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

In the context of carbon capture and storage systems, the pipeline steel utilized to transport supercritical CO2 usually encounters corrosion if impurities such as O-2 and H2O are present. This study filled the knowledge gap in understanding the effect of O-2 on carbon steel corrosion behavior in watersaturated 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 O-2 concentrations of 0.1 mol% to 2.0 mol% at 50 degrees 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% O-2 increased from 0.03 mm/y to 1.61 mm/y with relative water content rising from 45% to 100%. High O-2 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%.