New Ionic Liquid Corrosion Performance Studies

The use of inhibitors is the most practical methods for protection against corrosion, especially in acidic media. Nowadays, a growing number of scientists and engineers have been attracted to research the novel effective and environment-friendly corrosion inhibitors due to the view of environment protection and sustainable development strategy. The specific chemical behaviour and the unique physical properties are the key factors for considering ionic liquids (ILs) as corrosion inhibitors.Three kinds of ILs were involved in this paper, namely 1-ethyl-3-methylimidazolium tetrafluoroborate([EMIM]BF4),1-butyl-3-methylimidazoliumtetrafluoroborate([BMIM]BF4),1-hexyl-3-methylimidazoliumtetrafluoroborate([HMIM]BF4)which were non-toxicity and environmentally friendly. The inhibiting performance of three ILs compands were evaluated by weight loss, electrochemical test,SEM,XPS, quantum chemical calculations and molecular dynamics modeling. This paper discussed the corrosion inhibiting mechanism of these derivatives and the relationship between the molecular structure and their inhibiting efficiency. Main achievements were listed as follows:By referring to literatures, we established and improved the synthesis methods of ILs, which enhanced products yield compared to literatures methods. According to these methods, we sythesised [EMIM]BF4,[BMIM]BF4 and [HMIM]BF4.The target products were confirmed by FT-IR and 1H-NMRWeight loss test and electrochemical measurement results indicated that ILs were effective corrosion inhibitors for carbon steel in HC1 solutions. All measurements showed that the inhibition efficiency increased with increase in the concentration of inhibitor and the effectiveness of these inhibitors was in the order of [EMIM]BF4< [BMIM]BF4<[HMIM]BF4. The inhibition mechanism was that ILs moleculars absorbed on carbon steel surface forming a layer of dense protective film and inhibited its electrochemical cathode and anode processes to reduce the corrosion current density. Polarization curves revealed that the studied inhibitors were mixed type inhibitors.The adsorption of the inhibitors on the aluminum surface obeyed Langmuir adsorption isotherm. X-ray photoelectron spectroscopy and the thermodynamic data of adsorption showed that inhibition of steel corrosion in HC1 solution by ILs is due to the formation of a chemisorbed film on the steel surface. Surface analysis by SEM indicated a considerable reduction of corrosion products after the addition of ILs.The inhibition performance of three corrosion inhibitors in HC1 mild steel corrosions about the molecular structure, the absorption sites of these corrosion inhibitors has been theoretically evaluated by quantum chemistry calculations and molecular dynamics simulations. It is useful to provide some valuable information to synthetic new corrosion inhibitors.