电解质
镁
材料科学
腐蚀
降级(电信)
电位滴定法
镁合金
磷酸盐
合金
化学工程
分析化学(期刊)
离子
电极
冶金
化学
色谱法
有机化学
工程类
物理化学
电信
计算机科学
作者
Sviatlana V. Lamaka,Jorge González,Di Mei,Frank Feyerabend,Regine Willumeit‐Römer,Mikhail L. Zheludkevich
标识
DOI:10.1002/admi.201800169
摘要
Abstract Many reports are available on degradation rates and corrosion product characterization of magnesium alloys for implant application. Typically, the data are obtained ex situ, as post factum analysis of occurred degradation processes or in bulk electrolyte that does not fully reflect concentration gradients at the interface and in the diffusion layer. Meanwhile, these local conditions are essential for tissue‐implant compatibility. Only a limited number of studies employ the techniques that visualize ongoing degradation and are localized enough to observe the changes in the electrolyte layer directly adjacent to corroding magnesium. Here, local pH in Hank's solution is studied in operando, with potentiometric micro‐probes (d = 2 µm) located 10–50 µm above the surface of four Mg alloys potentially relevant for implant applications. A significant difference in local pH is observed for Mg in simple Hank's solution (near surface pH 9.9–10.5) or Hank's solution modified with 2.5 × 10 −3 m Ca 2+ (pH 7.8–8.5). The corresponding pH values are established during the first seconds of immersion. These findings indicate different degradation kinetics in electrolytes with or without Ca 2+ . The degradation rate of Mg alloys decreases by almost two times in Ca 2+ containing Hank's solution. Calcium‐phosphate/carbonate protective layer stabilizes the surface pH below 8.5 controlling Mg degradation.
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