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How long will a bright dipped copper part last?

(-----) February 27, 2008

Q. I am a Quality Manager who supply a customer with a Copper part stamping that went through a Bright Dip Mechanical process. The parts were processed a year ago and now this customer is complaining about oxidation in the part (like black spots). Is there a shelf life for this process? Thanks for your help.

Don Nalupta
Buyer - Orange, New Jersey

February 27, 2008

A. The shelf life would depend upon the exposure conditions, but it would not be long. As you would know from looking at copper roofs, it tarnishes or patinas. It would not be unusual to treat the copper with benzotriazole after bright dipping to extend the bright life somewhat. I think a year is a long time unless preservation measures were taken.

We also have a thread here about "Shelf life of PCBs / PWBs" which some readers might find relevant or interesting. Good luck.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

March 4, 2008

A. Immersion coppering using a mechanical process (either with glass beads or self-tumbled) is a common means of providing a copper finish on parts (particularly small parts under 1 pound or under 6 inches in length), often for part identification or for lubricity. The deposit achieved is self-limiting (as the steel, the reducing agent, is covered with copper) and is quite thin - about 9 millionths of an inch. The deposit provides NO corrosion protection (see, for example, Ford S-5 or Chrysler PS-4935). In fact, the steel will corrode to protect the copper, since the copper is more noble. Inhibitive systems used to protect immersion coppered parts (contact your supplier) generally protect against the corrosion of both steel and copper. Leaving the surface slightly alkaline will extend the shelf life. Even so, the corrosion protection is VERY limited. If additional protection is required, a lacquer topcoat would definitely help.

Tom Rochester
CTO - Jackson, Michigan, USA
Plating Systems & Technologies, Inc.
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