Electrophoretic deposition of hydroxyapatite coating on biodegradable Mg-4Zn-4Sn-0.6Ca-0.5Mn alloy

Aluminium-free Mg-4Zn-4Sn-0.6Ca-0.5Mn alloys, with similar mechanical properties to natural bone, were produced and used as substrates for electrophoretic deposition (EPD) of hydroxyapatite (HA) powder. HA powder was deposited at three levels of DC voltage (50, 100 and 150 V) at different times. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used for phase characterization. Cavities appeared in coated specimens with a coating thickness of more than 70 mu m and micro-cracks appeared in a coating thickness of more than 100 mu m. The maximum adhesion strength of coatings was 2.8 +/- 1.1 MPa for 150 V-5 s. Electrochemical impedance spectroscopy (EIS) test showed that coating resistance and charge transfer resistance increased in the coated samples of 100 V-5 s and 150 V-5 s, respectively.