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topic 50375

What is proper Rhodium Plating Thickness and how to measure it?


October 25, 2008

Q. I am working with a jewelry company as production In charge. We export to US and middle east market. One of my customers has asked us to specify the thickness of Rhodium plating that we are giving to white gold articles. I have a rough estimate of 0.5 micron but cannot say exactly the thickness of plating. How to measure the thickness of microplating? To what extent can the thickness of rhodium plating be increased?

Dinesh Kumar Sinha
Jewellery manufacturer - Mumbai, Maharshtra, India


October 29, 2008

A. Hi, Dinesh. 0.75 to 1.0 micron should be practical if you are looking for thicker plating. Considering the very high cost of rhodium, good instrumentation such as x-ray fluorescence should be justifiable.

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


January 6, 2009

A. Hi Dinesh,
You may measure the thickness as Ted said.
Usually for plating precious metals like gold, platinum, Palladium, Rhodium etc. it is always good to know the wt. in mg deposited on 1 dm square, for one micron. By this you can be sure how much worth in rupees of metal is deposited. This can also be considered as countercheck. For gold it is 178 mg/dm2/micron, Palladium it is 90 mg/dm2/micron and Rhodium, I understand deposits 40 mg/dm square to give one micron. If I am not confusing you, I will give a calculation as below:
Generally Rhodium is deposited @ 6-8 mg/amp-minute @ about 2 grm/ltr Rh in the bath.So if you back calculate you can get the time required to get 40 mg/dm2 and that will be equal to 1 micron.
Thus you can fix rate for the thickness to the customer with ease.
Best of luck.

t k mohan
T.K. Mohan
    plating process supplier 
Mumbai, India




April 8, 2011

Q. We are a manufacturer of high quality jewelry based in Gujrat India. We have been asked by our client to deposit between 3 to 5 mils thickness of rhodium on our jewelry products. We have always deposited rhodium in milligrams. Can you please advise me how many milligrams of rhodium is equal to 3 to 5 mils?

Thanking you in advance

PARESH PATEL
PROPRIETOR - NAVSARI, GUJRAT, INDIA


May 2, 2011

A. Mils in this context is a slang term being used by some and they usually mean millionths of an inch. They probably want 0.1 micron thickness of rhodium, and milligrams is a weight and will not tell you the thickness of your plating unless you also know the surface area.

Neil Bell
Red Sky Plating

supporting advertiser
Albuquerque, New Mexico
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September 20, 2012

Q. My company sells high quality costume jewelry. When I wanted to know the micron quantity of the products from one of our producers, he told me they plate it with "3U rhodium". I never heard this unit before, can anyone help me?

Theresa Berger
- Vienna, AUSTRIA


September 22, 2012

A. Maybe his "U" means "µ" = microns.

But 3µ thickness is very high for rhodium plating. You can have problems of cracks with such an high thickness.

Best regards ;)

François Pignon
- France



September 28, 2012

A. Servus, Gruss Di, und Hallo Theresa.
In my experience plating costume jewellery for Nina Ricci we found plating rhodium over gold to ascertain minimum thickness proved to be 0.000001" (at this thickness no gold colour was present). We decided to plate 0.000003" rhodium minimum to ensure quality. The gold thicknesses were 0.000008-0.00001 as a norm. I believe the "U" is designation for MICRO/MILLIONTHS of an inch. This would be 0.077 microns. For costume jewellery this would be enough to ensure the items retain their brilliance under normal wear (no abrasion, mechanical or chemical).
Servus!

Eric Bogner
- Toronto Canada



March 22, 2013

Q. Hello,

I wonder if someone can help me over here.

I am looking to manufacture my jewellery collection and very confused regarding the following.

What base metal should we use to achieve quality? Copper or Alloy.

Specifically we want to use 18k White gold plating. Over here, what would you recommended the thickness of the plating to be? Someone suggested 0.03 µm or 0.1 µm.

Quality is very important to me and your suggestions are as well :)

Many thanks,
Gee

Gaurav Jaura
- London, England


A. Hi Gaurav. I could be misreading your inquiry, but I'm not confident that white gold (8N) plating is really what you are looking for. May I request that you review our FAQ, "Rhodium Plating and White Gold" and then clarify if you still are looking for white gold plating? Eric's posting right above yours gives some good info on thickness of the plating. Thanks.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



June 12, 2014

Q. Dear Sir,

Currently we are manufacturing silver jewellery and we do rhodium for all our jewellery as it is required by our customer.

How do we measure the rhodium plating thickness manually?

How do we measure the silver plating and silver anti tarnish coating also manually?

Please advise what is the calculation for this procedure.

regards,
Sundaram

SUNDARAM VISWANATHAN
JEWELLERY MANUFACTURING - JAIPUR INDIA


June 2014

A. Hi Sundaram. I think there is little possibility of measuring the thickness of rhodium anti-tarnish plating on silver costume jewelry "manually" -- which I interpret to mean with a micrometer or like instrument. And viewing it by metallographic cross-section sounds quite unlikely unless you run a world-class lab.

It is probably possible to track thickness with an x-ray fluorescence machine, but these are expensive, so suitable for manufacturers but not for custom jewelry designers. The most practical technique is probably as described by TK Mohan; for background:

Metals are electrodeposited in proportion to the applied ampere-seconds, as discovered by Faraday with his Law of Electrolysis. 96,485 ampere-seconds (coulombs) deposits exactly one gram equivalent weight of metal if the bath is operating at 100% efficiency. From the valence state and atomic weight, you can determine exactly how much weight you have deposited; and from the density of the metal, what volume you have deposited. Dividing by the surface area of the work, you can determine the thickness. All of this conversion effort can be saved by going to the "Electrochemical Equivalents" appendix in the Metal Finishing Guidebook, which incorporates all those conversion factors for you and offers the answer that it takes 22.9 ampere-hours per square foot to deposit 0.001" of rhodium and 6.2 ampere-hours to deposit 0.001" of silver.

But most plating baths do not operate at 100% efficiency. In this case Faraday's Law of Electrolysis still holds but a portion of the ampere-seconds are going towards liberating hydrogen from the water of the plating solution instead of depositing silver or rhodium. TK suggests that you can determine the efficiency that you are operating at, or simply incorporate the efficiency into your calculations, by measuring how much rhodium you deposit once (or periodically), and then know how much rhodium you are depositing on your jewelry by simply applying a scaling factor to your ampere-seconds measurement. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



August 21, 2015

Q. Hi,

I am starting a Jewelry line that with brass base metal and rhodium plating. I have been advised to use 0.075 microns of rhodium plating on my jewelry, and that this will last up to 1 year with normal wear.

Is this a normal thickness to use, or should I go thicker?

What are companies like Swarovski's jewelry plated at? Similar?

Thanks in advance,
James

J C Little
- Toronto, ontario, Canada


Swarovski jewelry

August 2015

A. Hi James. Per an ad on Amazon, Swarovski electroplating is "3MIL". They claim that over 90% of jewelry suppliers plate 3X thinner =>

To electroplaters, 3 mil means three thousandths of an inch but, as Neil notes above, jewelry manufacturers mean 3 millionths of an inch, not 3 thousandths, and that's quite close to your 0.075 microns. Even at that, it's pretty thin: a pair of standard dice cubes of plating metal would cover about two thousand square feet of jewelry :-)

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


August 24, 2015

A. Good day James.

Rhodium @ 0.075 microns = 2.55 millionths of an inch is very good for pins, brooches, and items which do not receive any mechanical wear.
A bracelet or a ring or a pendant will not have the same "wear ability", due to mechanical abrasion factors, and acidity of the skin reacting with the base metal/substrate.
I do not know your process, but brass/copper alloys as substrates for jewelry to be rhodium plated, must be given a hard, lustrous barrier coat of metal to produce a shiny, hard surface to retain the quality and brilliance of rhodium plating.
In the past, acid copper and nickel plating was predominantly used prior to rhodium.
Nickel plating does pose health risks, (regarding dermatology) as it is banned in Europe.
A barrier plating of palladium (or other metal) instead of nickel is often used prior to rhodium.
Hope this is helpful and good luck with your endeavor.

Regards,

Eric Bogner
Lab Tech. - Whitby, On, Canada



June 29, 2017

Q. If we are wanting to produce some high end sterling silver jewellery (925) and want a good luster, finishing and durability of our product. Then what could be the best thickness of rhodium plating. We are also wanting to know the rhodium plating procedure and thickness used in Bangkok 925 sterling silver jewelry.
Regards,

Arun Sehgal
- Panipat, Haryana, India.


July 2017

A. Hi Arun. You can ask Bangkok 925 what thickness of rhodium they apply and their procedures; they may tell you, although I think they might keep certain steps confidential. You can also test it to find the thickness. But to post responses about what one particular supplier does could drift towards assisting in industrial espionage, and sorry but we don't have time to carefully audit such a discussion :-)

Courtesy of Metal Arts Specialties, we have a detailed article about rhodium plating of jewelry for download in our on-line library here; although it is actually directed at rhodium plating on white gold, it should answer your questions. Good luck!

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


July 20, 2017

A. The test that Ted mentions is usually done by X-ray fluorescence and our experience is that 0.1 micron to 0.2 micron of rhodium will provide good wear resistance on sterling silver jewelry.

Neil Bell
Red Sky Plating

supporting advertiser
Albuquerque, New Mexico
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