Galvanic corrosion in aluminum & steel firearms

[vt_shooter]

With so many firearms made of both aluminum and steel, how come we don't see examples of galvanic corrosion, e.g., corrosion between the dissimilar metals? Or are people 50 years from now apt to see it in firearms made today? Coatings such epoxy or anodizing create barriers between the metals, thus preventing the corrosion, but where there are parts that pivot, such as steel pins that go through aluminum, I'd expect to see it. Or perhaps oil serves as a barrier? I obviously know little about it, and no doubt there are some people here that know a great deal about it. Here's an example of galvanic corrosion - I left a garden hose with aluminum fittings attached to a copper spigot for a season, and it just about welded itself on - it was nearly impossible to get off, but when I did, a coating of what looked like aluminum oxide remained on the spigot. (Now I Know to never buy a hose with aluminum fittings.)

I'm just curious why we don't hear about galvanic corrosion in firearms.

 

[Protocall_Design]

Anything that creates a barrier between the metals and/or moisture in the air stops corrosion. This can be oil or grease between parts, paint, or one of many coatings that fully enclose the part such as anodizing, any number of platings, chemical finishes like titanium nitride, or powder coating or ceramic coatings.

For galvanic corrosion to occur, the 2 metals have to be in contact and there has to be an electrolyte to complete the reaction. Dry air won't work, but in most environments there is enough humidity in the air to facilitate the reaction. In the garden hose case, there was plenty of moisture to make it work.

 

[Rule3]

Dissimilar Metal Corrosion with… | American Galvanizers Association


However, just because dissimilar metals are in contact does not mean galvanic corrosion will occur. The formation of a galvanic cell requires all the following components to be present1:

• Anode – metal of greater negative electrical potential, where electrons are generated by the reaction. Accelerated corrosion occurs here.
• Cathode – metal of less negative electrical potential, where electrons are received. The cathode is protected from corrosion.
• Return Current Pathway – electrical connection (e.g. direct contact) between the anode and cathode.
• Electrolyte – conductive medium that allows electrons to be transferred from anode to cathode. A common example is ordinary moisture such as water, rain, dew, snow, high humidity, or sea spray.

 

[BigBoy99]

One needs to be very careful with the guns made with zinc receivers. I had a newly made leather sling resting against the zinc receiver and the tanning chemicals ate a hole into the receiver!

I now put a piece of plastic sheet between the leather sling and the gun's metal.

 

[venomballistics]

Most aluminum applications are anodized.
Essentially, it's pre corroded where it forms it's own aluminum oxide shell. You will find this used in abrasive applications and wear points from time to time.
It's quite hard and durable, as well as impervious to corrosion since it's already in a stable oxide state.

 

[SF VET]

When I went off to Vietnam for a year, I left my Grumman 15 foot canoe at my parents house, leaning up against a chain fence. Came back a year later, and here were countless tiny holes all along the side that had rested against the dirt. I covered them with a layer of some sort of metal infused epoxy, and went on to use it for several years. Some sort of electrical conduction I suspect between the fence and the aluminum canoe and the ground. SF VET