Effect of Exposure Time on the Corrosion Rates of X70 Steel in Supercritical CO₂/SO₂/O₂/H₂O Environments

Corrosion of pipeline steel used to transport supercritical carbon dioxide (CO₂) has been given increasing attention among various issues related to carbon capture and storage systems. When impurities are included, such as sulfur dioxide (SO₂) and O₂, the understanding of exposure time on the corrosion rate is inadequate. In the present work, the weight-loss method was used to study the effect of exposure time on the corrosion rates of X70 steel in supercritical CO₂/SO₂/O₂/H₂O. Morphology analysis was conducted on both surface and cross section by scanning electron microscopy (SEM), and the phase analysis of product scales was conducted by x-ray diffraction (XRD). The result showed that the exposure time had a great impact on the corrosion rates of X70 steel in supercritical CO₂/SO₂/O₂/H₂O. As corrosion went on, the product scale thickened, which effectively decelerated the corrosion rate. Finally, this work conducted analysis and discussion on the physical model and reaction process of X70 steel corrosion in such corrosive environments.