表面处理对AZ31B镁合金耐蚀性及血液相容性的影响.docx

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Abstract:
Magnesium alloy AZ31B has attracted increasing attention in biomedical engineering applications due to its excellent biocompatibility and biodegradability. However, its poor corrosion resistance and potential negative effects on blood compatibility have hindered its widespread use. This paper reviews the effect of surface treatments on the corrosion resistance and blood compatibility of AZ31B magnesium alloy, including chemical treatments, electrochemical treatments, and physical treatments.
Introduction:
Magnesium is the fourth most abundant element in the human body and is therefore an attractive material for biomedical engineering applications. Magnesium alloys have been widely investigated for surgical implants, drug delivery systems, and tissue engineering scaffolds due to their excellent biocompatibility, biodegradability, and mechanical properties. Among various magnesium alloys, AZ31B alloy is the most commonly used in biomedical field owing to its good corrosion resistance, acceptable mechanical strength and decent biocompatibility 1. However, the low corrosion resistance, especially under physiological conditions, is a major drawback of magnesium alloys, which can not only affect the durability of implants but also cause release of magnesium ions, leading to negative effects on cells and tissues. Furthermore, magnesium alloys may have potential negative effects on blood compatibility, such as platelet activation and aggregation. Therefore, it is essential to improve the surface properties of AZ31B magnesium alloy to enhance its corrosion resistance and blood compatibility.
Surface treatments:
Surface treatments are effective ways to modify the surface properties of magnesium alloys. Various chemical treatments, electrochemical treatments, and physical treatments have been employed to improve the corrosion resistance and blood compatibility of AZ31B magnesium alloy.
1. Chemical treatments:
Chemical treatments involve immersing the alloy in a solution containing certain chemicals, creating a surface layer with different chemical composition or morphology, and improving its corrosion resistance. Among various chemical treatments, the most widely used treatments are anodizing and conversion coating.
Anodizing is a process that forms an oxide layer on the surface of magnesium alloy by applying an electric current. The anodized layer can improve the corrosion resistance of the alloy and provide a substrate for further coating deposition. Studies have shown that anodization of AZ31B alloy in sulfuric acid solution can significantly enhance its corrosion resistance and decrease the release of magnesium ions 2. In addition, anodized AZ31B alloy can also improve cell adhesion and proliferation 3.
Conversion coating is a process that forms a protective layer on the surface of magnesium alloy by a chemical reaction between the alloy and a coating solution. The resulting coating can improve the corrosion resistance and biocompatibility of the alloy. Various conversion coatings have been developed, such as phosphate-based and silane-based coatings. For example, a phosphate-based coating was found to effectively increase the corrosion resistance of AZ31B alloy and reduce the cytotoxicity of its corrosion products 4.
2. Electrochemical treatments:
Electrochemical treatments involve applying a voltage or current to the alloy in an electrolyte solution, creating a surface layer with modified chemical composition or morphology, and improving its corrosion resistance. Among various electrochemical treatments, the most commonly used treatments are plasma electrolytic oxidation (PEO) and electropolishing.
PEO is a process that creates a ceramic-like coating on the surface of the alloy by a plasma discharge in an electrolyte solution. The resulting coating can significantly improve the corrosion resistance and biocompatibility of the alloy. Studies have shown that PEO-treated AZ31B alloy exhibits a much lower corrosion rate and higher hardness than untreated alloy, while maintaining good cell viability 5.
Electropolishing is a process that removes the top surface layer of the alloy by applying a high voltage in an electrolyte solution. The resulting surface has a smoother and more uniform morphology, and better corrosion resistance. It has been reported that electropolished AZ31B alloy exhibits a significantly lower corrosion rate and better hemocompatibility than untreated alloy 6.
3. Physical treatments:
Physical treatments involve surface modifications by physical means such as plasma spraying, laser beam irradiation, and friction stir processing.
Plasma spraying is a process that deposits a layer of ceramic or metallic coating on the surface of the alloy by high-temperature plasma spraying. The resulting coating can improve the wear resistance and corrosion resistance of the alloy. For example, AZ31B alloy coated with a hydroxyapatite coating by plasma spraying has been shown to exhibit good corrosion resistance and biocompatibility 7.
Laser beam irradiation is a process that creates a surface layer with altered chemical composition or morphology by applying a high-energy laser beam to the alloy surface. The resulting surface has a refined microstructure and improved corrosion resistance. Studies have shown that laser beam-irradiated AZ31B alloy exhibits improved corrosion resistance and better biocompatibility than untreated alloy 8.
Friction stir processing is a process that creates a surface layer with improved mechanical properties by applying frictional heat and deformation to the alloy surface. The resulting surface has a refined microstructure and improved corrosion resistance. It has been found that friction stir-processed AZ31B alloy exhibits higher hardness and better corrosion resistance than untreated alloy 9.
Conclusion:
Surface treatments are effective ways to modify the surface properties of AZ31B magnesium alloy to enhance its corrosion resistance and blood compatibility. Among various treatments, anodizing, PEO, and electropolishing are effective electrochemical treatments, while plasma spraying, laser beam irradiation, and friction stir processing are effective physical treatments. These surface treatments can significantly improve the corrosion resistance, wear resistance, and biocompatibility of AZ31B magnesium alloy and make it more suitable for biomedical engineering applications. However, further studies are required to investigate the long-term effects of the treated surfaces on cells, tissues, and organisms.