Characterization of the film formed on iron in borate solution by electrochemical impedance spectroscopy

The passive film anodically formed on iron in 0.1 mol l(-1) sodium borate solution has been evaluated by electrochemical impedance spectroscopy. An equivalent circuit is assumed in order to characterize the film capacitance, the charge transfer resistance at the interfaces and the ionic flux across the film. The Mott-Schottky representation was used plotting the capacitance as a function of the applied potential. The film can be described as an n-type semiconductor with a high concentration of donors and very low ionic conduction. (C) 2000 Elsevier Science Ltd. All rights reserved.