Inhibition performances of imidazole derivatives with increasing fluorine atom contents in anions against carbon steel corrosion in 1 M HCl

摘要

This work tests the anti-corrosion ability of three imidazolium-based ionic liquids with different anions-bis (fluorosulfon)imide ([FSI](-)), bis(trifluoromethylsulfonyl)imide ([NTF2](-)) and bis( pentafluoroethylsulfon) imide ([BETI](-))-on carbon steels in 1 M HCl solution at 298 K. Electrochemical impedance spectroscopy (EIS) indicated that increasing the number of -CF2 groups in the anion vastly enhanced the corrosion-inhibition efficiency (eta). Even at small concentrations (1.25 mM), [(OHC2)MIm][BETI] achieved an eta of 86%. The polarisation curve verified that [(OHC2)MIm][BETI] acted as a mixed-type inhibitor and that its adsorption followed the EI-Away adsorption model. Scanning electron microscope (SEM) imaging intuitively confirmed the superior inhibition performance of [(OHC2)MIm][BETI]. X-ray photoelectron spectroscopy (XPS) showed that [(OHC2)MIm] [BETI] was stably absorbed on the carbon-steel surface. Contact angle measurements indicated that adding the -CF2 groups effectively decreased the hydrophilicity and surface energy of carbon steel from 69.39 to 19.93 mJ/m(2), hindering the adsorption of water molecules. Moreover, a frontier molecular orbital theory (FMOT) study confirmed that the -CF2 groups enhanced the donation and drawing of electrons, and molecular dynamics (MD) simulations revealed that they reduced the interaction energy (E-interact) values between the corrosion inhibitor molecule and the iron surface (from -321.08 to -612.74 kJ.mol(-1)). It was inferred that among the three ionic liquids, [(OHC2)MIm][BETI] absorbed most strongly to the carbon-steel surface. (C) 2020 Elsevier B.V. All rights reserved.