By means of vacuum annealing in the range 525–775 K and under well controlled oxidative conditions the chemical composition of protective films of an AISI 316 stainless steel has been modified in order to increase the resistance to crevice corrosion. Independent of surface pretreatment the increase in critical potential for crevice corrosion in a neutral sodium chloride solution after thermal passivation in controlled vacuum is at least 250 mV. Due to selective oxidation of chromium and nickel during such thermal treatments the beneficial effect in corrosion resistance is attributed to a marked chromiumfilm enrichment and a less marked nickelfilm enrichment. In combination with any chemical surface pretreatment, which aims at reducing the amount of certain nonmetallic inclusions where localized corrosion attacks frequently start, this thermal surface treatment will result in a protective film with extraordinarily high corrosion resistance. The vacuum annealing process presented is suggested to act as the finishing manufacturing step in certain applications where the steel article is not subjected to any further high temperature annealing.