A Study On Corrosion Behaviors And Polymer Modification Of Magnesium Alloy

Magnesium alloys as bio-materials have many obvious advantages. By use of its poor corrosion resistance, it is possible to develop new type of biodegradable medical materials, such as coronary artery stent. In this paper, Magnesium alloys as biodegradable medical materials had been studied, including the corrosion behaviors and biocompatibility of magnesium alloy, the effects of polymer coating and surface modification on the corrosion, the biodegradable of the coating and the drug release profile from the polymer.Two kinds of commercial magnesium alloys, WE42 and AM20, had been used in this research. By use of open circuit, potentiodynamic polarization and electrochemical impedance spectroscopies (EIS), the corrosion behavior had been studied in simulated solution. The results showed that WE42 had better corrosion resistance. The immersion tests had proved the results. The in vivo experimental study showed that WE42 could be biodegradable in the rat, and had better biocompatibility. All of these showed that WE42 was more suitable to be used as stent materials.Using Modified chitosan as polymer coating, the results showed that the coating, which made magnesium alloy have higher corrosion potential and less corrosion current density, had improved corrosion resistance of magnesium alloy. The effects on the corrosion and combination intention were different according to the different surface modification. The combination intention between magnesium alloy and the coating was decrease according to this order: magnesium alloy treated with glutaraldehyde was better than that treated with coupling agent, better than that treated with acid, better than that coated directly. While the corrosion resistance of magnesium alloy treated with coupling agent was better than that treated with glutaraldehyde, better than that treated with acid, better than that coated directly. The effects were different when the chitosans were different, and the effects were little.By use of Modified chitosan as carrier, salicylic acid as model drug, the drug release profile was studied. The results showed that the release of salicylic acid was faster at first, up to 40% in 4h, then decreased, and at last only 55% was released in staticstate experiment, in which the addition of PEG had influence on the release, but the influence was little. While in dynamic experiment, about 90% of salicylic acid was released at last. In the drug-filter experiment, the diffusion of salicylic acid in the member played the most important role in filter. The more glutin in the member, the faster was the drug filter rate. The release of salicylic acid in multilayer chitosan in simulated solutions was up to 48.7% in 20 days, and the release period was up to 50 days, so the release of salicylic acid in multilayer chitosan could meet the demand of stent.