Effect of High-Concentration O₂ on Corrosion Behavior of X70 Steel in Water-Containing Supercritical CO₂ with SO₂ Available to Purchase

In the context of carbon capture and storage systems, the pipeline steel utilized to transport supercritical CO₂ usually encounters corrosion if impurities such as O₂ and H₂O are present. This study filled the knowledge gap in understanding the effect of O₂ on carbon steel corrosion behavior in water-saturated and water-unsaturated supercritical CO₂ phase with SO₂ as an acid gas impurity by systematically identifying the general and localized corrosion behavior of X70 steel exposed to supercritical CO₂ with SO₂, varying relative water contents of 45% to 100% and O₂ concentrations of 0.1 mol% to 2.0 mol% at 50°C and 10 MPa. Weight loss method, scanning electron microscopy, x-ray diffraction, and 3D measuring laser microscopy were used to analyze the corrosion behavior. General corrosion rates of X70 steel exposed to 0.1 mol% and 1.0 mol% O₂ increased from 0.03 mm/y to 1.61 mm/y with relative water content rising from 45% to 100%. High O₂ concentrations exerted no influence on uniform corrosion rates at a relative water content of 45%, enhanced the general corrosion at a relative water content of 50% to 60% and localized corrosion at a relative water content of 50% to 88%, but decreased the general corrosion at a relative water content of 75% to 100% and localized corrosion at a relative water content of 100%.