Synthesis and assessment of ionic liquid derived from benzalkonium chloride as corrosion inhibitor for carbon steel

Abstract

Abstract Corrosion poses a significant challenge in the materials industry, especially when carbon steel (C-steel) is subjected to highly corrosive environments such as 1 M HCl. In this study, four ionic liquids (ILs)-1-benzyl-1-methylpiperidin-1-ium chloride (IL I ), 1-benzyl-2-methylpyridin-1-ium chloride (IL II ), 1-benzyl-3-methylpyridin-1-ium chloride (IL III ), and 1-benzyl-4-methylpyridin-1-ium chloride (IL IV ) were synthesized and characterized using spectroscopic techniques, including FT-IR and 1 HNMR. Electrochemical analyses such as potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) demonstrated excellent protective performance for C-steel in 1 M HCl, reaching a maximum inhibition of 97% at an optimum concentration of 100 ppm. Insights from polarization and impedance analyses confirmed that these compounds act as mixed-type inhibitors by adhering to the steel surface. The adsorption behavior followed the Langmuir isotherm model, with ΔG 0 ads values suggesting a combination of physisorption and chemisorption. Quantum chemical assessments validated the experimental results, indicating that IL II –IL IV , due to their two aromatic rings, exhibited superior surface interaction and inhibition efficiency because of their reduced HOMO-LUMO energy gaps. These findings affirm the strong inhibitory potential of the tested ILs in acidic media.