A model based on the movement of point defects in an electrostatic field is proposed to interpret the growth behavior of a passive film on a metal surface. This model results in a logarithmic growth law. The theoretical equations derived from the model readily account for experimental data for the growth of a passive film on iron. It is found that the field strength of the film is 1.11×106V/normalcm . The dependence of film/solution interface potential difference on the applied potential (α) was found to be 0.743, and is independent of the identity of the anion in solution. However, the dependence of the potential difference across the film/solution interface on the solutionpH (β) is strongly dependent on the identity of the solution anion.

The point defect model that was previously developed (1) to explain the growth kinetics of a passive film has been extended to account for chemical breakdown. This model provides quantitative explanations of the dependence of breakdown potential on halide concentration, and of the incubation time‐breakdown overpotential relationships that have been observed for iron and nickel in aqueous solutions. Limitations of the model are identified and discussed.

The impedance spectrum for a passivated electrode has been computed using the point defect model that was proposed earlier (6, 7). This model predicts that at high frequencies the film/solution interfacial reaction is predominant and thus a variety of semicircles can be observed in the complex impedance plane. At low frequencies, the transport of point defects in the passive film is rate controlling, and a Warburg‐type impedance spectrum is predicted. These predictions are in good agreement with experimental data for passive Ni and Type 304 SS in aqueous buffer systems.

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Measurements have been made on the scattering of 7-rays from Th C" by Al and Pb. For Al the scattering is, within experimental error, that predicted by the Klein Nishina formula. For Pb additional scattered rays were observed. The wavelength and space distribution of these are inconsistent with an extranuclear scatterer, and hence they must have their origin in the nuclei.