Synergism of alkylbenzene sulfonate and cetyltrimethylammonium bromide on corrosion inhibition of carbon steel in CO2-saturated solutions

The synergistic effect of mixed surfactants, linear alkylbenzene sulfonate (LAS) and cetyltrimethylammonium bromide (CTAB), in inhibiting corrosion of CO2 on carbon steel was studied by weight loss and electrochemical measurement. The surface properties of LAS, CTAB, and their mixture in solution were also studied by surface tension and phase behavior. The surface of corrosion specimens was characterized by infrared spectroscopy, scanning electron microscopy, contact angle, and atomic force microscopy. The results show that LAS, CTAB, and their mixture are inhibitors mainly inhibiting anode reactions. The adsorption of LAS and CTAB molecules on the surface of steel belongs to chemical adsorption and follows Temkin adsorption. LAS or CTAB alone aggregated form spherical micelles or rod-like micelles, which results in the defective film layer and localized corrosion on surface of the steel. Mixed surfactants form closely packed lamellar microstructure in the solution which is correlated to compact adsorption film on the metal surface and better corrosion inhibition. The inhibition efficiency is the highest when the mixed ratio of LAS and CTAB is 2:1.