AR Upper aluminum flaking, won't stop

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[ARCHIVED THREAD] - AR Upper aluminum flaking, won't stop

Posted: 8/28/2016 1:45:43 PM EDT

***REPOSTED AS REQUESTED***

I bought this upper from Slim at IAS earlier this year and noticed there was some "spotting" on it. I figured it was no big deal and would be fine once i had it bead blasted. Picked it up from Braceman yesterday and the problem still exists. No matter how much sanding, buffing, we do to this, it still flakes. Some flaking on the inside too.

As this is for my 177 build, and I am going to distress it, it might not be a big deal, but.....?
Any ideas or helpful hints. Harlan, Mike?
Thanks everyone,
-Mark

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Posted: 8/28/2016 1:46:28 PM EDT

[#1]

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Posted: 8/28/2016 3:07:54 PM EDT

[#2]

Hmmm....I can only make a guess, and I would guess that corrosion UNDER the anodizing is lifting/flaking the anodized surface. I've seen lots of anodized aluminum parts corrode/flake in industrial applications where they are exposed to harsh conditions. Those uppers could have seen some rather "hostile" conditions in storage over the last 40-45 years. I know that on the day that I spent at IAS I saw many receivers "in the white" that were eaten up with white corrosion. Its the nature of the beast with aluminum.

Posted: 8/28/2016 3:26:54 PM EDT

[#3]

This is in the white. It is Not coated.

Posted: 8/28/2016 4:24:12 PM EDT

[#4]

I had a couple like that from Slim.... you're right, after blasting and sanding, it seemed to keep showing up. I Norrell's coated mine and it seemed to seal it up. I do not think it is a structural or strength issue, just a top layer corrosion/scaling thing after sitting for 40 years. Mine still look and shoot good. I wouldn't sweat it.

Posted: 8/28/2016 5:12:43 PM EDT

[#5]

Wrong thread

Posted: 8/28/2016 6:37:44 PM EDT

[#6]

Wrong thread

Posted: 8/28/2016 8:12:15 PM EDT

[#7]

I had a a1 do that, i had it done in clear hard coat then i painted it.

Posted: 8/28/2016 8:17:33 PM EDT

[#8]

I prefer anodizing, so........?

Posted: 8/28/2016 9:39:21 PM EDT

[#9]

Intergranular corrosion with exfoliation.

Click here for details

John Thomas

Posted: 8/29/2016 1:00:18 AM EDT

[#10]

Quote History

Quoted:
Inergranular corrosion with exfoliation.

Click here for details

John Thomas

View Quote

I would agree with JT's assessment. I recall reading that the early 6061 receivers were doing this in the extreme climate of Vietnam, which was one of the reasons for the switch to 7075. However, this upper is a round-forge, so it should be made from 7075. I guess even 7075 will corrode, given enough time in the "right" environment. Was this upper purchased from IAS "bare", i.e. without anodizing?

Posted: 8/29/2016 2:07:51 AM EDT

[#11]

Just throw it in a fish tank.

Posted: 8/29/2016 2:42:26 AM EDT

[#12]

Quote History

Quoted:
Just throw it in a fish tank.

http://i1332.photobucket.com/albums/w611/barrtjb/A5EFDE30-162A-49B3-B723-9E30BC20473C_zpsfhrely8t.jpg

View Quote

So, what's the story there? A project gone awry?

Posted: 8/29/2016 7:20:16 AM EDT

[#13]

Quote History

Quoted:

So, what's the story there? A project gone awry?

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
Just throw it in a fish tank.

http://i1332.photobucket.com/albums/w611/barrtjb/A5EFDE30-162A-49B3-B723-9E30BC20473C_zpsfhrely8t.jpg

So, what's the story there? A project gone awry?

Boating accident?

Posted: 8/29/2016 8:08:13 AM EDT

[#14]

Buddy put a partial AR build in his fish tank and the upper started delaminating almost immediately.

Posted: 8/29/2016 8:12:47 AM EDT

[#15]

I'd imagine the oils and chemical residue did the fish a world of good too.

Posted: 8/29/2016 8:59:43 AM EDT

[#16]

Quote History

Quoted:

I would agree with JT's assessment. I recall reading that the early 6061 receivers were doing this in the extreme climate of Vietnam, which was one of the reasons for the switch to 7075. However, this upper is a round-forge, so it should be made from 7075. I guess even 7075 will corrode, given enough time in the "right" environment. Was this upper purchased from IAS "bare", i.e. without anodizing?

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:

Inergranular corrosion with exfoliation.

Click here for details

John Thomas

I would agree with JT's assessment. I recall reading that the early 6061 receivers were doing this in the extreme climate of Vietnam, which was one of the reasons for the switch to 7075. However, this upper is a round-forge, so it should be made from 7075. I guess even 7075 will corrode, given enough time in the "right" environment. Was this upper purchased from IAS "bare", i.e. without anodizing?

yes bare I had Brace blast it for me

Posted: 8/29/2016 9:09:31 AM EDT

[#17]

Quote History

Quoted:

Inergranular corrosion with exfoliation.

Click here for details

John Thomas

View Quote

Thanks John,

Doesnt look like there's a fix.

Posted: 8/29/2016 2:51:24 PM EDT

[#18]

This from Victor at US Anodizing:

Hi Mark,

Nice to hear from you! The upper you have is an Arsenal upper, that had the anodizing removed (blasted) and was never re-anodized.

We have anodized many of the same uppers here, very familiar with them. I have seen this pitting or flaking many times here, most of them on 7075 alloy parts.

There several things that can cause this pitting or flaking;

1. Impurities in the forging die or alloy), or in the hardening process.

2. Pitting from exposure to humidity, from having those areas (bare) without

anodizing.

The alloy 7075 is a hard alloy, but it has its problems. The amount of Zinc in the alloy can cause pitting or flakes if left bare and expose to water or humidity. The Zinc in the alloy will cause a galvanic reaction, if left bare and expose to water or other chemicals.

The only way to repair the areas affected is to grind or sand the flaking off, and re-anodize. Keep in mind the receiver will need a thicker anodizing film put back, to bring it back to specs.

Hope this helps,

Victor