Development And Properties Research Of Schiff Base Coating On ZE21B Alloy Surface Via Electrostatic Spraying Technology

Biomedical magnesium alloy vascular stents have become a research hotspot in the field of medical materials due to their excellent biodegradability,biocompatibility and mechanical support,but their poor corrosion resistance and low expression level of biological functions severely limits its application in the medical field of vascular diseases.As an organic corrosion inhibitor with high efficiency,non-toxicity,easy preparation,convenient storage and low cost,schiff base can undergo complex reaction with metal ions such as Mg²⁺and Zn²⁺and stably adsorb on the metal surface,so as to achieve the purpose of reducing the corrosion rate of magnesium alloy and improving the corrosion resistance of the alloy.The surface modification of ZE21B alloy independently developed by the laboratory was carried out by electrostatic spraying,and the feasibility and effectiveness of schiff base application in the field of biomedical magnesium alloy coating were explored.In this project,the natural extract paeonol was used as raw material,and three amino acids（lysine,glycine,and methionine）were respectively subjected to dehydration condensation reaction to synthesize three new schiff bases.Three kinds of single schiff base coating and a compound schiff base coating were prepared on the surface of ZE21B alloy by electrostatic spraying technology.Using spraying time as a variable,the optimal process parameters in the coating preparation process were explored.Scanning electron microscopy（SEM）,X-ray energy dispersive spectroscopy（EDS）,Fourier transform infrared spectroscopy（FTIR）,X-ray photoelectron spectroscopy（XPS）and other material characterization results demonstrate the successful preparation of schiff base coatings.Water contact angle data showed that the coating improves the wettability of the alloy surface.The detection results of the step profiler and the optical profiler showed that the coatings have nano-scale thickness and roughness.Combined with the micro-scale particle size distribution of schiff base solution,the technical advantages of electrostatic spraying to prepare thickness-controllable nano-scale coatings are reflected.The weightless corrosion rate,corrosion inhibition efficiency,p H value change,self-corrosion potential,corrosion current density,polarization resistance,impedance modulus and other parameters of the schiff base coating were measured by static weight loss experiments and electrochemical experiments.The results showed that the compound coating has stronger corrosion resistance,which is significantly better than the three single coatings.The FTIR and XPS test results of the corrosion products on the surface of the samples after immersion corrosion are combined to clarify the corrosion inhibition mechanism of the schiff base coating,that is,the schiff base complex formed by the chelation reaction is adsorbed on the surface of the alloy to form a dense and uniform corrosion product film to block the corrosion media from eroding the substrate and reduce the corrosion rate.The concentration extreme effect was explained for the increase or decrease of the corrosion inhibition efficiency of the coating at different spraying times,and the synergistic corrosion inhibition theory of“1+1+1>3”was proposed for the stronger corrosion resistance of the compound coating.In vitro experiments on endothelial cell adhesion,proliferation,activity,and apoptosis showd that the schiff base coating can promote the growth of endothelial cells,improve cell activity and survival rate,and cytocompatibility was significantly improved.Coatings have endothelialization function;blood test results showed that the schiff base coating reduces the hemolysis rate of the ZE21B alloy,the adhesion of platelets and fibrinogen on the surface of the samples were reduced,and the blood compatibility of the alloy was significantly improved,with good anticoagulant and antihemolytic function.Comprehensive analysis and comparison of the above results indicated that the compound schiff base coating sample sprayed for 1.5 minutes not only significantly improved the corrosion resistance of ZE21B alloy,but also has good biological effects such as promoting endothelialization,anticoagulation,and antihemolysis.Schiff base coating provides a new approach for surface modification design of magnesium alloy vascular stents...