Comparative crevice corrosion behavior of 316Ti, 310 austenitic stainless steels and 32750, 32760 super duplex stainless steels in 6% FeCl 3 using ASTM G48

This study evaluates the crevice corrosion behaviour of 316Ti and 310 austenitic stainless steels (ASSs) and 32750 and 32760 super duplex stainless steels (SDSSs) in 6% FeCl3 solution following ASTM G48. A multi-technique approach, including gravimetric analysis, macroscopic examination, field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDX), optical profilometry, and Raman spectroscopy, was employed to assess degradation mechanisms. Results indicate significantly higher susceptibility of ASSs, with corrosion rates of 3.52 ± 0.89 mm/y (316Ti) and 3.44 ± 1.06 mm/y (310). In contrast, SDSSs show markedly lower rates of 0.0045 ± 0.0016 mm/y (32750) and 0.0064 ± 0.0042 mm/y (32760). Profilometry reveals deeper crevice attack and higher roughness in ASSs, whereas SDSSs exhibit minimal surface damage. Raman analysis identifies metastable phases (β-FeOOH, γ-Fe2O3) in ASSs and stable phases (α-Fe2O3, α-FeOOH) in SDSSs. The superior performance of SDSSs, particularly 32750, is attributed to enhanced passive film stability due to Cr–Mo-N-W synergy. These findings confirm the suitability of SDSSs for chloride-rich environments such as marine and chemical processing applications.