IN-SITU XANES STUDY OF GALVANOSTATIC REDUCTION OF THE PASSIVE FILM ONIRON

In situ XANES (x-ray absorption near-edge structure) was used to study galvanostatic reduction of the passive film on iron. In a berate buff er, the film appears to be removed in a layer-by-layer fashion by redu ctive dissolution during the first potential arrest. A burst of dissol ution takes place at the end of the arrest for slow reduction rates. D uring the course of reduction, the remaining film shows a composition change from ferric oxide toward Fe3O4. This may indicate that the film has an inner layer of Fe3O4. Galvanostatic reduction of the passive f ilm grown on iron in 0.1M KOH leads to complete reduction of the passi ve film to ferrous oxide or hydroxide without any detectable dissoluti on.