Investigation of the Microstructure and Bio-corrosion Behaviour of Mg-Zn and Mg-Zn-Ca Alloys

Biomedical applications of magnesium alloys have attracted increasing attention due to their unique combination of advantages. However, the poor corrosion resistance is an obstacle to magnesium alloys being used as biodegradable materials. As zinc (Zn) and calcium (Ca) are nontoxic and recognized as nutritionally essential elements in the human body, in this study Zn and Ca were selected as alloying elements to produce suitable bio-corrosion properties. The grain size was reduced significantly from 141.4 mu m to 97.3 mu m by adding Ca. The bio-corrosion performance of the two alloys (Mg-3Zn and Mg-3Zn-0.3Ca) was characterized using immersion tests in simulated body fluid at 37 degrees C. The alloys were dominated by pitting corrosion. Heat treatment was used to alter the microstructure and influence further the corrosion rate. The correlation between microstructure and bio-corrosion rate was evaluated, in the light of the alloying elements and the heat treatment employed.