Perfection 2 part over a 404/414 Epoxy Primekote should last a lifetime when placed over an acid etched mast.
Now the issue is what was the zinc chromate paint base coat made from? enamel? Sounds like you may be forced to use an enamel topcoat to remain compatible. You need to find out what the zinc paint really was.
Cal 9.2 #19 SilverSwan