Abstract
The corrosion potential of three newly studied ionic liquids (ILs) namely, 5-(Trifluoromethyl) dibenzothiopheniumtetrafluoroborate (TDTB), 5-(Trifluoromethyl)dibenzothiopheniumtrifluoromethanesulfonate (TDTM) and 1-Ethyl-3-methylimidazolium ethyl sulfate (EMIM)(ESO4) were investigated for mild steel (MS) in 1 M hydrochloric acid using electrochemical, Fourier transform infrared (FTIR) spectroscopy and gravimetric techniques. The potentiodynamic polarization data shows that the three inhibitor molecules studied possess characteristics that correspond to mixed-type inhibitors but TDTM exhibits more anodic characteristics. Scanning electron microscopy (SEM) was used for the surface studies. Remarkable corrosion inhibition of mild steel was also predicted using energy dispersive spectroscopy (EDS). FTIR spectroscopy established the functional group interrelationship showing disappearance of characteristic absorption bands in the adsorption film FTIR spectra. Quantum chemical calculations and Monte Carlo models were utilized to gain more insight into the electronic properties of the compounds in relation to the corrosion inhibition effect and the binding and/or adsorption of ionic liquids on the surfaces of MS. The adsorption energy adopts the order: TDTB ≈ TDTM >(EMIM)(ESO4). The numerical values of adsorption energy is −3.72 kcal mol−1, −3.77 kcal mol−1 and −3.04 kcal mol−1 for TDTB, TDTM and (EMIM)(ESO4), respectively.
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