Airweight Frame is corroded

[ArchAngelCD]

I'm just curious, how did the finish get like that?

I think the suggestion Rule3 gave you in Post #4 is a good idea. Easy to do, not expensive and will stand up to cleaning.

 

[BC38]

FWIW, if you feel you must paint it with something, and want to do something cheap and spray-on, I would pick up a can of POR-15 Topcoat. It is one of the toughest paints I've ever seen and it sticks to metal like nothing else.

 

[Rule3]

Now don't tell me aluminum (alloy) will not corrode!There are dissimilar metals in a gun (inside, the barrel and the cylinder) They top coat the alloy to prevent "oxidization" Once it is Oxidized it will leave a coating on it but looks ugly

This picture is of course a joke and example of galvanic oxidation corrosion. Dissimilar metals in a salt bath! Which is why outboard (drives) have sacrificial zinc anodes on them. Of course be submerged didn't help.

This boat just "appeared" one day in the bay!

 

[snowman.45]

I once had a 340Sc that I bought new and traded away to one of my officers. He could never qualify with it, but seemed to have carried it anyway and absolutely destroyed the finish. He traded it back to me and I went to work on it. I lightly bead blasted it after a complete disassembly (excluding the titanium cylinder. I then applied KG Guncoat and allowed it to dry to the touch, then baked it at 300 degrees for the prescribed time. I applied a titanium-colored finish to match the cylinder. It came out great and was as durable as any of the other coatings that were available at the time, definitely tougher than the DuraCoat available then.

 

[BC38]

Now don't tell me aluminum (alloy) will not corrode! There are dissimilar metals in a gun (inside, the barrel and the cylinder) They top coat the alloy to prevent "oxidization" Once it is Oxidized it will leave a coating on it but looks ugly

This picture is of course a joke and example of galvanic oxidation corrosion. Dissimilar metals in a salt bath! Which is why outboard (drives) have sacrificial zinc anodes on them. Of course be submerged didn't help.

This boat just "appeared" one day in the bay!

Nice "joke" photo that shows exactly what I referred to - a corrosive agent (salt water) that continually attacks the natural anti-corrosion coating of aluminum oxide to expose fresh new aluminum underneath to be further corroded.

You are right, there are dissimilar metals in contact inside the gun - where the lockworks touch the frame. However, that by itself is not enough to cause galvanic oxidization corrosion. From the link supplied by Jimboecy

Corrosion is an electrochemical process in which four (4) conditions must be present or corrosion will not take place:
1) There must be a positive or anodic area, referred to as the "anode".
2) There must be a negative or cathodic area, referred to as the "cathode".
3) There must be a moisture-bearing electrolyte for ionic current flow between the anode and cathode. It is important to note that the anode and cathode must be immersed in the same electrolyte. The atmosphere is not an electrolyte. Two pieces of metal touching each other in a humid environment develop excellent conditions where current flow will occur.
4) There must be a return path for electronic current flow, which is referred to as a "metallic path" between the anode and cathode.

While the internals of the gun may meet conditions 1, 2, & 4, condition 3 will not be met - unless the gun is left soaking in salt water like the motor in your photo. In fact the opposite is true inside the gun. The dissimilar metal parts are (or at least should be) coated with a thin layer of OIL, which is NOT an electrolyte that will support the necessary flow of current, it is in fact a barrier film that isolates the two metals from one another and reduces current flow between them.

Back to the motorcycle engine example I gave earlier. Not only are the case and all the cooling fins around the cylinder made of aluminum alloy, they are in direct contact with other metals - namely steel for the bolts and fasteners. This contact between dissimilar metals (the same two metals as what are in the gun by the way) is further exposed to repeated temperature swings of up to 300 degrees and at the same time repeatedly exposed to water. Do dirt bike engines look like the boat motor in your picture? NOPE. I can show you examples that are 30, 40, 50 years old that show no significant corrosion - nothing beyond the dullness of a naturally occurring aluminum oxide layer. The parts aren't corroded together and can be disassembled as easily today as they could when they were a year old.

The darker dull gray color of a natural aluminum oxide layer may not be as pretty as the shininess of the polished and clear-coated aluminum, but it really doesn't look much different than the coating on a titanium cylinder.

 

[armorer951]

After cleaning and glass beading, POR Topcoat applied with an airbrush would do the trick, at least for awhile.

 

[BC38]

After cleaning and glass beading, POR Topcoat applied with an airbrush would do the trick, at least for awhile.

You can even do it without the airbrush - they sell it in aerosol cans.

 

[mscampbell2734]

#3 is often met by plain old pocket sweat. I've seen many a pocket carried guns with really bad rust or corrosion. Steel frames would have overall rust and alloy frames would have visible corrosion where steel pins/inserts were.

 

[BC38]

#3 is often met by plain old pocket sweat. I've seen many a pocket carried guns with really bad rust or corrosion. Steel frames would have overall rust and alloy frames would have visible corrosion where steel pins/inserts were.

Yeah, good point I guess, if you sweat that hard and neglect them badly enough. That didn't affect the insides though, did it? Just the interface at the outer surface?

 

[hkcavalier]

There are pretty guns, and there are carry guns.

Over time, there are no pretty carry guns.

 

[Hondo44]

Please don't waste time on Aluma Hyde, it's a complete waste of money.

Now that you have the hard work done, it's prepared for an epxy finish. Dura Coat now comes in a spray can for about $39. Once you activate the two part epoxy finish by pushing the button in the bottom of the can, you have an hour or two to spray it.

You have choices of color and once it's dry and hardened she won't live long enough to ever need another refinish.

 

[stansdds]

The best finish for aluminum is anodizing, which gives the aluminum a hardened surface and can also provide color. Another option might be one of the nickel plating treatments like NP3. Much less expensive options would be Cerakote, Gunkote, or DuraCoat. Gunkote and DuraCoat are good DIY options.

 

[Rule3]

Please don't waste time on Aluma Hyde, it's a complete waste of money.

Now that you have the hard work done, it's prepared for an epxy finish. Dura Coat now comes in a spray can for about $39. Once you activate the two part epoxy finish by pushing the button in the bottom of the can, you have an hour or two to spray it.

You have choices of color and once it's dry and hardened she won't live long enough to ever need another refinish.

Dura Coat is certainly an excellent option. It is however is a one time deal. Once activated you can never do a touch up later.


Where do you find it for "about $39.00"??

 

[mscampbell2734]

Yeah, good point I guess, if you sweat that hard and neglect them badly enough. That didn't affect the insides though, did it? Just the interface at the outer surface?

For the most part yes, just the surface. I've never personnel seen/handled a rust frozen pocket carried revolver. Some of the Department armors tell me they have seen it.

 

[riverrat38]

I have sanded and polished Aluminum bicycle parts like stems, and they have remained like new after years. I occasionally rubbed some anti corrosive oil, like Boeshield, on the parts. Don't know if that's necessary, but I do it. May be different in tropical climates. I know, from reading, that Aluminum sail boat masts need attention in such environments.

Best,
Rick

 

[BC38]

...I know, from reading, that Aluminum sail boat masts need attention in such environments.

I think it is safe to say that would be less due to the climate, and more due to their exposure to saltwater...