In article
,
Stanley Schaefer wrote:

On Dec 11, 11:06*pm, Searcher7 wrote:
I'm working on a project that is a mechanical switch of sorts, and it
entails running electrical signals through Phosphor-Bronze contacts.

Now since *all* alloys will oxidize to an extent, I was wondering if I
were to wipe the phosphor-Bronze contacts with the same
material(Phosphor-Bronze), would that be serve to keep the alloy's
surface clean? (The wiping action will be part of the mechanics of the
switch).

Thanks.

Darren Harris
Staten Island, New York.

That's the approach Ford took with their relays they use for low-
voltage and current switching in their cars. Took one apart and it had
a pretty elegant method for wiping the contacts. Relay lived in the
rear of the van and was exposed to salt spray vapor a lot of the
time. Not sure of the material, the contacts themselves consisted of
wire welded onto the springs, when in contact, they made an "X" with
each other rather than being parallel and wiped each other the length
of the contacts. It all worked until the non-conformal-coated circuit
board got eaten up.

This crossed-bars design was developed by Western Electric for the
relays in the telephone switching systems of the 1950s or so, for
exactly the same reason - making the relays self-cleaning in the
presence of (slightly) corrosive environments. These relays were
expected to last 40 years.

Joe Gwinn