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"Corrosion of indoor/outdoor Christmas lights"

December 11, 2015

Q. I have learned by hard experience (and the work of uninformed plumbers) that galvanized iron nipples cannot be used to connect copper water lines and brass plumbing fixtures. I've been told that the resulting galvanic cell causes corrosion of the iron pipe.

I've seen rusting of the contacts in the sockets of 'indoor/outdoor' Christmas tree light sets. I've checked. The contact strips and the wire contacts coming from the LED bulbs are both paramagnetic. Is this the same phenomenon? Should the contacts be all copper to prevent premature failure of the light strings?

John Baum
- Palo Alto, California, USA

affil. link
"No-Ox-Id" Compound

December 2015

A. Hi John. Ideal would be for both components to be made of beryllium copper and then electroless nickel plated -- but Christmas lights are considered cheap, semi-disposable, items. Yours apparently are made of copper plated or tin plated spring steel, and the problem is probably not galvanic incompatibility, but simply that the plating is not thick enough and non-porous enough to be long lasting without corrosion.

You could probably prolong their life by using an anti-oxidizing compound, and by storing them with desiccant or even a VOC corrosion preventative, but the insulation on the wires will only last a limited number of seasons as well. Merry Christmas.


pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
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