Objectives:

The aim of this study is to evaluate the effect of pH treatment on the formation of hydroxyapatite (HA) coating layer and the biodegradation rate of hydroxyapatite coated AZ31 alloy for applications in biodegradable implants.

Methods:

HA was grown on the surface of AZ31 substrate at three different pH solutions of 7.5, 9.0, and 10.5 respectively by chemical solution treatment method. The coated samples were evaluated their biodegradation behavior by immersion test in the simulated body fluid (SBF) for 14 days. The biodegradation rate of the samples during immersion test was observed by Mg²⁺ ion quantification method and measuring the increase of pH of the medium.

Results:

HA coatings were successfully grown on the AZ31 substrate at three different pH conditions. The sample coated at pH 7.5 showed its uniform and dense coating layer resulted in highest corrosion resistance. While the highest biodegradation rate was observed for the sample coated at pH 10.5 due to many micro-cracks formed in the HA layer. After 14 days of immersion, Mg(OH)₂ and calcium phosphate were corrosion products on the surface of the specimens coated at pH 10.5 and pH 9.0 respectively. While HA almost remained on the surface of sample coated at pH 7.5.

Conclusion:

AZ31 alloy coated with HA at pH 7.5 has lowest biodegradation rate and become suitable for applications in biodegradable implants.

中文翻译：

---

不同pH值处理的可生物降解羟基磷灰石涂层AZ31合金的体外生物降解行为

目标：

本研究的目的是评估 pH 处理对羟基磷灰石 (HA) 涂层形成的影响以及羟基磷灰石涂层 AZ31 合金在可生物降解植入物中的应用。

方法：

采用化学溶液处理方法，在 AZ31 基板表面分别生长 7.5、9.0 和 10.5 三种不同 pH 值的 HA。通过在模拟体液 (SBF) 中浸泡测试 14 天，评估涂层样品的生物降解行为。^{采用Mg 2+}离子定量法观察浸没试验中样品的生物降解率，并测量介质pH值的升高情况。

结果：

HA 涂层在三种不同的 pH 条件下成功地在 AZ31 基材上生长。pH 值为 7.5 的样品显示其均匀致密的涂层导致最高的耐腐蚀性。由于在 HA 层中形成了许多微裂纹，因此在 pH 值为 10.5 的样品中观察到最高的生物降解率。浸泡 14 天后，Mg(OH) ₂和磷酸钙分别在 pH 10.5 和 pH 9.0 涂层的试样表面形成腐蚀产物。而 HA 几乎保留在 pH 值为 7.5 的样品表面。

结论：

AZ31 合金在 pH 7.5 时涂有 HA，具有最低的生物降解率，适合用于可生物降解的植入物。