Your ideal paint would be something like por-15. That stuff is extremely though but the process of applying it is lengthy and expensive.
Unlike the previous poster, I dislike rustoleum. I've had too many issues with their coats chipping too easily. On my steering components, I've had good luck with dupicolor engine enamel from advance auto. It's held up the best out of anything I've tried. Obviously, anything that is going to be scrapping up against rocks will need touched up occasionally.