Due to its biodegradability, Mg has recently been chosen as a potential temporary load bearing implant material. However the corrosion resistance of Mg must be improved to control its degradation rate matching with the bone healing process. One way to solve the issue is to deposit another bioactive and biocompatible hydroxyapatite (HA) coating on Mg implant via electrodeposition. With this motivation, the current paper explores how the current density, a crucial process parameter, influences the formation, characteristics and degradation of HA-coating. Electrodeposition at three different current densities (3, 6 and 13 mA/cm²) was performed on AZ31B Mg substrate followed by an alkali treatment to ensure the complete HA deposition. Surface morphology, chemical composition, crystallinity and texture of the coating were evaluated, followed by potentiodynamic corrosion tests to assess the degradation resistance of the coated samples. Characterisation results show that low current density of 3 mA/cm² results in a compact, dense and uniform coating layer as compared to 6 and 13 mA/cm². Accelerated H₂ gas evolution at Mg cathode and faster deposition at higher current density (of 13 mA/cm²) would cause the lack of integration and bonding of crystals, thus resulting in relatively porous, inhomogeneous and rough HA coating. HA coating deposited at low current density is shown to exhibit the best corrosion protection compared to those at higher current density. The findings clearly indicate that the integrity of the coating layer is a crucial quality indicator. Higher current density can produce the coating thickness of as high as 50 μm with appropriate application of the current density followed by alkaline treatment. It is also demonstrated that the electrodeposition could be a promising viable method to fabricate HA-coated AZ31B implants with better and prolonged corrosion protection.

由于其生物可降解性，Mg最近被选作潜在的临时负重植入材料。但是，必须提高镁的耐腐蚀性，以控制其降解速率与骨骼愈合过程相匹配。解决该问题的一种方法是通过电沉积在Mg植入物上沉积另一种具有生物活性和生物相容性的羟基磷灰石（HA）涂层。以此动机为基础，本文探讨了电流密度（一个关键的工艺参数）如何影响HA涂层的形成，特性和降解。三种不同电流密度（3、6和13 mA / cm ^2的电沉积在AZ31B镁基底上进行）处理，然后进行碱处理以确保HA完全沉积。评估了涂层的表面形态，化学组成，结晶度和织构，然后进行了电位动力学腐蚀测试，以评估涂层样品的耐降解性。表征结果表明，与6和13 mA / cm ²相比，3 mA / cm ^2的低电流密度可形成致密，致密且均匀的涂层。在Mg阴极加速H ₂气体逸出，并在更高的电流密度（13 mA / cm ^2的电流）下更快地沉积）将导致缺乏晶体的整合和结合，从而导致相对多孔，不均匀且粗糙的HA涂层。与高电流密度下的HA涂层相比，低电流密度下的HA涂层表现出最佳的腐蚀防护性能。这些发现清楚地表明，涂层的完整性是至关重要的质量指标。在适当施加电流密度后再进行碱处理，较高的电流密度可产生高达50μm的涂层厚度。还证明了电沉积可能是一种有前途的可行方法，可用于制造具有更好且延长的腐蚀防护的HA涂层的AZ31B植入物。