High Resolution In Situ XANES Investigation of the Nature of the Passive Film on Iron in a pH 8.4 Borate Buffer

The nature of the passive film grown on iron in a pH 8.4 borate buffer at a high potential [+0.4 V (MSE)] was investigated with high resolution in situ XANES (x‐ray absorption near‐edge spectroscopy). The pre‐edge peak at the base of the Fe K edge showed no evidence of the splitting associated with structures such as , , and which contain iron that is entirely octahedrally coordinated to oxygen. The single pre‐edge peak is consistent with the proposed structure (in which one‐third of the iron ions are tetrahedrally coordinated) or with a disordered structure with distorted coordination polyhedra.