Inhibiting properties of imidazole and 2-methylimidazole as corrosion inhibitor for mild steel in hydrochloric acid

The inhibition effect of imidazole and 2-methylimidazole on the corrosion of mild steel in 1N hydrochloric acid has been studied by mass loss and polarization techniques between 303 K and 333K. The inhibition efficiency increased with increase in concentration of inhibitor and temperature from 303 K to 318 K in 1N hydrochloric acid. But higher temperature at 333 K the inhibition efficiency decreased. The corrosion rate increased with increase in temperature and decreased with increase in concentration of inhibitor compared to blank. The adsorption of inhibitor on the mild steel surface has been found to obey Temkin's adsorption isotherm. Potentiostatic polarization results reveal that imidazole and 2-methyl imidazole act as mixed type inhibitor. The values of activation energy (Ea), free energy of adsorption (Delta G(ads)), enthalpy of adsorption (Delta H), and entropy of adsorption (Delta S) were also calculated.