Steady-state polarization curves, X-ray photoelectron spectroscopy, and impedance spectroscopy were used to explore the electrochemical properties for carbon steel in alkaline electrolytes. The complex-capacitance representation allowed determination of a capacitance value at high frequency, from which the oxide film thickness could be estimated. These results are in good agreement with values obtained using the power-law model, providing a single mathematical model that is shown to apply in both the anodic and cathodic domains for the characterization of an oxide layer. (C) 2017 Elsevier Ltd. All rights reserved.