Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Refinishing AR15 receivers: high shine plating? anodizing?
Q. IF ANODIZING HAS DEPTH AND WILL COMPROMISE MY FASTENER SURFACE, WHAT CAN I TREAT/AND COVER AN ANODIZED SURFACE WITH TO CHANGE IT'S COLOR IN A DURABLE SURFACE?
Larry Baker- Coalton, Ohio, USA
April 30, 2008
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,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 30, 2008
Q. Thanks for the followup Ted, What I am doing is building a custom AR15. I was able to purchase a titanium lower receiver and build it from scratch. However when building the upper portion of the firearm it is ONLY available in an anodized (BLACK) color. I want it to be silver in color. This Upper has many tight tolerances that have other metal surfaces either drilled into it, such as pins that push in and out of holes and other metal surfaces internally that rub against it. I can live with the anodized interior but I want the surface to be silver.
So if I can't remove anodized from aluminum what can I cover it with that is EXTREMELY durable?
- Coalton, Ohio, USA
May 6, 2008
A. Hi again. The anodizing can be stripped in a mixture of chromic-phosphoric acid, and then the article re-anodized, left undyed in natural aluminum color, and sealed. But depending on the alloy, it's hard to get the aluminum "clear" and keep it clear during anodizing (copper and other alloying materials will darken it).
Alternately the anodizing can be stripped and the article nickel-chrome plated. Both approaches 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.
These processes aren't easy and I think you should try to talk to a plating shop about them. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 2014
Multiple threads merged: please forgive chronology errors :-)
Q. Hello, all.
I am in the infancy of a custom rifle project. I have a mil-spec lower receiver for an AR15. I've had the original type III hard coat anodizing blasted off, crudely I'll admit.
My goal is to refinish with a high gloss metallic. I'd like a gold or chrome/nickel type appearance. You guys and gals may be my last hope. All other contacts thus far have not been helpful.
Thank you.
part-time 'smith - Norwich, Connecticut, USA
March 24, 2009
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.
- St. Louis, Missouri, USA
April 6, 2009
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 appreciated. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
How to harden aluminum for AR-15 lower receiver
I recently Purchased a 80% finished lower receiver for an AR-15 rifle. My problem is if anyone other than me does anything to it then the receiver is now illegal. Now the big question- I tried anodizing a chunk of 7075t aluminum with instructions from a paint ball web site. I burnt it up. Can aluminum be hardened any other way like annealing. Your advise will be greatly appreciated since I cannot have this professionally done.
Donald M [surname deleted for privacy by Editor]hobbyist - Kannapolis, North Carolina
2006
A. It needs to be professionally heat treated. Anything less and you put your life in your hands.
Bill Graysonmetal finishing - San Jose, California, USA
2006
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.
Jeffrey Holmes, CEF
Spartanburg, South Carolina
2006
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 very 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 anyone. Best of luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Chemical Resistance of Hard Anodize Mil-A8625, Type III
May 1, 2011Q. Hello, I have a question about the chemical resistance of Hard Anodize Military A8625, Type III Class II finish on my AR-15 rifle.
I recently touched up some bare metal on my rifle barrel with Birchwood Casey's Perma Blue
⇦this on
eBay or
Amazon [affil links] metal bluing chemical and a little bit of it may have gotten in contact with my aluminum receiver. My receiver is made from 7075 T6 Aluminum with the above mentioned Mil Spec finish. Is there any possibility of the Perma Blue doing any damage to the hard anodized finish on my receiver ?
Here is the listed chemicals for a 3 oz. bottle of Perma Blue per the MSDS:
Description Weight
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Selenious Acid 3%
Nitric Acid 3%
Cupric sulphate 3%
Water 91%
Curiously enough, Aluminum Black by Birchwood Casey
⇦[Aluminum Black on
eBay or
Amazon [affil links]
which is used to touch up nicks and scratches in aluminum includes the above mentioned chemicals minus the nitric acid, but three additional chemicals which are Phosphoric Acid, Fluoboric Acid, and Nickel sulphate.
I would appreciate any and all replies from the professionals in the anodizing industry here.
I should add that I always have a coat of BreakFree LP (Lubricant/Preservative) on my rifles including the upper and lower receivers.
Thanks again and I am looking forward to any replies to my concerns.
- Mantorville, Minnesota, USA
A. Chris
Possible yes, likely, no. Damage would be visible and it likely would not hurt the performance of the device.
- Colorado Springs, Colorado
May 5, 2011
Re-anodizing hand cut feed ramps in an AR platform upper receiver
Q. I have a rifle barrel that has M4 style feed ramps cut into the extension, and an A2 standard upper receiver that has no feed cuts. The upper receiver has a hard coat anodizing.
I want to hand Dremel
⇦this on
eBay or
Amazon [affil links] the cuts into the receiver myself, like many others have done, to mate up the extension cuts into the receiver. However, I do not want to leave the raw aluminum exposed because of future wear. This is a very small modification and is not an aesthetic feature, just utility. What can I do to re-anodize these very small cuts?
Thanks,
Jesse
Hobbyist - Olympia, Washington USA
February 23, 2016
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