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pH drop in Nickel Electroforming.

Dear Sir/Madam,

I am electroforming Ni using a sulphamate process and am unable to obtain a rise in pH after each run. I am using Inco s-rounds and have added 3 g/l of chloride to the bath, (to help dissolution) which I feel is the upper limit as I do not want the stress to increase. The pH drop is typically 0.1 after about 3 hours plating at 50 ASF. Also, the s-rounds were activated in sulphamic acid before use. Could anyone give me a hint as how to remedy this problem? Thanks in advance Mike

Mike Miller
- Sainte-Foy, Canada
1999

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You should see a pH rise as nickel plating takes place. The bath is less efficient at the cathode than the anode, so there is net consumption of free acidity and a rise of nickel concentration in the bath (ignoring dragout).

Bill Vins
microwave & cable assemblies - Mesa (what a place-a), Arizona
1999

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February 25, 2009

Hi, Mike. To expand a bit on Bill's reply, the reason you use S-rounds and/or chloride is to improve anode efficiency and thus slow the rise of the pH. If you are seeing the pH drop, which may be due to dragin, one thing you could do is substitute some pure nickel anodes or lower the chloride content.

Regards,

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