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How to blacken Nickel electroforms

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We electroform pure nickel in polymer molds. I am looking for a Ni surface treatment that can be used to significantly "blacken" the nickel surface. We can not use plated Ni Black as we have other metals in our system (Cu in particular) that we do not wish to deposit on. Does anyone know of a chemical or electrochemical surface treatment that can blacken the Ni by a conversion process?

Thanks in advance for your advice.

Raffi Garabedian
- Monrovia, California, USA

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++++ Dip in 50% nitric acid Jeffrey Holmes, CEF - Spartanburg, South Carolina

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Black patina for nickel:

0,5 gm potassium sulfocyanide
5 ccm sulphuric acid
25 ccm sodium peroxide
Cold immersion (15° C, 15 minutes). Use only fresh solution!

Goran Budija
- Zagreb,Croatia

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Try 0.5 g/l potassium thiocyanate with 25 ml/l of 10% sulphuric acid and 25 ml/l of 20 Vol hydrogen peroxide. Use at room temp for 2-6 minutes.

Trevor Crichton R&D practical scientist The Pheasantries - Chesham, U.K.

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I'd like to thank both the administrator of this web site and the kind responders for their suggestions.

Raffi Garabedian
- Monrovia, California, USA

Ed. note: You are certainly welcome, Raffi; a generous way to thank the responders would be to remember to let us know how things worked out after you've tried it.

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Black for nickel:

0,5 gm potassium thiocyanate
5 ccm sulphuric acid 25 ccm hydrogen peroxide Cold immersion (15° C, 15 minutes) Use only fresh solution! Good luck!

Goran Budija
- Zagreb, Croatia

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April 29, 2011

Can anyone recommend a source for these chemicals in small, affordable quantities? I have a small project on which I need to darken some nickel-plated hardware, and found this thread on Google...

Thanks for any help.

Courtney Ballard
- Gaston, South Carolina

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April 29, 2011

Hi, Courtney

Fisher Scientific, VWR, and Aldrich Chemical are three lab supply companies accustomed to selling chemicals in very small quantities. Please let us know if it works out.

Regards,

Ted Mooney, P.E. finishing.com Brick, New Jersey