Problem Due to the loose structure and high porosity of aluminum castings, it is very easy to have white spots after the anodized film is dyed, and the quality of the anodized film of aluminum castings is difficult to guarantee. In this regard, relevant experts said that the following methods can be used to avoid this problem:
First, use high voltage and high current density impact method. In the early stage of anodizing, high voltage and high current impact are adopted to connect the large and small "islands" originally divided by impurities into pieces through high current impact.
Second, the casting surface polishing method. Grinding can make the aluminum dust filled with the pores of the casting, and play the role of a bridge connecting the "islands" isolated by impurities.
Third, the casting surface shot peening method. Before the shot peening method was tried, the author used a round hammer to knock the gaps that blocked the "islands" by knocking, and the result was remarkable. These methods can effectively avoid the appearance of white spots on the anodized film of aluminum castings after dyeing, thereby ensuring its quality.
Prevention methods
1. Improve the structural design of castings, avoid sharp corners, strive for uniform wall thickness, and smooth transition
2. Take measures to increase the yield of sand molds (cores)
3. Ensure that all parts of the casting solidify simultaneously or sequentially, and improve the design of the pouring system
4. Appropriately reduce the pouring temperature
5. Control the cooling time of the casting mold
6. Use thermal correction method when the casting is deformed
7. Correctly control the heat treatment temperature and reduce the quenching cooling rate
