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Electrical contacts with silver on them


#1

Hello,

I came across some electical contacts that are made out of steel.
Each one has a silver disk the size of a nickel attached to the
steel. What would be the best way to get the silver off of the steel
so that I could use it for casting.

Thanks
Dan


#2

Unsolder it. (That’s how I did mine)

Cheers
Hans Durstling
Moncton, Canada


#3

Assuming the disks are silver rather than a plated base metal then
just met them. Are you sure the rest of the contact assembly is
steel. This is unusual on electrical equipment where copper or
copper alloys are more common. If the rest is steel then the melting
point of silver is about 500C lower than that of steel so just melt
the silver in a crucible and hook out the steel.

I’m not sure how you can easily assess the purity of the silver.

All the best
Jenny


#4

It is likely soldered in place so you can un-solder it. But one thing
to think of is it is unlikely that the silver contact material is
pure silver. Silver palladium is a common contact alloy and there are
other alloys that it could be as well.

James Binnion
James Binnion Metal Arts


#5

I came across these things years ago at the local scrap yard, a
favorite prospecting locality. Typically they were on heavy copper,
not steel, were soldered on & easily unsoldered. I actually sent one
to a lab for analysis; to my surprise it turned out to be 99% pure.

Cheers
Hans Durstling
Moncton, Canada


#6
I came across these things years ago at the local scrap yard, a
favorite prospecting locality. Typically they were on heavy
copper, not steel, were soldered on & easily unsoldered. I actually
sent one to a lab for analysis; to my surprise it turned out to be
99% pure. 

Pure silver is the most electrically conductive metal and is used
for relay and other switch contacts. But it is soft and contact wear
from arc erosion and mechanical wiping is a problem, so there have
been a whole range of alloys developed to increase the contact life.
Cadmimum, copper, zinc oxide, tin oxide, zirconium oxide, nickel,
gold, palladium have all been used in silver alloys for electrical
contacts. So unless you do lab tests it is hard to know what exactly
the contact material is.

Jim

James Binnion
James Binnion Metal Arts