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There's a highly watched video on YouTube by "ElectroBoom" on the effects of passing AC (not DC) current through salt water. The water gets cloudy and at the end of the video we can see one of the copper wires has been eaten away by the process.

Is there really "a reaction of the copper with the salt in water" as the author of the video claims? Or is it a pure physical process where the copper "boils off" the wire?

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  • $\begingroup$ SAFETY - Using the name ElectroBoom gives me a bad vibe about this. By using alternating current you're getting both hydrogen and oxygen at each electrode. Together the two gases do react explosively. Don't do it... $\endgroup$ – MaxW Apr 10 at 13:25
  • $\begingroup$ @MaxW: I take your point about safety, but I haven't heard of AC current causing outright explosions in water. Although if that's the case, it would be an interesting part of the answer. $\endgroup$ – Fizz Apr 10 at 13:37
  • $\begingroup$ @MaxW: presumably if the current was high enough it could have the same effect as dropping something very hot in water, which can result in a vapor-related explosion, e.g. youtu.be/PDRWQUUUCF0?t=123 $\endgroup$ – Fizz Apr 10 at 13:48
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Is there really "a reaction of the copper with the salt in water" as the author of the video claims? Or is it a pure physical process where the copper "boils off" the wire?

Yes it reacts, no it doesn't boil. Essentially the wire corrodes at an accelerated rate where during the part of the cycle where the wire is the positive terminal the copper reacts as follows:

$$\ce{Cu^0 + 2OH- -> Cu^2+ + 2e- + 2OH- -> Cu(OH)2 + 2e- -> CuO + 2e- + H2O }$$ (expanded for clarity, not a reaction mechanism)

There is obviously oxygen generated too but I am only focusing on the copper part of the reaction. During the part of the cycle where the wire is the positive terminal the reverse of this reaction does not occur on the other half of the cycle and over time more and more copper will be consumed eventually consuming the entire wire.

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  • $\begingroup$ The dark brownish color in water seems indeed to match that of CuO much more than that of metallic copper. $\endgroup$ – Fizz Apr 10 at 22:27
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    $\begingroup$ @Fizz There may be some $\ce{Cu2O}$ produced as well which is reddish, the video isn't very clear. $\endgroup$ – A.K. Apr 10 at 22:30
  • $\begingroup$ Congrats on 1×10⁴ rep:) $\endgroup$ – andselisk Apr 11 at 4:11
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    $\begingroup$ @andselisk Thanks - It was quite the grind. $\endgroup$ – A.K. Apr 11 at 11:22

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