Alumina films have been successfully formed on austenitic stainless steels containing 4 and 5 wt % Al by selective oxidation of Al in a H2O/H2 environment. γ-alumina films have been formed by oxidation at 800 °C and δ-alumina films at 900 °C. Satisfactory corrosion resistance performance for ozone gas has been obtained for both γ- and δ-alumina films. For ozonized water, δ-alumina films formed with pH2O/pH2≤1×10-4 have good corrosion resistance while δ-alumina films formed with pH2O/pH2≥3×10-4 or γ-alumina films do not. Holes of a characteristic triangular shape are observed on the oxidized surface of stainless steels containing 4 wt % Al, probably caused by the habitual formation of precipitated β-(Fe,Ni)Al. No such hole has been observed on the oxidized surface of stainless steels containing 5 wt % Al. © 1999 American Vacuum Society.