Synergistic active-passive corrosion protection of steel by a pH-responsive CeO2@ZrP epoxy coating enabled by interfacial engineering

To overcome the critical limitation of conventional epoxy coatings in providing long-term barrier effect against corrosion species and on-demand corrosion inhibition at damaged sites, this study develops a self-protective CeO 2 @ZrP/EP composites coating via in-situ hydrothermal growth of pH-responsive CeO 2 nanoparticles on lamellar α-ZrP nanosheets. The hydroxyl-rich CeO 2 nanoparticles not only enhance interfacial compatibility by filling voids and creating mechanical interlocking between α-ZrP nanosheets and the epoxy matrix, but also enable pH-triggered Ce 3+/4+ release under acidic condition. After 60 days immersion, the composite coating achieved a low-frequency impedance modulus (|Z| 0.01Hz ) of 3.5 × 10 9  Ω·cm 2 , which is four orders of magnitude higher than pure EP coating (3.7 × 10 5  Ω·cm 2 ). Crucially, elemental mapping confirmed 2.0 wt% cerium enrichment at artificial scratches, demonstrating autonomous active inhibition. This dual-action strategy synergistically integrates durable barrier protection with intelligent corrosion inhibition, providing long-term steel protection in marine environments.