Corrosion Behavior of 316L Stainless Steel under Different Concentrations of Cl^- and CO₂ Conditions

Abstract

In order to elucidate the impact of Cl- and CO2 on the corrosion behavior of 316L stainless steel in the produced water environment of the Liaohe oilfield, the effects of varying Cl- concentrations and CO2 partial pressures on 316L stainless steel were investigated through immersion tests, electrochemical impedance spectroscopy(EIS) and polarization curve techniques. The Cl- concentration gradients were 0, 0.030 0, 0.051 5, 0.070 0 mol/L, while the CO2 partial pressures were set at 0.2, 0.4, 0.6 MPa. Additionally, X-ray diffraction(XRD) technology was employed to analyze the corrosion products. Results showed that with the increase of Cl- concentration, the diameter of the capacitive reactance arc decreased, the dispersion index decreased, and the corrosion was intensified. With the increase of CO2 partial pressure, the diameter of the capacitive reactance arc first decreased and then increased, the dispersion index first decreased and then increased, and the corrosion first intensified and then slowed down. This was due to the fact that Cl- would destroy the passive film on the surface of 316L, while CO2 would react with the substrate to form FeCO3. With the increase of CO2 partial pressure, the FeCO3 protective film became denser.

Keywords

• 316l stainless steel; produced water of oilfield; cl^-; co₂; corrosion behavior; passive film