In order to improve the corrosion resistance and biocompatibility of magnesium alloys, MgF2/HA composite coatings were prepared on AZ31 magnesium alloy by way of chemical treatment and electrochemical deposition. The evolution of electrochemical impedance spectroscopy (EIS) behavior, as well as the change of the micrograph and chemical composition of the MgF2/HA coating in Hank's solutions were used to study the degradation process. The results indicate that, during the immersion in Hank's solutions,the capacitance loop at high frequency decreases obviously, the resistance of the composite coating reduces. The existence of inductance loop of the 5 d-soaked specimen indicates the nucleation of corrosion pits is formed on coated AZ31 alloy. Soak to 8 d, the pitting corrosion occurs, the corrosion products accumulate and form swelling prominence.Soak to 12 d,the Cl- permeates to substrate and MgCl2 crystals form on the coating surface. During the soaking, the surface coating does not fall off and the coating has not obvious dissolved. The degradation happens when the ions in solution permeate to the Mg substrate, and then the localized pitting corrosion occurs.%为改善镁合金的耐蚀性和生物相容性,利用化学处理和电化学沉积法在镁合金AZ31表面制备MgF2/HA复合涂层.采用Hank's仿生溶液中浸泡和电化学阻抗(EIS)的方法,结合浸泡过程中涂层EIS谱和表面形貌成分的变化,研究MgF2/HA涂层的体外降解行为.结果表明:在Hank's仿生溶液浸泡过程中,涂层电化学阻抗谱的高频容抗弧明显减小,涂层电阻随浸泡时间而降低.浸泡至5 d时,出现感抗弧,涂层表面区域产生腐蚀孔核.浸泡至8 d时,镁合金基体发生点蚀,点蚀产生的腐蚀产物在孔中堆积形成胞状突起.浸泡至12 d时,Cl-渗透至镁合金基体,涂层表面形成MgCl2结晶.浸泡过程中,表面涂层未发生脱落和明显的溶解,降解以溶液渗透至基体,然后发生局部点蚀为主.
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