Anti-corrosion and anti-scratch hybrid nanocomposite coatings containing zirconia microcapsules

Anti-corrosion and anti-scratch hybrid nanocomposite coatings were synthesized by incorporation zirconia-encapsulated chitosan microcapsules (CS–ZrO₂) into an epoxy resin matrix. The microcapsules were synthesized via a sol–gel method using zirconium (IV) chloride as a precursor, followed by characterization through FTIR, SEM, and EDX analyses to verify their chemical composition and morphology. SEM images indicated 1.5 wt% of filler as optimum for achieving uniform distribution into epoxy matrix. The pull-off adhesion measurements indicated strong bonding between the epoxy matrix and steel surface. The optimal scratch resistance of 2800 g was recorded for the coating with 2.5 wt% zirconia microcapsules, whereas the neat epoxy coating exhibited only 600 g resistance. The optimized formulation containing 2.5 wt% of CS–ZrO₂ microcapsules exhibited superior corrosion protection, scratch results, and interfacial adhesion compared to the neat epoxy film. Salt spray exposure and electrochemical impedance spectroscopy confirmed long-term protective stability, highlighting the potential of chitosan–zirconia hybrid systems for next-generation corrosion-resistant coatings. Nyquist and Bode plots obtained from electrochemical impedance spectroscopy (EIS) were employed to evaluate the electrochemical behavior and resistance of the samples. The results indicate that the sample without microcapsules exhibits the lowest resistance, as evidenced by the smaller Nyquist semicircle diameter. In contrast, samples containing 1.5 wt% of microcapsules show significantly higher resistance, maintaining values of approximately 6 kΩ even after 21 days. This enhanced resistance is attributed to the protective effect of the microcapsules, which effectively limit current flow through the material.