Don't know if this is any help,but I painted a few aluminum boats that I stripped down to bare aluminum with very good results.
I used a vinyl etching primer made by Sherwin Williams automotive coatings division.
http://www.sherwin-automotive.com/pr...product=E2G973
It's a two part primer that gives outstanding adhesion.I sprayed the finish coat with their two part Sunfire urethane.It was an extremely durable finish.I trailered these boats,but would occasionally leave them in the water for two or three weeks with no problems.