Anodizing Tip: Black Tracking in Anodized Aluminum

      Anodizing is prone to certain issues especially with lighter colors. One of the key problems is black tracking on parts especially when the aluminum contains copper (7000 series). Below I posted a photo of a gold derailleur I did last week, 7,000 series aluminum. 

I was able to virtually eliminate the tracking issue by dipping in a weak solution of nitric, rinsing with a strong blast of hot water and repeating a few times.
In addition I remove cathodes after every run and use desmut to clean all traces of copper from the tank.
Nitric is about the only acid that will attack copper and this is a major cause of black streaks.

 Anodize World