Faculty Publications
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Item Effect of pH on Electrodeposition of Ni–Cd Alloy Coatings and Their Anticorrosion Performance(Springer Nature, 2022) Gonsalves, C.N.; Sneha, I.M.; Hegde, A.C.Electroplating is a complex process controlled by bath composition and operating parameters. Among many operating parameters, the pH of the bath plays an important role in the process of deposition and properties of coatings. The present paper reports the effect of pH in the electrodeposition process of Ni–Cd alloy coatings from a low concentration bath of Ni–Cd alloy, using glycine as an additive. The experimental results revealed that change of pH over a wide range (from lower acidic to higher basic conditions) has a significant effect on the structure, morphology, and composition of the alloy electrodeposits. A considerable increase in the uniformity of coatings was found with an increase in bath pH. Electrochemical corrosion study carried out in 3.5% NaCl medium demonstrated higher corrosion resistance for Ni–Cd alloy coating, deposited at pH 8.0 compared to those deposited at lower pH. A change in the process of electro-crystallization was found with the change of pH, confirmed by the scanning electron microscopy (SEM) study. The improved corrosion resistance of alloy coatings was ascribed to the change of codeposition from anomalous to normal type, known by its Ni content confirmed by the energy dispersive X-ray spectroscopy analysis (EDAX). A change in phase structure was found with the change of pH, confirmed by the X-ray Diffraction (XRD) technique. Experimental results are analyzed in light of the theory of alloy deposition, and results are discussed. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Electrodeposited Metallic/ Nanocomposite Coatings(CRC Press, 2023) Elias, L.; Hegde, A.C.Magnesium (Mg) alloys have emerged as the lightest structural material with attractive mechanical properties in combination with other characteristics of good biocompatibility, easy recyclability, large hydrogen storage capacity, high theoretical specific capacity, etc. The ever-increasing trend in the number of publications on Mg and Mg alloys in the past two decades indicates that the research interest on Mg alloys is attaining more and more attention. However, the inferior corrosion resistance is still persisting as a major bottleneck towards their wide practical application. Although there are different strategies to improve the corrosion resistance of Mg alloys, surface coatings attract a lot of attention, since the coatings improve corrosion resistance along with enhancement of other characteristics such as wear resistance, antibacterial activity, hydrophobicity, decorative appeal, etc. Among the various methods available for the development of surface coatings, electrode position is known to be a simple and efficient method for the deposition of coatings at ambient temperature with tuned characteristics and great degree of reproducibility. The chapter presents a concise discussion on the different types of electrodeposited coatings for their corrosion protection. © 2024 selection and editorial matter, Viswanathan S. Saji.Item Multilayer Zn-Ni-Al2O3 coatings for corrosion protection(Inderscience Publishers, 2014) Ullal, Y.; Hegde, A.C.The paper reports the development of composite coatings of Zn-Ni-Al2O3 by composition modulated multilayer (CMM) technique using m-aminophenol and gelatin as additives. The bath constituents and deposition parameters were optimised by conventional method. The role of gelatin and m-aminophenol in the bath was analysed by cyclic voltammetry (CV) study. Corrosion performance of the monolayer coatings was enhanced further by multilayer technique. The modulation in composition was effected by pulsing the DC in square-wave patterns. The coatings configurations were optimised for peak performance of the coatings against corrosion. It was found that corrosion resistance of CMM coatings increased with number of layers up to certain optimal numbers, and then decreased. Incorporation of Al2O3 particles into metal matrix was confirmed by EDAX. Formation of layered coating and their phase structures were analysed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) study. Reasons responsible for better corrosion resistance of CMM composite coatings are analysed and results are discussed. Copyright © 2014 Inderscience Enterprises Ltd.Item Electrodeposition and electrocatalytic study of Ni-W alloy coating(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Elias, L.; Hegde, A.C.Electrocatalytically active Ni-W alloy coatings have been developed through compositionally versatile electrodeposition method on copper substrate from tri-sodium citrate bath, using glycerol as the additive. The deposition conditions have been optimized for peak performance of their electrocatalytic behavior, like hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1M KOH. Corrosion behaviors of the coatings have also been tested under study conditions of electrocatalysis. Electrocatalytic behaviors were tested by cyclic voltammetry (CV) and chronopotentiometry techniques. Experimental results demonstrated that Ni-W alloy coatings, deposited at low and high current densities (c. d.) were showing superior performance for OER and HER, respectively. Better electrocatalytic activity for HER with increase of deposition c. d. was attributed by the unique phase structure, surface morphology and chemical composition of the coatings, confirmed by XRD, SEM and EDX analysis. The dependency of coating thickness and hardness on HER and OER were analyzed, and results are discussed. © (2015) Trans Tech Publications, Switzerland.Item Electrodeposition of Sn-Ni alloy coatings and their characterization(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Shetty, S.; Hegde, A.C.A new alkaline bath has been proposed for deposition of bright Sn-Ni alloy coatings on mild steel (MS). Depositions were carried out at different current densities (c.d.) and their corrosion behaviors were studied in 5% NaCl solution by electrochemical AC and DC methods. Sn-Ni coating, deposited at low c.d. i.e. at 1.0 A/dm2 was found to be the most corrosion resistant compared to those at other higher c.d., even up to 4.0 A/dm2. This least corrosion rate (CR) is attributed to high wt. % Sn in the deposit. Increase of CR at high c.d. range is due to decrease of wt. % Sn, explained by the observed anomalous type of codeposition, followed by the bath. Regardless of the deposition c.d., the bath developed bright coatings, inherent of Sn-Ni alloy. Experimental results are discussed taking in account of the phase structure, composition and surface morphology of the coatings, evidenced by X-ray diffraction (XRD), Energy Dispersive X-ray (EDX) and Scanning Electron Microscopy (SEM) analysis. © (2015) Trans Tech Publications, Switzerland.Item Electron microscopic study of nodules formed during electrodeposition of copper on aluminium(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Augustin, A.; Bhat, K.; Udupa, K.R.; Hegde, A.C.Copper thin film was deposited on double zincated aluminium using electrodeposition route. To understand the growth behavior of copper nodules, deposition was done by varying coating current density. The topography and cross section of the coating was analyzed by using SEM. The structural details of copper nodules were studied by using TEM. Deposited copper thin film was made up of pomegranate like nodules with size varying from 5 μm to 8 μm, varying as a function of coating current density. At higher current density, the coating was made up of multiple layers of nodules having defects like twins, dislocations and stacking faults. The nodules had fine crystallites of size in the range of 50 nm. © (2015) Trans Tech Publications, Switzerland.Item Electrodeposition of Ni-Mo alloy coatings for water splitting reaction(American Institute of Physics Inc. subs@aip.org, 2018) Shetty, A.R.; Hegde, A.C.The present study reports the development of Ni-Mo alloy coatings for water splitting applications, using a citrate bath the inducing effect of Mo (reluctant metal) on electrodeposition, its relationship with their electrocatalytic efficiency were studied. The alkaline water splitting efficiency of Ni-Mo alloy coatings, for both hydrogen evolution reaction (HER) and oxygen evolution reaction were tested using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. Moreover, the practical utility of these electrode materials were evaluated by measuring the amount of H2 and O2 gas evolved. The variation in electrocatalytic activity with composition, structure, and morphology of the coatings were examined using XRD, SEM, and EDS analyses. The experimental results showed that Ni-Mo alloy coating is the best electrode material for alkaline HER and OER reactions, at lower and higher deposition current densities (c. d.'s) respectively. This behavior is attributed by decreased Mo and increased Ni content of the alloy coating and the number of electroactive centers. © 2018 Author(s).Item Layered coating of Zn-Co alloys on mild steel using triangular current pulses for better corrosion protection(2013) Bhat, S.R.; Bhat, K.; Hegde, A.C.Cyclic multilayer alloy (CMA) coatings of Zn-Co were electrodeposited on to mild steel (MS) from acid sulphate bath having thiamine hydrochloride and citric acid as additives. Depositions were carried out galvanostatically from a single bath containing Zn+2 and Co+2 ions. The triangular current pulses cycling between two cathode current densities were used for gradual change in composition in each layer. CMA coatings were developed under different sets of cathode current densities and number of layers, their corrosion resistances were evaluated by potentiodynamic polarization and Electrochemical Impedance Spectroscopy method, results were compared with that of monolayer Zn-Co alloy coatings. At optimal configuration, CMA coating represented as (Zn-Co)3.0/5.0/300 was found to exhibit ∼11 times better corrosion resistance compared to monolayer, (Zn-Co)4.0, deposited for same length of time from same bath. The formation of layered and corrosion mechanism was analyzed using Scanning Electron Microscopy. The corrosion protection of layered coatings of Zn-Co alloy was attributed to the different phase structure of the alloys in alternate layers, evidenced by XRD analysis. © 2013 Indian Institute of Metals.Item Electrodeposition and characterisation of zinc-nickel alloy(2006) Thangaraj, V.; Hegde, A.C.Electrochemically alloys can be designed to produce different corrosion potentials than their alloying elements. This paper deals with investigations on the development of a stable acid chloride bath of zinc-nickel alloy on mild steel in presence of sulphamic acid as brightener. A suitable bath is reported on the basis of Hull Cell studies. The effect of bath variables and operating parameters were studied and discussed. Plating efficiency and the composition of the alloy were determined. Effects of operating parameters on the deposition characteristics and properties were also reported. The corrosion properties of zinc-nickel alloy plating were studied under different operating conditions of the bath after passivation. It was found that the optimized bath composition gave bright and smooth zinc-nickel alloy plating with high performance against corrosion.Item Electrolytic preparation of cyclic multilayer Zn-Ni alloy coating using switching cathode current densities(2010) Venkatakrishna, K.; Hegde, A.C.Cyclic multilayer alloy (CMA) coating of Zn-Ni was developed on mild steel using single bath technique, by proper manipulation of cathode current densities. The thickness and composition of the individual layers were altered precisely and conveniently by cyclic modulation of cathode current densities. Multilayer coatings, having sharp change in compositions were developed using square current pulses. Gelatin and sulphanilic acid (SA) acid were used as additives. Laminar deposits with different configurations were produced, and their corrosion behaviors were studied, in 5% NaCl solution by electrochemical methods. It was observed that the corrosion resistance of CMA coating increased progressively with number of layers (up to certain optimal numbers) and then decreased. Cyclic voltammetry study demonstrated the role of gelatin and SA in multilayer coating. The coating configuration has been optimized for the peak performance against corrosion. The substantial decrease of corrosion rate, in the case of multilayer coatings was attributed to the changed intrinsic electric properties, evidenced by Electrochemical Impedance Spectroscopy (EIS) study. The surface morphology and its roughness were examined by Atomic Force Microscopy (AFM). The surface and cross-sectional view of coatings were examined, using Scanning Electron Microscopy (SEM). X-ray photoelectron spectrum (XPS) study was carried out for surface analysis. The relative performance of pure Zn, monolithic and CMA coatings were compared and discussed. © 2010 Springer Science+Business Media B.V.