Abstract
The chemistry of chromium in the passive film on sputter‐deposited chromium and 
thin films has been investigatedin situ in an electrochemical cell under potential control by studying x‐ray absorption near edge structure. At high potentials, Cr in the 
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).