The corrosion behavior of ferritic–martensitic 17Cr stainless steel in CO2-saturated brine was investigated using static autoclave immersion tests in 4.12 wt% NaCl solution at 230 °C under CO2 partial pressures of 6.36, 18.28, and 24.57 MPa. The calculated in situ pH values obtained using the OLI System were 3.79, 3.55, and 3.49, respectively. Corrosion morphology, microstructural evolution, and corrosion products were characterized by SEM, EDS, EBSD, and Raman spectroscopy. The average mass-loss corrosion rate increased from 0.138 ± 0.0221 mm/year at 6.36 MPa pCO2 to 0.326 ± 0.0142 mm/year at 24.57 MPa pCO2. Although the specimens did not show severe macroscopic pitting, localized attack preferentially occurred in fine-grained martensitic banded regions. EBSD analysis revealed that these regions exhibited higher local misorientation and defect density, which may reduce the stability of Cr-rich surface films. Raman spectra identified Cr(OH)3 in the corrosion products, and the Cr(OH)3 signal became more evident with increasing CO2 partial pressure. The results indicate that, under fixed temperature and salinity, the corrosion behavior of 17Cr stainless steel is governed by CO2 partial pressure and microstructural heterogeneity.
He et al. (Mon,) studied this question.