Decorative and functional surface treatment technology firstly goes into the magnesium alloy and high value-added products market. As the magnesium alloy is extremely active, there is often a layer of oxide on the surface, therefore, magnesium alloy surface treatment has some difficulty. We must use Special treatment. The existing surface treatment technology is not mature, often the alloy surface is very rough and use of a large number of non-environmentally friendly chemicals. Magnesium alloy in recent years, advanced surface treatment technology has a new development.
The development of the technology, including electroplating, conversion layer and anodic oxidation these three parts. Magnesium alloy surface treatment is mainly to improve the appearance of the product and improve wear resistance and corrosion resistance, its function has the following points:
(A) decorative surface;
(B) forming a protective layer to prevent magnesium alloy from being exposed to air;
(C) filling and modifying the surface pores of the die casting;
(D) increasing the adhesion between the magnesium alloy substrate and the organic coating;
(E) improve wear resistance;
(F) Insulating magnesium alloy with other metals to prevent electrochemical corrosion.
When selecting the appropriate surface treatment process, it must first consider the needs of products, such as surface conductivity, abrasion resistance, product application environment, and other components of the selected magnesium alloy material, must be considered. Magnesium alloy surface treatment technology is for the above points.
Magnesium alloy plating is divided into two categories, one is after the activation of the alloy directly no electrodeposition nickel; the other hand, can also be after the electrodepositing zinc, and then to be plated. The process is as follows:
Direct no electrodeposition nickel method
Degreasing → pickling → activation 1 → activation 2 → no electrodeposition nickel → heat treatment → electroplating copper → other plating
electrodeposition zinc method
Degreasing → pickling → activation 1 → activation 2 → zinc → copper plating → other plating
After pre-treatment, the magnesium alloy can be plated according to product requirements of the required metal, but also through the vacuum ion plating to get more diverse, better coating. The surface of the magnesium alloy after electroplating can ultimately be bright, good in electrical conductivity, good adhesion, and can be tested by> 100 hours salt spray.
The biggest advantage of Magnesium alloy anodized film is hard, wear resistance and corrosion resistance is superb, and insulation. The process is as follows:
Degreasing → pickling → anodizing → dyeing
Through the special equipment and electrolytes, select the appropriate voltage, in the process of oxidation generated plasma (Plasma) and micro-arc (MicroArc), the magnesium alloy surface to generate a layer of dense and hard ceramic oxide layer, and through> 100 Hour salt spray test. After this treatment, magnesium alloy surface can refer to the general aluminum anodizing to be stained, but also directly covered with organic coatings or other types of coating.
3. Conversion layer
Conversion layer can bring short-term protection and corrosion resistance to the magnesium alloy surface, at the same time, can also be the solid bottom layer between the alloy and organic coating, so that the organic coating can be with better adhesion. Regarding the Conversion layer, the chrome is the most commonly used and effective method. In terms of environmental issues, the use of hexavalent chromium (Cr6 +) technology is a matter of first consideration. Therefore, using the phosphating to replace the inherent chromium, and has achieved certain results. The magnesium alloy after the phosphating has been through the 24-hour neutral salt spray test, and the surface with organic coating, salt spray test can even go beyond 300 hours, the phosphate layer can also enhance the adhesion of magnesium alloy and paint.