam et al. 2015) on substituted cellulose compounds than any other class of carbohydrate
1021
biopolymer in the literature (See Table 5 for list of carbohydrate ploymer-halide inhibition
1022
systems deployed for metal corrosion studies in various aggressive media including the reasons
1023
for corrosion inhibition in the presence of the halide.
M
an
us
cr
ip t
1009
The effect of halide ions (Cl─, Br─, and I─) additives at 30–60 oC on the inhibition
1025
performance of CMC on mild steel corrosion in 2 M H2SO4 has been investigated using weight
1026
loss and hydrogen evolution techniques (Umoren et al. 2010). In the presence of the halide
1027
additives, corrosion inhibition was found to be dependent on their concentrations as well as the
1028
solution temperature and immersion period. Mild steel corrosion inhibition for CMC increased
1029
greatly in the presence of the iodide ions, and this was attributed to a synergistic effect while the
1030
presence of chloride ions antagonized the proposed inhibition process, with and without the
1031
principal inhibitor (CMC), from the results of both corrosion monitoring techniques. The weight
1032
loss technique at 30 oC revealed magnitudes of corrosion inhibition efficiency (% η ) of 89 and
1033
65%, respectively, in the presence and absence of 5 mM I─, while 48 and 63 % were recorded for
1034
5 mM Cl─ and Br─. Corrosion inhibition was linked with metal surface adsorption of inhibitor
1035
compounds and this followed Langmuir adsorption isotherm in the presence of the halide ions.
1036
Conversely, corrosion performance for each halide ion deceased with temperature due to
1037
molecular desorption at higher solution temperatures. In another study, authors have reported the
1038
enhance inhibition performance of hydroxypropyl methylcellulose and hydroxyethyl cellulose
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1024
37
Page 37 of 74
(substituted cellulosic compounds; SCC) in 0.5 M H2SO4 for aluminium (AA 1060 type) and
1040
mild steel using weight loss and electrochemical polarization and impedance spectroscopy
1041
(Arukalam et al., 2014a,b; Arukalam, 2014). The formation of passive oxide film on the Al
1042
surface was found to great dissolve in the acidic test solution, but the rate of dissolution
1043
decreased on addition of SCC. Improved protection for SCC was recorded in the presence of 500
1044
mg/L KI as EIS revealed increased corrosion resistance in the presence of this halide ion.
1045
Adsorption of SCC in the presence of the iodide ions on Al followed Freundlich (Arukalam et
1046
al., 2014a,b) and Langmuir (Arukalam, 2014) adsorption isotherm models. Hydroxypropyl
1047
methylcellulose-KI was revealed as a mixed-type inhibitor (though dominantly cathodic) from
1048
Tafel results. Authors further explained the relationship between hydroxypropyl methylcellulose
1049
adsorption and corrosion mechanism using DFT approach to quantum chemical calculations.
1050
Another corrosion inhibition performance of a biopolymer (ethyl hydroxyethyl cellulose; EHC)
1051
attributed to synergistic effect of iodide ion addition has been reported for mild steel in 1 M
1052
H2SO4 using experimental (chemical and electrochemical) and theoretical (quantum chemical
1053
calculations by DFT) evaluations (Arukalam et al., 2014c). Corrosion resistance was found to
1054
increase in the presence of 0.5 g/L KI added to the test solution with % η values up 58 and 52%
1055
recorded in the presence and absence of KI. Polarization results revealed that both EHC and
1056
EHC─KI were mixed-type inhibitor systems though predominantly cathodic while their
1057
adsorption followed Langmuir isotherm. Experimental evaluations were preceded by theoretical
1058
molecular orbitals and reactivity assessments of EHC’s structure in other to correlate its
1059
adsorption to the mechanism of inhibition using DFT. The effect of halide ions on the inhibition
1060
performances of exudate gums extracted from floral sources have also been investigated for
1061
some metal substrates in different media. In alkaline and acidic medium, the effectiveness of
1062
Gum Arabic (GA) towards the corrosion inhibition of Al has also been studied in the presence of
1063
these halide additives between 30 and 60 oC, using hydrogen evolution and thermometric
1064
techniques (Umoren, 2009; Umoren et al., 2006). The corrosion inhibition of GA of Al in 0.1 M
1065
NaOH and H2SO4 was enhanced in the presence of the iodide ions due to synergistic effect, and
1066
values of % η of GA-KI systems increased with temperature with corrosion inhibition attributed
1067
to adsorption (obeying Temkin adsorption isotherm in NaOH and Langmuir, Temkin and
1068
Freundlich in H2SO4). Corrosion performance of GA was greatly reduced in the presence of
1069
chloride ions, demonstrating antagonist effect for Al substrate in both corrodents. Al corrosion
Ac ce pt e
d
M
an
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1039
38
Page 38 of 74
inhibition followed the order I─> Br─ > Cl─. Umoren and Ebenso (2009) have investigated the Al
1071
corrosion inhibition with exudate gum extracted from Raphia hookeri and the effects of KCl,
1072
KBr and KI addition on its potency in 0.1 M HCl. Authors employed weight loss, hydrogen
1073
evolution and thermometric techniques in their evaluation for all the systems studied between
1074
30-60 oC. From the results of the findings, it was revealed that the inhibition performance of this
1075
gum extract was found to increase synergistically with KI and KBr in the solution of the acid
1076
electrolyte while KCl disallowed the adsorption of the gum unto the metal surface, thereby
1077
reducing its corrosion efficiency. Raphia hookeri exudates gum inhibition was attributed to
1078
molecular adsorption of its chemical constituents and this was collaborated with Freundlich,
1079
Langmuir and Temkin adsorption isotherms. Similar study have been reported for a Pachylobus
1080
edulis gum-KI system in 2 M H2SO4 using hydrogen evolution and thermometric methods
1081
investigated between 30–60 oC for mild steel corrosion (Umoren and Ekanem, 2010). Corrosion
1082
rate of the mild steel substrate reduced in the presence of the gum extract but more with the
1083
extract in combination with KI. Corrosion inhibition for both gum and gum-KI systems reduced
1084
with immersion time and with solution temperature. Physical adsorption was proposed from the
1085
dependence of temperature with trend of corrosion inhibition in the presence of the inhibitors
1086
studied; and adsorption was approximated with Temkin adsorption isotherm.
1087
Future perspective: computational approach to corrosion inhibition
1088
In some cases where core experimental results are inclusive, computational approach to
1089
corrosion inhibition is necessary. Experimental evaluations should always be supported with
1090
theoretical-based assessments of inhibition phenomena; especially the use of molecular
1091
modelling tools in correlating corrosion inhibition mechanisms with molecular structures of the
1092
inhibitor compounds (Obot et al. 2009,2010,2013; Ebenso et al., 2012; Kabanda et al., 2012).
1093
Quantum chemical modelling has been widely used in studying molecular orbitals and reactivity
1094
of organic inhibitors in other to fully understand their adsorption on metal surfaces in any
1095
aggressive (ionic) medium (Obot and Obi-Egbedi, 2010; Ebenso et al., 2012; Kabanda et al.,
1096
2012; Obot et al., 2013, 2015; Kayaa et al., 2015; Sasikumar et al., 2015; Obot, 2014). Since the
1097
mechanism of corrosion inhibition is not fully understood, model-based theoretical computations
1098
allows for an attempt to elucidate the possible phases of inhibition reactions in complex systems,
1099
hence, solving some obscured surface adhesion problems by mechanistic predictions of
Ac ce pt e
d
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an
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1070
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Page 39 of 74
applicable parameters. Carbohydrates from gum exudate show reliable reduction towards
1101
corrosion of metal substrates deployed in acidic and alkaline media, yet, it is difficult to assign
1102
inhibition to one chemical specie amongst the lot abound in these extracts. Bio-gums alone
1103
are mixtures of polysaccharides and/or glycoproteins, with typical arabinose and ribose sources.
1104
However, the use to molecular dynamics simulation (MDS) could serve as a very effective tool is
1105
studying the absorption of principal chemical constituents on the surfaces of metals, and also
1106
further explain the inhibitor-metal surface interaction, giving multiple views on possible
1107
molecular motions in the microscopic level (Obot et al., 2015; Kayaa et al., 2015; Obot, 2014).
1108
The principle of classical MDS could also help in computing time-dependent properties of this
1109
complex molecular systems as well as giving practical information about most stable
1110
conformations of inhibitor constituents prior to adsorption. Aspects of MDS could also include
1111
the study of the complexities and dynamics of inhibition processes involving polysaccharide
1112
polymeric systems by relating their inhibition mechanisms with conformational changes and
1113
surface stability (Obot et al., 2015; Kayaa et al., 2015; Sasikumar et al., 2015; Obot, 2014).
1114
Another aspect of molecular structure contributing to corrosion inhibition is the energy gap and
1115
the energies associated with frontier orbitals. Using Density Functional Theory (DFT), energies
1116
of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital
1117
(LUMO) have been widely collaborated with corrosion inhibition in terms of molecular
1118
adsorption sites on surfaces (Obot and Obi-Egbedi 2010; Ebenso et al. 2012; Kabanda et al.
1119
2012; Obot et al. 2009; Obot et al. 2013). The use of MDS and quantum chemical computational
1120
tools is therefore necessary for future studies of adsorption processes involving corrosion
1121
inhibition with carbohydrate biopolymers. Only few reports are available in the literature with
1122
regards to the application of quantum chemical computations (EL-Haddad 2013, 2014; Arukalam
1123
et al. 2014a, 2015; Umoren et al. 2015; Alsabagh et al. 2014).
cr
us
an
M
d
Ac ce pt e
1124
ip t
1100
1125
Concluding remarks
1126
Temperature and solution pH are some of the few factors affecting the rate of metal dissolution
1127
in any service environment to which they are deployed; and this can be hugely reduced if
1128
efficient control procedure is employed to revert the overall corrosion dynamics. The use of 40
Page 40 of 74
biopolymers is gaining grounds in the fabrication of inhibitor formulations for various field
1130
applications, and their chemistry is simple since the adsorption mechanism accompanying them
1131
involves either physical adsorption at metal surfaces, or by chemisorption. Some mixtures of
1132
carbohydrate polymers are also known to contain chemical constituents capable of forming
1133
passivation layers that prevents the passage of corrosive ions and molecule across the
1134
metal/solution interface.
1135
Carbohydrate biopolymers, as used in this review, are macro-compounds that possess
1136
monomeric units covalently bonded to form long macromolecular sugar chains with relatively
1137
high molecular masses. They are readily available in nature, benign, renewable and ecofriendly
1138
alternative to other organic inhibitors with toxic potentials. In corrosion inhibition, they represent
1139
a set of chemically stable, biodegradable and ecofriendly macromolecules with reliable inhibiting
1140
strengths for metal surface protection; making them effective protective coatings and metal
1141
linings. This review work has elaborately described the inhibition of metal corrosion using some
1142
green pure polysaccharide biopolymers as well as their mixtures (including modifications and
1143
nanocomposites) found in the literature. Exudate gums, cellulose, starch, pectin and pectates,
1144
chitosans and carrageenan, alginate and dextrin have been reviewed including the effects of
1145
halide additives on their anticorrosion performances. Molecular weights and molecular
1146
structures/symmetry and functional group chemistry are few characteristics of these compounds
1147
that have been also described to affect the mechanisms of their protection in aqueous media. The
1148
mechanism of molecular adsorption in the presence of halide ion leads to increased metal surface
1149
coverage, and this has been explained with typical examples based on formation of ion-pairs.
1150
Corrosion inhibition with polymer-halide conjugates have also been described in terms of
1151
coulombic attraction between polymers and halide ions at the metal/solution interface, thereby
1152
forming more stable protective film. Corrosion process designs are best understood if at the
1153
molecular level, the important factors conceived to affect the behavior of the system are
1154
addressed. Such approach is better explained using computational/theoretical tools. Apart from
1155
fostering further understanding of corrosion processes, the theoretical correlating of inhibition
1156
mechanisms with molecular structures of the carbohydrate polymeric compounds will also aid
1157
the studying of molecular orbitals and reactivity of inhibitors as a key to understanding
1158
adsorption on surfaces. Molecular dynamic simulations also allows for the studying of stable
Ac ce pt e
d
M
an
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1129
41
Page 41 of 74
conformations prior to adsorption as well as the time-dependent properties of this complex
1160
molecular systems.
1161
Acknowledgments
1162
The authors gratefully acknowledged Centre of Research Excellence in Corrosion, Research
1163
Institute, KFUPM and King Fahd University of Petroleum and Minerals (KFUPM) for supporting
1164
the work.
1165
References
1166
Abdallah M (2004) Guar Gum as Corrosion Inhibitor for Carbon Steel in Sulfuric Acid
cr
us
1167
ip t
1159
Solutions. Portugaliae Electrochimica Acta 22: 161-175
Abu-Dalo MA, Othman AA, Al-Rawashdeh NAF (2012) Exudate Gum from Acacia Trees as
1169
Green Corrosion Inhibitor for Mild Steel in Acidic Media. International Journal of
1170
Electrochemical Science 7: 9303 – 9324
M
an
1168
Aghzzaf AA, Rhouta B, Steinmetz J, Rocca E, Aranda L, Khalil A, Yvon J, Daoudi L (2012)
1172
Corrosion inhibitors based on chitosan-heptanoate modified beidellite. Applied Clay
1173
Science 65-66: 173-178
d
1171
Ahmed RA, Farghali RA, Fekry AM (2012) Study for the Stability and Corrosion Inhibition of
1175
Electrophoretic Deposited Chitosan on Mild Steel Alloy in Acidic Medium. International
1176
Journal of Electrochemical Science 7: 7270 – 7282
Ac ce pt e
1174
1177
Al-Bonayan AM (2014) Sodium Aliginate as Corrosion Inhibitor for Carbon Steel in 0.5 M HCl
1178
Solutions. International Journal of Scientific & Engineering Research 5(4): 611-618
1179
Alsabagh AM, Elsabee MZ, Moustafa YM, Elfky A, Morsi RE (2014) Corrosion inhibition
1180
efficiency of some hydrophobically modified chitosan surfactants in relation to their
1181
surface active properties. Egyptian Journal of Petroleum 23: 349–359
1182
Ameh PO, Eddy NO (2014) Characterization of Acacia Sieberiana (AS) Gum and Their
1183
Corrosion Inhibition Potentials for Zinc in Sulphuric Acid Medium. International Journal
1184
of Novel Research in Physics, Chemistry & Mathematics 1(1): 25-36
1185
Ameh PO, Magaji L, Salihu T (2012) Corrosion inhibition and adsorption behaviour for mild
1186
steel by Ficus glumosa gum in H2SO4 solution. African Journal of Pure and Applied
1187
Chemistry 6: 100-106 42
Page 42 of 74
1188
Antony N, Sherine HB, Rajendran S (2010) Investigation of the inhibiting effect of
1189
carboxymethylcellulose-Zn2+ system on the corrosion of carbon steel in neutral chloride
1190
solution. Arabian Journal for Science and Engineering, 35: 42-52 Arthur DE, Jonathan A, Ameh PO, Anya C (2013) A review on the assessment of polymeric
1192
materials used as corrosion inhibitor of metals and alloys. International Journal of
1193
Industrial Chemistry 4: 2-9
1195
Arukalam IO (2012) The inhibitive effect of hydroxyethylcellulose on mild steel corrosion in hydrochloric acid solution. Academic Research International 2: 35-42
cr
1194
ip t
1191
Arukalam IO (2014) Durability and synergistic effects of KI on the acid corrosion inhibition of
1197
mild steel by hydroxypropyl methylcellulose. Carbohydrate Polymers 112: 291–299
1198
Arukalam IO, Madufor IC, Ogbobe O, Oguzie E (2014a) Experimental and Theoretical Studies
1199
of Hydroxyethyl Cellulose as Inhibitor for Acid Corrosion Inhibition of Mild Steel and
1200
Aluminium. The Open Corrosion Journal 6: 1-10
an
us
1196
Arukalam IO, Madu IO, Ijomah NT, Ewulonu CM, Onyeagoro GN (2014b) Acid corrosion
1202
inhibition and adsorption behaviour of ethyl hydroxyethyl cellulose on mild steel
1203
corrosion. Journal of Materials doi.org/10.1155/2014/101709
M
1201
Arukalam IO, Madufor IC, Ogbobe O, Oguzie EE (2014c) Hydroxypropyl methylcellulose as a
1205
polymeric corrosion inhibitor for aluminium. Pigment & Resin Technology 43: 151 – 158
1206
Arukalam IO, Madufor IC, Ogbobe O, Oguzie EE (2014d) Acidic corrosion inhibition of copper
1207
by Hydroxyethyl cellulose. British Journal of Applied Science & Technology 4: 1445-
1208
1460
Ac ce pt e
d
1204
1209
Arukalam IO, Madufor C, Ogbobe O, Oguzie EE (2015) Inhibition of mild steel corrosion in
1210
sulfuric acid medium by hydroxyethyl cellulose. Chemical Engineering Communications
1211
202:112–122
1212
Atta AM, El-Mahdy GA, Al-Lohedan HA, Ezzat ARO (2015) Synthesis of nonionic amphiphilic
1213
chitosan nanoparticles for active corrosion protection of steel. Journal of Molecular
1214
Liquids 211: 315–323
1215
Aziz MA, Cabral JD, Brooks HJL, Moratti SC, Hanto LR (2012) Antimicrobial properties of a
1216
chitosan dextran-based hydrogel for surgical use. Antimicrobial Agents and
1217
Chemotherapy 56 1: 280-287
43
Page 43 of 74
1218
Bayol E, Gürten AA, Dursun M, Kayakirilmaz K (2008) Adsorption behavior and inhibition
1219
corrosion effect of sodium carboxymethyl cellulose on mild steel in acidic medium. Acta
1220
Physico-Chimica Sinica 24:2236-2243
1222
Banerjee S, Srivastava V, Singh MM (2012) Chemically modified natural polysaccharide as green corrosion inhibitor for mild steel in acidic medium. Corrosion Science 59: 35–41
ip t
1221
Behpour M, Ghoreishi SM, Khayatkashani M, Soltani N (2011) The effect of two oleo-gum resin
1224
exudate from Ferula assa-foetida and Dorema ammoniacum on mild steel corrosion in
1225
acidic media. Corrosion Science 53: 2489–2501
cr
1223
Bello M, Ocho N, Balsamo V, López-Carrasquero F, Coll S, Monsalve A, González G (2010)
1227
Modified cassava starches as corrosion inhibitors of carbon steel: An electrochemical and
1228
morphological approach. Carbohydrate Polymers 82: 561–568
us
1226
Bentiss F, Bouanis M, Mernari B, Traisnel M, Lagrenee M (2002) Effect of iodide ions on
1230
corrosion inhibition. of mild steel by 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole in
1231
sulfuric acid solution. Journal of Applied Electrochemistry 32: 671–678
1233
M
1232
an
1229
Bentrah H, Rahali Y, Chala A (2014) Gum Arabic as an eco-friendly inhibitor for API 5L X42 pipeline steel in HCl medium. Corrosion Science 82: 426–431 Biswas A, Pal S, Udayabhanu G (2015), Experimental and theoretical studies of xanthan gum
1235
and its graft co-polymer as corrosion inhibitor for mild steel in 15% HCl. Applied
1236
Surface Science 353:173 -183.
Ac ce pt e
d
1234
1237
Bouklah M, Hammouti B, Aouniti A, Benkaddour M, Bouyanzer A (2006) Synergistic effect of
1238
iodide ions on the corrosion inhibition of steel in 0.5 M H2SO4 by new chalcone
1239
derivatives. Applied Surface Science 252: 6236–6242
1240
Brindha T, Mallika J, Sathyanarayana MV (2015) Synergistic effect between starch and
1241
substituted piperidin-4-one on the corrosion inhibition of mild steel in acidic medium.
1242
Journal of Materials and Environmental Science 6: 191-200
1243 1244
Brown WH, Poon T (2005) Introduction to Organic Chemistry (3rd ed.) Wiley. ISBN 0-47144451-0
1245
Busch VM, Kolender AA, Santagapita PR, Buera MP (2015) Vinal gum, a galactomannan from
1246
Prosopis ruscifolia seeds: Physicochemical characterization. Food Hydrocolloids 51:
1247
495-502
44
Page 44 of 74
1248 1249
Caliskan N, Bilgic S (2000) Effect of iodide ions on the synergistic inhibition of the corrosion of manganese-14 steel in acidic media. Applied Surface Science 153: 128–133 Carneiro J, Tedimb J, Fernandesa SCM, Freire CSR, Silvestre AJD, Gandinia A, Ferreirab MGS,
1251
Zheludkevich ML (2012) Chitosan-based self-healing protective coatings doped with
1252
cerium nitrate for corrosion protection of aluminum alloy 2024. Progress in Organic
1253
Coatings 75: 8–13
ip t
1250
Carneiro J, Tedim J, Fernandes SCM, Freire CSR, Gandini A, Ferreira MGS, Zheludkevich M.L
1255
(2013a) Chitosan as a Smart Coating for Controlled Release of Corrosion Inhibitor 2-
1256
Mercaptobenzothiazole. ECS Electrochemical Letters 2(6): 2162-8726
us
cr
1254
Carneiro J, Tedim J, Fernandes SCM, Freire CSR, Gandini A, Ferreira MGS, Zheludkevich ML
1258
(2013b) Functionalized chitosan-based coatings for active corrosion protection. Surface
1259
& Coatings Technology 226: 51–59
an
1257
Chaires-Martínez L, Salazar-Montoya JA, Ramos-Ramírez EG (2008) Physicochemical and
1261
functional characterization of the galactomannan obtained from mesquite seeds (Prosopis
1262
pallida). European Food Research and Technology 227: 1669-1676
M
1260
Chakravarthy MP, Mohana KN (2014) Adsorption and corrosion inhibition characteristics of
1264
some nicotinamide derivatives on mild steel in hydrochloric acid solution. ISRN
1265
Corrosion doi.org/10.1155/2014/687276
Ac ce pt e
d
1263
1266
Chauhan K, Kumar R, Kumar M, Sharma P, Chauhan GS (2012) Modified pectin-based
1267
polymers as green antiscalants for calcium sulfate scale inhibition. Desalination 30:31–37
1268
Cheng S, Chen S, Liu T, Chang X, Yin Y (2007) Carboxymethyl chitosan-Cu2+ mixture as an
1269 1270 1271
inhibitor used for mild steel in 1.0 M HCl. Electrochimica Acta 52:5932–5938 Chung YC, Yeh, JY, Tsai CF (2011) Antibacterial characteristics and activity of water-soluble chitosan derivatives prepared by the maillard reaction. Molecules 16: 8504-8514
1272
Dang N, Wei YH, Hou LF, Li YG, Guo CL (2015) Investigation of the inhibition effect of the
1273
environmentally friendly inhibitor sodium alginate on magnesium alloy in sodium
1274
chloride solution. Materials and Corrosion 66: 1354-1362
1275 1276
Desai MN, Desai S.M (1970) Inhibition of the corrosion of A1-3S in NaOH. Corrosion Science 10: 233-237
45
Page 45 of 74
1277
Deyab MA (2015) Hydroxyethyl cellulose as efficient organic inhibitor of zinc-carbon battery
1278
corrosion in ammonium chloride solution: Electrochemical and surface morphology
1279
studies. Journal of Power Sources 280: 190-194
1281
Douiare M, Norton IT (2013) Designer colloids in structured food for the future (short survey). Journal of the Science of Food and Agriculture 93: 3147-3154
ip t
1280
Ebenso EE, Kabanda MM, Arslan T, Saracoglu M, Kandemirli F, Murulana LC, Singh AK,
1283
Shukla SK, Hammouti B, Khaled KF, Quraishi MA, Obot IB, Eddy NO (2012) Quantum
1284
chemical investigations on quinoline derivatives as effective corrosion inhibitors for mild
1285
steel in acidic medium. International Journal of Electrochemical Science 7: 5643 – 5676
us
cr
1282
Eddy NO, Ibok UJ, Ebenso EE (2010) Adsorption, synergistic inhibitive effect and quantum
1287
chemical studies on ampicillin and halides for the corrosion of mild steel. Journal of
1288
Applied Electrochemistry 40: 445-456
an
1286
Eddy NO, Odiongenyi AO, Ameh PO, Ebenso EE, (2012) Corrosion Inhibition Potential of
1290
Daniella Oliverri Gum Exudate for Mild Steel in Acidic Medium. International Journal
1291
of Electrochemical Science 7: 7425 – 7439
M
1289
Eddy NO, Ameh PO, Odiongenyi AO (2014) Physicochemical Characterization and Corrosion
1293
Inhibition Potential of Ficus Benjamina (FB) Gum for Aluminum in 0.1 M H2SO4.
1294
Portugaliae Electrochimica Acta, 32(3): 183-197
Ac ce pt e
d
1292
1295
Eduok UM, Umoren SA, Udoh AP (2012) Synergistic inhibition effects between leaves and stem
1296
extracts of Sida acuta and iodide ion for mild steel corrosion in 1 M H2SO4 solutions.
1297
Arabian Journal of Chemistry 5: 325–337
1298
Eduok U, Inam E, Umoren SA, Akpan IA (2013) Chemical and spectrophotometric studies of
1299
naphthol dye as an inhibitor for aluminium alloy corrosion in binary alkaline medium.
1300
Geosystem Engineering 16: 146-155
1301
Eduok UM, Khaled MM (2014) Corrosion protection of non-alloyed AIAI 316L concrete steel
1302
metal grade in aqueous H2SO4: Electroanalytical and surface analyses with Metiamide.
1303
Construction and Building Materials 68: 285–290
1304
Eduok UM, Khaled M (2015) Corrosion inhibition for low-carbon steel in 1 M
1305
H2SO4 solution by phenytoin: evaluation of the inhibition potency of another
1306
“anticorrosive drug”. Research on Chemical Intermediates 41: 6309-6324
46
Page 46 of 74
1307
Eid S, Abdallah M, Kamar EM, El-Etre AY (2015) Corrosion inhibition of aluminum and
1308
aluminum silicon alloys in sodium hydroxide solutions by methyl cellulose. Journal of
1309
Materials and Environmental Science 6: 892-901
1311 1312 1313
El-Haddad MN (2013) Chitosan as a green inhibitor for copper corrosion in acidic medium. International Journal of Biological Macromolecules 55:142–149
ip t
1310
EL-Haddad MN (2014) Hydroxyethyl cellulose used as an eco-friendly inhibitor for 1018 c-steel corrosion in 3.5% NaCl solution. Carbohydrate Polymers 112: 595–602
El-Sawy SM, Abu-Ayana YM, Abdel-Mohdy FA (2001) Some chitin/chitosan derivatives for
1315
corrosion protection and waste water treatments. Anti-Corrosion Methods and Materials
1316
48(4): 227-234
us
cr
1314
Fan B, Wei G, Zhang Z, Qiao N (2014) Preparation of supramolecular corrosion inhibitor based
1318
on hydroxypropyl-bcyclodextrin/octadecylamine and its anti-corrosion properties in the
1319
simulated condensate water. Anti-Corrosion Methods and Materials 61: 104– 111
1320
Fares MM, Maayta AK, Al-Mustafa JA (2012a) Corrosion inhibition of iota-carrageenan natural
1321
polymer on aluminum in presence of zwitterion mediator in HCl media. Corrosion
1322
Science 65: 223–230
1325 1326
M
d
1324
Fares MM, Maayta AK, Al-Qudah MM (2012b) Pectin as promising green corrosion inhibitor of aluminum in hydrochloric acid solution. Corrosion Science 60: 112–117
Ac ce pt e
1323
an
1317
Fekry AM, Mohamed RR (2010) Acetyl thiourea chitosan as an eco-friendly inhibitor for mild steel in sulphuric acid medium. Electrochimica Acta 55:1933–1939
1327
Feng Y, Lin X, Li H, He L, Sridhar T, Suresh AK, Bellare J, Wang H (2014a) Synthesis and
1328
characterization of chitosan-grafted BPPO ultrafiltration composite membranes with
1329
enhanced antifouling and antibacterial properties. Industrial Engineering Chemistry and
1330
Research 53: 14974−14981
1331 1332
Fiori-Bimbi MV, Alvarez PE, Vaca H, Gervasi CA (2015) Corrosion inhibition of mild steel in HCL solution by pectin. Corrosion Science 92:192–199
1333
Gabriel JS, Tiera MJ, Tiera VAO (2015) Synthesis, characterization, and antifungal activities of
1334
amphiphilic derivatives of diethylaminoethyl chitosan against Aspergillus flavus. Journal
1335
of Agricultural and Food Chemistry 63, 5725−5731
1336
Geethanjali R, Ali A, Sabirneeza F, Subhashini S (2014) Water-Soluble and biodegradable
1337
pectin-grafted polyacrylamide and pectin-grafted polyacrylic acid: Electrochemical 47
Page 47 of 74
1338
investigation of corrosion-inhibition behaviour on mild steel in 3.5% NaCl media. Indian
1339
Journal of Materials Science 2014, doi.org/10.1155/2014/356075 Gräfen H, Horn EM, Schlecker H, Schindler H (2002) Corrosion" Ullmann's Encyclopedia of
1341
Industrial Chemistry, Wiley-VCH: Weinheim, 2002.doi:10.1002/14356007.b01_08
1342
Grassino A, Halambek J, Djaković S, Brnčić S.R, Dent M, Grabarić Z (2016) Utilization of
1343
tomato peel waste from canning factory as a potential source for pectin production and
1344
application as tin corrosion inhibitor. Food Hydrocolloids, 52: 265–274.
cr
1346
Harek Y, Larabi L (2004) Corrosion inhibition of mild steel in 1 mol/dm3 HCl by oxalic Nphenylhydrazide N0 –phenylthiosemicarbazide. Chemistry in Industry 53:55-61
us
1345
ip t
1340
Hassan RM, Fawzy A, Ahmed GA, Zaafarany IA, Asghar BH, Takagi HD, Ikeda Y (2011)
1348
Kinetics and mechanism of permanganate oxidation of iota- and lambda-carrageenan
1349
polysaccharides as sulfated carbohydrates in acid perchlorate solutions. Carbohydrate
1350
Research 346: 2260–2267
an
1347
Hassan R, Zaafarany I, Gobouri A, Takagi H (2013) A revisit to the corrosion inhibition of
1352
aluminum in aqueous alkaline solutions by water-soluble alginates and pectates as
1353
anionic
1354
Doi.org/10.1155/2013/508596
M
1351
inhibitors.
International
Journal
of
Corrosion
d
polyelectrolyte
Hassan RM, Zaafarany IA (2013) Kinetics of corrosion inhibition of aluminum in acidic media
1356
by water-soluble natural polymeric pectates as anionic polyelectrolyte inhibitors.
1357
Materials 6: 2436-2451
1358
Ac ce pt e
1355
HESIS Fact Sheet; Wood Preservatives Containing Arsenic and Chromates; Hazard Evaluation
1359
System and Information Service
1360
(https://www.cdph.ca.gov/programs/hesis/Documents/arsen2.pdf)
1361
Hromádková Z, Malovikova A, Mozeš Š, Sroková IE, Ibringerová A (2008) Hydrophobically
1362
modified pectates as novel functional polymers in food and non-food applications.
1363
BioResources, 3: 71-78
1364
https://en.wikipedia.org/wiki/Chitosan
1365
https://en.wikipedia.org/wiki/Hydroxyethyl_cellulose
1366
Hussein MHM, El-Hady MF, Shehata HAH, Hegazy MA, Hefni HHH (2013) Preparation of
1367
some eco-friendly corrosion inhibitors having antibacterial activity from sea food waste.
1368
Journal of Surfactants and Detergents 16:233–242 48
Page 48 of 74
1369 1370
Jayalakshmi Μ, Muralidharan VS (1997) Inhibitors for aluminium corrosion in aqueous medium. Corrosion Reviews 15(3-4): 315-340 John S, Joseph A, Jose AJ, Narayana B (2015) Enhancement of corrosion protection of mild steel
1372
by chitosan/ZnO nanoparticle composite membranes. Progress in Organic Coatings 84:
1373
28–34
ip t
1371
Kabanda MM, Murulana LC, Ozcan M, Karadag F, Dehri I, Obot IB, Ebenso EE (2012)
1375
Quantum chemical studies on the corrosion inhibition of mild steel by some triazoles and
1376
benzimidazole derivatives in acidic medium. International Journal of Electrochemical
1377
Science 7: 5035 - 5056
1379
us
1378
cr
1374
Kalaivania R, Arasub PT, Rajendran S (2013) Inhibitive nature of carboxymethylcellulose with Zn2+ ion. Chemical Science Transactions 2: 1352-1357
Kayaa S, Tüzüna B, Kaya C, Obot IB (2015) Determination of corrosion inhibition effects of
1381
amino acids: Quantum chemical and molecular dynamic simulation study. Journal of the
1382
Taiwan Institute of Chemical Engineers, doi.org/10.1016/j.jtice.2015.06.009
1385 1386 1387 1388
M
under aerobic conditions. Nature 439: 187–191
Khairou KS, El-Sayed A (2003) Inhibition effect of some polymers on the corrosion of cadmium
d
1384
Keppler F, Hamilton JTG, Bra M, Röckmann T (2006) Methane emissions from terrestrial plants
in a hydrochloric acid solution. Journal of Applied Polymer Science 88:866–871
Ac ce pt e
1383
an
1380
Killaars, J, Finley, P (2001) SPE International Symposium on Oilfield Chemistry. Houston, Texas, SPE 65044
1389
Kim SRB, Choi YG, Kim JY, Lim ST (2015) Improvement of water solubility and humidity
1390
stability of tapioca starch film by incorporating various gums. LWT-Food Science and
1391
Technology doi.org/10.1016/j.lwt.2015.05.009
1392
Klinov IY (1962) New polymeric materials in anticorrosion technology. Trudy. Vsesoyuznoy
1393
Mezhvuzovskoy Nauchnoy Konferentsii po Voprosam Bor’by s Korroziyey (Translations
1394
of the Inter-Higher Educational Institute Scientific Conference on Questions of Fighting
1395
Corrosion). Gostoptekhizdat, Moskva, pp 296–303
1396
Li ML, Li RH, Xu J, Han X, Yao TY, Wang J (2014a) Thiocarbohydrazide-modified chitosan as
1397
anticorrosion and metal ion adsorbent. Journal of Applied Polymer Science DOI:
1398
10.1002/APP.40671.
49
Page 49 of 74
1399
Li M, Xu J, Li R, Wang D, Li T, Yuan M, Wang J (2014b) Simple preparation of aminothiourea-
1400
modified chitosan as corrosion inhibitor and heavy metal ion adsorbent. Journal of
1401
Colloid and Interface Science 417: 131–136
1403 1404 1405
Li R, Feke DL (2015) Rheological and kinetic study of the ultrasonic degradation of locust bean gum in aqueous saline and salt-free solutions. Ultrasonics Sonochemistry 27: 334–338
ip t
1402
Li X, Deng S (2015) Cassava starch graft copolymer as an eco-friendly corrosion inhibitor for steel in H2SO4 solution. Korean Journal of Chemical Engineering 32: 1-8
Li H, Li H, Liu Y, Huang X (2015) Synthesis of polyamine grafted chitosan copolymer and
1407
evaluation of its corrosion inhibition performance. Journal of the Korean Chemical
1408
Society 59: 142-147
us
cr
1406
Liu Y, Zou C, Yan X, Xiao R, Wang T, Li M (2015) β-Cyclodextrin modified natural chitosan as
1410
a green inhibitor for carbon steel in acid solutions. Industrial Engineering Chemistry and
1411
Research 54: 5664−5672
1413
Liu Y, Zou C, Li C, Lin L, Chen W (2016) Evaluation of β-cyclodextrin–polyethylene glycol as
M
1412
an
1409
green scale inhibitors for produced-water in shale gas well. Desalination 377: 28–33 Loto CA, Loto RT (2013) Effect of Dextrin and Thiourea Additives on the Zinc Electroplated
1415
Mild Steel in Acid Chloride Solution. International Journal of Electrochemical Science 8:
1416
12434–12450
1418 1419 1420 1421 1422
Ac ce pt e
1417
d
1414
Luckachan GE, Mittal V (2015) Anti-corrosion behavior of layer by layer coatings of crosslinked chitosan and poly(vinyl butyral) on carbon steel. Cellulose 22: 3275–3290 Manimaran M, Rajendran S, Manivannan M, Thangakani JA, Prabha AS (2013) Corrosion inhibition by carboxymethyl cellulose. European Chemical Bulletin 2: 494-498 Mishra RK, Sutar PB, Singhal JP, Banthia AK (2007) Graft copolymerization of pectin with polyacrylamide. Polymer-Plastics Technology and Engineering, 46: 1079–1085
1423
Mobin M, Khan MA, Parveen M (2011) Inhibition of mild steel corrosion in acidic medium
1424
using starch and surfactants additives, Journal of Applied Polymer Science 121: 1558–
1425
1565
1426 1427
Mohamed RR, Fekry AM (2011) Antimicrobial and anticorrosive activity of adsorbents based on chitosan Schiff’s base. International Journal of Electrochemical Science 6:2488–2508
50
Page 50 of 74
1428
Musa AY, Mohamad AB, Kadhum AAH, Takriff MS, Tien LT (2011) Synergistic effect of
1429
potassium iodide with pthalazone on the corrosion inhibition of mild steel in 1.0 M HCl.
1430
Corrosion Science 53: 3672-3677 Nada C, Katarina B, Sandra P (1996) The inhibition effect of pectin and ascorbic acid on the
1432
corrosion of tin in sodium chloride solution. 47th Annual Meeting of The International
1433
Society of Electrochemistry, Abstracts/The International Society of Electrochemistry
1434
(ed). - The Electrochemical Society, 1996. L6a-3. 47th Annual Meeting of The
1435
International Society of Electrochemistry, Veszprem-Balatonfured, Hungary, 1.-6.09.
1436
1996
cr
us
1437
ip t
1431
Nanaki SG, Kyzas GZ, Tzeremec A, Papageorgiou M, Kostoglou M, Bikiaris DN, Lambropoulou
1439
microparticles for the removal of pharmaceuticals from aqueous solutions. Colloids and
1440
Surfaces B: Biointerfaces 127: 256–265
1442
Synthesis and characterization of modified carrageenan
Obot IB, Obi-Egbedi NO, Umoren SA (2009a) Antifungal drugs as corrosion inhibitors for
M
1441
DA (2015)
an
1438
aluminium in 0.1 M HCl. Corrosion Science 51: 1868–1875 Obot IB, Obi-Egbedi NO (2010) Adsorption properties and inhibition of mild steel corrosion in
1444
sulphuric acid solution by ketoconazole: Experimental and theoretical investigation.
1445
Corrosion Science 52:198–204
Ac ce pt e
d
1443
1446
Obot IB, Ebenso EE, Kabanda MM (2013) Metronidazole as environmentally safe corrosion
1447
inhibitor for mild steel in 0.5 M HCl: Experimental and theoretical investigation. Journal
1448
of Environmental Chemical Engineering 1:431–439
1449
Obot IB (2014) “Recent Advances in Computational Design of Organic Materials for Corrosion
1450
Protection of Steel in Aqueous Media” in Developments in Corrosion Protection,
1451
INTECH, Croatia, p 123 – 151.
1452
Obot IB, Macdonald DD, Gasem ZM (2015) Density functional theory (DFT) as a powerful tool
1453
for designing new organic corrosion inhibitors. Part 1: An overview. Corrosion science
1454
99: 1- 30.
1455 1456
Octel-Starreon
Products:
http://web.archive.org/web/20050218035909/http://www.octel-
starreon.com/Products_RFA_Corrosion.htm
51
Page 51 of 74
1457
Okafor PC, Ikpi ME, Uwah IE, Ebenso EE, Ekpe UJ, Umoren SA (2008) Inhibitory action of
1458
Phyllanthus amarus extracts on the corrosion of mild steel in acidic media. Corrosion
1459
Science 50: 2310–2317 OSHA DATA; General_Facts
1461
https://www.osha.gov/OshDoc/data_General_Facts/hexavalent_chromium.pdf
1462
Patel PR, Pandya JM, Keemtilal (1981) Colloids as corrosion inhibitors for aluminium copper
1465
Peter A, Obot IB, Sharma SK (2015) Use of natural gums as green corrosion inhibitors: an
cr
1464
alloy in hydrochloric acid. Proceedings of Indian National Science Academy 47: 555-561
overview. International Journal of Industrial Chemistry 6: 153 – 164.
us
1463
ip t
1460
Prabakaran M, Ramesh S, Periasamy V, Sreedhar B (2015) The corrosion inhibition performance
1467
of pectin with propyl phosphonic acid and Zn2+ for corrosion control of carbon steel in
1468
aqueous solution. Research on Chemical Intermediates 41:4649–4671
1470 1471 1472
Qu D (2006) Behavior of Dinonylphenol Phosphate Ester and its influence on the oxidation of a Zn anode in alkaline solution. Journal of Power Sources 162: 706–712
M
1469
an
1466
Rabea EI, Badawy MET, Stevens CV, Smagghe G, Steurbaut W (2003) Chitosan as antimicrobial agent: Applications and mode of action. Biomacromolecules 4: 1457-1465 Rahim AA, Rocca E, Steinmetz EJ, Kassim MJ (2008) Inhibitive action of mangrove tannins and
1474
phosphoric acid on pre-rusted steel via electrochemical methods. Corrosion Science 50:
1475
1546−1550
Ac ce pt e
d
1473
1476
Raja PB, Fadaeinasab M, Qureshi AK, Rahim AA, Osman H, Litaudon M, Awang K (2013)
1477
Evaluation of green corrosion inhibition by alkaloid extracts of Ochrosia oppositifolia
1478
and Isoreserpiline against mild steel in 1 M HCl medium. Industrial & Engineering
1479
Chemistry Research 52: 10582–10593
1480
Rajendran S, Joany RM, Apparao BV, Palaniswamy N (2002) Corrosion inhibition by
1481
carboxymethyl cellulose-1-hydroxyethane-1, 1-diphosphonic acid-Zn2+ system. Bulletin
1482
of Electrochemistry 18: 25-28
1483 1484
Rajendran S, Sridevi SP, Anthony N, John AA, Sundearavadivelu M (2005) Corrosion behaviour of carbon steel in polyvinyl alcohol. Anti-Corrosive Methods and Materials 52:102–107
1485
Rajeswari V, Kesavan D, Gopiramanb M, Viswanathamurthi P (2013) Physicochemical studies
1486
of glucose, gellan gum, and hydroxypropyl cellulose—Inhibition of cast iron corrosion.
1487
Carbohydrate Polymers 95: 288–294 52
Page 52 of 74
1488
Ridhwan AM, Rahim AA, Shah AM (2012) Synergistic effect of halide ions on the corrosion
1489
inhibition of mild steel in hydrochloric acid using mangrove tannin. International Journal
1490
of Electrochemical Science 7: 8091–8104
1492
Rosliza R and Nik WBW (2010) Improvement of corrosion resistance of AA6061 alloy by tapioca starch in seawater. Current Applied Physics 10: 221–229
ip t
1491
Roy P, Karfa P, Adhikari U, Sukul D (2014) Corrosion inhibition of mild steel in acidic medium
1494
by polyacrylamide grafted Guar gum with various grafting percentage: Effect of
1495
intramolecular synergism. Corrosion Science 88: 246–253
cr
1493
Saidia N, Elmsellema H, Ramdania M, Chetouania A, Azzaouib K, Yousfia F, Aounitia A,
1497
Hammouti B (2015) Using pectin extract as eco-friendly inhibitor for steel corrosion in 1
1498
M HCl media. Der PharmaChemica, 7(5):87-94
us
1496
Sakai T, Sakamoto T, Hallaert J, Vandamme EJ (1993) Pectin, Pectinase, and Protopectinase:
1500
Production, Properties, and Applications. Advances in Applied Microbiology 39: 213–
1501
294
M
an
1499
Sangeetha Y, Meenakshi S, Sundaram CS (2015a) Corrosion mitigation of N-(2-hydroxy-3-
1503
trimethyl ammonium)propyl chitosan chloride as inhibitor on mild steel. International
1504
Journal of Biological Macromolecules 72: 1244–1249
d
1502
Sangeetha Y, Meenakshi S, Sundaram C (2016) Interactions at the mild steel acid solution
1506
interface in the presence of O-fumaryl-chitosan: Electrochemical and surface studies.
1507
Carbohydrate Polymers, 136: 38 – 45.
Ac ce pt e
1505
1508
Sangeetha Y, Meenakshi S, Sundaram CS (2016) Investigation of corrosion inhibitory effect of
1509
hydroxyl propyl alginate on mild steel in acidic media. Journal of Applied Polymer
1510
Science; DOI: 10.1002/APP.43004
1511
Sasikumar Y, Adekunle AS, Olasunkanmi LO, Bahadur I, Baskar R, Kabanda MM, Obot IB,
1512
Ebenso EE (2015) Experimental, quantum chemical and Monte Carlo simulation studies
1513
on the corrosion inhibition of some alkyl imidazolium ionic liquids containing
1514
tetrafluoroborate anion on mild steel in acidic medium. Journal of Molecular Liquids
1515
211: 105–118
1516 1517
Schweiger RG (1962) Acetyl Pectates and Their Reactivity with Polyvalent Metal Ions. Journal of Organic Chemistry 27: 1789
53
Page 53 of 74
1518
Shibad PR, Balachandra J (1976) Behaviour of titanium and its alloy with hydrofluoric acid in
1519
HCI and H2SO4 solutions with addition agents. Anti-Corrosion Methods and Materials
1520
23: 16–28 Smith AM (2001) The biosynthesis of starch granules. Biomacromolecules 2 (2): 335–41
1522
Solomon MM, Umoren SA, Udosoro II, Udoh AP (2010) Inhibitive and adsorption behaviour of
1523
carboxymethyl cellulose on mild steel corrosion in sulphuric acid solution. Corrosion
1524
Science 52: 1317–1325
ip t
1521
Sriram JG, Sadhir MH, Saranya M, Srinivasan A (2014) Novel Corrosion Inhibitors Based On
1526
Seaweeds for AA7075 Aircraft Aluminium Alloys. Chemical Science Review and Letters
1527
2: 402-407
1530 1531
us
Materials Science 3: 3995-4003
an
1529
Sugama T (1997) Oxidized potato-starch films as primer coatings of aluminium, Journal of
Sugama T, DuVall JE (1996) Polyorganosiloxane-grafted potato starch coatings for protecting aluminum from corrosion. Thin Solid Films 289: 39-48
M
1528
cr
1525
Suyanto, HDK, Ratih R, Leo SA (2015) Application chitosan derivatives as inhibitor corrosion
1533
on steel with fluidization method. Journal of Chemical and Pharmaceutical Research 7:
1534
260-267
1536
Talati JD, Modi RM (1976) Colloids as corrosion inhibitors for aluminium-copper alloy in
Ac ce pt e
1535
d
1532
sodium hydroxide. Anti-Corrosion Methods and Materials 23: 6─9
1537
Tang L, Li X, Mu G, Li L, Liu G (2006) Synergistic effect between 4-(2-pyridylazo) resorcin
1538
and chloride ion on the corrosion of cold rolled steel in 0.5 M sulfuric acid. Applied
1539
Surface Science 252: 6394–6401
1540 1541
Tawfik S.M (2015) Alginate surfactant derivatives as ecofriendly corrosion inhibitor for carbon steel in acidic environment. RSC Advances DOI: 10.1039/C5RA20340F
1542
Umoren SA, Obot IB, Ebenso EE, Okafor PC, Ogbobe O, Oguzie EE (2006) Gum arabic as a
1543
potential corrosion inhibitor for aluminium in alkaline medium and its adsorption
1544
characteristics. Anti-Corrosion Methods and Materials 53: 277–282
1545
Umoren SA, Ogbobe O, Ebenso EE (2006) Synergistic inhibition of aluminium corrosion in
1546
acidic medium by gum arabic and halide ions. Transactions of the SAEST (Society for
1547
Advancement of Electrochemical Science and Technology) 41: 74-81
54
Page 54 of 74
1548 1549
Umoren SA (2008) Inhibition of aluminium and mild steel corrosion in acidic medium using Gum Arabic. Cellulose 15:751–761 Umoren SA, Ogbobe O, Igwe IO, Ebenso EE (2008a) Inhibition of mild steel corrosion in acidic
1551
medium using synthetic and naturally occurring polymers and synergistic halide
1552
additives. Corrosion Science 50: 1998–2006
ip t
1550
Umoren SA, Obot IB, Ebenso EE, Obi-Egbedi N (2008b) Studies on the inhibitive effect of
1554
exudate gum from Dacroydes edulis on the acid corrosion of aluminium. Portugaliae
1555
Electrochimica Acta 26:199–209
cr
1553
Umoren SA, Eduok UM, Oguzie EE (2008c) Corrosion inhibition of mild steel in 1 M H2SO4 by
1557
polyvinyl pyrrolidone and synergistic iodide additives. Portugaliae Electrochimica Acta
1558
26: 533-546
us
1556
Umoren SA (2009) Synergistic Influence of gum arabic and iodide ion on the corrosion
1560
inhibition of aluminium in alkaline medium. Portugaliae Electrochimica Acta 27: 565-
1561
577
1563
M
1562
an
1559
Umoren SA., Obot IB, Obi-Egbedi NO (2009a) Raphia hookeri gum as a potential eco-friendly inhibitor for mild steel in sulfuric acid. Journal of Materials Science 44:274–279 Umoren SA, Obot IB, Ebenso EE, Obi-Egbedi NO (2009b) The Inhibition of aluminium
1565
corrosion in hydrochloric acid solution by exudate gum from Raphia hookeri.
1566
Desalination 247: 561–572
Ac ce pt e
d
1564
1567
Umoren SA, Ebenso EE (2009) Studies of the anti-corrosive effect of Raphia hookeri exudate
1568
gum-halide mixtures for aluminium corrosion in acidic medium. Pigment Resin
1569
Technology 37: 173–182
1570
Umoren SA, Ekanem UF (2010) Inhibition of mild steel corrosion in H2SO4 using exudate gum
1571
from Pachylobus edulis and synergistic potassium halide additives. Chemical
1572
Engineering Communications 197:1339–1356
1573
Umoren SA, Solomon MM, Udosoro II, Udoh AP (2010) Synergistic and antagonistic effects
1574
between halide ions and carboxymethyl cellulose for the corrosion inhibition of mild steel
1575
in sulphuric acid solution. Cellulose 17:635–648
1576
Umoren SA, Eduok UM, Solomon MM, Udoh AP (2011) Corrosion inhibition by leaves and
1577
stem extracts of Sida acuta for mild steel in 1 M H2SO4 solutions investigated by
1578
chemical and spectroscopic techniques. Arabian Journal of Chemistry, 55
Page 55 of 74
1579 1580 1581 1582
http://dx.doi.org/10.1016/j.arabjc.2011.03.008. Umoren SA, Banera MJ, Garcia TA, Gervasi CA, Mirıfico MV (2013) Inhibition of mild steel corrosion in HCl solution using chitosan. Cellulose 20: 2529 – 2545. Umoren SA, Eduok UM, Solomon MM (2014) Effect of polyvinylpyrrolidone–polyethylene glycol blends on the corrosion inhibition of aluminium in HCl solution. Pigment & Resin
1584
Technology 43: 299 – 313
ip t
1583
Umoren SA, Solomon MM (2015) Effect of halide ions on the corrosion inhibition efficiency of
1586
different organic species – A review. Journal of Industrial and Engineering Chemistry 21:
1587
81–100
us
cr
1585
Umoren S, Solomon MM, Ubon-Israel A, Eduok UM, Jonah AE (2015a) Comparative study of
1589
the corrosion inhibition efficacy of polypropylene glycol and poly (methacrylic acid) for
1590
mild steel in acid solution. Journal of Dispersion Science and Technology 36: 1721-1735
an
1588
Umoren SA, Obot IB, Madhankumar A, Gasem ZM (2015b) Performance evaluation of pectin as
1592
ecofriendly corrosion inhibitor for X60 pipeline steel in acid medium: Experimental and
1593
theoretical approaches. Carbohydrate Polymers 124: 280–291
1595
van de Velde F, DeRuiter GA (2005) Carrageenan: Polysaccharides. in: Biopolymers Online, Wiley-VCH Verlag GmbH & Co. KGaA, DOI: 10.1002/3527600035.bpol6009
d
1594
M
1591
Vathsala K, Venkatesha TV, Praveen BM, Nayana KO (2010) Electrochemical generation of Zn-
1597
chitosan composite coating on mild steel and its corrosion studies. Engineering 2: 580-
1598
584
1599 1600
Ac ce pt e
1596
Verbeken D, Diercka S, Dewttinck K (2003) Exudate gums: occurrence, production and applications (A review). Applied Microbiology & Biotechnology 10:1354–1457
1601
Wang L, Zhang C, Xie H, Sun W, Chen X, Wang X, Yang Z, Liu G (2015) Calcium alginate gel
1602
capsules loaded with inhibitor for corrosion protection of downhole tube in oilfields.
1603
Corrosion Science 90: 296–304
1604 1605 1606 1607
Yan X, Zou C, Qin Y (2014) A new sight of water-soluble polyacrylamide modified by βcyclodextrin as corrosion inhibitor for X70 steel. Starch/Stärke 66: 968–975 Zaafarany I (2006) Inhibition of acidic corrosion of iron by some carrageenan compounds. Current World Environment, 1(2): 101-108
56
Page 56 of 74
1608
Zaafarany I (2012) Corrosion Inhibition of aluminum in aqueous alkaline solutions by alginate
1609
and pectate water-soluble natural polymer anionic polyelectrolytes. Portugaliae
1610
Electrochimica Acta, 30: 419-426 Zaafarany IA, Khairou KS, Hassan RM (2009) Acid-catalysis of chromic acid oxidation of
1612
kappa-carrageenan polysaccharide in aqueous perchlorate solutions. Journal of Molecular
1613
Catalysis A: Chemical 302: 112–118
ip t
1611
Zheludkevich ML, Tedim J, Freire CSR., Fernandes SCM., Kallip S, Lisenkov A, Gandinia A,
1615
Ferreira MGS (2011) Self-healing protective coatings with ‘‘green’’ chitosan based pre-
1616
layer reservoir of corrosion inhibitor. Journal of Materials Chemistry 21: 4805–4812
1618
us
1617
cr
1614
Zou C, Yan X, Qin Y, Wang M, Liu Y (2014a) Inhibiting evaluation of b-Cyclodextrin-modified acrylamide polymer on alloy steel in sulfuric solution. Corrosion Science 85: 445–454 Zou C., Liu Y., Yan X., Qin Y., Wang M., Zhou L (2014b) Synthesis of bridged β-
1620
cyclodextrinepolyethylene glycol and evaluation of its inhibition performance in oilfield
1621
wastewater. Materials Chemistry and Physics 147: 521-527.
1623
M
1622
an
1619
1626 1627
Ac ce pt e
1625
d
1624
Table 1. Typical examples of inhibition systems involving exudate gums deployed for metal corrosion reduction in various aggressive media. Type of metal S/N Inhibitor system *Inhibitor type Corrosive media Method(s) of corros substrate Exudate gum 1. Gum Arabic ─ Aluminium/ mild 0.1 M H2SO4 Weight loss and t steel techniq 2. Gum Arabic in combination ─ Aluminium 0.1 M NaOH Weight loss and hyd with potassium iodide techniq 3. Gum Arabic ─ Aluminium 0.1 M NaOH Hydrogen evolution a techniq 4. Guar gum Mixed type Carbon steel (L-52 1 M H2SO4 Weight loss and po grade) containing NaCl polarization te 5. Exudate gum extracted from ─ Mild steel 0.1 M H2SO4 Weight loss, hydro Ficus glumosa thermometric techniq electron mic 6. Exudate gum extracted from ─ Aluminum alloy 1 M HCl GCMS and FTIR (d Ficus benjamina sheet the chemical compos exudate); weight l 7. Exudate gum extracted from ─ Zinc (A72357 0.1 M H2SO4 GCMS (determinatio 57
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─
Mild steel
9.
Exudate gum extracted from Acacia tree
Mixed type
Mild steel
10.
Exudate gum extracted from Ferula assa-foetida and Dorema ammoniacum
Mixed type
Mild steel
11.
Exudate gum extracted from Raphia hookeri Exudate gum extracted from Dacroydes edulis Polyacrylamide grafted guar gum
─
an
Aluminium (AA 1060 grade) Aluminium (AA 1060 grade) Mild steel
M
─ Mixed type
d
13.
ip t
Exudate gum extracted from Daniella olliverri
composition of the weight loss, hydroge thermometric techn electron mic 0.1 M HCl GCMS and FTIR (d the chemical compos exudate); weight l 0.5─2 M HCl and Weight loss, hydroge Potentiodynamic H2SO4 techniques; X-ray spectroscopy, Fourier red spectroscopy electron mic 2 M HCl Electrochemical spectroscopy, Pot polarization, scan microscopy; quan calculations (by se method/Austin Mode 0.1 M HCl Weight loss and t techniq 2 M HCl Weight loss and t metho 1 M HCl Weight loss techn transform infra-red; impedance spe Potentiodynamic scanning electron 1 M HCl Potentiodynamic p Electrochemical spectroscopy; Fourier red spectro 15% HCl Weight loss te Electrochemical spectroscopy, Pot polarization; scan microsc 0.5 M H2SO4 Weight loss, pote polarization and el impedance spectros electron mic
us
8.
12.
14.
Gum Arabic
Mixed type
15.
Xanthan gum and Xanthan gum-polyacrylamide conjugate
Mixed type
Mild steel
16.
Polyacrylamide grafted with Okra mucilage
Mixed but predominantly cathodic
Mild steel
Ac ce pt e
1628 1629 1630 1631 1632
grade)
cr
Acacia sieberiana
API 5L X42 pipeline steel
Metal corrosion inhibition by exudate gums are generally attributed to the adsorption of their chemical constituents on the metal surface via formation of protective film. *An inhibitor type for a metal substrate in a solution of an electrolyte is known on the basis of its Tafel behavior (by monitoring the effect of its presence on the anodic and/or cathodic reactions using the electrochemical potentiodynamic polarization technique that involves the application of potential within a given range versus the open-circuit potential at a given scan rate).
1633 1634 1635 58
Page 58 of 74
1636 Table 2. Typical examples of inhibition systems involving substituted cellulose and starch deployed for metal corrosion reduction in various aggressive media. S/N
Carboxymethyl cellulose and Hydroxyethyl cellulose Carboxymethyl cellulose
─
Type of metal substrate/ corrosive media
Method(s) of corrosion monitoring
cr
Mild steel/2 M H2SO4
Weight loss, hydrogen evolution and thermometric techniques.
an
Sodium carboxymethyl cellulose
Mixed type
Mild steel/1 M HCl
3.
Carboxymethyl cellulose in combination with potassium halides (KCl, KBr, KI)
─
Mild steel (AISI 1005 grade)/ 2 M H2SO4
4.
Carboxymethyl cellulose [Authors also studied poly(vinyl alcohol), poly(acrylic acid), sodium polyacrylate, poly-(ethylene glycol), pectin] Carboxymethyl cellulose in combination with 1hydroxyethanole-1,1diphosphonic acid─Zn2+ system.
Slightly cathodic at higher carboxymethyl cellulose concentrations Mixed type
Planar cadmium disc electrode/ 0.5 M HCl
Potentiodynamic polarization and electrochemical impedance spectroscopy.
Mild steel/ Neutral aqueous environment containing 60 ppm Cl─
Weight loss technique; [protective film has been analyzed by X ray diffraction (XRD) and FTIR]; Potentiodynamic polarization technique.
d
M
2.
5.
Reason for corrosi corrosion reduction is following re
ip t
*Inhibitor type
us
1.
Inhibitor system
Ac ce pt e
1637 1638
Weight loss techniques; potentiodynamic polarization, linear polarization resistance and electrochemical impedance spectroscopy. Weight loss and hydrogen evolution techniques.
Authors attributed chem via inherent functional g ─COOH) on the metal s reason for corrosion inh pointed out that the prot ─COOH at the carbony molecular adsorption on metal surface by electro Molecular adsorption on via inherent functional g
Inhibitor molecular a metal surface; Halide i both antagonism (Cl─ a synergism towards the of Carboxymethyl cellu Molecular adsorption on
Formation of prot (Zn(OH)2, Fe2+─HEDP ─CMC complex) films the metal substrate; co Diffraction and Fourie red spectroscopy
59
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Carboxymethyl cellulose ─Zn2+ binary system.
Mixed type; but dominantly anodic
Carbon steel/ Neutral chlorine ion (120 ppm Cl─) saturated media
7.
Carboxymethyl cellulose─Zn2+ binary system.
Mixed type; but predominantly cathodic.
Aluminium/ Ground water at pH 11
8.
Carboxymethyl cellulose─Zn2+ system.
─
Carbon steel/ Ground water at pH 11
9.
Hydroxypropyl cellulose [Authors also studied glucose and gellan gum] in combination with potassium iodide
Mixed type
cr us
Formation of protective surface (confirmed with microscope and atomic microscopy).
an
Rate of metal degradatio an inhibition synergism CMC; and also the form protective film on the m (confirmed with scannin microscopy). Cast iron/ 1 M Weight loss and Molecular adsorption on HCl potentiodynamic confirmed by Wide diffraction, Fourier tr polarization techniques, spectroscopy and sc electrochemical microscope; potas impedance demonstrated both spectroscopy. synergism towards the of Hydroxypropyl cellul Carbon steel (1018 Electrochemical Molecular adsorption on grade)/ 3.5% NaCl impedance (confirmed with sc spectroscopy, microscopy/ Energy potentiodynamic spectroscopy). polarization and electrochemical frequency modulation. Authors further explained inhibitor molecular adsorption and corrosion mechanism with DMol3 quantum chemical calculations. Mild steel/ 0.5 M Weight loss and Metal corrosion inhibit H2SO4 potentiodynamic to Hydroxyethyl cel polarization adsorption and elastic
M d
11.
Ac ce pt e
10.
Inhibition was attribut type protective film o confirmed by AFM; confirmed to be mad complex and Zn(OH)2 u
ip t
6.
technique. Weight loss and potentiodynamic polarization techniques, electrochemical impedance spectroscopy. Weight loss and potentiodynamic polarization techniques, electrochemical impedance spectroscopy. Weight loss technique and electrochemical impedance spectroscopy.
Hydroxyethyl cellulose
Mixed type
Hydroxyethyl cellulose in combination with potassium iodide
Mixed type
60
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techniques; electrochemical impedance spectroscopy
Hydroxyethyl cellulose
Mixed type
13.
Hydroxyethyl cellulose
Mixed type
Mild steel/ 1 and 1.5 M HCl; 0.5 M H2SO4
14.
15.
16.
Ac ce pt e
d
M
12.
an
us
cr
ip t
Quantum chemical calculations using the density functional theory (DFT) was employed to determine the relationship between molecular structure and inhibition efficiency. Weight loss technique; Potentiodynamic polarization and electrochemical impedance spectroscopy. Potentiodynamic polarization and electrochemical impedance spectroscopy. Potentiostatic polarization, electrochemical impedance spectroscopy, cyclic voltammetry and potentiodynamic anodic polarization techniques.
the steel substrate due this compound in th Potassium iodide enhan performance of the syste charged steel substrate inhibitor.
Methyl cellulose
Starch Starch in combination with 2,6-diphenyl-3methylpiperidin-4-one
Starch in combination with sodium dodecyl sulfate and
Cylindrical zinc substrate (Zinccarbon battery)/ 26% NH4Cl
Anodic
aluminum and aluminum silicon alloys/ 0.1 M NaOH
Mixed type
Mild steel/ 1 N HCl
Mixed type but predominantly 61
Mild steel/ 0.1M H SO
Weight loss measurements; Electrochemical Impedance Spectroscopy; Potentiodynamic polarization. Weight loss and potentiodynamic
Inhibitor molecular a metal surface.
Inhibitor molecular a metal surface (confirm transform Infra-red s scanning electron micro
Inhibitor molecular ads presence of methyl cellu of alloys.
Both compounds synerg steel corrosion by co adsorption at the metal claims of the formation confirmed with Fourie red spectroscopy).
Both natural and syn synergistically inhibited
Page 61 of 74
predominantly anodic
H2SO4
potentiodynamic polarization.
─
XC 35 carbon steel/ Alkaline 200 mg/l NaCl
Electrochemical Impedance Spectroscopy.
synergistically inhibited combine molecular a metal surface. Inhibitor molecular ads presence of starch at th (confirmed with microscopy).
ip t
17.
sodium dodecyl sulfate and cetyl trimethyl ammonium bromide Activated and carboxymethylated starch cassava starch.
cr
Corrosion inhibition in concentration of starch carboxymethylated star performed inhibitor d substitution of its active AA6061 alloy/ Gravimetric, Physical coverage as w seawater potentiodynamic adsorption at the metal s polarization, with scanning electr linear Theoretical approach polarization inhibition was also resistance and correlating inhibiting electrochemical molecular structure. impedance spectroscopy. Cold rolled steel/ 1 Weight loss, Improved protection fr M H2SO4 potentiodynamic is due to synergy polarization, compounds by com electrochemical adsorption at the metal s impedance with scanning electron m spectroscopy.
Tapioca starch
Mixed type
19.
Acryl amide grafted cassava starch
20.
Polyorganosiloxane-grafted potato starch coatings
Mixed type though predominantly anodic and cathodic at lower and higher temperatures, respectively. ─
21.
Cerium (IV) ammonium nitrate modified potatostarch
M
d
1640
Ac ce pt e
1639
an
us
18.
─
Aluminium/ neutral electrolyte
EIS and saltspray resistance for 288 h 6061─T6 Salt-spray tests, aluminium/ neutral EIS and surface electrolyte analytical techniques (FTIR and XPS).
Improved protection w polyorganosiloxane poly polysaccharide coated o Improved protective p composite was attribute of cerium-bridged carbo by carboxylate function ions at the metal/coating
1641 1642 1643
62
Page 62 of 74
1644 1645 1646
ip t
1647 1648
cr
1649
us
1650 1651
Pectic acid/Pectin/Pectate Commercial pectin extracted Mixed type; but from apple dominantly cathodic.
X60 pipeline steel/ 0.5 M HCl
Weight loss and Corrosion inhibition potentiodynamic attributed to the adso polarization later formation of pro techniques, film on the metal sub electrochemical (confirmed by scanni impedance microscopy, Fourier spectroscopy. infra-red spectroscop contact angle measur Quantum chemical calculation (density functional theory (DFT)) results provide useful insights into the active sites and reactivity parameters governing the corrosion inhibition with pectin. Weight loss technique Corrosion inhibition was attributed to its a on the metal surface, forming protective fi confirmed by scannin microscopy. Weight loss and Corrosion inhibition potentiodynamic by geometric blockin polarization chemisorbed inhibitiv
d
1.
Inhibitor system
Reason for cor Method(s) of inhibition/ corrosion corrosion monitoring is attributed to the reason(s)
Type of metal substrate/ corrosive media
*Inhibitor type
M
S/N
an
Table 3. Typical examples of inhibition systems (involving pectic acid/pectin/pectates, chitosan and carrageenan) deployed for metal corrosion reduction in various aggressive media.
Ac ce pt e
1652 1653
2.
Pectin extracted from citrus peel
─
Aluminium/ 0.5─2 M HCl
3.
Pectin extracted from fresh lemon peel
Mixed type
Mild steel/ 1 M HCl 63
Page 63 of 74
Mixed type; but dominantly cathodic
Tin/ 2% NaCl, 1% acetic acid and 0.5% citric acid solution
cr
Pectin extracted from tomato waste
d
M
an
us
4.
chemisorbed inhibitiv Complex-type specie metal surface. These pectin─Fe2+ ion com formed during the co reaction (confirmed w spectroscopic (UV/V scanning electron mi analyses). Nuclear magnetic Inhibitor molecular resonance, Fourier on the metal surface. transform infra-red spectroscopic techniques were employed to characterize the pectin extracted and compared with a standard.
ip t
polarization techniques, electrochemical impedance spectroscopy.
Pectin extracted from cladodes of Opuntia ficus indica
Mixed type; but dominantly cathodic
Mild steel/ 1 M HCl
6.
Pectin [propyl phosphonic acid and Zn2+]
Mixed type
Carbon steel/ 60 ppm chloride solution
Ac ce pt e
5.
Electrochemical impedance spectroscopy and potentiodynamic polarization techniques were employed for the corrosion test. Weight loss, Adsorption of the inh potentiodynamic organic matter on the polarization surface; and the form techniques, protective film at the electrochemical solution interface. impedance spectroscopy. Weight loss, Corrosion inhibition potentiodynamic attributed to the form polarization protective film on the techniques, the carbon steel in th electrochemical aqueous medium; Sy impedance inhibition due to the spectroscopy. pectin, along with pr phosphonic acid and (confirmed with Four transform infrared sp atomic force microsc scanning electron mi and X-ray photoelect spectroscopy).
64
Page 64 of 74
Tin/ Neutral NaCl solution
8.
Pectin-g-polyacrylamide and Pectin-g-polyacrylic acid grafted polymers.
Mixed type; but dominantly cathodic
Mild steel/ 3.5% NaCl
an M d 10.
Ac ce pt e
9.
ip t
Cathodic type
cr
Pectin─ascorbic acid binary system
us
7.
Authors suggested th protective film must consisted of [Fe3+)/F propyl phosphonic ac complex, Zn(OH)2, a hydroxides and oxide Weight loss and The inhibitory effect potentiodynamic inhibitor system was polarization to the formation of p techniques. complex at the tin/so interface. Pectin-gInhibition was due th polyacrylamide and of protective film on Pectin-g-polyacrylic surface (confirmed w acid grafted polymers transform Infra-red s were synthesized from and scanning electron pectin, acrylamide, microscopy. and acrylic acid as precursors.
Pectate (with alginate) anionic polyelectrolytes
─
Aluminium/ 4 M NaOH
Sodium pectate (with sodium alginate)
─
Aluminium/ 4 M NaOH
Characterization of the synthesized grafted polymer: Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyser (TGA), and scanning electron microscopy (SEM). Corrosion test: Potentiodynamic polarization techniques, electrochemical impedance spectroscopy , and then surface analytical evaluations. Weight loss and hydrogen evolution techniques.
Weight loss and hydrogen evolution techniques.
Corrosion inhibition attributed the chemic adsorption via hydrox of the polymer anion polyelectrolytes form between the polymer metal surface. Same as Zaafaran
65
Page 65 of 74
Pectate anionic polyelectrolyte
─
Aluminium/ 1 M HCl
12.
Calcium alginate gel capsules loaded with Imidazoline quaternary ammonium salt
-
P110 steel/ CO2 saturated 3.5 wt % NaCl
Mixed type
cr
Chitosan
us
14.
Mild steel/ 0.1 M Weight loss, HCl potentiodynamic polarization techniques, electrochemical impedance spectroscopy. Copper/ 0.5 M Weight loss, HCl potentiodynamic polarization techniques, electrochemical impedance spectroscopy and electrochemical frequency modulation techniques.
an
Mixed type
16.
Ac ce pt e
d
M
13.
Chitosan and substituted/modified chitosans Chitosan
15.
Same as Zaafaran
Improved corrosion i was attributed to the release of the imidaz inhibitor at the metal interface (surface ads was confirmed with s electron microscopy)
ip t
11.
techniques. Weight loss and hydrogen evolution techniques. Ultraviolet–visible spectrophotometry, scanning electron microscopy, electrochemical impedance spectroscopy.
Carboxymethyl chitosan─Cu2+
Mixed type
Acetyl─thiourea─chitosan conjugate polymer
Mixed type
Mild steel/ 1 M HCl
Quantum chemical calculations was also used to correlate the corrosion inhibition with the molecular structure of chitosan. Weight loss, potentiodynamic polarization techniques, electrochemical impedance spectroscopy.
Mild steel/ 0.5 M Potentiodynamic H2SO4 polarization, electrochemical impedance spectroscopy.
Chemical adsorption on the metal surface concluded as the cau corrosion inhibition ( with surface analytic techniques).
Inhibition was due th of protective film on surface (confirmed w transform Infra-red s and scanning electron microscopy.
Corrosion inhibition steel in the presence mixture was attribute molecular adsorption chitosan, and its inhi mechanism was furth investigated with conductometry. Scanning electron mi was deployed to stud surface morphology o substrate, in terms of prevalence of deep lo and the formation of
66
Page 66 of 74
Chitosan─crotonaldehyde schiff’s base
Mixed type
AZ91E alloy/ Artificial sea water
─
Galvanized steel/ 3 wt% NaCl
Heptanoate anions encapsulated into a chitosan─modified beidellite coating
19.
Synthesized methyl acrylate grafted and triethylene tetramine/ethylene diamine chitosan copolymers
Cathodic type
20.
Thiocarbohydrazide graft chitosan
Mixed type
The improved corros inhibition for this cla coating was attribute leaching of hepatano Diffuse reflectance the metal/coating inte infrared Fourier thereby preventing th passage of corrosive transform ions towards the met spectroscopy (DRIFTS), TG coupled MS and XRD techniques. Carbon steel Weight loss, Corrosion inhibition attributed to the dens (Q235-grade)/ potentiodynamic 5% HCl polarization “sustained-release” n technique, film on the electrode electrochemical (confirmed by scanni impedance microscopy). spectroscopy. 304 steel/ Copper Charaterization of the Corrosion inhibition sheets/ 2% acetic inhibitor: Fourier attributed to the form acid transform infrared protective film forme spectroscopy, steel surface (confirm scanning electron mi elemental analysis, thermal gravity analysis and differential scanning calorimetry,
22.
M d
Ac ce pt e
21.
Thiosemicarbazide and thiocarbohydrazide modified chitosan derivatives β-Cyclodextrin modified natural chitosan
an
us
cr
18.
Potentiodynamic polarization, electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy.
ip t
17.
and the formation of film, in the absence a presence of inhibitor respectively. Corrosion inhibition attributed to inhibitor adsorption at the met
Mixed type
Same as Li et al. (2014a).
Mixed type
Low carbon steel/ 0.5 M HCl
Corrosion test: Potentiodynamic polarization. Same as Li et al. Same as Li et al. (201 (2014a). Weight loss, potentiodynamic polarization technique, electrochemical impedance spectroscopy.
Corrosion inhibition attributed to inhibitor adsorption and the fo protective film on the surface (confirmed w scanning electron mi
67
Page 67 of 74
Coating caused a huge displacement in both redox currents (Mixed-type).
Coated mild steel Fourier transform substrates/ 0.5 M infra-red H2SO4 spectroscopic and scanning electron microscopic techniques were employed for surface characterization of the film after electrodeposition and before corrosion test.
Corrosion inhibition attributed to the barri the passage of corros sulphate ions through protective film coatin metal surface (the su morphology of the co conducted with scann electron microscopy)
ip t
Chitosan deposited on mild steel substrates by solution electrophoresis via the application of a 15 V potential for 15 mins in a binary solution of chitosan/acetic acid with glutaraldehyde employed as the cross linker.
cr
23.
─
Aluminium alloy (AA 2024 grade)/ 0.05 M NaCl
M
Self-healing chitosan-based hybrid coating doped with cerium ions (corrosion inhibitors)
Ac ce pt e
d
24.
an
us
Corrosion test: Potentiodynamic polarization technique, electrochemical impedance spectroscopy. Optical microscopy, SVET, scanning electron microscopy/Energy dispersive X-ray and Fourier transform infra-red spectroscopic techniques were used in analyzing the undoped chitosan, and Ce-doped chitosan coating, before and after immersion in the solution of the electrolyte after different exposure period in 0.05 M NaCl solution.
25.
Chitosan/Zn composite coating electrodeposited on mild steel from zinc sulphate/sodium chloride binary solution
─
Mild steel/ 3.5 wt% NaCl
The encapsulated Cs as corrosion inhibitor bulk of the coating th enhancing the coatin mechanical and prote strength; and also to needed self-healing a specific microcrack s
Corrosion test: Electrochemical impedance spectroscopy. Weight loss and Corrosion inhibit potentiodynamic attributed to the polarization corrosive ions fro technique, through the prote coated on the me electrochemical impedance (confirmed with microsco spectroscopy; salt electron spray test. enhanced corrosion
68
Page 68 of 74
spray test.
Nanostructured chitosan/ZnO nanoparticles.
28.
Chitosan (shrimp shell waste) modified to as water soluble chitosan derivatives (2-N,Ndiethylbenzene ammonium chloride N-oxoethyl chitosan and 12ammonium chloride N-oxododecan chitosan)
Mild steel/ 1 M HCl
ip t
27.
Superior barrier characteristics were attributed to inhibition of both cathodic and anodic reactions (Mixed type) Cathodic type
Mild steel/ 0.1 N HCl
cr
Chitosan grafted nanogels.
Potentiodynamic polarization technique, electrochemical impedance spectroscopy.
30.
31.
Weight loss technique
d
Carbon steel/ 1 M HCl
Ac ce pt e
29.
─
M
an
us
26.
enhanced corrosion for this coating was as being due to the Zn2+ ions in the coati Potentiodynamic Corrosion inhibition polarization technique nanogel was attribute and electrochemical formation of active p impedance film carrying chitosa at the metal/solution spectroscopy. (confirmed with scan electron microscopy)
Carboxymethyl chitosan─benzaldehyde and carboxy methyl chitosan─urea─glutaric acid Mercaptobenzothiazolecontrolled release chitosan─based coating
─
Mild steel/ 2% NaCl
─
Aluminum alloy (AA 2024 grade)/ 0.05 M NaCl.
Electrochemical impedance spectroscopy
Chitosan coatings doped with cerium nitrate.
─
Aluminum alloy (AA 2024 grade)/ 0.05 M NaCl
Electrochemical impedance spectroscopy.
Fluidization
Improved metal protection was re compacted films in t of ZnO, and the fo nanofilms on s concluded as the prin of corrosion inhibiti and this was charact UV–vis, Fourier tran red spectroscopy diffraction and electron microscop Dispersive X-ray spe Corrosion inhibition reported as being init changes in the orient substituted groups an degree of overlapping hydrogen bonding wi same molecule.
Molecular adsorption chitosan on the meta was concluded as the of steel corrosion inh Corrosion inhibition attributed to molecul adsorption of the inh the metal surface. The improved corros inhibition for this cla coating was attribute leaching of mercaptobenzothiazo metal/coating interfa It was observed that t layer worked as a res cationic Ce3+ corrosio due to the complexat
69
Page 69 of 74
NaCl
Modified chitosan surfactants
Mixed type
API 65 pipeline steel/ 1 M HCl
Potentiodynamic polarization technique.
ip t
32.
due to the complexat with chitosan amino which prevented its uncontrollable and fa Corrosion inhibit attributed to adsorption of the in the metal surface.
N-(2-hydroxy-3-trimethyl ammonium)propyl chitosan chloride
Cathodic type
34.
O-fumaryl-chitosan
Mixed type
35.
Layer-by-layer chitosan/poly vinyl butyral coating
Mild steel/ 1 M HCl
M
an
33.
us
cr
Quantum chemical calculations was also used to correlate the corrosion inhibition with the molecular structure of chitosan. Weight loss and potentiodynamic polarization technique, electrochemical impedance spectroscopy.
35.
Ac ce pt e
d
Mild steel/ 1 M HCl
Carrageenan i─carrageenan
─
Weight loss and potentiodynamic polarization technique, electrochemical impedance spectroscopy.
Mild steel/ 0.3 M Electrochemical (EIS aerated NaCl and potentiodynamic) solution. and surface analytical (SEM and Raman spectroscopy) techniques.
Corrosion inhibition attributed to its adsor the metal surface, the forming protective fi (confirmed with Four transform infra-red s and scanning electron microscopy). Corrosion inhibition attributed to its adsor the metal surface, the forming protective fi (confirmed with Four transform infra-red s and scanning electron microscopy, X-ray di and Atomic force mi Barrier protection by coating was attribute chitosan middle layer sandwiched between butyral bilayers on th substrate, as well as t incorporating glutara within the chitosan la
Formation of passive (Fe3O4 and -Fe2O3 o
─
Aluminium/ 2 M HCl
Weight loss technique.
Scanning electron mi demonstrated smooth and relatively cohere adsorption layers of t on the metal surface solution.
70
Page 70 of 74
36.
Anodic type
Low carbon steel/ 1 M HCl
Weight loss and galvanostatic polarization techniques.
Corrosion inhibition attributed to the bloc steel surface by carra molecular adsorption
Neither cathode nor anode were predominantly polarized.
2.
Dextrin (in the presence of Fe+3,Cu+2 and Ni+2)
─
3.
Dextrin (including acacia, gelatin, agar agar, tragacanth and glue) Dextrin and Thiourea
─
Al/Cu alloy/ 0.1─1.0 N HCl
d
─
Titanium and titanium alloy/ 20% HC1 and H2SO4 Aluminiumcopper alloy/ 0.11 M NaOH Dextrin and Thiourea Additives on the Zinc Electroplated Mild Steel/ acid chloride electrolyte
β-Cyclodextrin-modified acrylamide polymer
Mixed type inhibitor system
X70 steel/ 0.5 M H2SO4
5.
β-cyclodextrinepolyethylene glycol
Mixed type inhibitor system
Q235 carbon steel/ 0.5 M HCl
6.
Polyacrylamide modified βcyclodextrin composite
Mixed type inhibitor system
X70 steel/ 0.5 M H2SO4
4.
cr
Dextrin Dextrin (including acacia, gelatin, agar and glue)
Method(s) of corrosion monitoring
Weight loss potentiodynamic polarization techniques
us
1.
Inhibitor type
an
Inhibitor system
M
S/N
Type of metal substrate/ corrosive media
ip t
Table 4. Examples of inhibition systems (involving dextrin, alginates and their derivatives) deployed for metal corrosion reduction in various aggressive media.
Ac ce pt e
1654 1655
i,k,µ─carrageenan
Reason for co inhibition/ corrosio is attributed to th reason(s
and Corrosion inhibition attributed to the ads the formation of pro on the metal.
Open circuit potential Corrosion inhibition measurements attributed to the ads the metal surface. Weight loss
Corrosion inhibition attributed to the ads the metal surface. Adhesion test and The electroplating p SEM/EDS revealed densely pa crystals on steel wit with different surfac morphology for eac period under study. combination with th additive demonstrat remarkable superior at the highest platin compared to the res matrices as examine EDS. Potentiodynamic Corrosion inhibition polarization, EIS and attributed to the mo SEM coupled with adsorption on the m EDS. EIS, potentiodynamic Corrosion inhibition polarization and attributed to the mo weight loss adsorption on the m techniques. Weight loss, Corrosion inhibition Potentiodynamic attributed to the mo polarization, EIS and adsorption on the m
71
Page 71 of 74
A1-3S in 0.2 N NaOH
Mixed type inhibitor system
aluminium alloy (AA 7075 grade) in 3.5 wt% NaCl
11.
Na alginate
12.
13.
Apple derived alginatewater-soluble natural polymer anionic polyelectrolytes (including pectate). Na alginate
14.
Alginate cationic surfactant
15.
Ca aginate gel loaded with imidazoline quaternary ammonium salts
Carbon steel corrosion/ 0.5 M HCl
─
Mixed corrosion inhibition system (but anodically controlled) Mixed corrosion inhibition system (but cathodically controlled) ─
Anodization/ anodic and cathodic polarization Potentiodynamic polarization technique
us
Na alginate extracts from a brown seaweed (Turbinaria ornate).
Ac ce pt e
10.
ip t
─
Weight loss, potentiodynamic polarization, EIS and SEM/EDS techniques.
cr
Alginate Na alginate
Carbon steel corrosion/ 0.5 M HCl
an
8.
9.
Q235A steel/CO2 saturated deionized water at 5.6 pH
Chitosan-grafted βcyclodextrin composite
Mixed type inhibitor system (but predominantly anodic than cathodic) Mixed type inhibitor system
M
Hydroxypropyl-bcyclodextrin/ octadecylamin supramolecular complex
d
7.
SEM. EIS and potentiodynamic polarization.
Pure aluminum/ 4 M NaOH
AZ31 alloy grade/ 3.5 wt% NaCl
Carbon steel/ 1 M HCl
P110 steel/ CO2saturated 3.5 wt.% NaCl
Corrosion inhibition attributed to the for passive inhibitor lay hydrophobic octade inherent in the supr complex at the meta Corrosion inhibition steel in the presence composite was also molecular adsorptio composite.
Molecular adsorptio
Authors attributed c inhibition to adsorp functional groups fo alginate extract; this confirmed with FTI spectroscopy. Molecular adsorptio metal surface.
Weight loss, potentiodynamic polarization, EIS and electrochemical frequency modulation (EFM). Gravimetric and Molecular adsorptio gasometric techniques. metal surface.
Polarization, EIS, SEM coupled EDS and FTIR spectroscopy
Authors attributed c inhibition to molecu adsorption and subs formation of compa (freshly generated m hydroxide) on the m Gravimetric, Molecular adsorptio electrochemical, EDX metal surface. and SEM techniques
Ultraviolet–visible spectrophotometry, SEM and EIS techniques.
The improved prote presence of this com attributed to the aut release of imidazoli inhibitors at the me interface. BaSO4 wa encapsulated with a
72
Page 72 of 74
Hydroxyl propyl alginate
Mixed type inhibitor system
Mild steel/1 M HCl
cr
1656
d
M
an
us
Table 5. Bioploymer-halide inhibition systems deployed for metal corrosion studies in various aggressive media. Type of metal Reason for corrosio Inhibitor system (halide S/N substrate/ Method(s) of corrosion monitoring in the presence of type) corrosive media (Halide eff Aluminium/ 0.1 Weight loss and hydrogen evolution Synergism (wi Gum Arabic in combination 1. M NaOH. techniques. with potassium iodide. 2. Carboxymethyl cellulose in Mild steel (AISI Weight loss and hydrogen evolution Inhibitor molecular a combination with potassium 1005 grade)/ 2 M techniques. the metal surface; halides (with KCl, KBr, KI). H2SO4. demonstrated both (Cl─ and Br─ ions) a towards the inhibitio Carboxymethyl cellul 3. Hydroxypropyl cellulose Cast iron/ 1 M Weight loss and potentiodynamic KI demonstrated bot polarization techniques, and synergism t [Authors also studied HCl. electrochemical impedance inhibition pote glucose and gellan gum] in combination with KI. spectroscopy. Hydroxypropyl cellul 4. Hydroxyethyl cellulose in Mild steel/ 0.5 M Weight loss and potentiodynamic Potassium iodide e polarization techniques; inhibition performa combination (with KI). H2SO4. electrochemical impedance system by bridging spectroscopy steel substrate and inhibitor (synergism). Quantum chemical calculations using the density functional theory (DFT) was employed to determine the relationship between molecular structure and inhibition efficiency. 5. Hydroxypropyl Aluminium (AA Weight loss and potentiodynamic Synergism (with KI). methylcellulose (with KI). 1060 type)/ 0.5 M polarization techniques, H2SO4. electrochemical impedance spectroscopy.
Ac ce pt e
1657 1658
Weight loss, electrochemical (Polarization and EIS) techniques, AFM, SEM and FTIR.
ip t
16.
encapsulated with a imidazoline compos to aid sinking and c retardation was wel Molecular adsorptio metal surface.
6.
Hydroxyethyl Cellulose
Quantum chemical calculations (by DFT) was also used to correlate the corrosion inhibition with the molecular structure of Hydroxypropyl methylcellulose. Aluminium (AA Same as Arukalam et al. (2014a). Synergism (with KI) 73
Page 73 of 74
9. 10.
11.
Hydrogen evolution and thermometric techniques. Weight loss, hydrogen evolution and thermometric techniques.
Exudate gum extracted from Pachylobus edulis (with KCl, KBr, KI).
Mild steel/ 2 M H2SO4.
Hydrogen evolution and thermometric Synergism (with KBr methods. Antagonism (with KC
Synergism (with KBr Antagonism (with KC Synergism (with KBr Antagonism (with KC
an
1660
Ac ce pt e
d
M
1661
1663
Synergism (with KI)
Aluminium/ 0.1 M NaOH. Aluminium/ 0.1 M HCl.
1659
1662
Synergism (with KI)
Gum Arabic (with KCl, KBr, KI). Raphia hookeri exudate gum (with KCl, KBr, KI).
cr
8.
Hydroxypropyl methylcellulose (with KI). Ethyl Hydroxyethyl Cellulose (with KI).
us
7.
1060 type) and Mild Steel/ 0.5 M H2SO4. Mild steel/ 0.5 M Same as Arukalam et al. (2014a). H2SO4. Mild steel/ 1 M Same as Arukalam et al. (2014a). H2SO4.
ip t
(with KI).
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S0144-8617(15)01216-3 http://dx.doi.org/doi:10.1016/j.carbpol.2015.12.038 CARP 10636
To appear in: Received date: Revised date: Accepted date:
19-9-2015 11-12-2015 15-12-2015
Please cite this article as: Umoren, S. A., and Eduok, U. M.,Application of carbohydrate polymers as corrosion inhibitors for metal substrates in different media: A review, Carbohydrate Polymers (2015), http://dx.doi.org/10.1016/j.carbpol.2015.12.038 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Highlights
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-Different carbohydrate polymers used as metal corrosion inhibitors have been discussed
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-Effect of halide ion additives on corrosion inhibition with carbohydrate polymers highlighted
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- Mechanism of inhibition action by the carbohydrate polymers highlighted
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- Theoretical approach to corrosion monitoring have been recommended for future studies
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Application of carbohydrate polymers as corrosion inhibitors for metal
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substrates in different media: A review
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Saviour A. Umoren1*, Ubong M. Eduok2
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Petroleum & Minerals, Dhahran 31261, Saudi Arabia.
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2
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Saudi Arabia
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Abstract
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Naturally occurring polysaccharides are biopolymers existing as products of biochemical
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processes of living systems. A wide variety of them have been employed for various material
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applications; as binders, coatings, drug delivery, corrosion inhibitors etc. This review describes
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the application of some green and benign carbohydrate biopolymers and their derivatives for
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inhibition of metal corrosion. Their modes and mechanisms of protection have also been
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described as directly related to their macromolecular weights, chemical composition and their
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unique molecular and electronic structures. For instance, cellulose and chitosan possess free
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amine and hydroxyl groups capable of metal ion chelation and their lone pairs of electrons are
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readily utilized for coordinate bonding at the metal/solution interface. Some of the carbohydrate
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Center of Research Excellence in Corrosion, Research Institute, King Fahd University of
Department of Chemistry, King Fahd University of Petroleum & Minerals, Dhahran 31261,
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polymers reviewed in this work is either pure or modified forms; their grafted systems and
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nanoparticle composites with multitude potentials for metal protection applications have also
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been highlighted. Few inhibitors grafted to introduce more compact structures with polar groups
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capable of increasing the total surface energy of the surface have also been mentioned. Exudate
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gums,
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substituted/modified chitosans, carrageenan, dextrin/ cyclodextrins and alginates have been
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elaborately reviewed, including the effects of halide additives on their anticorrosion
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performances. Aspects of computational/theoretical approach to corrosion monitoring have been
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recommended for future studies. This non-experimental approach to corrosion could foster a
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better understanding of the corrosion inhibition processes by correlating actual inhibition
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mechanisms with molecular structures of these carbohydrate polymers.
hydroxyethyl
cellulose,
starch,
pectin
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pectates,
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Keywords: Carbohydrate polymers; Green inhibitors; Polysaccharides; Corrosion; Metal substrates; Corrosion inhibition. * Corresponding author. Email: [email protected]; Tel.: +966-3-8609702; Fax: +966-38603996.
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carboxymethyl
Table of contents
Pages
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Introduction …………………………………………………………………………………. 2
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Green carbohydrate polymers application for metal protection…………………………….. 5
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Exudate gums……………………………………………………………………… 6
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Carboxymethyl and Hydroxyethyl cellulose……………………………………… 11
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Starch……………………………………………………………………………… 15
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Pectin and pectate………………………………………………………………….. 18
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Chitosan and substituted/modified chitosans……………………………………..
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Carrageenan………………………………………………………………………
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Greenness: A prerequisite requirement for selection of inhibitor compounds……. 3
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Dextrin and cyclodextrins……………………………………………………….
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Alginates…………………………………………………………………………
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Effect of halide ion additives on corrosion inhibition with carbohydrate polymers…….
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Future perspective: computational approach to corrosion evaluation…………………..
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Concluding remarks……………………………………………………………………..
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References……………………………………………………………………………….
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Introduction
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Metals corrode, and this electrochemical process has huge implication on their end-use and
65
consequently, the economics of maintenance and repairs for industrial applications. Several
66
forms of corrosion products and all possible reactions, including stable phases, are revealed in
67
the Pourbaix diagram of metals showing their susceptibility to corrosion depending on the pH.
68
The rate of metal corrosion is greatly influenced by substrate and surface chemistries as well as
69
some environmental influences (e.g. temperature, solution concentration (pH) etc.), and by
70
understanding these factors, adequate control method can be employed to revert its degradation
71
kinetics. By studying corrosion, researchers worldwide aim at discovering more reliable methods
72
and strategies of preventing, or at least minimizing its spontaneous dynamics. The use of
73
corrosion inhibitor compounds (single/multiple component, composites and blends etc.) is by far
74
one of the most applied corrosion control strategy in oil-fields. This operation is effective if the
75
adsorption mechanism(s) of the adsorbed inhibitor compound at the metal surface is rightly
76
defined. Generally, a common mechanism of action of most inhibitor compounds involves the
77
formation of passivation layer that prevents the passage of corrosive ions to the metal surface.
78
However, the effectiveness of this layer depends on the environment to which the compound has
79
been applied, the metal type as well as the fluid composition, quantity of water, and flow regime
80
(Gräfen et al. 2002). Normally in the field, these compounds are added in small concentrations to
81
coolants, hydraulic fluids, or any other fluid (liquid or gas) surrounding the metal substrate,
82
like alkylaminophosphates and zinc dithiophosphates in fuel oil. Phosphates, and other inorganic
83
substances (e.g. chromates, dichromate and arsenates) are known to have detrimental
84
environmental effect and man health impact, as such their usage is against modern safety
85
regulation for the industrial chemicals with severe criticism. Currently, there is an increasing
86
quest for limiting field applications involving toxic compounds, hence the search for greener
87
alternatives by reformulating the existing products or by identifying new chemistries for
88
developing safer products (Killaars and Finley 2001).
89
Greenness: A prerequisite requirement for selection of inhibitor compounds
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The general requirements of the selection of compounds are not limited to the chemical
91
structural pre-requite in Scheme 1, but must also include eco-friendliness and benignity (Umoren
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et al. 2009a; Okafor et al. 2008; Umoren et al 2008a; Obot et al. 2009; Umoren et al. 2011). In
93
recent times, owing to global interest on environment safety as well as the effect of impacting
94
industrial activities of man’s health and ecological balance, the use of toxic chemicals and
95
operations that emit them have been minimized. On this note, the inorganic inhibitors and some
96
of their hazardous organic counterparts, though effective for the reduction of metal corrosion at
97
lower concentration, are gradually replaced by greener substances. Generally, eco-friendly, or
98
simply green, corrosion formulations (inhibitors and coatings) are those chemical products that
99
meet the required reduced level of hazardous substance generation, and the processes involving
100
their usage are governed by sustainable chemistry without direct or indirect negative
101
environmental or health impacts. Since recommended anticorrosive coating systems are expected
102
to be green and purely cured granules/powders with very low volatile organic compound (VOC)
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content and without heavy metals, their inhibitor counterparts should also meet these green label
104
compliant standards. With the banning of chromates, corrosion control programs with greener
105
inhibitor compounds (chromate-free inhibitor formulations) in most oil field applications are
106
designed to effectively meet safety standards and also efficiently protect the targeted metal
107
substrates in their service environments. Health defects of chromates ranges from mild skin
108
allergic reactions and rashes to nasal bleeding; with arsenates, alteration of genetic material may
109
occur at higher dosages as well as nervous breakdown and cancer. The US National Institute for
110
Occupational safety and Health (NIOSH) have reduced the permissible exposure limit (PEL) for
111
arsenates and chromates to 0.002 and 0.05 milligrams per cubic meter of air, respectively.
112
(https://www.osha.gov/OshDoc/data_General_Facts/hexavalent_chromium.pdf;https://www.cdp
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h.ca.gov/programs/hesis/Documents/arsen2.pdf).
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Scheme 1. General pre-requite requirements for the selection of inhibitor compounds.
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Green carbohydrate polymers application for metal protection
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Organic corrosion inhibitors are generally used as replacements for inorganic compounds
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in the control of dissolution of the metals in aqueous media. Huge interest in this class of
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compounds has continued to grow in the last decade as naturally occurring and some synthetic
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biopolymers as well as their products meet the environmental requirements for safe product
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application with good corrosion inhibiting potential with infinitesimally small/reduced or zero
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pollution risk. Carbohydrate polymers are widely used as metal linings, and protective coatings.
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In corrosion inhibition, they represent a set of chemically stable, biodegradable and ecofriendly
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macromolecules with unique inhibiting strengths and mechanistic approaches to metal surface
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and bulk protection (Raja et al. 2013), with those extracted from natural sources (e.g. floral)
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regraded as low cost, renewable and readily available alternatives with essential and active 5
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ingredients responsible for the corrosion inhibition (Rahim et al. 2008). Generally, some of these
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carbohydrate biopolymers are relatively high molecular mass compounds with unique colloidal
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properties. Gum Arabic, for instance, readily forms low viscous suspensions and/or gels that can
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absorb water to a great extent when dissolved in appropriate solvent (Umoren et al. 2006). In
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solution, since the initial adsorption of inhibitor compounds could be affected by foreign surface
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active molecules, the potential of these polymers to actually reduce corrosion on the surface of a
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metal depends also on the adhesion of their moieties on the metal surface, either by physical
135
forces or chemical bond. To really understand the surface chemistry, the potential for inhibition
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of these compounds is explained in terms of their macromolecular weights, chemical
137
composition and the nature of the substrate’s surface. Some carbohydrate biopolymers normally
138
can restrict the rate of anodic dissolution by forming blankets on the metal surface or deters
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associated cathodic reactions by active site blocking which may largely also depend on nature
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(structural and chemical characteristics) of the adsorption layers formed (Eddy et al. 2009;
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Umoren et al 2014, 2015a). Scheme 2 shows possible mechanisms of inhibition with
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carbohydrate biopolymers (Arthur et al. 2013). Because of their versatility as non-metallic
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materials, some carbohydrate biopolymers are widely replacing corrosive resistance alloyed
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steels and nonferrous metals in many industrial applications with anticorrosion roles especially in
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protection of metal parts (e.g. screws) subjected to corrosion, erosion and cavitation (Klinov
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1962).
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Scheme 2. Possible mechanisms of inhibition with carbohydrate polymers.
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This unique class of polymers has been widely reported as corrosion inhibitors due to their
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enormous functional groups and their ability to complex with ions of metals at surfaces. By
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covering large surface areas of metals in aqueous media, these complexes virtually “blankets” 6
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the surface from attack by corrosive molecules and ions thereby offering the needed protection.
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The efficacy of carbohydrate biopolymers as inhibitors varies with their class depending on their
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molecular weights, cyclic rings as well as the availability of bond-forming groups (e.g. sulphonic
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acid groups) and abundance of centers of adsorption (e.g. heteroatoms) (Rajendran et al. 2005).
156
The presence of non-bonded/lone pairs of electrons (as well as pi electrons) on the molecules of
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these polymeric compounds allows for inhibitor-metal electron transfer with formation of bond
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whose strength is a function of the polarizability of the electron-donating group.
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Exudate gums
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Exudate gums are generally viscous tree (not excluding larger shrub) polysaccharides secretions
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that feel relatively moisten and/or sticky when wet and harden when they are dried. This unique
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physical property makes them useful oil and gas industrial adhesives and binders (Chaires-
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Martínez et al. 2008); and are used in the food industries as hydrocolloids due to their thickening
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and stabilizing properties (Douiare and Norton 2013). Gums are also widely used as
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microencapsulating agents in pharmaceuticals. Their solubility aids their usage as gelling and
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emulsifying agents as well. Depending on their compositions and floral sources, some gums
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possess faint to very pungent scents, and are generally soluble in water with gentle stirring in
168
small concentrations. It is not strange that some galactomannan gums are also found in few
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leguminous seed endosperm like locust bean and guar gums extracted from Ceratonia siliqua
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and Cyamopsis tetragonoloba, respectively (Busch et al. 2015). Researches involving various
171
gum types, both natural and synthetic, abound in the literature. Kim et al (2015) have
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investigated the solubility of three gum types from tapioca starch pastes, Gum arabic, k-
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carrageenan, gellan in water, alongside solvent effect on their humidity stability and mechanical
174
properties. The degradation of locust bean gum by ultrasonication at room temperature has been
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studied by Li and Feke (2015) with the rate of aqueous dissociation observed to be dependent on
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changes on molecular conformation of the gum as well as ionic conditions in the saline media
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used. Depending on the gum type, their intrinsic viscosities are widely studied by simple
178
rheological measurements. Gums are either natural or synthetic with varying viscosities and
179
compositions. Natural gums are classified based on their sources; they are either charged (ionic;
180
e.g. Agar extracted from seaweeds) or virtually uncharged (e.g. Guar gum from Guar bean seeds)
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polymers. Because of their unique chemical composition, gums from natural sources are
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effective corrosion inhibitors, and their evolution has greatly attracted attention considerably in
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the corrosion field. Gums of this class are greener, and renewable, without threat to the
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environment to which they are used (Umoren et al. 2006). Gum Arabic (GA) has been employed
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as corrosion inhibitor for some metal substrates, and available reports in the literature show that
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it protects metals to a great extent in aqueous acid and alkaline media. GA is water soluble, a
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dirty sticky and wet exudate extracted from Acacia tree (Leguminosae) sap material; and it is a
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mixture of some polysaccharides, sucrose, oligosaccharides, arbinogalactan and glucoproteins
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conceived to have the needed corrosion inhibition potential for metal substrate protection
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(Verbeken et al. 2003). The use of GA for aluminium and mild steel corrosion inhibitor in 1M
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sulphuric acid has been reported using the classical corrosion monitoring techniques (Umoren
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2008). Results from weight loss and thermometric techniques revealed that GA protected both
193
metals remarkably in the solution of the aerated acid with the inhibition efficiency (% η ) and the
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degree of surface coverage (θ) increasing with the concentration of GA. Physical and chemical
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adsorption mechanisms where proposed for MS and Al corrosion, respectively, in the presence
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of GA, and its spontaneous adsorption was approximated with Temkin and El-Awady et al.
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adsorption isotherm models. From the results obtained, GA was concluded as a more effective
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inhibitor for Al in the acid solution than mild steel. In alkaline (0.1 M NaOH) medium, the
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effectiveness of GA towards the corrosion inhibition of Al with and without iodide ion (as KI)
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additives has also been studied by Umoren (2009) and Umoren et al. (2006) at 30 and 40 oC,
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using hydrogen evolution and thermometric techniques. The corrosion inhibition of GA of Al in
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0.1 M NaOH was enhanced in the presence of the iodide ions due to synergistic effect. In the
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absence of KI, the inhibition of Al corrosion by GA was GA-concentration and temperature
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dependent, chemisorption mechanism was proposed for GA inhibition and its adsorption on Al
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substrates followed Langmuir and Freundlich adsorption isotherms.
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Guaran, or simply, Guar gum (GG), extracted from guar bean seed endosperm is another
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class of anticorrosion gum reported in the literature. Abdallah (2004) was the first to report its
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anticorrosion behaviour for carbon steel (L-52 grade) in 1 M H2SO4 containing NaCl as the
209
corrodent using Tafel polarization and weight loss techniques. His research results revealed GG
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as a mixed type inhibitor and values of inhibition efficiency (% η) increased with its
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concentration for both corrosion monitoring techniques. GG adsorption on L-52 substrate 8
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followed Langmuir adsorption isotherm and the pitting corrosion potential (Epit) was found to
213
vary with chloride ion concentration in the solution of the electrolyte. The applications of
214
exudate gums from plants sources are inexhaustive. Ameh’s group has reported the corrosion
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inhibition of gum exudates extracted from Ficus glumosa (GFG), Ficus Benjamina (GFB) and
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Acacia Sieberiana (GAS) for mild steel (MS), Al and Zn corrosion in 0.1 M H2SO4 and 1 M HCl
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(Ameh et al. 2012; Ameh and Eddy 2014; Eddy et al. 2014). Corrosion inhibition of GF for mild
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steel followed chemical adsorption mechanism and its adsorption was approximated with
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Langmuir adsorption model (Ameh et al. 2012). Using classical (weight loss, gasometric and
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thermometric) and surface analytical (scanning electron microscopy, SEM) techniques, authors
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claimed that the inhibiting properties of GFB could be largely attributed to a multiple adsorption
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of its chemical constituents (tannins, polysaccharides and glucoproteins characterized by Gas
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chromatography-Mass spectrometry (GC-MS) and Fourier transform infra-red spectroscopic
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(FTIR) techniques) on MS. Results followed the same trend for Al corrosion except that GFG
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adsorption on Al followed Frumkin and Dubinin-Radushkevich adsorption models (Eddy et al.
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2014). In sulphuric acid, zinc corrosion inhibition has also been studied using GAS with weight
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loss, thermometric and scanning electron microscopic techniques. GAS adsorption was
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approximated with Frumkin adsorption model, and its corrosion inhibition was found to be
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concentration and temperature dependent. Protective inhibitor layer on the surface of the metal
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substrate was revealed by SEM (Ameh and Eddy 2014). The chemical composition of gum
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exudate extracted from Daniella olliverri (GDO) has been determined using GCMS and FTIR to
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contain stearic and phthalate acids, sucrose, 2,6-dimethyl-4-nitrophenol and (E)-hexadec-9-enoic
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acid, and mild steel corrosion inhibition with GDO has been attributed to the adsorption of these
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compounds in 0.1 HCl (Eddy et al. 2012). In this study, authors investigated the adsorption and
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thermodynamic behaviour of GDO. While results from weight loss technique reveals a
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dependence of % η on the concentration of the exudate gum, its adsorption followed Langmuir
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adsorption isotherm and the inhibition of GDO was entirely by physical adsorption. Abu-Dalo et
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al. (2012) have also studied the inhibition effect of exudate gum extracted from Acacia trees
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(GAT) on MS corrosion in 0.5─2 M HCl and H2SO4. A concentration range of 0.1─0.6 mg/L
240
GAT was chosen for this study investigated using weight loss, hydrogen evolution, and
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electrochemical polarization, X-ray photoelectron spectroscopy (XPS), FTIR and SEM. For both
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acid corrodents, values of % η increased with inhibitor concentration but GAT inhibited
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corrosion in HCl more than H2SO4. The magnitude of % η was found to increase with external
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magnetic field in the presence of GAT also revealed to be a mixed type inhibitor. Steel corrosion
245
inhibition was attributed to the adsorption of GDO films on the surface of the metal substarte,
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and this was confirmed by results from FTIR, SEM and XPS. Investigated with classical and
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electrochemical techniques, Behpour et al. (2011) have reported the effects of exudate gum
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extracts from Ferula assa-foetida (GFF) and Dorema ammoniacum (GDA) on the corrosion
249
inhibition of MS corrosion in 2 M HCl solution. From Tafel curves, the authors concluded that
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the gums from both sources exhibited mixed type behaviour, and their adsorptions followed
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Langmuir isotherm. The magnitude of % η for steel in the solution of the acid electrolyte
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decreased with temperature for both gum resins. Inhibition of MS in the presence of GFF and
253
GDA was attributed to adsorption of components of the gums unto the metal substrate in the
254
corrodent; authors further performed quantum chemical calculations (by the semi-empirical
255
method/Austin Model (AM1) method) illustrating the adsorption processes of some of these
256
chemical components. SEM results revealed more surface pitting for MS substrate in the
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corrosion media containing GFF compared to GDA. Umoren et al. (2009a) have reported the
258
corrosion inhibition of Al in HCl in the presence of exudate gum from Raphia hookeri (GRH) at
259
30–60 oC. Results from weight loss and thermometric techniques show that the performance of
260
GRH improved with concentration and not with temperature. The physical adsorption
261
mechanism of GRH was approximated with Temkin adsorption isotherm and Kinetic–
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Thermodynamic Model of ElAwady et al. Al corrosion inhibition in the presence of GRH was
263
also attributed to the adsorption of its phytoconstituents. Biswas et al. (2015) have recently
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reported the inhibition effect of Xanthan exudate gum (Figure 1) and its graft polyacrylamide co-
265
polymer on MS corrosion in a very high concentration of acid (15% HCl) using chemical,
266
electrochemical and surface analytical techniques. For all the techniques used in this study,
267
values of % η increased with inhibitor concentration and the gum inhibited HCl induced
268
corrosion up to 92% inhibition efficiency ─ remarkably higher for this corrodent concertation
269
(15% HCl). The gum inhibition system acted as a mixed type inhibitor with molecular adsorption
270
at the metal surface initiating corrosion inhibition as confirmed by SEM analysis.
271
inhibition was revealed in the presence of polyacrylamide. Inhibition mechanism was elucidated
272
by means of thermodynamic and kinetic parameters and Xanthan gum adsorption and in
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combination with the copolymer on the metal surface followed Langmuir isotherm model.
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Improved
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Authors also correlated the experimental results with theoretical evaluation of associated
275
monomeric units using DFT in other to correlate inhibitor molecular structure with corrosion
276
inhibition. The inhibition performance of exudate gum extracted from Dacroydes edulis
277
(Umoren et al. 2008b) including exudate gum extracts from other floral sources investigated in
278
acidic and alkaline media are presented in Table 1, well as their corrosion behaviors for
279
respective metal substrates as reported in the literature. Apart from the unique chemical
280
constituents of individual gums from different sources, their solubility in aqueous media allows
281
for their wide application in corrosion inhibition. In aqueous media, dried gum matters adsorb
282
water and gradually swell, then gel, dissolving without agitation since the consist of complex
283
mixtures of polysaccharides. Peter et al. (2015) have recently given a comprehensive review of
284
some green gums for corrosion inhibition in order of class/source as well as their solubility in the
285
media. Table 1 features reviewed examples of other exudate gums reported in the literature
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Figure 1. Molecular structure (repeat unit) of Xanthan gum
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Carboxymethyl and Hydroxyethyl cellulose
Cellulose gum or simply, Carboxymethyl cellulose (CMC), is available as a sodium salt.
303
It has structural features of normal cellulose but with reactive carboxymethyl groups attached to
304
the hydroxyl groups of its cellulosic glucopyranyl moiety (Figure 2) (Peter et al. 2015).
305
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Figure 2. Molecular structure of Carboxymethyl cellulose [R=H or CH2COOH] and
307
Hydroxyethylcellulose [R=H or CH2CH2OH].
308
Derived from molecular cellulose, CMC could be one of the most abundant water-insoluble
309
polysaccharide used in similar industrial applications as exudate gums as they are better binders,
310
thickener, stabilizers for food and pharmaceutics (Solomon et al. 2010). CMC is widely
311
synthesized via alkali-assisted cellulose/chloroacetic acid reaction. In acid-induced corrosion
312
inhibition, the protective ability of CMC on steel is alleged to be due to a possible physisorption
313
of protonated CMC via molecular attraction with the negative charged mild electrode weakly
314
adsorbed by hydrated ions of electrolyte anions. CMC protonation occurs primarily at the
315
carbonyl group, normally forming polycations. The anti-corrosive properties of CMC have been
316
widely studied for mild steel in different acid solutions. Bayol et al (2008) have studied the
317
adsorptive behavior of CMC on MS in HCl solutions. Solomon et al (2010) and Umoren et al
318
(2010) have reported the inhibition potential of CMC for sulphuric acid corrosion of MS and also
319
the effects of synergism and antagonism of halide ions with CMC on corrosion inhibition. Table
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2 presents a list of substituted cellulosic compounds deployed for metal corrosion reduction in
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various aggressive media. In the work by Solomon et al. (2010), CMC have been assessed as a
322
green corrosion inhibitor for MS in 2 M H2SO4 by means of chemical techniques (weight loss,
323
hydrogen evolution and thermometric methods) at 30–60 oC. It was found that values of % η
324
greatly increased with CMC concentration and not with temperature. This physical mode of
325
adsorption followed Dubinin–Radushkevich and Langmuir adsorption isotherms; and the
326
inhibition mechanism was corroborated by experimentally derived activation/kinetic parameters.
327
Under the same experimental condition, authors further studied the effect of halide ions (Cl─,
328
Br─, and I─) additives on the performance of CMC in the acid medium (Umoren et al. 2010). The
329
corrosion inhibition by CMC was enhanced in the presence of Iodide ions, showing synergistic
330
effect, while the opposite was the case in the presence of chloride ions (antagonistic effect). The
331
magnitude of % η increased with immersion time of MS in the solution of the electrolyte
332
containing CMC and the iodide ions, and for all the other halide ions. Adsorption of the halide
333
ions followed similar isotherm model reported by Solomon et al. (2010), and the trend in
334
thermodynamic and kinetic parameters was explained accordingly with respect to each halide
335
ions. Bayol et al (2008) have reported similar findings in 1 M HCl using chemical (weight loss
336
method) and electrochemical (potentiodynamic polarization, linear polarization resistance (LPR),
337
and EIS) techniques. Inhibition of MS corrosion was found to be concertation dependent and
338
CMC was revealed as a mixed type inhibitor. The adsorption behavior reported in this study
339
follows the same trend as those previously reported for CMC (Solomon et al. 2010; Umoren et
340
al. 2010). SEM analysis was employed in studying the adsorption of CMC on the MS surface at
341
room temperature. The corrosion inhibition of a planar cadmium disc electrode in 0.5 M HCl in
342
the presence of CMC alongside five other polymers has been reported by Khairou and El-Sayed
343
(2003) using EIS and Tafel techniques. The inhibitive action of CMC affected only the
344
associated cathodic processes, indicating that it was a cathodic type inhibitor at higher
345
concentrations. CMC’s physical adsorption mode followed Temkin adsorption isotherm, and the
346
increase in values of % η with CMC concentration was attributed to molecular adsorption on the
347
cadmium disc surface. Using weight loss technique, Rajendran et al (2002) have also reported
348
the effect of CMC on the inhibition properties of 1-hydroxyethanole-1/1-diphosphonic
349
acid(HEDP)─Zn2+ binary system for MS in neutral chlorine ion (60 ppm Cl─) saturated media.
350
Values of % η for this system stood at 40% in the presence of 300 ppm HEDP and 10 ppm Zn2+
351
but increased to 80 % with the addition of 50 ppm CMC being the peak concentration. Inhibition
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of MS corrosion in this neutral medium was attributed to the adsorption of Zn(OH)2,
353
Fe2+─HEDP type and Fe2+ ─CMC complexes/films on the surface of the metal substrate. This
354
was confirmed with X ray diffraction (XRD) and FTIR. Another CMC─Zn2+ binary system in
355
neutral chlorine ion (120 ppm Cl─) saturated media has been studied for carbon steel corrosion
356
using weight loss, EIS and potentiodynamic polarization techniques (Antony et al. 2010). A % η
357
magnitude of 97 % was achieved at pH 7 in the presence of 250 ppm CMC and 100 ppm Zn2+,
358
though decreased at extremely low and high pH values. CMC─Zn2+ binary system displayed a
359
mixed type protection but dominantly anodic controlled. Like the work reported by Rajendran et
360
al. (2002), inhibition of MS corrosion in corrodent was attributed to the adsorption of a
361
Fe2+─CMC type complexes/protective films. This mechanism was confirmed by AC impedance
362
spectra and AFM studies. Values of % η magnitude as high as 95 and 98 % have also been
363
recorded in the presence of 250 ppm CMC (in combination with 25 and 50 ppm Zn2+,
364
respectively) for aluminuim and carbon steel substrates in ground water using chemical and
365
electrochemical techniques at pH 11 (Kalaivania et al. 2013; Manimaran et al. 2013). CMC in
366
the presence of Zn2+ synergistically inhibited steel corrosion, and inhibition was attributed to
367
Zn2+─CMC type complexes adsorption on metal surface characterized by SEM and AFM.
368
Corrosion inhibition was attributed to complex formation at the metal surface with polarization
369
result revealing that this process was predominantly cathodic. Rajeswari et al (2013) have
370
accessed the corrosion inhibition of Glucose, gellan gum, and hydroxypropyl cellulose for cast
371
iron in 1 M HCl by electrochemical and chemical methods. Corrosion inhibition was found to be
372
dependent of temperature and on the concentration of CMC (as well as that of other inhibitors).
373
Greater protection of cast iron was observed at increased inhibitor concentrations, lower
374
temperatures and prolonged immersion time. CMC was revealed as a mixed type inhibiting
375
system, while its adsorption followed Langmuir adsorption isotherm. Physical adsorption
376
mechanism was proposed form thermodynamic/kinetics parameters. Recently, the corrosion
377
inhibition of methyl cellulose in 0.1 M NaOH has been reported for aluminum and aluminum
378
silicon alloys investigated with electrochemical techniques (Eid et al. 2015). Results from
379
potentiodynamic polarization technique revealed that the inhibitive action of this compound
380
system predominantly affected the anodic process, indicating that the methyl cellulose was an
381
anodic type inhibitor. Authors attributed corrosion inhibition by this compound to adsorption via
382
multiple sites at the metal surface and the physical displacement of corrosive molecules across
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the metal/solution interface. Corrosion of the alloys was found to reduce with the concentration
384
of methyl cellulose but not with temperature. Cellulose’s physisorption at the metal surface
385
followed Langmuir adsorption isotherm, and kinetic/thermodynamic parameters were calculated
386
to further explain the mechanism of molecular adsorption.
ip t
383
Just like CMC, Hydroxyethylcellulose (HEC) is also derived from cellulose and used
388
primarily as a thickening, binding and gelling/stabilizing agents, and employed medically for
389
gastrointestinal fluids drug dissolution (https://en.wikipedia.org/wiki/Hydroxyethyl_cellulose).
390
The molecular structure of HEC is displayed in Figure 2. It has structural features similar to
391
CMC except for the replacement of the carboxymethyl with Hydroxyethyl groups still attached
392
to the hydroxyl groups of cellulosic glucopyranyl moiety in the same position. The success of
393
this carbohydrate polymer as a corrosion inhibitor in different media is drawn from these unique
394
functional groups (OH, COOH) on its cellulose backbone as well as its large molecular size
395
which ensures greater coverage of metal surface, deterring corrosive ions and molecules. El-
396
Haddad (2014) have reported a corrosion inhibition efficiency (% η ) in the magnitude of 97 %
397
for 5 mM HEC for 1018 grade carbon steel in 3.5 wt% NaCl solution. The anticorrosion
398
properties of this carbohydrate polymer were investigated using EIS, potentiodynamic
399
polarization and electrochemical frequency modulation (EFM). Electrochemical polarization
400
result revealed that HEC was a mixed-type inhibitor under this experimental condition, and
401
corrosion inhibition was induced by molecular adsorption on the steel surface confirmed by
402
SEM/ energy dispersive X-ray (EDX) analysis. Adsorption of HEC followed Langmuir
403
adsorption isotherm. Adsorption mechanism was supported by DMol3 quantum chemical
404
calculations as well as the computation of thermodynamic parameter and activation parameters.
405
Arukalam et al. (2015) have also reported similar study in an aerated 0.5 M H2SO4 solution using
406
both gravimetric and electrochemical techniques for mild steel corrosion. Corrosion inhibition
407
was found to increase with HEC concentration and with temperature. Potentiodynamic
408
polarization result revealed that HEC was a mixed type inhibitor while its adsorption on the steel
409
surface gradually decreased double layer capacitance (Cdl). Quantum chemical calculations with
410
density functional theory (DFT) were used to correlate the corrosion inhibition with HEC
411
molecular structure; inhibition was attributed to its adsorption behavior on the steel surface from
412
computed activation/kinetic parameters. HEC adsorption followed the Freundlich isotherm
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model. Corrosion inhibition was enhanced in the presence of KI in the solution of the acid
414
electrolyte. A corrosion inhibition of magnitude 69.62% and 58.15% in 1 and 1.5 M HCl,
415
respectively, has been reported by Arukalam (2012) for HEC using investigated by weight loss
416
technique. He found that HEC inhibited steel corrosion by increasing its concentration and
417
attributed inhibition to HEC molecular adsorption/elastic film formation on the steel substrate.
418
With the ban of mercury as corrosion inhibitor for zinc batteries due to its inherent toxicity and
419
environmental impact, researcher worldwide have focus more attention of organic compounds as
420
alternative (Qu 2006). Deyab (2015) has investigated the anticorrosion ability of HEC as
421
inhibitor for zinc-carbon battery using electrochemical techniques. HEC was found to inhibit
422
corrosion up to 92% for 300 ppm HEC at 30 oC. Tafel polarization revealed that HEC was a
423
mixed-type inhibitor, and its ability to inhibit Zn corrosion was attributed to its adsorption on the
424
Zn surface. Langmuir isotherm and thermodynamic parameters were employed in explaining
425
HEC adsorption (both physisorption and chemisorption), as well as FTIR and SEM for
426
characterization of the adsorbed carbohydrate biopolymeric film.
427
Starch
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Starch is a very large carbohydrate molecule with glycosidic bonds chemically
429
connecting its numerous glucose units. Normally, starch is consists of varying percentages by
430
weight of amylose (linear and helical) and amylopectin (branched) molecules depending on the
431
source from which it is derived (Brown and Poon 2005). Figure 3 displays the molecular
432
structures of starch. Starch biochemically provides the needed body energy to both higher
433
animals especially as it is being indirectly consumed from green plant sources. For these plants
434
to biosynthesize starch, series chemistry is involved: initially, adenosine triphosphate is
435
employed to convert glucose-phosphate to adenosine diphosphate-glucose via enzymatic
436
catalyzed oxidation using adenylyltransferase (Smith 2001). Virtually every human diet taken
437
daily contains starch in relatively enormous abundance (in yams, cassava, cereals, potatoes, oats,
438
peas, nuts, etc.). Starch is basically used as common food additive but also processed for use to
439
simple sugars, thickeners and glues for use in food and other industries. This white and tasteless
440
polysaccharide is sparingly soluble in warm water but completely undissolved in cold water and
441
alcoholic solvents.
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(a)
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Figure 3. Chemical structures of the amylose (a) and amylopectin (b) molecules of starch.
M
444
(b)
The use of molecular starch as corrosion inhibitor lacks wide application due to its
446
reduced solubility and surface adhesion strength. Some reports involving its application in acid
447
and neutral media for metal inhibition have been reported based on either physical or chemical
448
modification in other to improve its anticorrosion ability. The corrosion inhibiting ability of
449
starch can be linked to its unique molecular structures (Figure 3); bearing electron-rich hydroxyl
450
groups capable of coordinate bonding by filling the empty or partially occupied orbitals of iron
451
in ferrous substrates, hence corrosion inhibition. Brindha et al. (2015) have recently reported the
452
use of starch in combination with 2,6-diphenyl-3-methylpiperidin-4-one (DPMP) for mild steel
453
in 1 N HCl using chemical and electrochemical techniques. Steel corrosion rate was found to
454
reduce with the concentrations of these compounds, with both compounds synergistically
455
inhibited steel corrosion by combine molecular adsorption at the metal surface. The corrosion
456
inhibition by starch was greatly enhanced by the addition of 0.2mM DPMP independent of the
457
study temperature and the immersion time. Authors also attributed corrosion inhibition to the
458
formation of protective layer confirmed with Fourier transform Infra-red spectroscopy.
459
Experimental results were further collaborated with theoretical evaluation of the relationship of
460
molecular structure and corrosion inhibition at the B3LYP/631G(d) level. Results from weight
461
loss techniques were also collaborated with thermodynamic and adsorption isotherm models. In
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another work, starch in combination with sodium dodecyl sulfate and cetyltrimethyl ammonium
463
bromide have been studied using weight loss and potentiodynamic polarization techniques for
464
mild steel in 0.1 M H2SO4 (Mobin et al. 2011). Results from potentiodynamic polarization
465
revealed that these starch─surfactant conjugates were a mixed type system (though
466
predominantly anodic) and recorded 66.21% inhibition efficiency at 30 oC with only 200 ppm
467
starch. Just as reported by Brindha et al. (2015), author linked corrosion inhibition of both
468
systems to synergistic or combine molecular adsorption at the metal surface. Adsorption of these
469
conjugates at steel surface followed Langmuir adsorption isotherm at the range of temperature
470
and concentration under study. Physical adsorption phenomenon was proposed and results were
471
also collaborated with thermodynamic parameters to further explain the inhibition mechanism.
472
Bello et al. (2010) have studied the effect of physically (activated starch) and chemically
473
(carboxymethylated) modified starch cassava starch on the corrosion of XC 35 carbon steel in
474
alkaline 200 mg/l NaCl medium using electrochemical impedance spectroscopy. Inhibitor
475
molecular adsorption due to the presence of starch at the surface of steel was concluded as the
476
principal cause of corrosion inhibition; this was confirmed with atomic force microscopy in the
477
presence and absence of starch. Corrosion inhibition increased with the concentration of starch in
478
both cases, with carboxymethylated starch being the less performed inhibitor due to molecular
479
substitution of its active hydroxyl groups. To further explain reason for this unique behaviour by
480
carboxymethylated starch, the monomeric units were theoretically mapped (electrostatic
481
potential mapping) to observe possible ionic interactions at the molecular level. Malaysian
482
cassava (tapioca) starch has been employed in reducing the corrosion of AA6061 alloy in
483
seawater (sourced from Terengganu port, Malaysia) using chemical and electrochemical
484
techniques (Rosliza and Nik 2010). The presence of starch in the neutral corrodent was observed
485
to greatly reduce metal corrosion rate with huge effects on double layer capacitance and
486
corrosion current densities. Potentiodynamic polarization results revealed starch inhibition
487
process influenced both cathodic and anodic reactions. Corrosion reduction was inhibition
488
concentration─dependent. Corrosion inhibition was attributed to physical coverage as well as
489
molecular adsorption of starch at the metal surface; further confirmed with SEM analysis.
490
Theoretical approach to corrosion inhibition was also employed by authors in correlating
491
inhibiting mechanism with molecular structure. Adsorption of starch followed Langmuir
492
adsorption isotherm model. The effect of chemical grafting of acryl amide to cassava starch for
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corrosion inhibition of cold rolled steel in 1 M H2SO4 has been investigated using chemical and
494
electrochemical techniques (Li and Deng 2015). The improved protection from this grafted
495
conjugate was due to a synergy between both compounds by combine molecular adsorption at
496
the metal surface (with the adsorption further confirmed with SEM). From the Tafel behaviour,
497
this grafted starch─acryl amide conjugate was observed to be a mixed type inhibitor though
498
predominantly anodic and cathodic at lower and higher temperatures, respectively. Langmuir
499
adsorption isotherm was employed in fitting the adsorption of the inhibitor adsorbed at the metal
500
surface. The use of cerium (IV) ammonium nitrate modified potato-starch has been deployed as a
501
primer coatings (and polyurethane top-coat) of 6061─T6 aluminium with remarkable
502
anticorrosion properties in 0.5 N NaCl electrolyte at 25oC. Corrosion tests were conducted using
503
salt-spray tests, EIS and surface analytical techniques (FTIR and XPS). An improved protective
504
property of this composite was attributed to the formation of cerium-bridged carboxylate
505
complexes by carboxylate functional group with Ce4 ions at the metal/coating interface. The
506
coating was found to loss of adhesion on polyurethane compared to aluminium substrates
507
(Sugama, 1997).
508
Pectin
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Pectin is a complex set of heteropolysaccharide with molecular structure not restricted to
510
Figure 4. It is naturally abundant in cell walls of non-woody terrestrial plants and commercially
511
available as white or brownish powders/granules (depending of the methods of synthesis and
512
purification) (Keppler et al. 2006). In nature, the structure and composition of floral pectin
513
depend on the plant and even the plant parts; and during fruit ripening, pectin is reduced to
514
pectinesterase by pectinase (Equation 1). Pectic polysaccharides are abundant with galacturonic
515
acid.
516 517
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509
Pectin
pectinase
Pectinesterase
(1)
19
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ip t
518
Figure 4. Molecular structure of pectic acid
520
Pectic is commonly extracted from citrus and apples, and used as gelling and thickening agents
521
in food industries and as stabilizers in some confectionaries, as well as in drinks (Sakai et al.
522
1993). Since pectin normally increases the amount and viscosity of human stool, it is medically
523
used against some chronic cases of constipation and diarrhea. Like other polysaccharides enlisted
524
in this review for inhibition, pectin’s ability to reduce metal corrosion is drawn from its
525
chemistry. Pectin possess carboxylic (―COOH) and carboxymethyl (―COOCH3) functional
526
groups on its carbohydrate backbone making it a possible candidate compound for corrosion and
527
scaling reduction in different media (Chauhan et al. 2012). Pectin is a biodegradable, benign and
528
green corrosion inhibitor. We have recently reported the anticorrosion ability of pectin
529
(commercial pectin from apple) in our laboratory against X60 pipeline steel in HCl medium
530
using chemical and electrochemical techniques (Umoren et al. 2015b). The corrosion inhibition
531
efficiency (% η ) was found to be temperature and pectin concentration dependent; higher
532
magnitudes of % η were obtained at increased concentration of pectin (79% being the highest
533
recorded % η for 1000 ppm pectin) and temperature. Potentiodynamic polarization results
534
revealed pectin inhibition influenced both cathodic and anodic reactions, but dominantly
535
cathodic. Inhibition of X60 pipeline steel corrosion was attributed to adsorption of protective
536
pectin film on the metal surface, and this was further confirmed by SEM and water contact angle
537
measurements. Pectin adsorption followed Langmuir adsorption isotherm, and quantum chemical
538
calculations by DFT was employed to explain pectin’s adsorption-inhibition activity. Fares et al
539
(2012a) have studied the application of pectin (from citrus peel) for Al metal reduction in acidic
540
(0.5-2 M HCl) media. The magnitude of % η greater than 91% was attained for 8.0 g/L pectin at
541
10 oC and was observed to slowly decrease with temperature. Values of % η increased with
542
pectin concentration, and this was consequently reflected in corresponding values of activation
543
energy, enthalpy and entropy. Corrosion inhibition by pectin was attributed to its adsorption on
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the metal surface and this was confirmed by SEM analysis. Its adsorption in this acidic media
545
followed Langmuir isotherm. Fiori-Bimbi et al. (2015) have reported a multi-step acid extraction
546
of pectin from fresh lemon peel. The pectin extract was tested for anticorrosion ability for mild
547
steel in 1 M HCl using chemical and electrochemical methods. Mild steel corrosion was found to
548
reduce with the addition of pectin, and this continued as the temperature increased. Tafel results
549
revealed that pectin in this study is mixed-type inhibitor, and the reason for pectin inhibition was
550
due to geometric blocking effect caused by chemisorbed pectin─Fe2+ type complexes/species at
551
the metal/solution interface was confirmed by UV-spectroscopic analysis. Thermodynamics and
552
kinetics of adsorption were considered directly from the electrochemical results and the trend in
553
values further added insights into the mode of adsorption. The most recent pectin application for
554
corrosion protection is the work by Grassino et al (2016). Authors extracted pectin for the first
555
time using tomato (Lycopersicum esculentum) waste. Characterization of pectin after extraction
556
from this source proceeded with FTIR and nuclear magnetic resonance spectroscopy (NMRS)
557
analyses as well as colour and rheological determination. Results were compared to a
558
commercially available pectin standard. The extracted pectin was methoxy pectin type based on
559
the degree of esterification result (about 82%). The pectin extract was employed in studying tin
560
corrosion inhibition, and values of % η up to 73% was recorded at very low concentrations (4
561
g/L) using EIS and potentiodynamic polarization technique in 2% NaCl, 1% acetic acid and
562
0.5% citric acid solution. Tafel results revealed that pectin in this study is mixed-type inhibitor.
563
Pectin extract from Opuntia cladodes has also been employed in reducing mild steel corrosion in
564
1 M HCl using weight loss, potentiodynamic polarization and electrochemical impedance
565
spectroscopy techniques (Saidia et al. 2015). Corrosion inhibition increased with the pectin
566
concentration as revealed in variation in values of charge-transfer resistance and the reduction
567
double-layer capacitance. Pectin from this source acted as a mixed inhibitor with the highest % η
568
(96%) attained at 35 oC in the presence of 1g/l pectin. Pectin adsorption on the metallic substrate
569
followed Langmuir adsorption isotherm. Corrosion researches involving pectin inhibition is not
570
limited to acid-induced media, Prabakaran et al. (2015) have reported the synergistic pectin
571
inhibition with propyl phosphonic acid (PA) and Zn2+ ions in neutral medium for carbon steel
572
using chemical and electrochemical techniques. The presence of pectin in this study enhanced
573
the inhibition ability of the secondary components (PA and Zn2+ additives). Result from weight
574
loss technique revealed the optimum concentration of pectin, also showing that the presence of
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PA and Zn2+ synergistic improved corrosion protection by pectin. Potentiodynamic polarization
576
results revealed pectin inhibition influenced both cathodic and anodic reactions, and its
577
adsorption was marked with decrease in values of corrosion current density. Spectroscopic
578
(FTIR) and surface analytical (SEM, AFM, and XPS) techniques were employed to ascertain the
579
formation of pectin-type complexes/film on carbon steel. The corrosion inhibition of
580
pectin/ascorbic acid for tin in a neutral NaCl solution has been investigated (Nada et al. 1996).
581
Greater corrosion inhibitive effect for the binary system was observed at 200 ppm ascorbic acid
582
in combination with pectin at room temperature. The inhibitory effect for was due to the
583
formation of protective complex at the tin/solution interface. Results from potentiodynamic
584
polarization technique showed that the inhibitive action of the system affected only the cathodic
585
process, indicating that the pectin/ascorbic acid binary system was cathodic type inhibitor. Like
586
other carbohydrate biopolymers, pectin can be modified for many applications by carefully
587
altering its functional chemistry. With some anticorrosive polymers, structural modifications
588
improves the overall material performances by coupling single or multiple adsorption sites
589
capable of metal surface bonding and physically displacement of corrosive molecules like water
590
across the metal/solution interface. For mild steel inhibition in 3.5 wt% NaCl solution, pectin has
591
been grafted to polyacrylamide and polyacrylic acid, and the final materials protected steel more
592
than 85% (Geethanjali et al. 2014). The graft polymerization procedure slightly differs from
593
those reported by Mishra et al. (2007), except for modification in the final pH sensitive hydrogel
594
products with acrylic and acrylamide acids, and pectin still used as precursors. Polymer synthesis
595
and modification were followed by corrosion testing using EIS and Tafel polarization, and then
596
surface analytical evaluations (with FTIR and SEM) of the protective film formed on the steel
597
surface. Pectin modification products have also been reported as being used as antiscalants for
598
water treatment (Chauhan et al. 2012). This procedure was only designed to lower the molecular
599
weight of pectin by acid hydrolysis before grafting to acrylamide, thereby making copolymer-
600
graft with an antiscalant potential for carbonates, sulfates and phosphates. The outcome of the
601
scaling remediation experiment with the final hydrolyzed pectin-based grafted material was
602
outstanding against the carbonates precipitation, but this reaction was temperature and pH
603
independent. SEM and XRD techniques were employed in studying the precipitates’ crystal
604
morphology.
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605
Pectate Pectic acid (or polygalacturonic acid), like pectin is also present in plants, but dominantly
607
in ripened fruits (Sakai et al. 2003). Its derivatives, particularly pectates, obtained from structural
608
modification of pectin and pectic acid, could be better emulsifying and foaming agents for food
609
and medical industries. Pectates are salts or esters of pectic acid. Hromádková et al. (2008) have
610
reported the synthesis of some pectates (pectate alkyl amides) from citrus pectin via
611
alkylamidation of esterified pectin from this source, followed by alkaline hydrolysis. These
612
pectate amides were also tested for their foam stabilizing abilities. Schweiger (1962) has reported
613
some routes for the substitution at hydroxyl groups of pectic substances, like nitropectin without
614
the rigorous conventional catalyzed reaction involving acetic anhydride or acetyl chloride in
615
pyridine. Just like other pectic substances, pectates have also been involved in corrosion
616
inhibition in some media in a view to utilizing their free alcoholic groups for metal surface
617
bonding. Zaafarany (2012) has reported corrosion inhibition of pectates (with alginates) anionic
618
polyelectrolytes for Al in 4 M NaOH using chemical methods. The presence of pectate in
619
solution of the electrolyte markedly reduced the corrosion rate of Al, and an inhibition efficiency
620
(% η ) magnitude up to 88% was recorded for 1.6% pectate in the solution of the alkaline
621
electrolyte using weight loss technique. Corrosion inhibition was found to be inhibitor
622
concentration and temperature dependent but the study was without an explanation of the
623
possible
624
kinetics/thermodynamic modelling. Recently, Zaafarany’s group has revisited this work using
625
sodium alginate and sodium pectate for pure Al substarte in the same corrodent (Hassan et al.
626
2013; Hassan and Zaafarany, 2013). The corresponding magnitudes of corrosion rate derived
627
from the techniques used in this study were computed and showed negligible difference.
628
Corrosion inhibition by Na pectate was ascribed to physical molecular adsorption with the
629
mechanism elucidated by means of thermodynamic and kinetic parameters. Pectate adsorption on
630
the metal surface followed Langmuir and Freundlich isotherm models.
Ac ce pt e
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corrosion
inhibition
mechanism,
electrochemically
or
by
means
of
631
632
Chitosan and substituted/modified chitosans
23
Page 23 of 74
Chitosan is a hydrophilic carbohydrate polymer naturally occurring in chitin-rich
634
exoskeletons of marine crustaceans and in shrimps and crabs, and can also be extracted by N-
635
deacetylation of fungal cell-wall chitin via alkaline treatment as well as chitins from simple
636
arthropods. It is being widely used against skin infections due to its antibacterial and fungal
637
properties, and as drug-carriers in modern therapeutics (https://en.wikipedia.org/wiki/Chitosan).
638
The antibacterial activities of chitosan as well as its combination with other polymers have been
639
studied for a range of Gram-positive and negative bacterial infections (Rabea et al. 2003; Gabriel
640
et al. 2015; Aziz et al. 2012; Chung et al. 2011; Feng et al. 2014a). Chitosan is also employed in
641
the textile, paper and food industries for various applications. Chitosan’s anticorrosion ability
642
could be drawn from its molecular structure (Figure 5); it bears electron-rich hydroxyl and amino
643
groups capable of metal surface bonding subsequent corrosion inhibition via coordinate bonding
644
as these electrons are donated to the empty or partially occupied Fe orbitals. The grafting of
645
these polar groups unto surfaces increases total surface energy components thereby further aiding
646
corrosion inhibition (Umoren et al. 2013). Chitosan is a polysaccharide bearing β-(1-4)-linked
647
and N-acetyl- D-glucosamine units in its monomeric moiety.
648 649
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633
Figure 5. Molecular structure of chitosan.
650
Earlier reports on the corrosion inhibition of chitosan are those previously reported in acid-
651
induced conditions for copper and mild steel (El-Haddad 2013; Cheng et al. 2007; Fekry and
652
Mohamed 2010; Mohamed and Fekry 2011). Using chemical and electrochemical techniques,
653
the corrosion inhibition of copper has been investigated in 0.5 M HCl using chitosan by El-
654
Haddad (2013). Chitosan was revealed as being a mixed-type inhibitor in the acidic condition
655
from its unique Tafel behavior. Electrochemical impedance results revealed steady decrease in
656
capacitance and increase in resistance with increasing concentration of chitosan. Inhibition of 24
Page 24 of 74
copper corrosion in HCl was attributed to molecular absorption of this biopolymer unto the metal
658
surface, and this was approximated with Langmuir isotherm and also evaluated with SEM and
659
FTIR. Quantum chemical calculations were also used to correlate the corrosion inhibition with
660
the molecular structure of chitosan. Cheng et al. (2007) have reported the effectiveness of
661
Carboxymethylchitosan-Cu2+ mixture for inhibition of mild steel in 1 M HCl gravimetric
662
(between 298 and 353K) and electrochemical techniques. Steel corrosion inhibition by this
663
mixture was attributed to synergistic effect from both polymeric and ionic components; as
664
individual components inhibited less than a combination of both. The magnitude of % η greater
665
than 90% was obtained for Carboxymethylchitosan-Cu2+ mixture, with 86 and 14% obtained for
666
20 mg/L Carboxymethyl chitosan and 0.01 ppm Cu2+, respectively. Corrosion inhibition of mild
667
steel in the presence of this mixture was also attributed molecular adsorption of chitosan, and its
668
inhibition mechanism was further investigated with conductometry. Physical adsorption
669
mechanism was also proposed from thermodynamic/kinetics parameters. Fekry and Mohamed
670
(2010) have reported the anticorrosion ability of Acetyl thiourea chitosan conjugate polymer,
671
synthesized by first preparing acetyl thiocyanate before adding to dissolve chitosan solution (in
672
dimethyl formamide/ acetic acid mixture at 100 ◦C). Using polarization and EIS techniques,
673
corrosion studies with this chitosan–derived conjugate polymer was conducted for mild steel in
674
aerated 0.5 M H2SO4. Corrosion rate of mild steel greatly reduced in the presence of this
675
conjugate polymer but increased with temperature. Corrosion resistance was found to increase
676
with immersion time, revealing that mild steel corrosion inhibition by chitosan was due to
677
molecular adsorption on prolonged immersion. A % η value of 94.5% was obtained for 0.76 mM
678
concentration of this conjugated biopolymer in the solution of the acidic electrolyte. SEM was
679
employed in studying the surface morphology of the steel substrate, in terms of the prevalence of
680
deep localized pits and the formation of protective film, in the absence and presence of inhibitor,
681
respectively. Fekry and Mohamed (2011) have also reported the corrosion inhibition of chitosan-
682
crotonaldehyde schiff’s base for AZ91E alloy inhibition in artificial sea water using EIS and
683
Tafel techniques. Corrosion resistance in the saline solution was found to increase with the
684
immersion time and concentration of the schiff’s base but decreased with temperature. AZ91E
685
alloy corrosion inhibition was attributed to the adsorption of inhibitor films on the surface of the
686
metal substrate, and this was confirmed by results from SEM. Chitosan-crotonaldehyde schiff’s
687
base was also used to adsorb Congo red dye and Maxilon Blue dyes, and its antimicrobial
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activities were investigated against Escherichia coli, Staphylococcus aureus, Aspergillus niger
689
and Candida albicans. Umoren et al. (2013) have investigated the role of a synthetically-derived
690
chitosan in 0.1 M HCl for mild steel corrosion using chemical, electrochemical and surface
691
analytical techniques. Corrosion inhibition was found to increase with the concentration of
692
chitosan, with values of % η greater than 90 % recorded at low concentrations of the
693
biopolymer. Its Tafel behavior revealed a mixed-type inhibition for the range of concentrations
694
studied. Authors attributed steel corrosion inhibition to the formation of film at the surface of the
695
substrate, and this was confirmed by SEM and UV spectroscopy. Chitosan’s chemisorption at the
696
metal surface followed Langmuir adsorption isotherm, and kinetic/thermodynamic parameters
697
were calculated to further explain the mechanism of molecular adsorption. In another study, the
698
anticorrosion properties of O-fumaryl-chitosan on low carbon steel has been investigated in
699
aqueous HCl using weight loss and electrochemical techniques (Sangeetha et al. 2015b).
700
Potentiodynamic polarization results revealed this modified chitosan biopolymer influenced both
701
cathodic and anodic reactions, and recorded a 93% inhibition efficiency at 500 ppm. For all the
702
techniques employed in this study, the corrosion rate of the metal substrate reduced with the
703
concentration of the chitosan inhibitor. The trend in corrosion resistance and double layer
704
capacitance with the concentration of the inhibitor was evaluated from the impedance results.
705
Steel inhibition in the presence of this compound was attributed to the film formation and
706
adhesion of complexes at the surface of the metal via molecular adsorption. This was confirmed
707
with surface analytical techniques (SEM, AFM and FTIR), with the mechanism of inhibition
708
proposed from electrochemical findings including zero charge potential evaluation. The
709
corrosion mechanism was also evaluated by means of adsorption isotherm plots and the
710
assessment of the thermodynamics of the inhibition process.
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711
More applications of modified chitosans and their composites also abound in the
712
literature. Heptanoate anions have been encapsulated into chitosan-modified beidellite coating
713
for corrosion protection of galvanized steel (Aghzzaf et al. 2012). The coating system was
714
designed to initiate continuous releasing of inhibiting heptanoate molecules to the surface
715
thereby healing any inherent micro-cracks. Diffuse reflectance infrared Fourier transform
716
spectroscopy (DRIFTS), TG coupled MS and XRD techniques were employed in studying the
717
coating prior to corrosion test with EIS in 3 wt% NaCl for the coated galvanized steel. The steel
26
Page 26 of 74
corrosion protection of this modified chitosan hybrid inhibitor was compared to a commercially
719
available anticorrosive pigment (Triphosphate aluminium). The improved corrosion inhibition
720
for this class of coating was attributed to leaching of hepatanoate ions at the metal/coating
721
interface. Li et al. (2015) have synthesized and investigated the anticorrosion properties of some
722
methyl acrylate grafted and triethylene tetramine/ethylene diamine chitosan copolymers for
723
Q235-grade carbon steel in 5% HCl at 25oC for 72 h using chemical and electrochemical
724
techniques. The improved corrosion inhibition of these hybrid chitosan systems was attributed to
725
high chemical grafting; ethylene diamine chitosan copolymers gave a 90% corrosion inhibition
726
efficiency (% η ) compared to the triethylene tetramine grafted system (% η = 85%). Steel
727
corrosion inhibition was also attributed to the adsorption of grafted polymeric molecules to the
728
surface of the metallic substarte; this was confirmed by metallographic microscopy and SEM.
729
Thiocarbohydrazide graft chitosan has been synthesized and its anticorrosion properties
730
investigated against 304 steel and Cu sheet corrosion in stagnant 2% acetic acid electrolyte
731
containing the modified chitosan inhibitor (Li et al. 2014a). Electrochemical polarization result
732
reveals the compound as a mixed type inhibitor with a magnitude of % η greater than 85% at
733
concentration of 30 mg/L. Thiocarbohydrazide graft chitosan was also used by authors to extract
734
some heavy metal (As, Ni, Cu, Cd, Pb) ions up to an adsorption efficiency of 60–99% at pH 9.
735
Using the same metal substrates and in the same test electrolyte, authors have also investigated
736
the corrosion inhibiting abilities of some thiosemicarbazide and thiocarbohydrazide modified
737
chitosan derivatives (Li et al. 2014b). They were reported to be mixed-typed systems as well, and
738
with a magnitude of % η greater than 90% at concentration of 60 mg/L. An adsorption efficiency
739
of 60–99% for As, Ni, Cu, Cd, Pb ions at pH 9 was also reported for both compounds were
740
employed as aqueous phase absorbents. Recently, Liu et al. (2015) have investigated the efficacy
741
of β-cyclodextrin modified natural chitosan for carbon steel corrosion in 0.5 M HCl using
742
chemical and electrochemical techniques. Corrosion inhibition was found to increase with
743
concentration of inhibitor at 30 oC. Potentiodynamic polarization results revealed this modified
744
carbohydrate biopolymer influenced both cathodic and anodic reactions with magnitude of % η
745
greater than 95%. Corrosion inhibition by this compound was attributed to its molecular
746
adsorption unto the metal surface, and this was approximated with Langmuir adsorption isotherm
747
also involving both physisorption and chemisorption protection mechanism. Metal surface
748
adsorption was confirmed with SEM/EDS. Chitosan films has also been involved in synthesis of
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Page 27 of 74
protective coating for corrosion inhibition. In a recent report, chitosan has been deposited on
750
mild steel substrates by solution electrophoresis via the application of a 15 V potential for 15
751
mins in a binary solution of chitosan/acetic acid with glutaraldehyde employed as the cross linker
752
(Ahmed et al. 2012). FTIR and SEM techniques were employed for surface characterization of
753
the film after electrodeposition before corrosion test using EIS and polarization methods with the
754
coated substrates immersed in 0.5 M H2SO4. Corrosion resistance of the chitosan coating was
755
found to decrease with immersion time in the solution of the electrolyte, and a % η value of 98%
756
was obtained at the experimental condition under study compared to bare steel. A self-healing
757
chitosan-based hybrid coating doped with cerium (Cs) ions has also been synthesized for
758
aluminium alloy AA 2024 (Zheludkevich et al. 2011). Cs ions served as an encapsulated
759
corrosion inhibitor in the bulk of the coating thereby enhancing the material’s mechanical and
760
protective strength. Optical microscopy, SVET, SEM/EDS and FTIR techniques were used in
761
analyzing the undoped chitosan, and Ce-doped chitosan coating, before and after immersion in
762
the solution of the electrolyte after different exposure period in 0.05 M NaCl solution. EIS
763
results reveal prolonged corrosion protection for the hybrid chitosan coating in the presence of
764
Cs ions doped in the pre-layer of the coating. Its self-healing ability at specific micro-confined
765
defects were assessed via localized electrochemical study. The protective properties of
766
Chitosan/Zn composite coating electrodeposited on mild steel from zinc sulphate/sodium
767
chloride binary solution has been reported by Vathsala et al. (2010). The effect of variation of
768
principal electrolyte components as well as the concentration of Zn ions was investigated vis-à-
769
vis superior protection. Corrosion test was conducted in 3.5 wt% NaCl for this class of coating
770
using chemical and electrochemical techniques, as well as salt spray test. The enhance corrosion
771
protection of this coating was attributed to synergistic inhibitive action of Zn ions in the coating,
772
this was evident in the increased corrosion resistance in the presence of the Zn ions using EIS.
773
SEM was also employed in studying the surface morphologies and crystallinity in the presence
774
of chitosan. El-Sawy et al. (2001) have reported the synthesis of Poly(DEAEMA)-chitosan-graft-
775
copolymer, poly(COOH)- chitosan-graft-copolymer, poly(V-OH)-chitosan-graftcopolymer, and
776
carboxymethyl-chitosan for the corrosion protection of steel panels uniformly coated at room
777
temperature. Corrosion protection was reported to increase in more highly grafted coatings, and
778
their protection mechanism was attributed to their bulk properties as well as the strength
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Page 28 of 74
779
coating/metal bonding (adhesion). These compounds were also used in adsorbing metals ions
780
and dyestuffs from aqueous solutions. The modification of chitosan molecules also involves the syntheses of its nanoparticle
782
composites for metal protection, and a few of them has been reported in the literature. Atta et al.
783
(2015) have synthesized hydrophobic chitosan nanogels with unsaturated fatty acids before
784
grafting them with polyoxyethylene aldehyde monomethyl ether to prepare amphiphilic chitosan
785
surfactant (ACS). Nanoscaled particles of this surfactant were later made from emulsification
786
and crosslinking reactions using methylene chloride with sodium tripolyphosphate, respectively.
787
Hydrophobicity, functional group and particle size analyses were carried out using appropriate
788
analytical techniques. Characterization of the grafted nanoparticles was followed by
789
electrochemical corrosion tests using EIS and Tafel methods. Values of Cdl decreased while the
790
corrosion resistance of carbon steel rode was found increase with the concentration of the
791
nanogel in the HCl (1 M) electrolyte, with values of % η greater than 85% recorded at a
792
nanoscale concentration of 250 mg/L. Corrosion inhibition of this nanogel was attributed to the
793
formation of active protective film carrying chitosan molecules at the metal/solution interface;
794
this was further confirmed by SEM analysis. John et al. (2015) have also reported the synthesis
795
of nanostructured chitosan/ZnO nanoparticles by sol-gel method, and its anticorrosion ability
796
evaluated electrochemically by Tafel and EIS techniques for mild steel in 0.1 N HCl. Improved
797
metal surface protection was revealed for compacted films in the presence of ZnO, and this
798
further enhanced increased values of inhibition efficiency (% η >70% and < 40% was obtained in
799
the presence and absence of ZnO, respectively). Formation of nanofilms on steel was concluded
800
as the principal cause of corrosion inhibition of steel, and this was characterized with UV–vis,
801
FTIR, XRD and SEM/EDX. Luckachan and Mittal (2015) have recently reported the protective
802
of layer-by-layer chitosan/poly vinyl butyral coating on steel investigated using electrochemical,
803
spectroscopic and SEM. This corrosion resistant property of this hybrid coating was evaluated
804
after 2 h immersion in 0.3 M NaCl, with the formation of passive oxide layer (Fe3O4 and γ -
805
Fe2O3 oxide) on the metal substrate confirmed by SEM and Raman spectroscopy. Barrier
806
protection by this coating was found to improve due to the chitosan middle layer sandwiched
807
between poly vinyl butyral bilayers on the metal substrate, as well as the incorporating
808
glutaraldehyde within the chitosan layer. This was not observed with graphene and vermiculite
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Page 29 of 74
incorporated with the same chitosan matrix in the same condition. Other anticorrosion
810
applications involving pectic acid/pectates and modified chitosans and their composites reported
811
in the literature are presented in Table 3.
812
Carrageenan
813
Carrageenan is a group of gel-like and mostly linear polysaccharides bearing sulfated b-D-
814
galactose and 3,6-anhydro-a-D-galactose backbone and commonly found in seaweeds (family:
815
Rhodophyceae). Figure 6 displays the molecular structure (iota), though other structures (e.g.
816
Mu, Kappa, Nu, Lambda forms) do exist in nature. Carrageenan can also be classified according
817
to the degrees of linear chain sulfation as well as the degree of the substitution occurring at the
818
free hydroxyl groups on the linear polysaccharide chain. Their molecular symmetry is flexible,
819
forming unstable helical conformations, thereby making most carrageenans exist as gels at room
820
temperature. This unique physical structures aids in their application as food thickeners and
821
stabilizers (van de Velde et al. 2005). Nanaki et al. (2015) have reported the synthesis of
822
modified carrageenans at different concentrations for aqueous state Metoprolol ((1-
823
(isopropylamino)-3-[4-(2-methoxyethyl)phenoxy]propan-2-ol)) removal at room temperature.
824
The kinetics of carrageenan oxidation (iota and lambda forms) by permanganate in perchlorate
825
solutions have also been reported by Hassan et al. (2011). In the same acidic solution, this group
826
has also investigated the effect of hydrogen ion concentrations on chromic acid oxidation rate of
827
k-carrageenan (Zaafarany et al. 2009). Carrageenans are green and biodegradable carbohydrate
828
polymers with the potentials for corrosion protection just like other carbohydrate polymers
829
discussed in this series. They are benign and due to their unique chemical structures and
830
functional groups, they possess the ability of complexing ions of metals at surfaces, thereby
831
inhibiting aqueous corrosion. The sulphonic acid groups on these biopolymers are endowed with
832
π-orbital character of donating electron to the empty 3d orbital of the Fe substrates. The
833
investigation of the corrosion inhibition potential of i-carrageenan for aluminium sheets in
834
presence of a mediator has been reported using weight loss technique after 2 h immersion in
835
different concentrations of HCl (1.0–2.0 M) (Fares et al 2012b). Al corrosion inhibition by i-
836
carrageenan was found to improved greatly in the presence of pefloxacin mesylate (inhibition
837
mediator); magnitude of % η increasing from 66.7% to 91.8%. This metal inhibition
838
enhancement was attributed to the synergistic adsorption of i-carrageenan/ pefloxacin mediator
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Page 30 of 74
compact film on the surface of the metal (Al). This was confirmed by SEM analysis, while the
840
corrosion inhibition mechanism by molecular adsorption was further explained with kinetics and
841
thermodynamics evaluation in the presence of the inhibitor and mediator. Inhibitor molecular
842
adsorption followed Langmuir adsorption isotherm model. Zaafarany (2006) has also studied the
843
corrosion inhibition of low carbon steel in 1 M HCl using weight loss and galvanostatic
844
polarization techniques with i, k, µ─ carrageenan. Corrosion inhibition was found to decrease
845
temperature but increased with the concentration of these polysaccharide biopolymers. Corrosion
846
inhibition was attributed to the blocking the steel surface by carrageenans’ molecular adsorption.
847
The adsorption of the inhibitors on the metal substrate followed Langmuir adsorption isotherm.
848
These compounds were revealed as being anodic-type inhibitors for steel in the acidic medium
849
studied, and kinetics and activation thermodynamic parameters were computed to add insights
850
into the corrosion inhibition mechanism.
an
us
cr
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839
M
851 852
Ac ce pt e
d
853 854 855
Figure 6. Molecular structures of carrageenan repeat unit.
856 857 858 859
860
Dextrin and cyclodextrins
861
Dextrin is a class of low molecular weight carbohydrate polymers structurally characterized by
862
glucose (D) units linked by glycosidic bonds [α-(1→4) or α-(1→6)]; Figure 7. They occur
863
naturally in the human digestive system via amylases catalyzed starch hydrolysis in the human
864
mouth;
it
can
also
be
synthesized
by
heat
treatment
in
acidic
solutions
31
Page 31 of 74
(https://en.wikipedia.org/wiki/Dextrin). Various forms of dextrin exist in nature ranging from
866
maltodextrin, amylodextrin, α , β -dextrin, cyclic and highly branched cyclic dextrin compounds.
867
Apart from being employed as food additives and in brewing, short chain dextrin as well as the
868
highly branched cyclic derivatives have been deployed as corrosion inhibitors in various
869
corrosive media (Jayalakshmi and Muralidharan, 1997); earlier researches date back between the
870
late 1970’s and the early 1980’s for titanium and aluminium/copper alloys, respectively (Shibad
871
and Balachandra, 1976; Patel et al. 1981; Talati and Modi, 1976).
cr
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865
an
us
872
873
Figure 7: Molecular structure of dextrin
875
Loto and Loto (2014) have reported the effect of dextrin and thiourea additives on the corrosion
876
of steel (low carbon grade) after electroplating the surface with zinc by applying negative
877
potential between with a zinc electrode connected to the steel test substrate in ZnCl2 solution.
878
The corrosion test was conducted in an acid chloride electrolyte. The electroplating procedure
879
revealed densely packed zinc crystals on steel without pores but the substrates possessed
880
different surface morphologies for every plating period under study. Dextrin in combination with
881
thiourea additive demonstrated remarkable superior protection at the highest plating period
882
compared to the rest of the matrices as examined by SEM/ EDS. The anticorrosion properties of
883
β-cyclodetrin-modified acrylamide polymer have been investigated 0.5 M H2SO4 for X70 steel
884
grade by electrochemical and surface analytical techniques. Potentiodynamic polarization results
885
revealed that this modified carbohydrate influenced both cathodic and anodic reactions with a
886
magnitude of % η greater than 84.9% for 150 mg/l at 303 K. Adsorption of the hybrid polymer
887
on metal surface followed Langmuir adsorption isotherm and corrosion inhibition was explained
888
by means of thermodynamic and kinetics parameters. Corrosion inhibition was attributed to
889
molecular adsorption at the metal surface, confirmed by SEM/EDS (Zou et al. 2014a). Zou et al.
890
(2014b) have investigated the efficacy of bridged β-cyclodextrin-polyethylene glycol (β-DP) for
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874
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Page 32 of 74
Q235 carbon steel in 0.5 M HCl using chemical and electrochemical techniques. β-DP was
892
characterized by FTIR reacting after being synthesized via a reaction between β-cyclodextrin
893
with polyethylene glycol. Tafel polarization curves revealed that this hybrid biopolymer was a
894
mixed type inhibitor compound in the solution of the electrolyte while corrosion inhibition was
895
attributed the formation of protective β-DP film at the surface of the metal; this was confirmed
896
by SEM/EDX. Recently, authors have also reported the scale inhibition using β-DP composite
897
for produced-water in shale gas well with up to 89.1% maximum scaling inhibition efficiency for
898
180 mg/l (Liu et al. 2016). Yan et al. (2014) have reported the effectiveness of polyacrylamide
899
modified β-cyclodextrin composite for inhibition of X70 steel corrosion in in 0.5 M H2SO4 using
900
electrochemical and chemical methods and surface analytical techniques. Corrosion inhibition in
901
the presence of this composite was found to increase with its concentration but not with
902
temperature while the trend in Tafel polarization data revealed that polyacrylamide/β-
903
cyclodextrin composite was a mixed type inhibitor system. Corrosion inhibition was attributed to
904
molecular (chemisorption) adsorption of this composite on the metal surface and the adsorption
905
phenomenon followed Langmuir isotherm. SEM results revealed the formation of
906
polyacrylamide/β-cyclodextrin composite protective film on X70 steel surface. Liu et al. (2015)
907
have studied the anticorrosion properties of chitosan-grafted β-cyclodextrin composite for carbon
908
steel corrosion in 0.5 M HCl using weight loss, potentiodynamic polarization, EIS and
909
SEM/EDS techniques. DC polarization curves reveal that the presence of this inhibitor
910
composite affected both cathodic and anodic reaction with 96.02% as the highest inhibition
911
efficiency at 230 ppm. Corrosion inhibition of carbon steel in the presence of this composite was
912
also attributed molecular adsorption, and its adsorption process was approximated with
913
Langmuir adsorption isotherm. Physisorption/chemisorption adsorption mechanism was also
914
proposed from the variation in thermodynamic parameters. Fan et al. (2014) have reported the
915
synthesis of hydroxypropyl-β-cyclodextrin/ octadecylamin supramolecular complex with
916
anticorrosion properties for Q235A steel. Corrosion study was conducted in CO2 saturated
917
deionized water (at 5.6 pH) at room temperature using chemical and electrochemical techniques
918
after the characterization of the synthesized supramolecular complex with FTIR, XRD and NMR
919
spectroscopy. Corrosion inhibition efficiency of 95% was obtained for the synthesized complex
920
and the inhibition process was attributed to the formation of passive inhibitor layer as well as
921
hydrophobic octadecylamin inherent in the supramolecular complex at the metal surface. The
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Page 33 of 74
complex acted predominantly anodic than cathodic from the trend of Tafel polarization results
923
with 90% inhibition efficiency obtained for 50 mg/l complex.
924
Alginates
925
This acid-type anionic polysaccharide is the principle component in the colloidal gum found in
926
the cell walls of algae and seaweeds where it binds with molecular water. Alginate is a group of
927
sugars also called alginic acid (due to the carboxylic acid functional group attached to their
928
molecular structure) or algin; they are linear copolymers with covalently bound (1-4)-linked β-D-
929
mannuronate and C-5 epimer α-L-guluronate homopolymeric blocks (Figure 8). Alginates have
930
numerous forms depending on their salts (principally alkaline or alkaline salts). Na alginate
931
extracts from brown seaweeds are widely deployed as dental gelling agents, and their usage is
932
common in pharmaceutical as well as food industries. K and Ca alginates are used as industrial
933
alternatives to Na alginates while the organic forms of this compound have also been synthesized
934
with various applications.
935 936
Ac ce pt e
d
M
an
us
cr
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922
Figure 8. Molecular structure of alginate.
937
Alginates have also been widely reported as corrosion inhibitors for various metals in different
938
media, and one of the earliest reports with regards to alginate is the one by the Desai’s in the late
939
70’s (Desai and Desai, 1970) where the effect of Na alginate on the cathode and anode potentials
940
of A1-3S in 0.2 N NaOH was evaluated. Sriram et al. (2014) have studied the anticorrosion
941
properties of Na alginate extracts from a brown seaweed (Turbinaria ornate) for aluminium
942
alloy (AA 7075 grade) in 3.5 wt% NaCl using potentiodynamic polarization technique. This
943
extract was found to inhibit aluminium corrosion to a great extent, with 95% inhibition
944
efficiency obtained at 2000 ppm after 24 h. Authors attributed this to the adsorption of
945
inhibition-inducing functional groups found on the extract; this was also confirmed with FTIR
946
spectroscopy. This compound has also been reported for carbon steel corrosion in 0.5 M HCl
947
investigated by chemical and electrochemical techniques (Al-Bonayan, 2014). Corrosion 34
Page 34 of 74
inhibition was found to increase with the concentration of Na alginate but not with temperature;
949
this was attributed to the adsorption of sodium alginate at the metal surface. Molecular
950
adsorption was explained by means of isotherm and activation parameters derived from results of
951
the chemical technique, while the effect of concentration of the inhibitor on the charge transfer
952
resistance and capacitance of double layer was also explained. Zaafarany (2012) have also
953
reported the application of alginate (apple derived)-anionic polyelectrolytes as corrosion
954
inhibitors for pure aluminum in 4 M NaOH at 25 oC using gravimetric and gasometric
955
techniques. A corrosion inhibition efficiency of 86.66% was recorded for 1.6% alginate at 30 oC
956
in the alkaline test solution. Al corrosion reduction in this medium was attributed to the unique
957
functional chemistry on the inhibitor, and the mechanism of inhibition was explained in terms of
958
kinetic and thermodynamic parameters. Deployed form magnesium test substrate (AZ31 alloy
959
grade), Na alginate have also been recently studied by another group of authors in 3.5 wt% NaCl
960
(Dang et al. 2015). They found that corrosion inhibition increased with concentration of Na
961
alginate though a decrease in magnesium protection was also observed after prolonged
962
immersion in the solution of the inhibitor. A corrosion inhibition efficiency of 90% was obtained
963
for 500 ppm Na alginate, and this was attributed to molecular adsorption and subsequent
964
formation of compact film (freshly generated magnesium hydroxide) on the metal surface.
965
Tawfik (2015) has synthesized and appropriately characterized alginate surfactant derivatives for
966
anticorrosion application. These surfactants were deployed as corrosion inhibitors for carbon
967
steel in 1 M HCl using chemical, electrochemical and surface analytical techniques. Corrosion
968
inhibition increased with the concentration of these compounds and with temperature, with a
969
96.27% inhibition efficiency obtained for 5 mM alginate derived cationic surfactant complexed
970
with copper. Tafel curves revealed that these inhibitors were mixed type though predominantly
971
cathodic. Parameters derived from thermodynamic and activation evaluations of the trend in
972
experimental results were employed to investigate the inhibition mechanism. Wang et al (2015)
973
have recently investigated the anticorrosion properties of Ca alginate gel loaded with imidazoline
974
quaternary ammonium salts; this composite was prepared by piercing-solidifying method
975
designed to automatically release these imidazoline corrosion inhibitors at the metal surface
976
(P110 steel) immersed in CO2-saturated 3.5 wt% NaCl medium. Corrosion studies were
977
conducted by EIS while UV-Vis spectroscopy and SEM complemented the electrochemical
978
technique as surface analytical techniques. This auto-release inhibition type system was effective
Ac ce pt e
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Page 35 of 74
to a great extent as the corrosion inhibitors were released from the gel as it swells in the solution
980
of the corrosive electrolyte. BaSO4 was also encapsulated within alginate/ imidazoline composite
981
in order to aid sinking and improved corrosion retardation was well. Hydroxyl propyl alginate,
982
an organic type alginate derivative, have been deployed to reduce mild steel corrosion in 1 M
983
HCl at room temperature using chemical and electrochemical techniques. Corrosion inhibition
984
was found to increase with the concentration of this compound due to molecular (physisorption)
985
adsorption at the metal surface; confirmed by SEM, AFM and FTIR as adsorbed film. Results
986
from Tafel polarization revealed that corrosion inhibition in the presence of this compound
987
affects both anodic and cathodic reactions. Inhibitor adsorption was also explained in terms of
988
adsorption isotherm, thermodynamic and kinetic parameters (Sangeetha et al. 2016). Typical
989
examples of inhibition systems involving dextrin, alginates and their derivatives deployed for
990
metal corrosion reduction in various aggressive media are presented in Table 4.
991
Effect of halide ion additives on corrosion inhibition with carbohydrate polymers
992
In many aggressive media, depending of the service environment to which an organic inhibitor is
993
being deployed, corrosion inhibition is normally aimed at achieving the maximum reduction in
994
metal dissolution with the utmost efficiency (Eduok et al. 2013; Eduok and Khaled 2014, 2015).
995
With this in mind, the improvement of the performance of any inhibition system employed
996
becomes a very importance aspect of the whole corrosion reduction program. Researchers
997
worldwide over the years have developed a number of additives to synergistically aid corrosion
998
reduction in the presence of organic compounds regardless of their modes of action and surface
999
chemistries; almost of these additives are halides (Eduok et al. 2012; Umoren et al 2008c). The
1000
application of some halides with organic inhibitors have been widely reported as having greater
1001
total inhibition effect compared to when only one of inhibitors used independently; hence
1002
synergism (Caliskan and Bilgic 2000; Ridhwan et al. 2012; Tang et al. 2006; Bouklah et al 2006;
1003
Bentiss et al. 2002). This unique property of halides has been largely linked with the formation
1004
of ion-pairs between the organic inhibitors and the halide ions leading to increased surface
1005
coverage. Since molecular adsorption is a key factor in corrosion inhibition, the ionic radii as
1006
well as the electronegativity of these ions have been conceived to contribute immensely to
1007
corrosion inhibition. Synergistic effect of halide ions have been found to follow this order
1008
depending on their ionic radii (pm): I─ (206) > Br─ (182) > Cl─ (167). Iodides, in particular, have
Ac ce pt e
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Page 36 of 74
been known for improved inhibition due to their hydrophobicity and the stabilization of adsorbed
1010
ions with the cations of most organic polymers leading to increased metal surface coverage
1011
(Bouklah et al. 2006). The initial adsorption of iodide ions on the surface of metal substrate aids
1012
further molecular adsorption of organic inhibitor by coulombic attraction thereby forming more
1013
stable protective film at the metal/solution interface (Musa et al. 2011; Harek and Larabi 2004).
1014
Since most organic inhibitors are thermally unstable, their usage in combination with halides
1015
becomes necessary, prompting enhanced metal surface protection from aggressive ions and
1016
molecules at increased temperature. Umoren and Solomon (2015) have recently reported a
1017
comprehensive review on the some inhibitor─halide systems for metal inhibition, yet studies
1018
involving the effects of halide ions on the corrosion inhibition of biopolymers are a scare,
1019
although there have been more investigations (Umoren et al. 2010; Rajeswari et al. 2013;
1020
Arukalam et al. 2015) on substituted cellulose compounds than any other class of carbohydrate
1021
biopolymer in the literature (See Table 5 for list of carbohydrate ploymer-halide inhibition
1022
systems deployed for metal corrosion studies in various aggressive media including the reasons
1023
for corrosion inhibition in the presence of the halide.
M
an
us
cr
ip t
1009
The effect of halide ions (Cl─, Br─, and I─) additives at 30–60 oC on the inhibition
1025
performance of CMC on mild steel corrosion in 2 M H2SO4 has been investigated using weight
1026
loss and hydrogen evolution techniques (Umoren et al. 2010). In the presence of the halide
1027
additives, corrosion inhibition was found to be dependent on their concentrations as well as the
1028
solution temperature and immersion period. Mild steel corrosion inhibition for CMC increased
1029
greatly in the presence of the iodide ions, and this was attributed to a synergistic effect while the
1030
presence of chloride ions antagonized the proposed inhibition process, with and without the
1031
principal inhibitor (CMC), from the results of both corrosion monitoring techniques. The weight
1032
loss technique at 30 oC revealed magnitudes of corrosion inhibition efficiency (% η ) of 89 and
1033
65%, respectively, in the presence and absence of 5 mM I─, while 48 and 63 % were recorded for
1034
5 mM Cl─ and Br─. Corrosion inhibition was linked with metal surface adsorption of inhibitor
1035
compounds and this followed Langmuir adsorption isotherm in the presence of the halide ions.
1036
Conversely, corrosion performance for each halide ion deceased with temperature due to
1037
molecular desorption at higher solution temperatures. In another study, authors have reported the
1038
enhance inhibition performance of hydroxypropyl methylcellulose and hydroxyethyl cellulose
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1024
37
Page 37 of 74
(substituted cellulosic compounds; SCC) in 0.5 M H2SO4 for aluminium (AA 1060 type) and
1040
mild steel using weight loss and electrochemical polarization and impedance spectroscopy
1041
(Arukalam et al., 2014a,b; Arukalam, 2014). The formation of passive oxide film on the Al
1042
surface was found to great dissolve in the acidic test solution, but the rate of dissolution
1043
decreased on addition of SCC. Improved protection for SCC was recorded in the presence of 500
1044
mg/L KI as EIS revealed increased corrosion resistance in the presence of this halide ion.
1045
Adsorption of SCC in the presence of the iodide ions on Al followed Freundlich (Arukalam et
1046
al., 2014a,b) and Langmuir (Arukalam, 2014) adsorption isotherm models. Hydroxypropyl
1047
methylcellulose-KI was revealed as a mixed-type inhibitor (though dominantly cathodic) from
1048
Tafel results. Authors further explained the relationship between hydroxypropyl methylcellulose
1049
adsorption and corrosion mechanism using DFT approach to quantum chemical calculations.
1050
Another corrosion inhibition performance of a biopolymer (ethyl hydroxyethyl cellulose; EHC)
1051
attributed to synergistic effect of iodide ion addition has been reported for mild steel in 1 M
1052
H2SO4 using experimental (chemical and electrochemical) and theoretical (quantum chemical
1053
calculations by DFT) evaluations (Arukalam et al., 2014c). Corrosion resistance was found to
1054
increase in the presence of 0.5 g/L KI added to the test solution with % η values up 58 and 52%
1055
recorded in the presence and absence of KI. Polarization results revealed that both EHC and
1056
EHC─KI were mixed-type inhibitor systems though predominantly cathodic while their
1057
adsorption followed Langmuir isotherm. Experimental evaluations were preceded by theoretical
1058
molecular orbitals and reactivity assessments of EHC’s structure in other to correlate its
1059
adsorption to the mechanism of inhibition using DFT. The effect of halide ions on the inhibition
1060
performances of exudate gums extracted from floral sources have also been investigated for
1061
some metal substrates in different media. In alkaline and acidic medium, the effectiveness of
1062
Gum Arabic (GA) towards the corrosion inhibition of Al has also been studied in the presence of
1063
these halide additives between 30 and 60 oC, using hydrogen evolution and thermometric
1064
techniques (Umoren, 2009; Umoren et al., 2006). The corrosion inhibition of GA of Al in 0.1 M
1065
NaOH and H2SO4 was enhanced in the presence of the iodide ions due to synergistic effect, and
1066
values of % η of GA-KI systems increased with temperature with corrosion inhibition attributed
1067
to adsorption (obeying Temkin adsorption isotherm in NaOH and Langmuir, Temkin and
1068
Freundlich in H2SO4). Corrosion performance of GA was greatly reduced in the presence of
1069
chloride ions, demonstrating antagonist effect for Al substrate in both corrodents. Al corrosion
Ac ce pt e
d
M
an
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1039
38
Page 38 of 74
inhibition followed the order I─> Br─ > Cl─. Umoren and Ebenso (2009) have investigated the Al
1071
corrosion inhibition with exudate gum extracted from Raphia hookeri and the effects of KCl,
1072
KBr and KI addition on its potency in 0.1 M HCl. Authors employed weight loss, hydrogen
1073
evolution and thermometric techniques in their evaluation for all the systems studied between
1074
30-60 oC. From the results of the findings, it was revealed that the inhibition performance of this
1075
gum extract was found to increase synergistically with KI and KBr in the solution of the acid
1076
electrolyte while KCl disallowed the adsorption of the gum unto the metal surface, thereby
1077
reducing its corrosion efficiency. Raphia hookeri exudates gum inhibition was attributed to
1078
molecular adsorption of its chemical constituents and this was collaborated with Freundlich,
1079
Langmuir and Temkin adsorption isotherms. Similar study have been reported for a Pachylobus
1080
edulis gum-KI system in 2 M H2SO4 using hydrogen evolution and thermometric methods
1081
investigated between 30–60 oC for mild steel corrosion (Umoren and Ekanem, 2010). Corrosion
1082
rate of the mild steel substrate reduced in the presence of the gum extract but more with the
1083
extract in combination with KI. Corrosion inhibition for both gum and gum-KI systems reduced
1084
with immersion time and with solution temperature. Physical adsorption was proposed from the
1085
dependence of temperature with trend of corrosion inhibition in the presence of the inhibitors
1086
studied; and adsorption was approximated with Temkin adsorption isotherm.
1087
Future perspective: computational approach to corrosion inhibition
1088
In some cases where core experimental results are inclusive, computational approach to
1089
corrosion inhibition is necessary. Experimental evaluations should always be supported with
1090
theoretical-based assessments of inhibition phenomena; especially the use of molecular
1091
modelling tools in correlating corrosion inhibition mechanisms with molecular structures of the
1092
inhibitor compounds (Obot et al. 2009,2010,2013; Ebenso et al., 2012; Kabanda et al., 2012).
1093
Quantum chemical modelling has been widely used in studying molecular orbitals and reactivity
1094
of organic inhibitors in other to fully understand their adsorption on metal surfaces in any
1095
aggressive (ionic) medium (Obot and Obi-Egbedi, 2010; Ebenso et al., 2012; Kabanda et al.,
1096
2012; Obot et al., 2013, 2015; Kayaa et al., 2015; Sasikumar et al., 2015; Obot, 2014). Since the
1097
mechanism of corrosion inhibition is not fully understood, model-based theoretical computations
1098
allows for an attempt to elucidate the possible phases of inhibition reactions in complex systems,
1099
hence, solving some obscured surface adhesion problems by mechanistic predictions of
Ac ce pt e
d
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an
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1070
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Page 39 of 74
applicable parameters. Carbohydrates from gum exudate show reliable reduction towards
1101
corrosion of metal substrates deployed in acidic and alkaline media, yet, it is difficult to assign
1102
inhibition to one chemical specie amongst the lot abound in these extracts. Bio-gums alone
1103
are mixtures of polysaccharides and/or glycoproteins, with typical arabinose and ribose sources.
1104
However, the use to molecular dynamics simulation (MDS) could serve as a very effective tool is
1105
studying the absorption of principal chemical constituents on the surfaces of metals, and also
1106
further explain the inhibitor-metal surface interaction, giving multiple views on possible
1107
molecular motions in the microscopic level (Obot et al., 2015; Kayaa et al., 2015; Obot, 2014).
1108
The principle of classical MDS could also help in computing time-dependent properties of this
1109
complex molecular systems as well as giving practical information about most stable
1110
conformations of inhibitor constituents prior to adsorption. Aspects of MDS could also include
1111
the study of the complexities and dynamics of inhibition processes involving polysaccharide
1112
polymeric systems by relating their inhibition mechanisms with conformational changes and
1113
surface stability (Obot et al., 2015; Kayaa et al., 2015; Sasikumar et al., 2015; Obot, 2014).
1114
Another aspect of molecular structure contributing to corrosion inhibition is the energy gap and
1115
the energies associated with frontier orbitals. Using Density Functional Theory (DFT), energies
1116
of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital
1117
(LUMO) have been widely collaborated with corrosion inhibition in terms of molecular
1118
adsorption sites on surfaces (Obot and Obi-Egbedi 2010; Ebenso et al. 2012; Kabanda et al.
1119
2012; Obot et al. 2009; Obot et al. 2013). The use of MDS and quantum chemical computational
1120
tools is therefore necessary for future studies of adsorption processes involving corrosion
1121
inhibition with carbohydrate biopolymers. Only few reports are available in the literature with
1122
regards to the application of quantum chemical computations (EL-Haddad 2013, 2014; Arukalam
1123
et al. 2014a, 2015; Umoren et al. 2015; Alsabagh et al. 2014).
cr
us
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M
d
Ac ce pt e
1124
ip t
1100
1125
Concluding remarks
1126
Temperature and solution pH are some of the few factors affecting the rate of metal dissolution
1127
in any service environment to which they are deployed; and this can be hugely reduced if
1128
efficient control procedure is employed to revert the overall corrosion dynamics. The use of 40
Page 40 of 74
biopolymers is gaining grounds in the fabrication of inhibitor formulations for various field
1130
applications, and their chemistry is simple since the adsorption mechanism accompanying them
1131
involves either physical adsorption at metal surfaces, or by chemisorption. Some mixtures of
1132
carbohydrate polymers are also known to contain chemical constituents capable of forming
1133
passivation layers that prevents the passage of corrosive ions and molecule across the
1134
metal/solution interface.
1135
Carbohydrate biopolymers, as used in this review, are macro-compounds that possess
1136
monomeric units covalently bonded to form long macromolecular sugar chains with relatively
1137
high molecular masses. They are readily available in nature, benign, renewable and ecofriendly
1138
alternative to other organic inhibitors with toxic potentials. In corrosion inhibition, they represent
1139
a set of chemically stable, biodegradable and ecofriendly macromolecules with reliable inhibiting
1140
strengths for metal surface protection; making them effective protective coatings and metal
1141
linings. This review work has elaborately described the inhibition of metal corrosion using some
1142
green pure polysaccharide biopolymers as well as their mixtures (including modifications and
1143
nanocomposites) found in the literature. Exudate gums, cellulose, starch, pectin and pectates,
1144
chitosans and carrageenan, alginate and dextrin have been reviewed including the effects of
1145
halide additives on their anticorrosion performances. Molecular weights and molecular
1146
structures/symmetry and functional group chemistry are few characteristics of these compounds
1147
that have been also described to affect the mechanisms of their protection in aqueous media. The
1148
mechanism of molecular adsorption in the presence of halide ion leads to increased metal surface
1149
coverage, and this has been explained with typical examples based on formation of ion-pairs.
1150
Corrosion inhibition with polymer-halide conjugates have also been described in terms of
1151
coulombic attraction between polymers and halide ions at the metal/solution interface, thereby
1152
forming more stable protective film. Corrosion process designs are best understood if at the
1153
molecular level, the important factors conceived to affect the behavior of the system are
1154
addressed. Such approach is better explained using computational/theoretical tools. Apart from
1155
fostering further understanding of corrosion processes, the theoretical correlating of inhibition
1156
mechanisms with molecular structures of the carbohydrate polymeric compounds will also aid
1157
the studying of molecular orbitals and reactivity of inhibitors as a key to understanding
1158
adsorption on surfaces. Molecular dynamic simulations also allows for the studying of stable
Ac ce pt e
d
M
an
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1129
41
Page 41 of 74
conformations prior to adsorption as well as the time-dependent properties of this complex
1160
molecular systems.
1161
Acknowledgments
1162
The authors gratefully acknowledged Centre of Research Excellence in Corrosion, Research
1163
Institute, KFUPM and King Fahd University of Petroleum and Minerals (KFUPM) for supporting
1164
the work.
1165
References
1166
Abdallah M (2004) Guar Gum as Corrosion Inhibitor for Carbon Steel in Sulfuric Acid
cr
us
1167
ip t
1159
Solutions. Portugaliae Electrochimica Acta 22: 161-175
Abu-Dalo MA, Othman AA, Al-Rawashdeh NAF (2012) Exudate Gum from Acacia Trees as
1169
Green Corrosion Inhibitor for Mild Steel in Acidic Media. International Journal of
1170
Electrochemical Science 7: 9303 – 9324
M
an
1168
Aghzzaf AA, Rhouta B, Steinmetz J, Rocca E, Aranda L, Khalil A, Yvon J, Daoudi L (2012)
1172
Corrosion inhibitors based on chitosan-heptanoate modified beidellite. Applied Clay
1173
Science 65-66: 173-178
d
1171
Ahmed RA, Farghali RA, Fekry AM (2012) Study for the Stability and Corrosion Inhibition of
1175
Electrophoretic Deposited Chitosan on Mild Steel Alloy in Acidic Medium. International
1176
Journal of Electrochemical Science 7: 7270 – 7282
Ac ce pt e
1174
1177
Al-Bonayan AM (2014) Sodium Aliginate as Corrosion Inhibitor for Carbon Steel in 0.5 M HCl
1178
Solutions. International Journal of Scientific & Engineering Research 5(4): 611-618
1179
Alsabagh AM, Elsabee MZ, Moustafa YM, Elfky A, Morsi RE (2014) Corrosion inhibition
1180
efficiency of some hydrophobically modified chitosan surfactants in relation to their
1181
surface active properties. Egyptian Journal of Petroleum 23: 349–359
1182
Ameh PO, Eddy NO (2014) Characterization of Acacia Sieberiana (AS) Gum and Their
1183
Corrosion Inhibition Potentials for Zinc in Sulphuric Acid Medium. International Journal
1184
of Novel Research in Physics, Chemistry & Mathematics 1(1): 25-36
1185
Ameh PO, Magaji L, Salihu T (2012) Corrosion inhibition and adsorption behaviour for mild
1186
steel by Ficus glumosa gum in H2SO4 solution. African Journal of Pure and Applied
1187
Chemistry 6: 100-106 42
Page 42 of 74
1188
Antony N, Sherine HB, Rajendran S (2010) Investigation of the inhibiting effect of
1189
carboxymethylcellulose-Zn2+ system on the corrosion of carbon steel in neutral chloride
1190
solution. Arabian Journal for Science and Engineering, 35: 42-52 Arthur DE, Jonathan A, Ameh PO, Anya C (2013) A review on the assessment of polymeric
1192
materials used as corrosion inhibitor of metals and alloys. International Journal of
1193
Industrial Chemistry 4: 2-9
1195
Arukalam IO (2012) The inhibitive effect of hydroxyethylcellulose on mild steel corrosion in hydrochloric acid solution. Academic Research International 2: 35-42
cr
1194
ip t
1191
Arukalam IO (2014) Durability and synergistic effects of KI on the acid corrosion inhibition of
1197
mild steel by hydroxypropyl methylcellulose. Carbohydrate Polymers 112: 291–299
1198
Arukalam IO, Madufor IC, Ogbobe O, Oguzie E (2014a) Experimental and Theoretical Studies
1199
of Hydroxyethyl Cellulose as Inhibitor for Acid Corrosion Inhibition of Mild Steel and
1200
Aluminium. The Open Corrosion Journal 6: 1-10
an
us
1196
Arukalam IO, Madu IO, Ijomah NT, Ewulonu CM, Onyeagoro GN (2014b) Acid corrosion
1202
inhibition and adsorption behaviour of ethyl hydroxyethyl cellulose on mild steel
1203
corrosion. Journal of Materials doi.org/10.1155/2014/101709
M
1201
Arukalam IO, Madufor IC, Ogbobe O, Oguzie EE (2014c) Hydroxypropyl methylcellulose as a
1205
polymeric corrosion inhibitor for aluminium. Pigment & Resin Technology 43: 151 – 158
1206
Arukalam IO, Madufor IC, Ogbobe O, Oguzie EE (2014d) Acidic corrosion inhibition of copper
1207
by Hydroxyethyl cellulose. British Journal of Applied Science & Technology 4: 1445-
1208
1460
Ac ce pt e
d
1204
1209
Arukalam IO, Madufor C, Ogbobe O, Oguzie EE (2015) Inhibition of mild steel corrosion in
1210
sulfuric acid medium by hydroxyethyl cellulose. Chemical Engineering Communications
1211
202:112–122
1212
Atta AM, El-Mahdy GA, Al-Lohedan HA, Ezzat ARO (2015) Synthesis of nonionic amphiphilic
1213
chitosan nanoparticles for active corrosion protection of steel. Journal of Molecular
1214
Liquids 211: 315–323
1215
Aziz MA, Cabral JD, Brooks HJL, Moratti SC, Hanto LR (2012) Antimicrobial properties of a
1216
chitosan dextran-based hydrogel for surgical use. Antimicrobial Agents and
1217
Chemotherapy 56 1: 280-287
43
Page 43 of 74
1218
Bayol E, Gürten AA, Dursun M, Kayakirilmaz K (2008) Adsorption behavior and inhibition
1219
corrosion effect of sodium carboxymethyl cellulose on mild steel in acidic medium. Acta
1220
Physico-Chimica Sinica 24:2236-2243
1222
Banerjee S, Srivastava V, Singh MM (2012) Chemically modified natural polysaccharide as green corrosion inhibitor for mild steel in acidic medium. Corrosion Science 59: 35–41
ip t
1221
Behpour M, Ghoreishi SM, Khayatkashani M, Soltani N (2011) The effect of two oleo-gum resin
1224
exudate from Ferula assa-foetida and Dorema ammoniacum on mild steel corrosion in
1225
acidic media. Corrosion Science 53: 2489–2501
cr
1223
Bello M, Ocho N, Balsamo V, López-Carrasquero F, Coll S, Monsalve A, González G (2010)
1227
Modified cassava starches as corrosion inhibitors of carbon steel: An electrochemical and
1228
morphological approach. Carbohydrate Polymers 82: 561–568
us
1226
Bentiss F, Bouanis M, Mernari B, Traisnel M, Lagrenee M (2002) Effect of iodide ions on
1230
corrosion inhibition. of mild steel by 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole in
1231
sulfuric acid solution. Journal of Applied Electrochemistry 32: 671–678
1233
M
1232
an
1229
Bentrah H, Rahali Y, Chala A (2014) Gum Arabic as an eco-friendly inhibitor for API 5L X42 pipeline steel in HCl medium. Corrosion Science 82: 426–431 Biswas A, Pal S, Udayabhanu G (2015), Experimental and theoretical studies of xanthan gum
1235
and its graft co-polymer as corrosion inhibitor for mild steel in 15% HCl. Applied
1236
Surface Science 353:173 -183.
Ac ce pt e
d
1234
1237
Bouklah M, Hammouti B, Aouniti A, Benkaddour M, Bouyanzer A (2006) Synergistic effect of
1238
iodide ions on the corrosion inhibition of steel in 0.5 M H2SO4 by new chalcone
1239
derivatives. Applied Surface Science 252: 6236–6242
1240
Brindha T, Mallika J, Sathyanarayana MV (2015) Synergistic effect between starch and
1241
substituted piperidin-4-one on the corrosion inhibition of mild steel in acidic medium.
1242
Journal of Materials and Environmental Science 6: 191-200
1243 1244
Brown WH, Poon T (2005) Introduction to Organic Chemistry (3rd ed.) Wiley. ISBN 0-47144451-0
1245
Busch VM, Kolender AA, Santagapita PR, Buera MP (2015) Vinal gum, a galactomannan from
1246
Prosopis ruscifolia seeds: Physicochemical characterization. Food Hydrocolloids 51:
1247
495-502
44
Page 44 of 74
1248 1249
Caliskan N, Bilgic S (2000) Effect of iodide ions on the synergistic inhibition of the corrosion of manganese-14 steel in acidic media. Applied Surface Science 153: 128–133 Carneiro J, Tedimb J, Fernandesa SCM, Freire CSR, Silvestre AJD, Gandinia A, Ferreirab MGS,
1251
Zheludkevich ML (2012) Chitosan-based self-healing protective coatings doped with
1252
cerium nitrate for corrosion protection of aluminum alloy 2024. Progress in Organic
1253
Coatings 75: 8–13
ip t
1250
Carneiro J, Tedim J, Fernandes SCM, Freire CSR, Gandini A, Ferreira MGS, Zheludkevich M.L
1255
(2013a) Chitosan as a Smart Coating for Controlled Release of Corrosion Inhibitor 2-
1256
Mercaptobenzothiazole. ECS Electrochemical Letters 2(6): 2162-8726
us
cr
1254
Carneiro J, Tedim J, Fernandes SCM, Freire CSR, Gandini A, Ferreira MGS, Zheludkevich ML
1258
(2013b) Functionalized chitosan-based coatings for active corrosion protection. Surface
1259
& Coatings Technology 226: 51–59
an
1257
Chaires-Martínez L, Salazar-Montoya JA, Ramos-Ramírez EG (2008) Physicochemical and
1261
functional characterization of the galactomannan obtained from mesquite seeds (Prosopis
1262
pallida). European Food Research and Technology 227: 1669-1676
M
1260
Chakravarthy MP, Mohana KN (2014) Adsorption and corrosion inhibition characteristics of
1264
some nicotinamide derivatives on mild steel in hydrochloric acid solution. ISRN
1265
Corrosion doi.org/10.1155/2014/687276
Ac ce pt e
d
1263
1266
Chauhan K, Kumar R, Kumar M, Sharma P, Chauhan GS (2012) Modified pectin-based
1267
polymers as green antiscalants for calcium sulfate scale inhibition. Desalination 30:31–37
1268
Cheng S, Chen S, Liu T, Chang X, Yin Y (2007) Carboxymethyl chitosan-Cu2+ mixture as an
1269 1270 1271
inhibitor used for mild steel in 1.0 M HCl. Electrochimica Acta 52:5932–5938 Chung YC, Yeh, JY, Tsai CF (2011) Antibacterial characteristics and activity of water-soluble chitosan derivatives prepared by the maillard reaction. Molecules 16: 8504-8514
1272
Dang N, Wei YH, Hou LF, Li YG, Guo CL (2015) Investigation of the inhibition effect of the
1273
environmentally friendly inhibitor sodium alginate on magnesium alloy in sodium
1274
chloride solution. Materials and Corrosion 66: 1354-1362
1275 1276
Desai MN, Desai S.M (1970) Inhibition of the corrosion of A1-3S in NaOH. Corrosion Science 10: 233-237
45
Page 45 of 74
1277
Deyab MA (2015) Hydroxyethyl cellulose as efficient organic inhibitor of zinc-carbon battery
1278
corrosion in ammonium chloride solution: Electrochemical and surface morphology
1279
studies. Journal of Power Sources 280: 190-194
1281
Douiare M, Norton IT (2013) Designer colloids in structured food for the future (short survey). Journal of the Science of Food and Agriculture 93: 3147-3154
ip t
1280
Ebenso EE, Kabanda MM, Arslan T, Saracoglu M, Kandemirli F, Murulana LC, Singh AK,
1283
Shukla SK, Hammouti B, Khaled KF, Quraishi MA, Obot IB, Eddy NO (2012) Quantum
1284
chemical investigations on quinoline derivatives as effective corrosion inhibitors for mild
1285
steel in acidic medium. International Journal of Electrochemical Science 7: 5643 – 5676
us
cr
1282
Eddy NO, Ibok UJ, Ebenso EE (2010) Adsorption, synergistic inhibitive effect and quantum
1287
chemical studies on ampicillin and halides for the corrosion of mild steel. Journal of
1288
Applied Electrochemistry 40: 445-456
an
1286
Eddy NO, Odiongenyi AO, Ameh PO, Ebenso EE, (2012) Corrosion Inhibition Potential of
1290
Daniella Oliverri Gum Exudate for Mild Steel in Acidic Medium. International Journal
1291
of Electrochemical Science 7: 7425 – 7439
M
1289
Eddy NO, Ameh PO, Odiongenyi AO (2014) Physicochemical Characterization and Corrosion
1293
Inhibition Potential of Ficus Benjamina (FB) Gum for Aluminum in 0.1 M H2SO4.
1294
Portugaliae Electrochimica Acta, 32(3): 183-197
Ac ce pt e
d
1292
1295
Eduok UM, Umoren SA, Udoh AP (2012) Synergistic inhibition effects between leaves and stem
1296
extracts of Sida acuta and iodide ion for mild steel corrosion in 1 M H2SO4 solutions.
1297
Arabian Journal of Chemistry 5: 325–337
1298
Eduok U, Inam E, Umoren SA, Akpan IA (2013) Chemical and spectrophotometric studies of
1299
naphthol dye as an inhibitor for aluminium alloy corrosion in binary alkaline medium.
1300
Geosystem Engineering 16: 146-155
1301
Eduok UM, Khaled MM (2014) Corrosion protection of non-alloyed AIAI 316L concrete steel
1302
metal grade in aqueous H2SO4: Electroanalytical and surface analyses with Metiamide.
1303
Construction and Building Materials 68: 285–290
1304
Eduok UM, Khaled M (2015) Corrosion inhibition for low-carbon steel in 1 M
1305
H2SO4 solution by phenytoin: evaluation of the inhibition potency of another
1306
“anticorrosive drug”. Research on Chemical Intermediates 41: 6309-6324
46
Page 46 of 74
1307
Eid S, Abdallah M, Kamar EM, El-Etre AY (2015) Corrosion inhibition of aluminum and
1308
aluminum silicon alloys in sodium hydroxide solutions by methyl cellulose. Journal of
1309
Materials and Environmental Science 6: 892-901
1311 1312 1313
El-Haddad MN (2013) Chitosan as a green inhibitor for copper corrosion in acidic medium. International Journal of Biological Macromolecules 55:142–149
ip t
1310
EL-Haddad MN (2014) Hydroxyethyl cellulose used as an eco-friendly inhibitor for 1018 c-steel corrosion in 3.5% NaCl solution. Carbohydrate Polymers 112: 595–602
El-Sawy SM, Abu-Ayana YM, Abdel-Mohdy FA (2001) Some chitin/chitosan derivatives for
1315
corrosion protection and waste water treatments. Anti-Corrosion Methods and Materials
1316
48(4): 227-234
us
cr
1314
Fan B, Wei G, Zhang Z, Qiao N (2014) Preparation of supramolecular corrosion inhibitor based
1318
on hydroxypropyl-bcyclodextrin/octadecylamine and its anti-corrosion properties in the
1319
simulated condensate water. Anti-Corrosion Methods and Materials 61: 104– 111
1320
Fares MM, Maayta AK, Al-Mustafa JA (2012a) Corrosion inhibition of iota-carrageenan natural
1321
polymer on aluminum in presence of zwitterion mediator in HCl media. Corrosion
1322
Science 65: 223–230
1325 1326
M
d
1324
Fares MM, Maayta AK, Al-Qudah MM (2012b) Pectin as promising green corrosion inhibitor of aluminum in hydrochloric acid solution. Corrosion Science 60: 112–117
Ac ce pt e
1323
an
1317
Fekry AM, Mohamed RR (2010) Acetyl thiourea chitosan as an eco-friendly inhibitor for mild steel in sulphuric acid medium. Electrochimica Acta 55:1933–1939
1327
Feng Y, Lin X, Li H, He L, Sridhar T, Suresh AK, Bellare J, Wang H (2014a) Synthesis and
1328
characterization of chitosan-grafted BPPO ultrafiltration composite membranes with
1329
enhanced antifouling and antibacterial properties. Industrial Engineering Chemistry and
1330
Research 53: 14974−14981
1331 1332
Fiori-Bimbi MV, Alvarez PE, Vaca H, Gervasi CA (2015) Corrosion inhibition of mild steel in HCL solution by pectin. Corrosion Science 92:192–199
1333
Gabriel JS, Tiera MJ, Tiera VAO (2015) Synthesis, characterization, and antifungal activities of
1334
amphiphilic derivatives of diethylaminoethyl chitosan against Aspergillus flavus. Journal
1335
of Agricultural and Food Chemistry 63, 5725−5731
1336
Geethanjali R, Ali A, Sabirneeza F, Subhashini S (2014) Water-Soluble and biodegradable
1337
pectin-grafted polyacrylamide and pectin-grafted polyacrylic acid: Electrochemical 47
Page 47 of 74
1338
investigation of corrosion-inhibition behaviour on mild steel in 3.5% NaCl media. Indian
1339
Journal of Materials Science 2014, doi.org/10.1155/2014/356075 Gräfen H, Horn EM, Schlecker H, Schindler H (2002) Corrosion" Ullmann's Encyclopedia of
1341
Industrial Chemistry, Wiley-VCH: Weinheim, 2002.doi:10.1002/14356007.b01_08
1342
Grassino A, Halambek J, Djaković S, Brnčić S.R, Dent M, Grabarić Z (2016) Utilization of
1343
tomato peel waste from canning factory as a potential source for pectin production and
1344
application as tin corrosion inhibitor. Food Hydrocolloids, 52: 265–274.
cr
1346
Harek Y, Larabi L (2004) Corrosion inhibition of mild steel in 1 mol/dm3 HCl by oxalic Nphenylhydrazide N0 –phenylthiosemicarbazide. Chemistry in Industry 53:55-61
us
1345
ip t
1340
Hassan RM, Fawzy A, Ahmed GA, Zaafarany IA, Asghar BH, Takagi HD, Ikeda Y (2011)
1348
Kinetics and mechanism of permanganate oxidation of iota- and lambda-carrageenan
1349
polysaccharides as sulfated carbohydrates in acid perchlorate solutions. Carbohydrate
1350
Research 346: 2260–2267
an
1347
Hassan R, Zaafarany I, Gobouri A, Takagi H (2013) A revisit to the corrosion inhibition of
1352
aluminum in aqueous alkaline solutions by water-soluble alginates and pectates as
1353
anionic
1354
Doi.org/10.1155/2013/508596
M
1351
inhibitors.
International
Journal
of
Corrosion
d
polyelectrolyte
Hassan RM, Zaafarany IA (2013) Kinetics of corrosion inhibition of aluminum in acidic media
1356
by water-soluble natural polymeric pectates as anionic polyelectrolyte inhibitors.
1357
Materials 6: 2436-2451
1358
Ac ce pt e
1355
HESIS Fact Sheet; Wood Preservatives Containing Arsenic and Chromates; Hazard Evaluation
1359
System and Information Service
1360
(https://www.cdph.ca.gov/programs/hesis/Documents/arsen2.pdf)
1361
Hromádková Z, Malovikova A, Mozeš Š, Sroková IE, Ibringerová A (2008) Hydrophobically
1362
modified pectates as novel functional polymers in food and non-food applications.
1363
BioResources, 3: 71-78
1364
https://en.wikipedia.org/wiki/Chitosan
1365
https://en.wikipedia.org/wiki/Hydroxyethyl_cellulose
1366
Hussein MHM, El-Hady MF, Shehata HAH, Hegazy MA, Hefni HHH (2013) Preparation of
1367
some eco-friendly corrosion inhibitors having antibacterial activity from sea food waste.
1368
Journal of Surfactants and Detergents 16:233–242 48
Page 48 of 74
1369 1370
Jayalakshmi Μ, Muralidharan VS (1997) Inhibitors for aluminium corrosion in aqueous medium. Corrosion Reviews 15(3-4): 315-340 John S, Joseph A, Jose AJ, Narayana B (2015) Enhancement of corrosion protection of mild steel
1372
by chitosan/ZnO nanoparticle composite membranes. Progress in Organic Coatings 84:
1373
28–34
ip t
1371
Kabanda MM, Murulana LC, Ozcan M, Karadag F, Dehri I, Obot IB, Ebenso EE (2012)
1375
Quantum chemical studies on the corrosion inhibition of mild steel by some triazoles and
1376
benzimidazole derivatives in acidic medium. International Journal of Electrochemical
1377
Science 7: 5035 - 5056
1379
us
1378
cr
1374
Kalaivania R, Arasub PT, Rajendran S (2013) Inhibitive nature of carboxymethylcellulose with Zn2+ ion. Chemical Science Transactions 2: 1352-1357
Kayaa S, Tüzüna B, Kaya C, Obot IB (2015) Determination of corrosion inhibition effects of
1381
amino acids: Quantum chemical and molecular dynamic simulation study. Journal of the
1382
Taiwan Institute of Chemical Engineers, doi.org/10.1016/j.jtice.2015.06.009
1385 1386 1387 1388
M
under aerobic conditions. Nature 439: 187–191
Khairou KS, El-Sayed A (2003) Inhibition effect of some polymers on the corrosion of cadmium
d
1384
Keppler F, Hamilton JTG, Bra M, Röckmann T (2006) Methane emissions from terrestrial plants
in a hydrochloric acid solution. Journal of Applied Polymer Science 88:866–871
Ac ce pt e
1383
an
1380
Killaars, J, Finley, P (2001) SPE International Symposium on Oilfield Chemistry. Houston, Texas, SPE 65044
1389
Kim SRB, Choi YG, Kim JY, Lim ST (2015) Improvement of water solubility and humidity
1390
stability of tapioca starch film by incorporating various gums. LWT-Food Science and
1391
Technology doi.org/10.1016/j.lwt.2015.05.009
1392
Klinov IY (1962) New polymeric materials in anticorrosion technology. Trudy. Vsesoyuznoy
1393
Mezhvuzovskoy Nauchnoy Konferentsii po Voprosam Bor’by s Korroziyey (Translations
1394
of the Inter-Higher Educational Institute Scientific Conference on Questions of Fighting
1395
Corrosion). Gostoptekhizdat, Moskva, pp 296–303
1396
Li ML, Li RH, Xu J, Han X, Yao TY, Wang J (2014a) Thiocarbohydrazide-modified chitosan as
1397
anticorrosion and metal ion adsorbent. Journal of Applied Polymer Science DOI:
1398
10.1002/APP.40671.
49
Page 49 of 74
1399
Li M, Xu J, Li R, Wang D, Li T, Yuan M, Wang J (2014b) Simple preparation of aminothiourea-
1400
modified chitosan as corrosion inhibitor and heavy metal ion adsorbent. Journal of
1401
Colloid and Interface Science 417: 131–136
1403 1404 1405
Li R, Feke DL (2015) Rheological and kinetic study of the ultrasonic degradation of locust bean gum in aqueous saline and salt-free solutions. Ultrasonics Sonochemistry 27: 334–338
ip t
1402
Li X, Deng S (2015) Cassava starch graft copolymer as an eco-friendly corrosion inhibitor for steel in H2SO4 solution. Korean Journal of Chemical Engineering 32: 1-8
Li H, Li H, Liu Y, Huang X (2015) Synthesis of polyamine grafted chitosan copolymer and
1407
evaluation of its corrosion inhibition performance. Journal of the Korean Chemical
1408
Society 59: 142-147
us
cr
1406
Liu Y, Zou C, Yan X, Xiao R, Wang T, Li M (2015) β-Cyclodextrin modified natural chitosan as
1410
a green inhibitor for carbon steel in acid solutions. Industrial Engineering Chemistry and
1411
Research 54: 5664−5672
1413
Liu Y, Zou C, Li C, Lin L, Chen W (2016) Evaluation of β-cyclodextrin–polyethylene glycol as
M
1412
an
1409
green scale inhibitors for produced-water in shale gas well. Desalination 377: 28–33 Loto CA, Loto RT (2013) Effect of Dextrin and Thiourea Additives on the Zinc Electroplated
1415
Mild Steel in Acid Chloride Solution. International Journal of Electrochemical Science 8:
1416
12434–12450
1418 1419 1420 1421 1422
Ac ce pt e
1417
d
1414
Luckachan GE, Mittal V (2015) Anti-corrosion behavior of layer by layer coatings of crosslinked chitosan and poly(vinyl butyral) on carbon steel. Cellulose 22: 3275–3290 Manimaran M, Rajendran S, Manivannan M, Thangakani JA, Prabha AS (2013) Corrosion inhibition by carboxymethyl cellulose. European Chemical Bulletin 2: 494-498 Mishra RK, Sutar PB, Singhal JP, Banthia AK (2007) Graft copolymerization of pectin with polyacrylamide. Polymer-Plastics Technology and Engineering, 46: 1079–1085
1423
Mobin M, Khan MA, Parveen M (2011) Inhibition of mild steel corrosion in acidic medium
1424
using starch and surfactants additives, Journal of Applied Polymer Science 121: 1558–
1425
1565
1426 1427
Mohamed RR, Fekry AM (2011) Antimicrobial and anticorrosive activity of adsorbents based on chitosan Schiff’s base. International Journal of Electrochemical Science 6:2488–2508
50
Page 50 of 74
1428
Musa AY, Mohamad AB, Kadhum AAH, Takriff MS, Tien LT (2011) Synergistic effect of
1429
potassium iodide with pthalazone on the corrosion inhibition of mild steel in 1.0 M HCl.
1430
Corrosion Science 53: 3672-3677 Nada C, Katarina B, Sandra P (1996) The inhibition effect of pectin and ascorbic acid on the
1432
corrosion of tin in sodium chloride solution. 47th Annual Meeting of The International
1433
Society of Electrochemistry, Abstracts/The International Society of Electrochemistry
1434
(ed). - The Electrochemical Society, 1996. L6a-3. 47th Annual Meeting of The
1435
International Society of Electrochemistry, Veszprem-Balatonfured, Hungary, 1.-6.09.
1436
1996
cr
us
1437
ip t
1431
Nanaki SG, Kyzas GZ, Tzeremec A, Papageorgiou M, Kostoglou M, Bikiaris DN, Lambropoulou
1439
microparticles for the removal of pharmaceuticals from aqueous solutions. Colloids and
1440
Surfaces B: Biointerfaces 127: 256–265
1442
Synthesis and characterization of modified carrageenan
Obot IB, Obi-Egbedi NO, Umoren SA (2009a) Antifungal drugs as corrosion inhibitors for
M
1441
DA (2015)
an
1438
aluminium in 0.1 M HCl. Corrosion Science 51: 1868–1875 Obot IB, Obi-Egbedi NO (2010) Adsorption properties and inhibition of mild steel corrosion in
1444
sulphuric acid solution by ketoconazole: Experimental and theoretical investigation.
1445
Corrosion Science 52:198–204
Ac ce pt e
d
1443
1446
Obot IB, Ebenso EE, Kabanda MM (2013) Metronidazole as environmentally safe corrosion
1447
inhibitor for mild steel in 0.5 M HCl: Experimental and theoretical investigation. Journal
1448
of Environmental Chemical Engineering 1:431–439
1449
Obot IB (2014) “Recent Advances in Computational Design of Organic Materials for Corrosion
1450
Protection of Steel in Aqueous Media” in Developments in Corrosion Protection,
1451
INTECH, Croatia, p 123 – 151.
1452
Obot IB, Macdonald DD, Gasem ZM (2015) Density functional theory (DFT) as a powerful tool
1453
for designing new organic corrosion inhibitors. Part 1: An overview. Corrosion science
1454
99: 1- 30.
1455 1456
Octel-Starreon
Products:
http://web.archive.org/web/20050218035909/http://www.octel-
starreon.com/Products_RFA_Corrosion.htm
51
Page 51 of 74
1457
Okafor PC, Ikpi ME, Uwah IE, Ebenso EE, Ekpe UJ, Umoren SA (2008) Inhibitory action of
1458
Phyllanthus amarus extracts on the corrosion of mild steel in acidic media. Corrosion
1459
Science 50: 2310–2317 OSHA DATA; General_Facts
1461
https://www.osha.gov/OshDoc/data_General_Facts/hexavalent_chromium.pdf
1462
Patel PR, Pandya JM, Keemtilal (1981) Colloids as corrosion inhibitors for aluminium copper
1465
Peter A, Obot IB, Sharma SK (2015) Use of natural gums as green corrosion inhibitors: an
cr
1464
alloy in hydrochloric acid. Proceedings of Indian National Science Academy 47: 555-561
overview. International Journal of Industrial Chemistry 6: 153 – 164.
us
1463
ip t
1460
Prabakaran M, Ramesh S, Periasamy V, Sreedhar B (2015) The corrosion inhibition performance
1467
of pectin with propyl phosphonic acid and Zn2+ for corrosion control of carbon steel in
1468
aqueous solution. Research on Chemical Intermediates 41:4649–4671
1470 1471 1472
Qu D (2006) Behavior of Dinonylphenol Phosphate Ester and its influence on the oxidation of a Zn anode in alkaline solution. Journal of Power Sources 162: 706–712
M
1469
an
1466
Rabea EI, Badawy MET, Stevens CV, Smagghe G, Steurbaut W (2003) Chitosan as antimicrobial agent: Applications and mode of action. Biomacromolecules 4: 1457-1465 Rahim AA, Rocca E, Steinmetz EJ, Kassim MJ (2008) Inhibitive action of mangrove tannins and
1474
phosphoric acid on pre-rusted steel via electrochemical methods. Corrosion Science 50:
1475
1546−1550
Ac ce pt e
d
1473
1476
Raja PB, Fadaeinasab M, Qureshi AK, Rahim AA, Osman H, Litaudon M, Awang K (2013)
1477
Evaluation of green corrosion inhibition by alkaloid extracts of Ochrosia oppositifolia
1478
and Isoreserpiline against mild steel in 1 M HCl medium. Industrial & Engineering
1479
Chemistry Research 52: 10582–10593
1480
Rajendran S, Joany RM, Apparao BV, Palaniswamy N (2002) Corrosion inhibition by
1481
carboxymethyl cellulose-1-hydroxyethane-1, 1-diphosphonic acid-Zn2+ system. Bulletin
1482
of Electrochemistry 18: 25-28
1483 1484
Rajendran S, Sridevi SP, Anthony N, John AA, Sundearavadivelu M (2005) Corrosion behaviour of carbon steel in polyvinyl alcohol. Anti-Corrosive Methods and Materials 52:102–107
1485
Rajeswari V, Kesavan D, Gopiramanb M, Viswanathamurthi P (2013) Physicochemical studies
1486
of glucose, gellan gum, and hydroxypropyl cellulose—Inhibition of cast iron corrosion.
1487
Carbohydrate Polymers 95: 288–294 52
Page 52 of 74
1488
Ridhwan AM, Rahim AA, Shah AM (2012) Synergistic effect of halide ions on the corrosion
1489
inhibition of mild steel in hydrochloric acid using mangrove tannin. International Journal
1490
of Electrochemical Science 7: 8091–8104
1492
Rosliza R and Nik WBW (2010) Improvement of corrosion resistance of AA6061 alloy by tapioca starch in seawater. Current Applied Physics 10: 221–229
ip t
1491
Roy P, Karfa P, Adhikari U, Sukul D (2014) Corrosion inhibition of mild steel in acidic medium
1494
by polyacrylamide grafted Guar gum with various grafting percentage: Effect of
1495
intramolecular synergism. Corrosion Science 88: 246–253
cr
1493
Saidia N, Elmsellema H, Ramdania M, Chetouania A, Azzaouib K, Yousfia F, Aounitia A,
1497
Hammouti B (2015) Using pectin extract as eco-friendly inhibitor for steel corrosion in 1
1498
M HCl media. Der PharmaChemica, 7(5):87-94
us
1496
Sakai T, Sakamoto T, Hallaert J, Vandamme EJ (1993) Pectin, Pectinase, and Protopectinase:
1500
Production, Properties, and Applications. Advances in Applied Microbiology 39: 213–
1501
294
M
an
1499
Sangeetha Y, Meenakshi S, Sundaram CS (2015a) Corrosion mitigation of N-(2-hydroxy-3-
1503
trimethyl ammonium)propyl chitosan chloride as inhibitor on mild steel. International
1504
Journal of Biological Macromolecules 72: 1244–1249
d
1502
Sangeetha Y, Meenakshi S, Sundaram C (2016) Interactions at the mild steel acid solution
1506
interface in the presence of O-fumaryl-chitosan: Electrochemical and surface studies.
1507
Carbohydrate Polymers, 136: 38 – 45.
Ac ce pt e
1505
1508
Sangeetha Y, Meenakshi S, Sundaram CS (2016) Investigation of corrosion inhibitory effect of
1509
hydroxyl propyl alginate on mild steel in acidic media. Journal of Applied Polymer
1510
Science; DOI: 10.1002/APP.43004
1511
Sasikumar Y, Adekunle AS, Olasunkanmi LO, Bahadur I, Baskar R, Kabanda MM, Obot IB,
1512
Ebenso EE (2015) Experimental, quantum chemical and Monte Carlo simulation studies
1513
on the corrosion inhibition of some alkyl imidazolium ionic liquids containing
1514
tetrafluoroborate anion on mild steel in acidic medium. Journal of Molecular Liquids
1515
211: 105–118
1516 1517
Schweiger RG (1962) Acetyl Pectates and Their Reactivity with Polyvalent Metal Ions. Journal of Organic Chemistry 27: 1789
53
Page 53 of 74
1518
Shibad PR, Balachandra J (1976) Behaviour of titanium and its alloy with hydrofluoric acid in
1519
HCI and H2SO4 solutions with addition agents. Anti-Corrosion Methods and Materials
1520
23: 16–28 Smith AM (2001) The biosynthesis of starch granules. Biomacromolecules 2 (2): 335–41
1522
Solomon MM, Umoren SA, Udosoro II, Udoh AP (2010) Inhibitive and adsorption behaviour of
1523
carboxymethyl cellulose on mild steel corrosion in sulphuric acid solution. Corrosion
1524
Science 52: 1317–1325
ip t
1521
Sriram JG, Sadhir MH, Saranya M, Srinivasan A (2014) Novel Corrosion Inhibitors Based On
1526
Seaweeds for AA7075 Aircraft Aluminium Alloys. Chemical Science Review and Letters
1527
2: 402-407
1530 1531
us
Materials Science 3: 3995-4003
an
1529
Sugama T (1997) Oxidized potato-starch films as primer coatings of aluminium, Journal of
Sugama T, DuVall JE (1996) Polyorganosiloxane-grafted potato starch coatings for protecting aluminum from corrosion. Thin Solid Films 289: 39-48
M
1528
cr
1525
Suyanto, HDK, Ratih R, Leo SA (2015) Application chitosan derivatives as inhibitor corrosion
1533
on steel with fluidization method. Journal of Chemical and Pharmaceutical Research 7:
1534
260-267
1536
Talati JD, Modi RM (1976) Colloids as corrosion inhibitors for aluminium-copper alloy in
Ac ce pt e
1535
d
1532
sodium hydroxide. Anti-Corrosion Methods and Materials 23: 6─9
1537
Tang L, Li X, Mu G, Li L, Liu G (2006) Synergistic effect between 4-(2-pyridylazo) resorcin
1538
and chloride ion on the corrosion of cold rolled steel in 0.5 M sulfuric acid. Applied
1539
Surface Science 252: 6394–6401
1540 1541
Tawfik S.M (2015) Alginate surfactant derivatives as ecofriendly corrosion inhibitor for carbon steel in acidic environment. RSC Advances DOI: 10.1039/C5RA20340F
1542
Umoren SA, Obot IB, Ebenso EE, Okafor PC, Ogbobe O, Oguzie EE (2006) Gum arabic as a
1543
potential corrosion inhibitor for aluminium in alkaline medium and its adsorption
1544
characteristics. Anti-Corrosion Methods and Materials 53: 277–282
1545
Umoren SA, Ogbobe O, Ebenso EE (2006) Synergistic inhibition of aluminium corrosion in
1546
acidic medium by gum arabic and halide ions. Transactions of the SAEST (Society for
1547
Advancement of Electrochemical Science and Technology) 41: 74-81
54
Page 54 of 74
1548 1549
Umoren SA (2008) Inhibition of aluminium and mild steel corrosion in acidic medium using Gum Arabic. Cellulose 15:751–761 Umoren SA, Ogbobe O, Igwe IO, Ebenso EE (2008a) Inhibition of mild steel corrosion in acidic
1551
medium using synthetic and naturally occurring polymers and synergistic halide
1552
additives. Corrosion Science 50: 1998–2006
ip t
1550
Umoren SA, Obot IB, Ebenso EE, Obi-Egbedi N (2008b) Studies on the inhibitive effect of
1554
exudate gum from Dacroydes edulis on the acid corrosion of aluminium. Portugaliae
1555
Electrochimica Acta 26:199–209
cr
1553
Umoren SA, Eduok UM, Oguzie EE (2008c) Corrosion inhibition of mild steel in 1 M H2SO4 by
1557
polyvinyl pyrrolidone and synergistic iodide additives. Portugaliae Electrochimica Acta
1558
26: 533-546
us
1556
Umoren SA (2009) Synergistic Influence of gum arabic and iodide ion on the corrosion
1560
inhibition of aluminium in alkaline medium. Portugaliae Electrochimica Acta 27: 565-
1561
577
1563
M
1562
an
1559
Umoren SA., Obot IB, Obi-Egbedi NO (2009a) Raphia hookeri gum as a potential eco-friendly inhibitor for mild steel in sulfuric acid. Journal of Materials Science 44:274–279 Umoren SA, Obot IB, Ebenso EE, Obi-Egbedi NO (2009b) The Inhibition of aluminium
1565
corrosion in hydrochloric acid solution by exudate gum from Raphia hookeri.
1566
Desalination 247: 561–572
Ac ce pt e
d
1564
1567
Umoren SA, Ebenso EE (2009) Studies of the anti-corrosive effect of Raphia hookeri exudate
1568
gum-halide mixtures for aluminium corrosion in acidic medium. Pigment Resin
1569
Technology 37: 173–182
1570
Umoren SA, Ekanem UF (2010) Inhibition of mild steel corrosion in H2SO4 using exudate gum
1571
from Pachylobus edulis and synergistic potassium halide additives. Chemical
1572
Engineering Communications 197:1339–1356
1573
Umoren SA, Solomon MM, Udosoro II, Udoh AP (2010) Synergistic and antagonistic effects
1574
between halide ions and carboxymethyl cellulose for the corrosion inhibition of mild steel
1575
in sulphuric acid solution. Cellulose 17:635–648
1576
Umoren SA, Eduok UM, Solomon MM, Udoh AP (2011) Corrosion inhibition by leaves and
1577
stem extracts of Sida acuta for mild steel in 1 M H2SO4 solutions investigated by
1578
chemical and spectroscopic techniques. Arabian Journal of Chemistry, 55
Page 55 of 74
1579 1580 1581 1582
http://dx.doi.org/10.1016/j.arabjc.2011.03.008. Umoren SA, Banera MJ, Garcia TA, Gervasi CA, Mirıfico MV (2013) Inhibition of mild steel corrosion in HCl solution using chitosan. Cellulose 20: 2529 – 2545. Umoren SA, Eduok UM, Solomon MM (2014) Effect of polyvinylpyrrolidone–polyethylene glycol blends on the corrosion inhibition of aluminium in HCl solution. Pigment & Resin
1584
Technology 43: 299 – 313
ip t
1583
Umoren SA, Solomon MM (2015) Effect of halide ions on the corrosion inhibition efficiency of
1586
different organic species – A review. Journal of Industrial and Engineering Chemistry 21:
1587
81–100
us
cr
1585
Umoren S, Solomon MM, Ubon-Israel A, Eduok UM, Jonah AE (2015a) Comparative study of
1589
the corrosion inhibition efficacy of polypropylene glycol and poly (methacrylic acid) for
1590
mild steel in acid solution. Journal of Dispersion Science and Technology 36: 1721-1735
an
1588
Umoren SA, Obot IB, Madhankumar A, Gasem ZM (2015b) Performance evaluation of pectin as
1592
ecofriendly corrosion inhibitor for X60 pipeline steel in acid medium: Experimental and
1593
theoretical approaches. Carbohydrate Polymers 124: 280–291
1595
van de Velde F, DeRuiter GA (2005) Carrageenan: Polysaccharides. in: Biopolymers Online, Wiley-VCH Verlag GmbH & Co. KGaA, DOI: 10.1002/3527600035.bpol6009
d
1594
M
1591
Vathsala K, Venkatesha TV, Praveen BM, Nayana KO (2010) Electrochemical generation of Zn-
1597
chitosan composite coating on mild steel and its corrosion studies. Engineering 2: 580-
1598
584
1599 1600
Ac ce pt e
1596
Verbeken D, Diercka S, Dewttinck K (2003) Exudate gums: occurrence, production and applications (A review). Applied Microbiology & Biotechnology 10:1354–1457
1601
Wang L, Zhang C, Xie H, Sun W, Chen X, Wang X, Yang Z, Liu G (2015) Calcium alginate gel
1602
capsules loaded with inhibitor for corrosion protection of downhole tube in oilfields.
1603
Corrosion Science 90: 296–304
1604 1605 1606 1607
Yan X, Zou C, Qin Y (2014) A new sight of water-soluble polyacrylamide modified by βcyclodextrin as corrosion inhibitor for X70 steel. Starch/Stärke 66: 968–975 Zaafarany I (2006) Inhibition of acidic corrosion of iron by some carrageenan compounds. Current World Environment, 1(2): 101-108
56
Page 56 of 74
1608
Zaafarany I (2012) Corrosion Inhibition of aluminum in aqueous alkaline solutions by alginate
1609
and pectate water-soluble natural polymer anionic polyelectrolytes. Portugaliae
1610
Electrochimica Acta, 30: 419-426 Zaafarany IA, Khairou KS, Hassan RM (2009) Acid-catalysis of chromic acid oxidation of
1612
kappa-carrageenan polysaccharide in aqueous perchlorate solutions. Journal of Molecular
1613
Catalysis A: Chemical 302: 112–118
ip t
1611
Zheludkevich ML, Tedim J, Freire CSR., Fernandes SCM., Kallip S, Lisenkov A, Gandinia A,
1615
Ferreira MGS (2011) Self-healing protective coatings with ‘‘green’’ chitosan based pre-
1616
layer reservoir of corrosion inhibitor. Journal of Materials Chemistry 21: 4805–4812
1618
us
1617
cr
1614
Zou C, Yan X, Qin Y, Wang M, Liu Y (2014a) Inhibiting evaluation of b-Cyclodextrin-modified acrylamide polymer on alloy steel in sulfuric solution. Corrosion Science 85: 445–454 Zou C., Liu Y., Yan X., Qin Y., Wang M., Zhou L (2014b) Synthesis of bridged β-
1620
cyclodextrinepolyethylene glycol and evaluation of its inhibition performance in oilfield
1621
wastewater. Materials Chemistry and Physics 147: 521-527.
1623
M
1622
an
1619
1626 1627
Ac ce pt e
1625
d
1624
Table 1. Typical examples of inhibition systems involving exudate gums deployed for metal corrosion reduction in various aggressive media. Type of metal S/N Inhibitor system *Inhibitor type Corrosive media Method(s) of corros substrate Exudate gum 1. Gum Arabic ─ Aluminium/ mild 0.1 M H2SO4 Weight loss and t steel techniq 2. Gum Arabic in combination ─ Aluminium 0.1 M NaOH Weight loss and hyd with potassium iodide techniq 3. Gum Arabic ─ Aluminium 0.1 M NaOH Hydrogen evolution a techniq 4. Guar gum Mixed type Carbon steel (L-52 1 M H2SO4 Weight loss and po grade) containing NaCl polarization te 5. Exudate gum extracted from ─ Mild steel 0.1 M H2SO4 Weight loss, hydro Ficus glumosa thermometric techniq electron mic 6. Exudate gum extracted from ─ Aluminum alloy 1 M HCl GCMS and FTIR (d Ficus benjamina sheet the chemical compos exudate); weight l 7. Exudate gum extracted from ─ Zinc (A72357 0.1 M H2SO4 GCMS (determinatio 57
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Mild steel
9.
Exudate gum extracted from Acacia tree
Mixed type
Mild steel
10.
Exudate gum extracted from Ferula assa-foetida and Dorema ammoniacum
Mixed type
Mild steel
11.
Exudate gum extracted from Raphia hookeri Exudate gum extracted from Dacroydes edulis Polyacrylamide grafted guar gum
─
an
Aluminium (AA 1060 grade) Aluminium (AA 1060 grade) Mild steel
M
─ Mixed type
d
13.
ip t
Exudate gum extracted from Daniella olliverri
composition of the weight loss, hydroge thermometric techn electron mic 0.1 M HCl GCMS and FTIR (d the chemical compos exudate); weight l 0.5─2 M HCl and Weight loss, hydroge Potentiodynamic H2SO4 techniques; X-ray spectroscopy, Fourier red spectroscopy electron mic 2 M HCl Electrochemical spectroscopy, Pot polarization, scan microscopy; quan calculations (by se method/Austin Mode 0.1 M HCl Weight loss and t techniq 2 M HCl Weight loss and t metho 1 M HCl Weight loss techn transform infra-red; impedance spe Potentiodynamic scanning electron 1 M HCl Potentiodynamic p Electrochemical spectroscopy; Fourier red spectro 15% HCl Weight loss te Electrochemical spectroscopy, Pot polarization; scan microsc 0.5 M H2SO4 Weight loss, pote polarization and el impedance spectros electron mic
us
8.
12.
14.
Gum Arabic
Mixed type
15.
Xanthan gum and Xanthan gum-polyacrylamide conjugate
Mixed type
Mild steel
16.
Polyacrylamide grafted with Okra mucilage
Mixed but predominantly cathodic
Mild steel
Ac ce pt e
1628 1629 1630 1631 1632
grade)
cr
Acacia sieberiana
API 5L X42 pipeline steel
Metal corrosion inhibition by exudate gums are generally attributed to the adsorption of their chemical constituents on the metal surface via formation of protective film. *An inhibitor type for a metal substrate in a solution of an electrolyte is known on the basis of its Tafel behavior (by monitoring the effect of its presence on the anodic and/or cathodic reactions using the electrochemical potentiodynamic polarization technique that involves the application of potential within a given range versus the open-circuit potential at a given scan rate).
1633 1634 1635 58
Page 58 of 74
1636 Table 2. Typical examples of inhibition systems involving substituted cellulose and starch deployed for metal corrosion reduction in various aggressive media. S/N
Carboxymethyl cellulose and Hydroxyethyl cellulose Carboxymethyl cellulose
─
Type of metal substrate/ corrosive media
Method(s) of corrosion monitoring
cr
Mild steel/2 M H2SO4
Weight loss, hydrogen evolution and thermometric techniques.
an
Sodium carboxymethyl cellulose
Mixed type
Mild steel/1 M HCl
3.
Carboxymethyl cellulose in combination with potassium halides (KCl, KBr, KI)
─
Mild steel (AISI 1005 grade)/ 2 M H2SO4
4.
Carboxymethyl cellulose [Authors also studied poly(vinyl alcohol), poly(acrylic acid), sodium polyacrylate, poly-(ethylene glycol), pectin] Carboxymethyl cellulose in combination with 1hydroxyethanole-1,1diphosphonic acid─Zn2+ system.
Slightly cathodic at higher carboxymethyl cellulose concentrations Mixed type
Planar cadmium disc electrode/ 0.5 M HCl
Potentiodynamic polarization and electrochemical impedance spectroscopy.
Mild steel/ Neutral aqueous environment containing 60 ppm Cl─
Weight loss technique; [protective film has been analyzed by X ray diffraction (XRD) and FTIR]; Potentiodynamic polarization technique.
d
M
2.
5.
Reason for corrosi corrosion reduction is following re
ip t
*Inhibitor type
us
1.
Inhibitor system
Ac ce pt e
1637 1638
Weight loss techniques; potentiodynamic polarization, linear polarization resistance and electrochemical impedance spectroscopy. Weight loss and hydrogen evolution techniques.
Authors attributed chem via inherent functional g ─COOH) on the metal s reason for corrosion inh pointed out that the prot ─COOH at the carbony molecular adsorption on metal surface by electro Molecular adsorption on via inherent functional g
Inhibitor molecular a metal surface; Halide i both antagonism (Cl─ a synergism towards the of Carboxymethyl cellu Molecular adsorption on
Formation of prot (Zn(OH)2, Fe2+─HEDP ─CMC complex) films the metal substrate; co Diffraction and Fourie red spectroscopy
59
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Carboxymethyl cellulose ─Zn2+ binary system.
Mixed type; but dominantly anodic
Carbon steel/ Neutral chlorine ion (120 ppm Cl─) saturated media
7.
Carboxymethyl cellulose─Zn2+ binary system.
Mixed type; but predominantly cathodic.
Aluminium/ Ground water at pH 11
8.
Carboxymethyl cellulose─Zn2+ system.
─
Carbon steel/ Ground water at pH 11
9.
Hydroxypropyl cellulose [Authors also studied glucose and gellan gum] in combination with potassium iodide
Mixed type
cr us
Formation of protective surface (confirmed with microscope and atomic microscopy).
an
Rate of metal degradatio an inhibition synergism CMC; and also the form protective film on the m (confirmed with scannin microscopy). Cast iron/ 1 M Weight loss and Molecular adsorption on HCl potentiodynamic confirmed by Wide diffraction, Fourier tr polarization techniques, spectroscopy and sc electrochemical microscope; potas impedance demonstrated both spectroscopy. synergism towards the of Hydroxypropyl cellul Carbon steel (1018 Electrochemical Molecular adsorption on grade)/ 3.5% NaCl impedance (confirmed with sc spectroscopy, microscopy/ Energy potentiodynamic spectroscopy). polarization and electrochemical frequency modulation. Authors further explained inhibitor molecular adsorption and corrosion mechanism with DMol3 quantum chemical calculations. Mild steel/ 0.5 M Weight loss and Metal corrosion inhibit H2SO4 potentiodynamic to Hydroxyethyl cel polarization adsorption and elastic
M d
11.
Ac ce pt e
10.
Inhibition was attribut type protective film o confirmed by AFM; confirmed to be mad complex and Zn(OH)2 u
ip t
6.
technique. Weight loss and potentiodynamic polarization techniques, electrochemical impedance spectroscopy. Weight loss and potentiodynamic polarization techniques, electrochemical impedance spectroscopy. Weight loss technique and electrochemical impedance spectroscopy.
Hydroxyethyl cellulose
Mixed type
Hydroxyethyl cellulose in combination with potassium iodide
Mixed type
60
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techniques; electrochemical impedance spectroscopy
Hydroxyethyl cellulose
Mixed type
13.
Hydroxyethyl cellulose
Mixed type
Mild steel/ 1 and 1.5 M HCl; 0.5 M H2SO4
14.
15.
16.
Ac ce pt e
d
M
12.
an
us
cr
ip t
Quantum chemical calculations using the density functional theory (DFT) was employed to determine the relationship between molecular structure and inhibition efficiency. Weight loss technique; Potentiodynamic polarization and electrochemical impedance spectroscopy. Potentiodynamic polarization and electrochemical impedance spectroscopy. Potentiostatic polarization, electrochemical impedance spectroscopy, cyclic voltammetry and potentiodynamic anodic polarization techniques.
the steel substrate due this compound in th Potassium iodide enhan performance of the syste charged steel substrate inhibitor.
Methyl cellulose
Starch Starch in combination with 2,6-diphenyl-3methylpiperidin-4-one
Starch in combination with sodium dodecyl sulfate and
Cylindrical zinc substrate (Zinccarbon battery)/ 26% NH4Cl
Anodic
aluminum and aluminum silicon alloys/ 0.1 M NaOH
Mixed type
Mild steel/ 1 N HCl
Mixed type but predominantly 61
Mild steel/ 0.1M H SO
Weight loss measurements; Electrochemical Impedance Spectroscopy; Potentiodynamic polarization. Weight loss and potentiodynamic
Inhibitor molecular a metal surface.
Inhibitor molecular a metal surface (confirm transform Infra-red s scanning electron micro
Inhibitor molecular ads presence of methyl cellu of alloys.
Both compounds synerg steel corrosion by co adsorption at the metal claims of the formation confirmed with Fourie red spectroscopy).
Both natural and syn synergistically inhibited
Page 61 of 74
predominantly anodic
H2SO4
potentiodynamic polarization.
─
XC 35 carbon steel/ Alkaline 200 mg/l NaCl
Electrochemical Impedance Spectroscopy.
synergistically inhibited combine molecular a metal surface. Inhibitor molecular ads presence of starch at th (confirmed with microscopy).
ip t
17.
sodium dodecyl sulfate and cetyl trimethyl ammonium bromide Activated and carboxymethylated starch cassava starch.
cr
Corrosion inhibition in concentration of starch carboxymethylated star performed inhibitor d substitution of its active AA6061 alloy/ Gravimetric, Physical coverage as w seawater potentiodynamic adsorption at the metal s polarization, with scanning electr linear Theoretical approach polarization inhibition was also resistance and correlating inhibiting electrochemical molecular structure. impedance spectroscopy. Cold rolled steel/ 1 Weight loss, Improved protection fr M H2SO4 potentiodynamic is due to synergy polarization, compounds by com electrochemical adsorption at the metal s impedance with scanning electron m spectroscopy.
Tapioca starch
Mixed type
19.
Acryl amide grafted cassava starch
20.
Polyorganosiloxane-grafted potato starch coatings
Mixed type though predominantly anodic and cathodic at lower and higher temperatures, respectively. ─
21.
Cerium (IV) ammonium nitrate modified potatostarch
M
d
1640
Ac ce pt e
1639
an
us
18.
─
Aluminium/ neutral electrolyte
EIS and saltspray resistance for 288 h 6061─T6 Salt-spray tests, aluminium/ neutral EIS and surface electrolyte analytical techniques (FTIR and XPS).
Improved protection w polyorganosiloxane poly polysaccharide coated o Improved protective p composite was attribute of cerium-bridged carbo by carboxylate function ions at the metal/coating
1641 1642 1643
62
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1644 1645 1646
ip t
1647 1648
cr
1649
us
1650 1651
Pectic acid/Pectin/Pectate Commercial pectin extracted Mixed type; but from apple dominantly cathodic.
X60 pipeline steel/ 0.5 M HCl
Weight loss and Corrosion inhibition potentiodynamic attributed to the adso polarization later formation of pro techniques, film on the metal sub electrochemical (confirmed by scanni impedance microscopy, Fourier spectroscopy. infra-red spectroscop contact angle measur Quantum chemical calculation (density functional theory (DFT)) results provide useful insights into the active sites and reactivity parameters governing the corrosion inhibition with pectin. Weight loss technique Corrosion inhibition was attributed to its a on the metal surface, forming protective fi confirmed by scannin microscopy. Weight loss and Corrosion inhibition potentiodynamic by geometric blockin polarization chemisorbed inhibitiv
d
1.
Inhibitor system
Reason for cor Method(s) of inhibition/ corrosion corrosion monitoring is attributed to the reason(s)
Type of metal substrate/ corrosive media
*Inhibitor type
M
S/N
an
Table 3. Typical examples of inhibition systems (involving pectic acid/pectin/pectates, chitosan and carrageenan) deployed for metal corrosion reduction in various aggressive media.
Ac ce pt e
1652 1653
2.
Pectin extracted from citrus peel
─
Aluminium/ 0.5─2 M HCl
3.
Pectin extracted from fresh lemon peel
Mixed type
Mild steel/ 1 M HCl 63
Page 63 of 74
Mixed type; but dominantly cathodic
Tin/ 2% NaCl, 1% acetic acid and 0.5% citric acid solution
cr
Pectin extracted from tomato waste
d
M
an
us
4.
chemisorbed inhibitiv Complex-type specie metal surface. These pectin─Fe2+ ion com formed during the co reaction (confirmed w spectroscopic (UV/V scanning electron mi analyses). Nuclear magnetic Inhibitor molecular resonance, Fourier on the metal surface. transform infra-red spectroscopic techniques were employed to characterize the pectin extracted and compared with a standard.
ip t
polarization techniques, electrochemical impedance spectroscopy.
Pectin extracted from cladodes of Opuntia ficus indica
Mixed type; but dominantly cathodic
Mild steel/ 1 M HCl
6.
Pectin [propyl phosphonic acid and Zn2+]
Mixed type
Carbon steel/ 60 ppm chloride solution
Ac ce pt e
5.
Electrochemical impedance spectroscopy and potentiodynamic polarization techniques were employed for the corrosion test. Weight loss, Adsorption of the inh potentiodynamic organic matter on the polarization surface; and the form techniques, protective film at the electrochemical solution interface. impedance spectroscopy. Weight loss, Corrosion inhibition potentiodynamic attributed to the form polarization protective film on the techniques, the carbon steel in th electrochemical aqueous medium; Sy impedance inhibition due to the spectroscopy. pectin, along with pr phosphonic acid and (confirmed with Four transform infrared sp atomic force microsc scanning electron mi and X-ray photoelect spectroscopy).
64
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Tin/ Neutral NaCl solution
8.
Pectin-g-polyacrylamide and Pectin-g-polyacrylic acid grafted polymers.
Mixed type; but dominantly cathodic
Mild steel/ 3.5% NaCl
an M d 10.
Ac ce pt e
9.
ip t
Cathodic type
cr
Pectin─ascorbic acid binary system
us
7.
Authors suggested th protective film must consisted of [Fe3+)/F propyl phosphonic ac complex, Zn(OH)2, a hydroxides and oxide Weight loss and The inhibitory effect potentiodynamic inhibitor system was polarization to the formation of p techniques. complex at the tin/so interface. Pectin-gInhibition was due th polyacrylamide and of protective film on Pectin-g-polyacrylic surface (confirmed w acid grafted polymers transform Infra-red s were synthesized from and scanning electron pectin, acrylamide, microscopy. and acrylic acid as precursors.
Pectate (with alginate) anionic polyelectrolytes
─
Aluminium/ 4 M NaOH
Sodium pectate (with sodium alginate)
─
Aluminium/ 4 M NaOH
Characterization of the synthesized grafted polymer: Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyser (TGA), and scanning electron microscopy (SEM). Corrosion test: Potentiodynamic polarization techniques, electrochemical impedance spectroscopy , and then surface analytical evaluations. Weight loss and hydrogen evolution techniques.
Weight loss and hydrogen evolution techniques.
Corrosion inhibition attributed the chemic adsorption via hydrox of the polymer anion polyelectrolytes form between the polymer metal surface. Same as Zaafaran
65
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Pectate anionic polyelectrolyte
─
Aluminium/ 1 M HCl
12.
Calcium alginate gel capsules loaded with Imidazoline quaternary ammonium salt
-
P110 steel/ CO2 saturated 3.5 wt % NaCl
Mixed type
cr
Chitosan
us
14.
Mild steel/ 0.1 M Weight loss, HCl potentiodynamic polarization techniques, electrochemical impedance spectroscopy. Copper/ 0.5 M Weight loss, HCl potentiodynamic polarization techniques, electrochemical impedance spectroscopy and electrochemical frequency modulation techniques.
an
Mixed type
16.
Ac ce pt e
d
M
13.
Chitosan and substituted/modified chitosans Chitosan
15.
Same as Zaafaran
Improved corrosion i was attributed to the release of the imidaz inhibitor at the metal interface (surface ads was confirmed with s electron microscopy)
ip t
11.
techniques. Weight loss and hydrogen evolution techniques. Ultraviolet–visible spectrophotometry, scanning electron microscopy, electrochemical impedance spectroscopy.
Carboxymethyl chitosan─Cu2+
Mixed type
Acetyl─thiourea─chitosan conjugate polymer
Mixed type
Mild steel/ 1 M HCl
Quantum chemical calculations was also used to correlate the corrosion inhibition with the molecular structure of chitosan. Weight loss, potentiodynamic polarization techniques, electrochemical impedance spectroscopy.
Mild steel/ 0.5 M Potentiodynamic H2SO4 polarization, electrochemical impedance spectroscopy.
Chemical adsorption on the metal surface concluded as the cau corrosion inhibition ( with surface analytic techniques).
Inhibition was due th of protective film on surface (confirmed w transform Infra-red s and scanning electron microscopy.
Corrosion inhibition steel in the presence mixture was attribute molecular adsorption chitosan, and its inhi mechanism was furth investigated with conductometry. Scanning electron mi was deployed to stud surface morphology o substrate, in terms of prevalence of deep lo and the formation of
66
Page 66 of 74
Chitosan─crotonaldehyde schiff’s base
Mixed type
AZ91E alloy/ Artificial sea water
─
Galvanized steel/ 3 wt% NaCl
Heptanoate anions encapsulated into a chitosan─modified beidellite coating
19.
Synthesized methyl acrylate grafted and triethylene tetramine/ethylene diamine chitosan copolymers
Cathodic type
20.
Thiocarbohydrazide graft chitosan
Mixed type
The improved corros inhibition for this cla coating was attribute leaching of hepatano Diffuse reflectance the metal/coating inte infrared Fourier thereby preventing th passage of corrosive transform ions towards the met spectroscopy (DRIFTS), TG coupled MS and XRD techniques. Carbon steel Weight loss, Corrosion inhibition attributed to the dens (Q235-grade)/ potentiodynamic 5% HCl polarization “sustained-release” n technique, film on the electrode electrochemical (confirmed by scanni impedance microscopy). spectroscopy. 304 steel/ Copper Charaterization of the Corrosion inhibition sheets/ 2% acetic inhibitor: Fourier attributed to the form acid transform infrared protective film forme spectroscopy, steel surface (confirm scanning electron mi elemental analysis, thermal gravity analysis and differential scanning calorimetry,
22.
M d
Ac ce pt e
21.
Thiosemicarbazide and thiocarbohydrazide modified chitosan derivatives β-Cyclodextrin modified natural chitosan
an
us
cr
18.
Potentiodynamic polarization, electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy.
ip t
17.
and the formation of film, in the absence a presence of inhibitor respectively. Corrosion inhibition attributed to inhibitor adsorption at the met
Mixed type
Same as Li et al. (2014a).
Mixed type
Low carbon steel/ 0.5 M HCl
Corrosion test: Potentiodynamic polarization. Same as Li et al. Same as Li et al. (201 (2014a). Weight loss, potentiodynamic polarization technique, electrochemical impedance spectroscopy.
Corrosion inhibition attributed to inhibitor adsorption and the fo protective film on the surface (confirmed w scanning electron mi
67
Page 67 of 74
Coating caused a huge displacement in both redox currents (Mixed-type).
Coated mild steel Fourier transform substrates/ 0.5 M infra-red H2SO4 spectroscopic and scanning electron microscopic techniques were employed for surface characterization of the film after electrodeposition and before corrosion test.
Corrosion inhibition attributed to the barri the passage of corros sulphate ions through protective film coatin metal surface (the su morphology of the co conducted with scann electron microscopy)
ip t
Chitosan deposited on mild steel substrates by solution electrophoresis via the application of a 15 V potential for 15 mins in a binary solution of chitosan/acetic acid with glutaraldehyde employed as the cross linker.
cr
23.
─
Aluminium alloy (AA 2024 grade)/ 0.05 M NaCl
M
Self-healing chitosan-based hybrid coating doped with cerium ions (corrosion inhibitors)
Ac ce pt e
d
24.
an
us
Corrosion test: Potentiodynamic polarization technique, electrochemical impedance spectroscopy. Optical microscopy, SVET, scanning electron microscopy/Energy dispersive X-ray and Fourier transform infra-red spectroscopic techniques were used in analyzing the undoped chitosan, and Ce-doped chitosan coating, before and after immersion in the solution of the electrolyte after different exposure period in 0.05 M NaCl solution.
25.
Chitosan/Zn composite coating electrodeposited on mild steel from zinc sulphate/sodium chloride binary solution
─
Mild steel/ 3.5 wt% NaCl
The encapsulated Cs as corrosion inhibitor bulk of the coating th enhancing the coatin mechanical and prote strength; and also to needed self-healing a specific microcrack s
Corrosion test: Electrochemical impedance spectroscopy. Weight loss and Corrosion inhibit potentiodynamic attributed to the polarization corrosive ions fro technique, through the prote coated on the me electrochemical impedance (confirmed with microsco spectroscopy; salt electron spray test. enhanced corrosion
68
Page 68 of 74
spray test.
Nanostructured chitosan/ZnO nanoparticles.
28.
Chitosan (shrimp shell waste) modified to as water soluble chitosan derivatives (2-N,Ndiethylbenzene ammonium chloride N-oxoethyl chitosan and 12ammonium chloride N-oxododecan chitosan)
Mild steel/ 1 M HCl
ip t
27.
Superior barrier characteristics were attributed to inhibition of both cathodic and anodic reactions (Mixed type) Cathodic type
Mild steel/ 0.1 N HCl
cr
Chitosan grafted nanogels.
Potentiodynamic polarization technique, electrochemical impedance spectroscopy.
30.
31.
Weight loss technique
d
Carbon steel/ 1 M HCl
Ac ce pt e
29.
─
M
an
us
26.
enhanced corrosion for this coating was as being due to the Zn2+ ions in the coati Potentiodynamic Corrosion inhibition polarization technique nanogel was attribute and electrochemical formation of active p impedance film carrying chitosa at the metal/solution spectroscopy. (confirmed with scan electron microscopy)
Carboxymethyl chitosan─benzaldehyde and carboxy methyl chitosan─urea─glutaric acid Mercaptobenzothiazolecontrolled release chitosan─based coating
─
Mild steel/ 2% NaCl
─
Aluminum alloy (AA 2024 grade)/ 0.05 M NaCl.
Electrochemical impedance spectroscopy
Chitosan coatings doped with cerium nitrate.
─
Aluminum alloy (AA 2024 grade)/ 0.05 M NaCl
Electrochemical impedance spectroscopy.
Fluidization
Improved metal protection was re compacted films in t of ZnO, and the fo nanofilms on s concluded as the prin of corrosion inhibiti and this was charact UV–vis, Fourier tran red spectroscopy diffraction and electron microscop Dispersive X-ray spe Corrosion inhibition reported as being init changes in the orient substituted groups an degree of overlapping hydrogen bonding wi same molecule.
Molecular adsorption chitosan on the meta was concluded as the of steel corrosion inh Corrosion inhibition attributed to molecul adsorption of the inh the metal surface. The improved corros inhibition for this cla coating was attribute leaching of mercaptobenzothiazo metal/coating interfa It was observed that t layer worked as a res cationic Ce3+ corrosio due to the complexat
69
Page 69 of 74
NaCl
Modified chitosan surfactants
Mixed type
API 65 pipeline steel/ 1 M HCl
Potentiodynamic polarization technique.
ip t
32.
due to the complexat with chitosan amino which prevented its uncontrollable and fa Corrosion inhibit attributed to adsorption of the in the metal surface.
N-(2-hydroxy-3-trimethyl ammonium)propyl chitosan chloride
Cathodic type
34.
O-fumaryl-chitosan
Mixed type
35.
Layer-by-layer chitosan/poly vinyl butyral coating
Mild steel/ 1 M HCl
M
an
33.
us
cr
Quantum chemical calculations was also used to correlate the corrosion inhibition with the molecular structure of chitosan. Weight loss and potentiodynamic polarization technique, electrochemical impedance spectroscopy.
35.
Ac ce pt e
d
Mild steel/ 1 M HCl
Carrageenan i─carrageenan
─
Weight loss and potentiodynamic polarization technique, electrochemical impedance spectroscopy.
Mild steel/ 0.3 M Electrochemical (EIS aerated NaCl and potentiodynamic) solution. and surface analytical (SEM and Raman spectroscopy) techniques.
Corrosion inhibition attributed to its adsor the metal surface, the forming protective fi (confirmed with Four transform infra-red s and scanning electron microscopy). Corrosion inhibition attributed to its adsor the metal surface, the forming protective fi (confirmed with Four transform infra-red s and scanning electron microscopy, X-ray di and Atomic force mi Barrier protection by coating was attribute chitosan middle layer sandwiched between butyral bilayers on th substrate, as well as t incorporating glutara within the chitosan la
Formation of passive (Fe3O4 and -Fe2O3 o
─
Aluminium/ 2 M HCl
Weight loss technique.
Scanning electron mi demonstrated smooth and relatively cohere adsorption layers of t on the metal surface solution.
70
Page 70 of 74
36.
Anodic type
Low carbon steel/ 1 M HCl
Weight loss and galvanostatic polarization techniques.
Corrosion inhibition attributed to the bloc steel surface by carra molecular adsorption
Neither cathode nor anode were predominantly polarized.
2.
Dextrin (in the presence of Fe+3,Cu+2 and Ni+2)
─
3.
Dextrin (including acacia, gelatin, agar agar, tragacanth and glue) Dextrin and Thiourea
─
Al/Cu alloy/ 0.1─1.0 N HCl
d
─
Titanium and titanium alloy/ 20% HC1 and H2SO4 Aluminiumcopper alloy/ 0.11 M NaOH Dextrin and Thiourea Additives on the Zinc Electroplated Mild Steel/ acid chloride electrolyte
β-Cyclodextrin-modified acrylamide polymer
Mixed type inhibitor system
X70 steel/ 0.5 M H2SO4
5.
β-cyclodextrinepolyethylene glycol
Mixed type inhibitor system
Q235 carbon steel/ 0.5 M HCl
6.
Polyacrylamide modified βcyclodextrin composite
Mixed type inhibitor system
X70 steel/ 0.5 M H2SO4
4.
cr
Dextrin Dextrin (including acacia, gelatin, agar and glue)
Method(s) of corrosion monitoring
Weight loss potentiodynamic polarization techniques
us
1.
Inhibitor type
an
Inhibitor system
M
S/N
Type of metal substrate/ corrosive media
ip t
Table 4. Examples of inhibition systems (involving dextrin, alginates and their derivatives) deployed for metal corrosion reduction in various aggressive media.
Ac ce pt e
1654 1655
i,k,µ─carrageenan
Reason for co inhibition/ corrosio is attributed to th reason(s
and Corrosion inhibition attributed to the ads the formation of pro on the metal.
Open circuit potential Corrosion inhibition measurements attributed to the ads the metal surface. Weight loss
Corrosion inhibition attributed to the ads the metal surface. Adhesion test and The electroplating p SEM/EDS revealed densely pa crystals on steel wit with different surfac morphology for eac period under study. combination with th additive demonstrat remarkable superior at the highest platin compared to the res matrices as examine EDS. Potentiodynamic Corrosion inhibition polarization, EIS and attributed to the mo SEM coupled with adsorption on the m EDS. EIS, potentiodynamic Corrosion inhibition polarization and attributed to the mo weight loss adsorption on the m techniques. Weight loss, Corrosion inhibition Potentiodynamic attributed to the mo polarization, EIS and adsorption on the m
71
Page 71 of 74
A1-3S in 0.2 N NaOH
Mixed type inhibitor system
aluminium alloy (AA 7075 grade) in 3.5 wt% NaCl
11.
Na alginate
12.
13.
Apple derived alginatewater-soluble natural polymer anionic polyelectrolytes (including pectate). Na alginate
14.
Alginate cationic surfactant
15.
Ca aginate gel loaded with imidazoline quaternary ammonium salts
Carbon steel corrosion/ 0.5 M HCl
─
Mixed corrosion inhibition system (but anodically controlled) Mixed corrosion inhibition system (but cathodically controlled) ─
Anodization/ anodic and cathodic polarization Potentiodynamic polarization technique
us
Na alginate extracts from a brown seaweed (Turbinaria ornate).
Ac ce pt e
10.
ip t
─
Weight loss, potentiodynamic polarization, EIS and SEM/EDS techniques.
cr
Alginate Na alginate
Carbon steel corrosion/ 0.5 M HCl
an
8.
9.
Q235A steel/CO2 saturated deionized water at 5.6 pH
Chitosan-grafted βcyclodextrin composite
Mixed type inhibitor system (but predominantly anodic than cathodic) Mixed type inhibitor system
M
Hydroxypropyl-bcyclodextrin/ octadecylamin supramolecular complex
d
7.
SEM. EIS and potentiodynamic polarization.
Pure aluminum/ 4 M NaOH
AZ31 alloy grade/ 3.5 wt% NaCl
Carbon steel/ 1 M HCl
P110 steel/ CO2saturated 3.5 wt.% NaCl
Corrosion inhibition attributed to the for passive inhibitor lay hydrophobic octade inherent in the supr complex at the meta Corrosion inhibition steel in the presence composite was also molecular adsorptio composite.
Molecular adsorptio
Authors attributed c inhibition to adsorp functional groups fo alginate extract; this confirmed with FTI spectroscopy. Molecular adsorptio metal surface.
Weight loss, potentiodynamic polarization, EIS and electrochemical frequency modulation (EFM). Gravimetric and Molecular adsorptio gasometric techniques. metal surface.
Polarization, EIS, SEM coupled EDS and FTIR spectroscopy
Authors attributed c inhibition to molecu adsorption and subs formation of compa (freshly generated m hydroxide) on the m Gravimetric, Molecular adsorptio electrochemical, EDX metal surface. and SEM techniques
Ultraviolet–visible spectrophotometry, SEM and EIS techniques.
The improved prote presence of this com attributed to the aut release of imidazoli inhibitors at the me interface. BaSO4 wa encapsulated with a
72
Page 72 of 74
Hydroxyl propyl alginate
Mixed type inhibitor system
Mild steel/1 M HCl
cr
1656
d
M
an
us
Table 5. Bioploymer-halide inhibition systems deployed for metal corrosion studies in various aggressive media. Type of metal Reason for corrosio Inhibitor system (halide S/N substrate/ Method(s) of corrosion monitoring in the presence of type) corrosive media (Halide eff Aluminium/ 0.1 Weight loss and hydrogen evolution Synergism (wi Gum Arabic in combination 1. M NaOH. techniques. with potassium iodide. 2. Carboxymethyl cellulose in Mild steel (AISI Weight loss and hydrogen evolution Inhibitor molecular a combination with potassium 1005 grade)/ 2 M techniques. the metal surface; halides (with KCl, KBr, KI). H2SO4. demonstrated both (Cl─ and Br─ ions) a towards the inhibitio Carboxymethyl cellul 3. Hydroxypropyl cellulose Cast iron/ 1 M Weight loss and potentiodynamic KI demonstrated bot polarization techniques, and synergism t [Authors also studied HCl. electrochemical impedance inhibition pote glucose and gellan gum] in combination with KI. spectroscopy. Hydroxypropyl cellul 4. Hydroxyethyl cellulose in Mild steel/ 0.5 M Weight loss and potentiodynamic Potassium iodide e polarization techniques; inhibition performa combination (with KI). H2SO4. electrochemical impedance system by bridging spectroscopy steel substrate and inhibitor (synergism). Quantum chemical calculations using the density functional theory (DFT) was employed to determine the relationship between molecular structure and inhibition efficiency. 5. Hydroxypropyl Aluminium (AA Weight loss and potentiodynamic Synergism (with KI). methylcellulose (with KI). 1060 type)/ 0.5 M polarization techniques, H2SO4. electrochemical impedance spectroscopy.
Ac ce pt e
1657 1658
Weight loss, electrochemical (Polarization and EIS) techniques, AFM, SEM and FTIR.
ip t
16.
encapsulated with a imidazoline compos to aid sinking and c retardation was wel Molecular adsorptio metal surface.
6.
Hydroxyethyl Cellulose
Quantum chemical calculations (by DFT) was also used to correlate the corrosion inhibition with the molecular structure of Hydroxypropyl methylcellulose. Aluminium (AA Same as Arukalam et al. (2014a). Synergism (with KI) 73
Page 73 of 74
9. 10.
11.
Hydrogen evolution and thermometric techniques. Weight loss, hydrogen evolution and thermometric techniques.
Exudate gum extracted from Pachylobus edulis (with KCl, KBr, KI).
Mild steel/ 2 M H2SO4.
Hydrogen evolution and thermometric Synergism (with KBr methods. Antagonism (with KC
Synergism (with KBr Antagonism (with KC Synergism (with KBr Antagonism (with KC
an
1660
Ac ce pt e
d
M
1661
1663
Synergism (with KI)
Aluminium/ 0.1 M NaOH. Aluminium/ 0.1 M HCl.
1659
1662
Synergism (with KI)
Gum Arabic (with KCl, KBr, KI). Raphia hookeri exudate gum (with KCl, KBr, KI).
cr
8.
Hydroxypropyl methylcellulose (with KI). Ethyl Hydroxyethyl Cellulose (with KI).
us
7.
1060 type) and Mild Steel/ 0.5 M H2SO4. Mild steel/ 0.5 M Same as Arukalam et al. (2014a). H2SO4. Mild steel/ 1 M Same as Arukalam et al. (2014a). H2SO4.
ip t
(with KI).
74
Page 74 of 74