Abstract Oxide film characterizations and electrochemical measurements were carried out on crevices of austenitic stainless alloys to investigate the acceleration mechanism of intergranular stress corrosion cracking (IGSCC) in high-temperature water. When the chromium concentration was sufficient, type 304 (UNS S30400) stainless steel (SS) and alloy 600 (UNS N06600) exhibited good corrosion performance in crevices, forming a chromium-enriched layer in an oxide film consisting of diiron nickel oxide (NiFe2O4). When chromium was depleted in the crevice, however, the nickel-based alloy exhibited larger weight loss and a thicker film, including nickel oxide (NiO) and NiFe2O4. The crevice environment in high-temperature water was characterized by a lower pH (one unit lower) and a lower corrosion potential (300 mV to 400 mV lower) than in the bulk water environment. There was a notable increase in the coupling anode current from the crevice to the free surface when the chromium-depleted phase was located in the...