Effect of OH, NH2 and OCH3 groups on the corrosion inhibition efficacy of three new 2,4,5-trisubstituted imidazole derivatives on mild steel in acidic solutions: Experimental, surface and DFT explorations

Abstract Three new imidazole derivatives namely,4-(4,5-bis(4-methoxyphenyl)-1H-imidazol-2-yl)phenol (IM1), 4-(4,5-bis(4-methoxyphenyl)-1H-imidazol-2-yl)benzenamine (IM2), 2,4,5-tris(4-methoxy phenyl)-1H-imidazole (IM3) were synthesized using microwave irradiation method. The noteworthy highlights of this method are safe reaction profiles, broad substrate scope, short run time, catalyst-free, excellent yields, economical, solvent-free, and simple workup conditions. The structural characterization of all the imidazole derivatives has been confirmed by 1HNMR and mass spectral techniques. The corrosion inhibition potential of all the imidazoles was explored using weight loss and electrochemical methods. The imidazole derivative (IM1) bearing a hydroxyl group exhibited maximum corrosion inhibition efficiency compared to other imidazoles (up to 96%). Strong adsorption of studied imidazole molecules followed the Langmuir model with very good correlation coefficients. The calculated Gibbs free energy of adsorption values suggested the mixed type of adsorption (physisorption and chemisorption). The polarization measurements indicated studied imidazole derivatives as mixed types of corrosion inhibitors. Further, scanning electron microscopy (SEM), XPS and XRD were performed to study the surface morphology of Mild steel (MS) surface. Quantum chemical calculations (DFT) was used to prove the obtained inhibition efficiencies (η %).