Methods: Specimens of polished AZ31 magnesium alloy (diameter 15 mm, thickness ~5 mm) were used. The acid calcium phosphate electrolyte solution (pH 3) was prepared by dissolving calcium phosphate in an aqueous solution of phosphoric acid at room temperature. Electrodes, the specimen and Pt plate, were connected to the negative and positive poles of a DC power source, respectively. The distance between the electrodes was 1 mm. Electrolysis was carried out in the solution (10 mL) at a constant voltage of 20 VDC for 600 s. The electrolytic current and the temperature of the electrolyte bath were measured every 10 s with a digital multi-meter. The deposited materials were morphologically analyzed by means of AFM and were characterized by FTIR and powder XRD.
Results: Average of current was 0.4 A and the maximum bath temperature was 80°C. Based on XRD and FTIR results, Ca-deficient hydroxyapatite (HAp) was confirmed. Moreover, some calcium hydroxide was observed. AFM image showed that the surface consisted of both many square rods with length of less than 0.3 μm and spherical or elliptical particles with the size of around 0.1 μm.
Conclusions: Ca-deficient HAp was deposited on AZ31 surface by the electrolytic treatment. This result suggested a simple and effective method for preparing a biocompatible AZ31 magnesium alloy surface.