How do I tell if it's aluminium?

[silentC]

I've got some old pumps and things here that have been chucked out. The housings are some sort of cast alloy, not ferrous (magnet wont stick), could be aluminium. Does anyone know of a way to tell what they are? I'm planning to build a furnace later this year and do some sand casting.

[pawnhead]

Easy. Just get yourself one of these (http://las.perkinelmer.com/Catalog/ProductInfoPage.htm?ProductID=prOTOF2000). I don't think they sell them at Bunnies though.

[silentC]

Guffaw guffaw!!

:p

[rodm]

For casting you are probably going to mix diffent compositions of aluminum anyway so I wouldn't get too worried about the purity. If you scratch it and it is bright and it is about the right weight for alloy then throw it in a bag, hit it with the sledge hammer and chuck it in the pot with the coke cans and mower parts.

[silentC]

Sounds good to me.

Though it could be a zinc alloy. Some of the stuff I plan to make can be made from pot metal but I think some parts need to be aluminium. I'll have to read up on it a bit more.

[Rocker]

The specific gravity of aluminium is 7.7. If you know someone in a Uni geology department with access to a Walker's steelyard, it is fairly easy to measure specific gravity. A bit lower tech than a mass spectrometer, but works fine.

Rocker

[silentC]

Hmm, what I was hoping for was something like the spark test you can use on steel.

I suppose I'll just have to suck it and see. I don't know many geologists, only one retired bloke and he is too far away to be of much assistance in this case :wink:

[Mirboo]

The specific gravity of aluminium is actually 2.7 grams per cubic centimetre. You could work out the volume of a piece by throwing it into a measuring cylinder of water and measuring how much the volume in the cylinder increases. Weigh the dry piece of metal before you throw it into the water and you can then work out its density (or specific gravity).

[Mirboo]

Aluminium is non-sparking.

[Stuart]

So's wood

[silentC]

Yeah I know but I thought there might have been a similar test, you know a rule of thumb type thing. Zinc alloy is non-sparking too (I think) so I can't use that to tell.

I guess I'd need some pretty accurate scales and a cyclinder with accurate graduations. I wonder how close the specific weight of aluminium is to other light alloys like magnesium etc..

[Mirboo]

Magnesium is 1.738 g/cm3 and zinc is 7.14g/cm3.

[Felder]

So's wood

The recycled stuff I was cutting the other day sparked quite nicely.....

[Mirboo]

Flame tests (http://www.amazingrust.com/Experiments/how_to/Flame_Test.html) can be used to determine qualitatively what elements may be present but some groups of metals give similar colours when subjected to such tests. For example, aluminium, magnesium and titanium all produce a silvery/white flame when flame tested. You could do a rough flame test with an oxy torch and without the cobalt blue glass. Be careful though, magnesium burns like buggery if you heat it up too much so just use a small sample.

[silentC]

Magnesium is 1.738 g/cm3 and zinc is 7.14g/cm3.
That would be in pure form though, wouldn't it? An alloy would be less dense perhaps, depending on what other metals are in it?

[Mirboo]

Alloying elements will change the density according to the proportions in which they are present. If your metal is predominantly aluminium then its density will be close to the 2.70 g/cm3 of pure aluminium.

[silentC]

And if it lights up like fireworks when I melt it, it's magnesium!

[Rocker]

The specific gravity of aluminium is actually 2.7 grams per cubic centimetre.

Oops, sorry about that typo.

Rocker

[Mirboo]

And if it lights up like fireworks when I melt it, it's magnesium!

That would be the singed eyebrows test.

[Dan]

Sodium Hydroxide (Drano) reacts with aluminium fairly well, but it might do the same with zinc.:?

[Dan]

The melting points are different by a couple of hundred degrees.

[Bleedin Thumb]

Think outside the square and ring the pump manufacturer up and ask.
Betcha its aluminium alloy.

[silentC]

OK, anyone got the country code for Japan?

My hope is that when I'm up at the tip scavenging or picking up bits and pieces in people's backyards that there will be a way to tell without having to trace the manufacturer and call them. I'm sure there is a simple test of some sort, I just don't know what it is yet. I've got some of Dave Gingery's books. I bet he could tell aluminium from zinc alloy without any special equipment. I'll scan through them and see what I can glean.

[Eddie Jones]

So's wood

Yes, but aluminium non-sparks much better than wood. About 9 on the Eddie Jones open ended non-sparking scale. Wood's only 5.

[Mirboo]

If you've got a volt meter (or perhaps a multimeter?) you might be able to devise a simple test based on the galvanic series (http://en.wikipedia.org/wiki/Galvanic_series). You could use seawater as your electrolyte and measure the voltage difference you get between two pieces of electrically connected metal. Start with known samples of metal to see what voltages you get and then see if you can use the test to work out unknown metals by comparing the results against those of known ones.

[Stuart]

Try rubbing it under your eyes - if it helps keep the sun reflection out, it's zinc.

[buzzy bee]

Hi

So have you got any info on casting, I have allways wanted to try this?

Cheers

Dave

[Grahame Collins]

Assuming you do not want to spend any money,I would go this way.
Ignoring those in the peanut gallery who are not helpful, we have :
A visual ID - silvery bright metal
Physical- light weight-weighs X per cc
But still not conclusive for the absence of zinc.
If you have an oxy or even a LP torch heat a small chunk to melting point.

If zinc is present in the alloy it will flash off before the melting point of aluminium. What will be observed if zinc is there will be a sudden eruption/puff/flash of white smoke and white residue .Do not inhale the smoke -nasty stuff.

My feeling that if it is a pump body it is cast aluminium - which makes it the #5000 series. A google search should give you the percentages of other metals alloyed.

If memory is correct,I think , I have read the aluminium cylinder heads from Nissan and Toyata are good material to melt down for casting.

Does this help ?

Grahame

[Master Splinter]

If its cast, and hasn't rusted, its most likely aluminium if its any sizeable casting.

When you've got your furnace built, just toss a small amount into the crucible to see what happens. Melts with little trauma - aluminium; lots of white smoke - diecast; lots of white smoke and lots of light as it burns the crucible, magnesium; sits there and soaks up heat and doesnt melt; titanium.

Any already cast aluminium is a good candidate for re-melting as it is the right stuff to make nice casting with - extruded aluminium (window frames, shower screens, fold-up chairs) doesn't cast as well plus you tend to end up with more dross in the melt that you have to skim off.

Old mag wheels and cylinder heads are a good source of quality castable aluminium.

[Schtoo]

OK, anyone got the country code for Japan?



+81.

For example, to call, say me, you would need to dial the international dialing code, whatever that is, then the country code, area code and finally the phone number.

So, 0011(?)+81-087-845-XXXX That would get you somewhere in my neighbourhood, seriously.

How's your Japanese? :D


The metal, pick it up. If it's heavy for it's size it will be zinc alloy, if it seems a little light, its ally.

If it is a pump, it is prolly ally. Zinc isn't a really good material for pumperdinkers. Happy now?

(If it's zinc, put it aside for later. Prolly Zamak or similar, which isn't 'pot metal' by a looong &$%^$^% way.)

Since it's already cast, the ally will be great for casting since some alloying componenets will be present, and some residual de-gassing stuff as well. Should result in a nice casting, provided you get everything else right...

Which you won't, so practise with whatever crap you can find first and save the good stuff for where it counts.

As if I would know anything about this... :rolleyes:

[silentC]

Well thank you everybody. Sounds like it's a bit of a guessing game then.

The pump is an air pump (http://www.pumpserv.com/hiblow.htm) from an on site sewarage system (made in Japan) and they are very expensive to replace. In addition to the body, they also have rare earth magnets in them and a few other bits and pieces worth salvaging.

But it wasn't so much this particular item I wanted to identify, was just looking for a rule of thumb to use in general when scavenging. I guess I'll be able to tell when I pick things up after a bit of trial and error.

[echnidna]

As Schtoo said zinc is noticeably heavier than aluminium.
Compare a bit of ally to say a car door handle and you'll soon see the difference.

[joe greiner]

I don't think it matters a great deal. If your scrap is castings, and they look and weigh like aluminium, you're probably good to go.

I'm looking at my 1959 Handbook of Chemistry and Physics, Table of Composition and Physical Properties of Alloys. Specific gravities range in the neighborhood of 2.7 to 2.96, except Alclad (coated sheet) at 2.00, which is NG for casting anyway. Most of the casting alloys have some magnesium and/or zinc and/or other stuff. Alloy number scheme has changed since then, so alloy numbers might not help much. Some alloys with names are:
Lynite, piston: 95Al, 2Cu, 1.5Mg, 0.8Fe, 0.2Si, 0.01Mn
Lynite, piston: 89Al, 11Cu, 0.5Mg
Liberty pistons: 77Al, 21Zn, 1.1Cu, 0.5Fe, Pb, Sn
Sand-casting 214: 96.2Al, 3.8Mg
Sand-casting 195: 96Al, 4.0Cu
Sand-casting 355: 93.2Al, 1.3Cu, 5.0Si, 0.5Mg
Sand-casting 356: 92.7Al, 7.0Si, 0.3Mg
Sand-casting 220: 90.0Al, 10Mg
Sand-casting 112: 89.3Al, 7.5Cu, 1.2Fe, 2.0Zn

My Gingery books are still in a moving box, but IIRC (or maybe from some other book), you can even use beer cans or extrusions, but only for non-structural applications as they're entirely different alloys. Might not pour or solidify very well either.

Joe

[Schtoo]

Beer cans are a disaster, Not worth the effort unless you can squash them into a brick. The thin sides burn up and become slag/dross which just makes it a pain. Also need to make sure they are bone dry before putting them into molten ally or you end up with a small scale bomb. I have never had that happen, and don't plan to try it out.

Al foil has iron in it, but agian you need to squash it into a brick. Extrusions are pretty good and they come out of the sand nice and shiny.

In homebrew applications, the alloy isn't critical, just go overkill on thickness and you should be covered.

Silent, when you go scrounging for scrap ally, keep in mind things, like, Will it fit in the pot? Can you break it down without too much trouble? Is the stuff thick enough to melt down well or will it turn to crap?

I have found that old castings are excellent, as you would expect. Apparently pistons and gearbox casings are the best for almost anything since they cast well. Extrusions are good for general stuff, but you may get some problems, and don't ask too much of the casting.

If you find some good quality zinc based stuff, use it for when you need something with extra strength, since the good zinc alloys are much stronger than ally typically is. This doesn't include old car door handles though, they really are junk and should be treated accordingly.

And if you can melt ally, brass isn't too much further up in temperature. ;)

Google is also your friend. :)

[soundman]

Surely a filing/ cutting/ scraping test would give some indication.

I seem to think that good ally tends to clog files & stuff more redily than zinc.

What about alook at the broken edge.


Dead alloy wheels aparantly are the best quality source of casting material.

A mate of mine used to do the rounds of several local wreckers for casting material....he prefered wheels.

there is a lot of good aloy in modern cars too if you go looking for it.

cheers

[silentC]

OK, all good stuff. Thank you. I'm not quite ready to melt yet, waiting for the weather to cool down a bit. It just came up because I got access to all these old pumps. I'll toss them in a corner and wait until I know more about what I'm doing. Cheers!!

[Randy Korr]

I'd do this outdoors, because any of them can burn.

A propane torch will easily melt zinc. You might even get away with an electric soldering iron.

It will take a very long time to melt a piece of aluminum any thicker than a beer can, and the electric soldering iron probably won't touch it. Magnesium is also high melting. You might catch a thin ribbon of it on fire with the propane torch, but an electric soldering iron shouldn't faze it.

Outdoors is key. If you were here, I'd offer that American pennies are made of zinc, and that would give you a certain piece of zinc to test against.

R. K.

[silentC]

I'd offer that American pennies are made of zinc
I'm happy to receive a few to experiment with. I reckon a tonne or two to start with :wink:

But seriously, I thought they were some copper-based alloy or something? I remember putting one in a machine at the Empire State building and it squashed it flat and stamped a tourist message on it.

[Harry72]

Al foil has iron in it,

Not if you buy "Comalco" its 99.97 aluminium , we use it at work to make custom blends of lead... its the cheapest way of buying it per K.
Your casings would prob be a aluminium zinc alloy, aluminium by itself is too soft so they add zinc to harden it also lowers the melting point of aluminium, if the pumps were made to be portable it would contain a high percentage of magnesium.
I know pure zinc melts at 420C and aluminium/magnesium is about 700ish depending on whats blended in it, its very rare for these metals to be in pure form.
As to refine them to a 99.99 product is super expensive... even our 9999 lead cost about an extra 1~2k per ton to produce(its what I actually do) we add magnesium and calcium and put it through a KBA(Kroll Bereton Antimonal, or some thingo)process.

Oh and steer clear of melting high content magnesium or product that contains calcium unless you study and use correct safety procedures to handle it.(espes cal it makes a very very nasty gas if exposed to moisture)

Here bookmark this page (http://en.wikipedia.org/wiki/List_of_elements_by_melting_point) handy for a reference

[simso]

Okay, dont want to get anyones nose out of joint but theres only one true way of finding out a materials composition. That is to carry out an electrical burn on the surface and analyize the smoke composition to find out what its made up of. For average joe blow its not worth it as it costs 350 per burn here in australia. The next easiest way to find out what type of broad spectrum the material is made out of is a conductivity test, this will only tell you what the majority of the material is made out of. If its aluminium itll be around 30% + IACS "international annealed copper standard" unless its an aircraft grade aluminium and then it could be anything so it would require an additional hardness test as well, if its zinc itll be 25% Iacs, and magnesium will be around 15%. If your willing to pay postage to perth and back break a small piece of and Ill tell you what base compound it is. This is what I do for a living test and examine metals fitted to aircraft for cracking distortion overheating hardness ect
Steve

[Grahame Collins]

Simso,
You won't get many of this lot spring that amount of money for a good welder let alone an Metals ID test.A spectrograph analyser is a great but pricy bit of kit.

Hear the squeeking sound here doncha? They are as tight as a fishes what not:D .

Here is the electrical test that I did to confirm that the Makita belt sander alloy casing had zinc.I know for sure that it can't be TIG welded. One arc and it flashed off with heap off white smoke. Die cast YUCK!

Grahame

[simso]

Yeh I know, but Im happy to put the offer out there, it takes me less than a minute to do a conductivity test on something and about another minute to do a hardness test. And thats good enough to give them a base material idea.

[Randy Korr]

I'm happy to receive a few to experiment with. I reckon a tonne or two to start with :wink:

But seriously, I thought they were some copper-based alloy or something? I remember putting one in a machine at the Empire State building and it squashed it flat and stamped a tourist message on it.


If you PM a mailing address, I will send a few, but the postage on a tonne would be prohibitive. Zinc's lousy casting metal anyway.

I just found out that it's only since 1982 that they're made out of zinc. I had thought they were plated zinc since about 1959, when they changed the reverse design from wheat to the Lincoln Memorial.

R. K.

[Schtoo]

I think that pennies are the ones that are now worth more as scrap/base metal than they are as currency. Not sure about that, but I suspect it is/was probably true.

Simso, it doesn't really matter what the stuff is for this kinda thing. If I was building a plane, then I wouldn't need to test it since I'd buy the right stuff from the get-go. ;)

I use whatever ally I can get my grubby hands on, and I don't care what it is, so long as it does what I want it to. If it doesn't, then it cost me about $1 in kerosene or waste planer shavings, depends on what I am doing.

It would be nice to know what's what, but it's just not that important. :)

[silentC]

If you PM a mailing address, I will send a few
Haven't you heard about Australia Post! They'd never make it to my door!!

Thanks for the offer though mate. :D

Thanks for the offer also simso. As Schtoo says, it's actually not all that important for my purposes. I've only got three of these pump covers and I'm likely to be collecting all sorts of stuff to throw in the pot.