Abstract
Aluminum covered with porous anodic oxide films was re-anodized in 0.5 kmolm-3-H3BO3 and 5×10-5kmolm-3-KOH solutions to examine the formation and breakdown of the oxide film.
In H3BO3-solution, the pores were filled with new oxide during re-anodizing, resulting in the uniform thickening of the barrier layer until film breakdown started. The breakdown potential of the film formed by the “pore-filling” method was 200V higher at maximum than that formed by anodizing after electropolishing.
In KOH solution, the pore-filling with new oxide was accompanied by local dissolution of oxide film, leading to the formation of rough interphase between oxide film and the substrate. The film breakdown potential of the film formed by the “pore-filling” was as high as that the the oxide film formed after electropolishing.
Effects of the structure of porous anodic oxide films on the film breakdown potential during re-anodizing in H3BO3 solution are discussed.
