Abstract:Mg-5Zn-0.3Ca/nHA biocomposites were prepared from pure Mg, Zn, Ca and nano-hydroxyapatite (nHA) powders by powder metallurgy method. The effect of various mass fractions of nHA (1%, 2.5%, 5%) as reinforcement on the corrosion properties of Mg-5Zn-0.3Ca alloy was investigated. The corrosion resistance of biocomposite samples was investigated by immersion tests and electrochemical techniques in SBF solution. The results showed that the corrosion resistance of Mg alloy was improved by adding 1% and 2.5% nHA. Bioactive nHA motivated the formation of stable phosphate and carbonate layers on surface and improved corrosion resistance of nanocomposites. However, addition of large contents of nHA in Mg alloy as reinforcement increased the density of this precipitated layer, so gases produced from localized corrosion were accumulated underneath this layer and decreased its adhesiveness and lowered its corrosion resistance. Indirect cytotoxicity evaluation for Mg alloy and its nanocomposites also showed that their extraction was not toxic and nanocomposite with 1% nHA indicated almost similar behavior as negative control.

Key words: powder metallurgy; metal biocomposite; corrosion; magnesium