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Electroplating brass wedding bands with Copper-Nickel-Rhodium

March 5, 2010

Hello, we are manufacturers of fine wedding bands. Due to the economy, we are mass producing brass samples for our retail clients to display in their showcases. We want the rings to be bright rhodium colour (white) as possible and we are having a lot of difficulty achieving a high level of whiteness.
These are the steps we are taking to plate:
We are using an 'unknown metal' racks ( 2 different kinds, which incidentally have different results.)
Clean the brass rings in warm ultrasonic. ONLY for a short time ( about 1 minute, or the brass goes brown)
Rinse with tap water, steam very well.
Put into electro cleaner for 1 minute (not heated)
Rinse, steam.
Copper plate for about 20 -30 seconds.
(At roughly 40-50 degrees temperature) We are using a 'homemade' plating set up where we have brass tubes which inject steam into the copper and nickel solutions to heat them up and we see the temperature on a thermometer)
Rinse, Steam.
Nickel for about 10 to 20 seconds.
Rinse.
Repeat Copper.
Rinse, steam.
Repeat Nickel.
Rinse, steam.
Rinse again in distilled water.
Rhodium plate for about 20 seconds. (not heated)
Rinse steam.

These are the problems we are having:

Final finish looks dark, not brite white. It looks greyish.
Unknown metal rack 'A' makes rings look dark grey-ish.
Unknown metal rack 'B' makes rings look dark grey-ish with a yellow tint.
Rack 'A' leaves darker grey stains on the inside of the ring where the hook was touching.
Rack 'B' Leaves a dark yellow stain where the hook was touching.

I do move the rings around to try to avoid these stains, to no avail.

Other problems are:
Cloudy stains
Stains with a black outline.

We have tried different approaches:
Keeping all hooks clean
Keeping rings clean
Keeping electrical clamps clean
Keeping anode/cathode clean
Tried different times in solution
Tried different Temperatures
Tried different hooks.

If anyone has any advice on this, please HELP!

Thank you,

Candace

Candace Berriche
Employee of Manufacturing company. - Montreal, QC, Canada

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Hi, Candace. Hopefully someone can offer you all the detailed advice you need, but please don't hold your breath. Virtually no one in the developed world attempts to design their own plating equipment, process, and chemistry these days. If I am understanding you and that is what you have done, you need to either retain a highly experienced plating consultant to figure out what is wrong or, at the least, invite a vendor of plating chemistry in to install proprietary plating processes.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 5, 2010

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You are doing several things wrong. first tell us whether the brass is "leaded" -does it contain lead, if so come back and we will tell you how to fix that main problem. Meanwhile, turn off the steam, use electric immersion heaters. Then re-submit a list of the problems along with the cycle. We can fix this by email (as much as I would like a trip to Montreal)

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

March 8, 2010