The early oxidation (t less than or equal to 120 min) of AISI 430 stainless steel has been investigated by thermal gravimetric analysis and Auger electron spectroscopy. It is found that the oxidation can be divided into two regions : one is a rapid growth rate for t less than or equal to 5 min and the other is a parabolic or slower growth rate for t greater than or equal to 5 min. Through analysis of the components of the oxide film and mathematical modeling, a critical temperature, T-c, above which a chromium-rich oxide film is formed is determined to be 947 K. The corrosion resistance of the oxidized metal is enhanced at T greater than or equal to T-c but is worse at T < T-c. Formation of a protective chromium-rich oxide film on this metal is considered to be a dominant factor in improving corrosion resistance.