Ionic liquids derived from α-amino acid ester salts as potent green corrosion inhibitors for mild steel in 1M HCl

In 1 M HCl solution, three selected amino acid ester salt based ionic liquids ([AAE][Sac] ILs), namely L-Phenyl Alanine methyl ester saccharinate ([PheME][Sac]), L-Leucine methyl ester saccharinate ([LeuME][Sac]), and L-Alanine methyl ester saccharinate ([AlaME][Sac]) under static conditions were examined as potent green corrosion inhibitors for mild steel by means of electrochemical measurements, weight loss, FT-IR spectroscopy, contact angle measurement, UV–vis spectroscopy, SEM/EDAX study, quantum chemical calculations and Monte Carlo (MC) simulation studies. ¹H NMR, and FTIR spectroscopy has confirmed the structure of obtained ILs. The investigations were done in the temperature range of 303–353 K. [AAE][Sac] ILs are assessed as an efficient steel corrosion inhibitors in 1 M HCl up to 333 K but have less inhibiting properties above 333 K i.e., 343 and 353 K. Among the [AAE][Sac] ILs analysed, [PheME][Sac] showed the greatest inhibition efficiency and obey the order as: [PheME][Sac] > [LeuME][Sac] > [AlaME][Sac]. Polarization measurements showed all the [AAE][Sac] ILs tested to be mixed-type inhibitors. The adsorption of the examined [AAE][Sac] ILs obeyed the Langmuir adsorption isotherm perfectly. The theoretical descriptors provided by quantum chemical calculations and advanced MC simulation also reinforced the experimental conclusions adequately.