In situ XANES study of galvanostatic reduction of the passive film on iron

In situ XANES (X-ray absorption near-edge structure) was used to study galvanostatic reduction of the passive film on iron. In a borate buffer, the film appears to be removed in a layer-by-layer fashion by reductive dissolution during the first potential arrest. A burst of dissolution takes place at the end of the arrest for slow reduction rates. During the course of reduction, the remaining film shows a composition change from ferric oxide toward Fe{sub 3}O{sub 4}. This may indicate that the film has an inner layer of Fe{sub 3}O{sub 4}. Galvanostatic reduction of the passive film grown on iron in 0.1M KOH leads to complete reduction of the passive film to ferrous oxide or hydroxide without any detectable dissolution.