Biohybrid microcapsules based on electrosprayed CS-immobilized nanoZrV for self-healing epoxy coating development

In this work, zirconium vanadate nanoparticles were immobilized into chitosan using a facile electrospraying technique to produce CS-ZrV hybrid microcapsules for the development of a self-healing coating. Upon assessment, hybrid microcapsules possessed desirable properties with a mean particle size of 319 μm, maintaining good thermal stability of ∼55% at 700 °C, and were subsequently incorporated into an epoxy resin to develop a biocompatible self-healing coating, CZVEx, for carbon steel corrosion protection. Scratched samples of self-healing and control coatings were analyzed in a corrosion medium of 3.5 wt% aqueous NaCl. SEM images of the scratched coating sample, after days of immersion, revealed healing of defects through the appearance of an epoxide gel-like substance due to the release of polymeric vanadate that reacted with corrosion agents, resulting in polymerization of vanadium hydrates and subsequent self-healing, validated by the proposed mechanism of self-healing. Electrochemical impedance spectroscopy analysis further confirmed CZVEx coating possessed excellent self-healing capabilities through a significant impedance rise from 4.48 × 10⁵ to 5.52 × 10⁵ (ohm cm²) between the 7th and 14th day of immersion. Furthermore, comparative polarization assessment of coating samples with/without defects indicated the accuracy of EIS for self-healing analysis, and showed the sample with no defect was only 2.6 times more corrosion resistant than the scratched coating, as against bare steel substrate that was 22 times less resistant, revealing superior self-healing anticorrosion properties of the coating.