What happened to the black spots when aluminum die castings were polished?

Update:18 Dec 2020

Why do aluminum die castings have dark spots when they are polished? There are several reasons for this.
1. It may be the formation of silicon oxide or aluminum oxide. The solution is simple, use fresh aluminum ingots.
2. Comes from a release agent. It may be that we sprayed too much release agent.
3. The organic content of the release agent is too high.

At the temperature of hot-melting aluminum, some of these organic substances are reduced to carbon, and some become organic macromolecular polymers. The mixture of these carbon molecules and polymers is included in the surface layer when the aluminum casting is formed and becomes the black spot we see. We can reduce the concentration of the spraying agent, switch to another spraying agent, or lengthen the blowing time after spraying. In order to reduce the formation of carbon elements and prevent the accumulation of macromolecular polymers. With the widespread application of plastic products, such as daily chemical products and beverage packaging containers, the appearance needs often require the surface of the plastic mold cavity to achieve mirror polishing Degree. The production of optical lenses, CDs and other molds have extremely high requirements for surface roughness, and therefore extremely high requirements for polishing. Polishing not only increases the beauty of the workpiece, but also improves the corrosion resistance and wear resistance of the surface of the material. It can also make the mold have other advantages, such as making plastic products easy to demold and reducing the production injection cycle.More about:custom precision die casting parts