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Copper oxide diodes are not common now but were a standard item along with selenium oxide for early power rectifiers (think old radios and those components with stacks of fins).

Can the oxide layer on an old, exposed copper mains conductor provide any significant amount of (pulsed) DC component to an individual who accidentally touches it and is sufficiently grounded that they draw an AC current sufficient to be dangerous?

AC and DC currents have different physiological effects on nerves and muscles so a question about the distinction may be relevant, but here I'm only asking if the skin / copper oxide / copper junction would provide enough rectification to have to be considered separately from a pure AC scenario.


Background on copper oxide rectifiers:

YouTube:

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    \$\begingroup\$ I wasn't the vote. If you feel there is a problem, stop telling me how simple and easy it is to understand and work on it. If you don't feel there is a problem and the vote is just some random mistake and your writing is perfectly fine, then just ignore me and the vote. It's none of my nevermind. \$\endgroup\$ – jonk Oct 12 at 3:46
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    \$\begingroup\$ I only date back to WW II units. I also never saw the copper oxide devices. I did read the article, "The Copper Oxide Rectifier" by Chauncey Starr, though. Thanks for that link. It was enjoyable. \$\endgroup\$ – jonk Oct 12 at 4:26
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    \$\begingroup\$ Downvotes happen. People most often do not say why. My +1 negates it. \$\endgroup\$ – Russell McMahon Oct 12 at 12:05
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    \$\begingroup\$ @uhoh "diamond" is far closer to purgatory than one may have imagined :-) :-(> The aim was to help people - but a lot or the resource is taken up by attempting to herd fractious adult cats :-). [And I still only have a +1 to give per answer or question :-) ] \$\endgroup\$ – Russell McMahon Oct 12 at 12:25
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    \$\begingroup\$ Without a capacitor to filter the ripple, will the DC component be significant compared to the AC in the ripple ? \$\endgroup\$ – AJN Oct 12 at 13:20
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Copper oxide does introduce measurable nonlinearities - so your concern is warranted.

However, we can quickly, from systems where there's a lot of AC voltage intentionally brought onto copper parts (namely, broadcast and cellular transmitter stations), gather from the severity of the PIM (passive intermodulation) that the energy in these rectified parts isn't severe enough to be harmful to someone touching a piece of conductor connected to an "accidental copper diode" where not 1 kW of RF is pumped through...

Another aspect: these diode junctions have breakdown voltages in the region of 1 V. By itself, a diode of that type can't sustain a potential difference greater than 1 V; so no risk.
There would have to be a lot of factors coming together (like... an old-school metal-oxide layered disk stack diode) to yield dangerous voltages.

You can safely ignore this, and worry more about other occupational hazards.

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  • \$\begingroup\$ Thank you for your answer. In order to understand your analogy, I'd like to ask if the "1 kW of RF is pumped through..." a layer of copper oxide? I just want to double check that you are referring to RF being (weakly) rectified by passing through a path which contains a point where there is no copper-to-copper contact in parallel, or if there is some but there is also a parallel path that passes through oxide. In my question, the person (unfortunately) completes a circuit and draws current through the oxide layer. \$\endgroup\$ – uhoh Oct 26 at 23:50
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    \$\begingroup\$ yep, if you connect a copper waveguide to another copper waveguide, and on the interface of these two, there's an oxide layer, you'll have a lot of current pass through that oxide layer (lest you do very clever things with your waveguide, but that leads too far into the land of fancy flanges and fearfully frightening fractal costs) \$\endgroup\$ – Marcus Müller Oct 26 at 23:55

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