Effects of CO2 Phase Change, SO2 Content and Flow on the Corrosion of CO2 Transmission Pipeline Steel

Results from previous studies demonstrated that significant corrosion of carbon steel was observed when 1% SO2 impurity was contained in a supercritical CO2 phase in the presence of small amounts of water (650 ppm). Considering real situations for CO2 transportation pipelines, the effects of CO2 phase change, impurity concentration and flow were evaluated in the present study in order to establish a clearer understanding of the corrosion risk for such pipelines. Different CO2 phases (liquid and supercritical), concentrations of SO2 (< 1%) and flow velocities were used in an autoclave based study. The corrosion rate of steel samples was determined by weight loss measurements. The surface morphology and the composition of the corrosion product layers were analyzed by using surface analytical techniques (SEM, EDS, and IFM). Results showed that the corrosion rate decreased with decreasing SO2 content in the supercritical CO2 phase containing 650 ppm of water. In addition, significant localized corrosion was observed when CO2 phase was liquid.