화학공학소재연구정보센터
Journal of Materials Science, Vol.53, No.20, 14666-14680, 2018
Enhanced inhibitive performance of fluoro-substituted imidazolium-based ionic liquid for mild steel corrosion in hydrochloric acid at elevated temperature
In this work, two imidazolium-based ionic liquids 1-(2-aminoethyl)-1-dodecyl-2-methyl-4,5-dihydro-1H-imidazol-1-ium chloride ([ADMDI]Cl) and 1-(2-aminoethyl)-1-dodecyl-2-(trifluoromethyl)-4,5-dihydro-1H-imidazol-1-ium chloride ([ADTDI]Cl) were synthesized for the first time and their inhibitive effects on the corrosion of mild steel in 0.5 M HCl solution at elevated temperature were investigated by experimental and theoretical methods. The results of weight loss tests show the studied ionic liquids (ILs) can effectively retard the serious corrosion of mild steel and that the greatest efficiencies obtained at 368 K are 86.3% for [ADMDI[Cl and 92.7% for [ADTDI]Cl. Potentiodynamic polarization curves suggest those compounds act as cathodic-type inhibitors and that [ADTDI]Cl has the better inhibiting performance than [ADMDI]Cl, especially at low concentration. It is indicated by the study of scanning electron microscope (SEM) that both the surface morphology and the internal structure of mild steel samples are severely damaged by the corrosive environment at 368 K. However, such bad situation is greatly improved by using IL additives. The higher inhibition efficiency of fluoro-substituted IL proved by experimental results can be explained by theoretical studies. The data of quantum chemical calculations show the introduction of fluoro group can increase the amount of free electrons transferred from IL molecule to the vacant d-orbital of Fe atom and strengthen the dipole-dipole interaction between inhibitor and metal surface. Additionally, molecular dynamics simulations suggest [ADTDI]Cl has the higher adsorption energy than [ADMDI]Cl, which also confirms the better performance of the former as corrosion inhibitor for mild steel in acid environment at elevated temperature.