Computational Simulation of the Adsorption Behavior of Benzimidazolone Derivatives as Inhibitors for Ordinary Steel Corrosion in HCl 1M

The adsorption behavior of Benzimidazol-2-one (Bz), 5-Methylbenzimidazol-2-one(CH3Bz) and 5-Chlorobenzimidazol-2-one (ClBz) as inhibitors for mild steel corrosion in HCl 1M have been studied computationally using density functional theory (DFT) calculations with the hybrid B3LYP functional. The calculations were focused on the protonated forms of the molecules under study, seeing that these classes of inhibitors can easily be protonated in acidic medium. The most preferred protonation centers were determined proton affinity (PA). Fukui indices have been computed to evaluate the nucleophilic and electrophilic sites of atoms in the molecule. The interaction of the inhibitors with the iron surface was studied by calculating the combined energy (Ecom) and the free energy of adsorption ( ΔG°ads ). Observable correlation was found between experimental corrosion inhibition efficiency and the theoretical data. The molecular dynamics (MD) and Monte Carlo (MC) simulations used show that all investigated Benzimidazol inhibitors are positioned parallel to the metal surface reflecting the coverage of a large portion of the steel surface.