Structure-performance relations of thio-alcohols and their synergistic corrosion inhibition for carbon steel in CO2-saturated solution

Corrosion of carbon steel in CO2-containing brine solutions is a major issue in the oil and gas industry. In this study, comparison of different structure thio-alcohols, dithiothreitol (DTT) and mercaptoethanol (ME), in synergism with oleic imidazoline (IM) for inhibiting corrosion of carbon steel in CO2-saturated oil/brine solution was investigated. The corrosion inhibition effect and mechanism of the mixed corrosion inhibitors (IM-DTT and IM-ME) were assessed using weight loss, electrochemical techniques, surface characterizations and theoretical simulations. The results demonstrate that DTT have better synergism with IM than that of ME in corrosion inhibition. IM-DTT is co-adsorbed forms a highly hydrophobic inhibition film on the specimen surface, which exhibits high stability and film persistency. DTT is preferentially adsorbs on the steel surface through S atoms, followed by the adsorption of IM through N atoms. The co-adsorbed film becomes denser due to hydrogen bonds and van der Waals interactions between IM and DTT molecule.