I've used it on some small areas and have been very satisfied with it. They also sell a thick paste version of POR 15 which I used on my 70 coupe below the rear window after I peeled off the old vinyl top. I patched a hole the size of a nickel with it. I cut some mesh larger than the hole, then coated the paste on the hole's edges, put the mesh down, then pasted over the mesh with the POR 15 some more. It dried very solid and once the new vinyl top was on it worked fine. If you follow the directions it should last a long time, but don't plan to use it on surfaces that you want to paint over because paint won't stick to it very well.
I used to work in a custom boat shop, and they loved the stuff. The 'clear' keeps aluminum looking really nice in salt-water conditions. They recommend using their "Metal-Etch" prep solvent first, I think. I'm not sure if that's a part of the 3-step restoration process or not.
Buy the small cans,It goes a long way.Wear GLOVES it dose not come off BELIEVE ME.I bought a quart did my engine compartment,my sos did underneath his firebird and had some left.Then it went bad.The can was beat up.I still had a 1/4 left.
I used it when I did my interior in wvcat. I painted all my floors and around the whole back window frame. I had some pin holes around the window that I brazed & my floors had deep surface ruston the ps front. I painted the window frame before installing the glass with base coat clear coat and it came out good with no problems. To paint it they recomend you either prime it while its still tacky or sand it first. I sanded it. That was 2 winters ago and it seems to be holding up great.