1. Causes of oxidation
The surface of aluminum foil paper is usually coated with a protective oxide layer to protect the inner aluminum foil from oxidation and corrosion. However, if the coating quality is not good or the aluminum foil is affected by external environments such as pollution and friction, the protective oxide layer will be destroyed, and the inner aluminum foil will oxidize and rust, forming black matter.
2. Causes of metal reactions
On the other hand, the coating on the surface of aluminum foil may also react due to environmental influences such as temperature and moisture. For example, when grease-coated food is stored on aluminum foil for an extended period of time, the acidic components of the grease may attack the coating, causing the aluminum foil beneath the surface coating to react. This reaction will produce a black substance under the surface coating of the aluminum foil.