Tin removal

[fiatdad]

Does anyone know if tin can be removed from an alloy by the different solubility of tin based on temperature?
Nick

[robert12345]

Nope, I do not know.
.
But,,,,
I read some where, ....some place, that once a metal has been alloyed, it is alloyed forever, and they way it is made pure again, is to dilute the alloy with pure metal, until, the metal which was added is of no consequence.
.
Truth;there is a way but it has to do with a seed of the metal you want to remove, inserted into liquid metal, then to attract the alloyed metal to the seed, but the process is above our pay grade.

[RogerDat]

Interesting question. Never heard of folks wanting to take tin out of their casting alloy. Why would you wish to do so?
Typically if the tin content is too high then one "cuts" the tin alloy with more plain or WW lead to reach a lower percentage of tin. If one wants a higher percentage of tin one buys a tin alloy with higher percentage of tin. Pewter being near the top of the tin percentage alloys we commonly see.

I seem to recall that precious metal reclamation is done in stages, often using chemical bath and electrodes. Typical would be pulling the alloys out of gold. Getting the gold, silver, copper, nickle, and maybe palladum out of the dissolved solution so they could be sold as closer to pure metals. Of course the metal reclamation only buys the customers gold items based on the gold content percentage so the other metals and getting the gold closer to pure work together to make the involved process of separation profitable and offset what I imagine ins a fairly expensive process.

[Tatume]

An alloy is a solution, like salt dissolved in water. With the equipment available to bullet casters it cannot be removed.

[bangerjim]

Heat the melt up WAAAAY hotter than normal ( I mean HOT) and start skimming the Sn off the top. Won't get it all, but most of it will oxidize and be on the top. Stir it A LOT with a metal spoon NOT a wooden stick. That carbon in the wood will just flux the Sn back in. May take a while and a big waste of energy! But that will remove most (not all) of the Sn.

Or just trade what you have for some pure Pb, which is what we are assuming you are going for to cast up BP RB's?

banger

[lightman]

Melting it at a higher than normal temperature will cook some of it out. Not all, but some of it. But, tin is considered to be very valuable to us casters and I suggest diluting it with a lesser tin rich alloy to save it. Just curious, what alloy are you working with and why do you want to do this?

[fiatdad]

Just an experimental inquiry, but can you get antimony out of a lead alloy? I accidentally put some scrap into my pure lead and it got hard.

[BattleRife]

You haven't said an alloy of what, but assuming it's just lead with a bit of tin, the answer is probably not:



For up to about 7% tin you get an essentially homogenous solid called alpha phase at all temperatures from solidus down to below 100°C. Not much to work with.

If you tin is high, say up around 15%, there is a narrow window where you get a mushy phase of alpha + liquid, the alpha is going to be somewhat tin deficient while the liquid will be slightly tin-rich. You could theoretically separate them to lower the tin content a point or two. Certainly it is very unlikely you can make enough difference to justify the effort.

[BattleRife]

Just an experimental inquiry, but can you get antimony out of a lead alloy? I accidentally put some scrap into my pure lead and it got hard.

It certainly can be done and is done on an industrial scale, but for a hobby level guy it would not be practically possible. Alloys are usually separated via complex sequences of reactions. For example, you might find with lots of research that a pot of your alloy exposed to chlorine gas for hours at 450°C at 1500 kPa pressure will eventually result in all the antimony reacting to form antimony trichloride and some of the lead reacting to form lead (II) chloride. The liquid you have left behind will be pure lead. Maybe some more research shows that antimony trichloride will dissolve in a hydrochloric acid solution with a pH of 2, whereas lead (II) chloride will not, so dump all those solids in HCl, filter out what doesn't dissolve and the two chloride salts are now separated. Treating the liquid with a caustic to a pH of 11 could then precipitate the antimony trichloride as a solid again. These salts could then be smelted (real smelting, not the simple remelting of scrap that people around here call smelting), and voila, you have pure metals again.

The above is just a bit of fantasy chemistry designed to illustrate a typical extraction cycle, I didn't look up the actual potential reactions. The point is it involves a complicated flowchart of processes, with industrial level process control at each step. It is not something that can be done without a good understanding of the chemistry and a carefully built process circuit.

[Rcmaveric]

What ever is involved is beyond my High School chemistry lesson with cabbage juice as a PH tester.

[bangerjim]

These salts could then be smelted (real smelting, not the simple remelting of scrap that people around here call smelting), and voila, you have pure metals again.


It is not something that can be done without a good understanding of the chemistry and a carefully built process circuit.

Finally - - - - - somebody that realizes the simple re-melting of hunks of old tire weights, pewter, and scrap Pb is NOT real "smelting" of metals!

banger

[RogerDat]

Finally - - - - - somebody that realizes the simple re-melting of hunks of old tire weights, pewter, and scrap Pb is NOT real "smelting" of metals!

banger

Nah we all know our scrap melts are not really smelting but it sounds way cool to call it that so.....

In answer to fiatdad having contaminated his soft Pb with harder alloy it sounds like a swap is in order. His hard for someone else's plain. Or just buy a box of plain soft lead in S&S forum and use the harder stuff he has for casting bullets that require a harder lead. Sort of depends on if fiatdad has use for harder and what value the scrap alloy that was accidentally added has. Dump a bunch of scrap Babbitt in and it would make a high value trade item. Zinc scrap and it won't have value, COWW's at 50/50 plain or better should swap easily.