[rooster]

Hello my name is Robert and I'm NOT a chemist. My background is architectural engineering. So if my question seems amateurish, you'll know why. So here goes.

Scenario-
I've constructed a hydrogen cell using 304 grade stainless steel, encased in PVC and NaOH as an electrolyte. The cell is drawing 15A @ 6.5V.

Now, here are the questions.
1. Is the stainless steel susceptible to hydrogen embrittlement?

2. If so, how can I prevent it from happening by either pretreatment or post-treatment?

Thank you in advance
Rob

[eugenedakin]

Hello rooster,

I hope that I can answer your questions clearly.

1. Is stainless steel susceptible to hydrogen embrittlement?

Threre are a few assumptions that I am making with your question, so feel free to correct me if I misinterpret your question. I am assuming that you have a weak (3%) concentration of caustic soda (NaOH). Hydrogen embrittlement occurs by the movement of hydrogen into the metal. The good news is that there is a slim chance that you will get hydrogen embrittlement ... but... you are producing hydrogen. Hydrogen generation can lower the pH, neutralize the NaOH and then, hydrogen embrittlement can occur. Certain types of stainless steel can be susceptible to hydrogen embrittlement. It really depends on the type of stainless steel and the concentration of hydrogen.

2. I would need to understand your type of hydrogen generation to understand how to you are creating hydrogen, and the area for contact.

Sorry, there is no easy answer. This is a complicated question.

Sincerely,

Eugene

[rooster]

Thank you Eugene.

Your interpretation of my problem was quit accurate. Thus far your answers are more than adequate.

1. Yes, I'm using less than 3% NaOH concentrate. The SS is 304 Grade (Cooking Standard) and yes I'm producing hydrogen through electrolysis.

2. The production of hydrogen is being generated by applying 6Volts DC @ 15Amps=90Watts thus producing 1 - 1.5lpm of hydrogen.

I hope that my description is more helpful this time around. Any insight would be greatly appreciated.

Thanks in advance.
Rob

[rooster]

Eugene,

Hello again! If I had been thinking I could of just asked this question as well.

If I inject this hydrogen production from the fuel cell into a internal combustion engine, will it cause embrittlement of the engine? I heard that it will. Any thoughts on this matter?

Rob

[eugenedakin]

Hello Rooster,

That is a much better question  Thank you!

Again, here is the assumption... The hydrogen that you generated is present as H₂ gas, and NOT as H⁺ ion (and it many variants such as HCl due to contaminants in the process and water).  When the gas is H₂, there is almost no embrittlement.

The way that hydrogen embrittlement occurs is that H⁺ ions permeate the metal and two H⁺ ions form H₂ gas inside the metal. The gas needs to escape, builds up pressure and separates the metal in layers.

As a general rule of thumb "Steel with a ultimate tensile strength of less than 1000 MPa or hardness of less than 30 HRC are not generally considered susceptible to hydrogen embrittlement."

If your metal meets this criteria, your metal will probably have a longer life.

Great question!

Sincerely,

Eugene

[rooster]

Eugene,

You´ve been a great help. Thank you for you time.

Rob

[rooster]

Hi Eugene,

After that invigorating lecture that you gave me, I shared it with another forum that I belong. It was very, very useful information for the bunch of us, but one question did come up that I cannot answer intelligently. Maybe you can be of some assistance again.

What is the likelyhood that any car manufacturer would fall below, what you considered to be safe standards against embrittlement?

"Steel with a ultimate tensile strength of less than 1000 MPa or hardness of less than 30 HRC are not generally considered susceptible to hydrogen embrittlement."

Are there any concerns that we should be concerned with?

Thanks again.

[eugenedakin]

Hello rooster,

For some reason, there will always be at least one car manufacturer which will not heed the warnings supplied to it ... for whatever reason.

Any time that a newer fuel system has been promoted, there has always been at least one manufacturer that has had 'issues' with components of one form or another. This could be due to complying with copyrights, new intelectual property or just plain misunderstanding.

My guess, is that there will be at least one, because of the 'human nature' of developers.

Sincerely,

Eugene