Active corrosion protection of AA2024T3 by the synergy of flash-PEO/Ce coating and epoxy coating loaded with LDH/eco-friendly gluconate

Abstract

This study introduces an eco-friendly and energy-efficient bilayer coating system for long-term corrosion protection of AA2024 aluminium alloy. The system comprises a Ce (III)-based Flash Plasma Electrolytic Oxidation (PEO) layer and an epoxy topcoat loaded with gluconate-intercalated layered double hydroxides (LDHs). The PEO layer (∼6 μm thick) was synthesized under 100 s oxidation time using an Na₃(P₃O₆)₃-based electrolyte with Ce₂(SO₄)₃, achieving high energy efficiency (1.52 kWh·m−2·μm−1) while providing initial corrosion protection, immobilized cerium species for improved structural compactness and enhanced adhesion for post-modification with organic systems. To enable active corrosion resistance, gluconate-intercalated LDHs (2.5 %, 5 %, and 10 %) were incorporated into the epoxy topcoat, ensuring controlled inhibitor release while maintaining significant overall dry and wet adhesion properties. Structural analyses confirmed successful gluconate intercalation and release behaviour in NaCl solution, while electrochemical evaluation by impedance demonstrated superior long-term corrosion resistance through synergistic mechanisms: (i) the cerium-modified PEO layer enhanced stability of the PEO/epoxy interface, and (ii) the LDH-based epoxy layer provided active protection. This bilayer system exemplifies a sustainable, high-performance ecofriendly approach for corrosion mitigation, bridging energy-efficient PEO treatments with multifunctional organic coatings for demanding applications.