Mobility of Metallic Foreign Atoms during the Anodic Oxidation of Aluminum

Abstract

Metallic foreign atoms introduced into the surface layers of aluminum specimens are shown to be mobile during anodic oxidation. The direction of motion depends on whether the initial distribution of the foreign atoms is located in aluminum metal under the natural air‐formed oxide or entirely contained within a thin preformed surface film of anodic oxide. For a number of the fifteen elements studied, the rate of motion relative to aluminum ions was determined. The results of these experiments are of intrinsic interest in the eventual understanding of the processes involved and have immediate practical consequences for sectioning techniques which involve anodizing and stripping.