Corrosion of Carbon Steel in High CO2 Environment: Flow Effect

At first glance, the need to explore and develop hydrocarbon gas fields which contain high CO₂ contents (up to 80 mole %) would call for use of expensive corrosion resistant alloys. This would have the potential to render project development costs untenable. An alternative approach would be to evaluate the technical feasibility of using carbon steels. Unlike transportation and sequestration of supercritical CO₂, where the amount of water is normally negligible or comes from condensation, field development has to consider the presence of formation water. This water has the potential to contain multiple corrosive species. In addition to the action of such species during carbon steel corrosion, evaluations that involve the effect of flow on corrosion rates are required as flow has the possible effects of challenging the protectiveness of the corrosion product films and increasing the mass transfer rates close to the pipe wall. Flow-sensitive CO₂ corrosion has been studied in rotating cylinder electrode (RCE) or pipe flow loop systems. In the present study, the hydrodynamic effects on CO₂ corrosion are evaluated using a high pressure and high temperature rotating cylinder electrode setup. Corrosion rates are measured via weight loss and electrochemical methods at various pH’s (3 to 5), temperatures (25 to 50°C), near critical and supercritical CO₂ partial pressures and at equivalent fluid velocities from 0 to 1.5 m/s.