Effect of Impurities on the Corrosion Behavior of Carbon Steel in Supercritical CO2 – Water Environments

The objective of the present study is to evaluate the corrosion properties of carbon steel in supercritical CO₂/H₂O/O₂/SO₂ mixtures related to the transmission of CO₂ to sequestration sites. To understand the thermodynamic properties of supercritical CO₂/H₂O/O₂/SO₂ systems related to the corrosion phenomena, mutual solubilities of CO₂ and water as well as pH of water-rich phase were measured with different pressures, temperatures, and impurities concentrations. The corrosion property of carbon steel was evaluated by using an autoclave with different pressures (max. 2000 psi), temperatures (max. 50^oC), and concentrations of impurities. The concentrations of O₂ and SO₂ were changed from its maximum concentrations in supercritical CO₂ phase (4% for O₂ and 0.1% SO₂). The corrosion rate of 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 Raman). In addition, mitigation strategies for corrosion of CO₂ transport pipeline were suggested by utilizing corrosion inhibitors and corrosion resistant alloys (CRA).