Corrosion Behavior Of Extruded AZ80 Magnesium Alloy In Simulated Human Body Fluid

Because of its good structural properties and biocompatibility,magnesium alloys have attracted more and more attention of medical materials researchers,But its low balance potential makes magnesium alloy material susceptible to corrosion,resulting in magnesium substrate in the human body greatly reduced the service life,Make the magnesium alloy is not enough to meet the minimum time required for the implant to achieve good mechanical support in the human body.The extruded AZ80 magnesium alloy has a relatively uniform grain structure compared with the cast AZ80 magnesium alloy,which is characterized by a cell-like crystal,which in principle has better corrosion resistance than the as-cast.In this paper,the corrosion behavior of the extruded AZ80 magnesium alloy in the initial state,solid solution and aging state in simulated human body fluid was studied.The corrosion degree of the material was measured by immersion hydrogen evolution test,immersion weight loss test and electrochemical polarization curve test,The corrosion specimens were observed and analyzed by macroscopic observation and SEM test.The corrosion products were filtered,collected and ground,and the corrosion products were qualitatively analyzed by XRD test.The corrosion behavior of extruded AZ80 magnesium alloy in pH=7,pH=8,pH=9,pH=10 and pH=11 simulated fluids was studied respectively under three heat treatment conditions.The influence of the ion composition in the solution on the corrosion behavior of the AZ80 magnesium alloy has been investigated.the corrosion results of three kinds of alloys of initial state,solid solution and aging state found by the heat treatment of the extruded AZ80 magnesium alloy which is immersed in the simulated body fluid at different pH values were analyzed.The results show:The corrosion resistance of the samples annealed with AZ80 magnesium alloy increases with the of thesurface film,thereby reducing the corrosive and other strong corrosive ions like Cl-.The measured polarization curve shows that as the pH increases,The degree of surface corrosion decreases correspondingly,with the increase of self corrosion potential,the corrosion current density decreases.The corrosion resistance of the extruded AZ80 magnesium alloy in the same pH value solution is as follows: aging state > solid solution state > initial state.By means of SEM microanalysis and EDS analysis,it was found that solid solution treatment changed the number,morpH ology and distribution position of the second pH ase?-Mg17Al12,and consequently affected the corrosion resistance of the corresponding alloy.The corrosion is difficult to accumulate where?-Mg17Al12 is enrichment.the corrosion tendency of the sample tends to be uniform corrosion,and then the corrosion resistance of the magnesium alloy is modified,because of the corrosion of the ?-Mg17Al12 on the surface of the sample and the corrosion area acting as anode and cathode,The results show that the corrosion resistance of the AZ80 magnesium alloy is as follows:HPO42-> H2PO4-> glucose> HCO3-> SO42-> Cl-,which played a major role for the Cl-,The other ionic components affect the corrosion performance by participating in the formation of the surface product film in which SO42-is predominantly present in the form of MgSO4?participating in the formation of the surface layer is more loose,Cl-and other small molecules hinder the role is not obvious.H2PO4-and HPO42-solution samples of the lowest degree of corrosion,which is the surface of the sample to form a stable pH ospH ate protective film.Glucose can make the corrosion oxide film dense,and the surface layer from the corrosion potential rise,thereby improving the corrosion resistance of magnesium alloy samples.The change of pH value,alloy condition and solution composition did not change the corrosion type of extruded AZ80 magnesium alloy.The main corrosion types were pitting corrosion and filiform corrosion.