Lead oxidation

[RogerDat]

Two subjects on oxidation.
How to people prevent plain lead ingots from oxidizing in storage? I have some pucks that have been in a crate in the garage for several years and they have either a thicker black oxide coating or white oxide dust coating. Planning to cast this stuff into larger 2.5 lb ingots using the ingot molds from the group buy / vendor Lakehouse.

I does seem to be an issue for plain lead and not much of an issue for lead with tin alloy.

I was smelting some old lead sheathed underground telephone cable. Full of paper wrapped thin wires. I melted it over a fire in the back yard since I was burning some scrap wood. I also figured the wire covering would smoke and might have been plastic so outside activity.

The cable was somewhat heavily tarnished and it seems to me it was really hard to get the lead clean of oxides and flecks of "stuff" Flux with sawdust, stir, skim. Two ingots ladled out and it had to be skimmed again. Stirring brought more stuff up. It was only 20# of lead but I don't recall having this much trouble getting and keeping lead clean. Eventually I had the stuff in nice ingots but wondered if maybe I could have used some other approach that would have worked better.

I did wonder if the burned paper wire wrapping ash got infused in the melt. It seemed to turn to a black ash.

The cable only yielded 22# of lead but it also had 7.5 lbs. of copper wire that should yield about $13 so almost paid for the purchase. :-)

[dbosman]

For fresh or refreshed ingots, paint or powder coat them. Paint one side and dry. Put the ingot paint side down on a bed of nails and paint the remainder.

I've had oakum joints that I couldn't render on my Coleman stove. Even submerged, the lead wouldn't melt out. I have a slag bucket to put over a wood fire, some day.

[BNE]

I like to go hot when smelting. I sort any possible Zinc ones out first, but to get the crud out, heat seems to help the most. I leave the pot covered to reduce the smoke, then influx with sawdust and wax. I light it to reduce the smoke. The fire also burns any oils, tar, oakum stuff also.

As for keeping pure from oxidizing?!? I have not had that issue. Maybe dip in hot wax? Vacuum seal? Nothing easy comes to mind.

BNE.

[Winger Ed.]

You should be casting & shooting it sooner to avoid this problem.

If you can't do that, keeping the air away from the lead is about all else you can do.
Sealed storage, painting, powder coating, something like that.

[NyFirefighter357]

If you really want seal them use Clear Shellac Spray. https://www.homedepot.com/p/Zinsser-12-oz-Clear-Shellac-Spray-408/100176744

[dikman]

For the underground cable I'd be slicing it open to remove the wires etc. If it can't be sliced then cut it into shorter lengths and pull out the innards. Much easier if you only have lead to worry about as you never know what else has been used on the cable (some of the old braided-covered cable was sometimes infused with arsenic to make it unpalatable to bugs).

[RogerDat]

If you really want seal them use Clear Shellac Spray. https://www.homedepot.com/p/Zinsser-12-oz-Clear-Shellac-Spray-408/100176744Hmmm I seem to recall shellac is a wax based finish so that sounds like it would work to seal and yet melt off easily. My junior high shop teacher would be proud I remembered that. As well as remembering you never use a screwdriver as a pry. :-)

For lead I want people to be able to handle I have used that clear art spray that goes over charcoal drawings. I have used that for stuff like sample bullets, linotype or monotype samples I sometimes show people so there is a protective layer over the lead. I'm not sure how well that would do being cooked off when I melt the ingot. Pretty sure shellac would be a better bet.

[NyFirefighter357]

Kerriidae is a family of scale insects, commonly known as lac insects or lac scales. ... These insects secrete a waxy resin that is harvested and converted commercially into lac and shellac, used in various dyes, cosmetics, food glazes, wood finishing varnishes and polishes.

Shellac is a resin secreted by the female lac bug, on trees in the forests of India and Thailand. It is processed and sold as dry flakes (pictured) and dissolved in alcohol to make liquid shellac, which is used as a brush-on colorant, food glaze and wood finish.

Dried shellac is also non-toxic

[RogerDat]

Thanks for the other ideas. I did wonder about heat. I was using an electric hot plate to melt the blocks that I poured when I melted the cable over the fire. I have used that hot plate for melting ingots before but most often for pewter or at least alloys with some tin in them. This was plain soft lead and that has a bit higher melt temperature than a lead/tin alloys. I might have been pushing the limits of what the plate could heat. Seemed to cast and flux a bit better after the pot was down a bit.

Cutting and pulling apart the cable would have been sort of a PITA the wires were really thin and in the cable really tightly. I'm not sure I would have like pulling apart cable treated with arsenic. Melting over a fire outside while staying upwind would seem safer. I cut the cable into short pieces and tossed it into a pot over a good hot fire. Stayed upwind because no point to standing down wind of a fire on a warm day. I sort of wonder how they get all that paper wrapped wire inside the tight lead cable. Never thought about it before but sort of do wonder what that process was.

Still I have had some pretty cruddy lead before and this struck me as especially "productive" of dross. If it was heat I have only myself to blame. I have bars I can put across my propane fryer so that I can put smaller pots on it and have plenty of heat.

[WRideout]

It's just my experience with smelting wheelweight, but I found that rancid vegetable oil really makes the lead let go of any other metal in the mix. And also, it smells like french fries while you are working.
Wayne

[Bookworm]

It's just my experience with smelting wheelweight, but I found that rancid vegetable oil really makes the lead let go of any other metal in the mix. And also, it smells like french fries while you are working.
Wayne

I gotta try this. I've got several gallons of used veggie oil.

So far, I've found used motor oil to be the best at fluxing/reducing wheel weights. The nastiest, greasiest weights in the bucket render out the cleanest.
I've taken to pouring a cup or so of used motor oil in the pot when rendering wheel weights. I'm going to try it with range lead too.

I'll try the veggie oil as a final flux, particularly with range lead. It should help release the lead from the jackets.

[lightman]

I'm wondering if you have a moisture or humidity problem? I store my ingots in my shop, with no heat or A/C and get hardly any oxidation on them. And its fairly humid here. The softer ones do get a little darker as they age. We're talking years here though. I've smelted heavily oxidized lead before. Stuff that was either stored outside or that was from something that was used outside. Cable sheathing, roof jacks, ect. It would be a pain to have to paint or coat all of mine! :(

[kevin c]

...It would be a pain to have to paint or coat all of mine! :(

You aren't kidding: I've got way too many ingots to seal easily, and in any case (maybe I'm being overly cautious here) I'd hesitate to do that to clean casting metal ready for the pot; it might not be much but whatever coating is on the ingots has to burn off and will leave ash in the pot.

I have had occasion to move/restack some antimonial lead ingots that were a year or two old, stored in a conex container out of the rain. Temps inside probably ranged from the high 40's to over 100 degrees, with moderate humidity. There was some white oxidation on the ingots on the outside of the pile, only on the outside surfaces. The surfaces that were inside the closely stacked pile were still clean.

[RogerDat]

I think it may well be condensation that accelerates oxidation in storage. As kevin_c points out where the ingots are exposed they oxidize, where they are interior to the stack they don't.

In my garage the pucks are dumped loose in a wood crate open on top. Combine that with running of a propane fish fryer during the winter which tends to put moisture in the air and cause the air temp to go up and then drop. Good possibility items that hold temperature would be crossing the dew point.

[jaysouth]

Cast all of your lead into bullets and teach them to fly fast. Oxide will not attach to a bullet in flight.

[RogerDat]

Not sure if the bullets are smart enough to learn to fly. Maybe I could trick them into jumping off the roof?

There could be another factor. I park my rather large 10 hp self propelled snow blower in front of that spot. While I do brush of the worst of the snow when I park it there after using I'm sure it puts a lot of moisture in the area.

What got me thinking on the snow blower as a possible cause is i have a good amount of plain lead at a different location in the garage. Including 90# of soft lead in 5# bars stacked on the floor. Not oxidized and they have been there for a couple of years. Near them there are some 1/2 inch slabs of xray room liner also on the floor with no oxidation to speak of. Those have been there for several years.

Also the pucks in that crate are mini muffin sized so a lot of surface area per pound and those are the most oxidized. The slabs on a furniture dolly next to it are oxidized but not as bad. They have less surface area and less area exposed.

All of this lead is going to end up as 2.5 lb. bar ingots. Either mixed into an alloy or as soft lead. New ingot molds are motivating me. Thinking about it there wouldn't be much work or expense to give each layer of ingots a light coating with spray shellac. Or I could even put a lot of them in Small Flat Rate Boxes. I accumulate lead faster than I use it so to some extent this lead is my retirement stash and some will probably end up sold in my estate with any luck. After all dying with some lead and components left means I never ran out.

[Bookworm]

... I accumulate lead faster than I use it so to some extent this lead is my retirement stash and some will probably end up sold in my estate with any luck. After all dying with some lead and components left means I never ran out.

This is best-case.

I was at an estate auction a few years ago, chatting with some other potential buyers. There were probably 300 people there, milling around this fellows property.
I said ' This is my yard many years from now. I have no kids, so everything will be sold. Buncha folks I don't know, standing around raising their hands....'

[lightman]

Roger, I think you may be on to something with the snow blower. Who would have thought about that?

[RogerDat]

Roger, I think you may be on to something with the snow blower. Who would have thought about that? Someone who spends way too much time in contemplation while sitting in the garage. I was putting a commercial lead puck into that crate and it was a struggle to roll the crate out from under the shelf because the snow blower was right in front of the shelf and in the way. As they say "light bulb" moment.

I have a couple items that I plan to get rid of, then I can move that snow blower over further. Was going to do yard sale but didn't get to it. Now a big item or two will end up on craigs list.