Enhanced corrosion resistance of low alloy steel in NaCl environment using 3-substituted chromone derivatives in epoxy coatings

Abstract

This study investigates the corrosion-controlling impact of newly synthesized 3-substituted chromone derivatives incorporated as eco-friendly additives in epoxy coatings to improve the corrosion resistance of low alloy steel (LAS) exposed to a corrosive 3.5 % NaCl solution. This is the first time, as far as we know, that such a chromone-based compound has been investigated for use in coatings, marking a significant advancement from traditional toxic corrosion inhibitors to environmentally benign alternatives. The novel chromone derivates were characterized by 1H NMR, 13C NMR, and FT-IR. 3-substituted chromone derivates were applied to LAS substrates and evaluated for their corrosion protection using electrochemical impedance spectroscopy(EIS) and potentiodynamic polarization techniques(PDP) at 298 K at various concentrations (0.25 %, 0.50 %, and 1.00 %), where 0.25 wt% were identified as an optimized concentration for all compounds. Furthermore, EIS and potentiodynamic polarization studies of the various formed coatings also revealed that 0.25 % of (E)‑prop-2-yn-1-yl 3-(7‑hydroxy-4-oxo-4H-chromen-3-yl) acrylate (MSC-5) was the most optimized coating, with an outstanding protection efficacy of 96.91 % even after 336 h of immersion in a 3.5 % NaCl solution. An improvement attributed to the presence of phenolic -OH in MSC-5 enhanced the adhesion and barrier properties of the coating. Contact angle measurements demonstrated the hydrophobicity order of the BS < Epoxy < MSC < MSC-4 < MSC-5-containing coating and highlighted their efficacy as a moisture-resistant barrier. Atomic Force Microscopy (AFM) and FESEM analyses further illustrated the homogeneous dispersion of MSC-5 within the epoxy matrix, with minimal pores or microcracks, thus contributing to the coating's integrity and corrosion resistance. Furthermore, the protective properties of the coating were reinforced by the donor-acceptor interaction using density functional theory. © 2024 Elsevier B.V.