silicon-doped hydroxyapatite coatings on ti-6al-4v: enhanced corrosion protection for biomedical implants with sustainable materials design and resource-efficient engineering

Co-substituted bioactive coatings have gained increasing attention for improving the biological and physicochemical performance of metallic implants. hydroxyapatite (hap), a hexagonal and thermodynamically stable bioceramic, is widely used as a protective and osteoconductive surface layer. in this study, pure hap and silicon-modified hap coatings were deposited on ti-6al-4v substrates using a spin-coating technique. structural and morphological features of the films were analyzed using xrd, ftir, and fesem. the pure hap coatings displayed microcracks and voids, which can compromise the mechanical stability and long-term functionality of implants. electrochemical impedance spectroscopy (eis) was performed in simulated body fluid (sbf) to examine corrosion resistance. both coatings provided substantially higher corrosion stability than the uncoated alloy, confirming the protective benefits of surface modification. incorporation of silicon into the hap lattice refined the nanoparticle size from 29.87 nm to 23.41 nm, indicating enhanced nucleation and structural densification. nyquist analyses further revealed that the si-doped hap coating achieved the highest charge-transfer resistance (rct = 494.39 kω×cm2), compared to only 66.69 kω×cm2 for bare ti-6al-4v, demonstrating its superior barrier properties. overall, the findings show that si4+-substituted hap coating significantly improves the structural integrity, corrosion resistance, and functional performance of ti-6al-4v substrates. this approach presents a promising and sustainable surface-engineering strategy that not only advances biomedical implant development but also aligns with environmentally conscious material design and responsible resource management.