Corrosion behavior of X65 steel in gaseous and liquid CO₂ transport environments containing multiple impurities and different H₂O content

Abstract

The mechanism of H2O content in different CO2 phase states on the corrosion of pipeline steel was studied by using high-pressure corrosion simulation tests, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and water chemistry simulation calculations. The results show that the corrosion mechanism of X65 steel did not change significantly under different CO2 phase state systems, and the corrosion products were similar. As the H2O content of the system increased, the sulfur-containing products in the corrosion products increased and the degree of corrosion worsened. Additionally, because the aqueous phase formed by the liquid CO2 system contained more corrosive substances, which promote the electrochemical corrosion process of X65 steel, the corrosion degree of X65 steel in a liquid CO2 system was significantly higher than that of X65 steel in a gaseous CO2 system.