How to tell aluminum from zinc?

[Zephyr]

I'm tearing apart some old lab equipment that contains cast frames, but I can't determine if they are zinc or aluminum by the weight. (They're painted, but I can always run a file over the surface.) Is there an easy way to figure out which is which? Thanks!

[theirratonalist]

Zinc is 3 times heavier then aluminum by volume. If you break it, it should look grainy. If it's aluminum, it usually bends (if its not cast). If it's zinc, it breaks.

If you plan on scrapping them, you will probably get the same price no matter what. My scrap yard just has one price for cast aluminum, it just needs to be clean, otherwise it is breakage.

[Zephyr]

I put some concentrated crystal Drano on the bare metal surfaces & it seemed to work. Aluminum turned black & zinc didn't. It has to sit for a few minutes, and needs to be rinsed off afterwards. I'd only use this method as a last resort, as playing with Drano is a nasty business (Heed the warning labels!)
Hope this is of some help to others....

[theirratonalist]

I put some concentrated crystal Drano on the bare metal surfaces & it seemed to work. Aluminum turned black & zinc didn't. It has to sit for a few minutes, and needs to be rinsed off afterwards. I'd only use this method as a last resort, as playing with Drano is a nasty business (Heed the warning labels!)
Hope this is of some help to others....

Ah! Chemistry is a scrappers best friend... Well, that and a sawzall.

[boogeyman]

It's been a few years now, but I recall that if you file the metal and put vinegar on the zinc it'll foam up a bit. On the aluminium the vinegar will stay clear.

That's how my grandfather used to test. Think it's the best least expensive way.

[WAres]

if you cant tell by looking at it you better get some acid, zincs turns yellow, aluminum stays clear, die cast turns black

[coinshooter]

Die cast what?

[WAres]

Die cast what?

die cast or pot metal samething

[hobo finds]

Die cast what?

zinc