Fabrication and performance of PES/Al composite corrosion-resistant coating based on labyrinth effect structure

To enhance the service lifetime of metallic substrates, a novel organic–inorganic composite coating was developed by constructing a PES matrix incorporated with aluminum powder as functional filler. The anti-corrosion mechanism was achieved through the formation of a “labyrinthine” structure that significantly prolongs the diffusion pathway and time required for corrosive agents to reach the substrate interface. The PES/Al composite coating exhibits superior mechanical properties and well-organized microstructure, demonstrating remarkable corrosion resistance improvement. In addition, a systematic investigation was conducted to elucidate the influence of Al particle size and loading content on the coating’s performance characteristics. • The preparation process for the novel composite coating is simple and highly efficient. • The coating had excellent mechanical properties, good micro-morphology and outstanding corrosion resistance. • The electrochemical impedance was increased more than 160%, by the labyrinthine effect on the structural configuration. • The coating exhibited excellent ability even under special environment, which has broad application potential. Organic-inorganic composite coatings have consistently garnered significant attention in corrosion protection research due to their exceptional anti-corrosion capabilities. In this study, a labyrinth-type composite coating was prepared by using the polyethersulfone (PES) as skeleton, combined with aluminum (Al) particles as functional fillers. The effects of varying proportions (0–20 wt%) and varying particle sizes (6–15 μm) of Al additives on coating performance were investigated. The mechanical properties of composite coating were assessed by adhesion strength via cross-cut test, pencil hardness, impact resistance, etc. The coating microstructure was examined through scanning electron microscopy (SEM). The electrochemical impedance spectroscopy (EIS), polarization test, cyclic salt spray testing, and solution immersion experiments in water, acid and alkaline. Experimental results demonstrate that the composite coating effectively filled micro-pores generated during PES film formation, simultaneously satisfying mechanical requirements and significantly enhancing corrosion resistance. The optimal proportion of Al powder for the coating is approximately 5 %. PES-7 could improve the electrochemical impedance by 2–3 orders of magnitude to 4.22 × 10 8 Ω cm 2 after 7 days, which is 162 % of the pure PES [lg(|Z|)], and could still maintain high protective ability after soaking in acidic and alkaline solution for 360 h. Meanwhile, the anti-corrosion mechanism and critical influencing factors of this composite coating have been investigated and elucidated.