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 Kalpha 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.