smeesh
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Hydrogen Embrittlement
until recently, i had no idea that exposure to hydrogen could damage the structural integrity of steel and some other metals.
i was most displeased with this development, as i plan to store hydrogen in a pressure vessel that is made of relatively low quality steel.
does anyone know anything about hydrogen embrittlement, beyond what is available on the first pages of google? if so, please answer the following
questions to the best of your ability...
could i reduce likelihood of structural damage by painting the inside of the container?
would i experience similar challenges with an aluminum container?
thanks guys
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SM2
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Well, technically, isn't H2 a metal? It doesn't seem to react with water at regular ATM at least, so there are no alkali metal properties to it
(corrosion). There are way smarter brains in here to possibly lend insight. I just wanted to take a stab.
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DJF90
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If you're referring to the placement of Hydrogen in the periodic table, it is often plonked above the alkali metals but does not really conform to
their shared chemistry. I do however recall that solid hydrogen has a "metallic state". As for the embrittlement problem, as far as I'm aware its a
common problem with steels, but I don't think aluminium is affected. The downside with aluminium is that its tensile strength may not be high enough.
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SM2
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IRONic H2 & Fe being some of the two most common elements in known universe (I think). Perhaps since H2 is so small, it can pass into steel and
wreak it's insidious havok, much in the same way that some non-polars can be kept in poly-ethylene btls., but after a period of time, they are
weakened.
But if the H2 doesn't leak out of the steel, it would still slip into initial layers, and the pressure would force those hydrogen atoms against the
steel, affecting it's strength, ultimately.
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vmelkon
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What are the conditions necessary for an element to be considered a metal?
That's like saying that lithium doesn't react with lithium oxide. Hydrogen is not an alkali metal.
Hydrogen is in its own group. It forms hydrides with many metals.
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ldanielrosa
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Yes, hydrogen embrittlement is is a source of frustration to welders. I remember an anecdote about how one welding crew was given color coded
low-hydrogen electrodes, and the color was changed every hour due to the high humidity.
As I recall, as iron cools below 300C or so the crystal structure transitions to one with much lower solvency for hydrogen. However, if you are
storing hydrogen under pressure then this may not be of much value to you.
How much hydrogen do you plan to store, for how long, at what pressure?
You should be able to find data on what alloys are used for hydrogen bottles.
"What are the conditions necessary for an element to be considered a metal?"
@vmelkon , it may seem unimaginative and imprecise but all of my instructors that addressed the question said "Metals are shiny and electrically
conductive."
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Endimion17
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smeesh, you're asking a question many scientists and engineers are working on. 
Hydrogen is a pain in the ass when it comes to storage. Not only it makes the metals brittle, but it also seeps out of containers, which will be a
major problem if the hydrogen economy comes forward too early, because hydrogen destroys the ozone layer.
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Arthur Dent
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Hydrogen "corrosion" is the enemy of gas refineries, I remember a few years back a gigantic fire at an east-end refinery in Montreal not far from me
and the cause was traced back to a pipe that carried hydrogen gas and suddenly failed because of corrosion. I remember hearing the loud "broooooom"
and going out to see what I could only describe as a mushroom cloud worthy of an end-of-the-world attack. Never seen so many fire trucks converging to
a single fire so fast!
Robert
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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watson.fawkes
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Oh, don't do
that; it's a recipe for disaster.
Tank hydrogen is available from your standard weld gas suppliers, though it's not universally stocked. I believe they use standard steel pressure
tanks, though I'd verify that first. I wouldn't be surprised if they have somewhat shorter lifetime storing hydrogen, but in the USA there's a
requirement that the tanks be hydrostatically tested every 10 years. Assuming no special tanks (which is as I recall), that would mean that the rate
of embrittlement at ordinary temperatures is pretty low.
Hydrogen is a "permanent gas", an old term of art meaning it doesn't liquify under pressure, at least at pressures readily available, and excluding
cryogenic temperatures. Practically, permanent gases need a high pressure compressor to store any reasonably large quantity of gas, and those aren't
cheap.
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watson.fawkes
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The condition is delocalization
of the electron cloud. There's a transition where the expected value of the distance an electron delocalizes from an atom or molecule becomes
infinite; that's the metallic state. This is related to the random walk, which is infinite in three dimensions, but finite in one or two.
The condition isn't just for elements, by the way; it's possible for compounds and mixtures to be metals. One interesting example is so-called
"lithium bronze", which is Li dissolved in ammonia. That solution itself becomes metallic, as some of the electrons from the ammonia become
delocalized. It's fascinating stuff, as you can vary the temperature and measure the transition to the metallic state.
The "shiny" part of the metallic state is generic to delocalized electrons, as they are motile and react to incoming light, which means they start
oscillating and re-emit quickly.
Metallic H2 is still a research subject. See the Wikipedia page.
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Pyro
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if you need hydrogen you should make it as you need it.
take an old fire extinguisher and do wat they do in draino bombs, NaOH and Al. but since a fire extinguisher is pressure resistant it wont explode,
but will just collect it and vent if the pressure gets too high. you should keep it in water while it is reacting though, otherwise it might get too
hot.
all above information is intellectual property of Pyro.  |
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SM2
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Quote: Originally posted by Endimion17  | smeesh, you're asking a question many scientists and engineers are working on.
Hydrogen is a pain in the ass when it comes to storage. Not only it makes the metals brittle, but it also seeps out of containers, which will be a
major problem if the hydrogen economy comes forward too early, because hydrogen destroys the ozone layer. |
If your going to spend that much money on a fuel cell vehicle, I bet it's been engineered with water as it's main fuel precursor, and a hydrogen
generator to supply H2 as needed. Batteries would be needed any way, but in this case, one would need extra potential to run the H2 generator, since
it's not 100% efficient. Or at least, solar cell subsidy. The H2, gen. uses a sort of Pd GoreTex, and the fuel cells I worked to develop, were
composed of carbon-carbon paper matrix, including Pd, and some other things. Acted as direct fuel cell and promoter.
I guess it would be way more efficient to make H2 en mass. So many advantages, economies of scale, no H2 gen break downs....list goes on and on. The
latest fuel cell tech blows away anything I was working on, with huge density potential. I mean a few stamp sized fuel cells were enough to produce
enough electricity to run a car.
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zed
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Tell us more about your storage vessel (especially its diameter), where this Hydrogen is going to come from, and how high the pressures will be.
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Poppy
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Is it a problem of steel only? AFAIK solid metals are composed of crystals and there are gaps between these crystal. With the gas speed of hydrogen
gas the H2 molecule may enter one of these gaps, then vibrate and keep digging, enlarging it.
Thus this should pose a problem to every solid metal, not just steel, unless some kind of catalysis acts on the H2 molecule maybe forcing it to gain
extradiordnary speeds or dissolving along the path of the Hydrogen.
The catalyst for making ammonia through Haber process is sometimes said to be iron, so iron may get a special effect upon hydrogen.
:S
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AJKOER
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An observation, per Wiki: "Hydrogen is a concern in metallurgy as it can embrittle many metals,[11] complicating the design of pipelines and storage
tanks.[12]" Link: http://en.wikipedia.org/wiki/Hydrogen
So my suggestion is not to fight the problem between H2 and metals, but let them join forces! In other words, look at chemical storage routes. Per
Wiki ( link: http://en.wikipedia.org/wiki/Hydride ): "Various metal hydrides have been examined for use as a means of hydrogen storage for fuel cell-powered
electric cars and other purposed aspects of a hydrogen economy.[5]"
In the case of H2 and Lithium. Reaction:
2 Li + H2 → 2 LiH
Addition of 0.001–0.003% carbon is said to increase the yield (see http://en.wikipedia.org/wiki/LiH ).
To release the Hydrogen, add water:
LiH + H2O → LiOH + H2
But, if you do not like this path, then please note H2 appears not to form hydrides with the following metals: Mn, Fe, Co, Mo, Tc, Ru, Rh, Ag, W, Re,
Os, Ir, Pt, Au, Fr, Ra and Pm. However, this does not ensure that the metals themselves will not be embrittled. And, if Iron is embrittled, would an
alloy with some Co (or Mn) behave differently? Also, noting the ability of carbon to influence the reaction between Li and H2 in forming a hydride,
would carbon-free steel be less sensitive to embrittlement? To answer this question and many more, I suspect a lot of work would be required.
[Edited on 15-9-2012 by AJKOER]
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Poppy
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| Quote: Originally posted by AJKOER |
LiH + H2O → LiOH + H2
But, if you do not like this path, then please note H2 appears not to form hydrides with the following metals: Mn, Fe, Co, Mo, Tc, Ru, Rh, Ag, W, Re,
Os, Ir, Pt, Au, Fr, Ra and Pm. However, this does not ensure that the metals themselves will not be embrittled. And, if Iron is embrittled, would an
alloy with some Co (or Mn) behave differently? To answer this question and many more, I suspect a lot of work would be required.
[Edited on 15-9-2012 by AJKOER] |
AJKOER could you please verify on the Pt, Ir, Rh, Au, Ra and Tc metals of the list please?
------------------------------------------------------
I don't get you guys why not use a rubber or plastic sealed layer inside the pressure vessel? I think if you put enough effort on it you can line one
of those at home. If the garage of yours is not decent enough to prepare this then you should not be even dealing with the gas !!
[Edited on 9-15-2012 by Poppy]
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AJKOER
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I believe I gave this reference above, but here is the quote:
"Almost all of the elements form binary compounds with hydrogen, the exceptions being the noble gases and Mn, Fe, Co, Mo, Tc, Ru, Rh, Ag, W, Re, Os,
Ir, Pt, Au, Fr, Ra, Pm, and some of the actinides.[1][2][3][4]"
Link: http://en.wikipedia.org/wiki/Hydrides
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phlogiston
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| Quote: | | could i reduce likelihood of structural damage by painting the inside of the container? |
Highly unlikely using common paint. An illustrative experiment to show just how easily hydrogen diffuses through layers of plastic etc is to fill a
common balloon with it. In just a few hours enough hydrogen will have diffused away through the membrane to reduce its lift such that it won't float
anymore.
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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vmelkon
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How about Cr?
http://en.wikipedia.org/wiki/Chromium
"Chromium, unlike metals such as iron and nickel, does not suffer from hydrogen embrittlement. However, it does suffer from nitrogen embrittlement,
reacting with nitrogen from air and forming brittle nitrides at the high temperatures necessary to work the metal parts.[5]"
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AJKOER
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Vmelkon:
Chromium apparently readily forms a brittle hydride. Per Wiki (http://en.wikipedia.org/wiki/Chromium_hydride ), "Electroplating chromium metal from a chromate solution involves the formation of chromium
hydride. If the temperature is high enough the chromium hydride rapidly decomposes as it forms, yielding microcrystalline body-centred cubic chromium.
Therefore, to ensure that the hydride decomposes sufficiently rapidly and smoothly, chromium must be plated at a suitably high temperature (roughly
60C to 75C, depending on conditions). As the hydride decomposes, the plated surface cracks."
Also: "The hexagonal form spontaneously changes to normal chromium in 40 days, whereas the other form (face-centred cubic) changes to the body-centred
cubic form of chromium in 230 days at room temperature. Ollard already noticed that hydrogen is evolved during this transformation, but was not sure
that the hydrogen was an essential component of the substance, as electrodeposited chromium usually contained hydrogen. Colin G Fink observed that if
the hexagonal form was heated in a flame that the hydrogen would quickly burn off."
So, one may be able to plate CrHx (x = 1, 1.7, 2,...) on at low temperature (to preserve the hydride layer) and perhaps, at least temporarily, create
a Hydrogen proof metal (not embrittled) encasement via hydride platting.
Note, as the decomposition reaction is:
CrH2 --> Cr + H2 (g)
one may be able to extend the life of the Chromium hydride plate by placing it in a pressurized container of Hydrogen, as this would move the above
reaction to the left.
[Edited on 25-9-2012 by AJKOER]
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