Potential modulated ellipsometric measurements on an Fe-17Cr alloy in sulphuric acid

• Published in: Corrosion science Vol. 37; no. 8; pp. 1211 - 1233
• Main Authors: Jacobs, L.C., De Vogel, H.P., Hemmes, K., Wind, M.M., De Wit, J.H.W.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-08-1995; Elsevier Science
• Subjects: Applied sciences; Corrosion; Corrosion environments; Exact sciences and technology; Metals. Metallurgy; Corrosion resistance; Investigation method; Chemical composition; Chromium alloys; Layer thickness; Electrode potential; Iron base alloys; Ellipsometry; Passivation; Sulfuric acid
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/0010-938X(95)00026-G

Ellipsometric measurements on an Fe-17Cr alloy have been performed combined with electrochemical measurements in order to study the passive film as a function of the electrode potential. The ellipsometric parameters Ψ and Δ change with varying potential, due to the formation of a passive film or to changes in the composition and thickness of the film. It is shown that it is possible to determine a range of physically acceptable values for the refractive index of the passive film for thicknesses between 1.5 and 2.5 nm. The values found for the imaginary part — about 2–4 — indicate the semimetallic character of the film. The composition and the thickness of the film in the passive region from −600 to +450 mV (SSE) hardly change. In the transpassive region film growth and considerable change in composition were observed.