Aluminum Discolouration Fix?

["Kai M. Radicke" <kmr@pil.net>]

Last year I had an accident involving the battery in my TR-6, and
consequently lots of acid dripped down the firewall and onto the bell
housing of my gearbox.  I have the gearbox out right now, and cleaned all
the goop off.  However, I have these ugly brown and white stains on the
majority of the bell housing.  Is there any way to get this off, other than
using say 400 grit sandpaper and gradually removing the discoloured metal?

Thanks!

--
Kai M. Radicke -- kmr@pil.net
1966 MGB -- 1974 Triumph TR-6
http://www.pil.net/~felix (pix soon)