Electrofabrication of Ni-Based Alloy Coatings for Better Corrosion Protection and Water Electrolysis

Abstract

This thesis titled, ‗Electrofabrication of Ni-based alloy coatings for better corrosion protection and water electrolysis ‗details a comprehensive approach for improving the corrosion resistance and electrocatalytic activity of (Ni-Co) and (Ni-Mo) alloy coatings through different advanced electrodeposition techniques. Inherent poor properties of alloy coatings, like corrosion resistance and electro catalytic activity of conventional (Ni-Co) and (Ni-Mo) alloy coatings have been improved by taking the advent of artificial convection of mass transport, by inducing ultrasound and magnetic field effect, during electrodeposition. The properties of sonoelectrodeposited (Ni-Co) coatings are improved further by developing them in multilayers, and by pulsing the ultrasound to go ON and OFF periodically, parallel to the process of deposition. The magneto-electrodeposited (Ni-Co) alloy coatings of higher corrosion resistance were developed by superimposing the magnetic field (B), in both intensity and direction (parallel and perpendicular), while depositing. The corrosion resistance property of electrodeposited (ED), sono-electrodeposited(SED), magnetoelectrodeposited (MED) and multilayer alloy coatings were evaluated in 5% NaCl solution through electrochemical AC and DC methods.The experimental investigation on corrosion behavior of all coatings demonstrated that magnetoelectrodeposited (Ni-Mo-Cd) alloy coating, represented as (Ni-Mo-Cd)6.0/0.3T is the most corrosion resistant, compared to other coatings. The electrocatalytic activity of electrodeposited (Ni-Co) and (Ni-Mo) alloy coatings, developed at different current densities (c.d.) were evaluated by alkaline water electrolysis in 1.0 M KOH, using them as both anode and cathode. Electrocatalytic efficacy, in terms of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been studied by measuring quantitatively the amount of H2 and O2 evolved. Effect of addition of nanoparticle into the alloy matrix found to increase the electrocatalytic activity of both (Ni-Co) and (Ni-Mo) alloy coatings, and results are discussed.The electro-catalytic efficacy of electrodeposited alloy coatings, having different configurations demonstrated that (Ni-Mo-CeO2)2.0 Adm-2 and (Ni-Mo) 2.0 Adm-2 coatings are the most active electrode materials for HER and OER, respectively. The electrocatalytic kinetic parameters of HER and OER, corresponding to different alloy/composite coatings were evaluated through cyclic voltammetry (CV) and chronopotentiometry (CP) methods. A mutually opposite electrocatalytic activity of both (Ni-Co) and (Ni-Mo) alloy coatings towards HER and OER, with deposition c.d.‘s was observed. It was attributed to the change in composition of the alloys, in terms of their constituting metals content, in the deposit.The changed property of alloy coatings, both corrosion and electrocatalytic activity was found to have a close relationship with their composition, phase structure, surface morphology and roughness, confirmed by EDX, XRD, SEM and AFM analyses, respectively. The experimental data are compared, and results are discussed with Tables and Figures, and a note for future work is mentioned at the end.