[Milsurplus] contact cleaners

[aGEnuine Ham]

Brooke:

One of the misunderstood aspects of the contact problem is that it is
rarely as simple as oxidation.  This is apparent when you consider the
silver plating on many switches and connectors.  Silver oxide is a fair
conductor, which is why it is chosen.  Other compounds of silver do not
fare so well.  Gold is not supposed to corrode at all.  HA!  One of the
principal offenders is sulfur, which migrates out of most old rubber
products.  Unfortunate choices of materials in many places produce what I
prefer to call corrosion products on just about any metal you can name. 
Some ferociously attack stainless steel, for example*.  And, this is
where the problems arise in both cleaning and in preserving the contact
surface.  Some corrosion products have to be mechanically removed, as
they will only yield to cleaners which damage everything else.  Then,
products like silicon grease are only partially resistive to vapor
penetration.  Most do a good job against water, but some of the other
vapors can penetrate them.  The only cure is to remove the source, which
sometimes is the rubber insulated chassis wiring itself.  So, this
corrosion cleaning and preservation can get very involved in some cases.

73,
George
W5VPQ

* The pins on Loktal tubes are a version of supposedly stainless Invar or
Kovar, I forget which, to match the thermal expansion of the glass in the
header.  Same for miniature tubes, I believe.  In an attempt to corner
the market, one of the radio hoarders I knew long ago stashed a big pile
of early 2-way radios in his active chicken coop, rather than sell them
at reasonable prices.  The vapor from chicken manure ate the pins
completely off all the Loktal tubes, and reduced the value of his tightly
held equipment to zilch, much to the amusement of the hams he was trying
to rip off.  Happened in just a few months, too, as I recall.  Didn't
bother the aluminum locating key, just the pins.

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