Enhancement of calcium phosphate formation on zirconium by micro-arc oxidation and chemical treatments

Surface treatments with various combinations of micro-arc oxidation (MAO) and chemical treatments were performed on zirconium (Zr) disks in this study to enhance the bioactivity of Zr. The surface oxide layers formed with MAO and chemical treatments on Zr disks were characterized using surface analyses; the calcium phosphate formation on the specimens after immersion in Hanks' solution was evaluated. As a result, thick calcium phosphate layers formed on Zr specimens that underwent MAO treatment with a mixture of calcium glycerophosphate and magnesium acetate and subsequent chemical treatment with sulfuric acid or sodium hydroxide solutions, while no precipitate was observed without treatment. The surface analyses revealed that the porous oxide layer formed by MAO treatment contained Ca, P, and Mg, which were incorporated from the electrolytes during the treatments. In addition, both the composition and crystal structure of the oxide layers uniquely changed as a result of the various chemical treatments. ► Micro-arc oxidation allows Zr oxide layer incorporating with Ca, P, and Mg. ► The incorporated Mg does not inhibit calcium phosphate formation. ► The amount of incorporated elements can be controlled by chemical treatments. ► Bioactive oxide layer containing Mg can be achieved by this technique.