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Old May 24, 2006, 05:04 PM   #1
GLM
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Parkerize aluminum?

I recently traded for an 80% AR15 lower that is unfinished. The man I traded with said that he parkerizes his aluminum parts. I was under the impression that aluminum couldn't be parked and that aluminum receivers needed to be anodized. If I am wrong, is the procedure for parking aluminum the same as other metals? For that matter, can I just use some sort of spray on finish like gun-kote and not anodize or park my lower?
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Old May 24, 2006, 06:11 PM   #2
Dfariswheel
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Aluminum CANNOT be parkerized.

Aluminum must be either anodized or coated with some type of gun coating.

Brownell's sell several very good coatings, Aluma-Hyde being a one of the best.
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Old May 24, 2006, 06:27 PM   #3
mete
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Parkerize is a zinc or manganese phosphate coating for steel. It can't be used on aluminum. The general coating for aluminum is anodizing which builds up an oxide coating electrolytically. The coating is pourous so that is sealed with wax which may be dyed different colors.
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Old May 24, 2006, 07:46 PM   #4
JNewell
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What you need is "type III" or "hard" anodizing. If you have it finished with regular or type II anodizing you will find that the aluminum wears pretty badly.
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Old May 25, 2006, 06:53 PM   #5
Bill DeShivs
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Aluminum can not be Parkerized, but it can be painted to match. Anodizing does not use wax. In anodizing the pores of the aluminum are opened, the metal is dyed, and the pores closed. All anodizing is "hard." A layer of aluminum oxide is built up on the surface. This layer is thin and will wear through.
Aluminum can be plated with electroless nickel.
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Old May 25, 2006, 06:58 PM   #6
JNewell
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Quote:
All anodizing is "hard."
This is true, but not all anodizing is equally hard. Type III results in greater and deeper hardness. The mil spec calls for Type III anodizing. Anything less is...less.
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Old May 26, 2006, 02:24 PM   #7
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To avoid confusion:

If one re-reads Mete's post caraefully, he does not state that anodizing itself employs wax, but that wax may be applied as a sealant in conjunction with the dying process after anodizing is complete. Mete is a metallurgist and is not likely mistaken on this point.

The pores in question are not in the metal, but rather in the aluminum oxide layer created by anodizing. It is the oxide that may be dyed and sealed, not the metal. Failure to seal the oxide may result in blooming under adverse conditions.

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Old May 26, 2006, 05:00 PM   #8
Bill DeShivs
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Nor am I an expert, but his post said "The coating is pourous so that is sealed with wax which may be dyed different colors."
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Old May 27, 2006, 03:19 PM   #9
Unclenick
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Bill,

Correct. I read Mete's post like this:

"The general coating for aluminum is anodizing which {is a process that} builds up an oxide coating electrolytically. The {oxide} coating is pourous so that {it may be} sealed with wax {and/or} dyed different colors."

I only mentioned it because I couldn't see any way to read into Mete's post that he had said the anodizing process, the part that builds up the porous oxide layer, involved wax in any way, which is how I read your response? Dyeing and sealing are also common post-Parkerizing options as well as being post-anodizing finishing steps (see: DOD-P-1632F).

Maybe this is just a question of where the term "anodizing" starts and stops? I see the anodizing part as completed as soon as the electricity is turned off. The optional dye and sealant (be it wax or something else) all come after the part is no longer serving as an anode and are not limited to any one dye or sealant. That may be the source of the confusion. I believe hard wax with a high melting temperature is a common anodizing sealant, but I doubt you would find either it or dye on anodized aluminum exhaust system parts. Neither could withstand the temperatures. So final steps will vary with the intended application.

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Old May 27, 2006, 03:45 PM   #10
mete
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exactly Unclenick ! Often it's the oxide layer that provides corrosion resistance rather than the metal itself.This is true of stainless steel. Metals actually oxidize easily in air but for better corrosion resistance the oxide is built up .In stainless steel it should be given a "passivation" treatment which builds up the oxide with acids .A stainless steel gun which rusts easily has not gotten the proper passivation.Aluminum has it's oxide layer built up with an electrolytic process . The oxide is pourous and those pours sealed with a wax .That's how we can get aluminum guns in decorator colors !! The oxide is white but the wax is dyed.
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Old May 29, 2006, 02:57 AM   #11
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"...said that he parkerizes his aluminum parts..." He's confused. Like the others have said, Al doesn't take parkerizing. Seems to me that current issue M-16/M-4's get powder coated. That'd be baked on powdered paint. I may be confused myself though.
As daft as it sounds, BBQ paint will do nicely. It's made for AL, is heat resistant, cheap and easy to find in any hardware store. It's flat black too.
Having any finish put on by a metal finishing shop won't be cheap.
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Old May 29, 2006, 12:28 PM   #12
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Anodising is most often dyed using vegetable or sometimes aniline dyes then washed in boiling water to close up the pores, As Mete says the final process is usually a silicon based wax which closes in any open pores and provides a further protection. The type of anodising specifyies the depth of oxide which basically increases with the time in the electolytic acid bath, it is not just simply leaving it in longer, like most things there are other considerations.
But Anodised aluminum is durable and attractive used sensibly. Stailnless steels are passivated to speed up and enhance the formation of the oxide layer, particularly on cast martensitic steels where the iron is concentrated on the surface and so tends to rust, passivating removes this iron and leaves a chrome bearing layer which oxidises providing protection. Excluding the air from any of the stainless steels will cause it to corrode like ordinary steel, always makes me smile in the ads for stainless screws and bolts into wood and such " all rusting problems over" etc, only on the head you can see is reality.
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Old May 29, 2006, 01:01 PM   #13
JNewell
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Quote:
Seems to me that current issue M-16/M-4's get powder coated. That'd be baked on powdered paint.
There may be civilian manufacturers doing that but the milspec calls for Type III hard anodizing. Although the lower receiver is a relatively low-stress part, things like pin holes do wear and they wear faster if they are not hard anodized.

There's a brief discussion here
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