Electrochemical & optical characterisation of passive films on stainless steels

• Published in: Journal of physics. Conference series 2006-01, Vol.28 (1), p.74-78
• Main Authors: Sudesh, T L, Wijesinghe, L, Blackwood, D J
• Format: Article
• Language: English
• Subjects: Austenitic stainless steels; Chromium; Electron transport; Iron; Localized corrosion; Optical properties; Photoelectric effect; Physics; Raman spectroscopy; Semiconductivity; Spectrum analysis
• ISSN: 1742-6596; 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/28/1/015

The formation and breakdown of the passive film are mainly controlled by ionic and electronic transport processes; processes that are in turn controlled by the electronic properties of the film. Consequently a comprehensive understanding of mechanisms behind passivity and localised corrosion require a detailed perception of the electronic properties of the passive films together with compositional and structural information. As a step towards this goal the passive film on austenitic stainless steel, AISI 316L, formed in borate solution was characterised by in situ Raman spectroscopy and photocurrent spectroscopy coupled with electrochemical measurements. The composition, structure and semiconductivity of the passive films depended on the potential; Fe rich n-type oxide and a Cr rich p-type oxide dominated at more positive potentials and more negative potentials respectively whilst n-type dual layered film formed at intermediate potentials. Analyses of the bandgap determined for these oxides suggested their structures to be Fe2O3 and a Fe-Cr spinel. This hypothesis was supported by the results of in situ Raman spectroscopy.