New Benzimidazole derivatives as efficient organic inhibitors of mild steel corrosion in hydrochloric acid medium: Electrochemical, SEM/EDX, MC, and DFT studies

Abstract

The corrosion of mild steel (MS), a widely used material in industry, represents a significant global challenge. In order to extend the durability of equipment, the use of corrosion inhibitors proves to be an effective solution, particularly in corrosive environments. In this research, two newly synthesized benzimidazole derivatives, namely 1-(cyclohex-1-en-1-yl)-3-[(3-phenyl-1,2-oxazol-5-yl)methyl]-2,3-dihydro-1H-1,3-benzodiazol-2-one (Benz1) and 1-(cyclohex-1-en-1-yl)-3-[(3-phenyl-4, 5-dihydro-1,2-oxazol-5-yl)methyl]-2,3-dihydro-1H-1,3-benzodiazol-2-one (Benz2), were evaluated as corrosion inhibitors for MS in 1 M hydrochloric acid solution. This study was conducted using both experimental methods and computational approaches. Potentiodynamic polarization diagrams (PDP) indicate that, depending on concentration effects, Benz1 and 2 function as mixed-type inhibitors, with a predominance of cathodic inhibition. The results of electrochemical impedance spectroscopy (EIS) show that the compounds tested offer high inhibition efficiencies of 96.32 % and 98.30 % at 10−⁴ M for Benz1 and 2, respectively. Inhibitor adsorption follows the Langmuir isotherm and involves chemisorption. SEM/EDX analyses confirm the presence of a protective film on the metal. In addition, DFT and Monte Carlo simulations reveal significant adsorption of the compounds on the MS surface, underlining their high potential as effective corrosion inhibitors.