It is well known that oxygen reduction is one of the most important reactions in corrosion process. Therefore, oxygen reduction has been extensively studied on metals and alloys, the surface of which is covered with oxide film. In general, the oxygen reduction reaction during localized corrosion is considered to occur extremely fast, but such rapid cathodic process has not been reported. In the present work, we propose an approach to investigate rapid oxygen reduction reaction, so-called a fast current-controlled polarization, where a fast cathodic current transient is applied to metals and alloys covered with oxide film and from the resulting potential variation, the kinetics of the oxygen reduction on the surface is analyzed.

Materials examined were several valve metals such ad Ti, Al, and Zr. Anodic oxide films were produced by anodization on the metals in a phosphate buffer solution at various voltages. In the first current-controlled polarization, a triangle form of cathodic current was applied to the anodized metals, monitoring the resulting potential variation. The potential for all the anodized metals shifted in the less noble direction steeply and then recovered back gradually to the original potential. The potential variation was analyzed based on the assumption that the applied current was consumed as charge-discharge in the space charge layer in the oxide film and the oxygen reduction reaction. As a result, it was found that the oxygen reduction current was clearly different depending on the type of valve metal as well as anodization voltage. In this presentation, details on the fast current controlled polarization will be presented and the different reduction kinetics will be discussed.