Influence of CO2 partial pressure on electrochemical behavior of corrosion-resistant alloys for CO2 injection tubing of carbon capture and storage system

• Corrosion of CRAs compared in scCO₂ and N₂ at high T and low pH. • 13Cr showed active corrosion; S13Cr passive without re-passivation. • DSS and SDSS exhibited high corrosion resistance in both environments. • SDSS was prone to crevice corrosion in scCO2 environment. • Passivity was similar in scCO₂/N₂; repassivation easier in N₂ for high-Cr alloys. Four different corrosion-resistant alloys (13Cr, super 13Cr, 25Cr duplex stainless, 25Cr super duplex stainless steel) were studied under two different CO 2 partial pressures (0 and 13.8 MPa) at high temperature (150 °C) in a 3 wt.% NaCl solution. Electrochemical and exposure experiments were conducted at a consistent initial pH for comparison. The results indicate that 13Cr exhibits active corrosion behavior, whereas super 13Cr demonstrates typical passive behavior without re-passivation under the testing conditions. Both 25Cr duplex and 25Cr super duplex steels show exceptional corrosion resistance and passive behavior, with re-passivation potentials higher than corrosion potential in nearly all testing conditions. Passive films show similar composition and forward-scan responses under both experimental conditions; however, in the CO 2 environment, the alloys repassivated only at more negative potentials than in the CO₂-free condition.