devinw
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Storing Manganese chips caused..rust?
Hi all! I had a bag of what was supposed to just be Manganese chunks that I had used to make some Magnesium Chloride (worked out, made pretty pink
crystals) in a not-very-sealed zip-lok bag. I put the bag in a cabinet in my shop which has a bunch of spray paint cans in it and forgot about them
and came out to grab some paint and all of the cans in that particular cabinet are insanely rusted on the seams. It's like they were in a garage by a
coastal city for 20 years but this happened in 6 months or so.. And the door hinge right near the Mn bag is all corroded and has like black little
globs on it. Is this something exposed Mn does?
I'm a chemistry newbie, so go easy on me. I just found this phenomenon interesting and need to find a way to seal off these chips so they aren't
exposed. Thanks for any help!
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gdflp
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Thread Moved
2-8-2017 at 14:23 |
gdflp
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Manganese metal is not at fault for what you describe.
A volatile acid, such as HCl, however will do exactly that to exposed metal. Did you have any HCl stored in that cabinet, or any chloride salts which
could have hydrolyzed over time to release hydrogen chloride vapors?
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AJKOER
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Well, it could be given steel cans and Mn plus moisture and any salt treatment dust for ice melting, and you may have some of the ingredients of a
galvanic corrosion reaction. Also, include the air surrounding the metals, which could be a source of O2 (for a metal/air battery) or CO2 or other
acidic/basic fumes.
My point is that the presence of a strong acid (or base) is not required if one considers electrochemical avenues.
[Edited on 3-8-2017 by AJKOER]
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unionised
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OK, lets start by checkinh on something
"Manganese chunks that I had used to make some Magnesium Chloride "
Do you mean manganese chloride?
Did yo make it by reacting the metal with hydrochloric acid?
Did you neutralise any leftover acid before storing the chunks?
If not it's likely that HCl is the cause of the rusting.
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devinw
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Yes I was making Manganese Chloride with HCL. Sorry about that typo! My mind always wants to type Magnesium when I think Manganese!
I thought I used up the HCL though. Let me check the cabinet tonight. If I did still have some HCL, it would be in a sealed jug though. Could it still
cause this problem in a plastic jug from the manufacturer?
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gdflp
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There's no way galvanic corrosion could explain this; how would the hinge have made an electrical connection to a piece of manganese sitting in a
bottle on the shelf? There aren't sufficient amounts of electrolyte present for an electrochemical route to have proceeded with any rapidity. It's
incredibly unlikely, especially when a corrosive vapor was likely present.
As to HCl vapors leaking from the original bottle, that's a very common occurance. In fact, I would expect it unless the original bottle had a
Teflon-lined cap.
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lab-equip
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Everything is said, your hydrochlorid acid out of the bottle or out of the MgCl2 hurts your cans..
Store acids and bases somewhere always fresh air is circulating around.
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AJKOER
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No corrosion chemistry going on?
Please contact the pundits that stated in a study, to quote:
"According to the current U.S. corrosion study, the direct cost of metallic corrosion is $276 billion on an annual basis. This represents 3.1% of the
U.S. Gross Domestic Product (GDP) (Figure 1)."
Link: https://www.google.com/url?sa=t&source=web&rct=j&...
I once mentioned in a thread about the new US naval vessels (a multi-billion dollar contract) that apparently have a steel jet propulsion system
connected to the aluminum hull. In polluted waters the ship where dissolving so fast that they were decommissioned. See headline "Builder Blames Navy
as Brand-New Warship Disintegrates | WIRED", link: https://www.google.com/url?sa=t&source=web&rct=j&...
-----------------------------------------------
My prior comments and link on the dissolving ships:
Quote: Originally posted by AJKOER  | Maintaining the luster on alloys may be a matter of the local environment. Add sea salt spray (a good electrolyte) and your inert alloy may become
electrochemically altered. Research metal-air batteries, metal-sulfur batteries, even a galvanic cell from an alloy (see, for example, https://www.google.com/patents/US4264362 ).
One would hope that the science of keeping your weapon sharp (at its peak) has long been solved. However, the report of dissolving new fast Aluminum
warships (see https://www.wired.com/2011/06/shipbuilder-blames-navy-as-bra... ) suffering aggressive corrosion at the interface of iron water jets with the
aluminum hull in sea water (and even worst in polluted/acidic waters) suggests otherwise.
I recently observed during my travels in Florida, a hot humid southern state, that the local copper pennies seemed to be unusually corroded. While my
observations are not based on a thoroughly designed scientific study, the local conditions, which apparently include heat, sunlight, high humidity, a
long coast line and sulfur rich fresh water, do suggest a potentially active environment for galvanic corrosion.
[Edited on 20-12-2016 by AJKOER] |
Link to thread: https://www.sciencemadness.org/whisper/viewthread.php?tid=63...
[Edited on 4-8-2017 by AJKOER]
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Texium
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Missing the point as usual AJKOER. Nobody said that no corrosion chemistry is happening. You'd be a fool to deny that. They only said that no galvanic
corrosion is happening, and that's obvious. A ship sitting in saltwater is a completely different situation than two pieces of metal sitting apart
from each other in a cabinet. Electrons are not going to spontaneously jump through the air.
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AJKOER
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Perhaps I forgot to mention the point that just about all metals employed in applications, like a simple metal hinge, are, in fact, a metal alloy or
metal plated! In addition, some select pure metals are capable of forming a battery cell with a metal/air or O2 or even sulfur.
The reason that a large number of circulating US pennies (copper plated zinc plus added scratches), for example as I cited above in the case of
Florida, in my opinion, are not a corroded mess, is that the other necessary conditions for a galvanic corrosion reaction are likely absent.
The presence of high humdity, O2, CO2 and other acid gases, sulfur rich air particles (which, depending on location, can also be apparently rich in
transition metals, see, for example, http://www.sciencedirect.com/science/article/pii/S1352231016...), elevated temperature, ionic salts, ....., can start the process.
If the problem caused by corrosion reactions were not pervasive, it would not be claimed to amount to over 3% of the U.S. Gross Domestic Product.
[Edited on 5-8-2017 by AJKOER]
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Texium
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Still missing the point. I'm amazed at how much you are able to talk while saying absolutely nothing.
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AJKOER
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I believe the issue is with terminology. Yes, galvanic (meaning two metal) cell may or may not be present along with a metal/air battery cell (that
is, a metal/non-metal cell commonly referred to most accurately as an electrochemical cell and not technically a galvanic cell). Both, however, are
examples of the chemistry of corrosion, a term I used.
If your opinion is that corrosion of metal spray paint cans, for example, is always caused by escaping acid fumes, you are mistaken as I have witness
this also and no stored acids were present. The escaping of compressed gas does, however, cool the can and results in condensation. Weak air based
acidic gases (like CO2) do not by themselves directly attack steel, but can still cause rust in an electrochemical reaction involving also oxygen and
an electrolyte from dust/water condensation, which is my opinion as to what could, in part, be occurring more generally.
[Edited on 5-8-2017 by AJKOER]
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Texium
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I'm not saying that in general acid fumes have to be present for corrosion to occur. In this case though, the OP had in fact been using HCl, already
pointing in that direction, and the rate at which the corrosion happened points to HCl being the most likely culprit as well. Your claim of a galvanic
cell between the chips of manganese which are inside of a bag and the hinges and spray paint cans is utter crap. I'm just calling it what it is for
the sake of the poor OP so he doesn't become even more confused by your ramblings.
Your "theories," AJKOER, read like someone seeing a body with a fatal stab wound and saying "well it must have been a unicorn attack"
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AJKOER
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Per my previous discussion, in my opinion, Mn and O2 is a metal/air battery (see, for example, https://www.google.com/url?sa=t&source=web&rct=j&...) awaiting an electrolyte. In the possible presence of HCl, some MnCl2 serving as
an electrolyte, which would be not be consumed. The main reagent is still not the small amount of captured HCl fumes, but O2 acting on Mn in an
'electrochemical cell' and not a galvanic cell. Note, the report of 'black little globs', implying MnO2 or related MnxOy.
In the case of the steel cans, Fe/O2 and thanks to moisture and possible HCl, FeCl2 formation acting as the unconsumed electrolyte in yet another
electrochemical cell. Note, reports of a rust corrosion product and not FeCl2.
The MnO2 globs on the hinge implies the hinges' metal (or metal alloy) could be in touch with the Mn bag as part of a galvanic cell, but yes, I agree,
questionably.
In my opinion, this is the strongest argument presented so far as it suggests that the results of a direct chemical attack provided the necessay
electrolyte serving as the basis for an ongoing electrochemical attack resulting in significant corrosion and reported products thereof.
[Edited on 5-8-2017 by AJKOER]
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elementcollector1
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AJKOER, you would benefit from a healthy dose of Occam's Razor. The manganese chunks had been placed in HCl. Said chunks were then taken out, placed
in a plastic bag, and placed next to the spray paint cans. HCl can diffuse through plastic bags. Only a very small amount of moist HCl gas is needed
to corrode a fairly large surface area of metal. Finally, iron oxide can be black in coloration (see rust removal via phosphoric acid for a
demonstration of this).
Until you can securely disprove that the HCl caused the corrosion, a galvanic cell of any type is unnecessary because it is not the simplest
explanation that fits the data.
EDIT: And before I forget, Mn is more electropositive than Fe and steel alloys, so it would corrode preferentially if in electrical contact.
[Edited on 8/5/2017 by elementcollector1]
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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AJKOER
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Actually, cleaning a metal surface with HCl is not uncommon when employing the metal in an electrochemical reaction (read some of my references I
provided at the bottom of page 63 in the "Make Potassium" thread) as it cleans the surface of oxide coatings.
Now, Elementcollector1 claims corrosion by HCl. And, what could be the possible products of such a reaction? Answer: MnCl2 and H2. Unfortunately, not
introducing a half cell reaction involving O2 precludes the formation of MnO2.
I also embrace the possible presence of HCl producing MnCl2 (or FeCl2) as providing a path for an excellent electrolyte.
[Edited on 5-8-2017 by AJKOER]
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Texium
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And yet, you're still so off base because the object that is being corroded here is the hinges and spray paint cans, which are made of steel/iron,
which is commonly known to by attacked by moist HCl vapors in air to produce a dark brown rust of basic iron chloride/oxide crud. I'm completely
mystified why you're still going on about manganese corrosion, and why you'd have any reason to be that manganese dioxide would have accumulated on
the hinges...
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AJKOER
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| Quote: Originally posted by zts16 | | And yet, you're still so off base because the object that is being corroded here is the hinges and spray paint cans, which are made of steel/iron,
which is commonly known to by attacked by moist HCl vapors in air to produce a dark brown rust of basic iron chloride/oxide crud. I'm completely
mystified why you're still going on about manganese corrosion, and why you'd have any reason to be that manganese dioxide would have accumulated on
the hinges... |
Yes, a " dark brown rust of basic iron chloride/oxide crud" likely produced as follows:
Fe + 2 HCl → FeCl2 + H2
which is a standard chemical reaction followed by the net cell electrochemical reaction:
4 Fe(ll) (aq) + 2 H+ + O2 → 4 Fe(lll) + 2 OH- (see, for example, http://corrosion-doctors.org/Experiments/rust-chemistry.htm and "IMPACT AND MANAGEMENT OF IRON CORROSION BY-PRODUCTS ON DRINKING WATER QUALITY
IN DISTRIBUTION SYSTEMS" by Md. Safiur Rahman, 2014, page 76, net of reactions 4.1 to 4.4.)
See also my comments and sources presented at https://www.sciencemadness.org/whisper/viewthread.php?tid=73... .
If one accepts this mixed chemistry, why does it not apply to Mn, which is also a transition metal like Fe described by Wikipedia (link: https://en.m.wikipedia.org/wiki/Manganese ) as "Manganese tarnishes slowly in air and oxidizes ("rusts") like iron in water containing dissolved
oxygen." ?
[Edited on 5-8-2017 by AJKOER]
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elementcollector1
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Firstly, there's no evidence MnO2 is anywhere beyond a few dark black dots on the paint cans in question, which could be anything from black iron
oxide to misplaced flecks of spray paint. Prove to me that that stuff is definitively MnO2, and I might start believing the need for electrochemistry.
Also, if the Mn in question was just in HCl, and contained enough HCl fumes to rust the paint, the atmosphere around it would be thoroughly reducing
in nature, which would suggest against the formation of Mn oxides. Note that the OP did not say that the manganese itself looked oxidized in any
capacity. And before you note that the steel rusted in the same reducing atmosphere, I might remind you that localized concentration of HCl would
suggest that the area near the Mn is more concentrated than the area farther away from it.
Again, there is simply no evidence suggesting electrochemical corrosion of any nature. Why you are so desperate to prove that this reaction takes at
least two steps, one of which involves a galvanic contact made through a plastic bag, is quite beyond me.
EDIT: I will also note, now that I remember it, that MnO2 has a remarkable ability to store (and form) chlorine gas when exposed to HCl. I had once
finished making several grams of MnCl2 (and copious amounts of chlorine) from a stock of purified MnO2, and had washed and dried the MnO2 before
putting it back in the bottle. When I opened the bottle later that night, I was shocked to find that the MnO2 positively stunk of chlorine, enough so
to make me cough despite my nose being a good distance away from the bottle.
This anecdote leads me to suggest a possible alternative: The Mn, when placed back in the bag, was still contaminated by traces of HCl. The air in the
bag oxidized the freshly exposed metal surface of the Mn, producing MnO2, which in turn reacted with the HCl to give Cl2 and MnCl2. The Cl2/HCl
diffused through the plastic bag, whereupon it reached the metal of the spray paint cans and began corroding them. Chlorine, being significantly more
reactive than HCl when mixed with water vapor, could also explain the surprising amounts of rust given the small volume of contaminants.
Proof of this reaction pathway would be demonstrated if the plastic bag, upon opening, smelled of chlorine instead of HCl (if the OP knows how to
distinguish between the two). It's certainly not as likely as simple HCl diffusion, but it's a damn sight easier to prove than galvanic corrosion
through a capacitive plastic medium.
[Edited on 8/6/2017 by elementcollector1]
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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AJKOER
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| Quote: Originally posted by AJKOER | Per my previous discussion, in my opinion, Mn and O2 is a metal/air battery (see, for example, https://www.google.com/url?sa=t&source=web&rct=j&...) awaiting an electrolyte. In the possible presence of HCl, some MnCl2 serving as
an electrolyte, which would be not be consumed. The main reagent is still not the small amount of captured HCl fumes, but O2 acting on Mn in an
'electrochemical cell' and not a galvanic cell. Note, the report of 'black little globs', implying MnO2 or related MnxOy.
In the case of the steel cans, Fe/O2 and thanks to moisture and possible HCl, FeCl2 formation acting as the unconsumed electrolyte in yet another
electrochemical cell. Note, reports of a rust corrosion product and not FeCl2.
The MnO2 globs on the hinge implies the hinges' metal (or metal alloy) could be in touch with the Mn bag as part of a galvanic cell, but yes, I agree,
questionably.
In my opinion, this is the strongest argument presented so far as it suggests that the results of a direct chemical attack provided the necessay
electrolyte serving as the basis for an ongoing electrochemical attack resulting in significant corrosion and reported products thereof.
[Edited on 5-8-2017 by AJKOER] |
Per my discussion repeated above, citing that my contention of an electrochemical feature to the observed corrosion is reliant on a 'galvanic cell'
solely is simply not valid.
Also, Elementcollector1 comment, to quote:
"The air in the bag oxidized the freshly exposed metal surface of the Mn, producing MnO2"
assuming that the Mn behaves (meaning the process of 'rust' production) as Fe, per the Wikipedia comment noted previously (namely, "Manganese
tarnishes slowly in air and oxidizes ("rusts") like iron in water containing dissolved oxygen."), implies a possible Mn/O2 electrochemical cell in the
presence of moist MnCl2.
Note, a metal/air battery, as this source notes http://scitoys.com/scitoys/scitoys/echem/batteries/batteries... , can likewise, in place of oxygen, proceed with either H2O2 or bleach (or HOCl,
see also my prior comments on SM on a so called bleach battery at https://www.sciencemadness.org/whisper/viewthread.php?tid=30... ). I mention this as further citing the presence of Cl2 (from the action of MnO2
on HCl), in the presence of H2O yields HCl and HOCl, with the latter hypochlorous acid being completely capable of feeding an electrochemical cell as
well.
Interestingly, even with limited water presence operating at RT, one may still be able to create an inefficient form of a metal/Cl2 battery. This
could form, in the current case of the metal Mn and Cl2 gas, the MnCl2 salt. See, for example, https://link.springer.com/article/10.1007/BF00610944 .
Bottom line, no escaping the likely contributing presence of an electrochemically fueled corrosion reaction, in my opinion, whether via O2, HOCl or
Cl2, or in combination thereof.
[Edited on 9-8-2017 by AJKOER]
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