Hi, i wonder how copper will oxidate with only air as insulation, for example with only cotton or a teflon tube?
Back in the days of wooden conduit for single wire house wiring, (pre 1950 in the UK), the wire was insulated with cloth but was always tinned.
Definitely, copper wire must be tinned during manufacture to prevent oxidation
from the oxygen in the air.
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House wire (US) is never tinned(*). It oxidizes when hot-drawn so they run it through a "reducing furnace" where excess carbon eats-off the oxide and makes it pretty. In the house, over the years, it oxidizes, sure. In dry work it does not grow green-scuzz. The usual house-wire connectors use large pressure to break-through the oxide and this is rarely a problem(**). For soldering, old wire must be scrubbed or scraped to break the oxide so flux and solder will bond.
(*) Except under old rubber insulation, where the sulfides would quickly darken and eventually eat the copper.
(**) Unlike aluminum wire, where the tough insulating oxide resists ordinary pressure connectors and leads to trouble; little trouble in large gauges on proper connectors professionally cleaned and treated against oxidation.
(*) Except under old rubber insulation, where the sulfides would quickly darken and eventually eat the copper.
(**) Unlike aluminum wire, where the tough insulating oxide resists ordinary pressure connectors and leads to trouble; little trouble in large gauges on proper connectors professionally cleaned and treated against oxidation.
Old copper in dry conditions just goes a dull brown colour on the surface. No harm done by this. So yes copper will oxidise, but no it doesn't matter.
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