Corrosion performance of iron aluminides in mixed-oxidant environments

Iron aluminide intermetallics are being developed for use as structural materials and/or as cladding for conventional engineering alloys. In addition to their strength advantages, these materials exhibit excellent resistance to corrosion in single-and multi-oxidant environments at elevated temperatures through the formation of slow-growing, adherent alumina scales. Even though these intermetallics develop protective oxide scales in single-oxidant environments, the simultaneous presence of several reactants in the environment (typical of practical systems) can lead to development of oxide scales that are non-protective and undergo breakaway corrosion or to non-oxide scales that are detrimental to the performance of underlying alloy. This paper describes the corrosion performance of Fe–Al intermetallics in environments that contain sulfur, carbon, chlorine, and oxygen and that are typical of industrial applications and power generation systems. Emphasis is on mechanisms of scale development/breakdown, performance envelopes for long-term usage of these materials, approaches to modifying the surfaces of engineering alloys by cladding or coating them with intermetallics, and corrosion experience in practical environments.