What are these cheap Raspberry Pi cases made out of?

[adjustttt]

Found these super cheap RPI cases on Ali express
https://www.aliexpress.com/item/Raspberry-Pi-Aluminum-Case-Silver-Case-Metal-Enclosure-Compatible-with-Raspberry-Pi-3-Raspberry-Pi-2/32742883169.html
But what are they made out of?
The listing says aluminum but they have a weird dull silver color to them
Could it be anodized? Or some kind of cadmium or something 
I am considering buying 10, these seem really good for clusters especially compared to the aluminum competition which is if I remember correctly, are 80 dollars per case.

[ataradov]

I think they are painted. And they are probably made out of some cheap aluminum alloy like silumin.

[ebastler]

The vendor says that it's aluminium alloy, not pure aluminium. Aluminium alloys with silicon and/or magnesium can look a darker grey, apparently. Or maybe it is even anodized?

I don't think it is painted; the color looks too even on the inside. Low-cost spray painting is typically just applied to the outside, with some "fog" visible inside. And since they claim to have two cooling fingers to touch the main chips on the Raspberry, painting it from the inside would actually be detrimental.

[pigrew]

I like the case, though I worry that the "heat sink" spires may crush the ICs? Perhaps a soft thermal pad is needed along with grinding down the case?

[ebastler]

I like the case, though I worry that the "heat sink" spires may crush the ICs? Perhaps a soft thermal pad is needed along with grinding down the case?

Yes, I've been wondering. With the burrs from the mold still visible, these fingers don't look like they will make decent thermal contact anyway. Hopefully they are designed to leave a small gap, to be filled by a thermal pad.

Well, you can always file them down if they are too long!

[David Hess]

The vendor says that it's aluminium alloy, not pure aluminium. Aluminium alloys with silicon and/or magnesium can look a darker grey, apparently. Or maybe it is even anodized?

In other words, pot metal.