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Hydrogen embrittlement due to NaOH?

March 24, 2010

Hi,
Does H atoms in NaOH solution cause hydrogen embrittlement?

Thanks for your help

Fatma Babacan
engineer - Izmir, Türkiye

Hi, Fatma. Please describe your situation rather than posing an abstract question because the answers to abstract questions require a hundred ifs, ands, and buts :-)

But, in general, I don't think NaOH can cause hydrogen embrittlement because there are no hydrogen ions, only sodium and hydroxide ions.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 24, 2010

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First of two simultaneous responses --

Sir:

My experience is that NaOH solution does not cause hydrogen embrittlement in steel. Even a steel coil or steel fire-tube is quite suitable for heating caustic.

Once while in a hot dip galvanizing plant, I saw several broken cast aluminum boat motor propellers laying on the floor next to the caustic tank. I asked what happened and the plant manager said he tried to clean the propellers in the hot caustic, but when he dumped them on the floor they all broke. Thus aluminum which is amphoteric (reacts with acid or caustic) reacted with the hot caustic and some people might say the aluminum was embrittled.

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA
March 24, 2010

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Second of two simultaneous responses -- March 25, 2010

Hi Fatma Babacan,
If you are sharing your Exact problem , I am able to share/give the solution.
Normally from the NaOH, Hydrogen will not penetrate to the part.
But you are using the NaOH, dilution i.e.. is mixed with H2O, then penetration of Hydrogen is possible.

Kannan Boopathi
- Salem, Tamil Nadu, India

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Because H2 is generated at the cathode, hydrogen embrittlement could result from any electrolytic process where your part is cathodic at any time. Otherwise, it is not likely. I can't say impossible, because I was involved in a rigorous study performed by an aerospace landing gear manufacturer that did show evidence that embrittlement might occur in high strength steel from an immersion-only alkaline stripping solution. The results of the study were mixed, so it wasn't easy to say conclusively either way. The final decision in this particular case which involved fracture-critical parts was to err on the side of caution and perform the embrittlement-relief bake.

Jon Barrows, MSF, EHSSC
GOAD Company

Independence, Missouri

March 25, 2010

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March 30, 2010

Hi again, first of all thanks for your generous help.
Our factory produces fasteners; bolts & nuts, and plate them. The question is about zinc electroplating. when the coating peel off by NaOH, is there any reaction between Zn and NaOH or something different to cause H+ ions?

Dear Barrows,

'I can't say impossible, because I was involved in a rigorous study performed by an aerospace landing gear manufacturer that did show evidence that embrittlement might occur in high strength steel from an immersion-only alkaline stripping solution.'

Could you say me any literature or document about hydrogen embrittlement risk in alkaline stripping solution?
Best regards

Fatma BABACAN
Electroplating - Izmir, Türkiye

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Dear Finishing com followers,
We are coating steel bolts and nuts with zinc since long years in our facility by electrolysis acidic method. To peel off the zinc and to re-coat high tensile products (over 32 HRC), if we use high concentration NaOH solution, would there be any Hydrogen Embrittlement risk?

Please help..

Oytun PINAR
Mech. Eng.
Turkey

Oytun PINAR
Plating Shop Manager - Izmir, TURKEY
March 31, 2010

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To answer your question to me...Unfortunately no, it was an internal study and was not intended to be published.

Jon Barrows, MSF, EHSSC
GOAD Company

Independence, Missouri

March 31, 2010