Al metal generates aluminum oxide in three seconds in the air.

It only takes three seconds for aluminum to form an aluminum oxide film on the surface when exposed to the air. However, this film is dense and separates the inner layer of aluminum from the outside air, so the oxidation will not continue to deepen.

Pure aluminum is easily oxidized. Basically, if left in the air for a while (full contact for an hour), an oxide film will form on the surface. To fully oxidize the aluminum powder, it is recommended to burn it because after the aluminum oxide is formed on the surface of the aluminum powder, the interior is very stable.