Electrolytic Synthesis and Characterization of Binary Alloy Coatings for Different Applications

Abstract

This thesis titled ‘Electrolytic synthesis and characterization of binary alloy coatings for different applications’ presents a comprehensive study on development and characterization of Ni/Co-based alloy coatings from newly formulated baths, namely Ni-Ti, Co-P and Co-Fe. Standard Hull cell method was used to optimize bath constituents and operating conditions for best performance of alloy coatings against corrosion, and electro-catalytic activity of water electrolysis. The corrosion protection efficacy of monolayer Ni/Co-based alloy coatings were improved further by modern methods of electroplating, namely composition modulated multilayer (CMM) and magneto-electrodeposition (MED) approaches. The attractiveness of electroplating linked to the cathode current density has been explored effectively for the development of multilayer Ni-Ti and Co-Fe alloy coatings for better corrosion resistance, compared to their monolayer counterpart. The multilayer Ni-Ti and Co-Fe alloy coatings of higher corrosion resistance were developed by proper manipulation of cyclic cathode current densities (for change of composition of layers) and duration of current pulse (for change of layers thickness). Corrosion performance of alloy coatings, were studied by electrochemical AC and DC methods in 3.5 % NaCl solution. Poorer corrosion resistance of (Ni-Ti) alloy coatings, inherited by its bath composition was successfully improved by inducing magnetic field (B), parallel to the process of deposition. Effect of both intensity and direction of B (both parallel and perpendicular) were tested. Experimental investigation revealed that corrosion protection efficacy of monolayer Ni-Ti alloy coatings can be increased seven fold better through MED technique. In addition, the electro-catalytic activity of Ni-Ti and Co-P alloy coatings have been tested for their efficacy for water splitting applications in 1.0 M KOH. The effect of addition of Ag-nanoparticles into baths of Ni-Ti and Co-P on electro-catalytic activities of their coatings were studied. The effect of composition, surface morphology and phase structure of alloy coatings on their electro-catalytic efficacies have been studied, using CV and CP methods. The process and product of electrodeposition were characterized using SEM, EDS, AFM and XRD techniques. The performance of different alloy coatings developed for same duration (10 min) through different methods (monolayer, CMM, and MED) were compared, and experimental results are discussed with Tables and Figures.