Early stages of oxidation of metallic iron in carbon dioxide

Abstract

The early stages of the oxidation of iron metal in carbon dioxide at atmospheric pressure and 773 K have been studied by use of Auger electron spectroscopy. Initially an oxide film is produced which consists of Fe₃O₄ with non-stoichiometric excess amounts of oxygen at the surface. It would appear that a layer of Fe₂O₃ is formed after ∼ 1000 min, but Fe₃O₄ may merely become enriched in oxygen at the expense of sulphur in order to maintain the anion balance in the lattice. Whether or not a change in oxide occurs the change in sulphur and oxygen concentration is produced either by the separation of the oxide and metal at the oxide/metal interface or by the exhaustive diffusion and oxidation of the sulphur from the bulk metal. Sulphur at the surface of the oxide may playa role in ‘fixing’ carbon produced by the decomposition of carbon dioxide.