plating, anodizing, & finishing Q&As since 1989
STRIPPING COPPER PLATING
Q. WE MANUFACTURE VERY PRECISE AIRCRAFT ENGINE (JET) SEALS FROM 17-4PH STAINLESS STEEL. THEY ARE COPPER PLATED 0.4 MILS MIN.IN SELECTED AREAS TO PREVENT NITRIDING. AFTER NITRIDING THE COPPER IS STRIPPED IN A NON-ELECTRIC (IMMERSION) SODIUM CYANIDE SOLUTION.
WE ARE LOOKING FOR A NON-TOXIC, NON-ETCH REPLACEMENT.
DOES ANYONE HAVE A SUGGESTIONS?
GENERAL MACHINERY & MFG. CO. - chicago, Illinois, USA
A. Lloyd - A great way to strip off the copper plating from SS is to use a peroxide-based stripper. No electricity is required and the process can take as little as 2-5 minutes. Check out our website for information on our line of Laser products. Good Luck.Dan Brewer
chemical process supplier - Gurnee, Illinois
A. I do not think you can find a really non-toxic alternative, but using cyanide-base solution is not required. You can use oxidizing acid like a standard passivating solution (any one recommended for the PH stainless steels), or simply a 50% nitric acid (room temperature), chromic acid, etc. Make sure the parts are well degreased prior to treatment with oxidizing acids.
Regards, MaxMax Stein
captive metal finisher - Montreal, Québec, Canada
To: Lloyd Steirer:
We manufacture a copper stripper that is very effective in stripping copper from steel and stainless steel. It was developed in response to a request from Boeing Aircraft and has been approved for use by Boeing (spec #BAC5771. It DOES NOT etch stainless steel, has a pH of 10.2 - 10.8 containing no acids nor cyanides. It is a one-component powder that is mixed with tap water and used at room temperature. This is a low-voltage electrical stripper with an extremely long life. Phone, fax or e-mail me and I will forward literature and lab sample for your in-house testing. Regards, Gayle
Metalx Specialty Products / Ronatec
To minimize searching & thrashing, multiple threads were merged; please forgive repetition, chronology errors, or disrespect of other responses (they probably weren't there) :-)
Removing Copper Plating from Stainless Steel2007
Q. We have been painting stainless steel hinges for some time. One of our customers asked us to also pretreat their hinges by passivating. We took them up on it and have been doing so for a couple weeks using copper sulfate for a drop test to confirm the stainless steel is passive.
We have had a couple failures which results in the copper sulphate plating out copper on the part. We have been able to remove most of the copper by wiping, but this is not 100%. We would like to strip the copper without damaging the stainless steel; we process 302 and 304 stainless steel.
Is there a way to do this?
Plating Shop Employee - Madison Heights, Michigan
A. Very few things are more easy, than remove copper from stainless steel, diluted nitric acid will easily do the trick, and steel will only be "more" passivated.Bo König
- Odense, Denmark
A. Nitric acid solutions work well.Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
A. Persulfate will do the trick.
Stellar Solutions, Inc.
A. All the above answers are satisfactory because you are talking about hinges. But for critical and delicate surfaces, if the acid copper stains, it means that some material from the surface was lost and the surface is immediately damaged from the moment it is stained.Guillermo Marrufo
Monterrey, NL, Mexico