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Author: Subject: How thick can an anodized layer be?
Tacho
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[*] posted on 30-11-2007 at 05:51
How thick can an anodized layer be?


In the aluminum anodizing process, does the oxide layer grows indefinitely as long as current flows? Or how thick can it get?

My intention is to anodize a tube to electrically insulate it. This way I can wind Ni-Cr wires directly around it to make a mini hot air gun.

Thanks.
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jpsmith123
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[*] posted on 30-11-2007 at 09:16


Hello Tacho,

I admire your resourcefulness, but is it worth it to even fool around like that when you can get a heat gun for $10.00? (I would think in Brazil there must be something similar?)

Anyway, here's an article from the Electrochemistry Encyclopedia that might be helpful.

One concern I would have would be the difference in thermal expansion between the metal and the oxide, especially if the oxide were thick and subject to repeated thermal cycling.
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12AX7
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[*] posted on 30-11-2007 at 10:26


Hardcoat may suffice. I know electronics professionals (good ones :P ) who have been known to mount transistors on hardcoat heatsinks. It's also very thermally conductive, being aluminum oxide.

Aluminum goes up to 500V or so- think aluminum electrolytic capacitors. As the anodization grows, the voltage must be increased.

Tim




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Tacho
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[*] posted on 3-12-2007 at 02:48


Thank you.

The link ( Electrochemistry Encyclopedia ) is the best information on anodizing I have seen so far.

My Idea is really a small scale thing and, as Tim pointed out, oxide insulation layers can be useful in many other projects. Besides, I really never saw one of those for sale for U$10 (or equivalent). Bless China.
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Nixie
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[*] posted on 17-12-2007 at 04:59


Quote:
Originally posted by 12AX7
It's also very thermally conductive, being aluminum oxide.

Bah, you can get beryllia insulators from eBay.




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unionised
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[*] posted on 17-12-2007 at 13:03


You can get a fair few carcinogenic things on eBay if you look hard enough.
I don't know how thick a layer you can get but there's another neat trick you can do. You can anodise a layer of oxide onto the Al then dissolve away the Al from the other side with I2 soln. That way you might get an Al2O3 tube without the metal.
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[*] posted on 17-12-2007 at 14:43


Quote:
Originally posted by unionised
You can get a fair few carcinogenic things on eBay if you look hard enough.

How is it carcinogenic? Only the dust is. Cut/drill under water and it's perfectly safe (the diamond bits you need to work this hard ceramic are intended for wet use anyways, as they overheat otherwise).




\"Good is a product of the ethical and spiritual artistry of individuals; it cannot be mass-produced.\" --Aldous Huxley
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