Electrochemical Behaviour of Thin Oxide Films Formed on Niobium in Aqueous Electrolytes under Open-Circuit Conditions

Abstract

The open-circuit growth of thin oxide films on Nb immersed in aqueous buffer solutions of pH 1–12 has been followed by means of potential and impedance measurements. In the early stages of the oxide film growth, the potential of the Nb electrode was found to decrease by 59 mV per unit pH, while in the final stages the potential decreased by 29 mV per unit pH. Appropriate kinetic equations are suggested. Impedance measurements show that the reaction film influences the corrosion and dissolution of the metal by reason of its effect on the open circuit corrosion potential.