Polydopamine-coated zeolitic imidazolate framework for enhanced anti-corrosion and self-healing capabilities of epoxy coating on magnesium alloy

[Display omitted] •ZIF-8@PDA smart nanocapsules, 250–350 nm in size, were fabricated.•The nanocapsules in epoxy resin enhanced anti-corrosion and self-healing properties.•Incorporating 1.0 wt% nanocapsules showed the optimal comprehensive properties. This study lies in the first-time incorporation of polydopamine (PDA)-modified zeolitic imidazolate framework-8 (ZIF-8) smart nanocapsules (ZIF-8@PDA) with epoxy resin, systematically improving the comprehensive performance of magnesium alloy coatings and proposing a novel anti-corrosion mechanism based on physical barrier and dual self-healing characteristics. The PDA coating formed on the ZIF-8 surface creates a uniform, dense, and relatively impermeable barrier layer, which enhances the stability of ZIF-8 within the coating matrix. Electrochemical impedance spectroscopy (EIS) tests demonstrate that while the overall electrochemical impedance of the pure epoxy coating decreases, the ZIF-8@PDA1.0wt%/EP coating exhibits a significant increase in impedance between 10–12 h after being scratched, indicating remarkable self-healing capabilities. After 50 days of immersion in a 3.5 % NaCl solution, the low-frequency impedance value (|Z|0.01 Hz) of the pure epoxy coating rapidly declines to 0.15 MΩ·cm2, whereas the ZIF-8@PDA1.0wt%/EP sample shows a much smaller decrease, maintaining an impedance of 50 MΩ·cm2, and the charge transfer resistance (Rct) of the ZIF-8@PDA1.0wt%/EP coating is three orders of magnitude higher than that of pure EP coating, underscoring the exceptional corrosion inhibition performance. This study introduces a groundbreaking approach to developing smart epoxy coatings with superior corrosion resistance for magnesium alloys.