Aluminum die casting Issue Protection
The organization of aluminum die casting is loose, the pore rate is high, and contains a variety of metal and non-metallic impurities. The quality of anodic oxidation film is difficult to guarantee. In order to obtain normal oxidation film quality and avoid appearing white spots after Anodic oxidation film dyeing, we should take the following measures.
1. The method of high voltage large current density impact
Adopt high voltage, high current surge in the initial period of the anodic oxidation can make the “island” that originally divided by the impurities connect a piece. The specific process is as follows:
Adjust the initial voltage of the anodic oxidation to 30V around. The current density now is about 2 ~ 2.5 A/dm2. After 3 ~ 5 min, return to the normal voltage of the anodic oxidation. After 50 min anodic oxidation and fully cleaning, it can be dyed out more satisfied oxidation film, and there are no white spots generally.
The slight deficiency of the method above is if the casting has a screw hole, the hole may be expanded slightly. So people should control the density of large current and the anode oxidation time of high voltage to prevent the temperature of the anode oxidation solution rising too fast. Continuous production need to take cooling measures on anodic oxidation solution.
2. The method of grinding on the casting surface
Grinding can produce the aluminum ends. Use the aluminum ends to fill the hole of the casting. And it has the bridge effect between each “island”. This method is not so good as the first method. Because the aluminum ends may lose the bridge effect sometimes and the filler of some parts will fall off in the alkali erosion and anodic oxidation process.
3. The method of peening the casting surface
The wall of general aluminum die casting can satisfy the pressure requirement of the peening method. It can close the pores and apertures, and improve the strength and neatness of the aluminum casting. It is the best way in the three methods.