Metal finishing Q&As since 1989

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Electroless Nickel Bath strip w/HNO3 followed by Sulfamic acid

2005

When we strip our electroless nickel tank we have used a 3% nitric acid strip and it is suggested to do a final rinse with sulfamic acid.

https://www.pfonline.com/articles/109802.html

"To prevent the effects of nitric acid contamination, it is good practice to use a final rinse of sulfamic acid in the EN tank prior to making up a new solution. How much sulfamic acid do we need to add to the final rinse?"


"To prevent the effects of nitric acid contamination, it is good practice to use a final rinse of sulfamic acid in the EN tank prior to making up a new solution."
How much sulfamic acid [on eBay or Amazon] do we need to add to the final rinse?

Thomas Brown
Plating Shop - Colorado Springs, Colorado, USA

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First of two simultaneous responses --

I disagree with that proposed practice. It will add another chemical compound to your already complicated water treatment system. I would suggest to just wipe clean the tanks with clean rags to eliminate the last traces of nitrate bearing rinses. Then dispose accordingly as dry stuff.

Guillermo Marrufo
Monterrey, NL, Mexico
2005

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Second of two simultaneous responses --

I was trained to use a dilute ammonia [on eBay or Amazon] solution to neutralize the HNO3 followed by a DI rinse.
Why do you strip with such a dilute nitric solution. 10 or 20% is so much faster and has little or no effect on the tank. It can be stored and reused until it is no longer effective and then is waste treated.

James Watts
- Navarre, Florida
2005

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I suggest using 10-12% sulfuric acid (vol)and hydrogen peroxide or sodium peroxide to strip the nickel. It works well and no nitric acid is involved. Water rinsing will remove the residual stripping solution. If there is a small residual, a dilute ammonium hydroxide rinse will take care of it.

Don Baudrand
Consultant - Poulsbo, Washington
(Don is co-author of "Plating on Plastics" [on Amazon or AbeBooks affil links]
           and "Plating ABS Plastics" [on Amazon or eBay or AbeBooks affil links])
2005

I am very interested in the nickel stripping method mentioned by Mr. Don Baudrand. Shall I have more detail about the stripping method? What is the percentage of the hydrogen peroxide in the stripping solution? What is the stripping temperature and duration? If my plating tank is 316 stailess steel, whether this stripping chemical is suitable or not?

Li Juan
- Singapore
2006