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Author: Subject: Chemical Removal of Copper from Graphite Gouging Rods
BobD1001
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[*] posted on 1-8-2019 at 17:23
Chemical Removal of Copper from Graphite Gouging Rods


Hi all,

Looking for some ideas to remove the copper cladding from graphite gouging rods. Obviously there is mechanical removal which I've found to be messy and very time consuming. I currently have a few rods soaking in a dilute HCl and H2O2 solution, seems to be working okay. Ferric chloride might work but will probably also contaminate the graphite making it unfavorable for some uses.

I just want to get some input on methods of removal that wont contaminate or degrade the graphite. This is for a video series, so I want to put multiple methods out there that I may not have thought of.

Cheers
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j_sum1
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[*] posted on 1-8-2019 at 22:58


Electrolysis?
You would want to rotate the rods though.




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Ubya
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[*] posted on 2-8-2019 at 00:44


being copper dilute nitric acid looks obvious.
then there's the microwave assisted carbon and hydrogen peroxide, acetic acid and a pinch of salt method (:D)





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rockyit98
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[*] posted on 2-8-2019 at 01:26


i did this before ,best way is Electrolysis in dil. sulfuric acid like 5%. use copper cathode so no waste is generated let it run till all copper is plated on the wire. it will not degrade the graphite if you used low current (1-2A)
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Heptylene
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[*] posted on 2-8-2019 at 04:47


1M H2SO4 + some H2O2 should work very well.
CuCl2/HCl should work well too, but might leave some CuCl residue.

Both these methods are used for etching copper on printed circuit boards.

If you have nitric acid on hand, it will work even better.
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AJKOER
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[*] posted on 2-8-2019 at 05:23


Commercial leaching of copper is accomplished with ammonia, ammonium carbonate, and air which is a mixed reaction involving some electrochemisty (and so, as an electrolyte, you might want to add a pinch of sea salt as Ubya suggests, a smart guy, but he apparently uses his microwave for everything, so I would trust this reference more https://www.researchgate.net/publication/260310630_Ammonia_l... and also this source, where the entire text is available for free at: https://www.academia.edu/292096/Kinetics_and_Mechanism_of_Co... ).

Unfortunately, the cited provided chemistry is even a little more complex with a mention of a minor secondary reaction, as the O2/Cu reaction complexed with NH3 is akin to a metal/air battery forming instrumental solvated electrons (as sourced from copper, so it is correct to claim that copper is catalytic to the oxidation of ammonia to nitrite from air). The latter e-(aq), I would surmise, with O2 may introduce the superoxide radical, and with H+, the hydrogen atom radical, which can interact with NH3 forming •NH2 radical, further interacting with O2 as follows:

•NH2 + O2 → NH2O2• (aminylperoxyl radical unstable) → NO + H2O

As a reference, see "On the aqueous reactions of the aminyl radical with molecular oxygen and the superoxide anion", Page 24, Table 2.1 at http://www.diva-portal.se/smash/get/diva2:730237/FULLTEXT01.... .

where the NO is a precursor to nitrite, and in particular NH4NO2. The latter has the annoying property of suddenly based on pH, of rapidly releasing volumes of N2 gas, which will cause leakage and even breakage of sealed reaction vessels (as I have experienced).

Some bottom line, don't tightly seal your reaction vessel (and I would recommend avoiding any skin contact with the solution due to possible toxic ammonium nitrite presence), because the cited minor secondary reaction (which creates NH4NO2) may have consequences.

[Edited on 2-8-2019 by AJKOER]
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