AZ31镁合金表面钙磷涂层在Hank′s液中的腐蚀行为

Corrosion Behavior of AZ31 Magnesium Alloy with Calcium Phosphate Coating in Hank′s Solution

采用电化学沉积法在AZ31镁合金表面制备了钙磷涂层,采用X射线衍射仪和三维显微镜分析了涂层的相组成和形貌,采用析氢试验和动电位扫描技术研究了AZ31镁合金和钙磷涂层在Hank′s液中的腐蚀行为。结果表明,电化学沉积法在AZ31镁合金基体上制备了均匀的透钙磷石(CaHPO4·2H2O)片状晶体。该钙磷涂层能有效地降低AZ31镁合金基体在Hank′s液中浸泡初期的腐蚀速率,自腐蚀电流密度较AZ31镁合金下降两个数量级;随着涂层的不均匀溶解,AZ31基体发生明显的局部腐蚀,出现半径约200μm,深度近500μm的腐蚀坑。残余涂层和基体间未出现明显的电偶腐蚀效应。

A calcium phosphate coating was fabricated on AZ31 magnesium alloy surface by electrochemical deposition method.The morphology and structure of the coating were analyzed by three-dimensional digital microscope and X-ray diffractometer.The corrosion behaviors of AZ31 magnesium alloy and calcium phosphate coating in Hank′s solution were investigated by the hydrogen evolution testing and the potentiodynamic scan technique.The results showed that the deposited coating predominately consists of flake-shape brushite(CaHPO4· 2H2O)crystallites.The coating can decrease the corrosion rate of AZ31substrate immersing stage in Hank′s solution.At the initial stage,the corrosion current density decreased 2orders of magnitude.With the degradation of the coating,the protectivity of the coating decreased and obvious localized corrosion occured on the sample surface.