Crevice Corrosion of Austenitic Alloys in High-Temperature Water Available to Purchase

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 NiFe₂O_4. 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 crevice. IGSCC was accelerated in crevice by the higher corrosion rate with less protective film at the chromium-depleted phase, with the differential potential cell between the free surface and in-crevice in high-temperature water.