Research On Preparation And Performance Of The HA-TiO₂ Sol-gel Composite Coating On The Magnesium Alloy

With the rapid development of biotechnology, biomedical materials has become the research and development hot. Applied in biomedical area, magnesium alloy has many advantages compared to other medical metal. It has similar mechanical properties with human bone, be biocompatibility to human body and can avoid the secondary operation. These prompt it becomes a huge potential biomedical materials. However, magnesium alloy lively nature lead to excessive corrosion rates, which makes it can’t reach the time requirement of human tissue healing, all of these limit the clinical application of magnesium and magnesium alloys. Now, how to avoid magnesium alloys corrosive has become the focus of the study.Hydroxyapatite（HA） has good chemical properties with high biocompatibility and corrosion resistance. Its proportion in human bone is about 69%. The metallic material’s corrosion degradation time can be extended as well as the healing period can be shorted when coated it on the surface of metallic materials. Ti O₂ has excellent chemical stability, biocompatibility, good mechanical performance and adhesion. It can improve the adhesion of HA coating when coated it on the surface of metallic materials.Based on AZ60, preparation of HA-Ti O₂ composite coating through coating compound and sol-gel compound is proposed in this artical. In the coating compound, first study on the process parameters of HA and Ti O₂ coatings, then compare the influences of different compound orders（HA+Ti O₂ and Ti O₂+HA coating, respectively）. In the sol-gel compound, first study on the process parameters about the sol molar ratio, the heat tenperature, aging time, the sol p H and coating layers of composite sol through orthogonal experiment and univariate experiment（HA/Ti O₂）, then study the influences of different coupling agent on composite sol coating（HA/Ti O₂/coupling agent）. Use SEM, EDS, X R D, polarization test, electrochemical impedance, delimit case law binding force test and immersion test to verify the coating, and explained how the parameters in the formation of coating affect its performance.The results explained that the Ti O₂+HA composite coating can improve a higher corrosion resistance of magnesium alloy than HA+Ti O₂ composite coating, and it can reach level "0" in mechanism testing. The coating effectively improves the corrosion resistance, Ecorr increase 322 m V; the test data shown that icorr decreased significantly. In the sol-gel compound, the silane coupling KH550 can not only solve the coating cracking, but also can improve the coating adhesion to some extent. EDS results show that elements distribute uniformly on magnesium alloy surface, these two sol combine well. The sol composite coating improves the corrosion resistance higher than the coating compound samples, Ecorr increase 372 m V, icorr decreased from 183.3×10-7A/cm2 to 2.063×10-7A/cm2. XRD results show that HA crystal and anatase Ti O₂ crystal form on the surface of magnesium alloy after heat treatment. Immersion test to review the electrochemical test data, and prove that these two kind of composite coatings were greatly improve the corrosion resistance of magnesium alloy.