RogueRose
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Aluminum - sourcing purest alloys - Can's are actually a good option!
So I've wondered what is the best source of aluminium, hopefully at a reasonable price. I found this wiki that lists the composition of most Al
alloys and it has some pretty good analysis of the other metals mixed with aluminium.
https://en.wikipedia.org/wiki/Aluminium_alloy
Now the purest form of Al is foil which is alloy 1099 and is 99.9% but I suspect there is a fair amount of Al2O3 on the surface and it would be
interesting to see what % in weight the oxide makes up. It is also pricey. Even buying large rolls at a restaurant supply store, it isn't as cheap
as buying the value brand (often even less expensive than store brand) at the stores. I've seen them for buy on get one free, so that is when I buy
and this usually comes out about 60-70% cheaper than buying a $40-50 roll at a discount restaurant supply store.
Now most cans made in the US and EU have about 97.5% Al, 2-2.25% Mg and .25-.5% Mn. All in all that isn't a bad composition if you want to use this
in something like thermite or other pyro uses and the fact that it is either free or that you would only get $.30-.50 per lb makes it even more
attractive cost wise. There are also some tricks when it comes to melting the cans to make sure you get as little Al2O3 dross on the top.
Melting cans - after every melt, you should save a portion (maybe 1/2 - 1lb depending on the size of the melt) into an ingot that can be used as a
"starter" for the next melt. This ingot, at the next melt, will be heated first until liquid and gotten very hot (1400-1700 is good but well below
steel/iron melting point). Then take the cans and press them into the liquid quickly and they should liquify nearly instantly - you will get flames
as you do this as the ink and plastic printing/coating burns off. Doing one at a time takes about 2 seconds. Keep heat on high while doing this. As
you get more Al built up, you can add more cans at once. It's all a balance of total heat in the mass being great enough to melt the cans immediately
upon submerging them. Every 30-40 cans I wait to get temps up high again then start adding more.
It is best to crush cans, stomping on them is best, but also flattening them - bending bottom & top towards middle of can so both ends face up
and the flat bottom is the side of the can. These seem to melt much better without oxidizing.
One other way to make this much more efficient is by putting the cans in the fire before adding to melt pot. Even if placed on white hot coals, they
don't seem to melt for some time (at least a few minutes) but they heat them to maybe 700-1100F and then they melt instantly when placed in the pot.
Just rotate the the heated cans and replace with new cold ones. All of this can be done over a wood fire and even faster with a blower for air near
the pot (keeping the edge of the fire cooler can help as the cans can be placed there to warm).
I went from getting maybe 25-50% oxide dross to less than 10% when doing melts. My largest of 50+ lbs I had less than 3lbs of dross for the entire
melt and lots of beautiful ingots and some castings.
Now I've heard some members make fun of people for using cans, even mock them, but in some places it's tough to find aluminium of known composition
and cans are usually a given. Unknown alloys can vary WIDELY in their content and can have 13 other metals in them!
So if you have no source for Al of known composition, I see no reason why can't can't be a decent source if you need Al for pyro uses. I'm using a
table saw with a VERY high tooth count blade to cut the Al into tiny chips (a couple mm in width by about .5mm thickness) and these grind MUCH easier
in a ball mill than foil, about 8x faster than foil. I use a vacuum cleaner (bagless vortex type), TOTALLY cleaned before use, to collect chips and
it seems to be ideal for this and have zero contamination. The blades last a LONG time and they are just standard stainless blades, easily
resharpened with a dremel and sanding disc- then the new blade just chews through 1/3"+ thick pourings, all with a 1/4hp motor. I can't wait to hook
up my 2hp motor (legit 2hp continuous duty so serious power) and may add a few blades in parallel to cut wider swaths, though IDK if that is possible
or safe.
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RawWork
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Come on man, why do you need pure Al? I find no use in it. Purifying it will just waste more money or energy.
I would use it as reducent, as powder, for making wires (i would never use copper), and most for battery.
I plan to use Al garbage (mostly cans) as galvanic cell, aka source of electric energy.
Seems useless for large energy wasters like stoves, boilers, motors.
But nice for small energy wasters like smartphones, watches, smaller lights, and if enough quantity even for laptops.
Although it can't work by itself, once we assemble it into galvanic cell after we buy or make acid or alkaline salt, it can give us free energy. Al is
most expensive part of that cell, and luckily it's free from garbage.
I calculated that only half a litre bottle volume is needed to power smartphone for a year if used 24 hours, if HCl is used as electrolyte and Al as
cathode. Also tested electric current, it was over 3 A, although i immersed very small part of Al foil in acid. So I would not recommend wasting
energy trying to clean such Al, except if somebody has good reason to.
I never liked galvanic cells I see on youtube. They show electrolyte being lemon, potato, some fruit, CuSO4... While they can give some current, it's
too weak. Even commercial MnO2 and even Li and Li-ion batteries are weak when compared to Al in acid ones that I discovered. Current generated by
their electrolytes is not even comparable to how much can be generated when acid or alkaline electrolyte is used, especially with Al cathode. I only
immersed a piece of my hand size of Al, if I immersed same surface area as is in Li or Li ion, current would be enough to power all devices.
Yes, I understand that hydrogen is being evolved at anode, but for testing purposes it's fine. It's easy to make at least.
Energy in Al as galvanic cell cathode comes from 3 electrons and it's reduction potential. It is more energetic than Li. While Li has higher reduction
potential, Al has 3 electrons involved while Li only one.
And believe it or not, even if we buy HCl which is actually extremely cheap in my country, 1 L 18% HCl is same price as half a litre of coca-cola, it
is cheaper than buying any batteries including Li, Li-ion, MnO2-Zn, Ag, NiCd....
Much cheaper and easy to make!!! 
[Edited on 30-3-2018 by RawWork]
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RogueRose
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Are we talking about the same thing? I was talking about Al, sources, processing and it's use. The reason I posted is a number of times a few
members were very negative about using cans as a source of Al, some mentioning the large loss due to oxidation and dross - hence my posting about a
good method to melt it.
If you view threads about making Al powder, most seems to suggest using Al foil, which is actually VERY time consuming and relatively expensive
costing $4-8/lb for aluminum. While it is the purest, I was showing that if using this for pyro uses, then the 2-2.25% of Mg really isn't much of an
issue as it will act similarly to Al in powder form and the Mn at .25-.5% is not worth mentioning IMO.
If someone wanted to make an H2 cell that produced gas at a constant rate, then using Al from cans is a decent choice, melt them and pour into
consistent shapes (long solid rods?) so the production would be fairly constant rather than using unmelted cans which causes ALL kinds of problems
(the very thin plastic liner/printing label blocks many acids/bases for hours even if at 120-160F but seems better at higher temps.
I have no idea what you are talking about HCl and "cells" for in relation to this. Can you explain what you mean?
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RawWork
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I mean Al = free energy. When I think of Al cans or Al generally, first thing that comes to my mind is electric energy. 1st priority why I would use
cans. Purity is not important, not even in powder, as it's not needed.
Also melting those cans is not needed if it's being used in small quantity. We can power our smartphone each day by using one square piece of Al
cathode and rest of cell with it, every day each. No need to use all Al at once. Can be cut with scizzors really.
Al is worth collecting or picking up from garbage for whatever reason, but especially for use as a source of (electric) energy.
Throwing away Al cans and not using them is stupid for us chemists at least. And since we already buy and have HCl, it's stupid to buy various
batteries.
We are talking about Al, it's purity, price, uses, and cans as source of it.
If I wanted pure Al I would use one from wires. There is the purest one.
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Pumukli
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Thanks for the article, RogueRose! I'm wondering if I could make a few hundred grams of Al melt, heat it up and dissolve some Ni coins in it in order
to make sort of a Raney Ni. A few percent Zn or Mg wouldn't hurt in that alloy as I read.
Do you think it would be doable in some sort of Youtube-style amateur furnace heated with a propane/air flame?
edited a typo
[Edited on 30-3-2018 by Pumukli]
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Sulaiman
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RawWork
Using cut-up Al cans as a consumable electrode for a primary cell is a great idea !
I may even have a try myself.
------------------------------------------------------------------
I believe that electrical aluminium wire (8000-series) contains iron, manganese, magnesium, chromium and silicon in varying proportins depending upon
grade.
Even aluminium foil is not pure aluminium, to allow processing and increased stength.
[Edited on 30-3-2018 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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MrHomeScientist
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There'd be some prep required, of course, to sand off the plastic liner and/or labeling before you could use it for anything. I'd be interested to see
a schematic of how such a battery would be built, and the calculations behind how much energy it can provide.
More on the original topic, those are great recommendations for melting cans. I was planning on doing a meltdown this weekend, and I was also going to
try NaCl/KCl eutectic as a flux to try cleaning things up. I'll definitely use an ingot as a starter for that melt.
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RogueRose
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Quote: Originally posted by MrHomeScientist  |
There'd be some prep required, of course, to sand off the plastic liner and/or labeling before you could use it for anything. I'd be interested to see
a schematic of how such a battery would be built, and the calculations behind how much energy it can provide.
More on the original topic, those are great recommendations for melting cans. I was planning on doing a meltdown this weekend, and I was also going to
try NaCl/KCl eutectic as a flux to try cleaning things up. I'll definitely use an ingot as a starter for that melt. |
I'm interested in this aluminum battery b/c I have about 55ft x 20 inches of this aluminum flashing (supposed to be pretty pure from what I read.
That would be much easier to use than cans I would think, no removing plastic coating/labels.
Any links to this battery?
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RawWork
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No, because I am the original discoverer, and discovered it only recently. Video is in progress, tough. 
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MrHomeScientist
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False alarm, everybody.
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