Investigation of imidazole derivatives as corrosion inhibitors for mild steel in sulfuric acidic environment: experimental and theoretical studies

In this work, we are interested in studying the effect of the addition of three heterocyclic organic compound derived from imidazole, namely 2-(1,4,5-triphenyl-1H-imidazol-2-yl)phenol (IM-OH), 1,4,5-triphenyl-2-(4-metyoxyphenyl)-1H-imidazole (IM-OCH3), and 3-methoxy-4-(1,4,5-triphenyl-1H-imidazol-2-yl)phenol (IM-H) on the corrosion inhibition of mild steel in acidic medium H2SO4 0.5 M. This study was performed using weight loss and electrochemical and theoretical investigations. The obtained results indicate that IM-OH, IM-OCH3, and IM-H act as excellent inhibitors for mild steel in H2SO4 0.5 M. The results obtained from the electrochemical methods show that IM-OH, IM-OCH3, and IM-H imparted high resistance and behave as mixed type inhibitors. Inhibition efficiency (IE %) increases with the increase of inhibitors concentration to attain 97.7%, 98.9%, and 88.9% at 10−3 M of IM-OH, IM-OCH3, and IM-H respectively. EIS data is analyzed to model the inhibition process through appropriate equivalent circuit model. Thermodynamic and kinetic parameters controlling the adsorption process are calculated and discussed. In addition, the surface of the mild steel has been analyzed by the SEM-EDAX. The theoretical results were in good agreement with experimental measurements.