Functionalized ZIF-8@ZrP nanohybrid for corrosion- and weathering-resistance epoxy composite coating: Critical role of polyaspartic acid

To overcome the inherent limitations of epoxy (EP) coatings in terms of barrier performance, active protection, and weathering resistance, this work presents a multifunctional composite strategy based on hierarchically engineered nanohybrids. Polyaspartic acid (PASP), in coordination with Ca 2+ , was co-functionalized on zeolitic imidazolate framework-8 (ZIF-8) nanoparticles that were in-situ grown on α-ZrP platforms. The resulting PASP-Ca@ZIF-8/ZrP nanohybrids exhibited excellent dispersibility and interfacial compatibility within EP matrix, enabling the fabrication of an advanced PCZZ/EP coating with robust mechanical properties (adhesion strength of 6.7 MPa and tensile strength of 52.3 MPa) and an exceptional barrier performance (| Z | 0.01Hz of 7.1 × 10 10  Ω·cm 2 after 90 days of immersion in 3.5 % NaCl solution). The nanohybrids endowed the coating with pH-responsive release of inhibitory species (PASP, Ca 2+ , Zn 2+ , and 2-MI) imparting a dynamic self-repairing function that effectively mitigated localized corrosion, as validated by salt spray and filiform corrosion tests. During 144 h of accelerated UV exposure, the | Z | 0.01Hz value of PCZZ/EP coating retain over 1 × 10 8  Ω·cm 2 , demonstrating its excellent weathering-resistance. Molecular dynamics simulations further revealed the highest crosslinking density (96 %) and the lowest Cl − diffusion coefficient (0.0159 cm 2 /s) of PCZZ/EP model, indicating a dense internal network that restricted ion transport. This work establishes a scalable and versatile design framework for developing high-performance smart epoxy coatings, offering both mechanistic insight and practical solutions for the long-term protection of steel infrastructures in severe marine and industrial environments.