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Old 12th November 2012, 11:17 AM   #1
Salar is offline Salar  Germany
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Default Looking for State of the Art Aluminium Alloy

Hi to all,
I am not talking about some obscure alloy using kryptonite.
I am talking about ordinary alloy, which is garuanteed garuanteed in purity and homogenous material structure.
As one example, this alloy needs rest and cool down in a controlled environment.

The back-story why I am asking:

Anodizing shows impurities in the base material because the alumunium-oxide layer applied add refraction.
You will not see these impurities in the untreated material. Only after anodizing. I does not matter wether you use dye or not.
The problem: You will not find any hints about the purity/quality of any aluminium.
As one example EN-AW 6060 (Al 0.5Mg 0.5Si Fe) is very suitable for anodizing but can be produced good or bad in the foundry.
A german producer of aluminium front panels for High End audio told me, he once had a loss of 30% while anodizing the front panels because of badly produced aluminium.
Every third front panel had to be rashed. The aluminium was bought from a intermediary.
He overcame this problem by ordering 10 tons of aluminium directly from a foundry with tight definitions.
But I do not have those means and can only buy from an intermediary.
I even visited an aluminium fair this year to find one intermediary who sells high grade aluminium alloy but was not lucky.
YouŽll have to be Apple or Sony to get some tons of well produced aluminium.

Within two years i put my spare time in designing my front panels - (no joke)
and of course I do not want to fail in the very last step, the anodizing process.
So i urgently look good base material to preclude a possible failure.

(BTW if the aluminium was simply painted, there would be no need of having good base material)

But maybe, in this great forum, there is somebody, producer of front panels / cabinets or DIYer deeply involved in aluminium production,
who could kindly help me in finding some well produced alloy? Or has some leftover aluminium plates?
I do not need much, at least 15 mm of thickness, about 500 x 500mm length of the aluminium plate (or 110 x 2000mm minimum as one alternative).

Thanks a lot for you help and hints,
Salar

Last edited by Salar; 12th November 2012 at 11:29 AM.
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Old 20th April 2013, 09:50 PM   #2
Salar is offline Salar  Germany
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Nobody?
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Old 20th April 2013, 10:01 PM   #3
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6061-T6 is usually pretty good.

jeff
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Old 20th April 2013, 10:20 PM   #4
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You might consider fabricating 1.5x the panels you need each from a different supplier. If the 30% anodizing reject rate is representative you should end up with enough useable panels unless your Monte Carlo statistics are unlucky.
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Old 20th April 2013, 10:29 PM   #5
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Aluminum alloy "state of the art" has been the same for quite some time. 6063 architectural aluminum has better finish quality than 6061 but it's not as machinable. All processes have tolerances, maybe even bad hair days. The trick might be to get your material from a mill that wont ship product that fails chemical analysis.

Last edited by Andrew Eckhardt; 20th April 2013 at 10:36 PM.
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Old 20th April 2013, 10:40 PM   #6
Salar is offline Salar  Germany
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Hello Jeff and Andrew,
thank you very much for your answer.
But which mill will ship about 5 kg of state of the art aluminium to a DIYer?

In general getting alloy like 6061-T6 is not the problem. Many traders to get small quantities from.
But getting this alloy carefully cast and wrought is the problem.
A manufacturer for enclosures for High-End audio gear told me, he had a 30% loss as long as he bought aluminium (6060, which is perfect) from intermediaries.
Finally, he ordered the aluminium directly from a foundry, and loss went down to 3%.
Another big problem:
You will see many flaws only after anodizing, not before, because of refraction of the anodized surface.

Flaws in the alloy like

Transverse Seam/Two Wax

contact corrosion

web marks

coarse grains

will become visible after the very last step!


Ironically, there are many other aluminim alloys which do meet very tight specifications because they need to withstand extreme conditions. But they are not suitable for decorative anodisation.

But there is nothing special about 6005 or 6060. So many manufacturers, not necessarily being top notch.

As I described before, companies specialized in milling and anodizing enclosures or any other decorative element of aluminium order from a foundry. Just watch Apples Unibody-Videos.

I canŽt. So I hope to find somebode who answers: Yes, we had this assignment for a company in producing fault free aluminium and there are still some bars left...

Last edited by Salar; 20th April 2013 at 10:52 PM.
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Old 20th April 2013, 10:48 PM   #7
Salar is offline Salar  Germany
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BTW I was told those alloys are suitable for decorative anodisation:
1070 / 1080 (But too soft)
5005 / 5754 (Also well suited for Hard Coat)
6005 / 6060
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Old 21st April 2013, 01:04 AM   #8
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Here in Pittsburgh I have no problems with aluminum that is anodized. I order it masked to avoid surface scratches. In the past when I get large quantities the mill makes it to order. Large quantities are only a few tons. (In steel two tons is a small order.)

Now the aluminum has not been stored improperly, which may be one problem. The other issue is to find an authorized distributor. My favorite local one buys from Alcoa directly. Others buy on the spot market and often have lower prices, but frequently higher and of course less quality control.

The issue of "Certificates of Fitness" is one you should ask about. It gives the batch, test results and history of storage.

So look for an authorized distributor who has the right paper work.

At my local place they have a room full of cut off short pieces that they sell at scrap pricing. You just walk in pick up what you want, they weigh it and the prices are very reasonable. I get heat sinks for pennies.
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Old 21st April 2013, 02:32 AM   #9
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I'm trying to remember what this is a called. But there are two "grades" of the same alloy supplied. One is regular mill stuff and has nothing special about the surface, usually imprinted with standard inked alloy marking, dull, grey.

The other is supplied with a smooth finish, and as Simon said it comes with a clear plastic covering. So far that stuff ends up being fine for anodizing assuming you have worked it properly and not messed it up by embedding nasty stuff in the surface, etc...

I found that surplus/scrap aluminum, if you can find the right physical shape or dimensions, tends to never anodize properly even after machining and surface finishing IF there has been the slightest corrosion, seemingly on the surface! All the little stuff pops right out! Odd how that works.

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Old 21st April 2013, 03:48 AM   #10
JMFahey is offline JMFahey  Argentina
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Quote:
Flaws in the alloy like

Transverse Seam/Two Wax

contact corrosion

web marks

coarse grains

will become visible after the very last step!
Sorry but your friend has been cheated by his supplier.
He has been sold *recycled* and reprocessed aluminum, which can have *anything* mixed in.
From junked motor blocks to beer cans , plus it often has iron filings, copper, whatever you pick by sitting in a junk bin, even sand grains.
Personally I use exactly that kind of recycled aluminum, because a reprocessor melts, rolls and sells me custom sized, no scrap sheets .... but I use painted panels.
When I chemically etch them for better paint grip, I see all kinds of ugly "chemical" blemishes, which in my case do not matter.

But a friend of mine who makes custom Studio equipment (think Neve modules and such), CNC mills his front panels and has them anodized.
He had the same problem you mention on the prototypes, but then the Anodizing guys told him: "go buy from Mr XXX who has the "good" aluminum" and he has never had any problem since.
Rich deep black lustrous anodizing.
By the way, black is the hardest colour to get right
No need for NASA specified aluminum, just get the real stuff from the best suppliers, through an official distributor, of course, who will sell you single sheets.
In Argentina we buy straight from Alcan, ALCOA or Kaiser Aluminum local branches, if you search for an European distributor you'll have no problem.

Definitely *none* of the problems you mention, specially if you buy "pure" aluminum (no exotic alloys) which is electrolytic, nothing else added, so it's truly homogeneous.
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