Electrodeposition of composites of zinc with vanadium oxide from sulfate solutions

Abstract

Electrodeposition of Zn with V was examined from optionally agitated sulfate solutions containing Zn2+ and VO2+ at pH 0-3 and 40°C under galvanostatic conditions. XPS spectra of the deposits showed that V was present in the deposited Zn in the form of its oxide, formed by hydrolysis of V ions. The V content of the deposits increased with increasing pH of the solution and increasing current density. These conditions appear to accelerate the hydrolysis of V ions by means of an increase in hydrogen evolution in the cathode layer. SEM and EPMA studies of the deposits showed that the V in the deposits was segregated at the edges of layered platelet crystals of Zn. Agitation of the electrolyte decreased the V content of the deposits but reduced the segregation of V oxide. Anodic polarization curves for dissolution of Zn in 3 % NaCI solution were polarized by codeposition of V oxide with Zn for V contents of <5 mass%. The corrosion current densities of deposits obtained from agitated solutions were smaller than those from un-agitated solutions. © 2008 ISIJ.