better than beer 
actually a fruit
juicing operation 
the process has no effect on sound plating of any kind, even paint if it's not already rusted beneath it, sound cadmium should come out looking like it did previous - I used a few pieces of galvanized metal for splash deflectors in the washer, and there's been no effect on them
the electrolytic process with sodium carbonate is as gentle as you can get, it has an effect on iron oxide and black rust only - try it on some excess plated parts if you have them
if you want to get real technical about preservation of metals
see here, files 9-15 - should suit your penchant for detail
Bill
