Processes

Aluminium Anodising

Decorative anodising is the controlled growth of a crystalline layer of aluminium oxide. This layer is porous and typically grows out of the original metal by approx 1/3 of its thickness and grows into the metal by approx. 2/3 compared to the original aluminium surface. This anodised layer is a crystal lattice structure with a microhardness of 250 – 300 HV . It is abrasion resistant and aesthetically pleasing.

Clear anodising is usually silver in shade like the original aluminium, however the different grades of aluminium alloy can show slightly different colour tinges due to their alloying elements. Care should be taken if parts need to match and it is best to manufacture batches with all aluminium from the same source.

Colour Anodising

The anodised layer is non-detachably bonded with the base material and contains pores which allow it to be dyed various colours for a pleasing functional and decorative effect.
The surface may also be printed before the pores are sealed, giving an extremely durable, abrasion resistant marking that does not rub off.

Hard Anodising

Hard anodising is similar to decorative anodising but the process is controlled differently to give a more dense crystal structure.with a microhardness of up to 550 HV . This dense structure takes longer to produce and is more difficult to colour, the colours usually being duller than decorative anodising.

Chemical Blacking

Chemical blacking is used to treat steel items to give a black oxide film coating . It is often called Hot Chemical Blacking to differentiate from other types of black coating.

Hot Chemical Blacking ( Black Oxide Coating) provides an oxide layer which is an integral part of the steel surface. The parts are finally immersed in an ultra thin film dewatering oil which is absorbed by the oxide surface.

The advantages of hot chemical blacking are :-

it does not change the dimensional tolerances of machined components.
it provides an aesthetically pleasing engineering surface.
it provides improved corrosion resistance.
it provides a lubrication layer which reduces the effects of galling and fretting corrosion.

Zinc Plating

Zinc plating is used as a corrosion resistant surface on steel components. Rack plating is used where components are of large or irregular shape that are not suited to barrel plating . Barrel plating is typically used for nuts, bolts and washers . Finigard is an organo-mineral topcoat containing polysilicides for improved corrosion resistance.