Corrosion Inhibition of N80 Steel by Newly Synthesized Imidazoline Based Ionic Liquid in 15% HCl Medium: Experimental and Theoretical Investigations

An imidazoline based ionic liquid, namely 2-heptadecyl-3-butyl-3-((n-methyl-thiourea) ethyl)-1H-imidazole-3-ammonium (MTOI), was prepared by a simple synthesis route. The structure of MTOI was characterized by FTIR testing. Electrochemical techniques and surface analysis tests were used to explore the corrosion inhibition behavior of MTOI on N80 steel in 15% HCl solution. The results showed that the adsorption of MTOI on the surface of N80 steel was in accordance with Langmuir isotherm, and it belongs to the mixed-type inhibitor with the maximum inhibition efficiency of 97% at 90 ppm. SEMEDS measurement verified that the N and S atoms in the ionic liquid were exactly adsorbed on the metal surface. Besides, the active nature of MTOI molecule was revealed by density functional theory (DFT) calculations, and the adsorption behavior of MTOI molecule on surface of N80 steel was elucidated by molecular dynamics (MD) simulations. This work can provide beneficial guidance for the future research of efficient and environmentally friendly ionic liquid corrosion inhibitors.