The Nature of Iron Sulfides Formed on Steel in an H2 S-O2 Environment

Corrosion products initially formed in a wet H2S environment with varying oxygen concentrations were consistently found to be FeS (Mackinawite). After exposure to the atmosphere, these products oxidized to FeO(OH) (Lepidocrocite) and elemental sulfur. Upon further exposure, the FeO(OH) transformed to Fe3O4 (magnetite). Both the corrosion rate in the H2S-O2 solution and the oxidation rate in the atmosphere varied with the degree of crystallization of the corrosion product. The corrosion rate was found to increase with increasing oxygen concentration as expected.