Will brass contaminate a rhodium solution even with a pre-plate?

I manufacture a line of brass and copper jewelry. I want to plate Rhodium over Brass(70% copper 30% zinc). The Midas plating chart I have shows that I just need to do a nickel pre-plate over Brass to plate Rhodium but I have also read in the same Midas manual that Zinc alloys will contaminate Rhodium even with a pre-plate. All Brass and Bronze that I have seen has Zinc in it. Can I plate over Brass that contains Zinc without contamination?
Mark Visbal

2006

Hi Mark,
Yes, zinc as a contaminate is a definite problem in your Rh bath. If the Ni pre-plate is thick enough I don't see how you could still get zinc into the bath. If you could plate the piece .0002" in Ni to give you adequate coverage over the brass, you should be fine. Good Luck!
Mark Baker

2006