A theory is developed for the steady-state properties of passive films that form on metals and alloys in aqueous environments. This theory is based on the point defect model developed earlier, and predicts that the steady-state thickness of the barrier film and the log of the steady-state current will vary linearly with applied voltage. These relationships may be used to estimate empirical parameters that describe the dependencies of the potential drop across the barrier film/ environment interface on the applied voltage and pH and to estimate kinetic parameters for dissolution of the film. If dissolution at the film-solution interface occurs very slowly, the primary passive film is envisaged to consist of a rigid oxide sublattice that transmits cations from the metal to a gel-like, precipitated upper layer. If dissolution at the barrier film/ environment interface occurs rapidly, then a steady-state thickness is achieved by a balance between the rate of dissolution of the film at the film-solution interface and the rate of growth of the film into the underlying metal phase, due to the outward movement of oxygen vacancies (i.e., inward movement of oxygen ions) through the barrier layer. The model is

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Algorithms have been developed to apply the Kramers‐Kronig transforms in the analysis of experimental electrochemical impedance data. The application of these algorithms is illustrated by transforming calculated impedance data for an electrical equivalent circuit, by transforming experimental data for TiO2‐normalcoated carbon steel in normalHCl/normalKCl solution at 25°C, and by analyzing data for an aluminum alloy in 4MKOH at 60°C. These transforms, coupled with statistical techniques, provide a powerful means of evaluating the validity of impedance data with respect to spurious errors that are present in either the real or imaginary component, and with respect to system stability.