Characterization and Corrosion Resistance Behavior Study of Pure Ni Coatings and Ni–V₂O₅ Nanocomposite Coatings Developed by Direct Current and Pulse Current Methods of Electrodeposition

Abstract—Pure nickel (Ni) coatings and nickel–vanadium pentoxide (Ni–V₂O₅) nanocomposite coatings have been developed on the mild steel substrates by the direct current (DC) and pulse current (PC) methods of electrodeposition using a sulfamate electrolyte bath by optimizing all of the suitable parameters. The surface morphology and texture characterization of pure Ni coatings and Ni–V₂O₅ nanocomposite coatings were analyzed by spectroscopic techniques such as scanning electron microscopy (SEM) equipped with an attachment for energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) spectroscopy analyses. The SEM study confirmed surface morphology of the pure Ni coating was changed by the incorporation of V₂O₅ nanoparticles in the nickel metal matrix and chemical composition of all the coatings was determined by EDS. The XRD study proved highly corrosion resistant nanocomposites show preferred orientation towards (111) plane. The corrosion rate of all the coatings was investigated in a 3.5% corrosive medium using electrochemical techniques such as Tafel extrapolation and AC impedance. The coatings developed by PC showed an enhanced corrosion resistance behavior compared to that of the coatings developed by DC. The 0.125 g/L Ni–V₂O₅ nanocomposite coating obtained by PC showed more widened semicircles with a high R_p value and a more positive shift with high corrosion resistance during the AC impedance and Tafel extrapolation analyses respectively. The coatings developed by PC showed improved microhardness compare to that of the coatings developed by DC during microhardness testing of all studied coatings.