Comparison of corrosion behaviour for X-65 carbon steel in supercritical CO2-saturated water and water-saturated/unsaturated supercritical CO2

• Comparison of corrosion behaviour in CO2-saturated water and water-containing SC-CO2.
• Main corrosion product of X65 steel is FeCO3 for all three conditions.
• At water contents of 1600 ppm and below, no corrosion was observed.
• Localised attack in the water-saturated SC-CO2 system is a fundamental consideration.
• The mass loss measurements can be misleading in determining the threat posed to CO2 pipeline.

The corrosion behaviour of X65 carbon steel was evaluated in supercritical carbon dioxide (SC-CO2)-saturated water, water-saturated SC-CO2 and under-saturated SC-CO2 conditions at 80 bar and 50 °C to simulate conditions of CO2 transportation in carbon capture and storage applications. A detailed assessment of localised corrosion and corrosion product film morphology/chemistry was conducted. Localised corrosion is shown to be a fundamental consideration in all environments, particularly in water-containing CO2 systems. Corrosion was shown to occur when under-saturated water was present in the system, however, no dissolution of the steel was observed at water contents below 1600 ppm at the conditions considered.

(a) 3D Profilometry image (after cleaning) and (b) 2D surface trace of corroded X65 sample exposed to supercritical CO2-saturated water at 50 °C and 80 bar for 48 h.Figure optionsDownload as PowerPoint slide