Theoretical evaluation of corrosion inhibition performance of benzimidazole corrosion inhibitors

The inhibition performance of four corrosion inhibitors in HCl mild steel corrosions, including 2-mercaptobenzimidazole (A), 2-amidobenzimidazole (B), 2-methylbenzimidazole (C), and benzimidazole (D), was theoretically evaluated using quantum chemistry calculations and molecular dynamics simulations, and the corrosion inhibition mechanism was analyzed. Global activity indices indicated that 2-mercapitobenzimidazole bore the highest reaction activity among the four molecules. For the three other molecules, Fukui indices and total electron density distributions suggested that 2-amidobenzimidazole possessed two electrophilic attack centers, which enabled multicenter adsorption of the molecule on metal surfaces and thus had preferable corrosion inhibition performance compared to 2-methylbenzimidazole and benzimidazole. Molecular dynamics simulation results showed that 2methylbenzimidazole was more stably adsorbed on the metal surfaces than benzimidazole did when the interaction of the inhibitor molecules with three layers of iron atoms was considered. With the help of the theoretical results, the efficiency order of the four inhibitors was found to be A > B > C > D, which accorded well with experimental results.