Two new amino acid derivatives as green corrosion inhibitors against Q235 steel in HCl solution: Experimental and theoretical investigations

Amino acids have emerged as promising green alternatives to replace toxic inhibitors in corrosion protection applications. In this study, we present a one-step synthetic approach for the functionalization of methionine and cysteine using p-tert-butylbenzoic acid (P-Meth and P-Cys), which have super protective performance to metals against corrosions. The corrosion rates of Q235 steel in 1 M HCl were reduced from 4.542 to 0.202 and 0.312 mg·h-1cm-2 in the presence of 100 mg·h-1 P-Meth and P-Cys, respectively. The surface structures of Q235 steel were not broken after 12 h in 1 M HCl mediums. The charge transfer resistances of corrosion reactions were enhanced by 12 and 9 times in the presence of P-Meth and P-Cys, respectively. Both of P-Meth and P-Cys were adsorbed onto Q235 steel by chemical actions generally, accompanying with a little physical action. Molecular dynamic simulations demonstrate that P-Meth has higher binding energies onto Q235 steel than P-Cys. The study is significant for the corrosion protections of metals with green and environmental-friend methods.