I need a short proof to the obvious statement that aluminum is many
times more corrosion resistant than galvanized steel.

Aluminum oxide forms a protective coating over the rest of the metal,
whereas iron oxide flakes off.
Also, as you move to the right on the periodic table, elements become
less electropositive, and thus oxidize more slowly (for example, a
chunk of sodium metal left in open air will "rust through" in a matter
of days)