Investigation of anticorrosive properties of some ionic liquids on mild steel in hydrochloric acid

摘要

The corrosion potential of three ionic liquids (ILs) namely, 5-(Trifluoromethyl)dibenzothiopheniumtetrafluoroborate (TDTB), 5-(Trifluoromethyl)dibenzothiophenium trifluoromethanesulfonate (TDTM)and 1-Ethyl-3-methylimidazolium ethyl sulfate [EMIM][ESO_4] was studied for mild steel and zinccorrosion in 1.0 M hydrochloric acid using electrochemical, spectroscopic and gravimetrictechniques. The studied ILs showed appreciable inhibition efficiencies at the consideredconcentration range. The highest inhibition efficiencies were observed at 30°C when inhibitorconcentration was 8.0 × 10-2 M. The gravimetric data revealed that inhibition efficienciesdecreased with an increase in temperature, the lowest inhibition efficiencies for mild steel and zincwere observed at 50°C. The potentiodynamic polarization results indicated that all three inhibitorsare mixed-type inhibitors, with TDTM being a predominantly anodic inhibitor. The adsorption of thestudied ILs on mild steel and zinc obeyed the Langmuir adsorption isotherm. The Gibbs freeenergy of adsorption (ΔG°ads) indicated that the adsorption process was spontaneous, and thatcorrosion inhibition occurred by a physical adsorption process. Surface morphology analysisthrough scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) revealeda great improvement in the surface morphologies of mild steel and zinc specimens in the inhibitedsystems. The Fourier transform infrared spectroscopy studies confirmed the chemical interactionsbetween the metal surface and the ILs. This is observed by the disappearance of characteristicabsorption bands in the adsorption film FTIR spectra.