Study On Static And Dynamic Corrosion Properties Of Zn-Mg-Mn Alloys And Mg-Mn-Zn Alloys In Simulated Fluids

Biomedical materials must be evaluated effectively in vitro and in vivo before implantation.In vivo evaluation is to implant materials directly into an animal or human body,which can obtain the most realistic corrosion information.However,in vivo experiments are complicated,so in vitro simulation experiments have become the best alternative to in vivo experiments.At present,in vitro experiments are mainly static ones,less attention is paid to the dynamic environment in vivo.The existing dynamic simulation experiments mainly focus on weightlessness experiments,other research methods including electrochemical experiments are less involved.In this paper,an in vitro dynamic corrosion performance testing device is designed,and electrochemical method is used to monitor dynamic corrosion in simulated biological fluids.Experiments show that the device is accurate and feasible,and can simulate the fluid environment of organism.The static and dynamic corrosion properties of two biodegradable metal biomaterials were studied.As biomaterial,zinc alloys have excellent mechanical properties,good biocompatibility and degradability.With the increase of magnesium,the content of Mg2Zn11 in Zn-Mg-Mn increases,which intensifies galvanic corrosion between the second phase and the matrix and increases the corrosion rate.The corrosion rate of zinc alloy in artificial plasma(AP)and artificial urine(AU)is different.Under static conditions,the corrosion rate is higher in artificial urine;while the dynamic corrosion rate of zinc alloy in artificial plasma is higher.In artificial plasma,the flow velocity(28 cm/s)has a greater effect on the corrosion of zinc alloys,and the corrosion rate under dynamic conditions is about twice.This is because the fluid has changed the structure of the passivation film on the alloy surface,so the corrosion is accelerated.However,in artificial urine,the velocity of the artificial urine environment is slow(4 cm/s),so the dynamic corrosion rate is slightly accelerated.As a biomedical metal material,magnesium alloys also have excellent performance,but the biggest disadvantage of magnesium alloys is that the corrosion is too fast.Coating is an effective means to increase the corrosion resistance of magnesium alloys.Poly(lactic-co-glycolic acid)(PLGA)has good biocompatibility.In this paper,polylactic acid glycols with molecular weights of 70,000,100,000 and 120,000 were selected as coatings.Coatings are carried out by extraction.The surface of PLGA coating is flat and combines well with the substrate,and there is no change in the structure of the PLGA after coating.The PLGA coating can improve the corrosion resistance of magnesium alloys,and the larger the molecular weight,the more obvious the effect.For uncoated magnesium alloys,the corrosion rate under dynamic conditions is significantly higher than that of static ones;the corrosion rate of the coated magnesium alloy can reach about 1/7 of that of the uncoated magnesium alloy and the difference is small under dynamic and static conditions.