The application of electrochemical impedance spectroscopy and identification procedures to the investigation of the dissolution and passivation of iron in carbonate—bicarbonate buffers at 25°C

Abstract

An electrochemical impedance spectroscopy study of the dissolution and passivation of polycrystalline iron is carbonate—bicarbonate buffers at 25°C is reported. The impedance spectra analysis was performed by using an identification procedure to estimate initially the dynamic parameters from the measured impedance obtained by employing both sinusoidal and pseudo-random binary sequence perturbation, followed by a quantitative fitting on the basis of reaction schemes in terms of formal rate constants. Impedance spectra and steady-state polarization characteristics are accounted for by a reaction model involving the parallel formation of Fe(OH) 2 and soluble Fe(II) species. The concentration of bicarbonate ions determines the overall current in the prepassive potential range.