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

Abstract

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.