AC Impedance study of passive B2 FeAl intermetallic alloy in sulphuric acid

Impedance properties of passive films grown on a FeAl intermetallic alloy in sulphuric acid solution were investigated as functions of film thickness and electrode potentials in the range 0.5 ⩽ E ⩽ 1.5V. Data analysis of the impedance spectra allowed us to identify two overlapping time constants, which were attributed, respectively, to charge transfer processes at the film/solution interface and ion conduction within the film. The potential dependence of the resistive component of the loop observed in the lower frequency range was discussed in terms of ohmic or high-field contributions to the ion transport within the passive film.