Inhibition of acid corrosion of carbon steel using four imidazolium tetrafluoroborates ionic liquids

In the present paper, four ionic liquids namely:3-Decyl-1-methyl-1H-imidazol-3-ium tetrafluoroborate (IL1), 3-Dodecyl-1-methyl-1H-imidazol-3-ium tetrafluoroborate (IL2), 3-Decyl-1,2-dimethyl-1H-imidazol-3-ium tetrafluoroborate (IL3) and 3-Dodecyl-1,2-dimethyl-1H-imidazol-3-ium tetrafluoroborate (IL4), were synthesized, characterized and tested as corrosion inhibitors for carbon steel in 1.0 M HCl solution. The molecular structure and characterizations of these ionic liquids were confirmed by elemental analysis, FTIR, X-Ray Diffraction (XRD), thermo gravimetric analysis (TGA) and 1H NMR spectroscopy. The corrosion performance of the ionic liquids was evaluated by using polarization and electrochemical impedance spectroscopy (EIS) measurements. The compounds presented relatively good inhibition efficiencies at 200 ppm. The order of the inhibition efficiency is as follows: IL4 > IL3 > IL2 > IL1. The adsorption of the studied ionic liquids obeyed the Temkin adsorption isotherm.