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:
- The Copper Oxide Rectifier
- Applications and Characteristics of Copper-Oxide Rectifiers July 1933 Radio-Craft
- The Copper Oxide Rectifier (1936, paywalled)