Aluminium anodizing (Anodic oxidation of aluminium)

Anodic oxidation (anodizing) is a form of surface treatment of aluminium where the natural susceptibility of aluminium to oxidation is used. This means that the surface of the aluminium material changes to alumina. This surface layer prevents further corrosion of aluminium (protects it) and at the same time is several times more resistant to abrasion and scratches than the original material ("pure" aluminium). The surface layer of aluminium after anodizing has a microporous structure, which becomes compact by dyeing and subsequent sealing, and the resulting anodized material is smooth, hard and chemically as well as corrosive and abrasion-resistant.

Canor - fully automated line for aluminium anodizing

Aluminium anodizing process

The components to be anodized are firmly clamped and passed through individual trays of an automatic anodizing line with pretreatment baths such as degreasing, deoxidation, etching to the anodizing bath, where the aluminium components are subjected to an electrolytic process in a sulfuric acid solution in which it generates oxygen on the surface of the components, which in turn oxidizes the base aluminium material to alumina.

Anodizing of aluminium in an anodizing bath

In natural anodizing, a layer is formed in a thickness of 10 to 20 10m and is used for decorative anodizing, in hard anodizing, a layer is formed in thicknesses of 10 - 80µm.

At the end of the anodizing process, the material is removed from the anodizing bath and rinsed thoroughly. Subsequently, dyeing processes (organic) are optional.

In order for the surface to achieve the correct mechanical properties, the material is finally heated in a water bath at a temperature of 97 degrees Celsius (so-called sealing), which closes the porous alumina structure and acquires high corrosion resistance.

The resulting anodized material becomes smooth, hard and chemically, corrosive and abrasion-resistant more than the metal itself.

Influence of anodizing on component dimensions

The alumina layer grows on both sides during the anodic oxidation (anodizing) process. Outside and inside the original surface. The nominal growth outwards, i.e. the increment is about 50% of the layer thickness. This means that with a layer thickness of 30 µm, the oxidation layer causes a reduction of the hole of 2 x 15 µm = 30 µm or an increase in the area of the part by 15 µm.

Anodized parts in black

The surface colour of components after anodizing

The resulting anodized material is a natural matte silver colour, using various chemical anodizing baths, the resulting surface can be matt, semi-matt, semi-gloss or glossy in the colours natural silver, gold, champagne, stainless steel (stainless appearance), black or bronze.

We offer black and natural anodizing as standard, but after consultation, we can also make other colour shades.

Anodizing line capacity

The dimensions of the baths of the automatic line for anodic oxidation of aluminium are approximately 1.500 x 700 x 700 mm and this corresponds to the maximum size of components that can be anodized on the line - 1.250 x 500 x 400 mm.

The capacity (performance) of the anodizing line depends directly on the size of the components, their complexity and the required anodizing thickness (the thickness of the formed alumina layer by anodic oxidation on the surface of the components).