AbstractKey principles of alloy oxidation are discussed, with emphasis on Cr2O3and Al2O3formation on nickel-, cobalt, and iron-base alloys. The various special cases of alloy oxidation, which are quantifiable to varying degrees, are presented schematically. The important competition between surface scale development and internal oxidation is emphasized and extended to explain transient oxidation. The ability to measure and model the distribution of alloying elements in steady-state scale and substrate is described. The priority now is to understand further alloying element and defect segregation and transport in grain boundaries, and also other short-circuit paths including pores, in Cr2O3and Al2O3scales.Interaction between alloy depletion, void formation, and phase-boundary oxidant transport in single- and multi-phase alloy substrates requires further elucidation. Brief consideration of ternary and quaternary alloy oxidation illustrates the, ability partially to explain complex alloy behaviour. The role of reactive element additives and dispersoids is reviewed concisely in light of recent work. MST/442