Research On Corrosion Resistance Of Biodegradable Polymer Coatings On Magnesium Alloy

People have paid more and more attention to the use of magnesium alloy in the medical industry recently. Because of good mechanical properties and biocompatibility, it is used as medical intervention materials. But it corrodes so quickly in human bodies for its inferior corrosion resistance, the development and application of magnesium alloy is seriously restricted.The influence on the corrosion resistance of WE43 magnesium alloy by the biodegradable polymer coating is mainly concerned in this paper and the optimal protective coating of degradable polymers for WE43 magnesium alloy is selected.Results show that the corrosion resistance of WE43 magnesium alloy in PBS solution can be improved by all biodegradable polymer coating at the preliminary stage of soaking, but different characteristics and molecular weights of polymers also lead to different protective effect of coating. When soaked in PBS solution, the corrosion of WE43 magnesium alloy was accelerated by PLGA(LA/GA=50/50,80/20)and PDLLA(Mw=20,000)coatings while PLGA (LA/GA=70/30) and PDLLA (Mw=40,000) coating samples did not show this accelerating phenomenon. So PLGA (LA/GA=70/30) and PDLLA (Mw=40,000) are more suitable as protective coating material for WE43 magnesium alloy.Different gravities ofβ-TCP are added into PLGA70 and PDLLA40 to study the influence to the corrosion resistance of WE43 magnesium alloy with theβ-TCP modified coating. The results show thatβ-TCP decreases the compactness of polymer coating, so the protective effect of theβ-TCP modified coating is weaker than the polymer coating at the preliminary stage of soaking. Because of the alkaline hydrolyzing of P-TCP during the whole soaking period, the degradation speed of the polymer can be decreased while the protective time to magnesium alloy by the degradation polymer coating is extended. The optimal content of theβ-TCP is 5%.HA with different particle size is added into PLGA70 and PDLLA40 to study the influence of different particle size of HA to the corrosion resistance of WE43 magnesium alloy. The results show that HA can also decrease the compactness of polymer coating and the protective effect of the HA composite coating is weaker than the preliminary stage of soaking. The micron-HA is more suitable as the additive of biodegradable polymer for the nano-HA falls off from the coating more easily during the soaking period which can lead to the failure of coating in advance.