Semiconducting properties of passive films and corrosion layers on weathering steel

摘要

Anodic films were grown on Weathering Steel by potentiostatic polarization in slightly alkaline solution. The photoelectrochemical results reveal that they are n-type iron oxide with E-g = 2.0 eV. Rust layer grown by atmospheric corrosion are n-type semiconductors with a band gap higher than that estimated for the anodic film attributed to the formation of gamma-lepidocrocite. The electrochemical impedance spectra allow to evidence that rust layers have a higher conductivity with respect to anodic films due to the presence of highly doped iron oxide layers. The use of Mott-Schottky theory to model the dependence of oxide capacitance as function of potential is critically discussed. (C) 2020 Elsevier Ltd. All rights reserved.