Hard Anodising
Engineering finish (similar to decorative sulphuric anodising, but with greater film depth and closer structure). Can emulate the surface hardness of stainless steel.

The Hard Anodising process at Alpha is available to BS5599/DEF STAN 03-26 and MIL-A-8625 with typical coatings from 35-50 microns, although thicker coatings are available.

For more detailed technical information on dimensions and tolerances

Hard Anodising to BS5599 in engineering application is normally used in its as-produced colour. This colour is usually a grey, but the colour is dependent on alloy and processing conditions. Because of this, the only appropriate dyed finish is black, but the process may be customised to produce an attractive range of pale to dark grey finishes for cosmetic use e.g. facia panels.

For cosmetic applications requiring a finish harder than normal sulphuric coatings, Alpha now operate an alternative hard process which may be dyed a number of colours. Please call us for details.

Hard anodic coatings have specific advantages on aluminium used for engineering components, where the properties of light weight and ease of machining plus a hard surface are of particular benefit.

When specifying hard anodising careful attention should be given to the choice of alloy, not only for the colour of the film, but for the quality of coating. Whilst free cutting alloys may be hard anodised, they are not ideal, as the copper content (which does not anodise) gives rise to an open softer film.

Chromate conversion finishes
Chromate conversion is a non-electrolytic method of protecting the surface of aluminium and it alloys by a chemical immersion process. These finishes are particularly suitable as paint primers and also where electrical conductivity plus protection is required. The two processes most widely used in industry are available at Alpha.

Alocrom 1000
A colourless conversion coating that was developed to satisfy a requirement for good chemical treatment of aluminium and its alloys without significantly changing the surface.

Paint adhesion to this coating is excellent, and the electrical resistance is lower than either Alocrom 1200 coatings or untreated alloy.Alocrom 1000 is not suitable for foodstuffs and water containers.

Alocrom 1200
Produces gold to orange conversion coatings and is ideal for coating all types of aluminium and its alloys, including high silicon pressure dye castings. It is recommended for use on aluminium wherever maximum corrosion resistance is required. Coatings are flexible and will withstand bending, and inserts of steel, brass or copper are not affected by the process. Alocrom 1200 is approved to DEF-STAN 03-18 and to MIL-C-05541, but must not be used to treat foodstuff containers as it contains Hexavalent chromium.

Alocrom and W.E.E./R.O.H.S. Directives
Although the alocrom treatments contain Hexavalent Chromium, the manufacturer states in their Guidance Note P/WRGN - 1/1 "Alocrom coatings have reaction mechanisms that utilise Hexavalent Chromium but the resultant items meet the directives..." Further information should be obtained, if required, from Trimite Limited.