Bugs me too...but I'm not convinced its a real problem.
For 10 years or so, I've sworn by Rustoleum Top Side coat. This is very good paint for painted metal that isn't submerged. I've used it on 4 or 5 trailer frames/axles/bumpers, a few SUV frames, and many trailer hitches. Even painting over light rust, no problem. This is tough stuff and it lasts! You can find it at local hardware stores for only $10-15 per quart.