IN-SITU MULTIELEMENT XANES STUDY OF FORMATION AND REDUCTION OF THE OXIDE FILM ON STAINLESS-STEEL

The effectiveness of in situ multielement x-ray absorption near edge spectroscopy for studying the passivation of alloys is demonstrated. By simultaneously windowing the appropriate K(alpha) fluorescence lines with a 13-element energy-dispersive germanium detector it is possible to measure concurrently the behavior of different alloying elements during electrochemical polarization. A thin film of stainless steel was stepped between - 1.5 and + 0.4 V (MSE) (the transpassive region of chromium) in a pH 8.4 borate buffer. On the first oxidation, no metal was lost and Fe and Ni showed some oxidation. On reduction, significant Fe and a barely detectable quantity of Ni dissolved. During the second oxidation, some Cr and a smaller fraction of Ni dissolved.