Rustoleum vs. POR 15 vs. others

Haven't heard of the Napa stuff, I'll keep an eye out for it. We use Ospho at work a lot, which is just a rust converter, not a paint, then paint Rustoleum over the top of it. It seems to hold up, but have only been using it for the past year or so, so that is not a long enough time to tell.

If Por 15 and the others use the same chemicals, it may come down to the concentration. It's just really hard to justify buying POR 15 at nearly $50 a quart when you can get a quart of Rustoleum for under $10. 1 gallon of Por 15 is almost $150!