Synergism of 2-mercaptobenzimidazole and oleic imidazoline on corrosion inhibition of carbon steel in CO2 -saturated brine solutions

The inhibition properties of 2-mercaptobenzimidazole (MBI) and its synergism with oleic imidazoline (OIM) for carbon steel in CO 2 -saturated brine solution were investigated by electrochemical, weight loss measurements, surface analysis and quantum chemical calculations. The effectiveness of MBI for OIM was also compared to the other sulfur-containing corrosion inhibitors such as 2-mercaptothanol (ME), mercaptoacetic acid (TGA), and thiourea (TU). The results show that a mixture of MBI and OIM gave a better synergistic corrosion inhibition than that of ME, TGA, and TU. OIM is protonated and coupled with MBI by hydrogen bonding to co-adsorb on the carbon steel surface. MBI adsorbs on Fe by a bidentate binding N S bridge connection, which effectively prevents the carbon steel from CO 2 corrosion.