Anodising

Anodising is a treatment process for ALUMINIUM.  It can be performed in coloured or clear finishes.  The process is commonly used wherever the aluminium is likely to be exposed to weather extremes - mainly to prevent corrosion and often to attain a particular sheen or appearance.

PLEASE NOTE that A Class Metal Finishers does not perform anodising processes on site, however in many cases we can arrange this work for you on a subcontract basis through other suppliers.  We can also advise you on alternative treatments and finishes for aluminium items.

As a simplified explanation - the anodising process works, in a way,  like a "reverse" of an electroplating process.   Rather than adding a coating of metal to the surface, anodising 'opens pores' in the surface of the material, creating a form of oxidisation.  Once the pores are open, colour 'dyes' are added, which 'grip' the oxidisation then the pores are closed, thus embedding the colour into the surface and creating a protective surface.

Anodising, depending on what it is exposed to, can still eventually corrode.  The strength of corrosion resistance is determined by the depth at which pores are opened (amount of oxidisation) in the process.  The deeper the oxidisation - the more corrosion resistance, but also the duller the surface becomes.  For decorative applications sometimes it is desirable to have a bright, shiny appearance but this is only possible by opening the pores (oxidising) less.  So it's a trade-off between appearance and corrosion resistance.

A Class Metal Finishers can electroplate aluminium items (not all platers can or will).  As we have specific pre-treatments for aluminium this enables us to electroplate in any of our plating finishes (for example, chrome, gold, satin chrome, nickel and so on).  There are limits, however, to the size and shape of parts we will plate.  For example we would not chrome long lengths of extruded aluminium commonly used for window construction

Another common treatment for aluminum is simply polishing it.  This can achieve a brilliant lustre and can come close to the appearance of polished stainless steel.  This is common for applications like aluminium vehicle trim or alloy wheels.  The downside is that the parts may require a bit more maintenance or upkeep to maintain appearance.

Whilst it is often possible to re-anodise parts, it can be problematic if the part has become very corroded, in which case anodisning can not "heal" the corrosion.  In such cases, A Class will usually suggest either polishing or plating, depending on the appearance or finish you are seeking.

Sometimes plating is not recommended for certain parts - for example original car parts of complex shapes (plating can sometimes not reach very deep recesses).  So re-anodising may be the best approach as long as there is no severe corrosion - in which case we would likely recommend polishing.

If your choice is to re-anodise, A Class would prepare the surfaces (clean up and polish) prior to sending out for anodising.  You can of course go straight to an anodiser yourself however be aware that many anodisers do not provide preparation pretreatments for restoring parts.