Mike Loewen wrote:
I do have some aluminum oxidation remover which
contains a small
concentration of phosporic acid which I might try (on an interior section
at first). A stainless steel brush might be a starting point to remove
the surface layer. I'll continue to collect suggestions for a bit.
If chemical treatment or polishing is inadequate, Scotchbrite pads with water
might be a next step. They can be surprisingly abrasive on soft metals (they
can remove thin plating or anodising), so one wants to be gentle at first, but
they are less aggressive than steel wool or wire-brushing. I haven't heard of
any issues with them leaving embedded particles, as has been mentioned as a
problem with steel wool.
They work well for objects with odd contours or crevices. (Also good when
building chassis for a final finish treatment on edges and some surfaces.)