In vitro corrosion behavior of PTFE coating on AZ31 by RF magnetron sputtering for biomedical application

Surface coatings are widely used for improving the biocompatibility or corrosion resistance of Mg alloy implant materials. Polytetrafluoroethylene (PTFE) coating with about 100 nm thickness was prepared on AZ31 alloy substrate by radio frequency magnetron sputtering. The coating was characterized via X-ray photoelectron spectroscopy, fourier transform infrared spectrometer, X-ray diffractometer, scanning electron microscope, contact angle goniometer, atomic force microscope and white light interferometer. The corrosion behavior of PTFE coating were analyzed by electrochemical and immersion measurements in SBF. The results showed that PTFE coating with dense and flat surface can be formed on AZ31 alloy substrate by sputtering a PTFE target directly at room temperature. The corrosion current density declined from 1.92 × 10−4 A/cm2 (bare AZ31 alloy) to 1.07 × 10−8 A/cm2 (sample with PTFE coating), and the 7 days immersion tests revealed a complete surface morphology and very slight variation in pH value of the SBF, suggesting a significant increase in corrosion resistance. High viability rate of endothelial cells of the PTFE coated AZ31 proved the good biocompatibility. These results manifest that the PTFE is a protective coating on magnesium alloys for implants application.