Wanders, thanks for the legwork and all of the links!
-----
Silver, copper, gold....
Off the top of my pumpkin head, and I am no engineer and am not looking up any data:
Silver is faultless. Its oxides are the only metal oxides (well its common oxides) that do not resist electricity.
A flashlight/torch with silver plated contacts would never give its owner a bit of trouble.
Copper: nearly as good a conductor as silver, but its oxides are absolutely ruinous to small voltage currents' passage.
Copper oxide was once the only, commonly used semi-conductor: they made low current AC rectifiers from stacks of copper disks.
Gold: the standard for fools and for reliable LOW CURRENT conductor terminations. It's a mediocre conductor.
It must be usually plated atop nickel, itself a poor conductor. Or put it on copper; the copper underneath eventually tarnishes,
yet the connector still passed current due to the immutable gold micro-thin plating.
The BEST of all is silver. Old milspec tube gear, used in the most demanding, damp circumstances, spec'd HEAVY silver plate on its contacts, connectors, tube socket pins. It's great stuff. It turns black in time, usually, but no matter: no resistance. DON'T polish silver plate.
BRASS, aside from cheap, brass or gold or copper plated steel, is the WORST of any electrical conductor: an alloy of copper with zinc:
Zinc is a terrible conductor and I mean, terrible. The copper is fine, but, hell, it tarnishes. Buss bars should never be of brass, but only of copper, or bronze; unless you could afford solid silver.
Aluminum: good conductor, cheap, terrible resistances form when the contacts oxidize. Special anti-corrosion pastes must be at the junctions.
Al. oxide is a perfect non-conductor.
Love silver, silver plate, and your grandmother's tea set.
Gold plate is for computers and delicate, cheap connectors.
Gold plated brass is shite.
Gold plated bronze (very rare) is good for the fact that bronze is a fine conductor, as its alloy metal is tin;
tin is a fine conductor, and its oxide is not all that much trouble.
Bronze for buss bars would be pretty good. So would be pure tin. But brass?
What is the conductivity of brass? Someone will look it up; it sucks.
Why don't "they" mass produce electrical switches and push-spring connectors of bronze,
and possibly silver plate?
Because the costs of the metals (tin and silver) are high.
The cost of gold plate is small because the coating is never thicker than a micron or three.
-----
Tinhorn Reid, the conduction kink master
