Inhibition of the oxygen evolution reaction during titanium passivation in aqueous phosphoric acid solution
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The anodic oxide on titanium can be thickened by anodization, with the consequent corrosion properties of this oxide depending on many variables, including the electrochemical perturbation, the final growth potential, and the nature of the electrolyte. During this anodization, an oxygen evolution reaction (OER) is frequently observed, contributing to reduction of the current efficiency of anodic oxide formation. Based on these factors, evaluation was made of the effect of the electrolyte on oxide film formation and inhibition of the OER during Ti anodization in aqueous H3PO4 and H2SO4 solutions with pH 1. The oxide films were grown by voltammetry and were characterized by electrochemical impedance spectroscopy (EIS) and the Mott-Schottky method. Interpretation of the electrochemical results indicated that inhibition of the OER was due to the adsorption of PO43− ions and their incorporation during growth of the oxide film. The EIS results showed that the oxide films formed in H3PO4 solution were also the most corrosion resistant.
KeywordsAnodic oxide Oxygen evolution reaction Impedance Mott-Schottky Electrolyte incorporation
The authors would like to thank the Brazilian funding agency CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for the financial support.
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