Theoretical design of green corrosion inhibitors using novel benzimidazolyl-pentane-1,2,3,4,5-pentaol derivatives as a case study: DFT calculations, Monte Carlo simulations and ecotoxicity prediction

In an effort to improve the practical application of benzimidazoles as corrosion inhibitors, hydrophilic groups were introduced through the attachment of aldoses to the benzimidazole ring. In this study, computational techniques, including DFT calculations and Monte Carlo simulations were used to predict the potentials of new aldo-benzimidazoles (benzimidazolyl-pentane-1,2,3,4,5-pentaol) as corrosion inhibitors for mild steel in aqueous acid media. The results showed that the compounds, which are inherently more hydrophilic than native benzimidazoles promise to exhibit higher corrosion inhibition efficiencies than conventional benzimidazole derivatives. Highly electron-donating (e.g. -OCH3) and electron-withdrawing (e.g. -NO2) substituents increased the corrosion inhibition efficiencies, making g-bzm-methoxy and g-bzm-nitro to have the highest corrosion inhibition efficiencies as predicted from the QSAR model. All the compounds showed appreciable adsorption energies on Fe(1 1 0) surface with bond distances that suggest non-covalent interactions between the N-atom of the benzimidazole ring and Fe. All the compounds showed lower toxicity to fathead minnow than benzimidazole except g-bzm-benzophenone, g-bzm-diCl, and g-bzm-dimethyl. The compounds also exhibited lower toxicity to Daphnia magna and T. pyriformis, suggesting their eco-friendly attributes. The study provides insights into the sustainability of benzimidazolyl-pentane-1,2,3,4,5-pentaol derivatives as corrosion inhibitors and recommends complementary experimental studies on the compounds.