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Old June 18, 2019, 18:20   #51
hueyville
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Notice aluminum and stainless steel have a "high risk of galvonic corrosion".



Lots of folks are using titanium parts for their three pound poodle shooters. Notice the risk of titanium in contact with many metals including aluminum, steel and nickel. Will take a picture of my chart that recommends which compound has best ability to reduce corrosion between specific metals as not finding it online.



https://galvanizeit.org/design-and-f...als-in-contact

I keep a little bit of everything laying around. Carbon steel joined to stainless steel is much different than aluminum to carbon or stainless. Expose your area where parts are joined to moisture, especially salt water and all kinds of crap can go bad. I have at least a half dozen different goopy choices at my assembly area and refer to a chart that gives tips based on main two or three metals in a joined assembly point.



Quote:
Dissimilar metals*exposed to electrolytes exhibit different potentials or tendencies to go into solution or react with the environment. Thisbehavior is recorded in tabulations in which metals and alloys are listed in order of increasing resistance to*corrosion*in a particular environment. Coupling of dissimilar metals in an electrolyte will cause destruction of the more reactive metal, which acts as an*anode, andprovides protection*for the less reactive metal, which acts as a cathode.
Quote:
If the exposed area of the less noble metal is smaller than the other one, faster corrosion also results. Some commonly found combinations of metals that result in galvanic corrosion are copper and stainless steel, brass or*bronze*and steel, stainless steel and*carbon steel.
https://www.sciencedirect.com/topics...ssimilar-metal

Quote:
"The corrosion rate is related to the distance between the metals in the ranking; the further apart the metals, the worse the corrosion rate,” he wrote. “For example, aluminum is listed toward the active end, while stainless steel is listed toward the inactive end. If aluminum and stainless steel were immersed in a corrosive environment (road salt solution) the corrosive rate of the aluminum would be highly accelerated while the rate of the stainless steel would be reduced.

“Note that aluminum is close in activity with steel. However, they are still dissimilar metals and are subject to considerable galvanic corrosion when in contact in a corrosive atmosphere. Awareness of this ranking and the effect it has on corrosion rates is critical to the initial construction and repair of trailers and bodies. When dissimilar metals come in contact, which is unavoidable, there are several design guidelines that can be employed to minimize galvanic corrosion.”
https://www.trailer-bodybuilders.com...similar-metals

I have taken apart all manner of machinery, equipment, tools and even firearms to find issues with corrosion caused by dissimilar metals. Some not so bad and some horrible that are near failure point or already failed. Learning what simple materials can be used to reduce this is worth the time. The AR 15's you screw together today may be the same rifles your grand kids may have to maintain or repair and when they pull the threads off a receiver that new laws have banned manufacture of new replacement parts and they may be screwed because we didn't take a moment and three cents worth of correct compound to help the joined parts not corrode as badly.

I would not be suprised to find an AR upper that lived in Florida for 50 years that an aluminum upper with slightly different aluminum alloy than normal have a stainless barrel extension locked in place with carbon steel barrel nut have issues. Grandson or great grandson gets that spare barrel you hoarded away out, goes to remove barrel nut and shanks something off due to it not having anything done to slow galvonic corrosion, explore to salt environment it's entire life and builder used the snug it till its tight then lean on the wrench just one or two more times to get gas tube notch to line up.

Some of the problem uppers I have dissasembled that took 90 to 120 ft/lbs of torque to lossen barrel nut (had one shank entire end of upper off while kitchen table builder watched) and no compound for an anti-sieze or to slow corrosion and the rifles you buried for the generation of your heirs down the road that feel a need to repeat the little episode from 1776 may find their hoard of tools left by our generation has a high failure rate because we skipped the anti-seize and usee of a torque wrench. Yes, I am paranoid but helped restore boats that were less than a decade old. Torn apart greasy motorcycle, automotive, tractor and other engines to have steel bolts pull the threads out of aluminum blocks and other parts shaking off that should not have. Why will our rifles not have same issue when time to be rebuilt comes if we don't take precautions during the build?
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