[Richard and Rhonda]

Are you going to strip the old paint? If not you need to scuff it with something like a 3M pad, and apply a sealant that is compatible with the top coat paint you will use. If not the paint will likely peel.

If you do strip it, then you are in for a whole different job. You must prime the aluminum with something like Allodyne, then use a primer, then the top coat.

Putting the top coat directly on the old paint, or on raw aluminum is not a long term solution in my opinion.

If you use Imron, be very careful. It is extremely toxic to breathe. It is a cyanoacrlyate catalyzed paint that basically adheres to your lung tissue like superglue.
You MUST use a respirator with supply air.