Aluminium oxyde is a tuff guy.
There're 2 ways to remove it; chemical or physical.
Forget the physical way if you don't want to polish it.
So it leaves you with chemical. (phosphoric) Acid based cleaner like DX-533 would do it.
You can try with vinegar, Borax or oven cleaner (lye) too.
2010 Buell Ulysses
1984 Suzuki GR650 "Tempter"
SgtDuster screwed with this post 01-28-2013 at 08:14 AM