Chrome is very smooth and shiny (obviously), and as a result, paint has a very hard time grabbing on to it. Sand the chrome with 200 - 400 grit sandpaper. The idea is to rough up the surface and give it some tooth so the paint has something to grab. Primer will also help your cause. I would recomend a sandable iron oxide (reddish in color) primer. When you buy the stuff, you definately get what you pay for. Spend the extra two or three dollars for better quality paint and you will get more milage out of the process. Lightly sand after primer and you will get a smoother finish. Also try to get all of the old paint off the chrome before you begin.

Good luck. 1987 245DL 228k (Freshly painted roof, as of last night.)