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Black and white rhodium plating on the same item

June 20, 2012

Q. Hello,
This is a production jewelry application over sterling silver. Any reason why we can't do both rhodium colors on the same piece? I am assuming we must mask/stop off areas not to be plated and do it in 2 steps. Is this correct?
Any advice is most welcome. I really enjoy this forum...when I have time to browse. It's always helpful thanks to Ted and everyone who answers.

Carole Jones
designer - Dartmouth, Nova Scotia, Canada

First of two simultaneous responses -- June 21, 2012

A. Hi Carole,

What I do when I have bicolor black and white articles to plate :
- plate the white Rhodium all over the article
- plate the ruthenium all over the white rhodium
- mask the part of the article you want to be in black with a sort of painting ("goudron" in French, seems to be "tar" in English)
- do anodic degreasing in a 50 g/L KOH solution : this will easily remove the ruthenium on all the parts which have not been masked by the painting
- use CH3Cl2 to remove the painting
- then you have a bicolor black and white article

Best regards ;)

Francois Pignon
- France

Second of two simultaneous responses -- June 21, 2012

A. If you plate rhodium over silver without a palladium or nickel barrier, the silver will walk right through the cracks in the rhodium and corrode on top.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina

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