Enhanced corrosion inhibition of mild steel in concrete pore solution using modified mgo-chitosan epoxy nanocomposite coatings

Abstract

In this study, epoxy-based coatings (pure epoxy, MgO-modified, chitosan-modified, and MgO-chitosan nano-composite) were applied to polished mild steel in a simulated concrete pore solution. The coatings were formulated by dispersing MgO nanoparticles and chitosan into an epoxy resin, homogenised by stirring, applied via the glass slide method, and cured. Electrochemical analysis (open-circuit potential, Nyquist, and Tafel plots) demonstrated the superior performance of the nanocomposite, which exhibited the highest charge-transfer resistance and lowest corrosion current density (Icorr = 2.076 × 10 − 4). Weight loss tests confirmed a 93.53 % inhibition efficiency, outperforming the uncoated steel and single-additive systems. FESEM morphological analysis revealed a uniform, porous nanocomposite structure with well-dispersed nanoparticles and minimal post-exposure cracking, in contrast to the severe pitting observed in the uncoated specimens. Elemental mapping confirmed MgO-chitosan integration and limited chloride penetration. The synergy between MgO and chitosan validates this hybrid organic–inorganic coating as an effective corrosion mitigation strategy for steel in chloride based alkaline concrete environments.