The surface of ordinary water is very clean. In fact, it has unraveled a lot of things. The most common are calcium and magnesium salts, followed by iron salts. Different water sources contain more or less iron salts. These iron salts are the "culprit" that causes aluminum pots to turn black.
Since aluminum is more reactive than iron, aluminum pans collide with water containing iron salts, and aluminum displaces the iron. The replacement iron was attached to the aluminum pan which turned black.
However, this chemical "trick" must succeed. Three conditions must be met:
First, the water contains more iron salts.
Second, boil water for a long time.
Third, the aluminum pot must be new, because there is a thin layer of alumina on the surface of the old aluminum pot. This layer of alumina has no chance of "beautifying the surface", and of course it will not become a "joke".
Since the black material is iron, the black color may not be removed. If you want the aluminum pot to regain its light, you can use vinegar to remove these black colors; cook some acidic foods, such as tomatoes, and dissolve the iron.
You can also put fresh apple peels into the scourge, add enough water, boil for a quarter of an hour, and then rinse with water. The aluminum pan will become as shiny as new.
