The Kinetics and Mechanism of Oxidation of Superpurity Aluminum in Dry Oxygen

Abstract

Weight gain data for the oxidation of electropolished aluminum in the temperature range 475° to 600°C are presented and analyzed in terms of the following model. The γ‐alumina crystallites, which nucleate beneath the amorphous oxide film, are assumed to achieve a terminal thickness rapidly, following which only radial growth takes place. This growth proceeds at a constant velocity, until the crystallites impinge on one another. The negative temperature coefficient, observed for the terminal thickness, and the terminal thickness itself follow from the proposed growth mechanism for the crystallites, which is given in sufficient detail to permit comparison of values of the experimental and theoretical pre‐exponential factors. The proposed model is in complete accord with electron micrographic and other data for the system, the kinetic parameters also being in agreement with independent estimates.