Research Publications

Research Publications

1. "Development of electroless Ni-Zn-P/nano-Ti02 composite coatings and their properties", S. Ranganatha, T. V .Venkatesha and K.Vathsala, Applied Surface Science, 256 (2010) 7377-7383

2. "Process and properties of NiCuP-Zr02 composite coatings", S. Ranganatha, T.V. Venkatesha, K. Vathsala, Materials Research Bulletin, 47 (2012) 635-645.

3. "Anticorrosive electroless Ni-P films for mild steel materials", S. Ranganatha and T.V. Venkatesha, Anticorrosion methods and materials 59(2) (2012) 69-75.

4. "Studies on the preparation and properties of electroless Ni-W-P alloy coatings and its nano-MoS2 composite", S. Ranganatha and T.V. Venkatesha, Physica Sm/jto 85 (2012) 035601.

5. "Electroless Ni-W-P coatings and its nano-WS2 composite: Preparation and properties", S. Ranganatha, T.V. Venkatesha and K. Vathsala, Industrial & Engineering Chemistry Research, 51 (2012) 7932-7940.

6. "Electrochemical studies on Zn/nano-Ce02 electrodeposited composite coatings", S. Ranganatha, T.V.Venkatesha, K.Vathsala and M.K. Punith kumar. Surface & Coating Technology, 208 (2012) 64-72.

7. "Development of high performance electroless Ni-P-Halloysite Nanotube composite coatings", S. Rangantha, T.V. Venkatesha and K. Vathsala, Applied Surface Science.

8. "Zn-WS2 nanocomposite coating on mild steel: Electrochemical aspects", fArticle in press) Synthesis and reactivity in inorganic, Metal-Organic and Nano-Metal Chemistry, K. Vathsala, T.V. Venkatesha, S. Ranganatha and M.K. Punith kumar 42 (2012)779-785.

9. "Metol as corrosion inhibitor for zinc", B M Praveen, T V Venkatesha, K G Chandrappa, S E Nataraj, M K Punith Kumar, S Ranganatha, C M Praveen Kumar P Sarala and M K Pavithra, Transactions of the Indian Institute of Metals, Published online 26 April 2012, DOI 10.1007/sl2666-012-0133-x.

Papers presented in Conferences/Scientific meets

Papers presented in Conferences and Scientific meets

1. National seminar on Nanotechnology- Past, Present and Future on 4* April 2008 at Kuvempu University, Organized by Dept of Chemistry, Shankaraghatta.

2. International Conference on Recent Advances in Industrial Electrochemical Science and Technology (ICRAIEST-2009), 5-7 November-2009 at Mangalore organized by Mangalore University. Paper presented: "Corrosion behavior of Ni-P electroless thin film coatings"

3. National level Conference on Recent Advances in Electroanalytical Techniques held at Gandhigram rural university, Deemed University, Gandhigram, Tamilnadu in 2010. Paper presented on "Development of Ni-Zn-P/Nano-Ti02 Composite Coating and Their properties"

4. National Conference on Recent Trends in Chemical Research-2010 held at NITK Surathkal, paper presented on "Electroless deposition of Ni-Cu-P-Zr02 composites on mild steel and corrosion behavior of the deposits".

5. National level Conference on Recent Trends in Chemical and Biological Sciences-2010 Kuvempu University and paper presented on "Electroless deposition of Ni-Cu-P-Zr02 composites on mild steel and Corrosion behavior of the deposit".

6. Selected by MHRD/DST, Govt, of India to participate in "Third Science Conclave: A Congregation of Nobel Laureates" organized by Indian Institute of Information Technology, Allahabad, held during 08-14, December 2010.

7. National conference on "Social Relevance of Chemical Sciences, SRCS-2011 held at Kuvempu University and presented a research paper entitled "Process and properties of Ni-W-P/nano-WS2 composite coatings" during 26-27* of March 2011.

8. Participated in National level workshop on "Usage of instruments for nanotechnology applications" held at Dept. of Nanoscience and Technology, Kuvempu University on 25* April 2011.

9. Participated in one day workshop on "Celebration of International Year of Chemistry" on October 2011.

10. Attended three days workshop, KSTA sponsored Special lecture Series on Chemistry held at Kuvempu University during 15-17* November 2011.

11. Participated in National conference on chemical and Environmental Science -2011 (NCCES -2011) held at Mahavir Jain college, Bengaluru during 28* and 29* December 2011 and presented paper on "Effect of MWCNTs on the properties of Zinc and its alloy coatings".

Papers presented in Conferences/Scientific meets

12. Participated in 'Special Lecture Series Chemistry' organized by Dept. of Chemistry, Kuvempu University and Kamataka Science and Technology Academy, Govt, of Kamataka, at Dept. of Chemistry, Kuvempu University during 15* - 17 November, 2011 in the celebration of International year of chemistry 2011.

13. Participated in Two day Workshop On "Electrochemical Techniques for Nano-Scale Surface Engineering" (ECTNSE-2012) held at BAARC-Mumbai during 5* and 6* January, 2012 and presented poster entitled "Effect of MWCNTs on the properties of Zinc and its alloy coatings".

14. Participated for two days National seminar on "Chemistry: Our life, our future" (NSCOF-2012) organized by Dept. of Chemistry, Kuvempu University during 25* and 26* of April 2012.

pubs.acs.org/IECR l&EC r e s e a r c h industrial & Engrneering Chemistry Research

Electroless Ni-W-P Coating and Its Nano-WSj Composite: Preparation and Properties S. Ranganatha,^ T.V. Venkatesha,*'^ and K. Vathsala*

Department of Studies in Chemistry, School of Chemical Sciences, Kuvempu University, Shankaraghatta-5774S1, Shimoga, Kamataka, India

Nanotribology Laboratory, Mechanical Engineering Department, Indian Institute of Science, Bangalore-560012, India

ABSTRACT: The ternary alloy Ni—W—P and its WS2 nanocomposite coatings were successfully obtained on low-carbon steel using the electroless plating technique. The sodium tungstate (Na2W04) concentration in the bath was varied to obtain N i - W -P deposits containing various Ni and P contents. WS^ composite was obtained with a suitable concentration of Na2W04 in N i - P coating. These deposits were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX) studies. The corrosion behavior was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies in 3.S wt % NaCI solutions, and the corrosion rates of the coatings for N i - P , N i - W - P , and N i - W - P - W S z were found to be 2.571 X 10"^ 8.219 X 10"' , and 7.986 X 1 0 ' ' g/h, respectively. An increase in the codeposition of alloying metal tungsten (W) enhanced the corrosion resistance and microhardness and changed the structure and morphology of the deposits. Incorporation of WSj nanoparticles to Ni—W-P alloy coating reduced the coefficient of friction from 0.16 to 0.11 and also helped in improving the corrosion resistance of the coating further.

• INTRODUCTION Autocatalytic electroless deposition is a widely used surface modification process for numerous applications because of its deposit properties such as excellent corrosion and wear resistance, deposit uniformity, solderbility, electrocatalytic activity, etc. "^ It has been found that most of the properties of electroless nickel deposits are structure dependent, and the structure is sensitive to the P content of the coatings. Though electroless binary N i - P alloys have had extensive applications due to their properties, the electroless ternary alloys such as N i - W - P , N i - C u - P , N i - Z n - P , N i - C o - P , N i - R e - P , N i -Sn—P, and Ni—Fe—P, etc., have been developed. To meet additional meticulous demands they can be tailored to required applications such as corrosion resistance, wear resistance, thermal stability, electrical properties, and some special physical performances like magnetic properties, solderability, and polishability.'""'^ Moreover, the work carried out by various researchers advocates better performance of ternary alloy coatings with embedded nanomaterials.

Tungsten (W), being a refractory metal, cannot be deposited from any aqueous solution. However, W alloys with the iron group transition metals can be readily deposited from aqueous solutions containing the W metal ions. An electroless ternary alloy with elements other than iron, namely, Ni—W—P, has been reported by Pearlstein et al. Introduction of W in electroless N i - P matrix improves properties such as the wear resistance, corrosion resistance, thermal stability, electrical resistance.'^^"^'* Even small amount of W codeposition affects the chemical composition, morphology, and roughness of N i - P deposits. This may be the cause of the unique properties of W such as high hardness, higher melting point, lower coefficient of linear thermal expansion, high tensile strength, etc. Eventually this created a tendency in the scientffic community to develop electroless ternary Ni—W—P alloys. The Ni—W—P deposits

specifically replaced hexavalent chromium and serve as environmentally friendly materials. Deposition of N i - W - P ternary alloys with nanoparticles incorporation is of foremost importance because of the enhanced properties of the coatings. To prepare composites of electroless N i - W - P coatings, various efforts to use nanoparticles (Al^Oj, PTFE, Ti02j ZTO2, etc.) have successfiolly been made. ' " The presence of quaternary components [added nanomaterials] in the electro­less ternary nickel alloy matrix affects the surface morphology and consequently its chemical and mechanical properties. The layered hollow structure and quasi-spherical shape makes the W S T particle demonstrate interesting tribological character­istics which makes them a favorable lubricant under several conditions, where fluids are imable to support a heavy load and are squeezed away from the contact area. ~ Some researchers have revealed that the tribological properties of these nanoparticles are excellent, so they are prospective lubricants for aerospace applications. In addition, these particles have been utihzed to design WS2-impregnated orthodontic stainless steel and have found medical applications. Composite coating is an efficient way of surface finishing and engineering; however, preparation of WS^—metal/alloy com­posites and their corrosion studies in the literature are very limited and seek more investigation. In the present work, an attempt has been made to fabricate corrosion-resistant Ni—W— P coating by varying the W metal. In addition, a composite with WS2 nanoparticles is prepared. Studies on the deposition, composition, surface nature, structure, electrochemical, and mechanical properties have been carried out successftilly.

Received: January 11, 2012 Revised: May 8, 2012 Accepted: May 10, 2012 Published: May 10, 2012

y^(25 P u b l i C S t i O n S ® ^^^^ American Chemical Society 7932 dx.doi.Ofg/10.1021/ie300104wl/nd. Eng. Chem. Res. 2012, 51, 7932-7940

Applied Surface Science 256 (2010) 7377-7383

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Applied Surface Science

journal homepage: www.elsevler.com/locate/apsusc

Development of electroless Ni-Zn-P/nano-Ti02 composite coatings and their properties S. Ranganatha, T.V. Venkatesha*, K. Vathsala Department of Studies in Chemistry, School of Chemical Sciences, Kuvempu University, Shankaraghatta, Shimoga 577457, Kamataka. India

A R T I C L E I N F O

Article history; Received 8 February 2010 Received in revised form 9 April 2010 Accepted 20 IVlay 2010 Available online 27 May 2010

Keywords: Electroless Ni-Zn-P-Ti02 Composites Metal matrix Coatings Corrosion Microstructure

A B S T R A C T

Ni-Zn-P-Ti02 composite coatings were successfully obtained on low carbon steel by electroless plating technique. Deposits were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive analysis (EDS) studies. The hardness and microstructure of as plated and heat treated Ni-Zn-P and Ni-Zn-P-Ti02 composite coatings were analyzed. The change in microstructure and higher hardness was noticed for heat treated composite. The corrosion resistance behavior of as plated and heat treated Ni-Zn-P and Ni-Zn-P-TiOj coatings was investigated by anodic polarization, Tafel plots and electrochemical impedance spectroscopic (EIS) studies in 3.5 wt% NaCl solution. The composite coating exhibited enhanced corrosion resistance property over Ni-Zn-P coating.

® 2010 Elsevier B.V. All rights reserved.

1. Introduction

Electroless deposition, an autocatalytic reduction of metals and alloys, offers an attractive and alternate method of producing a coating of higher Ni content and it has been known to form a thin and uniform deposit on substrate when compared to elec­troplating. Electroless Ni coatings have gained popularity due to their inherent properties like excellent corrosion, wear and abra­sion resistance. The deposit properties and structure are mainly dependant on amount of codeposited P. The coating property can be further enhanced by composing one or more metallic elements like 2n. Cu, Co, Fe, Sn, W, Mo, etc. in Ni-P matrix. The electroless Ni poly alloy deposition is considered as the most successful method to alter the physical and chemical properties of binary Ni-P alloy deposits [1-4).

The incorporation of Zn into Ni-P matrix has great impact on its microstructure, mechanical and electrochemical properties [5]. The electrochemical properties of Ni-Zn-P alloy have revealed that these coatings possess more noble character compared to other ternary alloys (6J. Also Ni-Zn-P coatings have been found applica­tions in electrocatalysis and under-bump metallization of solder joints [7,8) and turned out to be of great importance. Previous efforts in literature have shown that Ni-Zn-P plating follows nor-

* Corresponding author. Tel.; +91 9448855079: fax: +91 08282 256255. E-mail address: drtwenkatesha®yahoo.co.uk (T.V. Venkateslia).

mal deposition with high Ni content of about 80-90%. However, in these cases, the amount of Zn remains low at around 10wt% and hence the potential will be more positive to steel [9]. Thus these deposits, although offering excellent corrosion resistance, could not be used as a sacrificial coating to steel. Veeraraghavan et al. increased the Zn content in the coating from 10.8 to 17.9 wt% and resulted coatings performed the sacrificial behavior [10). Incorpo­ration of Zn causes transformation of the amorphous structure of Ni-P into a crystalline, which is due to reduced P content [ 11,12). It was also mentioned that, addition of Zn into electroless Ni-P matrix improves the corrosion resistance of the coating (13).

Also the incorporation of nanosized particles with in Ni-P auto­catalytic coatings greatly improved their properties and imparts new functional features to the coating performance, which finally enhanced their application in different fields [14).

The productions of particle reinforced composite films can be achieved by deposition of the matrix material from a plating solu­tion containing particles such as TiOa, SiC, AI2O3, Zr02, WC, M0S2, Si02, PTFE, and PE. Of these particles, Ti02 has attracted much interest in research community due to its wide applications in engineering materials. It improves wear resistance, hardness and corrosion resistance and other properties such as electrocatalysis and photocatalysis [1,15-23).

The present work aims to prepare Ni-Zn-P and Ni-Zn-P-Ti02 electroless coatings on mild steel and to evaluate its microstructure, hardness and corrosion resistance.

0169-4332/$ - see front matter © 2010 Elsevier B.V. Ml rights reserved. doi:10.1016/j.apsusc.2010.05.076

Materials Research Bulletin 47 (2012) 635-645

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Materials Research Bulletin

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Process and properties of electroless Ni-Cu-P-Zr02 nanocomposite coatings S. Ranganatha^ T.V. Venkatesha •"•*, K. Vathsala'' 'Department of Studies in Chemistry, School of Chemical Sciences, Kuvempu University, Shankaraghatta 577451, Shimoga, Kamataka, India *' Nanotribology Laboratory. Mechanical engineering department, Indian Institute of Science, Bangalore, India

A R T I C L E I N F O A B S T R A C T

Article history: Received 15 April 2011 Received in revised form 18 November 2011 Accepted 22 December 2011 Available online 31 December 2011

Keywords: A. Alloys A. Composites C. Impedance spectroscopy D. Electrochemical properties D. Mechanical properties

Electroless Ni-Cu-P-ZrOz composite coating was successfully obtained on low carbon steel matrix by electroless plating technique. Coatings with different compositions were obtained by varying copper as ternary metal and nano sized zirconium oxide particles so as to obtain elevated corrosion resistant Ni-P coating. Microstnjcture, crystal structure and composition of deposits were analyzed by SEM. EDX and XRD techniques. The corrosion behavior of the deposits was studied by anodic polarization. Tafel plots and electrochemical impedance spectroscopy (EIS) in 3.5% sodium chloride solution. The Zr02 incorporated Ni-P coating showed higher corrosion resistance than plain Ni-P. The introduction of copper metal into Ni-P-Zr02 enhanced the protection ability against corrosion. The influence of copper metal and nanopaiticles on microhardness of coatings was evaluated.

O 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Electroless Ni-P (ENP) thin films are often considered as engineering coatings on account of their exceptionally high hardness, remarkable wear and corrosion resistance properties. They are known to have good corrosion resistance in various media like mineral and organic acids, chlorinated and fluorinated atmospheres. Their deposit structure and properties mainly depend on the amount of codeposited phosphorous and further improved by codepositing one or more metallic elements with Ni-P matrix. Various metals like Cu, Zn, Fe, Sn, W, Re, Mo etc. are codeposited in electroless nickel matrix to improve electrochemi­cal, thermal and mechanical properties | l - 6 ] . The emergence of electroless Ni-P poly alloy deposits is considered as the most effective method to alter the chemical and physical properties of binary Ni-P alloy deposits. Initially the copper ions were added to the electroless Ni-P plating baths as a stabilizer, primarily to replace the other sulphur bearing stabilizers. Copper ions improved the solution stability without significantly retarding the deposition rate [7]. In many electroless plating bath the Pb^^ ions are also used as stabilizer. As lead ions in excess are biotoxic and give fatal damage to the brain and nerves, hence lead free processes are in demand. The stabilizer plays a mysterious role in the ENP process. The copper ions are selected as a model stabilizer for replacing lead ions. The introduction of copper ions into electroless Ni-P bath was actually to stabilize the bath by

• Corresponding author. Tel.; +91 9448855079; fax; +91 08282 256255. E-mail address: drtwenkatesha@yahoo.co.uk (TV. Venkatesha).

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preventing the propagation of colloidal nickel particles that lead to catastrophic precipitation of Ni blacks in the plating bath. The choice of Cu-̂ * ions is mainly based on the facts that, Cu^* ions have been reported with stabilizing functions and they provide a wider concentration window than lead ions for operation [8).

The codeposited copper in Ni-P matrix has immense effect on deposit characteristics and recent studies have indicated that properties like smoothness, brightness, ductility, higher thermal stability and corrosion resistance are superior to those of the electroless Ni-P coatings [9-14]. They show low temperature coefficient of resistance and finds application in thin film resistors and metal film resistors. In addition, the inclusion of Cu in Ni-P matrix increases the wetting property and act as an excellent barrier for solder bump 15]. With these profound technological applications the electroless Ni-Cu-P has drawn much interest among the researchers.

Furthermore, composite coarings can be generated for the bet terment of deposit properties and they can offer desirable service parameters. Metal carbides, oxides, nitrides, silicides, nonmetals and organic polymers like PTFE powders and fibers are most commonly incorporated parricles into Ni-P matrix. The superior mechanical and electrochemical properties of Ni-Cu-P coatings and their composites with PTFE, CNTs advocate the importance of codeposited copper and incorporated nanomaterial [15-17] . Zirconium has been found to be very efficient additive in its oxide form, to electroless Ni-P binary coatings and ternary alloys too. Zr02 is a refractory material and it offers chemical and corrosion inertness to temperatures even above the melting point of alumina. Low thermal conductivity, high strength, high fracture toughness, excellent wear resistance, high hardness, good

C Model APSUSC 242201-S

Applied Surface Science xxx (2012) xxx-xxx

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Applied Surface Science

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Development of high performance electroless Ni-P-HNT composite coatings Qi S. Ranganatha^.T.V. Venkatesha^-*, K. Vathsala''

' Department of studies m chemistry. School of chemical sciences, Kuvempu university, ShanltaTtigtuitta-577451, SMmoga, Karnataka, India ''Nanotribology laboratory, Meclxmical engineering department, Indian Institute of Science. Bangalore S600I2. Kamotaka. India

A R T I C L E I N F O

Article history: Received 17 March 2012 Received in revised form 2 August 2012 Accepted 5 September 2012 Available online xxx

Keywords; ElertrolessNi P Halloysite nanotubes Composite coating Corrosion Micro hardness Friction

A B S T R A C T

Halloysite nanotubes (HNTs) of the dimension 50nmxl- ip .n i (diameterx length) are utililized to fabricate the alloy composite by employing electroless/autocatalytic deposition technique. Electroless Ni-P-HNT binary alloy composite coatings are prepared successfully on low carbon steel. These nano­tubes were made to get inserted/incorporated into nickel matrix and corresponding composites are examined for their electrochemical, mechanical and tribological performances and compared with that of plain Ni-P. The coatings were characterized using scanning electron microscopy (SEM) and Energy dispersive X-ray analysis (EDX) techniques to analyze surface nature and composition correspondingly. Small amount of incorporated HNTs made Ni-P deposits appreciable enhancement and betterment in corrosion resistance, hardness and friction resistance. This drastic improvement in the properties reflects the effect of addition of HNTs into Ni-P matrix leading to thedevelopment of high performance Ni-P-HNT composite coatings.

© 2012 Published by Elsevier B.V.

1. Introduction

Electroless Ni-P binary alloy coatings have many properties that are superior to those of electrodeposited nickel. Because of phosphorous content, electroless nickel is harder and has better corrosion resistance. The electroless nickel composites combine the unique properties of conventional electroelss nickel deposits such as uniformity of deposition over complex geometries, high hard­ness and good corrosion resistance with those of abrasive materials possessing tribological wear resistance. The ability to reinforce sec­ond phase materials such as diamond, T1O2, SiC, AI2O3, Zt02, M0S2, WS2, Ce02, Si3 N4, PTFE and CNTs within metal matrix by electroless plating technique facilitates development of composite coatings which offers tremendous applications 11-7].

Halloysite nanotubes (HNTs) are a kind of naturally occurring aluminosilicate clay with a predominantly hollow nanotube struc­ture and can be obtained from the natural environment Halloysite is mainly composed of a twtnlayered aluminosilicate with the composition Al2Si205(OH)4 2H2O. chemically similar to kaolinite, dickite or nacrite, differing mainly in the morphology of crystal. It is a layered clay mineral, consisting of one alumina octahedron sheet and one silica tetrahedron sheet in a 1:1 stoichiometric ratio. The length of HNTs varies in the range of 1-15 p,m. HNTs have an

* Corresponding author. Tel.; +91 9448855079; fax: +91 08282 256255. E-mail addresses: kamath.ranganat)]®gmail.com (S. Ranganatha).

drtwenkatesha9yahooxo.uk (T.V. Venkateslia), vathsala.mahesh©gmail.com {K,Vaths3ia).

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inner diameter of 10-30nm and an outer diameter of 50-70 nm, depending on the deposits. The chemical properties of the HNTs' outermost surface are similar to the properties of Si02, while the properties of the inner cylinder core could be associated with those of AI2O3 [8].

Nanotubes with a hollow cavity have attracted a great deal of interest in both scientific and industrial fields. They possess novel physical and chemical properties derived from the structural ver­satility and provide opportunities for advanced applications in the fields of electronics, optics, catalysis, energy storage, and biological systems.

Since HNTs possess some excellent characteristics, such as large surface area, large pore volume and adequate hydroxyl groups, they have been used to store molecular hydrogen, in catalytic conversions and processing of hydrocarbons, in the removal of environmental hazardous species and in the field of diuretic drug delivery |9] . Some HNT composite materials have found application as electrocatalysts (10|. As the sorbents, HNTs have been tested for the ability to remove cationic dyes and Cr (VI) [ 11 ]. Recentiy, HNTs have been used as a new type of filler for polymers, such as epoxy, polypropylene and polyvinyl alcohol to improve the mechanical and thermal properties of the composites [12,13J. Also, the capric acid-HNT composites are used to prepare phase change materials for thermal energy storage 114].

In recent years, halloysite particles have been investigated as an alternative type of additive for polymers. Halloysite particles are readily obtainable and are much cheaper than other nanoparticles such as CNTs. More importantly, the unique crystal structure of hal­loysite nanotubes resembles that of CNTs, and therefore halloysite

Please rite this article in press as: S. Ranganatha, et aL, Development of high performance electroless Ni-P-HNT composite coatings, Appl. Surf. Sci. (2012), http://dx.doi.0rg/lO.lOI6/j.apsusc.2Oi2.O9.020

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Electrochemical studies on Zn/nano-Ce02 electrodeposited composite coatings S. Ranganatha ^ T.V. Venkatesha ^•*, K. Vathsala ^, M.K. Punith kumar ^ ' Department of Studies in Chemistry, School of Chemical Sciences. Kuvempu University, Shankarttghatta-57745t, Shimoga. Kamataka, India ^ Nana Tribology Laboratory, Mechanical Engineering Department. Indian Institute of Science. Bangalore. 570012. Kamataka. India

A R T I C L E I N F O

Article history-Received 29 December 2011 Accepted in revised form 3 August 2012 Available online xxxx

Keywords: Electrodeposition Composite coating Zeta potential Zn-CeOi Surface morphology Corrosion

A B S T R A C T

The Zn-Ce02 composite coatings through electrodeposition technique were successfully fabricated on mild steel substrate. As a comparison pure zinc coating was also prepared. The concentration of Ce02 nanoparticles was varied in the electrolytic bath and the composites were electrodeposited both in the presence and absence of cetyltriammonium bromide (CTAB). The performance of the Ce02 nanoparticles towards the deposition, crystal structure, texture, surface morphology and electrochemical corrosion behavior was studied. For characterizations of the electrodeposits, the techniques such as X-ray diffraaion (XRD), scanning electron microscopy (SEM) were used. Both the additives ceria and surfactant polarize the reduction processes and thus influence the deposition process, surface nature and the electrochemical properties. The electrochemical experiments like potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) studies carried out in 3.5 wt.% NaCl solution explicit higher corrosion resistance by CeOj incorporated coating in the presence of surfactant.

® 2012 Elsevier B.V. All rights reserved.

1. Introduction

Electrodeposition of zinc is a widely used industrial process to coat on steel materials to enhance its service life. Zinc, being more active than iron, proterts sacrificially by forming white rust. This white rust can be controlled by chromating the surface of zinc using chromic acid. But the effluent of this is hazardous to the environment and chromating process is avoided. To overcome this limitation some organic molecules were introduced as chelating agents and generated their thin fi/m on zinc matrix with the idea of hindering interaction of corrosive medium and metal matrix [1 ].

Increasing and demanding technological applications have led to the development of new coatings such as zinc alloy and/or zinc composite coatings. The zinc alloy coatings such as Zn-Ni, Zn-Mg and Zn-Co have been extensively studied (2-41. On the other hand, zinc coatings containing minute amounts of metal oxides, metal carbides, and carbon nanotubes (CNTs) have been produced called composite coatings. The recent investigations on composite zinc coatings revealed their higher corrosion resistance property, with higher wear resistance and micro-hardness [2-4].

In particular, the metal oxide nanoparticles are widely used for the fabrication of composites due to their ease of availability. The metal oxide nanoparticles like ZnO, AI2O3, ZrOj, TiOj, WS2. M0S2, etc., have been used as bath additives to generate composites for various metals

• Corresponding author. Tel.: +91 9448855079; fax: +91 8282 256255. E-mail address: drtmenkatesbi&yahoo.co.uk (T.V. Venlfatesha).

0257-8972/$ - see front matter C 2012 Elsevier B.V. All rights reserved, doi: 10.1016;i.surfcoat.2012.08.004

and alloys [5-8 ]. The cerium compounds possess some better features and found to have applications in different fields. Nano ceria can be used as an antioxidant and also it possesses low thermal conductivity and higher thermal exapansion of coefficient !9). In recent years ceria is used as gas sensors, electrode material for solid oxide fuel cells, oxygen pumps, amperometric oxygen monitors and abrasive for chemical mechanical polishing slurry. Ceria, in glass industry is considered to be the most efficient glass polishing agent. It is very important to note that cerium compounds either as coatings [lO] or as inhibitors [H-14] are known to polarize the cathodic reactions thereby slowing down oxi­dation of the substrate 115.16].

The Ce02 has been used in fabricating composite coatings with nickel metal. Incotporation of CeOj nanoparticles to metal matrix enhanced wear and corrosion resistance and microhardness, and im­proved high temperature oxidation resistance [17-21). The authors reported that the composites of desired properties may be prepared by proper choice of the electrodeposition parameters and the particle concentration in the electrolytes.

The composite coating of zinc with Ce02 was studied via hot dip process by Shibli and Chacko [15) and they reported that the corrosion resistance was improved considerably. In our present study, electrode­position of zinc was carried out and Ce02 nanoparticles were introduced to metal matrix The effect of cetyltrimethylammonium bromide (CT/̂ B), a cationic surfactant on the composite properties was studied. This cationic surfactant is expected to inaease the particle incorporation and affect the corrosion behavior of the composites [1,2]. The coatings' morphology, structure along with electrodeposition process and corro­sion behavior, is studied in detail.

Please cite this article as: S. Ranganatha, et al.. Surf Coat. Technol. (2012), doi:10.1016/j.surfcoat.2012.08.0O4

l O P PUBUSHINO PHYSICA SCRffX*

Phys. Scr. 85 (2012) 035601 (lOpp) doi: 10.1088/0031 -8949/85/03/035601

Studies on the preparation and properties of electroless Ni-W-P alloy coatings and its nano-MoS2 composite S Ranganatha and T V Venkatesha

Department of Studies and Research in Chemistry, School of Chemical Sciences, Kuvempu University, Shankaraghatta 577451 Shimoga, Kamataka, India

E-mail: drtvvenkatesha@yahoo.co.uk

Received 30 October 2011 Accepted for publication 4 January 2012 Published 3 February 2012 Online at stacks.iop.org/PhysScr/85/035601

Abstract The electroless Ni-W-P ternary alloy and its M0S2 composite films were successfully obtained on low-carbon steel by the electroless plating technique. The sodium tungstate concentration in the bath was varied to obtain Ni-W-P deposits containing various W and P contents. Ni-W-P-MoSi composite was obtained with a suitable concentration of sodium tungstate in the plating bath. These deposits were characterized via x-ray diffraction (XRD), scanning electron microscopy and energy dispersive XRD spectroscopy studies. The corrosion behavior was investigated via potentiodynamic polarization and electrochemical impedance spectroscopy studies in a 3.5 wt% NaCl solution. An increase in codeposition of the alloying metal tungsten changed the structure and morphology of the deposits and enhanced the corrosion resistance. Mechanical properties such as microhardness and friction coefficients were evaluated. Ni-W-P deposits with increasing amounts of tungsten metal were found to possess higher friction coefficients. The microhardness was greatly improved with increasing codeposition of tungsten inetal in the alloy. The incorporation of MoS; nanoparticles into Ni-W-P alloy coatings strongly influenced in reducing the corrosion and friction.

PACS numbers: 68.37.Hk, 61.05.cp, 88.07.Bc, 81.65.Kn, 84.37.+q, 88.30.Nn

(Some figures may appear in colour only in the online journal)

1. Introduction

Electroless nickel coating is a widely used surface engineering technique due to its numerous applications such as excellent corrosion and wear resistance, deposit uniformity, solderability, electrocatalytic activity, etc [1-3]. Phosphorus codeposition along with nickel influences most of the properties. Electroless nickel deposits are structure dependent and the structure and surface nature are related to the P content of the coatings [4]. Although electroless binary Ni-P alloys have found extensive applications due to their properties, electroless ternary alloys with alloying metals such as Cu, Zn, Co, Re, Sn, Fe, W, etc have also been developed to further enhance the properties of the binary system such as excellent corrosion resistance, wear resistance, thermal stability, electrical properties and some special physical performances such as magnetic properties, solderability and

polishability, and to meet more rigorous demands they can be tailored to specific applications [5-9]. Furthermore, the overall performance of ternary alloy coatings can be improved by embedding nanomaterials into their matrix [ 10-13].

Tungsten (W), being a refractory metal, cannot be deposited from any aqueous solution. However, tungsten alloys with the iron group transition metals can be readily deposited from an aqueous solution containing the tungsten metal ions. Electroless ternary alloys with elements other than iron, namely Ni-W-P, were first reported by Pearlstein et at [14]. The introduction of W into the electroless Ni-P matrix improves properties such as wear resistance, corrosion resistance, thermal stability and electrical resistance [15-IS]. Even a small amount of W codeposition affects the chemical composition, morphology and roughness of binary Ni-P deposits. This may be because of the unique properties of W such as high hardness, higher melting point, lower coefficient

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Anti-Corrosion Methods and Materials 59/2(2012)69- 75 q Emerald Group Publishing Limited [ISSN 0003-5599] [DOl 10.1108/00035591211210839]

Anti corrosive electroless Ni-P films for mild steel materials

Thimmappa Venkatarangaiah Venkatesha and Sudhakar Ranganatha Department of Chemistry, Kuvempu University, Shakaraghatta, India

Abstract

Purpose - The purpose of this paper is to evaluate the corrosion resistance of the electroless Ni-P coatings in two aggressive media 3.5 wt.% NaCI and Synthetic industrial w/aste water. Also to study the effect of Phosphorous content in the electroless Ni-P deposits on its surface nature, morphology and con'osion resistance.

Design/methodology/approach - The corrosion behavior of electroless Ni-P coatings generated on mild steel coupons from an acidic and an alkaline baths and their anti-corrosion performance of was compared systematically in 3.5 wt.% of NaCI solution and also in synthetic industrial waste water Microstrurture and surface composition of coatings were analyzed using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques, respectively The NI-P coated mild steel specimens were subjected to corrosion and the rate of corrosion was studied by chemical and electrochemical methods. The linear sweep voltammetry, Tafel and electrochemical Impedance spectroscopy were employed to obtain corrosion data. Findings - The electroless Ni-P coatings with higher P content possess homogeneous, uniform and amorphous surface nature and exhibited higher corosion resistance in the aggressive corrosive media chosen. OrigJnalityAralue - This paper provides corrosion behavior of electroless Ni-P coatings in 3.5 wt.% NaCI and syntfietic industrial waste water, and establishes the importance of phosphorous content on nature and properties of the coatings.

Keywords Steels, Coatings, Corrosion resistance. Films (states of matter), Electroless coating, Ni-P, Synthetic industrial waste water, Impedance, Polarization

Paper type Research paper

Introduction

The electroless plating is a chemical reduction process; the coatings obtained are of uniform thickness all over the object. T h e quality of the deposit, namely, physical and mechanical properties is also uniform because the composition of the coating is uniform at all the thicknesses. Recent advances in the electroless nickel system offer extremely bright deposit, which are comparable with electroplated bright nickel, while retaining the advantages of uniformity of thickness, especially for parts of complex geometry (Hari Krishnan et al., 2006). T h e electroless Ni-P coatings performed better against corrosion compared to bulk Ni and even electrodeposited Ni . Ease of passive film formation in the case of Ni-P deposits due to the presence of P alloyed with Ni held responsible for this noble character (Bai et al., 2003). T h e physical and chemical properties of electroless Ni -P deposits are dependent on the composition of the alloy in question. When the p H decreases, the noticeable change in the plating process is a concurrent decrease in the rate of deposition. T h e most dramatic effect of loweringpH is on the composition and concomitantly, the properties of the Ni-P deposit. Moreover, raising or lowering the p H effects on the process itself as well as the resultant deposits. T h e higher p H leads to increased deposition rate and the deposits contain

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Antt-CotT«sion Methods and Materials 59/2 (2012) 69-75 «5 Emerald Group Pubhshing Limited [ISSN OOOJ-55991 (DOI 10.1108/000355912112108391

decreased P content and exhibit poorer adhesion on steel. On the other hand, lower p H results in decreased deposition rate and corresponding deposits possess higher P content and shows improved adhesion on the steel materials and good corrosion resistance property (Gleim Mallory and Juan Hajdu, 1990). So the addition of P to the nickel matrix significantly enhances the corrosion resistance property in various corrosive environments (Bai et al, 2003). T h e P content can be mosdy controlled by p H of the plating bath (Glenn Mallory and Juan Hajdu, 1990; Ashassi-Sorkhabi and Rafizadeh, 2004). Fur thermore, the significant increase in anti-corrosion behavior can be observed with decreasing the p H there by enhanced P content in the deposit (Ashassi-Sorkhabi and Rafizadeh, 2004; Petukhov et a/., 2004). T h e superior corrosion resistance of high P amorphous deposi ts is a t t r ibutable to the extreme homogeneity, absence of defects and corrosion paths such as grain boundaries, as crystalline materials do (Changdong et al., 2005; Krolikowski etoL, 2006; Ping-Ho etal., 1994).

Due to unique properties of electroless Ni-P deposits, such as wear resistance, paramagnetic characteristics, hardness and electrocatalytic activities, these materials have attracted much attention of the researchers. T h e anticorrosive behavior of these deposits found greater importance and applicabiHty (Bai et al., 2003). T h e electroless Ni-P coatings are well knovra for high corrosion resistance in d e m a n d i n g , aggressive media (Krohkowski et al., 2006). T h e present work aims to produce electroless Ni -P deposits over steel specimens with varying amount of P content and to evaluate their microstructure, surface morphology and corrosion resistance behavior in two different aggressive environments like neutral 3.5 wt.% NaCI and in synthetic industrial waste water (SIWW).

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