If it turns out they are galvanized under paint like my PST LP72s, you can do what I did; strip the paint off with regular paint stripper, you won't believe how easy it comes off, but try to leave as much of the galvanized finish underneath as possible. The stripper also attacks the galvanizing, but not nearly as quickly so you just work fast, get the old paint off, and wash the tank down. Then you can lightly sand, really lightly, to clean up the galvanized surface, then coat with ZRC galvilite. I used the spray cans and went through an entire can for each tank, applying a few thin coats. You can also get a quart of the stuff and roll it on; that's probably what I'd do next time, or at least use a pro spray gun. I would not bother with any other type of finish, and I'd only do it if the original paint is in really bad shape, like it was on my tanks.