Wheel weight alloy composition?

[Ogajiga]

When I first started lead casting 10 years ago the Do-it flyer with the molds stated that wheel weights were 90% lead. A posting on a bullet casting website a few years back said clip on wheel weights were 95% lead & flat stick ons 98%. The clip on wheel weight alloy I poured sinkers with today appeared to be way softer than the crumbly grainy finish stick to the pot stuff from 10 years ago. Anyone have info on this?

Edited April 19, 2008 by hawnjigs

[nova]

From what I understand wheel weights are a mixture of lead, tin and antimony.

I use wheel weights mixed with pure lead at about a 50/50 mix. This give me the strength that I want along with an easy to pour product; also, paint will stay on the lead better.

I found that pure lead was too soft and dented quite easily and as you said wheel weights alone give you a "crumbly" result.

www.novalures.com

[sagacious]

At first this seems like a simple question, but definitive ww alloy percentages for the ww's any one given person is melting, is difficult to pin down. It's best to take all numbers as average values. As well, since it's impossible to know what you had 10 years ago, a basis for comparison with the ww alloy you have today will likely be hopelessly imprecise, and most sources of ww alloy percentages give no indication of when the data was made anyway. I have noticed that newer ww's bend and crack, exposing a frosty surface, whereas the older ones would snap, and expose a rougher, more crystalline fracture surface. That may be a clue.

The annoying rub is that ww alloy is changing all the time. Different manufacturers may use slightly different alloys, and those change with the metals market. However, we may be able to shed some light on this. Really old ww's-- say pre 70's-- apparently used 9% antimony as a primary hardening or strengthening component. The average composition reported in the past few years is 4% antimony, 0.5% tin, up to 0.25% arsenic, and the balance being about 95.25% lead. Stick on's are pretty much 99.5% lead.

Now, with the recent meteoric rise in metals prices, it's probably safe to conclude that the more expensive components of the alloy have been reduced wherever possible. That means antimony. The 0.5% tin fraction has likely remained unchanged for decades. That small tin percentage is required for some fairly important chemical and practical reasons, so it's probably not going anywhere. The candidate metals for solid-solution hardening of lead are limited, so significant alloy component substitutions are unlikely to happen any time soon.

The cheapest option is to tweak the chemistry. Arsenic provides considerable strengthening power in small amounts-- more so than a greater amount of antimony. And it's cheap. However, arsenic must be combined with antimony to harden lead properly, but no more than about 0.25% arsenic is needed in ww lead. Older ww's had, reportedly, only about 0.17% arsenic, and more antimony. The newest batches, I suspect, average more like 3% antimony, 1/2% tin, a full 1/4% arsenic, and 96.25% lead. That's enough of a change to notice a difference. Could also be some hardening contributed by very low-percentage metals, but that's not worth too much consideration.

Lead shot uses arsenic as a hardening agent, along with antimony. The more arsenic, the harder the shot, and I think the value ranges to about 1% arsenic. Antimony promotes a more grainy, brittle fracture, but arsenic makes the lead tougher, and the crystals smaller. This makes the shot not only harder, but less likely to shatter during firing, like a percentage of bismuth shot usually does. If the ww lead fracture appears smoother and more 'frosty' and less grainy-- as I saw-- it would match a reduction in antimony and increase in arsenic.

I also recall the lumpy clumps that would stick to the sides of a pot of melted ww's. Just a guess, but I suspect that may have been due to less thorough refining of the scrap lead (battery lead) used to make ww's. Battery lead contains all kinds of things, and it may be that the lead is being refined more thoroughly to retrieve those alloy constituents. So we don't see those wierd crystal 'lumps' floating around in the melt as much, or clinging to the sides of the pot.

Hope this helps, as opposed to being confusing! Good luck!

Edited April 20, 2008 by sagacious

[Ogajiga]

"Sagacious", that helps. Does an increased arsenic component present an added toxicity hazard to the lead caster or consumer?

Since you mentioned zinc as being a "pot sticker" metal in another thread, I remember reading that zinc might have been alloyed into some ww lead, which explains why pouring sessions back when with certain batches of ww coated my pot & ladle with a continuous shiny hard to remove plating. By contrast, the modern ww metal I poured again today left no unusual sticky residue on my equipment. Think you're right about the arsenic harderner because although the melt poured easy like softer lead it set up pretty hard though with a satiny rather than grainy finish.

[sagacious]

"Sagacious", that helps. Does an increased arsenic component present an added toxicity hazard to the lead caster or consumer?

Nope. When working with ww alloy, lead pourers need only observe the standard safety and hygene precautions inherent with handling lead.

Note that metallic arsenic is not the same stuff as 'white arsenic' (As2O3) or arsenic trioxide, the poison. At the small percentages in ww alloy, metallic arsenic will not escape from the melt to pose a hazard.

All the sources I've ever read indicate that these minute levels of metallic arsenic do not pose a threat to the hobby lead pourer. Some more prominent sources (Fryxell, Marshall) discuss the potential toxicity of cadmium contamination in scrap lead (specifically battery lead), but state unambiguously that the arsenic present in antimonial lead alloys presents no danger. So, I'm inclined to believe them, and not be suspicious that they're pooh-poohing a potential risk.

Again, anyone who read this: metallic arsenic in ww lead does not pose a toxic hazard.

Since you mentioned zinc as being a "pot sticker" metal in another thread, I remember reading that zinc might have been alloyed into some ww lead, which explains why pouring sessions back when with certain batches of ww coated my pot & ladle with a continuous shiny hard to remove plating. By contrast, the modern ww metal I poured again today left no unusual sticky residue on my equipment. Think you're right about the arsenic harderner because although the melt poured easy like softer lead it set up pretty hard though with a satiny rather than grainy finish.

Anything is possible under our Sun, but I suspect that any zinc contaminant in your lead would more likely have come from a 'lead-free' zinc wheel weight, or other small zinc die-casting.

Usually what happens if a zinc ww gets into the melt, and actually does melt, the zinc will float around on top like oil on water. And, somewhat like an oil spill, the zinc coats any metal surface it comes in contact with, leaving a hard, shiny coating. Usually that coating can be flaked off, as it hasn't had time to etch the steel pot, which is coated with a protective layer of oxide and grime itself. A hassle none the less, but fortunately fairly rare (to my knowledge).

The way to avoid this hassle is to melt down your ww's at no higher than 650*F (340*C). Wheel weight lead is completely molten at about 505*F (265*C).Zinc melts above 750*F (400*C), so any zinc ww's will float to the top. If you see a suspicious floater, skim it off asap. If your melt is above 750*F and a zinc ww melts, and you see it, carefully skim off the floating puddle of zinc asap and dispose of it. If you raise the temp, the solubility of zinc in lead increases, and the zinc will dissolve. However, when you pour ingots, anything more than 2% zinc will usually separate out as a weird-looking blob on your ingot. Discard that batch of lead. If you have zinc contamination at levels less than 2%, you'll notice right-away, because mold fill-out will be severely reduced. Small pours are almost impossible. Once lead has been contaminated by zinc, the lead is ruined and cannot be recovered for pouring.

Just as an aside, tin and antimony will also attack (dissolve) steel, although at much slower rates than zinc. Takes much longer contact with steel for this to happen, and is only a factor in industrial settings. Very old type metal-- re-used again and again-- will often have a small percentage of iron as a contaminant because of this, but it causes no real hassles.

Good luck, and be safe!

[Ogajiga]

Actually, there seems to be a higher percentage of zinc(alloy?) floaters in current ww batches which skim out with the steel clips. Or maybe I was previously melting the zinc since I poured at a much higher temp with the higher antimony alloy of older wws. Cranked up the heat till even zinc contaminatrf heavier bank sinkers poured OK. Took a lot of scraping, grinding, & sanding to clean up pot & ladle so for a coupla years I avoided wws. Back then soft scrap was abundant and cheap so no need for tire shop visits. "Sagacious", you answered a question in a previous thread I was curious about describing a separate melt floating on top of lead.

Edited April 20, 2008 by hawnjigs

[sagacious]

Sounds like you did get some zinc ones in the melt. What a drag-- I can see why you'd avoid ww's after that experience.

I see a lot more floaters these days, as you describe, but I find them to all be steel here, fortunately. Used to see a few zinc ones occasionally, but I haven't seen a zinc ww for years. Could be different in another part of the country. When in doubt, toss it out. With the metals market as it is, zinc tire weights may be a thing of the past.

Which thread was that with the melt separation?

[Ogajiga]

Oh, wheel weights can be steel? That explains why some floaters are shiny corrosion free riveted weights and some resembling lead are cast on. I think the cast ones are zinc. I remember in my early attempts to melt wheel weights I used to crank up the heat until the floaters which I thought were high antimony melted - no steel ones back then - so I probably got zinc contamination. Searched but couldn't find the thread with the layered melt posting.

[sagacious]

Lots of steel ones these days. The ones I see most are silver powdercoated and stamped with weight/type, such as: 25Fe. Some just have a weight stamped on, and some are unmarked.

If you still find zinc ones in your neck of the woods, keep 'em, they might come in handy some day. If I could get a bucket of zinc tire weights these days, they would get put to good use.