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
"Beer. Good." - Words of House Grog
drinking: Maibock, DB8Point IPA Clone, Belgian Wit, Rain Delay IPA, Wojtkowiak Piwo, CLB's Barleywine, 8Hearted Pale Ale, O'Rob's Dry Irish Stout - bottle conditioning: DB8PT Session Ale, Otto M. Gourd Pumpkin Barleywine, Jewel Thieves Apple Wine, Wojtkowiak Grodziskie - bulk conditioning: barleywine