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Discoloration on Rhodium Plate


#1

I haven’t found an answer to this problem. Our company manufactures laser engraved keepsakes in various metals. Most common is sterling silver, which we Rhodium plate. We also Rhodium plate white gold and brass display pieces. I’m trying to troubleshoot results. On occasion, one of the Jewelers will have pieces with milky areas after the final Rhodium bath. The other problem is brown stains after the final plating. I’m pretty sure the brown stains are caused by insufficient rinsing between baths.

Our usual process for precious metals is Electrocleaner>Rinse>Palladium>Rinse>Rhodium. Brass display pieces include an Acid Dip after Electrocleaner. We work at room temperature and plate up to a dozen pieces at a time.

The process was developed by Jewelers before me. I’m trying to get an acid bath and distilled water instead of filtered water added to all plating runs. The milky discoloration is not usual, the brown stains more often, but not usually.

Any thoughts or explanations?


#2

Ruth Annie
I am by no means an expert but have been doing my own plating for 35 years and rhodium can be tricky. I always use distilled water for all solutions and rinses. I never reuse wires wire that connect piece to rectifier. I always heat solutions to manufacturers specs. Finally about every 50 plating or so I start with all fresh solutions Also use a product from Rio Grande called Midas carbon treatment for rhodium. It removes organic contamination in liter batches.
Hope this helps
Franz