Patrick and Mike,
I disagree that all metals can be anodised. Anodising (UK spelling with s not
z!) aluminium (UK again with extra 'i'!) takes advantage of the fact that
aluminium oxide is very stable, and bonds very well to the aluminium
underneath - the process uses electrolysis to encourage a layer of aluminium
at the surface to oxidise. This protects the metal underneath (pure aluminium
is very reactive), and also aluminium oxide can be stained, hence the colour
can be applied. Hooray for my old A-level chemistry exam from 10 years ago -
I haven't quite forgotten it all yet!
We all know, however, that iron oxide is NOT stable, or bonds well to the
surface - it goes yukky and brown and flakes off, because it is RUST!!
Therefore steel, which is mostly iron, CANNOT be anodised. Stainless steel is
iron mixed with a little of another metal (don't know what), which dissuades
it from rusting.
There may well be processes that give a similar effect to anodising on the
surface of steel, and I couldn't honestly say what is possible with brass
(particularly since that is not a pure metal) so I'll keep quiet on that
subject! It is possible that the word has become mis-used over time, to
describe processes that give a similar finish to anodising, but are in fact
completely different.
Richard and Daffy (who would look great, and rust-free, with a body made
entirely of anodised shiny aluminium!)
|