[JWFokker]

I'd just polish it and spray a couple layers of clear coat on it to prevent oxidization. Have you checked Linens N Things for a stainless steel mixing bowl? They're supposed to have good ones similar to the Norpro.

Of course, this is assuming that the clear coat sufficiently prevents oxygen from reaching the surface of the aluminum, which I have no idea whether it does or not. It could be entirely oxygen permeable for all I know.