Main properties and control of anodic layers
Anodizing of aluminium and its alloys

As an anodic layer is not a coating, the notion of adhesion, by comparison with organic coatings or electroplating, has little meaning here. The tests specific to coatings should therefore not be applied to anodizing. In fact, detachment of the oxide layer from the underlying metal is only rarely observed, as in the case of burn-in phenomena.

As we have seen, anodic layers can range from a few hundred nanometers (barrier layers) to a hundred micrometers (hard anodizing)....