Corrosion Behavior of P110S Carbon Steel Under High Cl^- High Acid Gas Partial Pressure

The extremely harsh environment of Tahe Oilfield in Northwest China was simulated. The effects of temperature and partial pressure of CO₂ on the corrosion behavior of P110S carbon steel under the condition of high Cl^- containing acid gas were investigated through simulation test in high temperature and high pressure reactor, weight loss method, microstructure observation, phase analysis of corrosion products. The results showed that the corrosion rate of P110S carbon steel first increased, then decreased and then increased with the increase of temperature. With the increase of CO₂ partial pressure, the corrosion rate firstly increased and then decreased. The corrosion rate reached the maximum at 210 ℃ and CO₂ partial pressure of 8 MPa respectively. When the temperature was 150 ℃ or the partial pressure of CO₂ was 8 MPa, FeCO₃ crystal began to precipitate from the solution, forming a protective product film on the surface of P110S carbon steel, effectively inhibiting the overall corrosion of the matrix and reducing the corrosion rate. In addition, the high concentration of Cl^- in the solution could easily lead to the peeling and cracking of the product film, causing serious pitting corrosion.