Preparation And Effect Of Biological Schiff Bases On Corrosion Behavior For Mg-Zn-Y-Nd Alloy

At present,coronary heart disease has become one of the highest mortality diseases in the world,and the demand for vascular stent is increasing.As a new type of vascular scaffold material,biomedical magnesium alloy has outstanding advantages in mechanical properties,degradability and biocompatibility.When a magnesium alloy vascular stent was implanted in human body,it can not only support blood vessels,but also have anticoagulant and anti-hemolytic effects.Because the vascular stent was finally completely degraded by the human body,which greatly reduces the possibility of inflammation and thrombosis.Biomedical magnesium alloys have attracted more and more attention.However,magnesium alloys tend to fail prematurely in the process of service and lose their availability due to high activity and excessive corrosion rate.What’s more,the uneven corrosion of the magnesium alloy and the weak points formed by local excessively fast corrosion,which greatly reduce the service time of the stent and hinder large-scale clinical application of magnesium alloys.Aiming at the poor corrosion resistance of Mg-Zn-Y-Nd alloy used in vascular scaffolds,three Schiff base compounds were prepared,and their molecular structure was characterized by Fourier transform infrared spectrometer.The corrosion inhibition behavior and mechanism of the three Schiff bases were thoroughly investigated by static weight loss,inductively coupled plasma emission spectroscopy,electrochemical measurements,and surface analysis methods.Three Schiff base compounds were successfully prepared by condensation with paeonol and three amino acids（,Phenylalanine and Cysteine）:paeonol condensation tyrosine（PCTyr）,paeonol condensation phenylalanine（PCPhe）and paeonol condensation cysteine（PCCys）in 85.2%,73.4%and 72.9%yields,respectively.The cytocompatibility of the three Schiff bases was indicated and the effect of the toxicity on endothelial cells was analyzed.The corrosion inhibition behavior of three Schiff bases for Mg-Zn-Y-Nd alloy in 0.9 wt.%Na Cl physiological saline and simulated body fluids was studied,respectively.The results of static weight loss and electrochemical tests show that all three Schiff bases belong to anode corrosion inhibitors,which can effectively inhibit the anodic dissolution and cathodic hydrogen evolution process to protect Mg-Zn-Y-Nd alloy well.The results of scanning electron microscope show that the addition of Schiff bases makes the corrosion of magnesium alloy more uniform.PCTyr,PCPhe and PCCys have maximum corrosion inhibition efficiencies（physiological saline）at the concentrations of 3×10^-3mol/L,1×10^-2mol/L and 1×10^-2mol/L,respectively.And the maximum corrosion inhibition efficiencies（simulated body fluids）were got at concentrations of 1×10^-2mol/L,1×10^-3mol/L and 1×10^-2mol/L,respectively.In order to investigate the differences between the two corrosion solutions of Schiff bases,the control of different media was studied by static weight loss.It was found that HCO₃^-,Tris and HPO₄^2-were the main reasons that affected the inhibition properties of three Schiff bases in simulated body fluids.The corrosion inhibition mechanism of three Schiff bases for Mg-Zn-Y-Nd alloy in 0.9 wt.%Na Cl physiological saline and simulated body fluids was investigated.The results showed that the corrosion inhibition mechanism of Schiff bases in 0.9 wt.%Na Cl physiological saline was consistent with that in simulated body fluids.The results of energy dispersive spectroscopy,Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy show that Mg-Schiff bases compounds were formed on the surface of magnesium alloy.The Schiff bases molecules can complex with the magnesium ions released by the degradation of the magnesium alloy to form a new six-membered ring based on benzene ring,that is,the complexes of Mg-Schiff bases.The complexes precipitate with magnesium hydroxide to form dense layers on the surface of magnesium alloy,preventing corrosion media from reaching the substrate through the film layer in order to reduce the corrosion rate of the magnesium alloy.