My Experience at De-Zincing Lead
I successfully managed to remove excessive amounts of zinc from some contaminated lead.Will I ever do it again? Well maybe if I was down to the last remaining lead I could get, and had no ammo.
I managed to get a couple older publications to leaf thru while considering my technique.
Extractive Metallurgy of Lead and Zinc Cr1970,by Klause E., Gienard H., and Elmar k. ;
Lead and Zinc Sintering Cr2012 Baojun Zhao. I also confided in “real world” lead, zinc and silver smelters- furnace operators. Then checked the safety regulation, and Material safety data sheets, on all processes and chemicals I was working with
I also checked other forums to see what they did that worked and failed. Several attempts looked successful. However not one trial I had found, had bothered to take before and after Spectrometer results.
First things, first. I would not recommend someone who has not had professional experience in smelting, and a proper work area even to try this.
I used the following precautions, ventilation system, and a p100 mask. This process produces very dangerous fumes. The kind you think you walked away from only to drop dead 12 hrs later. Next all body parts covered by 100%cotten, pant legs out over good leather boots, leather apron, heavy welders gloves and a good face shield.(this stuff can and probably will pop and splash at you.)
Here is the process I used.
I do not recommend doing this, and am posting this as a subject for discussion and not a tutorial. I have vast experience in smelting, and working in hazardous situations. Fluxing of molten metal, working with toxic compounds, has been second hand to me. So, I am what you might call a professional, or at least an idiot.
*note: To the best of my knowledge, for this method to be completely successful, at least 1.5% copper must be infused into the lead. My sample was well over that. (Copper and Zinc like each other way more than lead)
Here is what I did. Starting with 5 lb processed, contaminated ingot.
I used “High Yield” Powder sulfur from the garden center
Step1: Bring alloy to 650f and let melt as good as it will. Do Not Stir!
Step 2: Slowly increase temp to 895f. Skim one time to remove initial dross. Do Not Stir !
Step 3: Add a handful of sawdust then slowly cut flame until you reach 644f. Do Not Stir, but fold from top to bottom of pot 3 times then let the alloy sit 10 min. at that temperature.
Step 4: Skim dross off top then add 1 tablespoon of sawdust mixed with 2 tablespoons sulfur. Fold twice. Bring Temp up to 750f . Scrape sides and bottom then fold again a couple times.
Step 4: Turn off the lights and watch the beautiful, bluish; aurora borealis of toxic fumes go up the vent. While dropping the temperature, slowly to 660f. Then after sitting at that for 10 min. skim. Scrape sides and bottom then let sit 10 min. more and final skim.
It should now show a nice, shiny lead puddle.
Step 5 : Reduce with paraffin wax, as you normally would and pour into ingot.
I had 2.1 lb of lead Alloy left out of 5.
Before and after.
PB 56.2%, Zn 31.34%, Cu 3.007%, Fe 3.1%, SB 1.2%, SN 1.18%. SF(other stuff)~4%
PB 98.6%, Zn 0.27%, Cu 0.025%, Fe 0.1%, SB 0.6%, SN 0.02%. SF(other stuff)~1%
Notice, I also removed tin and antimony.
Was it worth it? Was my success a fluke? I don't know. Will I CAST it Yes.
