Errr... Just read the thread title again, and noticed the word chrome.
Do you mean chrome bumpers instead of fenders?
If so, there are a bunch of threads covering this already. My rear bumper (front is painted; and plastic for that matter
) had rust on the sides that face forward, and a bit around the back on the sides; again, I'm pretty sure the gigantic brakes caused it. In any event, a little chrome polish and elbow grease takes it right off. Just don't get the chrome polish on the plastic bumper step... it will turn white and look like hell.