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Corkscrew
December 30, 2008, 13:44
I posted this over on AR-15.com but thought that I would get input from you guys as well. I just recently built two ARs and used Copper anti-seize grease on the threads on the upper. I got to thinking about the possibility of galvanic corrosion of the two different metals, aluminum and copper and was wondering if anyone else has used copper anti-seize on aluminum parts on an AR and had problems. There is also the issue of graphite in the compound that I used. It is called Spec308 from Topglock and I don't know if it has Graphite in it or not. Graphite is corrosive on bare aluminum. I know that AR manuals call for moly but I just happened to have some copper anti-seize, so that is what I used. Has anyone ever used Copper anti-seize on an AR barrel and had problems?

Thanks

C

L Haney
December 30, 2008, 18:44
If you want to ditch the metal bearing stuff completely, a tube of "Swak" from Swagelok will cure your worries. It's an anti-galling lube for high pressure stainless fittings. Also functions as anti-seize in any normal assembly thread loading pressures. This would include barrel/receiver threads.

Lowell

fastfreddy
December 30, 2008, 19:46
You could use the aluminum anti-seize that's widely available, eg Permatex.

tac-40
December 30, 2008, 20:07
Galvanic corrosion occurs when you have two dissimilar metals emersed in a medium that acts as an electrolyte. If you keep your weapons clean and lubed, it should not be a problem. The AR platform is a perfect example of this. Steel and aluminum together. I have not seen a well maintained AR exhibit any signs of corrosion.

elbo
December 31, 2008, 07:54
Al or steel seem to be at reasonably the same risk.



link (http://corrosion-doctors.org/Definitions/galvanic-series.htm)

A galvanic series has been drawn up for metals and alloys in seawater, which shows their relative nobility. The series is based on corrosion potential measurements in seawater. The relative position of the materials can change in other environments. The further apart the materials are in this series, the higher the risk of galvanic corrosion. (reference)

Most cathodic, noble, or resistant to corrosion

.................................................. .......
Platinum

Gold

Graphite

Titanium

Silver

Chlorimet 3

Hastelloy C

18-8 Mo stainless steel (passive)

18-8 stainless steel (passive)

Chromium steel >11 % Cr (passive)

Inconel (passive)

Nickel (passive)

Silver solder

Monel

Bronzes

Copper

Brasses

Chlorimet 2

Hastelloy B

Inconel (active)

Nickel (active)

Tin

Lead

Lead-tin solders

18-8 Mo stainless steel (active)

18-8 stainless steel (active)

Ni-resist

Chromium steel >11 % Cr (active)

Cast iron

Steel or iron

2024 aluminum

Cadmium

Commercially pure aluminium

Zinc

Magnesium and its alloys

..................................................
Most anodic or easy to corrode

Stranger
December 31, 2008, 21:49
Originally posted by tac-40
Galvanic corrosion occurs when you have two dissimilar metals emersed in a medium that acts as an electrolyte. If you keep your weapons clean and lubed, it should not be a problem. The AR platform is a perfect example of this. Steel and aluminum together. I have not seen a well maintained AR exhibit any signs of corrosion.

+1

You would have to displace the petroleum base of the anti-seize compound with a saline solution. That isn't exactly the easiest thing to do.

I guess if a person were to soak the joint in acetone for a few week to try and remove the oil, and then use high-pressure to inject a saline solution into the threads it might be a problem. But, who the fruck would do that? :confused:

Blood of Tyrants
January 01, 2009, 00:25
Originally posted by tac-40
Galvanic corrosion occurs when you have two dissimilar metals emersed in a medium that acts as an electrolyte. If you keep your weapons clean and lubed, it should not be a problem. The AR platform is a perfect example of this. Steel and aluminum together. I have not seen a well maintained AR exhibit any signs of corrosion.

Except that water will wick into even the fine threads and not come out.

NoNotAgain
January 01, 2009, 11:33
Provided that the anodized surface was intact and the parkerizing was whole, your galvanic cell would not be complete.

Hardcoat anodized aluminum does not conduct electricity.

The copper based anti-seize products are good at thermal conduction, not so great at electricial conduction.

If you are concerned about creating a galvanic cell, take an Ohm meter and attach one lead to the barrel with exposed metal and the other to a bare spot on the receiver and see if you have a complete circuit.

If the circuit is not complete life is good, if not when you have a chance get some moly lubricant and re-install the barrel after you clean every thing up.