I have been playing around with nickel plating, it looks like the same black crap forms if you run current too high on nickel plate solution. The bottle I bought claimed that 2V is a safe voltage, but when I was running that voltage on a small power supply, it blackened my parts. When I reduced the voltage it worked fine but the plating flaked off (I got lazy and decided that the ultrasonic was too much...

. You just can't tell this stuff with intuition and judgment very well... my previous nickel plating while going by the book worked fine). Also, that power supply needs to be calibrated because its my oldest HP unit. I am looking at making a battery powered one for safeys sake to minimize cabling near the solution to the hot plate.
I would guess that I need to reduce current density with the cleaning solution. I ordered some glassware and repaired some clamps and such to make proper fixtures for electropolish/clean/plate and bring temperature control into the mix. If you think about it, it makes sense, because in my previous effort the part facing the electrode turned black (high current density) and the part behind it got polished properly, this is in line with how I understand the current distribution to look like. My setup is also very bootleg.