POR 15

I used POR15 on my engine compartment and it seem to fade from the sun. I wouldn't suggest using it on anything exposed to sunlight.

Yeah, POR-15 requires a topcoat of some type if it will be exposed to sunlight. They even tell you this in the instructions. You can use their chassis coat paint or any other type you like as long as you follow the instructions. My friend uses a lot of POR-15. he has basically entombed his car in the stuff. I use Corroless for the most part because I like how it paints much better and I don't have any severwly rusted parts I am trying to save.