Synthesis and evaluation of 1-butyl-3-methylimidazolium chloride based ionic liquid for acid corrosion inhibition of aluminum alloy: Empirical, DFT/MD-simulation and RSM modeling

Abstract

The present research explores the synthesis of imidazolium based ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]) and its application for the protection of aluminum alloy (AA) in 1 M H2SO4 electrolyte using gravimetric, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), response surface methodology (RSM), density functional theory (DFT) and MD-simulation respectively. The studied (IL) showed appreciable inhibition efficiencies of 84.21 % for gravimetric, 90 % for PDP and 87.10 % for the EIS at 0.80 g/L inhibitor concentration and 313 K, respectively. The results of EIS and PDP reveal the corrosion inhibition process is charge transfer controlled, and the studied IL acts as a mixed type inhibitor. The optimization result via RSM model gave an optimum prediction of 84.21 % at 0.8 g/L inhibitor concentration at 313 K. Adsorption of [BMIM][Cl] on the aluminum surface obeyed the Frumkin adsorption isotherm. The scanning electron microscope (SEM) and atomic force microscopy (AFM) revealed the formation of protective film of the inhibitor on the aluminum surface. Theoretical modeling were used to correlate the experimental results. The best fit of the theoretical models were functions of molecular structure and fractions of electron transferred from the inhibitor to the aluminum surface.