Letter 33081

How to blacken Nickel electroforms [California] 

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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, Ca, USA

Dip in 50% nitric acid

Jeffrey Holmes, CEF - Spartanburg, SC, USA

Black patina for nickel:

       o,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

Try 0.5g/l potassium thiocyanate with 25ml/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 - UK

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

Raffi Garabedian
- CA, USA

Ed. note: You are certainly welcome, Raffi, but the very best way to thank the kind responders is to let us all know how things worked out after you try it.

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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