Electrochemical behaviour of anodic oxide films on antimony in phosphate solutions

Abstract

The dissolution behaviour of the anodic oxide film on antimony in phosphate solutions has been studied by impedance and potential measurements. The dissolution rate of the oxide film was found to increase with increase in the pH of the dissolution medium. A plot of the steady state potential values vs pH gave a straight line with a slope of approximately −55 mV/pH. In phosphate solutions of concentrations up to 1 N, the oxide film is completely dissolved with a rate proportional to the phosphate concentration. But in concentrated phosphate solutions (> 1 N), rapid dissolution followed by formation of an oxide film and/or blocking of the dissolving one was observed and finally complete dissolution occurred. The influence of chloride ions on the rate of dissolution of the oxide film in phosphate solution was found to depend on the solution pH. At pH 2 the dissolution rate increased with increasing the Cl − ion concentration whereas at pH 7 the rate decreased.