高腐蚀动力学和局部腐蚀进展是基于镁(Mg)的可植入装置的临床实施所引起的主要问题。在这项研究中,采用二元Mg-锂(Li)合金作为模型材料,旨在在模拟体液中产生均匀和缓慢的腐蚀行为,即最低必需培养基(MEM),与普通镁合金AZ31和生物相容性Mg-0.5Zn-0.5Ca对应物相比。扫描电子显微镜检查揭示了Mg-14Li(β-Li)的单相微观结构特征,而不溶性相的存在,阴极到α-Mg基体,在AZ31和Mg-0.5Zn-0.5Ca.尽管在短期时间范围内(不超过60分钟),所有试样的腐蚀动力学存在轻微差异,如电位动力学极化和电化学阻抗谱所示,在浸没测试方面,深刻的变化是显而易见的,即质量损失和析氢测量(长达7天)。横截面显微照片揭示了AZ31和Mg-0.5Zn-0.5Ca中的严重点蚀,但Mg-14Li的情况并非如此。X射线衍射图和X射线光电子能谱证实,在MEM中的Mg-14Li的表面上产生了由碳酸锂(Li2CO3)和氢氧化钙组成的致密膜(厚度为25μm),这大大有助于其低腐蚀速率。因此,建议单相结构以及保护性和无缺陷的Li2CO3膜的形成引起Mg-14Li在MEM中的受控和均匀的腐蚀行为,为生物可降解镁材料的探索提供新的见解。
High corrosion kinetics and localised corrosion progress are the primary concerns arising from the clinical implementation of magnesium (Mg) based implantable devices. In this study, a binary Mg-lithium (Li) alloy consisting a record high Li content of 14% (in weight) was employed as model material aiming to yield homogenous and slow corrosion behaviour in a simulated body fluid, i.e. minimum essential medium (
MEM), in comparison to that of generic Mg alloy AZ31 and biocompatible Mg-0.5Zn-0.5Ca counterparts. Scanning electron microscopy examination reveals single-phase microstructural characteristics of Mg-14Li (β-Li), whilst the presence of insoluble phases, cathodic to α-Mg matrix, in AZ31 and Mg-0.5Zn-0.5Ca. Though slight differences exist in the corrosion kinetics of all the specimens over a short-term time scale (no longer than 60 min), as indicated by potentiodynamic polarisation and electrochemical impedance spectroscopy, profound variations are apparent in terms of immersion tests, i.e. mass loss and hydrogen evolution measurements (up to 7 days). Cross-sectional micrographs unveil severe pitting corrosion in AZ31 and Mg-0.5Zn-0.5Ca, but not the case for Mg-14Li. X-ray diffraction patterns and X-ray photoelectron spectroscopy confirm that a compact film (25 μm in thickness) consisting of lithium carbonate (Li2CO3) and calcium hydroxide was generated on the surface of Mg-14Li in
MEM, which contributes greatly to its low corrosion rate. It is proposed therefore that the single-phase structure and formation of protective and defect-free Li2CO3 film give rise to the controlled and homogenous corrosion behaviour of Mg-14Li in
MEM, providing new insights for the exploration of biodegradable Mg materials.