An Electrometric and Electron Diffraction Study of Air-Formed Oxide Films on Iron

Oxide films formed at room temperature on iron single crystals and poly‐crystals have been investigated by electron diffraction and electrochemical methods. The structure of the oxide is found to vary from an type material at the metal/oxide interface to a type material at the oxide/gas interface. The detailed nature of this film varies with the crystallographic orientation of the iron substrate, the mode of formation, and the time of subsequent air exposure. In all cases examined the oxide forms as a highly oriented, compact array of microcrystals of lateral extension less than 30Aå. The mean thickness of the film lies within the range of 10–25Aå.