Abstract
A theory is presented for the anodic oxidation of metals such as tantalum and aluminum. The theory of Mott and Cabrera has been extended to include effects of space charge on kinetics of the process in the highfield case.
The behavior of these systems is shown to depend critically on a dimensionless factor, δ, which is determined by the lattice and energy parameters and also by the experimental conditions.
For δ very small, corresponding to small space charge, the kinetic equation reduces to that of Mott and Cabrera. For large values of δ a very similar equation results which, however, contains only the parameters of the bulk oxide. For intermediate values of δ, complex behavior is predicted. In particular, the temperature independence of Tafel slope observed for tantalum is shown to be a consequence of the theory for certain reasonable choices of the parameters.