Stripping nickel and copper
Q. We want to find out an easy way of de-plating nickel (40 micron) and copper coating An anodic treatment of sulfuric acid with 6 V using lead anodes was suggested earlier, however I need more details or alternative solutions if there exists.
In addition would you please let me know how to provide health and safety rules, any gases coming out might cause big problems.
plating - Istanbul
A. The most effective process for stripping nickel and copper from steel is a hot solution of Sodium Cyanide, Nitrobenzene Sulfonic Acid and Sodium Hydroxide. Unfortunately, as you probably already know, this will be an extremely toxic solution that will be difficult to treat. The solution becomes saturated with chelated ferrocyanides and complete oxidation of cyanide is nearly impossible. The solution has a very high tolerance for metal and will last for a long time before dumping is required. It also will strip nickel and copper back to the base metal. Unfortunately the toxicity is very difficult to work around. Check with your local regulatory authorities to see if this is legal in your area.
Conversely, the sulfuric acid strip will only strip nickel. It will not strip copper. It is a relatively slow process and it can also lead to severe etching of the base metal. Small additions (1 oz/gal) of glycerine inhibits the etching problem. If you want to strip down to the steel, you will have a much more difficult time using sulfuric. You will probably have to remove the copper using mechanical means (polishing or abrasive blasting.)
There are some proprietary stripping agents that are more expensive and less effective than the sulfuric or the cyanide processes, but they tend to be much more environmentally benign. I would investigate that are available in Asia or Eastern Europe.
Good luck, what you're trying to do is tougher than it was 25 years ago.
Daryl Spindler, CEF
decorative nickel-chrome plating - Greenbrier, Tennessee
Your answer concerning the stripping of nickel is really interesting, may I have just a detail: what is the concentration of the acid (%) and what is the temperature of the acid during the stripping?
I thank you very much for your answer.
- Martigues, France
Remove Residual Nickel Plating after BlastingJanuary 20, 2020
Q. Hello all, I work in the aerospace industry and we deal with a situation call Residual Nickel. We do a Nickel Strike and Copper plate process prior to HT. Once Heat Treat is complete we strip and blast to remove residual Copper/Nickel. This process is not always successful so we have added a process check to inspect for residual nickel. The obvious issue we want to deal with is why were not able to successfully remove the Copper/Nickel during strip/blasting. The method we use to inspect for residual nickel is Nital Etch. Obviously there is no value added there. We would definitely like to stop using this process to detect the nickel and use something more cost effective/easier detection method. I'm looking for suggestions on how to strip and remove 100% of the copper/nickel or A easier method to detect for residual nickel at the process. Appreciate all feedback.
Northstar - Bedford Park, Illinois
A. Hi Bob. Apparently there is something to be said for non-acid copper plating processes :-)
If you need freedom from residual nickel, the best approach might be to not apply it in the first place. Maybe send sample parts to someone like EPI (Electrochemical Products Inc.) [a finishing.com supporting advertiser] who can try a proprietary copper plating process, or a pyrophosphate, or even a cyanide copper plating process before your heat treatment. Decades ago the plating supplier I was with at the time installed mass production lines for pyrophosphate copper plating of tools and subsequent removal and recovery of the copper after heat treatment.
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Striving to live Aloha
January 22, 2020
Q. Hello Ted Mooney, thank you for your response. We are working to Boeing Specification BAC5722 and are required to Nickel Strike prior to Copper coating. Unfortunately, removing the nickel strike is not an option. Any other suggestions will be greatly appreciated.Bob Foster [returning]
Northstar - Bedford Park, Illinois