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Anodic oxidation

Dimensional change by increase in layer thickness

 
In the anodic oxidation of aluminium 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 layer, the aluminium oxide has more volume than the aluminum and therefore the metallic substrate surface by anodizing will always have a dimensional change.


Anodizing

What size the dimensional change is, is precipitated alloying and process-specific.
In normal anodizing it is usually negligible
and is about 1/3 of the oxide 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.

In a normal anodizing process, the oxide layer grows columnar two-thirds into the base material, it builds up to a third on the outside.

Aluminium oxide layers are microporous pigments and these pores can be incorporated. By a compression process, the pores are closed again stable.

For the anodising of aluminum alloys, the recommendations of the relevant DIN EN 573-3 and DIN EN 1706 apply.
 

At ELB® aluminum alloys are analyzed in principle for customer projects, at any time to achieve and to respond to the slightest fluctuations in the process itself for optimal results.

 
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