Corrosion Protection of Carbon Steel by Self-Healing Epoxy Coating Based on Biocompatible Chitosan-NanoZrO₂ Hybrid Microcapsules

Nano-zirconium oxide particles were immobilized into chitosan via electrospraying technique to obtain organic-inorganic hybrid microcapsules (CZ) serving as self-healing anticorrosion materials for the enhancement of epoxy coating. Assessment of produced materials through adequate characterizations revealed hybrid microcapsules possessed spherical morphology with a mean size of 300 μm and thermal stability at 700^oC up to ~ 50%. Subsequently, CZ was incorporated into an epoxy coating matrix to develop a self-healing coating, CZP_x, for carbon steel protection. SEM and EIS analysis of scratched CZP_x coating at 14 days of immersion in a corrosive medium confirmed the self-healing and anticorrosion capabilities of the coating with the impedance at the coating-substrate interface increasing from 2.01 × 10⁶ to 1.22 × 10⁷ (ohm cm²) between the 7th to 14th day of immersion. The barrier property of CZP_x was determined through capacitance (CPEdl) to be higher than neat epoxy coating with a stronger impedance to the ingression of corrosion agents after the 14th day of immersion. Due to the unique feature of prepared CZ that allows their absorption of corrosion ions and formation of cross-linkages, self-healing was triggered upon the introduction of defects. The inhibitive nature of CZ provided superior anticorrosion properties to epoxy coating.