Optimizing Electrochemical Deposition for Biodegradable Zinc-Hydroxyapatite Systems in Bone Repair

Biodegradable metals are gradually gaining increased attention as a new option for complementary treatment alongside standard inert metal implants. While magnesium- and iron-based systems have been extensively studied, zinc has recently emerged as a novel candidate due to its moderate degradation rate and essential biological role. However, the use of pure zinc in biomedical applications is limited by its potential cytotoxicity. A widely adopted strategy to overcome these drawbacks involves surface modification with bioactive ceramic coatings, particularly hydroxyapatite (HAp), to promote bone-material integration. In this study, we report a systematic use of electrochemical deposition (ECD) for the fabrication of hydroxyapatite coatings on zinc substrates. This method allows us to precisely tailor the coating morphology and properties under controlled electrochemical conditions, offering a scalable, low-temperature alternative to other deposition techniques. Key deposition parameters including applied current density, deposition time, and the presence of a chelating agent (EDTA-2Na) were optimized to achieve uniform, adherent, and morphologically favorable HAp layers. The optimal conditions (current density of 1.25 mA/cm², deposition time of 120 min, and EDTA-2Na addition) yielded coatings with strong adhesion to the zinc substrate and beneficial HAp morphology for cell-attachment. The ceramic layer not only improved the mechanical stability of the composite system but also reduced the degradation rate in simulated body fluids. Furthermore, the HAp-coated zinc surface did not exhibit any signs of thrombogenicity, suggesting good hemocompatibility.