Comparative crevice corrosion behaviour of AISI 304, AISI 317, and UNS S2205 stainless steels in chloride environment

Crevice corrosion resistance of stainless steels (SSs) in chloride environments is governed by the coupled effects of alloy chemistry, passive-film stability, and localised corrosion kinetics. This study systematically correlates alloy composition, electrochemical behaviour, passive-film chemistry, and crevice corrosion resistance of AISI 304, AISI 317, and UNS S2205 SSs using potentiodynamic polarisation, ASTM G48 immersion testing, FE-SEM/EDS, optical profilometry, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Localised corrosion resistance increased progressively from AISI 304 to AISI 317 and UNS S2205, with pitting potentials of 0.081, 0.853, and 0.978 VSCE, respectively. AISI 304 exhibited the highest corrosion rate (4.079 ± 0.16 mm/y), and crevice penetration depth (∼2.01 mm), whereas UNS S2205 showed the lowest values (2.798 ± 0.35 mm/y, and ∼0.77 mm). AISI 317 displayed intermediate behaviour owing to Mo-assisted passive-film stabilisation and repassivation. Raman spectroscopy identified Fe oxides and oxyhydroxides as the principal corrosion products, while XPS revealed a compact Cr- and Mo-enriched passive film on UNS S2205, in contrast to the Fe-rich passive films formed on the austenitic grades. The superior corrosion resistance of UNS S2205 is attributed to the synergistic effects of higher Cr, Mo, and N contents which collectively enhance passive-film stability and suppress chloride-induced localised corrosion.