The properties of insulating anodic oxide films

The oxide films formed by anodization of metals can be classified roughly as either non-porous or porous. The former class grows in thickness to an apparently limiting value which is proportional to the applied voltage. The latter class grows until the rate of loss of oxide (e.g. by dissolution in the anodization electrolyte) balances the rate of formation. The properties of the films depend on the conditions of anodization, but some typical values are quoted for various anodic coatings. The uses of the coatings in the electronics industry are briefly described.