可降解血管支架用Mg-4.0Zn-0.2Mn-0.2Ca微细管的体外降解行为

通过浸泡实验和电化学测试研究了Mg-4.0Zn-0.2Mn-0.2Ca（质量分数）微细管的体外降解行为与腐蚀机理。结果表明，退火处理可以提高微细管的耐腐蚀性。长期浸泡实验表明腐蚀过程相对均匀，退火微细管在Hank''s溶液中的腐蚀速率约为0.30 mm/a。在浸泡初期，退火管材表面生成Mg(OH)₂，形成保护膜，阻碍腐蚀进行。虽然Mg(OH)₂膜上形成的羟基磷灰石（HA）可以进一步降低腐蚀速率，但是镁基体中粗大的第二相会增强电偶腐蚀效应，并且生成的大量氢气，从而破坏HA膜，使腐蚀继续进行。

In-vitro Degradation Behavior of Mg-4.0Zn-0.2Mn-0.2Ca Micro-tube for Biodegradable Vascular Stent

The in-vitro degradation behavior and corrosion mechanism of Mg-4.0Zn-0.2Mn-0.2Ca (wt%) micro-tube was investigated by the immersion tests and electrochemical tests. The results show that the corrosion resistance of the micro-tubes can be improved by the annealing treatment. The long-term immersion tests reveal that the corrosion process is relatively uniform, and the corrosion rate of the annealed micro-tube in Hank''s solution is about 0.30 mm/a. During the initial stage of immersion, Mg(OH)₂ is formed on the surface of the annealed micro-tubes, forming a protective film to hinder the corrosion progress. Although the formed hydroxyapatite (HA) on Mg(OH)₂ film can further reduce the corrosion rate, the coarse secondary phases in Mg matrix can enhance the galvanic corrosion effect. The generated abundant hydrogen may destroy the HA film, thus promoting the corrosion process.