goldberg
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Hydrogen Embrittlement - when to worry about it
There is thread about this same topic but i did not found answer to my question.
This thread is pretty old so i decide to start new one. If that's wrong, i'm sorry for that in advance.
I read that many metals and alloy are getting brittle in contact with hydrogen.
But i did not found any numbers and conditions describing this.
I would like to know at what pressure and temperature 304 stainless steel will get brittle.
I'm thinking about building small medium-pressure (up to 20atm) hydrogenation vessel.
Parr uses 316 steel but this is hard to get in place where i live. At the other hand i can easily acquire 304 steel. I am also considering small fire
extinguisher.
Temperature would intentionally not exceed 100C, pressure up to 20atm. Should i worry about embritlment or not? I do not like idea of steel vesses
suddenly exploding in my face after a few reactions. If that's matter later i plan to experiments with applying ultrasounds during hydrogenation to
see if it will actually affect nickel catalyst.
If 20atm at 100C is OK to what pressure i can safely go up?
(i will see how much pressure i will be actually able to get)
I did not managed to find any information about that.
Recomendations for other materials for such vessel are highly welcome too.
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DavidJR
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This is also known as HTHA: high temperature hydrogen attack. It is a function of the partial pressure of hydrogen, the temperature, and the contact
time.
See this document from the American Petroleum Institute:
Attachment: API-RP-941-2004.pdf (775kB)
This file has been downloaded 3553 times
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Fulmen
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There are several challenges with hydrogen, embrittlement is as far as I can tell mostly a problem with high strength alloys (Rm > 1000MPa /
32HRC). Most austenitic steels (including 304) should be fairly resistant. There is also hydrogen induced cracking, this is caused by elemental
hydrogen diffusing out of the steel into pores and defects. I have actually seen a piece of 2" thick steel with a large 1/2" thick "blister" in the
middle caused by long term exposure to pressurized hydrogen.
Embrittlement can apparently occur at low pressures and temperatures, for instance during plating. Cracking will most likely require long exposures at
fairly high pressures.
We're not banging rocks together here. We know how to put a man back together.
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Fulmen
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A quick read tells me this is a very complicated field. Finding simple engineering tables might not be possible.
As I understand it embrittlement is caused by hydrogen acting like an alloying element. This could happen quite fast even at low temperatures, so I
would avoid high strength steel all together. If high strength is needed austempering might increase resistance.
Hydrogen induced cracking will require much more hydrogen to diffuse into the steel, so here I would expect a time/pressure/temperature-depended
response. Annealing should reverse the process to some degree.
We're not banging rocks together here. We know how to put a man back together.
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Herr Haber
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I'm pretty sure you can find some info looking into the Haber-Bosch process as hydrogen embrittlement was one of the majors problems that had to be
overcome.
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XeonTheMGPony
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The hydrogen reacts with carbon forming methane and slowly converting the steel to plain old iron.
the 300 series of stainless is the most resistant, 316L being best.
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goldberg
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@DavidJR: Thanks for this pdf.
@Herr Haber: Good idea, thanks.
So summing up 304 steel is not bad choice (parr uses 316 for his hydrogenation apparatus)
I also found mention somewhere that parr apparatus will operate at abot 10bar.
So my idea of carrying out hydrogenation in 304 steel at 10-20bar at 100C is not that bad.
Unfortunately there is no possilibity to put something like safety valve that will break first.
So should i just put some bags with sand (poor man's protective screen) around hydrogenation vessel and go ahead or this is overkill?
I would prefer to ask how much i should worry instead of being injured by blowing up vessel.
I hope that welding does not change situation there. I know that i have to chemically treat stainless steel after welding.
On sciencemadness wiki there is only mention that it is hard to build hydrogenation apparatus out of OTC materials.
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XeonTheMGPony
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Preheat the stainless befor any welding then slow cool.
Best is 316L (L means low carbon) but all ells fails 304, just stick it in a bucket with damp sand and don't sit on top of it and all will be well
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zed
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Ummm. You are working at pressures that require gauges. The innards of your gauges will probably be a lot more vulnerable to embrittlement, than the
pressure vessel itself.
Some types of gauges hold up well, and some don't.
On such an important matter, one might think that gauge manufacturers would supply some critical information on the capacity of their gauges to
survive use with hydrogen. Sadly, such information is generally not at the forefront.
Perhaps someone here, knows something about economical gauges, that are suitable for use with Hydrogen?
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DavidJR
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Quote: Originally posted by zed  | Ummm. You are working at pressures that require gauges. The innards of your gauges will probably be a lot more vulnerable to embrittlement, than the
pressure vessel itself.
Some types of gauges hold up well, and some don't.
On such an important matter, one might think that gauge manufacturers would supply some critical information on the capacity of their gauges to
survive use with hydrogen. Sadly, such information is generally not at the forefront.
Perhaps someone here, knows something about economical gauges, that are suitable for use with Hydrogen?
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I think if the innards of a pressure gauge were to rupture, this would likely just result in the contents venting out, rather than the catastrophic
failure which would result from the pressure vessel itself rupturing
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zed
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It isn't the rupturing of the gauges that I am concerned about. I'm talking about small inner-parts breaking due to embrittlement, thereby ruining
the gauges.
Gauges can be quite spendy, especially if you pay full price.
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goldberg
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Thanks for your responses and pointing out possible problem with gauges.
I will look what is avaiable on market.
There is also problem with pump.
I would like to make hydrogen by electrolysis of basic solution of water.
Generation pressure (say 10 to 20atm) is tricky because i will need suitable electrolytic bridgne that will withstand pressure and will prevent
contamination of hydrogen with oxygen.
OTOH some unglazed porcelain is good for electrlytic key without pressure. Maybe i can make it robust enough to withstant 20atm? But hydrogen might
want to diffuse through it, right?
I did not found any information if hydrogen actually can diffuse and escape via electrolytic key...
Other way is to collect hydrogen in bottle under water and from this bottle pump it to the vessel (i'm thinking about rather small scale 0.25l up
maximum 0.5l). Cheap electric bike pumps should give 10atm and they are cheap. I will need to figure out how i can attach supply of gas other than
environment to them.
Third option is reaction of aluminium with NaOH but kipp apparatus is not able to give elevated pressure.
I do not like idea of forcing basic solution with argonium from bottle.
I do not want to put motor immersing rod of aluminium into caustic solution in pressure bottle
because building it will be very labour intensive and fragile.
I need some way to control this reaction. Any ideas welcome.
I checked Vogel book but he described only atmospheric pressure apparatus.
I do not want to work with hydrogen bottles due to safety and economic reasons. (dangerous, expensive and hard to get)
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Ubya
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do you have an empty fire extinguisher? fill it with NaOH solution and aluminium scraps (foil or small chunks), put a regulator on the tank outlet,
and after that a mist filter and a dessicant vessel. this would give you water free hydrogen already pressurized.
ps vent a few times the tank to remove the air inside or if you have it use a vacuum pump, by using larger pieces of aluminium you would have more
time to evacuate tge extinguisher. oxygen free pressurized hydrogen
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goldberg
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I have empty fire extinguisher. But how i can control reaction of it?
Second i need to empty vessel before starting making hydrogen, otherwise lot of it will be wasted.
I do not want to force solution of NaOH by argonium from bottle.
Making something syrgine-like that will be able to force solution into reaction vessel is non trivial.
I am not sure about leaks in bike pumps, small leak can have vary bad consequences...
Any other ideas how to pump such corrosive solution? Persitaltic pumps are rather not going to work well with high pressures.
Heating hydrides is not an option.
I do not see lot of possibilites to control reaction of aluminium and NaOH other than stopping addition of solution of NaOH.
I tried to find information about details of pressure electrolysers for hydrogen but did not managed to find anything usefull.
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Ubya
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| Quote: Originally posted by goldberg | I have empty fire extinguisher. But how i can control reaction of it?
Second i need to empty vessel before starting making hydrogen, otherwise lot of it will be wasted.
I do not want to force solution of NaOH by argonium from bottle.
Making something syrgine-like that will be able to force solution into reaction vessel is non trivial.
I am not sure about leaks in bike pumps, small leak can have vary bad consequences...
Any other ideas how to pump such corrosive solution? Persitaltic pumps are rather not going to work well with high pressures.
Heating hydrides is not an option.
I do not see lot of possibilites to control reaction of aluminium and NaOH other than stopping addition of solution of NaOH.
I tried to find information about details of pressure electrolysers for hydrogen but did not managed to find anything usefull. |
how do you control the reactio? you don't. just put inside the fire extinguisher enough aluminium and sodium hydroxide solution to fill it with (let's
say) 15 bars of hydrogen. now you have a fire extinguisher pressurized with 15 bars of hydrogen, no need to control any reaction, you put a pressure
regulator inline with reaction vessel and the fire extinguisher. you want to remove air from the tank, you can use a vacuum pump, a water aspirator, a
hand pump, you name it, as you remove air it will be displaced sith hydrogen (if you use larger pieces of aluminium you have a longer induction period
to do this job), or you could just leave the valve open (without pulling a vacuum first) and let the formed hydrogen displace the air inside the tank.
i don't see how this method could be problematic, it's not hard as you think, no need to pump corrosive solutions unde high pressure
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goldberg
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I understood. Theoretically this is a way to go but i do not like idea of generating whole hydrogen at once.
OK i am doing to work only with small scale but still.
I will use it i not manage to find any better way.
Or maybe there is a better way to generate hydrogen?
Electrylysis of water is super easy to control but there is problem with generation of oxygen.
Will hydrogen diffuse through eletrolytic key? Or maybe i could collect oxygen under pressure too.
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Ubya
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electrolysis is way harder, you need a custom made pressure vessel divided in two cells with a pressure resistent membrane in between, then you would
need to build 2 electrical insulating feedthrough resistent to high pressure.
ps remember even if this was a sealed system the pressure of H2 would be double that of O2
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Fulmen
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Both energy requirements and difference in gas volume speaks against electrolysis. A chemical route can supply all the energy required, NaOH/Al seems
like the obvious route when one considers cost and availability.
Make sure that your components are chemically compatible with all chemicals (no nasty side-reactions), do the math. TRICE! Then stand well back. A
bit further. A bit more. That's fine... 
We're not banging rocks together here. We know how to put a man back together.
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AJKOER
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Some possible helpful background comments with sources on hydrogen embrittlement for various metals. First with chromium:
"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."
My point is if one is going to give credit to the hydrogen, don't ignore the role of the highly anodic metal, or transition metals with multiple
valence states, as sources of the mono-atomic hydrogen radical (.H formed courtesy of the anodic metal or high temperatures), or as historically
sometimes referred to, in my estimation, as 'nascent' hydrogen. Here is a recent account of the surface chemistry of adsorbed .H on aluminum and
applications, see https://books.google.com/books?id=1etfSdk55SYC&pg=PA817&... . This last reference per Equation (5) appears to support my reaction presentation
in terms of 2 .H (which is adsorbed on an aluminum surface) and not H2, to quote:
" PbS + 2 .H = Pb + H2S (5) "
Prior comment relating to Al/Mg:
| Quote: Originally posted by AJKOER | Found some support suggesting that the cathodic reaction I detailed previously above proceeds per the Aluminum path cited above with Magnesium,
namely:
H2O + e- → OH- + .H
along with the corresponding reaction of the created monatomic hydrogen radical with Magnesium to form a hydride:
Mg + 2 .H → MgH2
My support is from a reported observation published long ago from "Chemical News and Journal of Physical Science, Volumes 87-88, p. 312, link: https://books.google.com/books?id=jvjmAAAAMAAJ&pg=RA1-PA... , to quote:
"Solutions of the chlorides of barium, strontium, and calcium were acted upon but feebly by magnesium, but ammonium chloride solution was attacked at
a lively rate. "
Also, on page 314, to quote:
"It is especially interesting to note that the alcohol solution IS much more vigorous in its action on magnesium than is pure water. The urea solution
is relatively vigorously attacked, though, as has been stated, ammonia is also formed in this case."
In my opinion, with respect to the above observation of the reaction between Mg metal and aqueous NH4Cl, it is consistent with the reaction of aqueous
NH4+ with e-, creating the hydrogen atom radical:
NH4+ + e- = NH3 + .H
where the above reaction could be viewed as flowing from the better known reaction:
H+ + e- = .H
as upon adding NH3 to both sides of the above: NH3 + H+ (= NH4+) + e- = NH3 + .H as claimed above. Another way of viewing this is that NH4+ is a
very weak acid:
NH4+ = NH3 + H+ (see https://www.google.com/url?sa=t&source=web&rct=j&... )
So, upon adding e- to each side:
NH4+ + e- = NH3 + (H+ + e-) = NH3 + .H
as required. In my opinion, the above reaction could provide an added avenue for the creation the monoatomic hydrogen radical that, especially in near
neutral water as per the reported experimental observation above, could enhance the reaction rate.
With respect to the observation of increased reactivity with alcohol over water, this supports the idea of an anodic half cell reaction (likely
consuming MgH2) forming solvated electrons, as ethanol is a cited preferred medium over water. Further, the chemical breakdown of Urea to NH3 supports
a possible underlying electron transfer mechanism (like via solvated electrons).
Also note, the cited Magnesium employed in the reference above is said to contain a small amount of a transition metal (Iron) and Aluminum oxide. Per
a source (page 127 of a Phd thesis by Anna Grzech, "Hydrogen Storage in Porous Materials and Magnesium Hydrides", available online as a 17.1MB pdf) to
quote:
"some of the transition metals [13], transition metal oxides [14,15] or hydrides, transition metal halides (NbF5, TiF3, FeF3)[16-18] are
widely investigated as additives. These are believed to act as a catalyst for the chemisorption of hydrogen and transport into the
magnesium phase. [2] Among of these TiF3 additive appears to be a particularly effective catalyst. [10,19,20] "
Abstract of the cited reference [13] "It has been revealed that ball-milling of MgH2 powders with small amounts of selected 3d-transition metals M
such as Ti, Nb, … or oxides of 3d-metals (e.g. Cr2O3) leads to marked improvements of the hydrogen absorption/desorption kinetics"
So, I would expect that select transition metals (or their oxide) impurities, or present as alloys, could increase reaction rate.
[Edited on 25-5-2017 by AJKOER] |
Here is a 2008 thesis, "Alkaline dissolution of aluminum: surface chemistry and subsurface interfacial phenomena", by Saikat Adhikari, link: https://www.google.com/url?sa=t&source=web&rct=j&...
I believe a similar electrochemical reaction scheme is occurring with Magnesium. Some extracts of interest for the brave, to quote:
"In addition to being a primary corrosion process, dissolution behavior of aluminum and its alloys in alkaline solutions is of
considerable interest because it is the anode reaction in aluminum-air batteries.[4] ......The anodic half-reaction at the Al electrode
is
Al + 4 OH − → Al (OH)4− + 3 e− (1.1)
which exhibits an electrode potential of -2.35 V in alkaline solutions(vs. NHE).
"2 Al + 6 H2O → 2 Al (OH)3 + 3 H2 (1.2)"
....."dissolution of aluminum in alkaline solutions at open-circuit also leads extremely high rates of H-absorption into the metal,
[9-14] ".....
"Another study of the dissolution of aluminum in aqueous solutions by Perrault revealed that the open circuit potential of aluminum
in strongly alkaline solutions corresponds closely to the Nernst potential for oxidation of aluminum hydride to aluminate ions [25]
AlH3 + 7 OH− (aq) → Al (OH)4− + 3 H2O ( aq ) + 6 e− (1.3)
This suggests a role of surface aluminum hydride as a reaction intermediate in the dissolution process. Additional evidence for the
presence of aluminum hydride was provided by Despic and co-workers.[26, 27] They found that aluminum hydride formation was one of
the major processes apart from aluminum dissolution and hydrogen evolution, during the cathodic polarization of aluminum. Titanium
corrosion in alkaline solutions is also thought to proceed through a hydride mediated mechanism.[28-30] "
"He found that the open-circuit potential in strongly alkaline media was determined by the equilibrium of the reaction
AlH3 + 7 OH− (aq) → Al (OH )4- + 3 H2O ( aq ) + 6 e− (3.7)
He obtained a standard chemical potential of 25 kcal/mol for AlH3 from his data, which was in reasonable agreement with prior
thermochemical calculations done by Sinke et al who obtained a value of 11.1 kcal/mol for the chemical potential.[80] ...."
"The anodic reaction 3.7 is accompanied by the cathodic reduction of water to form hydrogen
H2O + e- → OH- + H (3.8)
and the reaction of hydrogen with aluminum to from hydride
Al + 3 H → AlH3 (3.9)"
So, a bit technical but related half cell reactions I would guess for the likes of Magnesium.
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....
Note, even in aqueous settings, long ago there are reports of unexplained reactions of various salts with Mg metal, including converting nitrate into
nitrite and finally ammonia (see, for example, p. 314 at "Chemical News and Journal of Physical Science, Volumes 87-88, 1903, p. 312-316, link: https://books.google.com/books?id=jvjmAAAAMAAJ&pg=RA1-PA... ).
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[Edit] Here is an interesting article citing a temperature and Magnesium alloy presence associated with hydride formation: "absorption of hydrogen by
magnesium based alloys", in METAL 2014, link: https://www.google.com/url?sa=t&source=web&rct=j&...
This short discussion on preparing the Mg for interaction with H2 may be of value: https://books.google.com/books?id=NR3OxpSiA60C&pg=PA491&... "
In general, I would outline the surface chemistry as follows based on the reaction of metals like, Iron, Aluminum, Magnesium, for example, with water
in the presence of a good electrolyte like NaCl:
H2O = H+ + OH-
Fe + 2 OH- → Fe(OH)2 + e-
H+ + e- = .H
.H +.H → H2
…….
Now, in the case of Aluminum, indeed more possible electrochemical reactions, which I would express as follows, in the presence of an electrolyte like
NaCl:
H2O = H+ + OH-
Al + 3 OH- → Al(OH)3 + 3 e-
H+ + e- = .H
.H +.H → H2
.H + e- = H-
Al (surface)→ Al(3+) + 3 e-
Al(3+) + 3 H- →AlH3
AlH3 + 3 H2O → Al(OH)3 + 3 H2
……
To quote a source:
“In addition to being a primary corrosion process, dissolution behavior of aluminum and its alloys in alkaline solutions is of considerable interest
because it is the anode reaction in aluminum-air batteries.[4] ......The anodic half-reaction at the Al electrode is
Al + 4 OH − → Al(OH)4− + 3 e− (1.1)
which exhibits an electrode potential of -2.35 V in alkaline solutions(vs. NHE).
"2 Al + 6 H2O → 2 Al(OH)3 + 3 H2 (1.2)"
Also:
....."dissolution of aluminum in alkaline solutions at open-circuit also leads extremely high rates of H-absorption into the metal, [9-14] ".....
"Another study of the dissolution of aluminum in aqueous solutions by Perrault revealed that the open circuit potential of aluminum in strongly
alkaline solutions corresponds closely to the Nernst potential for oxidation of aluminum hydride to aluminate ions [25]
AlH3 + 7 OH− (aq) → Al(OH)4− + 3 H2O ( aq ) + 6 e− (1.3)
This suggests a role of surface aluminum hydride as a reaction intermediate in the dissolution process. Additional evidence for the presence of
aluminum hydride was provided by Despic and co-workers.[26, 27] They found that aluminum hydride formation was one of the major processes apart from
aluminum dissolution and hydrogen evolution, during the cathodic polarization of aluminum. Titanium corrosion in alkaline solutions is also thought to
proceed through a hydride mediated mechanism.[28-30] "
"He found that the open-circuit potential in strongly alkaline media was determined by the equilibrium of the reaction
AlH3 + 7 OH− (aq) → Al(OH)4- + 3 H2O ( aq ) + 6 e− (3.7)
The obtained a standard chemical potential of 25 kcal/mol for AlH3 from his data, which was in reasonable agreement with prior thermochemical
calculations done by Sinke et al who obtained a value of 11.1 kcal/mol for the chemical potential.[80] ...."
Source: A 2008 doctoral thesis , "Alkaline dissolution of aluminum: surface chemistry and subsurface interfacial phenomena", by Saikat Adhikari, link:
http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=16827&...
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Based on all of the above comments, relating to the thread topic, 'Hydrogen Embrittlement - when to worry about it', my answer would be it is a
concern when working with metals (or alloys) with high anodic index (like Mg, Al, Zn, Fe,....) acting as a source of e-, or transition metals with
various valence states (like Cr, also a source of e-) and associated reaction with water (or other source of H+ like an acid, or an acid salts
including NH4Cl (aq)) in the presence of an electrolyte (sea salt,...) per some of the chemistry detailed above creating the hydrogen atom radical, or
at high temperatures acting on H2 (H2 + Heat ⇆ .H + .H) and since, .H + e- = H-, possible associated hydride formation.
Note, .H is also formed in electrolysis or sonolysis settings, and also by high pressure H2 interacting with a source of the hydroxyl radical (.OH):
H2 (g) + .OH ⇆ .H + H2O
[Edited on 23-10-2018 by AJKOER]
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