Elucidating the corrosion inhibition mechanism of benzimidazole-based molecules on carbon steel: An integrated experimental and DFT/DFTB/MD molecular modelling study.

A range of both practical and theoretical methods was employed to dissect the effectiveness of two 2-(Alkylphenyl)-1H-benzo[d]imidazole-1-yl)acetates namely naphthalen-1-yl 2-(2-(p-tolyl)-1H-benzo[d]imidazole-1-yl)acetate (NTMBIA) and naphthalen-1-yl 2-(2-(4-nitrophenyl)-1H-benzo[d]imidazole-1-yl)acetate (NNBIA) in impeding the corrosion of carbon steel in acidic media. The methyl group on the phenyl ring in NTMBIA acts as an electron donor, enhancing its inhibition efficiency to 95.45%, whereas NNBIA, with its electron -withdrawing nitro group, achieves only 85.60% at the highest concentration. Findings from potentiodynamic polarization (PDP) tests indicated that these 2-(Alkylphenyl)-1H-benzo[d]imidazole-1-yl)acetates can reduce carbon-steel corrosion, functioning as mixed-type inhibitors. Scanning electron microscopy (SEM) & energy dispersive X-ray (EDX) analyses revealed the inhibitory effect of these molecules through their adsorption on the carbon steel/surface. The chemisorption of these acetates on the metal surface is consistent with the Langmuir isotherm. Additionally, quantum chemical calculations, focusing on global and local chemical reactivity parameters, were conducted and thoroughly analyzed to explore the potential anticorrosive role of these compounds. Density Functional Theory (DFT) analyses display that both NNBIA and NTMBIA interact greatly with metal surfaces through the 1H-benzo[d]imidazole scaffold of the molecule, with additional contributions from oxygen carbonyl groups. MD and DFTB simulations reveal that NTMBIAH + exhibits increased reactivity toward the iron surface, corroborating experimental results.