Effect of Water Content on Corrosion Behavior of X65 Pipeline Steel in Supercritical CO2 Fluids
CO2 induced pipeline corrosion is one of main concerns for the safe implementation and large-scale application of Carbon Capture,Utilization and Storage(CCUS)technology.Reasonably limit-ing the water content in supercritical CO2 transport environments containing multiple impurities is crucial for the corrosion control of the pipeline.Herein,the effect of water content on the corrosion behavior of X65 pipeline steel in supercritical CO2 transport environments with/without impurities of O2,H2S,SO2 and NO2 was investigated by means of simulated corrosion test with high-temperature and high-pressured au-toclave,and surface analysis technology.Concurrently,the influence mechanism of impurities on the cor-rosion of the steel in supercritical CO2 transport environments with different water contents was dis-cussed.The results show that X65 steel only undergoes slight corrosion in supercritical CO2-H2O environ-ment even if the water content reaches a saturated solubility of 0.4114％,and the corrosion rate is 0.0013 mm/a.However,when O2,H2S,SO2 and NO2 coexist in supercritical CO2-H2O environment,the corrosion rate of X65 steel increases from 0.0181 mm/a to 0.2901 mm/a as the water content varies from 0.002％to 0.4114％.The impurities and their interactions significantly promote the formation of corrosive aqueous phase,therefore exacerbating the corrosion of X65 steel.The corrosion process of X65 steel in the envi-ronment with low water content is controlled by the products of impurity reactions,whereas the impurities and the products of impurity reactions jointly dominate the corrosion process of the steel in the environ-ment with high water content.
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