Strip (remove) Copper Plating from Steel

A. Hi Mark.

Decades ago my employer (M&T, now Atotech) installed two programmed hoist lines at a well known tool supplier to the oil-drilling industry in Houston Texas. The first line was for applying pyrophosphate copper plating to the tools before nitriding, the second line was for stripping it off after nitriding. Interestingly, the stripped copper was going to be recovered and reused in the first line. I was a young engineer designing & installing equipment with no knowledge of the chemistry, so I don't know what the stripping solution was, nor if the re-use of the copper actually worked out.

But I can assure you from this experience that reliable, continuous, high-production stripping of copper from heat treated parts can be done. Since recovery & reuse of the copper was planned, most likely the process was electrolytic. I've appended your inquiry to an earlier thread suggesting some alternative stripping solutions, and hopefully some kind & knowledgable soul will chime in ... because the only thing I recall from my visit 55 years ago is that a heat treatment plant in Houston in the summer was so damn hot you absolutely would not believe it  🙂

Luck & Regards,


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

A. Hi Mark,

A long, long time ago, when I was first starting out in the electrochemistry world, I developed a method of electro-stripping, a method was also patented by Lea Ronal back in the early 1990s, based on the same type of chemistry.

The solution was based on the pyrophosphate solution for copper plating, with the copper pyrophosphate not added, scrap copper anodes recycled as cathodes and the part made cathodic. Stripping times were down to 1-2 hours, and we had a stripping solution that lasted up to 5 years, rather than 6 weeks (as it was at the time, when using cyanides and proprietary salts in a purely immersion process). It cut down on process time and waste at the time.

You guys have made me realize that (to the best of my knowledge) no book has ever been written about stripping. With so many platings, so many substrates, so many situations, I bet I'm not the only one who would love to see one.

Luck & Regards,


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

Hi Mark,

It's pushing my memory a bit, but is based on a typical copper pyrophosphate plating solution, minus the copper pyrophosphate, so typical make up would be around:
Potassium pyrophosphate - 150 g/l
Potassium nitrate - 2 g/l
Ammonia (concentrated) - 1ml/l
Temperature - around 50 °C
Current density - typically 1-2 A/dm2, but if memory serves me right, stripping could be accelerated by increasing the current to 5 A/dm2 without damaging the base material (never completed fatigue testing at that removal rate, so treat it with caution, although there is no reason I can think of for there to be an issue).

A. Immersion in ammonium hydroxide (ammonia water) will dissolve copper in a short time and will not affect the nickel alloy. Odor is very strong and irritating, and disposal must be done in accordance with your local laws.

A. Try adding about 2-4% of 35% hydrogen peroxide. Jeffrey Holmes, CEF Spartanburg, South Carolina A. One micron of copper should be no problem to ammonia (should remove it in less than one hour). If it is not working then it is not copper or has something else on top of it. Another possibility is to use anodic treatment part is (+) stainless steel is (-), 6 volts and 30% alkali in water (sodium or potassium hydroxide) but again this may not work if ammonium didn't. Guillermo Marrufo Monterrey, NL, Mexico

A. You can use 150 gm sodium sulfide/15 gm sulfur/1 lit water solution (20 °C temp.)!

Good luck!

A. Sodium or Ammonium persulphate will work very well.

A. Your supplier can suggest a safe copper stripper. Or, as Mr. Lee mentioned, you can use persulphate as it etches copper. Or you can also go for mild hydrochloric acid with ferric chloride ⇦ this on eBay or Amazon [affil links] for slow stripping, but be careful since it is highly corrosive mixture.

A. Hi Mike.

Some suppliers have offered copper bright dipping systems which used sulphuric acid and peroxide at high temperature, with a slipstream recirculated to a cooling system to remove precipitated copper sulphate, to allow continuous or at least extended use of the stripping solution by removing the copper. Whether this has any hope of being helpful with ammonia and peroxide I don't know  🙂

Luck & Regards,


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

A. Looking at the various options suggested in this thread over its lifetime, I think the persulphate option is still the least hazardous. (It ships hazmat due to being an oxidizer but isn't noxious to work with.)

(Adv.)
Please feel free to contact me if you are interested in a source for this.

A. Why not try putting a few handfuls of sand in the tank with some water and agitating it in sone way, even manually.

A. Hello Mike
There are a few proprietary strippers based on Nitrobenzene sulfonate salts. They are frequently marketed as Nickel strippers. When those strippers are mixed with Sodium Cyanide or some other alkaline salts, they will strip Nickel, Copper, and some other soft metals from steel (without damaging steel). Heating of the solution may be required. Try to contact your chemical supplier.
Also, it is possible to strip Copper electrolytically at 5-6V anodic (reversed) in a diluted mix of Sodium Cyanide and Sodium Hydroxide. Please note: any work with Cyanides requires relevant safety measures due to toxicity.
Good luck,