In Situ XANES Detection of Cr(VI) in the Passive Film on Fe‐26Cr

The passive film on sputter deposited thin film Fe-26Cr electrodes has been examined using the technique of in situ X-ray absorption near edge spectroscopy (XANES). During the X-ray spectroscopic measurements, the sample was maintained under electrochemical control in the pH 8.4 borate buffer electrolyte. The appearance of the distinctive Cr(VI) XANES pre-edge peak can be correlated with the transpassive wave in the cyclic voltammogram, and its disappearance with the corresponding reduction wave. The formation and reduction of Cr(VI) was reversible, and only small amounts were detected in the film. Cr(VI) in the passive film is not indefinitely stable, and it is completely absent after long periods of air exposure.