Aidan wrote:
The3rd Earl Of Derby wrote:

The process involved dipping aluminium panels in caustic soda for a
few minutes whereby it gave the surface/facia a very hard resiliant
surface,almost none scratchable.

I think caustic soda would just dissolve the aluminium.

It's not anodising, is it?

Anodising increases the thickness of the surface oxide layer, which
is absorbent and can be dyed to pretty colours. That's also why they
can't get all the paint off underground trains when they've been
defaced by morons with spray cans.

Idiots' anodising guide here;
http://www.creative-chemistry.org.uk.../anodising.pdf

Caustic soda is involved, but only for initial cleaning. The anodising
solution uses sulphuric acid.

If it's not anodising, then just ignore that.

Thanks for that,but no it didn't disslove it as it was not in the caustic
solution long enough for this to happen bearing in mind also its strenght.

I have done this ,but as i said it was quite some years ago.

The process gave the aluminium surface an semi matt appearence something
like brushed aluminium.

--
Sir Benjamin Middlethwaite