Investigation Of Limidazolium Based Ionic Liquid As Inhibitors For X65 Steel In 0.5M Sulfuric Acid

As an excellent steel,X65 has been highly applied in modern industry.The study of the corrosion process in H2SO4 solution and the inhibition action of ionic liquids for X65 steel can provide theoretical and practical significance to select efficient inhibitor in in the actual industry.Nowadays,with the needs of environmental protection and the sustainable development,more and more eco-friendly substances are studied as corrosion inhibitors.Ionic liquids(ILs)are new green solvent,they have unique characteristics which are low toxicity,low vapor pressure,good solubility,stable thermal ability and good designability.So they have been investigated as inhibitors in recent years.In this paper,a vinyl based limidazolium bromide and four allyl based limidazolium bromide molecules were chosed as the corrosion inhibitors.They were 1-vinyl-3-ethylimidazolium bromide([VEIM]Br),1-allyl-3-ethylimidazolium bromide([AEIM]Br),1-allyl-3-butylimidazolium bromide([VBIM]Br),1-allyl-3-hexylimidazolium bromide([VHIM]Br),1-allyl-3-octylimidazolium bromide([VOIM]Br).Several technologies which are measurements of potentiodynamic polarization,electrochemical impedance spectroscopy(EIS),weight loss test,scanning electronic microscope(SEM)analysis and quantum chemical calculations analysis method have used to study the inhibition action of these five inhibitors and evaluate their inhibition effect for X65 steel in 0.5 M H2SO4 solution.The main results of this paper are represented as follows:(1)The EIS results showed that the diameter Rct changed larger with the increasing concentration of the test inhibitor.Compared with the blank one,the double layer capacitances got smaller which indicated that inhibitor affected through its displacement of water and forming a thin film on the X65 steel surface.Thus the charge-transfer became more difficult and a higher inhibition efficiency was obtained.(2)The potentiodynamic polarization curves revealed that the corrosion current density decreased and the inhibition efficiency increased when concentration got higher.The Tafel polarization curves showed that the test molecule mainly retarded the hydrogen ions reaction on the cathodic region while not changing the mechanisms of cathodic and anodic corrosion reactions.The displacement of Ecorr was less than 85 mV,which suggested that these substances were mixed-type inhibitors.(3)The corrosion rates decreased with the addition of inhibitors in weight loss measurements.The inhibition efficiencies gained from weight loss tests were in agreement with EIS and polarization results.(4)The adsorption analysis showed that the five inhibitors on the X65 steel in 0.5 M H2SO4 solution obeyed the Langmuir isotherm model.The negative values of (6(90 showed that the adsorption on the X65 steel surface was a spontaneous process,and the adsorption mechanism was the contribution of both physisorption and chemisorption.(5)From the quantum chemical calculations results,we found that low molecular band(?E)value and high dipole moment(?)were related to the inhibition efficiency.The occuipied molecular orbital of LUMO(ELUMO)were higher and molecular orbital of HOMO(EHOMO)were lower,the molecular band(?E)became smaller.Hence,the interaction between the inhibitor and X65 steel got stronger,and a berrer inhibition effect was obtained.In conclusion,that the five limidazolium based ionic liquids presented good inhibition for the corrosion of X65 steel in 0.5 M H2SO4 solution.The SEM images showed a protective surface was formed after adding the inhibitors,which verified the conculsion from electrochemical measurements and weight loss tests.The arrangement of these limidazolium based ionic liquids inhibition effect was: [AOIM]Br > [AHIM]Br> [ABIM]Br> [AEIM]Br> [VEIM]Br.