X-Ray Absorption Study of Electrochemically Grown Oxide Films on AlCr Sputtered Alloys II. In Situ Studies
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Citation:Frankel, G. S.; Schrott, A. G.; Davenport, A. J.; Isaacs, H. S.; Jahnes, C. V.; Russak, M. A. "X-Ray Absorption Study of Electrochemically Grown Oxide Films on AlCr Sputtered Alloys II. In Situ Studies," Journal of the Electrochemical Society, v. 141, no. 1, 1994, pp. 83-90.
The chemistry of chromium in the passive film on sputter-deposited chromium and AlCr thin films has been investigated in situ in an electrochemical cell under potential control by studying x-ray absorption near edge structure. At high potentials, Cr in the AlCr alloys was oxidized to the 6-valent state. Depending on the rate of potential increase, 6-valent chromium either dissolved from the alloy or was trapped in the passive film where it was electroactive, i.e., the valence state could be reversibly switched between the 3- and 6-valent states by changing the applied potential. The kinetics of these processes were investigated. Ex situ x-ray photoelectron spectroscopy measurements indicated that, during slow scanning at low potentials, the composition of both the surface oxide and underlying metallic layers changed. These changes resulted in a structure that was susceptible to transpassive dissolution of Cr at potentials above 0.2 V(MSE).
A. J. D. and H. S. I were supported under the auspices of the U. S. Department of Energy, Division of Materials Sciences, Office of Basic Energy Science under Contract No. DE-AC02-76CH00016.