Influence of the Molecular Structure on the Inhibitor Properties of Benzimidazole Derivatives on Mild Steel Corrosion in 1 M Hydrochloric Acid

Six benzimidazole derivatives were investigated as corrosion inhibitors on mild steel in 1 M hydrochloric acid (HCl) using gravimetric and polarization techniques. Inhibitor efficiency was found to depend on concentration and on the structure of the molecules. The results were interpreted by means of an adsorption model based on inhibitor adsorption in the form of nonprotonated and protonated molecules. Five of the six examined compounds adsorbed according to the Frumkin adsorption isotherm. An attempt was made to find a correlation between the inhibition efficiency and some parameters of the electronic structure of the molecule, like induction and resonance effects of the substituents and ionization potential. A correlation also was attempted between the inhibition efficiency and some parameters of the chemical structure of the molecule, like the molecular area and others. No simple correlation was found to exist.