Effect of 1-(3-phenoxypropyl) pyridazin-1-ium bromide on steel corrosion inhibition in acidic medium

Accepted Manuscript Effect of 1-(3-phenoxypropyl) pyridazin-1-ium bromide on steel corrosion inhibition in acidic medium F. El-Hajjaji, M. Messali, M.V. Martínez de Yuso, E. Rodríguez-Castellón, S. Almutairi, Teresa J. Bandosz, M. Algarra PII: DOI: Reference:

S0021-9797(19)30136-5 https://doi.org/10.1016/j.jcis.2019.01.113 YJCIS 24602

To appear in:

Journal of Colloid and Interface Science

Received Date: Revised Date: Accepted Date:

7 September 2018 24 January 2019 25 January 2019

Please cite this article as: F. El-Hajjaji, M. Messali, M.V. Martínez de Yuso, E. Rodríguez-Castellón, S. Almutairi, T.J. Bandosz, M. Algarra, Effect of 1-(3-phenoxypropyl) pyridazin-1-ium bromide on steel corrosion inhibition in acidic medium, Journal of Colloid and Interface Science (2019), doi: https://doi.org/10.1016/j.jcis.2019.01.113

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Effect of 1-(3-phenoxypropyl) pyridazin-1-ium bromide on steel corrosion inhibition in acidic medium F. El-Hajjajia,*, M. Messalib, M.V. Martínez de Yuso c, E. Rodríguez-Castellónd, S. Almutairie, Teresa J. Bandoszf, M. Algarrag,*

a

b

c

d e f

g

Laboratory of Engineering, Electrochemistry Modeling and environment Faculty of sciences. University Sidi Med Ibn Abdallah. Fez, Morocco. Chemistry Department, Faculty of Science, Taibah University, 30002, Al-Madinah Al-Mounawwara, Saudi Arabia X-Ray Photoelectron Spectroscopy Lab. Central Service to Support Research Building (SCAI). University of Málaga. 29071 Málaga, Spain Department of Inorganic Chemistry, Faculty of Science, University of Málaga, 29007 Málaga, Spain King Abdulaziz City for Science and Technology, Riyadh 11442, P. O. Box 6086, Saudi Arabia. Department of Chemistry and Biochemistry, The City College of New York, 160 Convent Ave, New York, NY 10031, USA. CQM-Centro de Química da Madeira. Universidade da Madeira. Campus da Penteada. 9020-105 Funchal. Portugal.

*Corresponding authors: E-mail: [email protected] (F.El-Hajjaji) and [email protected] (M. Algarra).

1

ABSTRACT The effect of 1-(3-phenoxypropyl) pyridazin-1-ium bromide, a new pyridazinium derivative, on steel corrosion in a HCl (1M) solution was analyzed using electrochemical impedance and XPS spectroscopy. Experimental results indicated that the inhibition efficiency increased with an increase in an inhibitor concentration. Electrochemical impedance spectroscopy measurements revealed that an increase in the immersion time of steel in an acidic medium from 1 to 12 h and further to 24 h decreased the charge transfer resistance (R ct) and thus decreased the inhibition efficiency. The SEM and XPS analyses linked the inhibition effect to the adsorption of the

inhibitor

(1-(3-phenoxypropyl) pyridazin-1-ium bromide) on the steel surface Keywords: Corrosion inhibition; Steel; Surface adsorption; Charge transfer resistance

2

1. Introduction The corrosion of metals affects various industries [1] owing anodic dissolution in in acidic media [2-4]. Among numerous means of corrosion prevention, covering a steel surface with a corrosion inhibitor is considered as one of the most economical approaches [5]. The adsorption/retention of inhibitors on the steel surface depends on its chemical properties and a surface charge and it is affected by a temperature and the type of electrolyte used [6-8]. The evaluation of steel corrosion inhibition is often carried out in hydrochloric acid (HCl), which is one of the most aggressive acidic medium. Few materials can withstand exposure to such an environment. In general, the HCl treatment is used for removing undesirable flaking and rusting in several industrial processes. However, to prevent hydrochloric acid from a direct contact with the material, the industries must find techniques to isolate/protect the steel surface from the acid exposure. Ionic liquids are a group of compounds which has been recently used in various chemical technologies [9]. They have been used as solvents and catalysts in chemical engineering [10], in supercapacitors [11], and helped with the electrodeposition of metals [12]. Other applications include chemical separation processes, supported liquid membranes [13], or corrosion inhibitors [14-16]. When the corrosion inhibitors are added at a low concentration, they slow the rate of corrosion and subsequently inhibit the degradation of a metal exposed to various corrosive environments. At present, organic compounds are frequently used as corrosion inhibitors for mild steel in an acidic medium [17-21]. The fascinating properties of ionic liquids such as low toxicity, low vapor pressure, high polarity, high thermal and chemical stability, less hazardous influence on environment make them as a promising candidate for replacing the conventionally used highly volatile and toxic corrosion inhibitors [17]. Mild steel is most frequently used as a construction material in several industries due to its high mechanical strength and low cost [22-24]. However, this is highly reactive and undergo corrosive degradation during various industrial processes like acid cleaning, acid descaling, and acid pickling processes that require the use of additives to increase the lifespan of metal/alloy [25,26]. Recently, organic compounds, such as ionic liquids, containing heterocyclic rings and polar functional groups such as alkylamine [27,28], ammonium-based compounds [29,30], imidazolium derivates [31-33], 3

polymerizable ionic liquids-based nanoparticles [34,35] and nitrogen and phosphorous doped based ionic liquids [36] have been reported as efficient additives protecting metals and alloys from the unsolicited reactions. The objective of this paper is the evaluation of the effect of a new corrosion inhibitor, 1-(3-phenoxypropyl) pyridazin-1-ium bromide (PyB), on prevention a mild steel corrosion in a HCl (1M) solution. The effects of various concentrations of PyB on the inhibition efficiency have been evaluated. The morphologies of the steel surface were analyzed by SEM microscopy and XPS spectroscopy. The choice of pyridazinium derivative was based on its chemical composition. The presence of heteroatoms in the molecule such as oxygen (O), nitrogen (N), phosphorus (P), sulfur (S), and multiple bonds, enable an adsorption on the surface of metal. This compound has not been reported previously as a corrosion inhibitor. The synthesis procedure requires only one a single step reaction. Furthermore, these features are expected to favor the inhibitor adsorption on the steel surface [37,38] and this process is predicted to prevent corrosion

2.

Experimental details

2.1. Synthesis of Pyridazinium derivate (PyB) Pyridazine and (3-Bromopropoxy) Benzene from Aldrich (1:1, eq) dissolved in toluene were placed in a tightly closed container and left under ultrasonic conditions for 5h. Precipitation of a solid marked the completion of the reaction. The pyridazinium salt (1-(3-phenoxypropyl) pyridazin-1-ium bromide, PyB (Fig. 1) was isolated by filtration and washed three times with ethyl acetate to remove any unreacted compounds and solvent. Obtained PyB was dried under vacuum. PyB was analyzed by NMR (Electronic Supplementary Information as Fig ES1-2. FTIR and LC-MS data are reported in SI).

Figure 1. Molecular structure of PyB (1-(3-phenoxypropyl) pyridazin-1-ium bromide.

4

2.2. Characterization and data analysis 2.2.1. Sample preparation. The carbon steel sheets (mild steel) with the dimension 2×1×0.25 cm was used. Their chemical composition (%) was as follows: C: 0.21; Si: 0.38; Mn: 0.05; S: 0.05; P: 0.09; Al: 0.01 and balanced with Fe. Samples were polished using emery paper (400, 600, 800, 1200, 1500), degreased with acetone and rinsed with bi-distilled water. HCl (1M) solution was prepared by dilution of HCl (ACS-ISO, 37%) in double distilled water. PyB concentrations tested were: 10-3-10-6 M. Steels were treated before treatment with the optimum concentration of PyB (10-3 M) with HCl (1M) solution for 6 h solution in the absence or presence of the optimum concentration of the PyB (10-3 M)

2.2.2. Gravimetric evaluation of the corrosion extent The mild steel was weighted before and after immersion in HCl (1M) solution. The latter was without and with various PyB concentrations. The experiments were performed in a cell equipped with a thermostatic cooling condenser at 25°C for 6 h. The inhibition efficiency (IE%) was determined using the following equation:

IE% = (Wcorr -Wcorr/inh)/ Wcorr

(eq. 1)

W= (mi-mf)/St

(eq. 2)

Where mi is the initial mass; mf is the final mg; S represents the area of the sample in cm2 ; t is the immersion time in s, Wcorr and Wcorr/inh are the corrosion rate in the absence and presence of the PyB inhibitor, respectively, in mg.cm-2·s-1.

2.2.3. Impedance spectroscopy Temperature, concentration and immersion time effects were evaluated by electrochemical impedance spectroscopy (EIS), using a PGZ 301 Voltalab potentiostat Radiometer). C-steel pieces with a surface of 1 cm² were used as working electrodes (WE) in the PyB solution; a large area platinum mesh was used as a counter electrode (CE), and saturated calomel electrode - as a reference electrode (RE). The instrument 5

was controlled with a VoltaMaster 4 software. EIS measurements were carried out at 10 mV in a frequency range of 100 kHz-10 mHz. The Nyquist plots were constructed from the measurements at various temperatures (25-55°C), either in the absence or the presence of PyB inhibitor. The 1M HCl solution was prepared by dilution of HCl (ACSISO, 37%) in double distilled water. PyB concentrations tested were in the range 10 -310-6 M. The electrochemical parameters extracted from this experimental approach are the charge transfer resistance Rct and the double layer capacitance C dl. To analyse all the EIS data, the equivalent circuit model was used to fit the spectra of the various concentrations of PyB and then ZView2 software was used to calculate Rct and Cdl in the equivalent circuit and compared with the obtained by Voltamaster 4 [39,40].

2.2.4. Scanning electron microscopy (SEM) The morphology of the mild steel surface before and after 6 h immersion in the 1.0 M HCl solution in the absence or presence of the optimum concentration of the PyB inhibitor (10-3 M); determined based on EIS experiments) at 25 ºC was performed using SEM. The images were obtained on JEOL, JSM 6400.

2.2.5. XPS analysis XPS studies were carried out on a Physical Electronics PHI VersaProbe II spectrometer using monochromatic Al-K radiation (49.1 W, 15 kV and 1486.6 eV) for analyzing the core-level signals of the elements of interest with a hemispherical multichannel analyzer. The sample spectra were recorded with a constant pass energy value at 29.35 eV, using a 200 μm diameter circular analysis area. The X-ray photoelectron spectra obtained were analyzed using PHI SmartSoft software and processed using MultiPak 9.3 package. The binding energy values were referenced to adventitious carbon C 1s signal (284.8 eV). Shirley-type background and Gauss-Lorentz curves were used to determine the binding energies.

3. Results and discussion The evolution of the corrosion rate of mild steel at various concentrations of PyB in HCl (1M) was determined after 6 h of the steel immersion process at 25°C. Table 1 shows the corrosion rate and the calculated inhibition efficiency (% IEG). 6

Table 1. Corrosion rate (Wcorr) and inhibition efficiency (IE) of mild steel in HCl (1M) at various PyB concentrations. Concentration / M

Wcorr. / mg.cm-2.h-1

IEG/ %

1.0

0.6521

-

10-3

0.0312

95.2

10-4 10-5 10-6

0.1395 0.2754 0.4748

78.6 57.8 27.2

HCl

PyB

The results obtained from weight loss measurements show that the corrosion rate decreases with an increase in the PyB concentration and the inhibition efficiency is reaching a maximum of 95.2 % when [PyB] = 10-3 M. Thus, this concentration is considered as an optimal one to prevent the steel corrosion process [41].

300 -3

10 M -4 10 M -5 10 M -6 10 M 1M HCl fiting curve

250

2

-Zim (ohm.cm )

200

150

100

50

0 0

50

100

150

200

250

300

350

400

450

2

Zre (ohm.cm )

Figure 2. Nyquist plots of mild steel in HCl (1 M) constructed from the data collected at 25ºC at various PyB concentrations: (symbol) experimental data; (line) fitted data. The Nyquist plots collected for mild steel immersed for 6h in HCl (1M) at various PyB concentrations at 25°C are showed in Fig.2. The semi-circles are clearly seen on the plots and theirs sizes increase with an increase in the inhibitor concentration. This, along with the inhibition rates results, suggests that the corrosion of steel is controlled 7

mainly with a charge transfer process [42]. The appearance of the depressed nature semi-circle is characteristic of solid electrodes and it is attributed to the heterogeneity of the steel surface [43,44]. The diameter of the capacitive loop increased gradually with the increasing concentrations of PyB indicating that the charge transfer resistance increased, and the adsorbed inhibitor formed a more compact monolayer on the metal surface with an increasing amount of inhibitor. Table 2 summarizes the impedance parameters such as the charge transfer resistance Rct, the double layer capacitance Cdl, and the inhibition efficiency IE%. The inhibition efficiency was calculated from a charge transfer resistance by equation (3) [45], Where Rct/inh and Rct are the charge transfer resistance with and without inhibitor, respectively. IEG ( %) = [(Rct/inh – Rct) / Rct/inh] × 100 (eq. 3) Table 2. Impedance parameters for mild steel at various PyB concentrations at 25 ºC. Rct (Ω cm2) 34 379

Cdl (μF cm-2) 114

IEIMP (%) -

33

91.03

10-4

148

53

77.03

10-5 10-6

136

56

75.00

86

62

60.47

Inhibitor Concentration (M) 0 10-3 PyB

The EIS results show that the charge transfer resistance R ct increases with an increasing PyB concentration. On the contrary, the double layer capacitance decreases with more PyB present in the solution. The decrease in C dl is likely caused by the adsorption of inhibitor on the metal surface causing a change in the double layer structure [46], which led to an increase in the inhibition efficiency. This efficiency reached the maximum value of 91.03 % at the concentration of 10 -3 M (at 25°C). These results are consistent with the results of the gravimetric measurements discussed above (Table 1). The thickness of the protective inhibitor layer (δ org), is related to Cdl through the following equation [47]: Cdl = ε0εr /δorg

(eq. 4)

Where, ε0 is the vacuum dielectric constant and εr is the relative dielectric constant. The observed decrease in Cdl might be caused by a decrease in a local dielectric constant or

2

by an increase in the thickness of the electrical double layer. These changes are expected to be the results of the inhibitor adsorption on the steel surface. The Nyquist plots were modeled by an equivalent electrical circuit (Fig. 3). Rs

CPE Rct

Figure 3. Equivalent electrical circuit of the steel/PyB/HCl interface. The circuit used for PyB has The Constant Phase Element Value (CPE) which is inError parallel Element Freedom

Free(+) with the charge transfer Rs resistance (R ct) and together they are0in series with theN/A solution CPE-T CPE-P theRct experimental

Fixed(X) Fixed(X) data are listed Fixed(X)

0 1 Table 0

N/A N/A double-layer N/A

resistance (Rs). The corresponding EIS parameters such as R s, Rct, Cdl, n, and IEIMP % obtained by fitting

in

3. The

Error % N/A N/A N/A N/A

capacitance (Cdl) is related to the transfer charge resistance R ct and the CPE constant (Q)

Chi-Squared: by the following equation [48]:

0.0076669 Weighted Sum of Squares: 0.72069 Cdl = (Q.Rct1-n) 1/n

(eq. 5)

Data File: C:\Users\Hamid\Desktop\zerrouk\e Circuitfactor Model Where Q is the proportionality and File: n are the CPE exponent which represent the Mode: Run Fitting / Freq. Range (0.01 - 1 surface inhomogeneity. Table 3 shows that the charge transfer resistance significantly Maximum Iterations: 100 increases as a function of the inhibitor concentration Optimization Iterations:while the 0 double layer capacitance Fitting: Complex decreases, as discussedType above.ofThe low values of Cdl indicate the decrease in the Type of Weighting: Calc-Modulus exposed area of the electrode due to the formed surface coating by the adsorbed inhibitor. According to Macdonald et al., the exponent (n) is a measure of the surface heterogeneity, related with phase shift, briefly: *if n=0 the CPE constant represents R ct and if n=1 the CPE constant represents Cdl (if the values of n are between 0 and 1 this is mean ideal CPE constant which is our case in this experiment) [49].; Rs become more important in presence of inhibitor, from 1.29Ω cm2 in absence of inhibitor to 2.17 Ω cm2 at 10-3M of PyB, that's mean that our solution becomes more active by the charge transfer happens between the surface and the solution. The decrease of n can be also explained by the existence of thin layer of adsorbed PyB covering the steel surface. To study the effect of the immersion time on the corrosion of mild steel in the HCl (1M) solution, the electrochemical impedance spectroscopy measurements were collected at various immersion times (1, 2, 4, 6, 12 and 24 h) at the PyB concentration of 10-3 M (Table 4), which was indicated above as leading to the most efficient inhibition 3

process. The parameters obtained from the impedance curve fitting, including the charge transfer resistance Rt and the double layer capacitance C dl, are collected in Table 4. Increasing the immersion time from 1 to 24 h shifts the Rct toward the smaller values and increases the corrosion of steel by increasing the corresponding C dl values. This is shown in the decrease in the inhibition efficiency IE IMP (%) with time. It is important to mention that the inhibition efficiency remains significant even after a long time. The effect of temperature on the mild steel corrosion in the HCl (1 M) solution in the temperature range 35-55 ºC at various PyB concentrations was also studied by EIS electrochemical impedance spectroscopy after 1 h immersion in the aggressively acidic electrolyte (Figure 4).

Figure 4. Impedance diagrams of mild steel in HCl (1M) at various temperatures A) 35° and B) 45 °C with PyB = 10-3M.

The parameters calculated from fitting of the impedance spectra such as the charge transfer resistance, the double layer capacitance and inhibition efficiency are collected in Table 5. As shown, the charge transfer resistance at a fixed temperature decreases increases with PyB concentration. The charge transfer resistance also decreases with an increase in the temperature, both in the inhibited and uninhibited solutions. Consequently, the inhibition efficiency of the inhibitor decreases slightly with the increasing temperature (Figure 4).

2

Table 3. Electrical parameters of the equivalent circuit C/M HCl (1M) PyB

Rs /Ω cm2

Rct /Ω m2

10-4 Q/Ω-1cm-2s-n

n

Cdl / μF cm-2I IE/ %

0

1.29±0.01

34.22±0.15

3.49±0.07

0.0±0.003

115.37

-

10-3

2.17±0.07

367.7±0.66

0.83±0.04

0.75±0.006

25.93

90.69

-4

1.70±0.03 1.59±0.03 1.72±0.04

140.9±0.80 136.5±0.99 87.24±0.60

1.55±0.03 1.53± 0.04 2.31±0.08

0.73±0.007 0.75±0.003 0.70±0.006

37.67 42.13 43.34

75.71 74.93 60.77

10 10-5 10-6

Table 4. Variation of Rtc and Cdl with the immersion time of mild steel in HCl (1M) with PyB (10-3 M ) at 25°C. Immersion / h 1 2 4 6 12

Rct /Ω cm2 (PyB) 217 183 171 139 108

Rct /Ω.cm2 (Blank) 27 22 19 19 10

Cdl / μF cm-2 34 36 46 56 58

11

Table 5. Influence of temperature on the inhibition efficiency in HCl (1M) at various concentrations of PyB.

T/°C

Concentration/M

Rtc ct/Ω cm2

Cdl / F cm-2

EIMP/%

35

0 10-3

27 163

73

-

30

83.44

10-4 10-5

73

53

63.01

70

45

61.43

10-6 0 10-3

40 16

39 40

32 -

89

53

82.02

10-4 10-5

30

65

46.67

16

67

-

10−6

13 8.7 28

72 91

-

56

68,93

10−4 10−5

17

72

48,82

15

81

42,00

10−6

4

98

-

45

55

0 10−3

The results collected in Table 5 show that the investigated compound inhibits the corrosion of mild steel when used at various concentrations and temperatures and the inhibition is more efficient with an increase in the PyB concentration. This behaviour can be attributed to the increased adsorption and thus to a steel surface coverage by the inhibitor as a function of an increased PyB concentration, as showed in the value of inhibition efficiency, IE (90.69%) and the parameters of the double layer formed by PyB such as capacitance, Cdl (25.93 μFcm-2) and resistance, R (367.7 Rct/Ω m2), which justified a great resistance to the charge transfer [50]. The nature of the adsorption process depends on the physico-chemical properties of inhibitors/adsorbate and an adsorbent/steel surface feature. The adsorption of these kind of organic compounds on a metal surface is considered as a chemical process, which takes place through a charge transfer of the delocalized π-electrons of the adsorbate to the empty d-orbital of the iron atoms. The new inhibitor tested, PyB, contains two nitrogen atoms on the benzoic ring linked together by a double bond and its electron-rich nature is expected to promote these kind of interactions [51]. The 12

presence of two nitrogen atoms on a benzoic ring linked together by a double bond (- stacking) might lead to the efficiency of PyB inhibitor. The morphologies of the steel surface after the treatment with HCl (1M) in the presence of PyB (10 -3 M) were analysed by SEM microscopy (Fig. 5). Fig. 5A shows the finely polished characteristic surface of mild steel where some scratches, due to polishing, are visible. The steel surface is strongly damaged in the HCl solution (absence of the inhibitor, Fig. 5B). Fig. 5C shows that the contact of steel with the PyB inhibitor leads to the formation of an adsorbed film, which is likely responsible for the highly effective corrosion inhibition by this adsorbed compound on the steel surface.

Figure 5. SEM image of mild steel surface A) Before; B) After 6 h of immersion in the HCl (1M) solution in the absence PyB and C) After 6 h of immersion in the HCl (1M) solution with PyB (10-3M).

The surface chemistry of the mild steel before (Blank), after 6 h of immersion in the HCl (1M) solution in the absence PyB (HCl), and after 6 h of immersion in HCl (1M) solution with PyB (10-3M) was analysed by XPS. Table 6 shows the atomic concentration of elements on the surface. The observed high atomic concentration of C in the blank sample is characteristic of all metallic surfaces exposed to air [52]. The treatment with HCl results in a clear decrease in the contents of Fe and O, and in an increase of the contents of C, Si and N. The treatment with PyB caused, as expected, a clear increase in the content of C and a decrease in the contents of O and Si. This is the results of the inhibitor adsorption on the

2

steel surface. More information can be derived from the analysis of the intensities of the evolution of the C 1s, O 1s and Fe 2p core level spectra of these three samples (Figure 6).

Table 6. Atomic concentration [in at %] of elements on the surface of mild steel before (Blank), after 6 h immersion in the HCl (1M) solution in the absence PyB (HCl) and after 6 h immersion in the HCl (1M) solution with PyB (10-3M) (Py). Sample Blank HCl Py

%C 58.06 67.34 74.73

%O 29.82 23.69 18.62

%Fe 7.18 2.12 1.70

%N 0.68 1.70 1.23

%Si 4.26 5.15 3.72

%Cl n.d n.d n.d.

The C 1s spectra (Figure 6A) of mild steel (blank) and mild steel treated with HCl show similar intensities, and, when treated with PyB increases the intensity of C 1 s at a low binding energy due to the adsorption of the inhibitor which contains C-C and –C=C- bonds. Figure 6B shows the deconvoluted C 1s spectra for steel treated with PyB. Three mains contributions at 284.8, 286.6 and 288.2 eV are seen, and they are assigned to C-C/-C=C-/CH, C-O/C-N and C=O functional groups present on the steel surface, respectively. The O 1s spectra (Figure 6C) also indicates interesting changes. The contribution at 529.8 eV is due to the lattice oxygen from iron oxide [53], while the second one 532.5 eV is assigned to oxygen from silica (contamination) and iron hydroxide. The sample treated with the inhibitor shows the smaller content of Si and the relative intensity of its contribution at 532.5

eV

is

the

weak

one

(Figure ESI4), the presence of Si in the sample is justified by the previous coverage with a plastic. Concerning the relative intensities of the contributions at low binding energy (about 529.8 eV), there is a clear correlation between the content of iron and the intensity of these contributions, showing the sample with the higher Fe content as having a more intense contribution at low binding energy. The observed intensities of the Fe 2p core level spectra (Figure 6D) also follow the same trend as those found for the O 1s contribution at low binding energy. Another interesting finding is a clear presence of a contribution at about 707 eV in the Fe 2p3/2 signal due to Fe0 in the case of sample treated with HCl and with the inhibitor. Analysing the intensities, is observed that when treated with PyB decrease the presence on the surface of Fe-O. The nitrogen signal was very week and therefore the trend in its content on the surface are not discussed. Besides, an increase in the carbon can affect the relative nitrogen content detected. 2

In summary, XPS results confirm that the treatment with the inhibitor leas the deposition of a PyB film of the surface of mild steel. This is demonstrated by the increase in the C content and a decrease in the O content, and in the presence more metallic iron.

Figure 6. XPS core level spectra of A) C 1s for untreated steel (black), with HCl (1M) (red) and treated with inhibitor PyB (blue); B) Deconvoluted C 1s signal of PyB on the steel surface C) O 1s for untreated steel (black), with HCl (1M) (red) and treated with inhibitor PyB (blue) and D) Fe 2p for untreated steel (black), with HCl (1M) (red) and treated with inhibitor PyB (blue).

4. Conclusions The collected results indicate that PyB is a good inhibitor of mild steel corrosion, when exposed to acidic conditions (0.1 M HCl). The inhibition efficiency increases with an increase in its concentration and reaches 91.03% for PyB at 10-3M at 25 °C. The EIS results showed that the PyB inhibitor significantly increased the charge transfer resistance and decreased the double layer capacitance. The adsorption of PyB led to the formation of a protective film on the surface of the steel. The evaluation of the effects of the immersion time showed that the inhibition efficiency of PyB increased with the exposure time. XPS and 3

SEM measurements supported that PyB covered the steel surface when immersed in HCl (1M) medium with PyB.

Acknowledgments The authors thank to the project CTQ2015-68951-C3-3-R (MINECO, Spain). This work was supported by FCT-Fundação para a Ciência e a Tecnologia (projectPEst-OE/QUI/UI0674/2019, CQM, Portuguese Government funds), and through Madeira 14-20 Program, project PROEQUIPRAM - Reforço do Investimento em Equipamentos e Infraestruturas Científicas na RAM (M1420-01-0145-FEDER-000008) and by ARDITI-Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação, through the project M1420-01-0145-FEDER-000005 - Centro de Química da Madeira - CQM+ (Madeira 14-20).”

References [1] S. Ghareba, S. Omanovic, Corros. Sci., 52 (2010) 2104. [2] Y. Jianguo, W. Lin, V. Otteno-Alegoi and D.P. Schweinsberg, Corros. Sci. 37 (1995) 975. [3] F. El-Hajjaji, M. Messali, A. Aljuhani, M.R. Aouad, B. Hammouti, M.E. Belghiti, D.S. Chauhan, M.A. Quraishi, J. Mol. Liq, 249 (2018) 997. [4] G. Khan W.J. Basirun, S. N. Kazi, P. Ahmed, L. Magaji, S.M. Ahmed, G.M. Khan, M. A. Rehman, A. B. Badry, J. Coll. Interf. Sci. 502 (2017) 134. [5] L. Guo, S. Kaya, I.B. Obot, X. Zheng, Y. Qiang, J. Coll. Interf. Sci. 506 (2017) 478. [6] J.M. Sykes, Br. Corros. J. 25 (1990) 175. [7] M. Elachouri, M.S. Hajji, S. Kertit, E.M. Essasi, M. Salem, R. Coudert, Corros. Sci. 37 (1995) 381. [8] B. Mernari, H. El Attari, M. Traisnel, F. Bentiss, M. Lagrene´e, Corros. Sci. 40 (1998) 391. [9] P. Wasserscheid, T. Welton, Ionic Liquids in Synthesis, John Wiley & Sons, 2008. [10] J.F. Liu, G.B. Jiang, Y.G. Chi, Y.Q. Cai, Q.X. Zhou, J.T. Hu, Anal. Chem. 75 (2003) 5870. [11] M. Ue, M. Takeda, A. Toriumi, A. Kominato, R. Hagiwara, Y. Ito, J. Electrochem. Soc. 150 (2003) A499. [12] M.A. Ibrahim, M. Messali, Prod. Finish. 2 (2011) 14, [13] R.D. Rogers, K.R. Seddon, Ionic Liquids: Industrial Applications for Green Chemistry, ACS Pubs, 818, 2002. [14] E. Ech-chihbi, M.E. Belghiti, R. Salim, H. Oudda, M. Taleb, N. Benchat, B. Hammouti, F. El-Hajjaji , Surfaces and Interfaces . 9 (2017) 206. [15] A. Bousskri, A. Anejjar, M. Messali, R. Salghi, O. Benali, Y. Karzazi, S. Jodeh, M. Zougagh, E.E. Ebenso, B. Hammouti, J. Mol. Liq. 211 (2015) 1000. 4

[16] A. Zarrouk, M. Messali, H. Zarrok, R. Salghi, A. Ali, B. Hammouti, S. Al-Deyab, F. Bentiss, Int. J. Electrochem. Sci. 7 (2012) 6998. [17] A. Verma, E.E. Ebenso, MA. Quraishi, J Mol Liq (2017) 233. [18] Y. Ma, F. Han, Z. Li, C. Xia. ACS Sustainable Chem. Eng. 4 (2016) 5046. [19] C. Verma, I.B. Obot, I. Bahadur, E. M. Sherif, E. E. Ebenso. Appl. Surf. Science 457 (2018) 134-149 [20] K. Zhang, W. Yang, Y. Chen, B. Xu, X. Yin, Y. Liu, H. Zuo. J. Mater. Sci. 53 (2018) 14666-14680 [21] L. Feng, S. Zhang, Y. Qiang, S. Xu, B. Tan, S. Chen. Mater. Chem. Phys. 215 (2018) 229-241. [22] H. S. Link, R. J. Schmitt. Ind. Eng. Chem. 53 (1961) 590-595 [23] N. R. Badoo. J. Constructional Steel Res. 64 (2008) 1199-1206. [24] B.H. Smith, S. Szyniszewski, J. F. Hajjar, B.W. Schafer, S.R. Arwade. J. Constructional Steel Res. 71 (2012) 1-10. [25] A. Bakkar, S. Ataya. Corr. Sci. 85 (2014) 343-351 [26] M.K. Pavithra, T.V Venkatesha, M.K.P. Kumar, H.C. Tondan. Corr. Sci. 60 (2012) 104-111. [27] F. L. Bernard, F. D. Vecchia, M. F. Rojas, R. Ligabue, M. O. Vieira, E. M. Costa, V. V. Chaban, S. Einloft. J. Chem. Eng. Data 2016, 61, 1803-1810 [28] J. Yang, X. Yu, J. Yan, S. Tu. Ind. Eng. Chem. Res. 53 (2014) 2790-2799 [29] P. Arellanes-Lozada, O. Olivares-Xometl, N.V. Likhanova, I.V. Lijanova, J.R. VargasGarcía, R. E. Hernández-Ramírez. J. Molec. Liq. 265 (2018) 151-163 [30] J. Haque, V. Srivastava, C. Verma, H. Lgaz, R. Salghi, M. A. Quraishi. New J. Chem. 41 (2017) 13647-13662 [31] M. Mashuga, L. Olasunkanmi, A. Adekunle, S. Yesudass, M. Kabanda, E. Ebenso. Materials 8 (2015) 3607-3632 [32] D. Yang, M. Zhang, J. Zheng, H. Castaneda. RSC Advances 5 (2015) 95160-95170 [33] Y. Qiang, S. Zhang, L. Guo, X. Zheng, B. Xiang, S. Chen. Corr. Sci. 119 (2017) 68-78 [34] M. Taghavikish, S. Subianto, N. K. Dutta, L. de Campo, J. P. Mata, C. Rehm, N. R. Choudhury. ACS Omega 1 (2016) 29-40. [35] R. Marcilla, M. Sanchez-Paniagua, B. Lopez-Ruiz, E. Lopez-Cabarcos, E. Ochoteco, H. Grande, D. Mecerreyes. J. Polym. Sci., Part A: Polym. Chem. 44 (2006) 3958-3965 [36] Q. Yu, C. Zhang, R. Dong, Y. Shi, Y. Wang, Y. Bai, J. Zhang, M. Cai, F. Zhou. Tribology Intern. 132 (2019) 118-129. [37] A.F. Al-Ghamdi, M. Messali, S.A. Ahmed, J. Mater. Environ. Sci. 3 (2011) 215. [38] A. Ghazoui, N. Benchat , F. El-Hajjaji , M. Taleb , Z. Rais , R. Saddik , A. Elaatiaoui , B. Hammouti. Journal of Alloys and Compounds. 693 (2016) 510. [39] Zview version 2.9b. Copyright 1990–2005, Scribner Associates, Inc. D. Johnson. [40] J. F. Basbus, M. D. Arce, F. Prado, L. Suescun, A. Caneiro, L. V. Mognia. Journal of The Electrochemical Society, 6 (2016) 516. [41] F. El-Hajjaji, R. Belkhmima, B. Zerga, M. Sfaira, M. Taleb, M. EbnTouhami, B. Hammouti, S. Al-Deyab, E. Ebenso, Int. J. Electrochem. Sci. 9 (2014) 4721. [42] A. Bouoidina, F. El-Hajjaji, M. Drissi, M. Taleb, B. Hammouti, I.L. Chung, S. Jodeh, H. Lgaz. Metall and Mat Trans A (2018). https://doi.org/10.1007/s11661-018-4828-4. 5

[43] T. E.W. Flick. Corrosion Inhibitors, Park Ridge, New Jersey. (1987) 68. [44] B. Gomez, N.V. Likhanova, M.A. Dominguez Aguilar, O. Olivares, J.M. Hallen, J.M. Martinez-Magadan, J. Phys. Chem. A 109 (2005) 8950. [45] S.L. Granese, Corrosion 44 (1998) 322. 14. F. Bentiss, M. Traisnel and M. Lagrenee, J. Appl. Electrochem. 31 (2000) 41. [46] F. Bentiss, M. Lagrenee and M. Traisnel, Corros. Sci. 42 (2000) 127. [47] E.M. Sherif, R.M. Erasmus, J.D. Comins, J Colloid Interface Sci. 309 (2007) 470. [48] R. Solmaz. Corrosion Science 79 (2014) 169–176 [49] F. El Hajjaji, F. Abrigach, O. Hamed, A. R. Hasan, M. Taleb, S. Jodeh, E. RodríguezCastellón, M.V. M. Yuso, M. Algarra, Coatings. 8 (2018) 330. [50] Z. Ahmad. Principles of Corrosion Engineering and Corrosion Control. Elsevier, (2006). [51] V.S. Sastri, Corrosion Inhibitor, Wiley, New York, NY, 373 (1998) 39. [52] C. Sciancaleporea, L. Gemini, L. Romoli, F. Bondioli. Surf. Coating Techn. 352 (2018) 370-377. [53] J.F. Moulder, W.F. Stickle, P.E. Sobol, K.D. Bomben, Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer Corp, Eden Prairie, MN. 1992.

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*Graphical Abstract

Graphical Abstract

PyB (10-3M)

25 °C