Compared with sulphuric acid anodising, the chromic acid anodising process gives relatively soft, thin coatings, normally of two to five microns thickness.
The chromic anodising process is used where a high resistance to corrosion is required, where crack detection is a subsidiary requirement, for the treatment of aluminium assemblies where there must be no corrosion risk from trapped electrolyte (a common problem with sulphuric anodising) and for the production of opaque enamel-like self coloured grey/black finishes for decorative use.
There are a number of key features that make chromic anodising key for particular applications:
Ideal for castings
Minimised loss of fatigue strength due to anodising
No risk of sulphuric acid entrapment and associated post treatment corrosion
Ideal for treatment of material less than 0.25mm thick
Compatible with explosives, propellants and pyrotechnics