Thin alumina films were deposited at low temperatures (290–420°C) on stainless steel, type AISI 304. The deposition process was carried out in nitrogen by metal-organic chemical vapour deposition using aluminum tri-sec-butoxide. The film properties including the protection of the underlying substrate against high temperature corrosion, the chemical composition of the film, the microstructure, and the refractive index were investigated. The activation energy for the heterogeneous reaction was 83 ± 5 kJ mol-1. Corrosion experiments, performed at 450°C in a hydrogen sulphide containing gas, showed that the amount of corrosion products of an alumina film (0.20±0.05 mg cm-2)-AISI 304 combination decreased with increasing deposition temperature. The alumina films, even those deposited at 420°C, exhibited an amorphous structure, in agreement with the index of refraction. Transmission electron microscopy analysis revealed that extremely fine γ-alumina was formed. Only OH groups were found as an impurity in the oxide film. No carbon was detected.