You may find that sometimes aluminum die castings have black spots when polished. Why does this phenomenon occur? Watch will answer for you: There are several reasons. It is possible that the die casting mold is made of silicon oxide, or aluminum oxide is formed. The solution is simple, use fresh aluminum ingots.
Secondly, it may come from the release agent. It may be that too much release agent is sprayed on aluminum die castings, or it may be that the organic content of the release agent is too high.
Under the temperature of hot melted aluminum, some of these organic compounds are reduced to carbon elements, and some become organic macromolecular polymers. The mixture of these carbon molecules and polymers is contained in the surface layer when the aluminum casting is formed, becoming the black spots we see.
