Corrosion inhibition of aluminum in hydrochloric acid solution by alkylimidazolium ionic liquids

The effects of newly synthesized three alkylimidazolium ionic liquids-1-butyl-3-methylimidazolium chlorides (BMIC), 1-hexyl-3-methylimidazolium chlorides (HMIC) and 1-octyl-3-methylimidazolium chlorides (OMIC)-on the corrosion of aluminum in 1.0 M HCl were investigated using potentiodynamic polarization, electrochemical impedance spectroscopy and weight loss methods. All measurements showed that the inhibition efficiency increased with increase in the concentration of inhibitor and the effectiveness of these inhibitors was in the order of OMIC > HMIC > BMIC. Polarization curves revealed that the studied inhibitors were mixed type inhibitors. The adsorption of the inhibitors on the aluminum surface obeyed Langmuir adsorption isotherm and had a physical mechanism. The effect of temperature on the corrosion behavior in the presence of 5 x 10(-3) M of inhibitors was studied in the temperature range of 303-333 K. The associated activation energy of corrosion and other thermodynamic parameters such as enthalpy of activation (Delta H), entropy of activation (Delta S), adsorption equilibrium constant (K-ads) and free energy of adsorption (Delta G(ads)) were calculated to elaborate the mechanism of corrosion inhibition. (C) 2009 Elsevier B.V. All rights reserved.