I can also attest to the durability of this stuff. Had 9 years experience on a car and 8 years on 2 pair of patio doors. The patio doors are steel and original finish lasted 4 years before pitting. Bad humid environment in the shade in Florida. Did the exact process, with POR's products, including sanding out all pitting down to bare metal. After 8 years, not one new pit. No peal, no pitting, no nothing. With Latex paint!

Cannot just put it over rust. This material keeps oxygen off the metal. A rust base will just crack the POR material and o2 will get in. In fact the cure of POR is anerobic. It consumes o2 (ie any on or near the surface of the metal) as well as the outer surface . The final finish of the stuff is a very shiny and hard, like glass.

Re painting, you have to use a special primer. Case in point. I tried applying some latex to the doors before prime for fun and it just slid off like a omelete in a pan. Incredible. Best to scuff the POR before applying the primer

Good luck Lots of prep time