AR Building with parts of dis-similar metals/coatings

[pert near]

Something I hadn't given much thought to until I read about how some handgun designs having problems with parts of different types of metal. Apparently different metals against each other cause electrolysis/corrosion & or can gall when they must slide against each other.

When building an AR there are myriad of parts, metals, & coatings to choose from. For instance, is it a good idea to match a SS gas block to a melonite coated barrel? Or how about putting a SS extension on a chome-moly barrel? Is that a big no-no?

TIA for any advice or comments...

 

[someguy2800]

Unless your taking your rifle salt water diving I wouldn't worry about it

 

[CraigC]

If you're threading a steel screw into aluminum threads, it's a good idea to use anti-seize compound or thread locker but other than that, it's a non-issue. Don't over-complicate it.

 

[coloradokevin]

The short answer is you'll be fine.

AR-15's have a lot of aluminum and steel parts, and in theory you can get galvanic corrosion by having those two types of metals in contact in the presence of an electrolyte. But, ask yourself how many AR-15s have been built, and how many are falling apart because of the aluminum and steel working against each other.

I will say that I used the specified Aeroshell grease when attaching the barrel. Not sure if it helped, but made me feel better.

 

[lysanderxiii]

All aluminum parts in an AR are anodized. This prevents galvanic corrosion, as the aluminum oxide layer is a very good insulator, about as good as glass, so there really isn't ant direct aluminum-to-steel contact.

 

[grampajack]

The problem arises when people use greases containing graphite and nickel, then get the rifle somewhere on the coast where there's sea spray in the air. Use moly grease or 100% copper anti-seize and you'll be fine.

All aluminum parts in an AR are anodized. This prevents galvanic corrosion, as the aluminum oxide layer is a very good insulator, about as good as glass, so there really isn't ant direct aluminum-to-steel contact.

One of several great reasons not to mess with 80% lowers unless you plan on having it anodized afterwards, which, not including labor, should only bring the final cost to about 300 bucks or so...

Assuming you even get it right the first time.

 

[lysanderxiii]

The problem arises when people use greases containing graphite and nickel, then get the rifle somewhere on the coast where there's sea spray in the air. Use moly grease or 100% copper anti-seize and you'll be fine.



One of several great reasons not to mess with 80% lowers unless you plan on having it anodized afterwards, which, not including labor, should only bring the final cost to about 300 bucks or so...

Assuming you even get it right the first time.

Graphite in grease does not cause problems....

(Unless you're a Seal, or some such...)

 

[grampajack]

Graphite in grease does not cause problems....

(Unless you're a Seal, or some such...)

Or you sweat...

Considering the inexpensiveness of the correct mil-spec products I don't think it's worth the risk of using whatever you happen to find at the auto parts store. I would go as far as to say it would be okay to use any straight up moly grease, but I certainly wouldn't risk using graphite or nickel. If nothing else, it will void whatever warranty you might have had. I actually had a fairly long conversation with Vltor one day trying to figure out what their warranty required (the little slip that came with the receiver was very vague), and after being passed around quite a bit finally was told to only use 100% copper anti-seize, milspec blah blah blah. They use it exclusively on all their stuff. I asked them if it had ever been tested in salt water environments, and they claimed they had both rifles and grenade launchers being used by the military for maritime operations and no reports of galvanic corrosion.

 

[MistWolf]

VLTOR had it wrong. Copper will promote galvanic corrosion between steel and aluminum. Boeing Aircraft Company Tech Manuals specifically forbid the use of copper based Never Seize between steel and aluminum parts. They require the use of nickel based Never Seize.

Graphite causes embrittlement of metals, particularly on titanium and aluminum and metals exposed to high temps. A graphite pencil is absolutely forbidden for drawing on aircraft parts for this very reason

 

[redneck2]

I sell a industrial products. A really common area that sees electrolysis is the little bolts that hold street signs onto the clamps on the steel poles. After a few years they are about impossible to remove. These aren't in salt spray. Typically aluminum housing with steel bolts.

So, it's possible to have a reaction. Weather/humidity/chemicals may all greatly accelerate the reaction

 

[grampajack]

VLTOR had it wrong. Copper will promote galvanic corrosion between steel and aluminum. Boeing Aircraft Company Tech Manuals specifically forbid the use of copper based Never Seize between steel and aluminum parts. They require the use of nickel based Never Seize.

Graphite causes embrittlement of metals, particularly on titanium and aluminum and metals exposed to high temps. A graphite pencil is absolutely forbidden for drawing on aircraft parts for this very reason

I would have thought so too, but every Vltor/Abrams product that leaves that factory has threads coated in LPS milspec anti-seize, and they claim they've never had one come back with galvanic corrosion, even if submerged repeatedly in saltwater. They could be lying, but I don't know why they would still be using it if it were costing them money. I thought the lady who answered the phone was off her rocker, so I got it straight from the horse's mouth (they probably hate me over there, but it's their fault for leaving vague and confusing instructions with their products).

 

[MistWolf]

I don't think VLTOR is lying about never having any trouble with galvanic corrosion. I've had this same conversation with another knowledgeable AR armoror and he said he's never seen any problem from using copper based Never Seize. Anodizing does its job. However, based on years of personal experience in the field of aviation, I go with the science and tech data. I've seen and repaired a lot of corrosion and cracks