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Anodizing (Anodic oxidation)

Dimensional change by increase
in layer thickness


In the anodic oxidation of aluminum oxide is formed by anodic circuit in an electrolyte, we enhance the natural process of the aluminium transform into alumina. This represents the classic way of the surface finishing of aluminium.

The resulting oxide film, the aluminum oxide, has a higher volume as the metal, and therefore, the substrate always has a dimensional change by anodization.

Properties of hard anodising

  • Hardness : typically 450 to 550 HV
  • Layer thickness : 150 microns
  • Color: darker natural colors, depending on alloy and layer thickness
  • wear and corrosion resistant

Hard Anodizing

In the case of hard anodizing the dimensional change is much greater.
The unilateral dimensional change is usually 50 % of the selected layer thickness.


The graph shows the expected dimensional changes.

The resulting oxide layer provides an accurate topographic image of the original raw metal surface, ie, retained surface defects. Therefore, the pre-treatment of the material is to pay the utmost attention.