UnintentionalChaos
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Removing lead stuck to Stainless Steel
Just throwing a bit of handy advice out there, but if I'm working with lead as electrodes, for example, they usually come out of solution with all
sorts of oxides and junk on them. To clean the lead up, I melt it in a stainless crucible and pour new electrodes, the molten lead pouring out easily
from under the oxide slag. The issue is that while the lead doesn't stick to the crucible, the oxides tend to stick and often attach small chunks of
lead metal to the walls with them. I find these very frustrating to get off since HCl and H2SO4 are useless at removing lead (the HCl actually doing
damage to the stainless by complexing the chromium oxide protective layer). Nitric is a bit too precious for cleaning a crucible and scrubbing proves
useless. I have recently found that even fairly dilute mixtures of hydrogen peroxide and acetic acid readily attack lead metal while doing absolutely
nothing to stainless steel. I used regular 5% vinegar and some 7.5% peroxide, but the mix worked when diluted to half that strength.This is not news
for most of you, I am sure, but it must be useful to someone out there. I also noticed that the sediment produced by dropping some lead into this
mixture is significantly gray in color. Is this some lead dioxide forming, or just unreacted lead dispersed in regular white lead oxide? This sediment
seems to be quite resistant to dissolving in excess vinegar.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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Pyridinium
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Sounds like you're converting the stuck Pb and its oxides to Pb(OAc)2.
Another method that might get the oxides / Pb off is cathodic reduction, to make some hydrogen bubbles to scrub off the oxide coating? Not sure if it
would work, it's just a thought. I'm too lazy at the moment to check the reduction potentials for the relevant species... :-P
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UnintentionalChaos
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Its not so much a coating as a lot of small globs. I broke down and used HCl at one point which probably removed the lead by dissolving the steel out
from under it, but it didn't finish the job. The strange thing is that even tiny quantities of lead cloud the acetic acid solution, quantities that
should have no issue being dissolved to form acetate.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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Eclectic
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Vinegar has some of everything that was in the original apple juice,
distilled white vinegar would have anything volatile produced from the same, so expect some traces of volatile organic and inorganic acids along with
the acetic. You don't get the cloudy precipitate with photo grade glacial acetic acid.
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Mr. Wizard
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This is a problem with gun barrels too. Years ago mercury was often used to dissolve the lead. Now it's not practical for safety and other reasons.
Common vinegar and hydrogen peroxide are now used to accomplish the job. Searching under cleaning gun bores might reveal more details. Many gun
barrel cleaning solutions also include ammonia to dissolve the copper left behind from copper clad bullets.
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Pyridinium
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| Quote: | Originally posted by Eclectic
Vinegar has some of everything that was in the original apple juice,
distilled white vinegar would have anything volatile produced from the same, so expect some traces of volatile organic and inorganic acids along with
the acetic. You don't get the cloudy precipitate with photo grade glacial acetic acid. |
It might be interesting to run some simple tests on a couple batches of dist. white vinegar to see what comes down from Ag+, Ba++, and a couple
others.
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12AX7
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I've never had lead stick to steel, stainless or otherwise. It should chip right off...
Tim
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Pyridinium
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| Quote: | Originally posted by 12AX7
I've never had lead stick to steel, stainless or otherwise. It should chip right off...
Tim |
I actually cast some molten lead tonight, well more properly I de-cast it (melted down some scrap and granulated it by pouring into cold water). I
noticed two things:
1. Some lead and oxides stuck to the inside of the steel crucible (now it's happening to me!!!)
2. The quenching-water from the lead retained a white, cloudy precipitate hanging in it after I poured some off into a jar. I looked closer and
found it to be blue-gray, metallic, iridescent. Really neat looking. It was actually tiny lead particles that were so small they hung in the water.
Now, we all know lead has a high density, but if the particle size and shape is just right you can get almost anything to make a suspension in water.
The molten lead droplets had exploded into mossy lead when they hit the water. Now they are rapidly oxidizing just from sitting in the air.
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unionised
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"Vinegar has some of everything that was in the original apple juice"
Sure about that?
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Eclectic
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Well, since apple vinegar is apple juice fermented with acetobacter, yes!
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