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Preferrably one that is common or easy to make using common chemicals.

My application is to remove nickel plating from brass parts. Right now the best solution I have is to scrape and chip it off, but that sometimes takes up to 4 hours per part, and it often scratches the brass (sometimes badly).

An ideal solution would be to simply dunk the part in a solvent for 20 minutes and take it out clean!

Does such a chemical exist?

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    $\begingroup$ I don't think it would work, or at least be that simple. $\endgroup$
    – Mithoron
    Commented Apr 27, 2022 at 18:26
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    $\begingroup$ Why did you ask without doing research? Or at least telling what kind of brass is this, exactly. $\endgroup$
    – Mithoron
    Commented Apr 27, 2022 at 19:33
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    $\begingroup$ I am not an expert in this field, which is why I am asking on a website that is supposedly tailored to the field. Who are you to assume I have not researched this? And what degree of "research" is acceptable before I am allowed to ask a question on StackExchange? I don't know the alloy: all I know is it is "brass" and 99.9% "pure nickel". I do not know how to identify exactly what kind of brass it is. If you can't or won't answer, I'll go to a different website. This website seems awfully pedantic. $\endgroup$
    – user123594
    Commented Apr 27, 2022 at 19:52
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    $\begingroup$ Removing nickel plating from brass - "I have often stripped nickel from copper and brass. A thin layer will come off quickly in dilute hydrochloric acid. ... A common method of stripping thicker layers is a solution of 3 parts sulfuric acid to 2 parts water by volume. Apply a positive DC voltage to the part and use a lead cathode. About 6 volts should work." $\endgroup$ Commented Apr 27, 2022 at 21:03
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    $\begingroup$ @PeterMortensen But you don't mention the part that says that such methods also attack brass. That's the thing - whatever you'd use can dissolve both. $\endgroup$
    – Mithoron
    Commented Apr 27, 2022 at 21:33

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This is a bit more complicated than dip and rinse, but if you have a lot to strip, maybe you can make it work.

enter image description here

Nickel is mined, going from the oxide to the metal, by reacting the ore with water gas, a mixture of H2 and CO (made by adding H2O to hot and/or burning coal - at the relatively low temperature of 50ºC and atmospheric pressure). Now the OP already has metallic nickel, so this step is redundant. The next step, formation of Ni(CO)4 obviously takes place at temperatures below 230ºC, because it decomposes there to nickel metal. Ref 1

The proposed operation is similar to mining, except that the nickel is discarded and the depleted ore (the brass item) is retained. First step, get some coal; start it burning (with a propane torch). Shut off its air supply and feed steam or water mist onto the coal (which will cool it, but also generate H2O and CO) and pass the water gas over the nickel-coated item. The burning coal will cool, so you have to run some air over it to heat it up again; then more water mist or steam to get more water gas to pass over the nickel-coated item. Repeat until all the nickel is gone from the item and deposited somewhere else, far, far away, because the Ni(CO)4 is terribly toxic and you don't want to have any contact with it - at all.

As I ponder the set-up, this method should work, but it does seem more like a theoretical exercise or possibly an industrial project, rather than a do-it-yourself type of chemistry. It could be improved, or simplified, perhaps, by getting a cylinder of carbon monoxide and passing it slowly over the nickel-coated brass item at a temperature high enough to form Ni(CO)4, but not decompose it, then lead the gas (excess CO plus the Ni(CO)4) thru a very long pipe to a hot zone where the Ni(CO)4 would be decomposed to metallic nickel and the relatively less toxic carbon monoxide.

If you try this, do appreciate the toxicity of nickel tetra carbonyl (Ref 2) and CO (Ref 3).

Ref 1. http://wwwchem.uwimona.edu.jm/courses/nickel.html

Ref 2. https://en.wikipedia.org/wiki/Nickel_tetracarbonyl

Ref 3. https://en.wikipedia.org/wiki/Carbon_monoxide

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    $\begingroup$ I'm not an experimentalist, so somebody who knows more here please correct, but recommending Ni(CO)4 as a suitable substance for use in a home lab really makes me worry. $\endgroup$
    – Ian Bush
    Commented Apr 29, 2022 at 17:55
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    $\begingroup$ I'm just commenting here on the technical stuff and not on the content. You've chosen to make an image of a text that you later refer to by a link which proves that you just as easily (or more so) could have copied it from and pasted it into an appropriate environment. Why? Also, we have MathJax with mhchem enabled, they make setting reaction equations and formulae rather easy. $\endgroup$ Commented Apr 29, 2022 at 20:39
  • $\begingroup$ @Martin: Sorry, I'm not so well versed in all the options. $\endgroup$ Commented Apr 30, 2022 at 1:51
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    $\begingroup$ OP would be better off dumping all his brassware into an acid bath and performing a good ol' separation than work with metal carbonyls. Should they not want both their health and starting material in shambles, my two cents would be using acidification to dissolve minute amounts of nickel, then complexation (e. g. with oxalate) to recover more of the nickel. $\endgroup$ Commented Apr 30, 2022 at 13:41
  • $\begingroup$ @TheRelentlessNucleophile: I agree. I was thinking that adding a chelating agent in a known amount might complex off the Ni without affecting the Cu or Zn, but I think it would take a long time, and might need some acid - could get too complicated . $\endgroup$ Commented Apr 30, 2022 at 14:46

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