Go to your local "jobber" (NAPA, Carquest, etc) and ask for Mar-Hyde Tal-Strip 2. The 2 is the important part Tal-Strip is for metal etc. Tal-Strip 2 is for aluminum and even has an aircraft on the label. They may have to order it in.. most seem to only keep the Tal-Strip in stock.
Key is.. brush it on and DON'T touch it again. It needs to gel over/seal for the chemicals to do their job under the gel.
BTW.. it's about $40 to $50 a gallon!