Quick question about colored aluminum

Quick question I havn't seen asked before.

I've been breaking down a lot of computers and electronics and have accumulated a lot of heat sinks. Most are normal silver color, but a few the metal has had something added so that it is green, black, red, etc.

I realize that it probably varies from yard to yard, but was curious if your yard accepts this with the rest of the extruded aluminum. Last thing I want is a load downgraded because of a few random pieces.



Thanks for any input.

Color doesn't matter at my yard

Originally Posted by drozenski

Color doesn't matter at my yard

Thanks, which yard do you go to? We live in the same town.

Its just anodising, don't worry about it.
On Ali theres a thin (at the start) layer of clear aluminium oxide.
In the metal platers they form a thicker oxide layer on the surface of the ali & at the same time they have it dipped in a dye vat.
As the oxide builds up it traps the dye iside the crystal matrix & thats what the colour is. Thin dye in clear oxide.

When they resmelt the Ali, the oxide comes off, floats up to the top with the now destroyed dye compound.
They might add cryolite or flouride or something to resmelt the oxide into ali or something like that.

Its just like paint but seethru.
Ali oxide is hard as diamond almost, thats why they do it too, makes the Ali more wear resistant.

Originally Posted by Mechanic688

Just make sure it doesn't have a copper insert or some are all copper heatsinks.

Thanks for the heads up.

I broke open an old server I got the other day that had a huge solid copper heat sink that weighed about 3 pounds. I scratch test all of the heatsinks that aren't obviously aluminum just to make sure since someone posted on here that sometimes the silver colored ones are plated copper.

Originally Posted by eesakiwi

Its just anodising, don't worry about it.
On Ali theres a thin (at the start) layer of clear aluminium oxide.
In the metal platers they form a thicker oxide layer on the surface of the ali & at the same time they have it dipped in a dye vat.
As the oxide builds up it traps the dye iside the crystal matrix & thats what the colour is. Thin dye in clear oxide.

When they resmelt the Ali, the oxide comes off, floats up to the top with the now destroyed dye compound.
They might add cryolite or flouride or something to resmelt the oxide into ali or something like that.

Its just like paint but seethru.
Ali oxide is hard as diamond almost, thats why they do it too, makes the Ali more wear resistant.

Fascinating, thanks for the info. Just what I was curious about.