Anodising aluminium provides an oxidised barrier which is 1,000 times thicker than the natural oxide that forms on raw aluminium.
The anodise is not a coating but a conversion of the aluminium surface which can never peel, chip or flake off.
This anodised surface becomes non conductive and therefore prevents the flow of electricity which causes a galvanic reaction or corrosion, which is the corrosion of two or more metals of different nobility, such as stainless steel and aluminium, resulting in the weaker being eaten away through a galvanic reaction.
Unlike raw mill finish aluminium, Anodised aluminium has virtually a life long resistance to corrosion.
As we know Spitfire Trailers are the only aluminium trailers which are anodised.
A comprehensive report on the benefits of anodised aluminium follow.
Anodising to Prevent Galvanic Corrosion
Galvanic corrosion is a serious issue across the engineering industry and it has a variety of solutions, which all boil down to one technique: breaking the circuit. Anodising is one way to break the circuit. The anodic coating is made up of aluminium oxide, which is a good electrical insulator.
The oxide layer is a thousand times thicker than the natural oxide that forms on aluminium, which offers essentially no galvanic protection.
It is sensible to use anodising because it has such good adhesion (owing to being a conversion coating) and so won't flake off like a paint might. Hard anodising can also provide protection in situations where higher wear is expected, which paint will not be able to withstand.
Galvanic corrosion occurs when two dissimilar metals come into contact. It is also necessary for there to be moisture, but it is rare to find an environment without moisture. Galvanic corrosion leads to the deterioration of one of the metals and can occur in environments that would otherwise not be considered corrosive to said metal.
Precautions When Using Anodising for Galvanic Corrosion Protection
Anodised aluminium has an electrically insulative surface, just like any of the other barrier protection techniques and if this surface is damaged then the protection it provides will be reduced or eliminated. For this reason, anodising must be done after all machining, folding or welding has been completed.
The beauty of anodising is that because it is an insulator and not a metal, it is compatible with all other common metals (from a galvanic perspective) by virtue of being non-conductive. This means, that it is acceptable to use stainless steel, zinc coated steel, titanium, nickel and others in contact with anodised components.