The anodic film formed in chromic acid anodising is considerably thinner than that obtained in sulphuric acid anodising, typically between 3 and 5 microns. It is, however more flexible and provides a good protective surface for subsequent painting for demanding applications. As the chromic acid is not corrosive to aluminium it can be used where there is a probability of seepage from lap joints etc. Due to the bright red colour of the electrolyte it is also used for crack detection in forgings.
Alocrom 1200 chromating process gives a straw to gold coloured very thin film on aluminium alloys, that is electrically conducting, corrosion resistant and a very good pre-treatment for painting and powder coating. Steel inserts are unaffected by the process (unlike in the anodising processes) so assembled components can be processed.
The chromate conversion process can be used as a repair in certain instances where an anodic film has been damaged.
We can also offer stainless steel passivation on small parts and application of dry film lubricants to anodised components and other alloys typically for aerospace applications. The passivation process uses hot oxidising acids to remove surface iron and forming a thin oxide film to protect the component. A subsequent test for surface iron ensures that the process has successfully transformed the surface.