Electrodeposition of manganese substituted hydroxyapatite/zinc oxide duplex-layer on AZ91 magnesium alloy for orthopaedic applications

AZ91 Magnesium alloy (AZ91 Mg alloy) has been developed as a biodegradable implant material because of its outstanding biodegradability and mechanical properties. But the poor corrosion resistance of AZ91 Mg alloy in physiological solution limits its biomedical applications. In order to improve the corrosion resistance and biological performance of AZ91 Mg alloy, we have fabricated a manganese-subs tituted porous hydroxyapatite (Mn- HAP)/zinc oxide (ZnO) duplex layer on AZ91 Mg alloy by electrodeposi tion. The porous Mn-HAP/ZnO duplex-layer coating on AZ91 Mg alloy was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy and energy dispersive X-ray analysis (FESEM-EDAX). Also, the mechanical properties of the duplex-layer coatings were evaluated using adhesion and Vickers micro-hardness tests. The effects of the duplex-layer coating on the corrosion behavior of AZ91 Mg alloy were also investigated in simulated body fluid using electrochemical studies. The potentiodynamic polarization results indicated that the corrosion resistance of AZ91 Mg alloy was significantly improved by the duplex-layer coating. Hence, from the obtained results we believe that the duplex-layer made of ZnO together with porous Mn-HAP on AZ91 Mg alloy could provide effective corrosion protection and enhanced bioactivity. Thus, duplex-layer coated AZ91 Mg alloy can serve as a promising candidate for orthopaedic applications.