Semiconducting properties of passive films and corrosion layers on weathering steel

• Published in: Electrochimica acta Vol. 354; p. 136697
• Main Authors: Tranchida, G., Franco, F. Di, Megna, B., Santamaria, M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 10.09.2020; Elsevier BV
• Subjects: Anodic polarization; Atmospheric corrosion; Band gap; Carbon steel; Corrosion resistant steels; EIS; Electrode polarization; Iron oxides; Mott–Schottky theory; N-type semiconductors; Semiconductors; Structural steels; Weathering steels; Mott–Schottky theory; Carbon steel; Band gap; Semiconductors; EIS
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2020.136697

•Anodic film on Weathering Steel are n-type semiconductor with band gap of 2 eV.•Rust layers on Weathering Steel were grown by atmospheric corrosion.•Rust layers mainly contain magnetite and lepidocrocite.•Rust layers behave as n-type semiconductor with band gap between 2.3 and 2.6 eV.•Mott-Schottky theory is not suitable to model the measured differential capacitance. 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 Eg = 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 γ-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.