The electrochemical impedance of anodically grown passive films on glassy metal Fe80B20 in berate buffered solutions, was measured in the range between +0.50 V vs. see, the potential of surface film formation, and + 1.10 V, which is deep in the range of the oxygen evolution reaction (OER). By modelling, numerical fitting, and validation procedure, equivalent circuits in particular ranges of potentials were established. The values of elements of these were determined and their potential dependence analysed. Results of both the experimental and modelling procedures show that : (i) at passive potentials, between +0.50 and +0.70 V, the electrode impedance exhibits pure capacitative behaviour due to the non-separable film, and Helmholtz double-layer capacitance, with a low ion transfer anodic current density, i(a); (ii) at E greater than or equal to +0.75 V, the pure capacitance model is complemented by surface (adsorbed) state impedance; (iii) at potentials between +0.95 and + 1.05 V the impedance data and a steep increase in i(a) point towards two-step kinetics of the OER, in which surface (adsorbed) states mediate electron transfer. Comparison of impedance data for Fe80B20 with those obtained for Fe indicates a lower rate constant for the formation of surface (adsorbed) states, a different control step and a lower electrocatalytic efficiency for the OER on Fe80B20.