I have read that older houses may have aluminum wiring, and to splice copper to it there is a less than desirable method of purple wire nuts using corrosion inhibitor paste.

My house was built in 1977, I had a home inspection done when I purchased the house a year ago that concluded that the house is copper wiring, and I read the sheathing for all of the wiring heading into the main breaker box and nothing seems to identify as an AL conductor, all standard copper Romex and the like.

All this to said, I was replacing nearly all of the fixtures, switches, outlets in the house and there were two places I backed off the wire nuts and found a sticky black paste on the twisted wires (dining room chandelier and outdoor porch lights). There wasn't any sheathing exposed to investigate further (and i didn't have the presence of mind to clean the bare wire enough to see if it looked aluminum). Am I being paranoid about the aluminum wiring thing? Would some electrician's opt to use some kind of conductive paste (black?) on a typical copper to copper termination? Or is there a chance that most of the visible working runs in the house we're replaced but maybe some aluminum was left some walls?

Thanks for any pointers, insight.

  • Can you post photos of the situation you found? – ThreePhaseEel Mar 28 '19 at 1:21
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    1977 doesn't fit with aluminum wiring anywhere I've lived. I think someone was using some sort of mystery goo in your wire nuts. Don't worry about this. – Aloysius Defenestrate Mar 28 '19 at 5:22
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    Could it be residue from a temporary use of electrical tape? – mike65535 Mar 28 '19 at 12:22
  • Absolutely possible that it could have been leftover electrical tape residue! – bmfinn Mar 28 '19 at 13:08

It's possible, especially on outdoor circuits, that someone decided to add Alumox paste. It helps prevent corrosion in general. Kind of a belt-and-suspenders approach.

Could someone have replaced only SOME of the old wiring? Sure, anything is possible. But if you are going to go to the expense, why stop 90% of the way there?

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