Mg-5Ca-xZn alloys were prepared using various zinc contents from 1 to 5 wt% for use as degradable biomaterials in medical implant applications. The influence of zinc on the corrosion properties of Mg-5Ca alloys prepared in Hanks' solution was examined using electrochemical and surface analysis techniques. The electrochemical tests reveal that the addition of zinc improves the corrosion resistance of Mg-5Ca alloys compared with untreated alloys. The improved corrosion resistance is attributed to the increased refinement of the precipitates, the grain refinement, and the continuous precipitation of Mg-Ca and MgCaZn compounds as a corrosion barrier. (C) 2015 The Electrochemical Society. All rights reserved.