Electrochemical studies on the electrodeposited Zn-Ni-Co ternary alloy in different media

The electroplating of ternary Zn-Ni-Co alloy, surface morphology and corrosion resistance were investigated and contrasted with the characteristics of Zn-Ni electrodeposits. The investigation of electrodeposition was carried out using cyclic voltammetry and galvanostatic techniques, while potentiodynamic polarization resistance and anodic linear sweeping voltammetry techniques were used for corrosion study. Under the examined conditions, the electrodeposition of the alloy was of anomalous type. It was found that the obtained Zn-Ni-Co alloy exhibited more preferred surface appearance and better corrosion resistance compared to Zn-Ni alloy that electrodeposited at similar conditions. During the cathodic scan of cyclic voltammetry, a cathodic peak at -574 mV is appeared and correlated with the deposition of sulfur liberated from the reduction of sulphate group in the presence of H. Up to four anodic peaks were obtained by cyclic voltammetry technique, two correlated with zinc oxidation from pure deposited Zn and gamma-Ni5Zn21 phases and two correlated with oxidation of cobalt and nickel, were observed. The phase structure, surface morphology and chemical composition of the deposits were characterized by means of X-ray diffraction analysis, scanning electron microscopy and atomic absorption spectroscopy, respectively. (C) 2008 Elsevier B.V. All rights reserved.