Corrosion Behavior of Carbon Steel in Supercritical CO2 – Water Environments

The corrosion behavior of carbon steel was investigated under supercritical CO₂ (scCO₂) – water systems to simulate the condition of CO₂ transportation pipeline in the CO₂ sequestration applications. To understand the thermodynamic properties of scCO₂-water systems related to the corrosion phenomena, thermodynamic modeling were conducted for the mutual solubilities of CO₂ and water in the two coexisting phases, and for the concentrations of corrosive species in the free water at various ranges of pressure and temperature. Carbon steel samples were exposed to pure scCO₂, water-saturated scCO₂, and scCO₂ saturated water in the pressure range of 70 to 100 bar and temperatures from 25 to 50^oC. The corrosion rate of samples was determined by weight loss measurements in pure scCO₂ and water-saturated scCO₂ environments, whereas it was measured by LPR and weight loss measurements in scCO₂-saturated water environments. The surface morphology and the composition of the corrosion product layers were analyzed by using surface analytical techniques (SEM, EDS, and XRD).