Anodized Aluminum

[bob4432]

how non conductive is hardcoat anodized Al (type III)? does it make the Al an insulator or just cut down on its conductive properties and not totally destroy them?

also, does type II anodizing do the same in ways of conducting electricity?

 

[Paperdoc]

Anodizing Aluminum simply means making its surface oxidize (which it will do slowly, anyway) quickly, forming a relatively thicker Aluminum Oxide layer than might naturally happen. Now, Aluminum Oxide is not a good conductor, so you're sort of growing an insulating layer in place on the metal. However, that layer is thin and not very tough mechanically, so it can be scraped off down to bare metal again. So any abrasion can allow contact with the good Aluminum conductor properties. I am not familiar enough with the types of anodizing to offer any info on their relative merits, including hardness / abrasion resistance.

 

[silverpig]

Originally posted by: Paperdoc
Anodizing Aluminum simply means making its surface oxidize (which it will do slowly, anyway) quickly, forming a relatively thicker Aluminum Oxide layer than might naturally happen. Now, Aluminum Oxide is not a good conductor, so you're sort of growing an insulating layer in place on the metal. However, that layer is thin and not very tough mechanically, so it can be scraped off down to bare metal again. So any abrasion can allow contact with the good Aluminum conductor properties. I am not familiar enough with the types of anodizing to offer any info on their relative merits, including hardness / abrasion resistance.

I have hard anodized cookware and the oxide is very tough and quite thick. Normal aluminum behaves as you said though... a thin oxide layer, which is a very good insulator, forms rather quickly but is brittle and easily broken through.

 

[Born2bwire]

It's about infinitely away from being a perfect conductor.

 

[bob4432]

thanks for the info. i think i found what i was looking for -

* Corrosion Resistance (336+ Hours salt spray resistance per ASTM B117)
* High Durability (file hard, 60-70 on Rockwell C-scale)
* Electrical Insulation (800 V / mil thickness)

i knew type III was pretty thick but just didn't know how well of an electrical insulator it is. so w/ this info, say i have a anodized Al heatsink in a compuer, and it falls onto the m/b, in theory it should not short anything out correct? assuming that the anodizing has not been compromised.

 

[f95toli]

Aluminium oxide is routinely used as a high-quality insulator in microelectronic circuits, i.e. high-quality aluminium oxide is a VERY good insulator and won't short anything.

 

[bob4432]

thanks again

 

[BladeVenom]

Originally posted by: Paperdoc
Anodizing Aluminum simply means making its surface oxidize (which it will do slowly, anyway) quickly, forming a relatively thicker Aluminum Oxide layer than might naturally happen.

It can also radically change the surface structure. I don't know how much that makes a difference for electrical conductivity, but it's very important for decorative purposes.