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Rhodium plating deposition per amp-hour

dear sir,
we are doing white& black rhodium plating [adv: black rhodium plating solution on eBay or Amazon [affil links] on our jewelry products. We want to know the rate of deposition per ampere hour of rhodium. We are using acid base proprietary chemical in our process. Please help us in this matter, we shall be thankful to you.

thanks
regards

Mahesh Aggrawal
employee in jewelry company - Jaipur Rajasthan India
February 18, 2011

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Hi, Mahesh

There is a simple relationship for this called Faraday's Law of Electrolysis. At 100 percent efficiency, one coulomb (96,485 ampere-seconds) will deposit one gram equivalent weight of metal. Look up the molecular weight of Rhodium in the periodic table, divide by its oxidation state as an aqueous salt (+3), and you have how many grams will be deposited by a Faraday assuming 100% efficiency. Check with your supplier for the usual efficiency of their bath.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 18, 2011