Chromic Anodising

What is Chromic Anodising?

Chromic Acid Anodising produces relatively thin coatings that are more flexible than the Sulphuric Anodising process, better withstanding deformation and heating without cracking.

The films of around 2.5 microns tend to be opaque or semi-opaque in appearance with less wear but more corrosion resistance than Sulphuric Acid type coatings of equal thickness. The thin coating means less adverse effects on the metal being treated.

Uses for Chromic Acid products are as diverse as knitting needles to defence industry parts in contact with explosives.


As Chromic Acid does not attack the base aluminium it is safe to use on components where electrolyte may be trapped in joints and crevices and is the preferred method for castings.

The natural brown colouring of Chromic Acid may be used to its advantage as an aid to inspection of base materials for cracks and porosity.

There is very little change in dimensions of products, it is an excellent base for painting, and has superior heat resistance.

The first Chromic Acid Anodising Process was patented in 1923 and one of the first applications was for the protection of seaplanes.

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