Control Of Degradation Rate Of Medical Mg-Zn-Sr Alloy By Biomimetic Coating

Magnesium alloys is considered as a potentially biodegradable biomedical materials due to its good biocompatibility,degradability and mechanical properties of matching human bone,so can effectively avoid the secondary surgery.However,the high corrosion rate that can not match the rate of bone healing badly confined their application in clinical,become a biggest problem of magnesium alloy as biomedical material.Therefore,The key is to improve the degradation rate of magnesium alloy as medical material.First,the success of prepared Mg-2.96%Zn-0.317%Sr-0.313%Ca alloys and Mg-2.67%Zn-0.67%Sr alloys,then respectively to test the performance of the two alloys,HA coating was generated on the alloy surface by biomimetic method,and coatings are studied by X-ray diffraction technology,scanning electron microscopy.The electrochemical corrosion and immersion corrosion of the without,once,twice coatings alloy samples in human simulated solution are studied,and the results are as follows:(1)Mg-2.96%Zn-0.317%Sr-0.313%Ca alloy and Mg-2.67%Zn-0.67%Sr alloy are yield strength of 131 MPa,113 MPa;tensile strength are 250 Mpa,230 MPa;compressive strength are 411.92 MPa,317.31 MPa;extending rate are 20%,21.4%;the density are 1.752 g·cm-3,1.748 g cm-3;the alloy are plastic materials.(2)The once and twice HA coatings are successfully prepared on the surface of Mg-2.96%Zn-0.317%Sr-0.313%Ca alloy and Mg-2.67%Zn-0.67%Sr alloy by the biomimetic deposition method.(3)Mg-2.96%Zn-0.317%Sr-0.313%Ca alloy without,once,twice coatings samples electrochemical corrosion potential are-1.686 V,-1.5406 V,-1.457 V;current density are 1.905×104 A·cm-2,9.984×10-6 A.cm-2,7.2614×10-6A·Cm-2;corrosion resistance are 23 ?,340 ?,500 ?,;Mg-2.67%Zn-0.67%Sr alloy without,once,twice coatings samples electrochemical corrosion potential are-1.71 V,-1.67 V,-1.58 V;current density are 3.104×10-4 A·cm-2,8.764×10-5 A·cm-2,4.651×10-5 A·cm-2;corrosion resistance are 50 ?,95? 130 ?;coating increases the alloy corrosion resistance,and the twice coatings effect is the best.(4)The hydrogen evolution of the Mg-2.96%Zn-0.317%Sr-0.313%Ca alloy without,once and twice coatings samples corroded 7 days was as follows:226 ml,92 ml,67 ml;the hydrogen evolution of the Mg-2.67%Zn-0.67%Sr alloy without,once and twice coatings samples corroded 7 days are 169 ml,97 ml,24 ml.The hydrogen evolution of the twice coatings is less than once coating,and once coating is less than without coating.(5)The longer the immersion corrosion time of Mg-2.96%Zn-0.317%Sr-0.313%Ca Alloy without,once,twice coatings samples,the more weight loss.,the twice coatings samples weight loss rate is less than once coating,once coating sample weightlessness rate was less than without coating.(6)The corrosion performance of the two alloys are increased by HA coating,and the twice coatings is better than once coating.