A Point Defect Model for Anodic Passive Films: III . Impedance Response

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.