Effect of Temperature on Corrosion of P110 Steel in Oil Field Environment with High CO₂ and Low H₂S

In order to clarify the influence of temperature on the corrosion rate of P110 steel under high CO₂ and low H₂S conditions, corrosion simulation experiments were carried out and the corrosion rate was recorded by weight loss method. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and laser confocal microscope were used to observe and analyze the corrosion morphology and corrosion products on the surface of P110 steel. The results showed that the general corrosion rate of P110 steel increased and then decreased with the increase of temperature under the condition with CO₂ partial pressure of 1 MPa and H₂S partial pressure of 20 kPa. The corrosion peak temperature was reached near 100 ℃. When the temperature rised above 80 ℃, the corrosion morphology changed from general corrosion to localized corrosion and the corrosion pits could be observed within 80 ℃ to 120 ℃. With the increase of temperature, the corrosion products on the surface of P110 steel changed from iron-rich structure to sulfur-rich structure. Dense troilite and pyrrhotite impeded ion diffusion in the corrosion reaction. The increased of temperature in the range from 60 ℃ to 100 ℃ would promote the reaction of anode and cathode, which would lead to the increase of the current density and corrosion rate of P110 steel. When the temperature continued to rise to 120 ℃, the P110 steel self-corrosion current density would decrease and the corrosion process would be inhibited.