Effect of alkylimidazolium ionic liquids on the corrosion inhibition of copper in sulfuric acid solution

Abstract

The effects of three newly synthesized alkylimidazolium based ionic liquids: 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO4), 1-hexyl-3-methylimidazolium hydrogen sulfate ([HMIM] HSO4), and 1-octyl-3-methylimidazolium hydrogen sulfate ([OMIM]HSO4), on the corrosion inhibition of copper in 0.5 mol · L-1 H2SO4 solution were investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. All the measurements show that these alkylimidazolium ionic liquids are excellent inhibitors for copper in sulfuric acid media and the effectiveness of these inhibitors decreases as follows: [OMIM]HSO4>[HMIM]HSO4>[BMIM]HSO4 at the same concentration. Potentiodynamic polarization studies indicate that the three inhibitors are mixed type inhibitors and that both the cathodic and anodic processes of copper corrosion are suppressed. The electrochemical impedance results were evaluated using an equivalent circuit in which two constant phase elements (CPE) were offered for these systems with two time constants. Changes in impedance parameters (charge transfer resistance and double layer capacitance) with the addition of the inhibitors also suggest that these imidazolium based molecules act by adsorbing at the copper/solution interface. The adsorption of these imidazolium based compounds on the copper surface in an acidic solution is found to fit the Langmuir adsorption isotherm. Thermodynamic calculations reveal that the adsorption of inhibitors on the metal surface occurs by a physisorption-based mechanism involving a spontaneous process. © Editorial office of Acta Physico-Chimica Sinica.