Design of 8HQ@ZIF-8/PDA smart nanocontainers via host-guest nanoconfinement and surface self-assembly for enhanced corrosion protection and self-healing of magnesium alloy epoxy composite coatings

Abstract

Conventional nanoparticles incorporated into epoxy coatings suffer from poor compatibility and insufficient corrosion improvement, hindering their practical applications. A dual-strategy approach integrating in-situ host–guest nanoconfinement and surface self-assembly was devised to fabricate 8HQ@ZIF-8/PDA smart nanocontainers. The guest 8-hydroxyquinoline (8HQ) was encapsulated within the zeolitic imidazolate framework-8 (ZIF-8) host, leveraging nanoconfinement effects. A bioinspired polydopamine (PDA) layer was then self-assembled on the 8HQ@ZIF-8 surface through dopamine oxidative self-polymerization, resulting in a robust nanocontainer architecture. Density functional theory (DFT) calculations verify that the molecular interactions between the PDA and the ZIF-8 surface was the chemical adsorption. The resultant 8HQ@ZIF-8/PDA retained the rhombic dodecahedral morphology and crystallinity of ZIF-8, demonstrating controlled pH-responsive release behavior. When incorporated into an epoxy (EP) resin matrix on magnesium alloy, the 8HQ@ZIF-8/PDA/EP smart composite coatings exhibited outstanding interfacial compatibility and long-term stability, achieving a low-frequency impedance (|Z|₀.₀₁_Hz) of 2.49 × 10⁷ Ω cm², a maximum phase angle of 82.8°, and a breakpoint frequency (f_b) of 63.34 Hz after 50 days of immersion in a 3.5 wt% NaCl solution. These findings highlight the exceptional self-healing and corrosion-resistant properties of the 8HQ@ZIF-8/PDA/EP smart composite coatings, underscoring its potential for protecting magnesium alloys in aggressive environments.