溶液温度对医用Mg-Li-Ca合金表面锌钙系磷酸盐转化膜耐蚀性能的影响(英文)

Influence of solution temperature on corrosion resistance of Zn-Ca phosphate conversion coating on biomedical Mg-Li-Ca alloys

考察不同磷化液温度对Mg-Li-Ca合金表面锌钙磷酸盐转化膜质量和耐蚀性能的影响。利用扫描电子显微镜、电子探针、能谱仪、X射线衍射和傅里叶红外光谱研究转化膜的表面形貌、化学成分和物相，采用析氢腐蚀实验和动电位电化学技术以及电化学阻抗研究磷化液温度对 Mg-Li-Ca 合金表面磷酸盐转化膜耐蚀性能的影响。结果表明：当溶液温度低于45℃时，膜层主要由Zn和ZnO组成，而当温度高于50℃时，膜层的主要相为Zn3（PO4）2·4H2O、少量的Zn和ZnO；在55℃温度下制备的磷酸盐转化膜的耐蚀性能最好；在40~50℃下制备的膜，由于镁基体与锌之间形成的电偶腐蚀而加快了其析氢速率。

The influence of phosphating bath at different temperatures on the formation and corrosion property of calcium-modified zinc phosphate conversion coating （Zn-Ca-P coating） on Mg-Li-Ca alloy was investigated. The morphologies, elemental distribution and chemical structures of the coatings were examined via SEM, EPMA, EDS, XRD and FT-IR. The corrosion resistance was assessed by hydrogen evolution, potentiodynamic polarization and EIS. The results show that the coating is composed of single element Zn and ZnO at below 45 ℃;whereas the coatings are predominantly characterized by Zn3（PO4）2·4H2O and small amount of element zinc and ZnO at above 50 ℃. Mg-Li-Ca alloy with Zn-Ca-P coatings prepared at 55 ℃ has the highest corrosion resistance. However, the hydrogen evolution rates of the coatings obtained at 40-50 ℃ is accelerated due to the galvanic corrosion between the imperfection of the single element Zn coating and the Mg substrate.