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dlj04(at)josephson.com
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 Posted: Fri May 18, 2012 9:49 am Post subject: Anti-corrosive paste |
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On 5/17/12 11:57 PM, AeroElectric-List Digest Server wrote:
| Quote: | Hi People,=0A=0AI would like to know what opinions you have on
anti-corrosi ve zinc paste to make our connections more reliable.
-Below is a link to an article on how ACZP helps make better
connections by
Bob has explained thoroughly about what's happening here. Let's go a
|
few steps further. The idea is to make the metal-to-metal contact area
of the conductors as large as possible by forming them into each other,
and to exclude any contaminants that might get between the metals. Any
nonconductive contaminant reduces the size of the contact area, which
increases the resistance. Most troublesome are oxides and salts of the
metals, which occur when air, water and other chemicals eventually
convert the metal to something else, producing a barrier between the two
parts. Zinc chromate paste excludes water to some extent but its main
function is to combine chemically with *aluminum* to produce a thin
chemical film that is conductive, and to prevent the formation of
aluminum oxides which are not. I don't know whether any such reaction
occurs with copper, I haven't seen "ACZP" used for this purpose.
The idea of using a grease like silicone (DC4) is based entirely on
excluding air and water. Silicone grease is used on microwave and RF
connections because it doesn't badly compromise the dielectric constant
of insulators it gets on. But for DC, any ordinary grease will do; it
also lubricates the parts as they are being crushed by the wrench or
crimper, so they can conform to each other's surfaces more readily. The
very best grease for this purpose has been used for nearly 100 years for
all kinds of high current applications by the telephone company, but it
seems to be a secret in the light aviation industry. I first learned of
it at a helicopter battery shop where they made their own version, with
a little more solvent added so it could be painted on. It's cheap and
readily available. It's a combination of petroleum grease, some waxes to
make it stiff and some amines to make it penetrate into joints and
spread throughout the voids in the contact over time. It is closely
related to "cosmoline" and is called No-Ox-Id "A Special" made since the
early 1910s by Sanchem in Chicago. A big tube of it sells on eBay for
about $10 but you can buy cases of 24 at less than $5 apiece. You can
see the various other versions of No-Ox-Id on their site. A-Special is
thinned out a little so it can be squeezed out of a tube (if the tube is
a little warm.) You only need a very thin film but you can coat all the
metal parts with this, clamp them together and you're done.
I have taken apart telephone company installations more than 50 years
old that had this stuff in all their joints and there has never been any
corrosion. Many fleet operators use it on battery posts and terminals to
keep the lead from corroding, you can even massage it into the joint
between the post and the battery case to slow down the battery acid
vapors from getting to the post that way. I started using it on aircraft
and automotive things about 30 years ago and it just works.
--
David Josephson
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wynaire(at)citlink.net
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| Posted: Fri May 18, 2012 10:05 am Post subject: Anti-corrosive paste |
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Thanks for an extremely helpful reply on the subject of pastes.
It's time to add another goody to the tool box!
M. Wynn/A&P, LNC2 bld'r.
*********
---
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wtmills
Joined: 05 Feb 2007
Posts: 32
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| Posted: Fri May 18, 2012 11:22 am Post subject: Anti-corrosive paste |
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Hi David -
This sounds similar in application to Par-Al-Ketone - used on aircraft flight and engine control cables. Do you know of this product, and is it similar No-Ox-Id?
See Wick's offering below:
http://www.wicksaircraft.com/catalog/product_cat.php/subid=10183/index.html
Bill
SF bay area
On Fri, May 18, 2012 at 10:45 AM, D L Josephson <dlj04(at)josephson.com (dlj04(at)josephson.com)> wrote:
[quote]--> AeroElectric-List message posted by: D L Josephson <dlj04(at)josephson.com (dlj04(at)josephson.com)>
On 5/17/12 11:57 PM, AeroElectric-List Digest Server wrote:
| Quote: | Hi People,=0A=0AI would like to know what opinions you have on anti-corrosi ve zinc paste to make our connections more reliable. -Below is a link to an article on how ACZP helps make better connections by
|
Bob has explained thoroughly about what's happening here. Let's go a few steps further. The idea is to make the metal-to-metal contact area of the conductors as large as possible by forming them into each other, and to exclude any contaminants that might get between the metals. Any nonconductive contaminant reduces the size of the contact area, which increases the resistance. Most troublesome are oxides and salts of the metals, which occur when air, water and other chemicals eventually convert the metal to something else, producing a barrier between the two parts. Zinc chromate paste excludes water to some extent but its main function is to combine chemically with *aluminum* to produce a thin chemical film that is conductive, and to prevent the formation of aluminum oxides which are not. I don't know whether any such reaction occurs with copper, I haven't seen "ACZP" used for this purpose.
The idea of using a grease like silicone (DC4) is based entirely on excluding air and water. Silicone grease is used on microwave and RF connections because it doesn't badly compromise the dielectric constant of insulators it gets on. But for DC, any ordinary grease will do; it also lubricates the parts as they are being crushed by the wrench or crimper, so they can conform to each other's surfaces more readily. The very best grease for this purpose has been used for nearly 100 years for all kinds of high current applications by the telephone company, but it seems to be a secret in the light aviation industry. I first learned of it at a helicopter battery shop where they made their own version, with a little more solvent added so it could be painted on. It's cheap and readily available. It's a combination of petroleum grease, some waxes to make it stiff and some amines to make it penetrate into joints and spread throughout the voids in the contact over time. It is closely related to "cosmoline" and is called No-Ox-Id "A Special" made since the early 1910s by Sanchem in Chicago. A big tube of it sells on eBay for about $10 but you can buy cases of 24 at less than $5 apiece. You can see the various other versions of No-Ox-Id on their site. A-Special is thinned out a little so it can be squeezed out of a tube (if the tube is a little warm.) You only need a very thin film but you can coat all the metal parts with this, clamp them together and you're done.
I have taken apart telephone company installations more than 50 years old that had this stuff in all their joints and there has never been any corrosion. Many fleet operators use it on battery posts and terminals to keep the lead from corroding, you can even massage it into the joint between the post and the battery case to slow down the battery acid vapors from getting to the post that way. I started using it on aircraft and automotive things about 30 years ago and it just works.
--
David Josephson
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longg(at)pjm.com
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| Posted: Fri May 18, 2012 12:19 pm Post subject: Anti-corrosive paste |
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Isn't that how they market dialectic grease available for $2 at Home Depot? That will likely work for the electrical parts you can access which means the electrical parts will outlast the rest of the airplane - for the body you simply take out all of the rivets between the non-compatible parts and puts some grease in there and rivet them back together. Good luck inside the wings. When your AP tells you your wing is rotting inside out from the same problem, have a check ready. Oh, and you do realize on older airplanes the wire covering will rot and short out only while you are flying at night before the connectors oxidize. When the skin comes off that big breaker wire in the panel on the old jobs, it's a real light show.
I'm sticking with carbon/fiberglass for the body. When I'm gone the wife can use it as a lawn ornament. The Buss panels you buy from B&C will probably last longer than you own your airplane. If not, they are < $20 to replace. If you smoke and would buy electrical parts each day instead of cigarettes, you could replace all the parts every weekend 
They also sell a kit that will charge - ions with + 1's to stave the rust advance - I've no idea if that swamp land idea works. Since many folks use some kind of battery tender anyway you can run a cord with a 25 watt bulb attached and hang it in your avionics bay. Cheapest insurance available. Of course you can also move to Arizona and just park in the field under an umbrella. Be sure to disconnect the light bulb before you fly away.
Have a great weekend everybody,
Glenn
--
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henador_titzoff(at)yahoo.
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| Posted: Fri May 18, 2012 3:45 pm Post subject: Anti-corrosive paste |
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Dave,
As Mike says below, thanks for an extremely helpful reply on the subject of pastes. I'm gonna look for a tube of No-Ox-Id A Special to see what it is like. I'm going to compare it to the Permatex stuff one can get at AutoZone to see which one I like better, as both are probably very good for this application.
Thanks, everyone.
Henador Titzoff
From: Mike Wynn <wynaire(at)citlink.net>
To: aeroelectric-list(at)matronics.com
Sent: Friday, May 18, 2012 2:02 PM
Subject: Re: Re: Anti-corrosive paste
--> AeroElectric-List message posted by: "Mike Wynn" <wynaire(at)citlink.net (wynaire(at)citlink.net)>
Thanks for an extremely helpful reply on the subject of pastes.
It's time to add another goody to the tool box!
M. Wynn/A&P, LNC2 bld'r.
*********
---
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dlj04(at)josephson.com
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| Posted: Sat May 19, 2012 12:36 am Post subject: Anti-corrosive paste |
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As Bob mentioned, any grease will do for a while to keep moisture out,
which (along with lubricating the joint to reduce friction so the parts
conform when being squeezed together) is what you want. I think
par-al-ketone would work too but don't have any experience with it.
Penetrox is a little different, it contains 15% zinc dust in a castor
oil base, not zinc chromate as I had thought or zinc oxide as others had
assumed. It is intended not only to keep some moisture out but fill in
some of the gaps with a conductive medium. If you can keep it all in one
place, fine, but I don't think I want bits of
zinc-dust-containing-grease wandering around the airplane. I mentioned
No-Ox-Id because I know it works, and it stays where you put it. You
want a metal-to-metal contact, not through some intermediary metal
powder if you can avoid it.
--
David
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