The effects of Zn on microstructure and bio-corrosion of biodegradable Mg-1.38 Si alloy were investigated. The results show that Zn has preferable modification effect on Mg

2

Si phase in as-cast Mg-1.38 Si alloy. The morphology of primary Mg

2

Si phase is converted from polyhedral to finely particle-like and the eutectic Mg

2

Si phase is refined after Zn addition. With the increase of Zn contents

the amount of Mg

2

Si phase is further decreased

and the corrosion rate and corrosion current density of the alloy are gradually decreased

while the corrosion potential of the alloy is gradually moved towards positive direction

indicating the enhancement of corrosion resistance. When the Zn content is 1.5%

the corrosion resistance of the alloy presents desirable.