Oxidation of Cobalt Metal

By means of inert markers of radio-platinum, it has been shown that cobalt metal oxidizes by outward diffusion of cobalt atoms through the oxide. Oxidation rates have been measured at various temperatures and oxygen pressures and have been found to agree with the rates calculated from the Wagner equation and the authors’ values for the diffusion coefficient of cobalt in the oxide. The distribution of radio-cobalt in growing oxide layers has been accurately measured and found to be different from that predicted from the Wagner oxidation theory. Attempts have been made to measure the change of lattice parameter of the oxide with composition.