Characterization of bioactivity behavior and corrosion responses of hydroxyapatite-ZnO nanostructured coating deposited on NiTi shape memory alloy

In this research, a ceramic combination of Hydroxyapatite and ZnO with a weight ratio of 50:50 was deposited on NiTi shape memory alloy by Electrophoretic Deposition Process (EPD). Deposition of the Hydroxyapatite-ZnO on NiTi alloy was performed by applying 50 volts for 100 s. The sintering operation was then conducted for 2 h in a furnace under an argon atmosphere at 500 degrees C. In the next step, the morphology and thickness of the coating were studied by Field Emission Scanning Electron Microscopy (FE-SEM). In addition, bioactivity behavior and corrosion resistance of the coating were evaluated using electrochemical tests, and the rate of the Ni ion release has been investigated in Simulated Body Fluids (SBF) solution. The FE-SEM observations on the morphology of the Hydroxyapatite-ZnO ceramic nanostructured coating revealed that a non-crack coating with approximate 135 pm thickness was deposited on the NiTi alloy. The results also showed that the Hydroxyapatite-ZnO nanostructured coating leads to the formation of ion exchange barrier on the NiTi alloy surface which acts well as a barrier to penetrating nickel ions in the body fluid, in such a way that the corrosion resistances of NiTi alloy has been increased significantly in the presence of Hydroxyapatite-ZnO coating. Also, the adhesion strength of the Hydroxyapatite-ZnO ceramic nanostructured coating on NiTi shape memory alloy was highly desirable (about 25.4 +/- 0.1 MPa).