Molecular modeling study on inhibition performance of imidazolines for mild steel in CO2 corrosion

Corrosion inhibiting performance of 1-hydroxyethyl-2-heptadecylimidazoline (A) and 1-aminoethyl-2-heptadecylimidazoline (B) for mild steel was evaluated by combination of quantum chemistry calculation, molecular mechanics, and molecular dynamics simulation. The calculated results by quantum chemistry method demonstrated that frontier orbitals of A and B molecules are mainly located on imidazoline rings, and molecule B possesses higher reactivity than molecule A. The calculated results by molecular mechanics and molecular dynamics simulation presented that these two inhibitor molecules could form dense and high-coverage membranes to prevent diffusion of reactive corrosive species to metal surface. Furthermore, the adsorption energy, cohesive energy, and adsorption angle demonstrated that the binding affinity and stability of B membrane was remarkably greater than that of A, which indicated that B had better inhibition performance in CO2 corrosion. The calculated results were well accorded with previous reported experimental results. These researches implied that molecular modeling might be an effective approach to assess inhibition performance, which has potential application in design of new inhibitors.