Preparation and Properties of Modified Anti-degradation Coating on the Surface of Mg-Zn Alloy Bone Screws

The anti-degradation coatings of Ca-P with or without F on the surface of Mg-Zn alloy bone screws were prepared by the method of electro-deposition. In vitro degradation of these screws in simulated body fluid (SBF) was investigated. The morphology and the crystal structure before and after degradation of the two kinds of Ca-P coatings were researched by scanning electronic microscope (SEM) and X-ray diffraction (XRD). The results showed that the surface of the Ca-P coating without F contained lumpish and filamentous structure, while that of the coating with F was columnar. The coatings with or without F can both retard the corrosion of the screw effectively. The screws coated with FHA degraded faster than the screws coated with the coating without F. The FHA coating was resistant to the corrosion. However it couldn′t combine quite well with the complex-shaped screw, coupled with its brittleness, and it tended to peel off. In contrast, the screws with the coating without F maintained integrity, which protect the bone screws effectively.