Corrosion Behavior in Hank's Solution of a Magnesium–Hydroxyapatite Composite Processed by High‐Pressure Torsion

It is known that magnesium (Mg)-hydroxyapatite (HA) composites can be produced by the room temperature consolidation of particles. The present study analyzes the corrosion behavior of an Mg-HA composite and makes a direct comparison with pure Mg. Samples of Mg-HA and of pure Mg were immersed in Hank`s solution for up to 60 hours and the microstructure and corrosion products were characterized by scanning and transmission electron microscopy and X-ray diffraction. Electrochemical tests were used to evaluate the corrosion behavior and a hydrogen evolution test was undertaken to determine the corrosion rate. The results show the corrosion rate of the Mg-HA composite is higher than for pure Mg but decreases significantly after ~10 hours of immersion in Hank`s solution. The increase in corrosion resistance of the composite is attributed to the formation of a protective layer of corrosion products with an external surface layer rich in Ca, P and O.