Cleaning behind rims

[MynewVR]

hey i just put on a set of chrome 18 inch rims and found that behind them is juss a little bit dirty. Theres a bit of non penetrating rust and other crap. What did you guys do to clean this up. Did u polish it up aswel?

I'm talking about the part of the car the rims fits on to, I dont know what its called. Also info about brake caliper cleaning would be useful.