Preparation Of Mg-Fe LDHs Film And Its Corrosion Resistance In Simulated Body Fluids

The lightweight metal materials magnesium and its alloys have the advantages of high specific strength,good shock absorption,recyclability and good biocompatibility,and are used in aerospace,automotive,electronics,biomedical and other fields.However,compared with other metals,its standard electrode potential is very negative,resulting in easy corrosion of magnesium and magnesium alloy.In the human environment,the rapid corrosion of magnesium alloy is always a key problem restricting its clinical application.Therefore,the study on corrosion and protection of magnesium alloys is very important for the application of magnesium alloy biomaterials.Hydrotalcite(Layered Double Hydroxide,LDHs)is a special structure and function of double metal layered compound.In situ growth of LDHs film on the surface of magnesium alloy is a new protective method to protect magnesium alloy against corrosion.In this paper,a suitable method of obtaining iron trivalent cation was found,and the types of LDHs materials prepared by in-situ growth method were expanded.The biocompatibility and biodegradability of Mg-Fe LDHs were organically combined for corrosion protection of magnesium alloys in biological environment.The composition of the film layer prepared under different technological conditions was analyzed by means of X-ray diffraction(XRD)and EDS elemental analysis.The surface morphology of the sample was observed by scanning electron microscope(SEM).finally using electrochemical workstation polarization curves of the samples have been measured,optimizing the Mg-Fe LDHs film preparation technology and research in 37 ? Hank 's solution coating corrosion resistance performance.Through the preparation experience of Mg-Al LDHs film in magnesium alloy and previous experiments,iron ions were successfully introduced into carbonic acid film solution,and Mg-Fe LDHs film was grown in situ on the surface of Mg-Ca alloy by two-step method.The effects of two different methods of introducing iron ions on the film preparation were studied.It was found that the preparation of Mg-Fe LDHs films had little effect on the quality of the resulting films.Therefore,the focus of this paper is to systematically study the effects of post-treatment process parameters on the composition,morphology and corrosion resistance of Mg-Fe LDHs films.The results show that the pH value affects the quality of the membrane layer.When the pH value is low,the deposition of the membrane is unfavorable and there are more microcracks on the membrane surface.As pH increases,the film becomes dense,but the composition becomes less and less pure.Temperature affects the amount of sediment on the surface of the film.At 55 ?,the composition of the film is more pure,and the film thickens as the temperature rises,but the temperature is too high,which is not conducive to the conversion of hydroxide into LDHs.The post-treatment time has a great influence on the transformation of the structure of the hydrotalcite film.When the film time is less than 12 h,only a small amount of the hydrotalcite is generated,most of which are still hydroxides,and the film thickness is also relatively thin.The Mg-Fe LDHs film prepared under the best technological conditions is pure in composition,which plays a good protective effect on magnesium and calcium alloy in simulated body fluid.The corrosion potential of MgCa alloy substrate increased by 0.14 V,and the corrosion current density decreased by about an order of magnitude.It lays the foundation for the application research of magnesium alloy in biomedicine.