Tinned copper to aluminum connections? Cannot find info anywhere

[fbartlo (Frank Bartlo)]

I’ve searched all over the net for info regarding direct connections of aluminum and **tinned **copper wiring, but could not find anything.

I’ve been writing these up as I would any direct copper to aluminum connections, as I often see such wires combined without appropriate means for connecting copper to aluminum on sub-panel feeds (with sub-panels that are typically not properly grounded), but am wondering if such connections interact as badly as connections of bare copper to aluminum, as I’ve typically observed such connections, even obviously very old ones, to be free of noticeable corrosion.

It stands to reason the “tinning” would alter the electrical properties of the wiring, but I’ve been unable to find any info regarding this.

Any info would be appreciated.

[mlarson (Michael Larson, WI Lic. # 1672-106)]

Double tapped refers to two conductors on the same termination point of a circuit breaker. Some are rated for that and some are not.

Perhaps you mean something else.

[fbartlo (Frank Bartlo)]

I’m referring to interaction between tinned copper and aluminum, *not *properties of terminals or circuit breakers.

[mlarson (Michael Larson, WI Lic. # 1672-106)]

@fbartlo

I’m referring to interaction between tinned copper and aluminum, *not *properties of terminals or circuit breakers.

COPALUM Method of Repair

As an alternate to rewiring with copper, CPSC recommends attaching a short section of copper wire to the ends of the
aluminum wire at connection points (a technique commonly referred to as “pigtailing”), using a special connector named
COPALUM to join the wires.

CPSC staff considers pigtailing with a COPALUM connector to be a safe and permanent repair of the existing aluminum wiring. The repair
should include every connection or splice involving aluminum wire in the home, including outlets, dimmers, switches, fixtures,
appliances, and junction boxes. The repaired system, with short copper wire extensions at every termination throughout the
home, permits the use of standard wiring devices, including receptacles and switches

http://www.cpsc.gov/cpscpub/pubs/516.pdf

[fbartlo (Frank Bartlo)]

I know about that. But cannot find the information about the effect of “tinning” on such connections, which for all I know may or may not be significant. I’m really curious.

[mlarson (Michael Larson, WI Lic. # 1672-106)]

Tin and copper have almost the same galvanic reactivity.

http://www.corrosionist.com/Corros1.gif

[fbartlo (Frank Bartlo)]

Thanks. Graph provides excellent information. Of course, one needs to know what the metal used for “tinning” actually is.

[rcooke (Roy D. Cooke, Sr)]

@fbartlo

Thanks. Graph provides excellent information. Of course, one needs to know what the metal used for “tinning” actually is.

It I am sure is tin and they Tinned all Knob and tube wires as all joints where soldered to make good contact .
To solder copper wires required cleaning before soldering .
Tinned wires took the solder and a ggod joint was easy to do .
Been there done that many years ago.
Solder is made up with a large amount of tin in it .

[gcoy (Gerald L. Coy)]

I believe that part of the issue is the thermal expansion and contract differential between copper and aluminum wires. Whether or not the copper is tinned or not is pretty much irrelevant. That is probably why there is little specific discussion regarding tinning and this issue. As was pointed out any galvanic action with aluminum would be similar between copper and tin as well.