Deejay, I think the two fixed electrodes in the bath are connected together and have the same polarity, which is opposite to that of the part being cleaned. Their gauge doesn't matter unless or until they get eaten through. However there are practical details that are worked out from experience, and Steve obviously has that. I've used this technique years ago to remove rust and metal deposits from the bore of rifle barrels, but that is a specialised process - Steve's is more general.
