Originally Posted by kfscoll

The factory wheels have a two-stage paint on them -- it's black under a metallic silver paint -- that's called "ghost chrome." That's what gives the wheel its unique look but that's what also causes the black spots to appear when the wheels are damaged.

DO NOT USE any type of abrasive polish or cleaner on the wheel. The top metallic layer is EXTREMELY thin and extremely easy to polish off (ask me how I know).

If you can convince Nissan to repaint your wheels that's probably your best bet. A professional aftermarket powdercoat would almost certainly be more uniform and more durable than the factory wheel finish.