Effect of pressure on corrosion behavior of X60, X65, X70, and X80 carbon steels in water-unsaturated supercritical CO₂ environments

A systematic study was performed to investigate the effect of pressure and water content on the general corrosion and localized attack of carbon steels during the transport of CO₂ for the CCS industry. Corrosion experiments were conducted on X60, X65, X70, and X80 carbon steels in water-unsaturated supercritical CO₂ with SO₂ and O₂ in conditions of 50 °C and 8-12 MPa. The general corrosion rates increased with water content and ranged from 0.02 mm/year to 0.31 mm/year at 8 MPa and from 0.01 mm/year to 0.94 mm/year at 10 MPa. Localized corrosion was determined by measuring the penetration rate and pitting factor. The penetration rates ranged from 0.2 mm/year to 3.25 mm/year at 8 MPa and from 0.04 mm/year to 6.02 mm/year at 10 MPa. Meanwhile, the pitting factors ranged from 4 to 70 at 8 MPa and from 3 to 43 at 10 MPa, with water contents varying from 1600 ppm to 3000 ppm. The degrees of general corrosion and localized attack were higher at 8 MPa than those at 10 MPa, with water contents ranging from 1600 ppm to 2600 ppm, but lower at a water content of 3000 ppm.