Gregg Klawson said:

>At 2:47 PM  -0400 5/20/96, [log in to unmask] (Jerry Cupples) wrote:
>
>>Doug McKean asked:
>>
>>>          Green Cu oxide shows up on socket pins after about three
>
>I believe copper oxide is black not green.  Sounds like it could be a
>copper chloride.

Yes, cupric oxide is black to brownish black. Coppers salts are blue-green,
but it could be many other things besdes cupric chloride.

>
>>>          months in the field.  Very little shows up before assembly,
>>>          or shipment.
>>
>>Regarding copper, the Merck Index says: "...in moist air, gradually becomes
>>coated with green basic copper carbonate" Most copper salts are blue or
>>blue-green. I think that the salts tend toward a bright blue. As a wild
>>guess, if the color is bluish, it could be an artifact of halide
>>contamination. Straight green, OTOH is normal after environmental exposure
>>to water vapor. A real chemist might disagree.
>
>Well I'm not a real or psuedo chemist but pure water won't hurt you.  It's
>little traces of nasty things like chlorides in the water which hurt.   A
>simple view of corrosion is you need three things for it to occur: a
>corrodent (chloride (Cl) for example), water (H2O) and something to corrode
>(the copper).  Take away one of the three and nothing happens.

Gregg, with H2O + CO2 from air and you have dilute carbonic acid in
minutes. Take the pH of some DI water, let it sit out in a beaker a few
minutes; remeasure. Even distilled deionized water or pure water vapor can
attack most metals if exposed to open air. Of course adding any salts makes
a better electrolyte.

Also, pure DI water has murderous effects on many metals. Try piping some
through some copper...

My point is that you don't have to add chlorides to see adverse effects on
copper with exposure to pure water and air. Add some energy from elevated
temperatures, copper becomes copper carbonate.

cheers,

Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com