(1. 重庆理工大学 材料科学与工程学院，重庆 400054；
2. 重庆市特种焊接材料与技术高校工程研究中心，重庆 400054)
摘 要: 为改善镁合金的耐蚀性能，采用化学沉积法在AZ31镁合金表面制备了微-纳级别尺度CaF2/MgF2复合膜层，分析该复合膜层的形貌、成分及相结构。采用Hank’s仿生溶液中浸泡和电化学测试技术，结合浸泡过程中膜层EIS谱和表面形貌成分的变化，研究CaF2/MgF2复合膜层的体外降解行为。结果表明：该复合膜层外层为纳米尺度的片状CaF2 晶体，内层为致密的MgF2转化膜。CaF2膜层提高了单一氟转化层的自腐蚀电位φcorr和极化电阻Rp，浸泡13 d后其电荷转移电阻仍维持在1×104 Ω·cm2以上。试样在Hank’s溶液中浸泡7 d后CaF2膜层发生局部溶解；9 d后在CaF2层局部脱落处，Cl-渗透到MgF2膜层而发生点蚀。
关键字: 镁合金；CaF2/MgF2； 膜层；降解性能；生物材料
（1. School of Materials Science & Engineering, Chongqing University of Technology, Chongqing 400054, China;
2. Chongqing Municipal Engineering Research Center of Institutions of Higher Education for Special Welding Materials and Technology, Chongqing 400054, China）
Abstract:CaF2/MgF2 composite film was prepared on AZ31 magnesium alloy by chemical treatment to improve its corrosion resistance. The morphology and composition of the composite film were analyzed. The evolution of electrochemical impedance spectroscope (EIS) patterns and the change of the surface appearance and chemical composition of the composite film in Hank’s solutions were investigated to study the degradation process of film. The results show that the composite film consists of nanoscale flaky-like CaF2 crystals in out layer and compact MgF2 conversion film in inner layer. The corrosion potential φcorr and polarization resistance Rp of the fluorine conversion layer are improved by the CaF2 film. And the Rct of the composite coating after 13 d immersion in Hank’s solution is still above 1×104 Ω·cm2. CaF2 dissolves partially and adsorbs some of phosphate ions after 7 d immersion in Hank’s solution. After 9 d immersion, pitting corrosions occur because of the partial exfoliation of CaF2 film and the infiltration of Cl- into the MgF2 film.
Key words: magnesium alloy; CaF2/MgF2; coating; degradation behavior; biomaterial
