Ultraviolet Assisted Deposition Of PA&TiO₂ Hybrid Coating On Biodegradable Mg And Its Properties Research

The application of biodegradable materials have received widespread attention,with the continuous development of biomedical technology.Magnesium has a broad development prospects in the field of biodegradable material,because of its outstanding mechanical performance,which is similar with human bones.Furthermore,its biocompatibility and biodegradability promote its application in biomaterials.However,its widely application has been limited by its too fast corrosion degradation behaviors in the physiological environment.Rapid degradation can lead to many problems,such as premature failure of the implant materials,the drastically generation of hydrogen bubble.Therefore,taking appropriate methods to reduce the corrosion rate of magnesium has become an urgent priority.Surface modification,as a promising method to address issues related to corrosion control,thus far,has drawn great attention of researchers.Phytic acid（PA）,which can be found in the seeds of most plants,is a kind of natural organic substance.The 6 phosphate carboxyl groups endow PA with a powerful chelating ability with Ti⁴⁺,Zn²⁺,Fe²⁺,Fe³⁺,Ca²⁺,and Mg²⁺,forming a stable metal-organic complex.Phytic acid can also form conversion coating with magnesium base,with a strong chemical bonds.The combination of PA and magnesium substrate is firm.As a result,an effective protection can be reached by this conversion coating.TiO₂ is one of the most biocompatible inorganic material and has good corrosion resistance.However,the TiO₂ coating is brittle,resulting the poor mechanical compliance between coating and substrate.Currently,we use UV irradiation to assist deposition of organic and inorganic PA&TiO₂hybrid coating on pure magnesium.We have investigated the materials performance,corrosion resistance and physicochemical property of the coating.The research of materials performance tell us that the coating we have constructed shows high quality with dense and homogeneous structure.The chelation role of PA as well as ultraviolet irradiation jointly promote the improvement of the quality of hybrid coating.Through the study of corrosion performance we can discover that the corrosion resistance of the coating is pretty well.Transient electrochemical test shows that UV assisted deposition of hybrid coating samples have the smallest i_corr（ca.0.36μA/cm²）,approximately 20 times lower than for untreated Mg（ca.7.21μA/cm²）,as well as the biggest R_ct value（ca.108.10kΩ.cm²）,which was almost 50-fold larger than for untreated Mg（ca.2.53 kΩ.cm²）.Long-term（up to 504h）immersion tests showed that the degradation of the sample always maintain the slowest speed.Both transient electrochemical test and long-term immersion degradation behavior have proved the good corrosion resistance of the coating.We can find from the research that the good corrosion resistance are results from the high quality of the coating obtained by UV irradiation and PA chelation role.The results of physicochemical property showed that the surface of the hybrid coating deposited by UV irradiation is of superhydrophilic and compact,with Less oxygen defects in the crystal.