CO2 sequestration requires the prediction of pressure-temperature-composition (P-T-X) data for CO2 and water mixtures at significantly high pressures and temperatures and these applications most commonly deal with subsurface water containing dissolved salts. In this study, a thermodynamic model was used to predict the solubility of supercritical CO2 in pure water and in the presence of chloride salts in the aqueous phase (i.e. brine solutions) for temperatures up to 1000C and pressures up to 60 MPa. The concentrations of the corrosion species in the aqueous phase was predicted and were compared with experimental data available from open literature. A mechanistic model is presented to predict the internal corrosion of carbon steel under such operating conditions of temperature, pressure and salt concentrations.