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Stripping Chrome From Old Car Parts

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I am looking for a way to strip chrome plating from old car parts. I have been grinding,but this is a long difficult process. I found a method that uses NaOH, but I can't seem to make it work. I am quite sure that I am dealing with chrome and not stainless, because it has rusted. Anyway, what I have tried a few times is, I have made a bath of water and NaOH (Red Devil LYE), which the piece to be stripped is placed in. I then connected a six volt positive source to the piece and the negative to the bath container. The bath bubbles, which I think is the water electrolysing. I am using about 6 or 7 oz of LYE to a gallon of water. I have tried this with the bath at about 30 F and 70 F. I have left the piece in the bath for 5 or 6 hours with no effects to the chrome. What has happened is once the water turned green, I thought maybe some copper was dissolving. I was a little optimistic of the green color because I think that Cr2O3 is green, but there were no signs of the chrome being removed from the piece. Another time a black residue appeared on the piece, I thought that maybe some aluminum may have caused this. I am not having any luck getting the chrome off. I must admit that I don't understand the chemistry of this. I am guessing that the water ionizes the NaOH and the positive charge attracts the OH to the chrome, but how does the OH react with the Chrome, I don't know. I know that there are three oxides of chrome that are stable, 2+, 3+ and 6+. Apparently, the Cr2O3 is the most common, so I guess that this is what would happen, but where does the oxide appear? Does it go into solution or does it plate the negative surface? I'd like to make this work, but I'm a little lost.

Michael Z deleted
- New Berlin Wisconsin


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Try this: 7 oz/gal NaOH, 9 oz/gal Na2CO3. Use at room temperature, 6 V, with a steel cathode (make the workpiece to be stripped the anode).

totter James Totter, CEF
- Tallahassee, Florida


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Well, if the part is rusting, it's steel not aluminum, so that part is settled. Steel is magnetic, of course, while aluminum is not, so that's another easy way to tell. It's an important distinction because the NaOH would quickly destroy and dissolve an aluminum part.

Mr. Totter's chemistry sounds like an improvement, but you admit you don't know what you're trying to remove, and there may be the rub. Decorative chromium plating consists of about 20 millionths of an inch of chromium, plated onto a nickel layer which is hundreds of times thicker. To the untrained eye, nickel looks so much like chrome that it could be fooling you.

My theory is that you removed the chromium a long time ago and are now looking at the nickel plating. Of course, my response begs a follow-up question, but I'll wait for you to ask it smiley

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


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First, I want to thank both of you for your response. I seem to agree with Ted that maybe the chrome is long gone. Do you have any thoughts about the colors I saw in the Bath? I did see some black residue and then some green. Anyway I did read somewhere that the chrome used in these instances is very thin and I did know that there was nickel under the chrome. Some of the info I did read also stated that there may be copper under the nickel. One reason that makes me think that the chrome is gone and what I am looking at is Nickel is that the original finish was dull and after the piece was in the bath it became very lustrous. This may be the nickel. You seem to imply that the process that I was using to remove the Chrome (NaOH reverse plate) may not work on the nickel. Do you have a suggestion for this? Again I do appreciate the time.

Michael Z [returning]
- New Berlin, Wisconsin


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There may or may not be copper under the nickel, based on the age of the part and its quality.

Even under carefully controlled conditions, speculation based on a color observed by another person is a weak investigative tool, Michael. In this case--no offense intended, but you admit you're not positive if you're working with steel, stainless, or aluminum, and whether there is an undercoating of copper, etc.--I think speculation on the cause of a recalled black or green color can't contribute much of value.

Yes, I did imply that you can't remove the nickel this way, now I'll state it outright: it won't work. You will need to buy industrial chemicals containing either cyanide or proprietary ingredients to chemically strip nickel off of steel. The banner at the top of the page leads to a supplier of proprietary nickel strippers.

If you operate a legitimate industrial facility, this should be no problem. But if not, you may be able to get only very tiny packages of the required chemicals, or they may not be available to you at all. People are extremely leery about shipping cyanide to you, and manufacturers have a legitimate fear of liability in selling strong proprietary chemicals to the public, where your handling of them will not be under constant government scrutiny as it would be in a regulated plating shop. Think of their vulnerability if a neighborhood child develops cancer and her father feels you caused it by polluting his well, and there is a drum of their chemical in your residential backyard.

Sorry I can't offer real encouragement on the DIY front, but a plating shop can easily strip the nickel with those proprietary chemicals, and you are certainly welcome to try to buy them. Other than that, sandblasting is a possibility. Good luck.

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Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

February 20, 2008

I've read that sulfuric will strip nickel. I'm pretty sure that aqua regia (nitric mixed with sulfuric) will strip everything. I used it once to strip chrome off a part that I THOUGHT was a steel substrate. I watched with fascination as the chrome came bubbling off, then the copper sublayer (uh oh), then in horror as the aqua regia broke through to the ALUMINUM substrate. Oops! No more part. *blush*

Dirk Sears
- Corning, New York


September 18, 2008

Yes, aqua regia will strip just about everything. It's the only acid that will attack platinum. So if you really want results, and yearn to throw caution to the wind; it's the way to go.

Scott Koeble
- Brookings, Oregon


September 23, 2009

Hello Anybody!

Can someone tell me if there is an easy way to strip chrome from brass tubing?

I have chrome plated plumbing drain tubing that I need in brass, and can't find what I am looking for. All anyone sells is chrome plated brass or PVC. Can I strip the chrome off with some type of chemical bath?

Thanks much!

Don Wojtaszek
Home shop machinist - Berwyn, Illinois


September 23, 2009

Hi, Don. What we've been trying to say is, no, there isn't a really easy way :-)

A plating shop could strip it, but it would cost much more than most people would be comfortable with. But I think that the tubing you are looking for is available in brass. Have you tried a plumbing supply company as opposed to a hardware store? Good luck.

Regards,

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Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

October 23, 2009

I have a vintage bike with chrome fenders that are pitted. I want to strip the chrome from the fenders and paint them to match the gas tank. how can I do this?

Wayne Reese
novice - Lake City, South Carolina


December 1, 2009

Hi, Wayne. Have the fenders sand blasted to remove the chrome and roughen the nickel, then apply a bare metal primer before your finish coat. Good luck.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

December 1, 2009

Hi to all the finishing experts.
I am wanting to strip a golf club of it's chrome/nickel finish. The chrome could be gone and only the nickel left, I don't know, but I need to remove the finish in order to get a torched look to adhere to the Forged mild carbon steel.
My question is what would be an easy DIY way of doing this? Plus, would this grade of metal stand up to the "corrosiveness" of the compound used.
Oh, and I have no chemistry background so take it easy on the technical jargon.
Thanks in advance!

Jared van de Merwe
Putter Milling Machinist - Cape Town, South Africa


December 1, 2009

Hi, Jared. We've explained that there is no safe and easy chemical method for people without a chemistry background. Try sanding or sandblasting the nickel off. I don't know what a "torched" look is, but the bare carbon steel will rust quite quickly.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
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