Electrochemical & optical characterisation of passive films on stainless steels

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.

[1]  W. Bowers,et al.  In Situ Raman Spectroscopic Investigation of Stainless Steel Hydrothermal Corrosion , 2002 .

[2]  K. Nakamoto,et al.  The handbook of infrared and Raman spectra of inorganic compounds and organic salts , 1997 .

[3]  Carmelo Sunseri,et al.  Semiempirical Correlation between Optical Band Gap Values of Oxides and the Difference of Electronegativity of the Elements. Its Importance for a Quantitative Use of Photocurrent Spectroscopy in Corrosion Studies , 1997 .

[4]  H. Girault,et al.  A Time Resolved Laser Induced Fluorescence Study of Photoinduced Electron Transfer at the Water/1,2-Dichloroethane Interface , 1997 .

[5]  M. Grimsditch,et al.  Transient oxidation in Fe-Cr-Ni alloys: A Raman-scattering study , 1996 .

[6]  Marystela Ferreira,et al.  Electrochemical and Laser Raman Spectroscopy Studies of Stainless Steel in 0.15M NaCl Solution , 1992 .

[7]  S. Joiret,et al.  Influence of Ni, Mo, and Cr on Pitting Corrosionof Steels Studied by Raman Spectroscopy , 1992 .

[8]  A. H. Goff,et al.  Localized corrosion processes in iron and steels studied by in situ Raman spectroscopy , 1992 .

[9]  T. Devine,et al.  Obtaining Surface‐Enhanced Raman Spectra from the Passive Film on Iron , 1991 .

[10]  K. Mccarty,et al.  A Raman study of the systems Fe3−xCrxO4 and Fe2−xCrxO3 , 1989 .

[11]  I. Thanos.  In situ Raman and other studies of electrochemically oxidized iron and iron-9% chromium alloy , 1986 .

[12]  N. Mott,et al.  Electronic Processes In Non-Crystalline Materials , 1940 .