The growth of passive films on a series of iron‐nickel‐chromium alloys, , in borate buffer solution was studied ellipsometrically as a function of applied potential and temperature. The kinetic film growth data were found to fit both the logarithmic and inverse logarithmic growth laws with the former providing a more rational representation of the growth behavior. For alloys containing 0, 5, and 10%Cr, the film growth rate constants were found to be essentially independent of applied potential. However, the 16Cr and 30Cr alloys show considerably lower film growth rates at low potentials (< 400 mVSCE), but at higher potentials the growth rates approach those for the low chromium content alloys. The steady‐state film thicknesses were found to vary linearly with potential, and again the two high chromium alloys exhibit anomalous behavior in that the potential dependence changes abruptly at ∼=350 mVSCE. This phenomenon has been interpreted in terms of changes in the composition of the passive film due to dissolution of chromium at high anodic overpotentials.
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