Characterization of hydroxyapatite coating on Mg-1%Zn alloy for implant application

Abstract

Most conventional orthopedic implant used for joint and bone fractures consist of metallic biomaterials with polycrystalline microstructures that exhibit high hardness, good corrosion resistance, excellent fatigue and wear resistance. Alternatively, to avoid post extraction of the implant, intensive efforts are being made in recent years to develop new classes of so called “biodegradable implant composed of non-toxic materials that become reabsorbed by the human body after a reasonable period of time. We use Mg alloys since they have poor corrosion resistance in the body environment. i.e Mg-1%Zn alloy. Zinc improves the mechanical properties of the magnesium alloys and does not show any side effects on the human body. This investigation shows ways of improving corrosion resistance of this alloys by electrodeposition of hydroxyapatite (HA), hydroxyapatite with high concentration of phosphate (HAP), hydroxyapatite with high concentration of calcium (HACa) and hydroxyapatite with high concentration of both phosphate and calcium (HAPCa) as a bio-compatible coating. The coating improves the corrosion protection of Mg-1%Zn alloy.  The corrosion protection follows the sequence    HAPCa › HACa › HAP › HA.