P. K. Wong, C. T. Kwok, University of Macau, Macau, China
Titanium and its alloys are often used in orthopedic surgery and dentistry due to their excellent corrosion resistance, high mechanical strength and low density. However, their inertness and low biocompatibility are the most serious drawbacks for biomedical applications. In order to improve their biocompatibility, hydroxyapatite (HAP) is often coated on surface of metallic implants by plasma spraying. However, the plasma sprayed HAP coatings suffer from various problems such as high degree of porosities, poor bond strength, non-stoichiometric composition and amorphous structure. In the present study, nano-HAP particles were prepared by ultrasonic precipitation and the nano-HAP coating was fabricated on titanium alloy by electrophoretic deposition. Microstructure, compositions and crystallite morphology of the nano-HAP coating were analyzed by means of scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffractometry (XRD) respectively. In addition, the corrosion behavior of the coating in Ringer’s solution at 37 oC was investigated by means of open circuit potential measurement and potentiodynamic polarization technique. By XRD analysis, the size of the nano-HAP crystallite was about 20 nm. Moreover, the results of electrochemical corrosion studies illustrated that the nano-HAP coated Ti possessed significant improvement in corrosion resistance compared to the uncoated Ti and the micron-sized HAP coated Ti as reflected by the noble shift in corrosion potential, wider passive range, and reduction of corrosion and passive current densities.
Summary: Titanium and its alloys are often used in orthopedic surgery and dentistry due to their excellent corrosion resistance, high mechanical strength and low density. However, their inertness and low biocompatibility are the most serious drawbacks for biomedical applications. In order to improve their biocompatibility, hydroxyapatite (HAP) is often coated on surface of metallic implants by plasma spraying. However, the plasma sprayed HAP coatings suffer from various problems such as high degree of porosities, poor bond strength, non-stoichiometric composition and amorphous structure. In the present study, nano-HAP particles were prepared by ultrasonic precipitation and the nano-HAP coating was fabricated on titanium alloy by electrophoretic deposition. Microstructure, compositions and crystallite morphology of the nano-HAP coating were analyzed by means of scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffractometry (XRD) respectively. In addition, the corrosion behavior of the coating in Ringer’s solution at 37 oC was investigated by means of open circuit potential measurement and potentiodynamic polarization technique. By XRD analysis, the size of the nano-HAP crystallite was about 20 nm. Moreover, the results of electrochemical corrosion studies illustrated that the nano-HAP coated Ti possessed significant improvement in corrosion resistance compared to the uncoated Ti and the micron-sized HAP coated Ti as reflected by the noble shift in corrosion potential, wider passive range, and reduction of corrosion and passive current densities.
