Corrosion inhibition effect of several amino acids on an Al-Zn-Mg-Cu alloy: Electrochemical study, DFT and MD simulation

Abstract

The corrosion inhibition performance of three amino acids, namely L-Phenylalanine (Phe), L-Methionine (Met) and L-Histidine (His) on 7150 Al alloy in 0.1 M HCl + 1 M NaCl solution was investigated by using electrochemical impedance spectroscopy (EIS), cyclic polarization, DFT and MD simulations. Electrochemical results indicate that all the studied amino acid inhibitors are cathodic type, and the inhibition efficiency follows the following order under all studied temperatures (25, 35 and 45 ℃): His > Met > Phe. A strong correlation between corrosion inhibition efficiency and DFT parameters is not evident, but the adsorption sites (N and O of NH2-COOH-, S atom of Met and two N atoms in the imidazolyl ring of His) can be determined by Fukui indices and Mulliken charges of the local atoms. In addition, MD simulations indicate that corrosion inhibition efficiency increases with the decreasing of adsorption energy.