Corrosion Behavior of X70 Mild Steel during Transportation of Gaseous- and Supercritical-CO2 Fluids

The corrosion behavior of X70 mild steel was investigated in the case of water deposited in CO2 pipeline by means of weight loss method and scanning electron microscopy (SEM). Results showed that general corrosion rate of X70 steel decreased with the increase of CO2 pressure from 4 to 12 MPa at 35 ℃. FeCO3 film and severe general corrosion was observed at 4 MPa, while thin and discontinuous corrosion product and serious pitting corrosion attack were found under other CO2 pressure conditions. It is of great corrosion risk to transport CO2 in gaseous or supercritical sta- tus for X70 mild steel if free water is formed in the pipeline.