Modeling steel corrosion under supercritical CO₂conditions

Corrosion in the presence of CO 2 was studied under supercritical conditions (high pressure and moderate temperature) using different carbon steels and various corrosion resistant alloys (CRA's). An objective of this work was, among others, to put the results in perspective relative to various CO 2 corrosion models that have been developed and published over the years. In particular, the NORSOK, FREECORP, and OLI models were used for comparison, while others were discussed as well. The systems investigated were (a) supercritical CO 2 (SC CO 2 ) saturated with water (no separate water phase), (b) a water mist phase in equilibrium with SC CO 2 , (c) a water/brine phase in equilibrium with SC CO 2 . It was found that the OLI model best simulates the experimental corrosion rates observed in system (c) where coupons were corroded in the aqueous phase at high velocities in the rotating cage. The varying susceptibility of different carbon steels to corrosion under these conditions is highlighted. CRA steels are comparatively more resistant.