How to avoid corrosion between al and steel

[mikeyanxu]

Had run across this type of questions a few times. There are a few standard methods at work (aircraft manufacture)and no one seems to question about it. Just follow the spec and do what is always be done, right?
[ul]
[li]For example, steel fastener in aluminum airframe. Cad plate fasteners, anodize aluminum, and wet dip fastener in primer upon installation.[/li]
[li]Steel rod end into flight control rods. Cad plated rod ends with aluminum flight control rods. Wet dip rod ends threads in primer upon installation.[/li]
[/ul]

Are the above methods adequate? Maybe, people still discover corrosion when tearing down the old airframe at the above locations.

Now, down to my own home project and I can decide what to do without an FAA approval, nice. Since I am an engineer, I would like to do it right. See the picture, it is a firearm project.
The upper receiver is anodized aluminum 6061, 7071 or maybe 7075, unknown temper.
The barrel is 8620 steel, heat treated. Parkerized or blued.
The barrel nut is steel, heat treated. Parkerized or buled.
The shim is stainless. Not known if it is passivated.
The end of the threaed section of upper receiver had been lapped/ground to produce a true perpenticular surface reference the thread. So, the anodize on the face is gone. It is bare aluminum with touch up "cold blue". I think it is a kind or touch up alodine.
So, the way it will be assembled, what anti-seize (or compound) should I use to avoid galvanic corrosion between the upper receiver and the barrel nut or between the receiver and the barrel?
Thanks.

 

[CoryPad]

What is your electrolyte/corrodent? Are you sure you will have corrosion? Can't you anodize after lapping/grinding? I would expect thermal expansion/contraction and fretting fatigue issues before galvanic corrosion.

 

[mikeyanxu]

Thanks for the reply. I am not sure if I will have corrosion, but I have concerns and that is why I am here to ask.
No, I can not anodize again. The upper receiver has been anodized. The only spot missing anodize is the lapped/ground area. I will touch up with "cold blue" some kind of gunsmith solution and I think it is just touch up alodine with black dye.

So, will this "cold blue" be adequate? It touches the barrel (parkerized steel) when they are assembled. If I use anti seize which contains graphite, will this promote corrosion?

I would not worry about any other issue since it is a proven AR15 design and I am not changing anything else.

 

[swall]

I would touch up the ground/lapped area of anodic film with Alodine. Then I would quit worrying about it.

 

[EdStainless]

I would also worry more about galling or fretting.
For anti-seize I would use a good synthetic grease like Krytox.

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Plymouth Tube

 

[CoryPad]

Graphite will promote corrosion