Channel Jumper wrote:

Ralph Mowery;851568 Wrote:
"Bob Wilson" wrote in message
...--
Yes, there is a problem with aluminum to copper connections.

There are various "greases" to solve the problem.

-
That grease is widely used where aluminum power wiring comes in from a

pole and connects to a lug in a meter. And for that matter when I have

bought wiring panels (I mean the box where your power fuses or circuit

breakers live) they have come with a sticker saying the grease must be

used wherever wire other than copper connects to the panel.
Bob, WA9D-

That grease is fine for inside a house where it does not get wet.
Outside
for antennas it would probably wash off after a few rains. Then with
the
wet conductors you get what is called galvanic corrosion.

The more distance in the chart it is, the faster this action is.
https://en.wikipedia.org/wiki/Galvanic_corrosion

You can buy stainless steel tape at most welding shops.
The tape is used to protect threads and valuable machined parts from
weld slag. If you apply it to the copper, the aluminum will not
corrode.
The problem with stainless steel is that it is an alloy and has a
different dielectric constant than either the aluminum or the copper.

To be a bit simplistic, metals don't have a real dielectric constant.

The issue with dissimilar metal connections is the electropotential
difference between the metals in the presence of an electrolyte.

This means that if you can keep all electrolytes, which water is,
from the connection, nothing will happen.

As air contains water, keeping all water out is problematic.

The greases do two things; they contain conductive particles to minimize
the electropotential difference of the contact and provide a barrier to
keep water out.

Coating the copper end of a connection with solder also helps greatly
as it raises the anodic index from the -0.35 of copper to -0.65 which
is a LOT closer to the anodic index of most aluminum alloys.


--
Jim Pennino