Just got my winters mounted on black steel rims and am looking to clean up the look a bit. The rims are brand new so they are solid black already but I'm thinking of just spraying the nuts/center of the wheel so it's a solid black.

Do I need to sand or use primer first or just have at er' with a spray can?

I don't want to damage the hardware or anything :)

(I am a truck/vehicular noobie)