Synthesis and Characterization of Electrodeposited Nickel Based Alloys and Their Nanocomposite Coatings

Abstract

This thesis titled ‘Synthesis and Characterization of Electrodeposited Nickel Based Alloys and Their Nanocomposite Coatings’ is a comprehensive approach for improving the corrosion resistance and electrocatalytic activity of binary alloys, namely Ni-W and Ni-P. New alkaline citrate baths have been optimized for the electrodeposition of Ni-W and Ni-P alloy coatings through standard Hull cell method, using glycerol as a common additive. The effect of bath composition, deposition current density (c. d.), pH and concentration of additive on the coating properties were studied. The corrosion resistance of monolayer alloy coatings were improved to many folds of its magnitude through multilayer approach by depositing in layers, having alternatively different composition. Further, the benefit of magnetoelectrodeposition (MED) has been explored for improving the coating characteristics of Ni-W alloy. The conditions of MED have been optimized for maximizing the corrosion protection efficacy of Ni-W alloy coatings. The effect of magnetic field (B) on coating characteristics, in both intensity and direction have been tested. A significant change in the deposit characters have been observed due to increase in the limiting current density (iL), explained by the magnetohydrodynamic (MHD) effect. The electrocatalytic activity of the alloy coatings towards hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were tested using electrochemical methods. The HER efficiency of the coatings was further enhanced by different methods such as electrochemical dissolution, MED, magnetic field induced HER (MFI-HER), and by nanoparticles incorporation. All depositions were carried out for the same duration (10 min) for comparison purpose. The corrosion resistance and electrocatalytic 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 different analytical techniques, like SEM, XRD, EDS etc. The performance of the coatings have been compared and discussed with Tables and Figures, supported by plausible mechanism.