Dynamic Polymer/Metal–Organic Framework Hybrid Microcapsules for Self-Healing Anticorrosion Coatings

Abstract

An ideal microcapsule effectively preserves an active substance and can rapidly release it to elicit a self-healing anticorrosion effect. However, the development of highly efficient microcapsules remains a challenge. In this study, polymer/metal–organic framework hybrid microcapsules with dynamic properties were constructed as self-healing anticorrosion coatings. The shell of the microcapsule consisted of flexible polydopamine and a hard crystalline zeolitic imidazolate framework-8 (ZIF-8) layer. The corrosion inhibitor 8-hydroxyquinoline (8-HQ) was trapped in the microcapsules and remained unreleased because the ZIF-8 layer acted as a molecular sieve. When the coating was surrounded by an acidic environment, the ZIF-8 nanocrystals in the shell dissociated, followed by the release of 8-HQ. A dense protective layer was formed on the steel surface to suppress extensive corrosion propagation. The |Z|_0.01Hz value of the self-healing coating increased from 1.9 × 10⁴ Ω cm² to 2.2 × 10⁶ Ω cm² within 48 h and remained at this level until 120 h post application. This value is 3 orders of magnitude higher than that of a pure epoxy coating under the same conditions. Compared with conventional coatings, the novel dynamic microcapsules enable the application of self-healing coatings that can withstand harsh acidic environments without human intervention.