Effect of SO₂ concentration as an impurity on carbon steel corrosion under subcritical CO₂ environment

Carbon dioxide (CO₂) is considered to be easier to transport over moderate distances when turned into supercritical state (dense phase) than at any other state. Because of this reason, the transportation of CO₂ during carbon capture and storage requires CO₂ to be at its supercritical state. CO₂ temperature profile from different regions causes CO₂ to deviate between supercritical and subcritical state (gas/liquid phase). In this study the influence of sulphur dioxide (SO2) on the corrosion of carbon steel was evaluated under different SO2 concentrations (0.5, 1.5 and 5%) in combination with subcritical CO₂. Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Energy-Dispersive X-ray Spectroscopy (EDS) were used to characterize the CO₂ corrosion product layer formed on the carbon steel surface. The weight loss results showed that corrosion rate increased with SO₂ concentration with corrosion rate up to 7.45 mm/year while at 0% SO₂ the corrosion rate was 0.067 mm/year.