Theoretical MD/DFT computer explorations and surface-electrochemical investigations of the zinc/iron metal cations interactions with highly active molecules from Lemon balm extract toward the steel corrosion retardation in saline solution

Abstract

By molecular-scale simulations and electronic-scale computational investigations combined with electrochemical techniques, the green water extract of Lemon balm (L.B)/zinc ions mixtures synergistic effect on the steel corrosion retardation in a saline electrolyte was assessed. The L.B-Zn2+/B.E-Fe2+chelates formation was confirmed by UV–Vis and FT-IR spectroscopy results. Electrochemical investigations results showed a 93% inhibition value when 200 ppm L.B was blended with 600 ppm Zn2+ ions in the saline solution. DC polarization measurements indicated that a mixed type inhibition mechanism had been provided by 200:600 ppm mixture of L.B-Zn2+, leading to the lowest icorr. Uniform L.B-Zn2+/L.B-Fe2+ based protective film growth over the surface of the metal was proved by GIXRD, AFM, and FE-SEM experiments explorations. The adsorptivity of Zn+2 cation complexes with Lemon balm compounds on the metallic adsorbent was described by molecular-scale calculations (MC and MD).