Deep Wheel Cleaner is ideal for baked on brake dust from a big set of Brembos. It's safe for ANY type of wheel, black ZL1 wheels included.
Just be sure to follow the two golden rules of wheel cleaning:
1) Don't use them when the wheels are hot
2) Don't allow the cleaner to dry on the surface, rinse thoroughly
Stand by those two and that brake dust will melt away. Once you have them thoroughly cleaned, I'd suggest getting a coat of
Quick Sealant on them to make them easier to clean, both after normal driving and track days alike.