aluminum pots need that layer of oxidation.
you can scrub it off, but then you'll need to season it again by boiling water in it for an hour (measure before & after to get your boil-off rate)
"If you want to do something, do it and then have a homebrew. If you don't want to do it, just have a homebrew" - Charlie Papazian
drinking: DB8PT Session Ale, Sweetpea's Mock Maibock, DB 8 Point IPA Clone, Witless Belgian Wit, Rain Delay IPA, Czech Pilsner, CLB's Red Barleywine, 8 Hearted Pale Ale, O'Rob's Dry Irish Stout - bottle conditioning: Otto M. Gourd Pumpkin Barleywine - bulk conditioning: barleywine