Electrodeposition of Ni-Based Alloy Coatings and Their Electrochemical Behaviours

Abstract

This thesis titled ‘Electrodeposition of Ni-Based alloy coatings and their electrochemical behaviours’ details the experimental results of investigation on electrodeposition and characterization of two newly proposed binary baths of nickel, namely NiW and NiCo for improved corrosion protection and electro-catalytic activity, through different new methods of electroplating. The research work presented here is primarily on optimization of two baths, using glycine as the common additive. Deposition conditions and operating variables have been optimized for best performance of alloy coatings against corrosion, and good electro-catalytic activity of alkaline water electrolysis of HER and OER (1 M KOH). The corrosion resistance and electro-catalytic activities of conventional (monolayer) alloy coatings developed using direct current were improved drastically through different modern methods of electroplating, like composition modulated multilayer (CMM) and magnetoelectrodeposition (MED) methods. Experimental results showed that under optimal conditions, multilayer alloy coatings of both NiW and NiCo show several fold better corrosion resistance, compared to their monolayer counterparts, deposited from same bath for same time. Study of MED alloy coatings revealed that corrosion protection efficacy of monolayer alloy coatings can be increased to many fold of its magnitude by superimposing magnetic field (B), both parallel and perpendicular, applied simultaneously to the process of deposition. At the same time, the electro-catalytic activity NiW and NiCo alloy coatings from their optimal baths, have been tested for their efficacy for both HER and OER during alkaline water electrolysis. The effect of addition of nanoparticles, namely Ag nanoparticles into NiCo bath has been studied for their HER activity. The corrosion resistance and electro-catalytic activity of Ni-based alloy coatings, and their nanocomposite coatings were compared in relation to their composition, surface morphology and phase structure. The process and product of electrodeposition were characterized using CV, CP, SEM, AFM, XRD, EDS and Elemental mapping techniques. The performance of alloy coatings, developed under different conditions have been compared, and discussed with Tables and Figures.