Help!! Need an enclosure FAST...

anodizing is absolutely horrible

a good thermal insulator if it is thin enough. What type of anodizing are you talking abougt? How bad is this supposed to be? I'm not familiar wit h the "horrible" spec.

sink fins

e a transistor was bolted to the inside made a big difference

ct like the anodized surface not being very flat? Anodized layers are less than 1 mil up to 5 mils depending on type. It's pretty hard to get much i nsulating properties in 5 mils of thickness. How many watts? How large of a surface? What was the observed temperature change?

tt

?1 3 cm^2 at 5 mil thickness (hard anodizing) would be about 70 W/K. T hat would seem to be less than one degree Kelvin from removing the anodized layer.

?K?1 and thought no problem, but then I looked up numbers for ano dizing and found multiple papers where they had measured it as more like 1

ts, with the thickness already having been taken into account or something? That's what I would expect from a paper analyzing thermal conductivity of anodizing.

On Saturday, May 11, 2019 at 8:58:22 PM UTC-4, Lasse Langwadt Christensen w rote:

he anodizing is absolutely horrible

is a good thermal insulator if it is thin enough. What type of anodizing a re you talking abougt? How bad is this supposed to be? I'm not familiar w ith the "horrible" spec.

at sink fins

ere a transistor was bolted to the inside made a big difference

fect like the anodized surface not being very flat? Anodized layers are le ss than 1 mil up to 5 mils depending on type. It's pretty hard to get much insulating properties in 5 mils of thickness. How many watts? How large of a surface? What was the observed temperature change?

watt

??1 3 cm^2 at 5 mil thickness (hard anodizing) would be about 70 W/K. That would seem to be less than one degree Kelvin from removing the anodi zed layer.

?K?1 and thought no problem, but then I looked up numbers for ano dizing and found multiple papers where they had measured it as more like 1

nits, with the thickness already having been taken into account or somethin g? That's what I would expect from a paper analyzing thermal conductivity o f anodizing.

Did you actually read the paper? It is not clear to me just what they were doing. Without the paper you can't tell if what they were measuring is th e same as the anodizing done for electronics.

Their results are 20:1 different at least from other published results. So it seems hard to believe without understanding what they measured and how it would apply to other uses. Then there is always the matter of unverifie d research. They seem to want $35 for the paper.

Anodising layer is very porous. You can see even from the abstract that reduces thermal conductivity radically.

anodizing and found multiple papers where they had measured it as more like

units, with the thickness already having been taken into account or someth ing? That's what I would expect from a paper analyzing thermal conductivity of anodizing.

were doing. Without the paper you can't tell if what they were measuring i s the same as the anodizing done for electronics.

So it seems hard to believe without understanding what they measured and how it would apply to other uses. Then there is always the matter of unver ified research. They seem to want $35 for the paper.

Radically??? Worse case, it would be approximately in proportion to the po re area, but when filled with heat sink grease, I expect somewhat less. Ar e you suggesting the anodizing is well over 50% pores? To explain a 20:1 d ifference it would need to be 95% pores. Sounds more like a net, holes tie d together.

I can't tell anything from the abstract about the thermal conductivity of a nodizing on heat sinks because I don't know anything about how they created the anodizing in the study or how they measured the thermal conductivity. Can you?

But it's so thin! does this number really matter?

Anodising is very porous, it seems. That's how it takes dye.

Clifford Heath wrote in news:CycCE.12432$% snipped-for-privacy@fx43.iad:

Bare Aluminum is porous. Anodizing is not so much as a hard anodized Aluminum surface is non conductive. If it were 'porous' as you state, it would fail at a very low voltage. It does not, so the surface treatment must be pretty complete.

The final step in anodizing Aluminum is a water finish to close up the 'pores' on the oxidized layer. That is also when they add the tinting. After that prossess the pores are sealed up by the water reacting with the oxide layer.

Chem etch and chem film is NOT anodizing.

On Saturday, May 11, 2019 at 8:58:22 PM UTC-4, Lasse Langwadt Christensen w rote:

he anodizing is absolutely horrible

is a good thermal insulator if it is thin enough. What type of anodizing a re you talking abougt? How bad is this supposed to be? I'm not familiar w ith the "horrible" spec.

at sink fins

ere a transistor was bolted to the inside made a big difference

fect like the anodized surface not being very flat? Anodized layers are le ss than 1 mil up to 5 mils depending on type. It's pretty hard to get much insulating properties in 5 mils of thickness. How many watts? How large of a surface? What was the observed temperature change?

watt

??1 3 cm^2 at 5 mil thickness (hard anodizing) would be about 70 W/K. That would seem to be less than one degree Kelvin from removing the anodi zed layer.

?K?1 and thought no problem, but then I looked up numbers for ano dizing and found multiple papers where they had measured it as more like 1

nits, with the thickness already having been taken into account or somethin g? That's what I would expect from a paper analyzing thermal conductivity o f anodizing.

Huh, Interesting thanks. 5 mil for the anodized layer seems like a lot.

(OK 5 mil is 'common'

George H.

The oxide layer formed during anodizing is porous and kind of "fluffy" and damages easily but takes dye well. At this point you can wipe most of the oxide off with your hand. The final step in anodizing with or without dye is to simmer in boiling water, usually with nickel acetate and maybe other proprietary goodies added. This changes the crystal structure of the aluminum oxide, collapses the pores in the oxide layer which traps the dye making the color durable, and the densification greatly improves the abrasion resistance of the oxide layer.

I believe that the porous film is sapphire (Al2O3). It has to be porous so that ionic current can still pass through it, or the oxide stops growing. I don't think further chemical processing touches the sapphire, just the underlying metal and the pores.

The original process just used the hot water to form aluminum hydroxide to fill the pores. That works OK for some things, but as you say, you can fill them with other stuff, e.g. fluorpolymers for Tufram/Polylube.

Cheers

Phil Hobbs

the anodizing is absolutely horrible

g is a good thermal insulator if it is thin enough. What type of anodizing are you talking abougt? How bad is this supposed to be? I'm not familiar with the "horrible" spec.

heat sink fins

where a transistor was bolted to the inside made a big difference

effect like the anodized surface not being very flat? Anodized layers are less than 1 mil up to 5 mils depending on type. It's pretty hard to get mu ch insulating properties in 5 mils of thickness. How many watts? How larg e of a surface? What was the observed temperature change?

?1 3 cm^2 at 5 mil thickness (hard anodizing) would be about 70 W /K. That would seem to be less than one degree Kelvin from removing the an odized layer.

anodizing and found multiple papers where they had measured it as more like

units, with the thickness already having been taken into account or someth ing? That's what I would expect from a paper analyzing thermal conductivity of anodizing.

minum)

Depends on what you ask for. There are multiple types of anodizing. Chrom ate is typically 1 mil or less. Sulfuric acid is used to make anodizing up to 5 mil... well, I think I read it was sulfuric acid. Wikipedia has an o k page and lots of anodizers also have pages. The thicker sulfuric acid an odizing is called "hard" anodizing.