Durable self-healing coating system based on pH-responsive core-shell nanostructures

A critical access to high-efficiency anti-corrosion coatings is adding pH-responsive nanocontainers encapsulated with corrosion inhibitors into epoxy resin as it endows the composite coating with significant active long-term corrosion protection. Here, two self-healing coating systems (I-PBZ-EP and II-PBZ-EP) were constructed based on epoxy coating (EP) and benzotriazole-loaded zeolitic imidazolate framework (ZIF-8) encapsulated with polydopamine (PDA) by one-pot and two-pot methods, respectively. Electrochemical impedance spectroscopy (EIS) investigation shows that the low-frequency impedance modulus value (vertical bar Z vertical bar(0.01Hz)) of I-PBZ-EP still reaches 2.16 x 10(10) O center dot cm(2) which is the highest among all the coatings after 35 d of immersion. vertical bar Z vertical bar(0.01Hz) of the scratched I-PBZEP is 1.10 x 10(5) Omega center dot cm(2) after 13 h of immersion in 3.5 wt% NaCl solution, which far surpasses vertical bar Z vertical bar(0.01Hz) of the scratched II-PBZ-EP, exhibiting its excellent self-healing properties. This is because I-PBZ can release more benzotriazole (BTA) (22.5 mg/L and 13.4 mg/L) than II-PBZ (15.8 mg/L and 9.4 mg/L) under acidic and basic conditions to repair the micro-defects. In short, by changing the loading mode of corrosion inhibitors, I-PBZ-EP with a simpler synthesis method manages to provide the long-term anticorrosion protection for the carbon steel substrate.