Stripping copper plating from stainless steel

"Electroplating Engineering Handbook"
by Larry Durney

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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. Good Luck.

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, Max

To: Lloyd Steirer:

adv.
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

A. Copper is readily attacked by alkalies; hence, a hot sodium or potassium hydroxide solution will remove the copper quite easily, especially in conjunction with ultrasonics. The high pH will have little or no effect on most stainless.

Waste disposal: The copper hydroxide will be the bluish sediment in the stripping solution after the reaction is over. As long as the pH is high, the stripping solution should will not have a lot of residual copper. After the copper hydroxide settles out, decant the clear liquid off of the sediment--if the copper concentration is low enough, you can dilute it and dispose of the liquid. You can either dry the remains and properly dispose of the copper hydroxide (toxic), or you can treat the remaining precipitate as is; the copper hydroxide will dissolve in acids--you can adjust the pH of the remaining (solution + precipitate) with HCl to make copper nitrate. Then, you adjust the pH back to neutral with baking soda [in bulk on eBay or Amazon [affil links] or whatever you have lying around. The Copper nitrate can be disposed of via your normal hazmat provider. You can go one step further & roast it in air at 250 °C or so to make copper oxide, but that is just more mess and hazmat to worry about.

Was this too much info?

A. Nitric acid would remove the copper a lot faster and at room temp. Down side being nitrous oxides you need a fume cupboard or extraction.

A. John -

Another way of stripping the copper is to use a peroxide/sulfuric acid blend. The solution runs at just above room temp and doesn't generate the fumes of some other methods. It also creates copper sulphate as a precipitate and the peroxide is easy to waste treat.

A. Very few things are easier than removing 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. Persulphate will do the trick. Ray Kremer Stellar Solutions, Inc. McHenry, Illinois

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.