Unlike rust, aluminium oxide layer corrosion does not attack the metal itself. However, a thin layer of this material does stick to the surface of the metal. This layer is usually brittle. However, it does not flake off like stainless steel or titanium.
When aluminium is exposed to oxygen, it forms an oxide layer on its surface. This layer forms naturally in the air and it is not easily chipped off. It can be seen as a white powdery coating on aluminium.
The aluminium oxide layer can be formed in a variety of different ways. It is also known as anodised layer. The layer is usually made to be thin enough to coat the surface of the metal. When it is thin enough, it will be a conformal layer that will protect the metal from corrosion. However, when the oxide layer is not thin enough, it will not completely cover the aluminium surface.
In the case of atmospheric corrosion, the aluminium oxide layer is damaged by various elements. For instance, sulfides are common in the air. In addition, mercury can disrupt the aluminium surface layer. The pH level and the velocity of water can also aggravate this form of corrosion.
Aluminum oxide is not soluble in solutions with low pH. However, it is soluble in a variety of acids. This allows it to oxidize at a faster rate than steel oxidation.
There are several types of corrosion that can occur to aluminium. The most common is atmospheric corrosion. It can be classified into wet and dry types.