View Full Version : Zinc
December 15, 2009, 09:57 AM
I have yet to cast any rounds, so for just reading an trying to compile the neccesary items. I keep reading that if Zinc becomes mixed in with the alloy it is bad, bad, bad. Is there any way to remove the Zinc once it becomes part of the mixture?
December 15, 2009, 06:05 PM
If you do a search on zinc in this forum or others you will likely find several ways to remove zinc from a lead alloy. Some are expensive, some are dangerous, most probably don't even work.
If you have just a small batch of contaminated alloy, you might be able to add enough pure lead to dilute the zinc to the point of it no longer causing problems for casting. That should be somewhere around the <5% range by weight.
I recently read about somebody saying zinc can be used in casting, but you need to use a lot of heat and some special handling to get good mold fillout. It was also recommended to NOT use zinc contaminated bullets for hunting since they won't expand hardly at all. Never tried it, never seen it done, just passing along some information I read about it.
December 16, 2009, 01:11 AM
To check for zinc put a drop of muretic acid on an ingot it will give a reaction !!!
To remove zinc it`s been said to flux with sulphur.
I have heated a melt hot 850f then let it cool no stirrin & skim the oatmeal off the top , this is at 600f the zinc floats then freezes .
Just stay on top of your smeltin procces & the zinc will float before it melts , go slow & skim em off!!
Hope this helps even if a little!!
December 16, 2009, 02:41 PM
I thank you for your responses. As soon as I get the hang of melting down w/w and other scrap, I'll try the smelting process that you discribed with the 15lbs or so of ingots that I was told had zinc in it.
December 17, 2009, 08:05 AM
Before trying to remove the zinc try a castin with it , it may cast fine if not then I would go another route!!
If it`ll cast ok I`d go with it !:):cool:
December 17, 2009, 09:20 AM
It was also recommended to NOT use zinc contaminated bullets for hunting since they won't expand hardly at all.
I can believe that.
I know that zinc bullets don't even deform a whole lot when fired into a steel backstop at my indoor range. Had to stop using them.
December 17, 2009, 03:33 PM
Over on the cast boolit forum, there was a guy that was going to try to separate zinc that had been alloyed into lead. The procedure was to heat a pot to just over the point that the lead would melt. Like GP100 says, it's right around 600 deg. The zinc will,(supposedly), separate and float to the top, to be skimmed off.
I don't think you will get all of it that way, but most will be gone. It's important to remember that zinc melts at 787 degrees. As long as your WW smelter is UNDER that temp, you will see the zinc WW floating along with the steel clips. Skim them out, you're in good shape then. That requires a thermometer, but you need one anyway, right?
December 19, 2009, 09:21 PM
Reading in some of my old Lyman reloading books- from the 40s & 50s, in the cast bullet section it states that 1 part zinc to 10,000 lead is no good.
Stay away from wheel weights that are squared on the ends, they are for mag wheels and contain zinc.
December 29, 2009, 09:19 AM
A good pot thermometer is always a plus to keep a check on your alloy temp,Lead melts at 621 degrees Zinc at 787 degrees. As mentioned the Zinc weights will float to the top and you can skim them off. I've missed a few when culling out 5 gal. buckets full of WW,I've never had a problem with the alloy I found floater in. The key is keeping your temp right so they don't melt in.
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