Corrosion inhibition of mild steel in acidic medium by simple azole-based aromatic compounds

Many organic corrosion inhibitors are complex and may include complicated chemical structures, mixture of different species, or require numerous and tedious preparation steps. In this study, we demonstrate inhibition by triazole- and imidazole-based compounds, which are synthesized in a one-step method and possess austere chemical structures. The inhibition effect was studied on the corrosion of mild steel in 1.0 M HCl solution at 40 °C by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and weight loss. Results from electrochemical measurements showed that the aromatic compounds were effective in inhibiting corrosion in acidic medium, such that the inhibition efficiency increased with increasing inhibitor concentration. The triazole-based compound had the best inhibitive performance (efficiency >90%), followed by the imidazole-based (~85%), at a concentration of 850 μM. These results were supported by analyses obtained from scanning electron and atomic force microscopy, which showed improved mild steel topology and decrease in surface roughness by up to a factor of five, and x-ray diffraction, which revealed the extent of oxide layer formation. In addition, the adsorption of a protective inhibitor layer on the metal surface was confirmed by Raman spectroscopy, while the underlying mode and mechanism were postulated based on a Langmuir adsorption isotherm and computational studies, which showed good correlation between the inhibitive ability and the electron donating and accepting capability of the compounds.