Mg-based metallic glasses show attractive properties making it as potential materials for implants in biomedical applications, especially compared to traditional crystalline Mg alloys. In this study, the corrosion behavior of melt-spun glassy Mg67Zn28Ca5 ribbons before and after heat treatment at different temperatures was systematically investigated in simulated body fluid. Electrochemical tests and the rate of hydrogen evolution indicated that the corrosion behavior strongly depended on the structure of ribbons. The slowest corrosion rate (strongest corrosion resistance) was achieved for the ribbon with a partially crystallized structure (metastable crystalline Mg102.08Zn39.6 and amorphous matrix). Surface morphology analysis revealed that amorphous ribbons were more susceptible to pitting corrosion than the corresponding partially and fully crystallized ribbons. A Zn-rich passivation layer was detected on the surface of ribbons after immersion test, indicating the corrosion was mainly caused by the loss of Mg- and Ca-containing components, resulting in the enrichment of metallic Zn with improved corrosion resistance as the outcome. (c) 2012 Elsevier B.V. All rights reserved.