2，形成保護(hù)膜，阻礙腐蝕進(jìn)行。雖然Mg(OH)2膜上形成的羥基磷灰石（HA）可以進(jìn)一步降低腐蝕速率，但是鎂基體中粗大的第二相會增強(qiáng)電偶腐蝕效應(yīng)，并且生成的大量氫氣，從而破壞HA膜，使腐蝕繼續(xù)進(jìn)行。;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."/>