Since magnesium alloys are extremely active and there is often a layer of oxide on the surface, the surface treatment of magnesium alloys is difficult.Special treatment methods must be adopted.The surface treatment of magnesium alloy mainly focuses on improving the appearance of magnesium alloy die castings and improving wear and corrosion resistance. Its functions are as follows:(a)Decorative surface;(b)A protective layer is formed to prevent exposure of the magnesium alloy to the air;(c)Fill and modify the small holes on the surface of die castings;(d)Increase adhesion between the magnesium alloy substrate and the organic coating;(e)Improve wear resistance;(f)Insulate the contact between magnesium alloy and other metals to prevent electrochemical corrosion.
When choosing an appropriate surface treatment process, it is necessary to first consider the needs of magnesium alloy processing products, such as surface conductivity, wear resistance, product application environment, and other components of the selected magnesium alloy material, etc.Magnesium alloy surface treatment technology is aimed at the above key points.1 platingMagnesium alloy electroplating is mainly divided into two categories. One is to directly perform electrodeposition-free nickel after the alloy is activated;On the other hand, it can also be electroplating after zinc deposition.The relevant process is as follows:Direct electrodeposition-free nickel methodDegreasing →Pickling →Activation 1 →Activation 2 →Non-submerged nickel →Heat treatment →Electroplating copper →Other electroplatingDegreasing →Pickling →Activation 1 →Activation 2 →Zinc sink →Electroplating copper →Other electroplatingAfter pre-treatment, the magnesium alloy can be used as magnesium alloy. cnc Processing products require the metal required, and more diverse and functional coatings can be obtained through vacuum ion plating.The surface of the magnesium alloy after electroplating can finally achieve brightness, good conductivity, good adhesion, and can pass ＞100Hour salt spray test.2 AnodizingThe major advantages of magnesium alloy die cast anodized film are its hardness, good wear resistance and corrosion resistance, and insulated.The process is as follows:Defat →Pickling →Anodizing →dyeingThrough special equipment and electrolyte, the appropriate voltage is selected to generate plasma during the oxidation process (Plasma)and microarc (MicroArc)，The surface of the magnesium alloy is formed into a dense and hard ceramic oxide layer, which can pass through ＞100Hour salt spray test.The surface of the magnesium alloy after this treatment can be dyed with reference to general aluminum anodization, or it can be directly covered with organic coatings or other types of coatings.3 Transformation layerThe conversion layer processed by magnesium alloy can bring temporary protection and corrosion resistance to the surface of magnesium alloy. At the same time, it can also become a solid bottom layer between the alloy and the organic coating, so that the organic coating has better adhesion.In terms of transformation layers, chromization is a common method, and the effect is also;However, due to environmental protection issues, hexavalent chromium is used without (Cr6+)Technology is a must-be considered.Therefore, phosphating has replaced the inherent chromization and has achieved certain achievements.The phosphated magnesium alloy can pass the 24-hour neutral salt spray test, and after the surface is added with an organic coating, the salt spray test can even exceed 300 hours. This phosphated layer can also enhance the adhesion of the magnesium alloy and paint.