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Views: 2 Author: Site Editor Publish Time: 2023-02-06 Origin: Site
Magnesium alloy is the lightest metal engineering material in industrial applications. Its density is low, only 2/3 of the aluminum, 1/4 of the iron, and has excellent damping and electromagnetic shielding performance. It is convenient, easy to recycle, and meet environmental protection requirements. It has important application value and broad application prospects in the fields of automotive, electronics, aerospace, national defense, etc., and is known as "green engineering materials of the 21st century". Magnesium alloy has a strong electrochemical activity, and the standard electrode potential is -2.37V. It is prone to corrosion and passivation in the environment of humidity, CO2 and CI. It can naturally form alkaline carbonate in the air. At the same time, the impurities elements and alloy elements contained in magnesium alloy are easy to cause the electrical puppet corrosion, stress corrosion, fatigue corrosion, etc. during use, which greatly limits the widespread application of magnesium alloy materials.
In order to improve the corrosion resistance of metal magnesium, from the perspective of design alloys and improving casting conditions, impurities should be reduced, alloying elements should be added, and high -pure gold surface generates a membrane or coating with protective performance to improve and improve corrosion resistance. Reduce impurities through metallurgy, or add other alloy elements to limit the existence of impurities, and improve the corrosion resistance of magnesium alloy, which will make the application range of magnesium alloy expanded A few elements such as elements have not yet been widely used and cannot meet industrial requirements. Then some new types of surface treatment methods such as tin conversion film, laser surface treatment, PVD (physical gas sedimentation method), chromium nitride coating, and magnesium alloy sedimentation and other methods have also emerged. Surface modification is mainly divided into electrochemical method, chemical method, heat processing method, high vacuum and other physical methods.
Among the many magnesium alloy corrosion methods, the organic protection coating is widely used for its simple construction, economical application, non -device shape constraints and certain decorative effects. Therefore, the development of a coating system that is suitable for magnesium alloy is an effective way to improve its anticorrosive performance. In the magnesium alloy protection system, it is necessary to correctly choose a multi -layer composite coating system.
Through chemical transformation, it can form an inorganic membrane layer composed of oxides or metal salts on the surface of the magnesium alloy matrix. This film has a good combination with the substrate, which can prevent the corrosion medium from eroding the substrate. Such a conversion film itself is generally not too much The dense and corrosion resistance is not too strong. It can only be used for the protection of short -term atmospheric corrosion. But it is important that it can be found to the subsequent coating to enhance the combination of magnesium alloy base and subsequent coating. The conversion membrane can be divided into chromate and chromium -free chemical conversion system according to the solution type. Among them, the most applications in the chromium -free conversion system are phosphate film.
