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

Four different corrosion-resistant alloys (13Cr, super 13Cr, 25Cr duplex stainless, 25Cr super duplex stainless steel) were studied under two different CO₂ 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 CO₂ environment, the alloys repassivated only at more negative potentials than in the CO₂-free condition.