For die-casting enterprises, post-plating treatment is very important. In the process of electroplating production, the pre- and post-treatment of castings are very important. Many die-casting enterprises find that most of the undesirable phenomena during the full inspection are caused by defects in surface treatment. Before the treatment, everyone is still cautious, because in the public understanding of the die-casting industry, if the pre-treatment is not done, the electroplating will definitely fail in large quantities.
However, few companies pay attention to die casting in the later processing. After electroplating, the casting is treated mainly to retain the coating and increase its corrosion resistance. The treatment methods adopted are dehydrogenation and passivation treatment, and organic film coating is also required when necessary.
Hydrogen removal treatment
The removal of hydrogen is particularly important for electroplating products, because in the electroplating system, metal ions obtain electrons through the cathode. Similarly, hydrogen ions can also obtain electrons to generate atomic hydrogen, which penetrates into the metal coating. After being left for a period of time, it becomes loose, and hydrogenation will combine in an atomic state to form hydrogen, causing its volume to expand, resulting in pinholes, bubbling, and even shedding of the coating. If it penetrates into the matrix, it will also cause hydrogen embrittlement of the entire component, especially high-strength steel. Once hydrogen permeation occurs, it is easy to cause brittle fracture of the component. Therefore, after electroplating, heat treatment should be carried out at a certain temperature for several hours to drive out the hydrogen that has penetrated into the coating or the base metal.
Passivation treatment
Passivation treatment is a method of chemical or electrochemical treatment in a certain solution to form a stable, dense and stable film on its surface. Passivation will further improve the corrosion resistance of the coating and increase the surface gloss and anti-pollution ability.