Siddy
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Accidental Cl2 production - Ruined stainless steel
Hi,
Accidentally formed Cl2 gas, whilst moving chemicals through the house (knocking down the old shed).
HCl 30% got all over CaOCl, stank and i had to run out.
Used soap and abrasion to clean everything, but all stainless steel surfaces are dull and "sponge" like. I looked it up and Halogens penetrate
stainless easily and deteriorate the structure causing rust very soon after.
I really need to get as much of the Chlorine out of the stainless, its going to ruin my whole kitchen, any ideas????
Ive tried stainless steel cleaner.
[Edited on 23-12-2007 by Siddy]
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MagicJigPipe
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There is no chlorine in your stainless steel. It already reacted with the Fe and Cr to form Fe(III) chloride and chromium(III) chloride respectively.
I know the Iron(III) hydrolizes to form HCl and because of this Iron(II) chloride was also formed.
In other words, you have nothing health related to worry about (except for maybe the chromium salts) as long as you wash it off real good with water.
As far as cleaning it off without damaging the metal further, I'm not sure. I would just toss it if it was too heavily corroded.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Siddy
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Ive scrubbed it all for hours now. It isnt heavily corroded, its just extremely hard to get off. I used stainless wool and a grit paste cleaner, the
Cl2 left a white "sponge" looking effect. Yes, it would be FeCl3 and CrCl3, i wasnt thinking before, i was panicking thanks for that.
Does that mean that all FeCl3 that comes into contact with water will make HCl solution? I hope so, becuase i ran a sink and filled it with NaOH - i
never realised how exothermic NaOH is when dissolving, i literally burnt my fingers, not that concentrated NaOH is good for skin anyway... The NaOH
should have delt with the FeCl3 i hope, now its the CrCl3 remaining. My scrubbing affords black powder now [the color of Fe(s) and CrCl3] so i think
its working.
I may we well learn for about it, is this correct:
Fe(s) + Cl2(g) > Fe(III)Cl3
Fe(s) + HCl(aq) > Fe(II)Cl2
What if HCl for second equation is in excess, does FeIII form?
[Edited on 24-12-2007 by Siddy]
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12AX7
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Fe(III) is reduced by Fe metal to more Fe(II). Oxygen oxidizes Fe(II) to Fe(III), 1/3 of which precipitates as rust. The remainder is reduced by Fe
metal to more Fe(II). It's a catalytic oxidation that results in more rust.
NaOH won't do anything for you, and certainly not if you dissolve your hands in it.
We're talking stainless here; what you need is a passivating agent. A mixture of hydrofluoric and nitric acids are appropriate, IIRC, but fortunately
for us, a mixture of citric acid and stuff (what I don't recall) works just as well.
If you want the metal to look original, that's a mechanical solution. Got a belt sander?
Tim
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MagicJigPipe
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I'm pretty sure FeIII, if formed, would be immediatley hydrolyzed to HCl under aqueous HCl. If it's similar to AlCl3 then under anhydrous conditions,
FeIII could form. But atmosphere is far from anhydrous. FeII might be soluble in HCl. You could try a dilute HCl wash followed by maybe a mixture
of acids, like nitric and HCl or dare I say, HF or something similar. Maybe even some carboxylic acid?
EDIT
I see someone beat me to the reply.
[Edited on 24-12-2007 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Mr. Wizard
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Try some 400 or 600 sandpaper grit " wet or dry" and sand in the direction you want the grain to run. Try it on a small spot first to see if you like
the results. Keep it wet while sanding.
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12AX7
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| Quote: | Originally posted by MagicJigPipe
I'm pretty sure FeIII, if formed, would be immediatley hydrolyzed to HCl under aqueous HCl. |
Fe(III) is stable in solution, typically as a hydroxy ion. The hexaaquo- ion is very acidic and readily loses a proton or two, giving the hydroxy or
dihydroxy species in solution (I have them as pKa1 = 2.19 and pKa2 = 2.41). A solution of concentrated FeCl3 smells mildly of HCl.
The small amount of FeCl3 formed by oxidation will absorb moisture from the air, nevermind the CrCl3 which (in my experience) never dries out, so
there's no shortage of solvent to catalytically corrode stainless steel in this manner.
Tim
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Siddy
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Thanks a lot for the replies, im going to buy some citiric acid, does anyone know where i can get 100% citiric acid, im going to try a pool supply
shop. Ill also use some 400-800 sand paper.
Some of the Cl2 fog settled in my sink, which is the worst hit area. I scrubbed it and some of the area's look good as new. BUT, when i put water in
it, bubbles appear on the surface of the stainless, they DO NOT rise, they stay on the bottom and only go when the water is drained. Any ideas what
this is? Is it gas formation? it doesnt seem to stop no matter home any times i have rinsed.
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Siddy
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| Quote: | Originally posted by 12AX7
We're talking stainless here; what you need is a passivating agent. A mixture of hydrofluoric and nitric acids are appropriate, IIRC, but fortunately
for us, a mixture of citric acid and stuff (what I don't recall) works just as well.
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Was on my way to buy citric acid, walked past a bottle of citirc hand wash i use in the work room (garage). I doesnt have ingredients, but obviously
there must be a little citriic acid, it also contains pumice, which works as a very good polishing agent on stainless (apparently ). Scrubbed the worst part of the sink with steel wool (was going to try 600grit next),
the white "sponge" effect disappeared, the sink looks really shinny and new.
I ran a sink and only a small amount of bubbles formed on the bottom, and they were small bubbles too - i haven never seen anything like what was
happeing before, water was no able to go on the surface of those places, even when the sink was full (30L?)
Thank you so much 12AX7 (12a RX7?)
btw, i have NaNO3, i could make nitric acid if its worth it?
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Mr. Wizard
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The Citrus or Orange automotive hand cleaner contains d-limonene or orange oil which is a great solvent, but is not citric acid, or even acidic. I
use the hand cleaner for all sorts of things including cleaning metal and you won't go wrong with it. Just remember to rub in the same direction as
the pre-existing brush marks, otherwise it will leave ugly scratches. The pumice is the active agent for what you are doing. The orange oil also
leaves a nice coating on stainless kitchen appliances when rubbed almost clean with a paper towel after a rubbing with pure orange oil. The pure
orange oil is available as Howard furniture oil and is not mixed with silicone oils or other ingredients.
http://en.wikipedia.org/wiki/Limonene
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Siddy
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Oh, well aren't i a retarded one, well it was just the pumice then...
Should i still buy some Citiric acid?
[Edited on 24-12-2007 by Siddy]
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Mr. Wizard
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I think the previous reference to citric acid is from an older method of cleaning copper and brass by mixing lemon juice and salt ( NaCl) together and
rubbing it in. I've seen a lemon cut in half and mixed up with a small hand full of salt to form a mush that would indeed remove corrosion from a
copper or brass plate or casting. I'm not sure exactly why it works, but it does. Some methods use a piece of Aluminum foil to brush the surface as
well. The combination of abrasiveness and galvanic action may be the reason the foil works. Wear gloves and old cloths as the resulting solution seems
to stain hands and clothing. Don't bother buying Citric Acid for this job.
BTW I agree about halogens and acids being bad for corrosion. I had a closed bottle of HCl 'pool acid' in a garage. The seal was intact, but every
shiny bit of metal in the garage started taking on a rusty color in a matter of weeks. Keep that stuff outside. Did you ever wonder why the windows in
a lab are always covered with a white haze?
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12AX7
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Probably the chloride complexes with the copper (weakly, but with granular salt around, the solution is saturated, and abrasive to boot), while the
acid allows some capacity to dissolve oxides. Hmm, citric and ascorbic acids would tend to reduce copper, no? Might also complex, if not oxidized.
But that's not what I meant. I've heard of citric acid used to passivate stainless steel. Probably worth a search on the subject, and I bet there
are some posts on sci.engr.joining.welding.
Tim
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not_important
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Both acids and halides are bad for ferrous alloys, and worth avoiding except for
A) complexing acids such as citric to remove 'rust stains'
B) reforming a passivated layer using an oxidising acid such as nitric
In either case you want to remove all traces of acids when done.
Nitric isn't something you want to slop about, I suggest looking into alternative methods if you really want to pursue that.
The big thing is to get as much of the chloride ions out of there as you can, washing with water and sodium carbonate or bicarbonate then rinsing
well. After that buff the surface to mechanically remove corrosion products and get it smooth again, the wash well once more. You've basically done
this with the hand wash and steel wool.
The hydrocarbons in the hand wash are likely behind the small bubbles, having coated the steel with a hydrophobic layer.
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Siddy
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Thanks for the extra advice, taking it all on board!
Oil looking bubbles appeared on the top of all three of my fish bowls, one of these bowls was up stairs in a room with all windows and doors closed???
Also a oil looking layer was on top of the water. The Bubbles do not pop, but they do not feel like oil on my fingers. They don't form round bubbles,
they form strange shapes.
All the fish are dead, (some are over 5years old) the tanks stink like chlorine, or what i think chlorine smells like (from this little [big]
misshape).
Stainless is still the main objective, i can manage sodium dicarbonate for now, till shops open tomorrow (bloody christmas...)
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MagicJigPipe
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All your fish are dead in a closed room!? This was a HUGE mishap wasn't it? Remember, once Cl2 dissolves in water it creates HCl and HClO both of
which can cause all sorts of reactions with the organics in the water. Either it's a coincidence or the acids reacted with fish poop etc...
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Siddy
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Yes, the room was completely closed. No it was a VERY small mishap, under 1 mole Cl2. The Ammonia would react, but i cant explain the oil looking
bubbles, i could not determine if they were gas or liquid, very weird.
I wish i had litmus paper to test pH, id didnt feel acidic (lol).
Citric Acid worked well, hard to tell on the sink cause ive scrubbed so much and polished with pumice and 600grit paper, but a tea spoon in the sink
was badly effected and i hadn't touched it yet, but it looks fine now after citric acid treatment.
Kitchen smells nice too.
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