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How to blacken Nickel electroforms

Q. 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
2004

A. Dip in 50% nitric acid

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2004

A. Black patina for nickel:

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

Goran Budija
- Zagreb,Croatia
2004

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

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2004

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

Raffi Garabedian
- Monrovia, California, USA
2004

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

A. Black for nickel:

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

Goran Budija
- Cerovski vrh Croatia
2004

Q. 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
April 29, 2011

A. 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.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 29, 2011

Q. We need to blacken nickel electroforms. We tried your advice but we couldn't. Also, we tried blackening with a liquid antique chemical called black 508.
We did electropolishing on the part before the process and then activated with sulfuric acid. (Nickel electroform blackened in 30 seconds.) However, black oxide layer didn't adhere to nickel surface. What can we do about it?
Thanks for your advices.

Ecem Gore
- Ankara, Turkey
January 24, 2019

A. Immersion in 25% nitric acid will blacken the nickel, although it may not be jet black. There are commercially available processes which will blacken the nickel.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
August 10, 2019

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