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Spent the time to pull the copper cores out of some heat sinks.

To find out they are copper-coated aluminum and could’ve stayed in place?!

Argh.

Is this always the case or do I need to scratch test each one?

I’ve seen copper-zinc alloys before and copper nickel. Never seen one copper plated.

Sorry for the bad luck.

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Seems highly unlikely they would press fit aluminum into an aluminum heatsink...but who knows.

I'll point out a few things:

The weight in your hand should almost automatically tell you if it's copper or aluminum. Heavier = copper.

The removal and pressing of the copper will leave some amount of aluminum on the copper.

Heating the whole thing will usually make the copper drop out with no to almost no effort.

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Here to learn more so I can recycle more
My grades are my own opinion and not an official grade from Boardsort

If it’s heavy-ish, check it with a high power magnet. Make sure it’s not nickel

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Definitely heavy. I have six of these of different sizes and shapes and all feel dense/heavy for their size

I have two suggestions.

First is really etch or gouge or cut into it and make sure it’s really aluminium and not copper
Second, again, grab a magnet. Make sure you don’t have nickel.

As marked Pointed out, it makes no sense shoving a piece of aluminium into a block of aluminium for a heat sink.

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