Black stain on painted wheel center

[BillgreenC10]

Hey guys,

The wheels on my truck are aluminum American Racing Torq Thrusts. The lip is polished aluminum, the centers are light gray paint with a rough texture. The lips were in desperate need of polishing, so I a Mothers powerball on them. Problem is I got the black residue on the painted part.

Is there anything that removes the black stuff. Tried some household cleaners and a lot of brushing with a stiff brush, no luck. Thanks in advance.