- Email: [email protected]
Black oxide conversion coating on metals: A review of coating techniques and adaptation for SAE 420A surgical grade stainless steel
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 4 (2017) 9534–9541
www.materialstoday.com/proceedings
ICEMS 2016
Black oxide conversion coating on metals: A review of coating techniques and adaptation for SAE 420A surgical grade stainless steel Reghuraj.A.Ra*, Saju.K.Kb a
b
Research scholar, Mechanical Engineering Division, School of Engineering, Cochin University of Science And Technology, Kalamassery, Cochin, Kerala, India. Professor, Mechanical Engineering Division, School of Engineering, Cochin University of Science And Technology, Kalamassery, Cochin, Kerala, India.
Abstract Surgical grade martensitic stainless steel SAE 420A is one of the main materials being used in the production of surgical instruments. Majority of the surgical instruments have high reflectance. Since these instruments are used for many hours in surgery rooms which involves conditions of bright lighting the user experiences heavy eye strain and lack of precision due to the high reflective nature of the material. Therefore surgical instruments with lower reflectance will be able to reduce the above undesired effects. An effective black oxide coating is seen to improve the efficacy of the surgeon and surgical instruments by providing a glare free environment at the point of surgery. This paper reviews procedures for providing a non reflective corrosion resistant and non toxic black oxide coating on metals and explores possibility to adapt it to 420A stainless steel. © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Recent Trends in Engineering and Material Sciences (ICEMS-2016). Keywords: Conversion coatings; Blackening; 420A Stainless steel; Black oxide; Reflectance.
*
Corresponding author. Tel: +91-9947379668 E-mail: [email protected]
2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Recent Trends in Engineering and Material Sciences (ICEMS2016).
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
9535
1. Introduction Stainless steels are widely used for the manufacture of surgical instruments [1]. Reflection from the surgical instruments made of surgical grade martensitic stainless steel under bright light is creating undesired difficulties to the surgeons like loss of precision, device control difficulty etc especially in laparoscopic surgeries [2,12]. The precision and device control in laparoscopic and key-hole surgeries are vital. Matte black oxide coating of surgical steels has been suggested to reduce the reflectivity of surgical grade stainless steel. Black oxide is a conversion coating formed on the metal surface as a result of chemical reaction of the metal atoms with an oxidizing agent such as atmospheric air, alkaline aqueous salt solution and molten salts. The conversion coating is a film of chemical compound formed in the reaction of the substrate substance with another substance [3]. This reaction distinguishes conversion coating from a conventional coating. Stainless steels of grade 303, 304, 410, 420A, 420B, 420C, 420 Mod. Grade 303, 304 under class-3 Austenitic stainless steel) and 410, 420A, 420B, 420C, 420 Mod comes under class 4 (Martensitic stainless steel) classifications are used for manufacturing surgical instruments [4,7]. Currently surgical equipments are manufactured from superior grade 410 stainless steels. The surgical grade martensitic stainless steel is strong, hard, and wear resistant but it has less corrosion resistance [5]. For ages it’s been a custom to employ the austenitic stainless steel, especially grade 316L, as medical grade stainless steel in orthopedic field [6]. Nomenclature SAE AISI CVD PVD
Society of Automotive Engineers American Iron and Steel Institute Chemical Vapour Deposition Physical Vapour Deposition
2. Physiochemical Surface Modification Extensive studies have been carried out on different coating methods. Jingxin Yang,Fuzhai Cui, In Seop Lee broadly classified all the various surface modification techniques which are used to improve the surface properties of Magnesium alloys employed in biomedical applications [8]. Materials and their tissue response can be changed by changing physiochemical characteristics such as energy, charge and composition of the surface. The various techniques commonly used for applying coating on metals are electroplating, electroless plating, hot dipping, Chemical Vapour Deposition (CVD), Physical Vapour Deposition (PVD), thermal spraying and conversion coatings [8]. Coating is a layer of a substance applied to the substrate surface. Coating material is normally different from the substrate material and it make possible achieving special or better surface properties of the part without changing its bulk properties like appearances, adhesion, wetability, corrosion, oxidation resistance, wear resistance, scratch resistance and hardness. Many attempts have been made to improve the anti-reflective coating on grade 300 series stainless steel which is used extensively for orthopaedic applications. This paper reviews the experiments that were conducted to obtain a coating on different metals. 3. Principle of hot alkaline/chemical conversion coating The formation and deposition process of conversion type coatings can be classified into two, chemical and electrochemical. In chemical processes oxide coating deposits are formed on the surface of substrate by simple immersion of parts in oxidizing solution, but in electrochemical, electric current plays a vital role in process control and deposition [3] [16,29]. In chemical conversion coating processes, non metallic coatings are produced by the transformation of outer atomic layers of a metal surface in to new non-metallic forms with different sets of properties from the original surface [9]. The substrate reacts with another substances which are in the form of solids, liquids or gases so that substrate surface is chemically converted into different compounds having different properties at elevated temperatures [10,11]. This reaction distinguishes conversion coating from a conventional
9536
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
coating, which is usually applied on the surface without changing its chemical state. Ferrous metals and its alloys are commercially treated to produce oxide coatings by chemical conversion of their surfaces. The most commonly used method for blackening steels and stainless steels is the immersion of metal in a hot highly alkaline solution containing an oxidizing agent and then treating them in a atmosphere of steam at 3000C – 6000C, to convert the surface to black oxide (Fe3O4) [9]. 4. Review of the coating methods Frank Hollstein, Petr Louda established that the reflection and scattering of bright light from the surface of surgical instruments made of stainless steels disturbs the visual operating field of surgeon especially during minimally invasive surgery. To reduce this problem a two layer black film of TiAlN and TiCN, developed by Physical Vapour Deposition (PVD) and unbalanced magnetron sputtering, was coated. However these two single layers do not seem to be sufficiently dense to protect the substrate against corrosion. Also the coating on the substrate gets affected by multiple sterilization of the instruments. Therefore a Nb intermediate layer as a diffusion and oxidation barrier was deposited. The long term oxidation stability of multilayer Nb/TiAlN and Nb/TiCN on SS substrate could be significantly affected by the PVD coating methods and the different conditions in reactive modes [12]. Monica Lira- Cantu, Angel Morales Sabio, Alex Brustenga, Pedro Gomez-Romero (2005) discussed about black nickel solar absorber coating on stainless steel AISI 316L for light absorbing, without reflection. The antireflection coating was used for conversion of incident solar radiation into useful heat by minimizing thermal back-radiation. The antireflection coating was developed by Electro chemical deposition and final antireflective coating on stainless steel AISI 316L was made based on TEOS (Tetra-ethylorthosilica). The black nickel solar absorber coating was done on the bright nickel coated stainless steel substrate. Nickel chloride 70 g/L, sodium chloride 30 g/L, water volume 1L were used as the chemical solution and the coating process was carried out by electrochemical deposition method. Sol-gel silica based anti reflective coating from TEOS (Tetra-ethylorthosilica) was also applied to solar surface by deep coating method with the controlled immersion velocity of 30cm/min [13]. Ales Nagode, Grega Klancnik, Heidy Schwarczova, Borut Kosec, Mirko Gojic discussed about the formation of black oxide coating on the surface of grey cast iron hot plates made for an electric stove. For this case black oxide coating is used to produce a protective dark oxide layer consisting predominantly of magnetite (Fe3O4) on the surface of hot plate. The dark oxide layer is stable at high temperatures. The most popular method of black oxide coating on cast iron is immersing the workpiece in a boiling aqueous alkaline solution of oxidizing salts [14]. The oxidation procedure is followed by a coloring procedure using a heated (about 100-1500C) oxidizing solution containing sodium hydroxide, sodium nitrite, sodium nitrate or mixtures which reacts with cast iron substrates to form magnetite (Fe3O4) [3]. Similar procedures can be adopted for 420A stainless steel. Jan-Kyo Kim, Ricky S. C. Woo, Pamela Y.P Hung, Mohamed Lebbai, in their work also mentioned the formation of black oxide coating on copper alloy. The black copper oxide coating is produced in a chemical conversion process where copper substrate is treated with mixture of high concentrated sodium chlorite and sodium hydroxide, in the ratio of 350g/L and 120 g/L at 850C for 4 minutes [15,18]. In this, the black oxide coating on copper alloy helps to improve the interfacial bond strength by improving adhesion of various polymers with copper. The moisture resistance of the substrate with black oxide coating was much higher than the bare copper substrate. A K Sharma, R Uma Rani, S M Mayanna did thermal studies on black oxide coated magnesium alloys developed using, electro deposition. The black oxide coating on magnesium alloys in this case is developed by black anodizing method. The solution is formulated using potassium dichromate, ammonium sulfate at a pH value of 5.8 and temperature ranging 230C - 270C. The heat treatment process is carried out at a temperature of 700C for 2 hours [16]. Mohamed LEBBAI, W.K SZETO and Jang-Kyo KIM developed the black oxide coating by immersing copper in to an oxidizing agent of alkaline – buffered solution at high temperature [17].
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
9537
R. Uma Rani, A.K Sharma, C. Minu G.Poornima, S. Tejaswi explained the blackening process of electroless nickel coating to produce ultra black coating on titanium alloys with higher optical properties. The formation of black colour nickel-phosphorous coating is due to the unique surface morphology of nickel oxides (NiO,NiO2) and some nickel phosphates, which gives higher solar properties especially absorptance [19]. T.D Burleigh, T.C Doston, K.T Doston, S.J Gabay, T.B Sloan and S.G Ferrel described the oxide formation on steel either in KOH or NaOH solutions with concentration anywhere from 10% to saturated. The optimum electrolytes for anodizing process for the formation of magnetite (Fe3O4) were reported as either 50% KOH or 25% NaOH. The common factor for this process is the requirement of high temperatures (2000C – 5000C) [20]. M.G.S Ferreira, N.E Hakiki, G.Goodlet, S. Faty, A.M.P Simoes, M. Da Cunha Belo- discussed the formation of oxide films formed on AISI 304 Stainless steel, which used borate buffer solution (pH 8.4) at 0.8V versus Saturated Calomel Electrode (SCE). The thermally grown oxide films were formed in air at controlled and selected temperatures between 500 and 4500C inside a furnace with a duration of 2 hours at atmospheric pressure [21]. M. Da Cunha Belo, M. Walls, N.E Hakiki, J. Corset, E. Picquenard, G. Sagon, D. Noel- described oxide films formation on Stainless Steel 316L. Samples were first vacuum-annealed at 10500C for 20 minutes and polished with diamond paste down to 1 micron. These samples were subsequently oxidized by 2000hour exposure in a primary type PWR environment at 3500C [22]. N. Arab & M. Rahimi Nezhad Soltani pointed out the effect of black oxide coating on cast iron substrate. The oxidizing solution containing sodium hydroxide, sodium nitrite, or mixtures reacts with cast iron substrate to form magnetite (Fe3O4) at a temperature of about 100-1500C [3]. The chemical reaction is reported as mM + nA z − → M m An + nze } where M denotes metal that reacts with environment and A denotes intermediary
{
environment ion. A mechanism explained for the black oxide coating on Cast Iron substrate in the presence of oxidant ingredients is that the cast Iron will react with alkaline solution to produce soluble sodium hypoferrite. Fe +
1 O 2 + 2 NaOH → Na 2 FeO 2 + H 2 O 2
The generated salt in the above chemical reaction diffuses into the blackening bath and strikes and reacts with oxidant ingredients like sodium nitrate to produce soluble sodium ferrite (Na2FeO2). This sodium ferrite reacts with supersaturated solution of two and three valence ferric oxide and by means of crystallization of this solution, magnetite oxide layer is produced on cast Iron substrates. M.LEBBAI, J.K KIM, M.M.F Yuen, P. Tong discussed black oxide coating formation on copper substrate surface by immersing into hot alkaline solutions at a temperature of 850C for a duration of 4 minutes [23]. It is reported that the role of black oxide was to improve adhesion strength of copper with various polymers and the techniques has been used since early days of printed circuit technology. Kuriacose, J Rajaram pointed out that black oxide coatings on steel can be obtained by soaking steel in a concentrated solution of sodium hydroxide, containing oxidizing agent like sodium nitrite or sodium chlorate at 800C to 900C [24]. Mel Schwartz -Encyclopedia and Handbook of Materials, Parts and Finishes describes the formation of magnetite on the steel surface by reacting with inorganic blackening solutions. Oxidizing salts are first dissolved in water then boiled and held at 138-1400C. The product surface is cleaned in an alkaline soak and then rinsed before immersion in the blackening solution. After a second rinse, the finish is sealed with rust preventers and produces finishes that vary from slightly oily to hard and dry. The black oxide finish produced on steel is composed essentially of the black oxide of iron (Fe3O4, and is considered to be a combination of FeO and Fe2O3) [25]. Steve F Crar, Arthur R Gill, Peter Smid explained the formation of black oxide coating on ferrous metal. Black oxide coatings are a chemical conversion process produced by the reaction of iron in ferrous metal with the oxidizing salts. The result of this chemical reaction is the formation of black iron oxide and magnetite on the surface
9538
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
of the metal being coated. Black oxide can be produced using molten salt bath operating at 3150C and above, a cold black solution operating at room temperature, or a hot alkaline aqueous solution operating between 2850F and 3000F (1400C and 1480C). The hot alkaline aqueous solution is most commonly used for the formation of black oxide coating on ferrous metal. This process produces a deep black finish that is consistent and uniform in appearance. Since the process is strictly a chemical reaction, there are no high or low current density areas to cause uneven coating thickness. This results in the formation of black iron oxide (magnetite) on the surface of the metal being coated. This coating is most commonly used for decorative and corrosion prevention purposes on bearings gears, small components and firearms [26]. HE Xin- kuai, CHEN Bai-zhen, LI Xiao-dong, HU Geng-sheng, WU Lu-ye, TIAN Wen-zeng pointed the technology of black colouring on stainless steel by electrochemical method. The optimum bath composition and operating conditions were obtained for blackening process on stainless steel and is reported as: 40 – 50 g/L K2Cr2O7, 15 – 20 g/L MnSO4, 15 – 20 g/L (NH4)2SO4, 20 – 40 g/L H3BO3, 20 – 30 g/L additive A, 2 g/L (NH4)6Mo7O24, duration of coating 9 – 20 min; at a temperature of 15 – 30°C; potential 3 V and current density 1 – 2 mA/cm2. They also mentioned the influence of passivation time on black colouring on stainless steel. There is an improvement in quality of film when the passivation time and colouring time is increased. Also a reactive chromate solution at high temperature is difficult to deal with since special attention must be paid to environmental problems and corrosion of material used in the reaction vessel [27]. 5. Factors influencing the conversion coating process A number of external parameters make a significant influence on the thin film coating produced by hot alkaline conversion methods. Parameters like treatment time, temperature of hot alkaline bath and percentage of sodium dichromate has a great impact on thickness of coating, average roughness and average percentage of reflectance on black oxide coatings developed on the surface of the substrate during the conversion coating process. 5.1. Effect of treatment time MOHAMED LEBBAI, Jang-Kyo KIM, W.K SZETO, MATTHEW M F YUEN, PIN TONG pointed the variation in surface roughness of black oxide coating developed on copper substrate with respect to treatment time. The roughness value and thickness of the coating increased gradually with treatment time. The surface roughness variation reported for 60sec treatment duration is as shown below in fig. 1 (a) [18]. The oxide thickness has been reported to have increased with treatment time upto 150 sec and got steady after about 180 sec duration [17]. The variation is reported as depicted in the graph (b). a
b
Fig.1. (a) Surface roughness of black oxide at different treatment time. (b) Thickness of black oxide at different treatment time.
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
9539
5.2. Effect of bath temperature The thickness of thermally grown oxide films on AISI 304 stainless steel increases from about 8nm at 1500C to about 30 nm at 4500C [21]. The variation is as shown in figure 2.
Fig. 2. Thickness of iron oxide films formed at different temperatures between 1500C and 4500C.
5.3. Effect of chemical composition of blackening bath The chemical composition of coating changes as the coating thickness increases [16]. N. Arab & M. Rahimi Nezhad Soltani explained the blackening of cast iron in conventional blackening baths offer the use of sodium salts but use of blackening bath containing potassium salts is reported to lead to higher quality and uniform coating. The application of blackening bath containing potassium salts, in addition to preventing negative effects of some elements on the cast Iron blackening also prevents decrease in the efficiency and lifetime of the bath. It also provides better adhesion of coating layer onto cast iron substrates [3]. 5.4. Effect of acid pickling on coating quality The metal specimens have been reported to undergo acid pickling after degreasing the surfaces for the removal of all surface oxides. Commonly used chemicals are HCl, H2SO4 and H3PO4 [28,29]. A study of cast iron blackening shows the improvement in adhesion of coating in the cast iron parts that underwent pickling in one molar sulphuric acid than blackened without pickling [3]. 5.5. Effect of pH on coating quality 5.5.1 Effect of pH in thickness of conversion coating The pH value of treatment bath was one of the vital factors reported to affect the thickness of chromium free conversion-coating on magnesium alloys. Accordingly in the coating developed by using a phosphate – permanganate bath, the conversion coating thickness is seem to decrease gradually with the increase of pH value as shown below figure 3(a) [30].
9540
a
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
b
Fig. 3. (a) Conversion coating thickness as a function of pH value of the solution.1-K2HPO4-150g/L,KMnO4-40g/L; 2- K2HPO4-100g/L,KMnO440g/L; 3- K2HPO4-80g/L. KMNO4-40g/L. (b) Influence of pH of electroless nickel solution on the solar absorptance of the coating.
5.5.2 Effect of pH in blackening One of the important factors that should be regulated to obtain the most favorable results in blackening is the pH of treatment solution. Vishal Saxena, R. Uma Rani, A.K Sahrma explained the effect of pH of electroless nickel solution for the formation of ultra high solar absorber black electroless nickel coatings on aluminum alloys for space application [31]. The experiments reported to the conducted in the pH range 4.0-5.5, the optimum value of this coating on aluminum alloys were obtained at a solution pH value of 4.7. At lower pH (4.0), solar absorptance of coating was lower and at higher pH (5.5) and above the electroless nickel plating solution started to decompose [19]. The variation is as shown in the graph 3(b). 6. Conclusion Though many methods have been developed for providing black oxide coating on metals, they have not been applied for conversion coatings of surgical grade steel grade 420A. Since this steel is being used extensively for minimally invasive surgical instruments, there is a scope to develop an optimum method for producing black surface on this steel to reduce its reflectivity and thereby increases the efficacy of the surgeons. Modifications to the methods discussed in this paper can be made to develop an effective technique for black oxide coating to 420A surgical grade stainless steel. References [1] Gerald McDonnell, Denise Sheard -A Practical Guide to Decontamination in Healthcare, Wiley Blackwell Publishers, John Wiley & Sons, Ltd, West Sussex, UK ISBN-10: 1444330136, 2012, pp. 70-75. [2] Howard L. Levine , M. Pais Clemente -Sinus Surgery: Endoscopic and Microscopic Approaches, Thieme Publisher, ISBN-10: 0865779724, 2004, pp. 174-178. [3] N. Arab & M. Rahimi Nezhad Soltani -A Study of Coating Process of Cast Iron Blackening, Journal of Applied Chemical Research, 9, (2009) 13-23, ISSN: 2008-3815. [4] Standard specification for stainless steels for surgical instruments-ASTM international designation: F 899 – 02. [5] Mikell P. Groover- Fundamentals of Modern Manufacturing: Materials, Processes, and systems, Fourth edition, John Wiley & Sons, Hoboken, ISBN-10: 0470467002, 2010, pp. 114-116. [6] Kean –Khoon Chew, Sahrif Hussein Sharif Zein, Abdhul Latif Ahamed – The corrosion scenario in human body: stainless steel 316L orthopaedic implants, Natural science Vol.4, No.3, (2012) 184-188. [7] Dr. Dalbir Koshal- Manufacturing Engineer’s Reference Book, 13th edition, Butterworth-Heinemann Ltd,ISBN-13 978-0750611541, 1993, pp.35-39. [8] Jingxin Yang, Fuzhai Cui, In Seop Lee-Surface Modification Of Magnesium Alloys For Biomedical Applications, Annals of Biomedical Engineering, Vol. 39, No. 7, (2011) 1857-1871. [9] BharatBhushan- Principles and Applications of Tribology, Published by Wiley India Pvt.Ltd, ISBN-047159407-5, 1999.
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
9541
[10] Peter M. Martin- Handbook of Deposition Technologies for Films and Coatings: Sience, Applications and Technology, 3rd edition, Published by William Andrew, ISBN 0815520328, 9780815520320, 2009 pp. 10-30. [11] T.S.N. Sankara Narayanan Surface Pretreatment by Phosphate Conversion Coatings- A Review, Reviews on Advanced Material Science, vol.9, No.2, (2005) 130-177. [12] Frank Hollstein, Petr Louda- Bio compatible low reflective coatings for surgical tools using reactive d.c magnetron sputtering and arc evaporation – a comparision regarding steam sterilization resistance and nickel diffusion, Surface and Coatings Technology 120-121 (1999) 672-681. [13] Monica Lira- Cantu, Angel Morales Sabio, Alex Brustenga, Pedro Gomez-Romero- Electrochemical deposition of black nickel solar absorber coatings on stainless steel AISI 316L for thermal solar cells, Solar Energy Materials & Solar Cells 87 (2005) 685-694. [14] Ales Nagode, Grega Klancnik, Heidy Schwarczova, Borut Kosec, Mirko Gojic- Analyses of defects on the surfaces of hot plates for an electric stove, Engineering Failure Analysis 23 (2012) 82-89. [15] Jan-Kyo Kim, Ricky S. C. Woo, Pamela Y.P Hung, Mohamed Lebbai- Adhesion performance of black oxide coated copper substrates: Effects of moisture sensitivity test, Surface & Coating Technology 201 (2006) 320-328. [16] A K Sharma, R Uma Rani, S M Mayanna – Thermal studies on electrodeposited black oxide coating on magnesium alloys, Thermochimica Acta 376 (2001) 67-75. [17] Mohamed LEBBAI, W.K SZETO and Jang-Kyo KIM- Optimization of black oxide coating Thickenss As Adhesion Promotoer for Copper Substrate, International Symposium on Electronic Materials & Packing (2000) 206-213. [18] MOHAMED LEBBAI, Jang-Kyo KIM, W.K SZETO, MATTHEW M F YUEN, PIN TONG- Optimization of Black Oxide Coating Thickness As An Adhesion Promoter for Copper Substance In Plastic Integrated- Circuit Packages, Journal of ELECTRONIC MATERIALS, Vol. 32, No.6 (2003) 558-563. [19] R. Uma Rani, A.K Sharma, C. Minu G.Poornima, S. Tejaswi- Studies on black electroless nickel coating on titanium alloys for spacecraft thermal control appliocations, JAppl Elctrochem (2010) 40: 333-339. [20] T.D Burleigh, T.C Doston, K.T Doston, S.J Gabay, T.B Sloan and S.G Ferrel- Anodizing Steel in KOH and NaOH Solutions: Journal of The Electrochemical Society, 154 (10) (2007) C579 – C586. [21] M.G.S Ferreira, N.E Hakiki, G.Goodlet, S. Faty, A.M.P Simoes, M. Da Cunha Belo- Influence of the Temperature of Film Formation on the Electronic Structure of Oxide Films Formed on 304 Stainless steel, Eletrochimica Acta 46 (2001) 3767-3776. [22] M. Da Cunha Belo, M. Walls, N.E Hakiki, J. Corset, E. Picquenard, G. Sagon, D. Noel- Composition, Structure and Properties of the Oxide Films Formed on the Stainless Steel 316L in a Primary Type PWR Environment, Corrosion Science, Vol. 40, No. 2/3, (1998) 447-463, [23] M.LEBBAI, J.K KIM, M.M.F Yuen , P. Tong- Effect Of Black Oxide on Interface Adhesion Between Copper Substrate & Globe- Top Resins, 4th Intern. Conf. Adhesives Joining & Coating Technology in Electronic Manufacturing (2000) 61-68. [24] J C Kuriacose, J Rajaram-Chemistry in Engineering and Technology, Vol. 2, Published by Tata McGraw Hill, ISBN-13:9780074517369, ISBN-10: 0074517368, 2010, pp 524-529. [25] Mel Schwartz -Encyclopedia and Handbook of Materials, Parts and Finishes. Second Edition, CRC Press LLC, Florida, ISBN-10: 1566766613, 2002, pp. 137-140, 489-492 & 479-490. [26] Steve F Crar, Arthur R Gill, Peter smid Technology of machine tools – seventh edition, published by Mc Graw Hill, ISBN 978-0-07351083-5, pp. 190-195. [27] HE Xin- kuai, CHEN Bai-zhen, LI Xiao-dong, HU Geng-sheng, WU Lu-ye, TIAN Wen-zeng - Technology of black colouring on stainless steel by electrochemical method, Journal of Central South University of Technology, Volume 13, Isuue 2, (April 2006) 135-140. [28] Bulent Tepe, Banihan Gunay- Evaluation of pre – Treatment processes for HRS (hot rolled steel) in powder coating, Progress in organic coatings 62 (2008), 134-144. [29] Guangyu Li, Liyuan Niu, Jianshe Lian and Zhongaho Jiang- A black phosphate coating for C1008 steel, Surface and Coatings Technology 176 (2004), 215-221. [30] Ming-Zhao, Shusen Wu, JiRong Luo, Y. Fukuda, H. Nakae- A chromium – free conversion coating of magnesium alloy by a phosphate – permanganate solution, Surface and Coatings Technology 200 (2006), 5407-5412. [31] Vishal Saxena, R. Uma Rani, A.K Sharma- Studies on ultra high solar absorber black electroless nickel coatings on aluminium alloys for space applications, Surface & Coatings Technologies 201 (2006), 855-862.
ScienceDirect Materials Today: Proceedings 4 (2017) 9534–9541
www.materialstoday.com/proceedings
ICEMS 2016
Black oxide conversion coating on metals: A review of coating techniques and adaptation for SAE 420A surgical grade stainless steel Reghuraj.A.Ra*, Saju.K.Kb a
b
Research scholar, Mechanical Engineering Division, School of Engineering, Cochin University of Science And Technology, Kalamassery, Cochin, Kerala, India. Professor, Mechanical Engineering Division, School of Engineering, Cochin University of Science And Technology, Kalamassery, Cochin, Kerala, India.
Abstract Surgical grade martensitic stainless steel SAE 420A is one of the main materials being used in the production of surgical instruments. Majority of the surgical instruments have high reflectance. Since these instruments are used for many hours in surgery rooms which involves conditions of bright lighting the user experiences heavy eye strain and lack of precision due to the high reflective nature of the material. Therefore surgical instruments with lower reflectance will be able to reduce the above undesired effects. An effective black oxide coating is seen to improve the efficacy of the surgeon and surgical instruments by providing a glare free environment at the point of surgery. This paper reviews procedures for providing a non reflective corrosion resistant and non toxic black oxide coating on metals and explores possibility to adapt it to 420A stainless steel. © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Recent Trends in Engineering and Material Sciences (ICEMS-2016). Keywords: Conversion coatings; Blackening; 420A Stainless steel; Black oxide; Reflectance.
*
Corresponding author. Tel: +91-9947379668 E-mail: [email protected]
2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Recent Trends in Engineering and Material Sciences (ICEMS2016).
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
9535
1. Introduction Stainless steels are widely used for the manufacture of surgical instruments [1]. Reflection from the surgical instruments made of surgical grade martensitic stainless steel under bright light is creating undesired difficulties to the surgeons like loss of precision, device control difficulty etc especially in laparoscopic surgeries [2,12]. The precision and device control in laparoscopic and key-hole surgeries are vital. Matte black oxide coating of surgical steels has been suggested to reduce the reflectivity of surgical grade stainless steel. Black oxide is a conversion coating formed on the metal surface as a result of chemical reaction of the metal atoms with an oxidizing agent such as atmospheric air, alkaline aqueous salt solution and molten salts. The conversion coating is a film of chemical compound formed in the reaction of the substrate substance with another substance [3]. This reaction distinguishes conversion coating from a conventional coating. Stainless steels of grade 303, 304, 410, 420A, 420B, 420C, 420 Mod. Grade 303, 304 under class-3 Austenitic stainless steel) and 410, 420A, 420B, 420C, 420 Mod comes under class 4 (Martensitic stainless steel) classifications are used for manufacturing surgical instruments [4,7]. Currently surgical equipments are manufactured from superior grade 410 stainless steels. The surgical grade martensitic stainless steel is strong, hard, and wear resistant but it has less corrosion resistance [5]. For ages it’s been a custom to employ the austenitic stainless steel, especially grade 316L, as medical grade stainless steel in orthopedic field [6]. Nomenclature SAE AISI CVD PVD
Society of Automotive Engineers American Iron and Steel Institute Chemical Vapour Deposition Physical Vapour Deposition
2. Physiochemical Surface Modification Extensive studies have been carried out on different coating methods. Jingxin Yang,Fuzhai Cui, In Seop Lee broadly classified all the various surface modification techniques which are used to improve the surface properties of Magnesium alloys employed in biomedical applications [8]. Materials and their tissue response can be changed by changing physiochemical characteristics such as energy, charge and composition of the surface. The various techniques commonly used for applying coating on metals are electroplating, electroless plating, hot dipping, Chemical Vapour Deposition (CVD), Physical Vapour Deposition (PVD), thermal spraying and conversion coatings [8]. Coating is a layer of a substance applied to the substrate surface. Coating material is normally different from the substrate material and it make possible achieving special or better surface properties of the part without changing its bulk properties like appearances, adhesion, wetability, corrosion, oxidation resistance, wear resistance, scratch resistance and hardness. Many attempts have been made to improve the anti-reflective coating on grade 300 series stainless steel which is used extensively for orthopaedic applications. This paper reviews the experiments that were conducted to obtain a coating on different metals. 3. Principle of hot alkaline/chemical conversion coating The formation and deposition process of conversion type coatings can be classified into two, chemical and electrochemical. In chemical processes oxide coating deposits are formed on the surface of substrate by simple immersion of parts in oxidizing solution, but in electrochemical, electric current plays a vital role in process control and deposition [3] [16,29]. In chemical conversion coating processes, non metallic coatings are produced by the transformation of outer atomic layers of a metal surface in to new non-metallic forms with different sets of properties from the original surface [9]. The substrate reacts with another substances which are in the form of solids, liquids or gases so that substrate surface is chemically converted into different compounds having different properties at elevated temperatures [10,11]. This reaction distinguishes conversion coating from a conventional
9536
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
coating, which is usually applied on the surface without changing its chemical state. Ferrous metals and its alloys are commercially treated to produce oxide coatings by chemical conversion of their surfaces. The most commonly used method for blackening steels and stainless steels is the immersion of metal in a hot highly alkaline solution containing an oxidizing agent and then treating them in a atmosphere of steam at 3000C – 6000C, to convert the surface to black oxide (Fe3O4) [9]. 4. Review of the coating methods Frank Hollstein, Petr Louda established that the reflection and scattering of bright light from the surface of surgical instruments made of stainless steels disturbs the visual operating field of surgeon especially during minimally invasive surgery. To reduce this problem a two layer black film of TiAlN and TiCN, developed by Physical Vapour Deposition (PVD) and unbalanced magnetron sputtering, was coated. However these two single layers do not seem to be sufficiently dense to protect the substrate against corrosion. Also the coating on the substrate gets affected by multiple sterilization of the instruments. Therefore a Nb intermediate layer as a diffusion and oxidation barrier was deposited. The long term oxidation stability of multilayer Nb/TiAlN and Nb/TiCN on SS substrate could be significantly affected by the PVD coating methods and the different conditions in reactive modes [12]. Monica Lira- Cantu, Angel Morales Sabio, Alex Brustenga, Pedro Gomez-Romero (2005) discussed about black nickel solar absorber coating on stainless steel AISI 316L for light absorbing, without reflection. The antireflection coating was used for conversion of incident solar radiation into useful heat by minimizing thermal back-radiation. The antireflection coating was developed by Electro chemical deposition and final antireflective coating on stainless steel AISI 316L was made based on TEOS (Tetra-ethylorthosilica). The black nickel solar absorber coating was done on the bright nickel coated stainless steel substrate. Nickel chloride 70 g/L, sodium chloride 30 g/L, water volume 1L were used as the chemical solution and the coating process was carried out by electrochemical deposition method. Sol-gel silica based anti reflective coating from TEOS (Tetra-ethylorthosilica) was also applied to solar surface by deep coating method with the controlled immersion velocity of 30cm/min [13]. Ales Nagode, Grega Klancnik, Heidy Schwarczova, Borut Kosec, Mirko Gojic discussed about the formation of black oxide coating on the surface of grey cast iron hot plates made for an electric stove. For this case black oxide coating is used to produce a protective dark oxide layer consisting predominantly of magnetite (Fe3O4) on the surface of hot plate. The dark oxide layer is stable at high temperatures. The most popular method of black oxide coating on cast iron is immersing the workpiece in a boiling aqueous alkaline solution of oxidizing salts [14]. The oxidation procedure is followed by a coloring procedure using a heated (about 100-1500C) oxidizing solution containing sodium hydroxide, sodium nitrite, sodium nitrate or mixtures which reacts with cast iron substrates to form magnetite (Fe3O4) [3]. Similar procedures can be adopted for 420A stainless steel. Jan-Kyo Kim, Ricky S. C. Woo, Pamela Y.P Hung, Mohamed Lebbai, in their work also mentioned the formation of black oxide coating on copper alloy. The black copper oxide coating is produced in a chemical conversion process where copper substrate is treated with mixture of high concentrated sodium chlorite and sodium hydroxide, in the ratio of 350g/L and 120 g/L at 850C for 4 minutes [15,18]. In this, the black oxide coating on copper alloy helps to improve the interfacial bond strength by improving adhesion of various polymers with copper. The moisture resistance of the substrate with black oxide coating was much higher than the bare copper substrate. A K Sharma, R Uma Rani, S M Mayanna did thermal studies on black oxide coated magnesium alloys developed using, electro deposition. The black oxide coating on magnesium alloys in this case is developed by black anodizing method. The solution is formulated using potassium dichromate, ammonium sulfate at a pH value of 5.8 and temperature ranging 230C - 270C. The heat treatment process is carried out at a temperature of 700C for 2 hours [16]. Mohamed LEBBAI, W.K SZETO and Jang-Kyo KIM developed the black oxide coating by immersing copper in to an oxidizing agent of alkaline – buffered solution at high temperature [17].
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
9537
R. Uma Rani, A.K Sharma, C. Minu G.Poornima, S. Tejaswi explained the blackening process of electroless nickel coating to produce ultra black coating on titanium alloys with higher optical properties. The formation of black colour nickel-phosphorous coating is due to the unique surface morphology of nickel oxides (NiO,NiO2) and some nickel phosphates, which gives higher solar properties especially absorptance [19]. T.D Burleigh, T.C Doston, K.T Doston, S.J Gabay, T.B Sloan and S.G Ferrel described the oxide formation on steel either in KOH or NaOH solutions with concentration anywhere from 10% to saturated. The optimum electrolytes for anodizing process for the formation of magnetite (Fe3O4) were reported as either 50% KOH or 25% NaOH. The common factor for this process is the requirement of high temperatures (2000C – 5000C) [20]. M.G.S Ferreira, N.E Hakiki, G.Goodlet, S. Faty, A.M.P Simoes, M. Da Cunha Belo- discussed the formation of oxide films formed on AISI 304 Stainless steel, which used borate buffer solution (pH 8.4) at 0.8V versus Saturated Calomel Electrode (SCE). The thermally grown oxide films were formed in air at controlled and selected temperatures between 500 and 4500C inside a furnace with a duration of 2 hours at atmospheric pressure [21]. M. Da Cunha Belo, M. Walls, N.E Hakiki, J. Corset, E. Picquenard, G. Sagon, D. Noel- described oxide films formation on Stainless Steel 316L. Samples were first vacuum-annealed at 10500C for 20 minutes and polished with diamond paste down to 1 micron. These samples were subsequently oxidized by 2000hour exposure in a primary type PWR environment at 3500C [22]. N. Arab & M. Rahimi Nezhad Soltani pointed out the effect of black oxide coating on cast iron substrate. The oxidizing solution containing sodium hydroxide, sodium nitrite, or mixtures reacts with cast iron substrate to form magnetite (Fe3O4) at a temperature of about 100-1500C [3]. The chemical reaction is reported as mM + nA z − → M m An + nze } where M denotes metal that reacts with environment and A denotes intermediary
{
environment ion. A mechanism explained for the black oxide coating on Cast Iron substrate in the presence of oxidant ingredients is that the cast Iron will react with alkaline solution to produce soluble sodium hypoferrite. Fe +
1 O 2 + 2 NaOH → Na 2 FeO 2 + H 2 O 2
The generated salt in the above chemical reaction diffuses into the blackening bath and strikes and reacts with oxidant ingredients like sodium nitrate to produce soluble sodium ferrite (Na2FeO2). This sodium ferrite reacts with supersaturated solution of two and three valence ferric oxide and by means of crystallization of this solution, magnetite oxide layer is produced on cast Iron substrates. M.LEBBAI, J.K KIM, M.M.F Yuen, P. Tong discussed black oxide coating formation on copper substrate surface by immersing into hot alkaline solutions at a temperature of 850C for a duration of 4 minutes [23]. It is reported that the role of black oxide was to improve adhesion strength of copper with various polymers and the techniques has been used since early days of printed circuit technology. Kuriacose, J Rajaram pointed out that black oxide coatings on steel can be obtained by soaking steel in a concentrated solution of sodium hydroxide, containing oxidizing agent like sodium nitrite or sodium chlorate at 800C to 900C [24]. Mel Schwartz -Encyclopedia and Handbook of Materials, Parts and Finishes describes the formation of magnetite on the steel surface by reacting with inorganic blackening solutions. Oxidizing salts are first dissolved in water then boiled and held at 138-1400C. The product surface is cleaned in an alkaline soak and then rinsed before immersion in the blackening solution. After a second rinse, the finish is sealed with rust preventers and produces finishes that vary from slightly oily to hard and dry. The black oxide finish produced on steel is composed essentially of the black oxide of iron (Fe3O4, and is considered to be a combination of FeO and Fe2O3) [25]. Steve F Crar, Arthur R Gill, Peter Smid explained the formation of black oxide coating on ferrous metal. Black oxide coatings are a chemical conversion process produced by the reaction of iron in ferrous metal with the oxidizing salts. The result of this chemical reaction is the formation of black iron oxide and magnetite on the surface
9538
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
of the metal being coated. Black oxide can be produced using molten salt bath operating at 3150C and above, a cold black solution operating at room temperature, or a hot alkaline aqueous solution operating between 2850F and 3000F (1400C and 1480C). The hot alkaline aqueous solution is most commonly used for the formation of black oxide coating on ferrous metal. This process produces a deep black finish that is consistent and uniform in appearance. Since the process is strictly a chemical reaction, there are no high or low current density areas to cause uneven coating thickness. This results in the formation of black iron oxide (magnetite) on the surface of the metal being coated. This coating is most commonly used for decorative and corrosion prevention purposes on bearings gears, small components and firearms [26]. HE Xin- kuai, CHEN Bai-zhen, LI Xiao-dong, HU Geng-sheng, WU Lu-ye, TIAN Wen-zeng pointed the technology of black colouring on stainless steel by electrochemical method. The optimum bath composition and operating conditions were obtained for blackening process on stainless steel and is reported as: 40 – 50 g/L K2Cr2O7, 15 – 20 g/L MnSO4, 15 – 20 g/L (NH4)2SO4, 20 – 40 g/L H3BO3, 20 – 30 g/L additive A, 2 g/L (NH4)6Mo7O24, duration of coating 9 – 20 min; at a temperature of 15 – 30°C; potential 3 V and current density 1 – 2 mA/cm2. They also mentioned the influence of passivation time on black colouring on stainless steel. There is an improvement in quality of film when the passivation time and colouring time is increased. Also a reactive chromate solution at high temperature is difficult to deal with since special attention must be paid to environmental problems and corrosion of material used in the reaction vessel [27]. 5. Factors influencing the conversion coating process A number of external parameters make a significant influence on the thin film coating produced by hot alkaline conversion methods. Parameters like treatment time, temperature of hot alkaline bath and percentage of sodium dichromate has a great impact on thickness of coating, average roughness and average percentage of reflectance on black oxide coatings developed on the surface of the substrate during the conversion coating process. 5.1. Effect of treatment time MOHAMED LEBBAI, Jang-Kyo KIM, W.K SZETO, MATTHEW M F YUEN, PIN TONG pointed the variation in surface roughness of black oxide coating developed on copper substrate with respect to treatment time. The roughness value and thickness of the coating increased gradually with treatment time. The surface roughness variation reported for 60sec treatment duration is as shown below in fig. 1 (a) [18]. The oxide thickness has been reported to have increased with treatment time upto 150 sec and got steady after about 180 sec duration [17]. The variation is reported as depicted in the graph (b). a
b
Fig.1. (a) Surface roughness of black oxide at different treatment time. (b) Thickness of black oxide at different treatment time.
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
9539
5.2. Effect of bath temperature The thickness of thermally grown oxide films on AISI 304 stainless steel increases from about 8nm at 1500C to about 30 nm at 4500C [21]. The variation is as shown in figure 2.
Fig. 2. Thickness of iron oxide films formed at different temperatures between 1500C and 4500C.
5.3. Effect of chemical composition of blackening bath The chemical composition of coating changes as the coating thickness increases [16]. N. Arab & M. Rahimi Nezhad Soltani explained the blackening of cast iron in conventional blackening baths offer the use of sodium salts but use of blackening bath containing potassium salts is reported to lead to higher quality and uniform coating. The application of blackening bath containing potassium salts, in addition to preventing negative effects of some elements on the cast Iron blackening also prevents decrease in the efficiency and lifetime of the bath. It also provides better adhesion of coating layer onto cast iron substrates [3]. 5.4. Effect of acid pickling on coating quality The metal specimens have been reported to undergo acid pickling after degreasing the surfaces for the removal of all surface oxides. Commonly used chemicals are HCl, H2SO4 and H3PO4 [28,29]. A study of cast iron blackening shows the improvement in adhesion of coating in the cast iron parts that underwent pickling in one molar sulphuric acid than blackened without pickling [3]. 5.5. Effect of pH on coating quality 5.5.1 Effect of pH in thickness of conversion coating The pH value of treatment bath was one of the vital factors reported to affect the thickness of chromium free conversion-coating on magnesium alloys. Accordingly in the coating developed by using a phosphate – permanganate bath, the conversion coating thickness is seem to decrease gradually with the increase of pH value as shown below figure 3(a) [30].
9540
a
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
b
Fig. 3. (a) Conversion coating thickness as a function of pH value of the solution.1-K2HPO4-150g/L,KMnO4-40g/L; 2- K2HPO4-100g/L,KMnO440g/L; 3- K2HPO4-80g/L. KMNO4-40g/L. (b) Influence of pH of electroless nickel solution on the solar absorptance of the coating.
5.5.2 Effect of pH in blackening One of the important factors that should be regulated to obtain the most favorable results in blackening is the pH of treatment solution. Vishal Saxena, R. Uma Rani, A.K Sahrma explained the effect of pH of electroless nickel solution for the formation of ultra high solar absorber black electroless nickel coatings on aluminum alloys for space application [31]. The experiments reported to the conducted in the pH range 4.0-5.5, the optimum value of this coating on aluminum alloys were obtained at a solution pH value of 4.7. At lower pH (4.0), solar absorptance of coating was lower and at higher pH (5.5) and above the electroless nickel plating solution started to decompose [19]. The variation is as shown in the graph 3(b). 6. Conclusion Though many methods have been developed for providing black oxide coating on metals, they have not been applied for conversion coatings of surgical grade steel grade 420A. Since this steel is being used extensively for minimally invasive surgical instruments, there is a scope to develop an optimum method for producing black surface on this steel to reduce its reflectivity and thereby increases the efficacy of the surgeons. Modifications to the methods discussed in this paper can be made to develop an effective technique for black oxide coating to 420A surgical grade stainless steel. References [1] Gerald McDonnell, Denise Sheard -A Practical Guide to Decontamination in Healthcare, Wiley Blackwell Publishers, John Wiley & Sons, Ltd, West Sussex, UK ISBN-10: 1444330136, 2012, pp. 70-75. [2] Howard L. Levine , M. Pais Clemente -Sinus Surgery: Endoscopic and Microscopic Approaches, Thieme Publisher, ISBN-10: 0865779724, 2004, pp. 174-178. [3] N. Arab & M. Rahimi Nezhad Soltani -A Study of Coating Process of Cast Iron Blackening, Journal of Applied Chemical Research, 9, (2009) 13-23, ISSN: 2008-3815. [4] Standard specification for stainless steels for surgical instruments-ASTM international designation: F 899 – 02. [5] Mikell P. Groover- Fundamentals of Modern Manufacturing: Materials, Processes, and systems, Fourth edition, John Wiley & Sons, Hoboken, ISBN-10: 0470467002, 2010, pp. 114-116. [6] Kean –Khoon Chew, Sahrif Hussein Sharif Zein, Abdhul Latif Ahamed – The corrosion scenario in human body: stainless steel 316L orthopaedic implants, Natural science Vol.4, No.3, (2012) 184-188. [7] Dr. Dalbir Koshal- Manufacturing Engineer’s Reference Book, 13th edition, Butterworth-Heinemann Ltd,ISBN-13 978-0750611541, 1993, pp.35-39. [8] Jingxin Yang, Fuzhai Cui, In Seop Lee-Surface Modification Of Magnesium Alloys For Biomedical Applications, Annals of Biomedical Engineering, Vol. 39, No. 7, (2011) 1857-1871. [9] BharatBhushan- Principles and Applications of Tribology, Published by Wiley India Pvt.Ltd, ISBN-047159407-5, 1999.
Reghuraj.A.R / Materials Today: Proceedings 4 (2017) 9534–9541
9541
[10] Peter M. Martin- Handbook of Deposition Technologies for Films and Coatings: Sience, Applications and Technology, 3rd edition, Published by William Andrew, ISBN 0815520328, 9780815520320, 2009 pp. 10-30. [11] T.S.N. Sankara Narayanan Surface Pretreatment by Phosphate Conversion Coatings- A Review, Reviews on Advanced Material Science, vol.9, No.2, (2005) 130-177. [12] Frank Hollstein, Petr Louda- Bio compatible low reflective coatings for surgical tools using reactive d.c magnetron sputtering and arc evaporation – a comparision regarding steam sterilization resistance and nickel diffusion, Surface and Coatings Technology 120-121 (1999) 672-681. [13] Monica Lira- Cantu, Angel Morales Sabio, Alex Brustenga, Pedro Gomez-Romero- Electrochemical deposition of black nickel solar absorber coatings on stainless steel AISI 316L for thermal solar cells, Solar Energy Materials & Solar Cells 87 (2005) 685-694. [14] Ales Nagode, Grega Klancnik, Heidy Schwarczova, Borut Kosec, Mirko Gojic- Analyses of defects on the surfaces of hot plates for an electric stove, Engineering Failure Analysis 23 (2012) 82-89. [15] Jan-Kyo Kim, Ricky S. C. Woo, Pamela Y.P Hung, Mohamed Lebbai- Adhesion performance of black oxide coated copper substrates: Effects of moisture sensitivity test, Surface & Coating Technology 201 (2006) 320-328. [16] A K Sharma, R Uma Rani, S M Mayanna – Thermal studies on electrodeposited black oxide coating on magnesium alloys, Thermochimica Acta 376 (2001) 67-75. [17] Mohamed LEBBAI, W.K SZETO and Jang-Kyo KIM- Optimization of black oxide coating Thickenss As Adhesion Promotoer for Copper Substrate, International Symposium on Electronic Materials & Packing (2000) 206-213. [18] MOHAMED LEBBAI, Jang-Kyo KIM, W.K SZETO, MATTHEW M F YUEN, PIN TONG- Optimization of Black Oxide Coating Thickness As An Adhesion Promoter for Copper Substance In Plastic Integrated- Circuit Packages, Journal of ELECTRONIC MATERIALS, Vol. 32, No.6 (2003) 558-563. [19] R. Uma Rani, A.K Sharma, C. Minu G.Poornima, S. Tejaswi- Studies on black electroless nickel coating on titanium alloys for spacecraft thermal control appliocations, JAppl Elctrochem (2010) 40: 333-339. [20] T.D Burleigh, T.C Doston, K.T Doston, S.J Gabay, T.B Sloan and S.G Ferrel- Anodizing Steel in KOH and NaOH Solutions: Journal of The Electrochemical Society, 154 (10) (2007) C579 – C586. [21] M.G.S Ferreira, N.E Hakiki, G.Goodlet, S. Faty, A.M.P Simoes, M. Da Cunha Belo- Influence of the Temperature of Film Formation on the Electronic Structure of Oxide Films Formed on 304 Stainless steel, Eletrochimica Acta 46 (2001) 3767-3776. [22] M. Da Cunha Belo, M. Walls, N.E Hakiki, J. Corset, E. Picquenard, G. Sagon, D. Noel- Composition, Structure and Properties of the Oxide Films Formed on the Stainless Steel 316L in a Primary Type PWR Environment, Corrosion Science, Vol. 40, No. 2/3, (1998) 447-463, [23] M.LEBBAI, J.K KIM, M.M.F Yuen , P. Tong- Effect Of Black Oxide on Interface Adhesion Between Copper Substrate & Globe- Top Resins, 4th Intern. Conf. Adhesives Joining & Coating Technology in Electronic Manufacturing (2000) 61-68. [24] J C Kuriacose, J Rajaram-Chemistry in Engineering and Technology, Vol. 2, Published by Tata McGraw Hill, ISBN-13:9780074517369, ISBN-10: 0074517368, 2010, pp 524-529. [25] Mel Schwartz -Encyclopedia and Handbook of Materials, Parts and Finishes. Second Edition, CRC Press LLC, Florida, ISBN-10: 1566766613, 2002, pp. 137-140, 489-492 & 479-490. [26] Steve F Crar, Arthur R Gill, Peter smid Technology of machine tools – seventh edition, published by Mc Graw Hill, ISBN 978-0-07351083-5, pp. 190-195. [27] HE Xin- kuai, CHEN Bai-zhen, LI Xiao-dong, HU Geng-sheng, WU Lu-ye, TIAN Wen-zeng - Technology of black colouring on stainless steel by electrochemical method, Journal of Central South University of Technology, Volume 13, Isuue 2, (April 2006) 135-140. [28] Bulent Tepe, Banihan Gunay- Evaluation of pre – Treatment processes for HRS (hot rolled steel) in powder coating, Progress in organic coatings 62 (2008), 134-144. [29] Guangyu Li, Liyuan Niu, Jianshe Lian and Zhongaho Jiang- A black phosphate coating for C1008 steel, Surface and Coatings Technology 176 (2004), 215-221. [30] Ming-Zhao, Shusen Wu, JiRong Luo, Y. Fukuda, H. Nakae- A chromium – free conversion coating of magnesium alloy by a phosphate – permanganate solution, Surface and Coatings Technology 200 (2006), 5407-5412. [31] Vishal Saxena, R. Uma Rani, A.K Sharma- Studies on ultra high solar absorber black electroless nickel coatings on aluminium alloys for space applications, Surface & Coatings Technologies 201 (2006), 855-862.