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Conductive grease

 
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TELEDYNMCS(at)aol.com
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PostPosted: Tue Feb 07, 2006 6:28 am    Post subject: Conductive grease Reply with quote

In a message dated 2/4/2006 3:01:09 AM Eastern Standard Time,
europa-list-digest(at)matronics.com writes:

Hi Brian

Quote:
A smear of grease might be Ok after you have connected the earth terminals
but not before. You want the best possible electrical contact and this
requires a chemically clean joint- grease on the contact face is not good

This would be true for normal grease, but there are products available that
are conductive, usually refered to in the telecommunications world as
"conductive grease". You will find them at any electrical supply house. One in
particular we use on copper to copper connections is called "Penetrox". Penetrox
is basically copper powder that is mixed in grease. There are also similar
products sold under the name "Copper Coat" and "CopperOx". These preparations
enhance the conductivity of the connection between a lug and buss bar or
between the lug and the cable if applied before crimping them. They also prevent
oxidation of the connection later on. They are commonly used on electrical
connections that are exposed to weather, such as lightning protection systems and
outdoor lighting fixtures. There are also products available specificly
formulated for aluminum to copper or aluminum to aluminum connections.

Anyway, hope it helps!

Regards,

John Lawton
Dunlap, TN
A-245 (Engine installation complete, airfame complete, painted surfaces
being finish buffed today while I await FAA registration. Watch this space for a
big announcement coming in a few weeks!)


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TELEDYNMCS(at)aol.com
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PostPosted: Wed Feb 08, 2006 6:51 am    Post subject: Conductive grease Reply with quote

In a message dated 2/8/2006 3:01:07 AM Eastern Standard Time,
europa-list-digest(at)matronics.com writes:

Hi Fred,

Quote:
I don't see how conductive grease will solve or prevent any
problem.

Sure it does. Conductive grease enhances the conductivity of the connection
and prevents oxidation down the road. Penetrox is used either between the lug
and the buss bar or between the lug and the cable. A lug that is freshly
crimped or recently installed on a buss bar generally doesn't need any
conductivity enhancement, but 5-10 years down the road when corrosion sets up between
the cable and the lug or the lug and the buss bar it becomes very important.
You only use a very thin layer of the Penetrox between the cable and the lug
or the lug and the buss bar, so there is no need to worry about heating up
the grease and having it run out. I've seen lugs on lightning protection
systesm that took repeated direct lightning discharges on literally thousands cell
towers and I've never, ever seen Penetrox run out due to heating. Believe me,
the lugs get very hot when they take a direct hit by lightning, particularly
in Kentucky and Michigan where the ground resistance is high.

Small crimps get soldered to prevent oxidation. Large lugs are difficult to
solder, so
Quote:
Penetrox is used. This is industry standard.

I also put a piece of heat shrink over the crimped area of the lug. The shrink
Quote:
will help prevent oxidation and it makes the connection look better, too.
I have seen quite a few battery cables fail on automobiles due to oxidation
between the end lug and the cable, particularly on GM products. However, I
have never once seen a cable connection fail when Penetrox or Al-Ox was used in
more than 7,000 cell site installations I've done over the past 19 years.

In regard to not being able to Google up a specific application for Penetrox
on aircraft, this does not surprise me in the least. As you are aware, we
live in a very litigious society. Given the long and sorted history of aircraft
liability in our court system, manufacturers who do not specifically produce
products for aircraft use are usually very reluctant to say one way or the
other if their products are applicable to use on an aircraft, particularly if
that aircraft is experimental. I ran into this a while back when I made the
mistake of telling a paint manufacturer that I was wanting to use their paint
on an airplane. All I wanted to know was whether or not their paint provided
adequate UV protection for the underlying composite. As soon as I mentioned
aircraft, they stopped responding altogether. I appoached them again a few
weeks later with a different e-mail address and mentioned fiberglass "boat"
instead of fiberglass "aircraft" and they gave me all the info I could ever want
about their paint products. As a result my fiberglass airplane, er, uh,
"boat" is now white and shiny and has loads of UV protection.

Regards,

John Lawton
Dunlap, TN
A-245 (Engine installation complete, airframe complete, painted surfaces
being hard waxed and buffed today while I await the return of FAA registration
paperwork sent in NOVEMBER! Watch this space for a big announcement coming in
a few weeks!)



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n3eu(at)comcast.net
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PostPosted: Wed Feb 08, 2006 3:28 pm    Post subject: Conductive grease Reply with quote

it does. Conductive grease enhances the conductivity of the
Quote:
connection and prevents oxidation down the road.

Well, chicken soup can't hurt either, if you have a cold.
Seriously, I've not seen it used in cars, and the operating
environment under the hood is a brutal one where they use
salt on the roads. Every time like a sensor fails, I'd
prefer it to be the connector, but it hasn't yet been so.

On my 1972 plane, inside the tail cone (partially exposed to
elements) there's a pair of spade connectors for the nav
light. Difficult to replace, that arrangement is rusted,
corroded, and soaked with dirty oil. From the control
hardware above it dripping oil I put there every inspection.
The nav light just simply refuses to ever not work. If
anyone wants the brand and part# of this connector, I can
maybe research it! Wink

Reg,
Fred F.


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