Surface chemistry of carbon steel in contact with CO2 streams containing impurities

Pipeline corrosion is one of the most pressing problems within the push for Carbon Capture and Storage (CCS) hub projects. The corrosion occurs at the interface between carbon steel and the dense CO 2 phase containing reactive impurities. This study investigates diagrammatically the possible corrosion products of iron in contact with a CO 2 stream containing various levels of H 2 O, O 2 , impurities containing sulfur (COS, H 2 S, SO 2 …) or nitrogen (NO, NO 2 ). We construct Pourbaix-like stability diagrams that predict the chemistry of the surface at chemical equilibrium as a function of the composition of the equilibrated stream. Depending on the conditions, a range of possible corrosion products has been identified: FeCO 3 , Fe 2 O 3 , Fe 3 O 4 , FeOOH, FeS, FeS 2 , iron sulfates and nitrates.