Multiscale investigation of corrosion resistance-bioactivity synergistic mechanism in ZnO-CaSiO₃/GO/h-BN composite coatings

This study investigates the corrosion resistance mechanisms, bioactivity, and antibacterial properties of ZnO-CaSiO₃/GO/h-BN composite coatings through a combination of experiments and molecular dynamics (MD) simulations. Electrochemical tests revealed that the T2 coating exhibited optimal corrosion protection, characterized by the highest corrosion potential (−0.005 V) and the lowest corrosion current density (9.617 × 10⁻⁹ A·cm⁻²). Correspondingly, the T2 coating showed the highest resistance (8.62 × 10⁵ Ω·cm²) and significant charge transfer resistance (2.84 × 10⁷ Ω·cm²), maintaining the best anti-corrosion performance even after 14 days of immersion in SBF. MD simulations indicated that the h-BN/GO sheets, combined with uniformly distributed nanoparticles, create a dense coating structure through a “maze effect” that effectively inhibits the diffusion of corrosive species. Although hydrogen bonding improved filler dispersion, excessive ZnO reduced coating stability due to poor interfacial compatibility. Cell viability assays demonstrated that the T2 coating promotes cell activity (with a cell survival rate of 80.7 %), benefiting from the biomimetic mineralized environment provided by CaSiO₃ and the enhanced cellular function facilitated by appropriate Zn²⁺ release. However, excessive Zn²⁺ induced cytotoxicity, indicating a biphasic concentration-dependent regulation of bioactivity. Antibacterial tests confirmed that the T2 and T3 coatings, owing to their higher ZnO content, possess remarkable antibacterial capability. In summary, considering the core requirements for biomedical applications, the T2 composite coating demonstrates promising potential for use in titanium alloy orthopedic implants.