Aluminum is very active, is one kinds of metal can be oxidized in a natural environment, easily oxygen oxidation in the air, once the formation of a layer of oxidation can prevent further oxidation of aluminum metal, thereby protecting the metal, this is natural oxidation.

But this layer of oxide film is thin, about 0.01 to 0.1 microns of oxidation film, this layer of oxide film is non-crystalline, thin and porous, poor corrosion resistance. This layer of oxide film protection film in acid icing conditions unstable, with the intensification of environmental pollution, acid rain and other natural phenomena increase, now more serious pollution of the region, rain pH in about 3, acid rain or acid mist will lead to the aluminum profile surface of the oxide film destroyed, resulting in aluminum profile oxidation.

On the surface of aluminum profiles, we often see piles of white powder, i.e. the oxide film on the surface of the aluminum profile, which is destroyed, resulting in the oxidation of the aluminum profile by oxygen in the air. Then we need to oxidize it again and add another layer to the surface to improve the surfaces corrosion resistance protective film.