The reaction rates in oxygen of electropolished samples of superpurity aluminum and certain of its binary alloys were investigated in the temperature range 250°–450°C, employing anodic polarization and weight gain measurements. The rate of formation of “amorphous” oxide was not affected by small alloying additions of Fe, Mn, or Ga, and was found to be in good accord with the Cabrera‐Mott theory for the formation of very thin films. A modified version of this theory is preferred, however, since the rate appears to be controlled within the film, rather than at the metal‐oxide interface. At 450°C and presumably above, the nucleation and initial growth of gamma alumina crystallites was found to coincide with a region of approximately constant oxidation rate, providing a qualitative explanation for the latter. The presence of copper was found to have an appreciable effect on the oxidation behavior. This effect can be explained by assuming that the presence of copper ions in the oxide film increases the concentration of conducting aluminum ions substantially.