Telling the difference between zinc and aluminum

As most of us know neither zinc (cast) nor aluminum are magnetic. They both also show a shiny silver color if you use a file on them, and neither spark if you use a wheel on them. So how can a person definitively tell the difference between the two? Most of the time I can tell generally by the weight in relation to the size, but sometimes the weight is just so that I cannot for sure say one way or another. Anyone have a tried and true method to tell these two from each other?

I know how, Zink starts with a Z! what about a hardness test, isn't Al fairly soft?

lol..Bear your a freaking trip buddy.

I have nothing useful to add other then the above, carry on!

Sirscrapalot - Lol'ing at the Bear

I find some small heat sinks in boards that I think are zinc. I don't accumulate much of them, and my yard does not buy zinc, so they end up in my aluminum. Shhh.

My yard checks with a file. They say zinc is a duller gray, aluminum is more white.

Originally Posted by erewen

I find some small heat sinks in boards that I think are zinc. I don't accumulate much of them, and my yard does not buy zinc, so they end up in my aluminum. Shhh.

Ask your yard if they buy "Die Cast"

That is the more common term for zinc.

Thanks, I will try filing again and double check the shades.

Originally Posted by freonjoe

My yard checks with a file. They say zinc is a duller gray, aluminum is more white.

Usually the die cast (zinc) is a darker grey color. Sometimes you just can't go by weight. I recall when I started the yard guy mentioning 'swirls' or something but all I heard was ''wah wah wah.''

The yard I bring my cast alluminum to lets me throw Zinc in with the cast and pay me cast price. One yard I know of only pays .10 per bl for Zinc.

Dang, 10 cents a lb is horrible. I get 25 cents at the yard I usually go to.

Found this on treasurenet.com... I have some laptop hinges and such that I think might be zinc. If aluminum I plan to melt them down with the 50lbs or so of hard drive cases I've accumulated. Spring fever, time to melt some metal! Anyways, this is what they wrote:

Quote Originally Posted by pepperj
"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."

Die Cast by me is zinc. I will try and do the vinegar thing and see

When a scrap yard talks about die cast, they are talking about Zamak and similar alloys... (see here for details) https://en.wikipedia.org/wiki/Zamak (and Here) https://en.wikipedia.org/wiki/Zinc_aluminium

A Lot of metals can be die-cast, but aluminum and zinc-aluminum alloys are now the most common.

weight is the most common determining factor, Za 8 a common die cast alloy at 82% Zn has a density of 6.3g/cm3 compared to Al at 2.7g/cm3,
so Zinc based die-cast alloys are at least twice as heavy as aluminum,
additionally Zamak will flow into a much thinner wall then aluminum,

the hardness test is no good at all as: an 1100 series Al (almost pure) will be softer then zinc diecast alloys, while 7000 series Al will be much harder.

magnesium based die-cast will have the thin walls, but be lighter then aluminum, it has the very dull color some think guarantees die cast. it dont!

just remember die cast is a process for making parts, not an actual alloy. at the scrap yard they call zinc based alloys die-cast, even zinc anodes, which are around 98% zinc or better.

most likely at the refinery they melt all the zinc based die-cast together, then add zinc or aluminum till they get the alloy they want.


V/r HT1

I find that aluminum has a ring to it and zinc alloys thunk similar to lead.

Originally Posted by t00nces2

I find that aluminum has a ring to it and zinc alloys thunk similar to lead.

the ring test while helpful is definitely not definitive Zamak2 with a hardness of 90 Brinell aged will ring just like an identical shape of 6061, but it will still weigh twice as much

V/r HT1

P.S. I use the ring test, and the manual hardness test both, but it is impossible to teach the "touch" that those sort of test require, some can pick it up, some cannot (shrug)