Pure Aluminimum is least likely to corrode, but pure almunimum is too soft and isn't suitable as a construction material, to gain strength its alloyed by less stable metals to lend strength the trade off is the susceptability to corrosion.
Its expensive but aircraft Mfg's use Alclad aluminum is a sheet alloy that has a very thin covering of pure aluminum on the outside used mainly in aircraft construction, they still coat the insides with corrosion preventative zinc chromate paint, the zinc paint is a sacrificial coating like a Zinc annode on a boat hull.
Boats are constructed of cheaper alloy aluminimum, then clearcoated, the best you can do is polish off the discoloration, clean and seal, if you dont you will be chaseing your tail the whole time, you can paint with a zinc base paint (zinc chromate).
The best thing is alodine (acid etch) the surface this chemical process oxidizes a layer on the aluminum and is deactivated so a protective layer of oxidized aluminum corrosion protects the underlying structure, problem areas are the skin seams and rivets,
If you note the US Navy has Aluminum hulled war ships that are painted (low maintenance), not polished Very High maintenance) same for aircraft, most private aircraft owners will attest to the high maintenance required to keep polished aluminum aircraft pretty.