Experimental and Quantum Chemical Studies of Some Bis(trifluoromethyl-sulfonyl) Imide Imidazolium-Based Ionic Liquids as Corrosion Inhibitors for Mild Steel in Hydrochloric Acid Solution

The corrosion inhibition of mild steel in 1.0 M HCl solution by some selected imidazolium-based ionic liquids, namely 1-propyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl) imide ([PMIM][NTf2), 1-butyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl) imide ([BMIM][NTf2), 1-hexyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl) imide ([HMIM][NTf2]), and 1-propyl-2,3-methylimidazolium bis(trifluoromethyl-sulfonyl) imide ([PDMIM][NTf2]) was investigated using weight loss, electrochemical measurements, and quantum chemical calculations. All ionic liquids showed appreciable inhibition efficiency. Among the ionic liquids studied, [PDMIM][NTf2] exhibited the best inhibition efficiency. The results from the weight loss, electrochemical measurements and quantum chemical calculations show that the order of inhibition efficiency by the ionic liquids follow the order [PDMIM][NTf2] > [HMIM][NTf2] > [BMIM][NTf2] > [PMIM][NTf2]. At 303 K, polarization measurements indicated that all the studied compounds are mixed...