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 to get 4-(tert-butyl)benzoyl)methionine (P-Meth) and 4-(tert-butyl)benzoyl)cysteine (P-Cys) through the acylation reactions between methionine or cysteine and p-tert-butylbenzoic acid, respectively, which exhibit a super protective performance toward metals against corrosion. The corrosion rates of Q235 steel in 1 M HCl were reduced from 4.542 to 0.202 and 0.312 mg·h⁻¹·cm⁻² in the presence of 100 mg·L⁻¹ P-Meth and P-Cys, respectively. The surface structures of Q235 steel remained unbroken after 12 h in 1 M HCl medium. The charge transfer resistances of corrosion reactions were enhanced by 12 and 9 times in the presence of P-Meth and P-Cys, respectively. P-Meth and P-Cys were adsorbed onto the Q235 steel via chemical actions, which were accompanied by minimal physical action. Molecular dynamic simulations demonstrate the higher binding energy of P-Meth onto Q235 steel than P-Cys. The study contributes to the corrosion protection of metals with green and environmentally friendly methods.