Assessing the corrosion product scale formation characteristics of X80 steel in supercritical CO2-H2O binary systems with flue gas and NaCl impurities relevant to CCUS technology

Abstract

The corrosion product scale formation mechanism of X80 steel in the supercritical (SC) CO2-H2O binary phase containing flue gases and NaCl impurities at 8 MPa and 60 °C was investigated. The formation process of corrosion product scale was significantly different in the SC CO2-saturated aqueous and water-saturated SC CO2 phases. In the SC CO2-saturated aqueous phase, an amorphous product scale was formed initially, then a crystalline product scale was precipitated. The formation process of the corrosion product scale in the saturated-water SC CO2 phase proceeded in just the opposite way. In the water-saturated SC CO2 phase, the inner scale had better protectiveness to the substrate than the outer scale, but it was just the opposite in the SC CO2-saturated aqueous phase. The severity of pitting in the SC CO2-saturated aqueous phase was much greater than the pitting corrosion in the water-saturated SC CO2 phase.