Parametric Study of CO2 Corrosion of Carbon Steel

Abstract Carbon dioxide corrosion of carbon steel has been studied as a function of CO2 partial pressure (0.05 to 2.1 MPa), temperature (20, 40 60 and 90 °C), pH (4 to 6) and flow velocity (0.1, 3.1, 8.5, and 13 m/s) under conditions where protective iron carbonate films do not form. The experiments were carried out under strict control of the water chemistry in a high pressure corrosion testing loop. The corrosion rate was generally high and increased with increasing CO2 partial pressure to an exponent of 0.7. Under conditions with significant flow, high, uniform, corrosion rates only were observed. Localised attacked was occasionally seen at flowrates less than 0.1 m/s. A reduction in corrosion rate was observed when the pH was increased. This is attributed to the significant contribution of the hydrogen ion reduction reaction at low pH and precipitation of iron carbonate when pH exceeds about pH 5. The corrosion rate increased with flow at high temperatures but was less affected by flow at low temperature. At 20 °C a negative flow exponent was obtained at flowrate 3.1 m/s and above.