Anodizing of firearms. Refinishing AR15 receivers

A. Hi wyatt
I have seen it a few ways. Depending upon the component, hardcoat was prevalent. Some want mil spec work but then when something goes awry they buck the spec and want to do their own thing. The spec is then disregarded for their own faulty reasoning.

I have also seen some mfrs who request the type II anodize. Lastly I have seen where the mfr actually has a guard on site (may have been an armed guard) during all processing and components are checked after nearly every step along with serial number verifications to say the least.

A. Hi, Larry. Your situation isn't clear to me. You say you are speaking of a fastener, but it is unusual for a nut or bolt to be made of aluminum at all, much less anodized aluminum, so what kind of fastener are we speaking of?

May I assume that you are a hobbyist with a small number of these parts, rather than an industrial metal finisher? An anodized surface is like a honeycomb, with the dye where the honey would go; then the walls of the honeycomb are expanded to lock the dye in so you cannot change the color except by stripping the anodizing off and re-anodizing first.

Regards,

A. Hi again. The anodizing can be stripped in a mixture of chromic-phosphoric acid, and then the article re-anodized, and left undyed in natural color, and sealed. But depending on the alloy, it's hard to keep the aluminum "clear" during anodizing (the copper and other alloying materials will darken it) -- that's probably why they're only available in black.

Alternately the anodizing can be stripped and the article electroless nickel plated. Either will give a hard surface, but both involve some dimensional changes that must be studied, as dimension will be lost when the anodizing is stripped, and added back when it is re-anodized or plated. And the adhesion of the electroless nickel in this application may be questionable.

These processes aren't easy and I think you should try to talk to a plating shop about them. Good luck.

Regards,

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"Chromating - Anodizing - Hardcoating"
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A. You must make sure all of the anodizing is off. Inside and out. My concern with plating on aluminum alloy for guns is the durability. When you fire a gun it can expand slightly or have parts that make hard metal contact when firing. It might be possible to do. Keep in mind some tolerances may be effected.
I have done some alloy pistols (automatics); sometimes the frames don't hold plating for long because of the slide traveling on them.

A. Hi James. It is usual to chemically strip anodizing from aluminum rather than blast it off. caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] (sodium hydroxide) is often used for this purpose by anodizing shops, but this will also attack the aluminum if left too long. So even better is a chromic-phosphoric acid mix that dissolves anodizing but not aluminum. You can search the site with the key words my reply uses, and read a good deal about stripping anodizing from aluminum.

As Frank's reply suggests, electroplating onto aluminum is a little problematic in terms of durability. The issue is that aluminum cannot be electroplated onto directly, but requires a zincate immersion plating process first, which does not offer the same adhesion as direct electroplating. If done properly it can work fairly well (thousands of miles of aluminum bus bar has been copper plated), but Frank's caution is much appreciated. Good luck.

Regards,

A. It needs to be professionally heat treated. Anything less and you put your life in your hands.

A. Would you seek advise on paint balls from a metal finishing site? No? Then why seek metal finishing advise from a paint ball site?

Use the search feature here to find much information on "hard coat anodizing". You will find that it is not a simple process you can do successfully in your garage for a few dollars.

A. Hi Donald. Sorry, but I don't know enough about firearm design to know whether heat treatment (which effects the strength of the component) is required, or whether anodizing (which effects mostly the surface hardness) is sufficient.

While most metal finishing shops are not licensed to work with firearms, some are. I find it extremely hard to believe that the position of the ATF is that owners with no firearm design knowledge and no metallurgical knowledge are expected to safely maintain them, and are forbidden to receive help from licensed professional services. Best of luck.

Regards,

A. Chris

Possible yes, likely, no. Damage would be visible and it likely would not hurt the performance of the device.