Effect of oil displacement agent on corrosion behavior of NaCl - Alkali/ Surfactant/ Polymer flooding pipeline steel

The research examined the effect of oil displacement agent (Hydrolyzed polyacrylamide, Sodium petroleum sulfonate, NaCl) on corrosion behavior of 20# steel in simulated NaCl ASP flooding solution. Scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray Photoelectron Spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization were performed to investigate the corrosion mechanism of oil displacement agent on carbon steel. The results demonstrated HPAM (hydrolyzed polyacrylamide) and SPS (sodium petroleum sulfonate) can be adsorbed on the surface of carbon steel to played a role in corrosion inhibition. For-HPAM, the corrosion inhibition rate decreases at high concentrations, which was ascribed to the saturation of adsorption amount and the thinning of corrosion product layer at higher concentrations. For-SPS, the formation of hemi-micellar aggregates caused desorption of the inhibitor from the metal/solution interface at higher concentrations. For -NaCl, NaCl promoted the occurrence of corrosion. Although the adsorption of oxygen on the surface of carbon steel was inhibited by a higher concentration of Cl−, a corrosion cell was formed under the action of the adsorption layer of HPAM and SPS, which promoted localized corrosion.