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Hydrogen embrittlement of aluminum castings

I am designing a casting which will be exposed to hydrogen gas. My preference is to use aluminum for weight and cost consideration but am concerned about Hydrogen Embrittlement.
Is there a surface finishing process either a coating or plating method that would seal the surface from hydrogen gas and hydrogen embrittlement of the aluminum casting?

Matt Carroll
castings designer - Sandusky, Ohio, USA
September 9, 2010

Why do you think that aluminum will suffer from hydrogen embrittlement?
Even medium hard steel does not suffer from it.
Hard high tensile strength steel does, but aluminum is not even close in either of these areas.

James Watts
- Navarre, Florida

Sir:

I had one practical experience with hydrogen embrittlement. In a hot dip galvanizing shop a worker threw some aluminum outboard engine propellers into a caustic tank to clean them. After an hour or so the propellers were brought out of the caustic and dumped on the floor. Most of them broke into several pieces.

I asked a guy who was supposed to be knowledgeable and he said that atomic hydrogen (a hydrogen atom which is very small) was formed on the surface of the aluminum and migrated into the castings and found other hydrogen atoms and formed hydrogen gas (H2) and became bigger and more and more hydrogen gas was formed inside the aluminum castings until the pressure caused the castings to break upon shock from hitting the floor. Thus I wonder if molecular hydrogen gas could even enter into the aluminum castings. Frankly I do not know, but I expect an expert metal guy would know.

Regards,

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

Hi,

A quick googling shows claims and counterclaims about whether hydrogen embrittlement of aluminum exists as a practical problem, and whether hydrogen gas can offer the monoatomic hydrogen responsible for it -- but I am not a metallurgist either.

(Caustic readily dissolves aluminum. It is often used to strip the anodized layer off of aluminum, but timing is important in order to not destroy the aluminum object. Some complicated hollow parts are built by electroforming nickel onto aluminum mandrels and then completely dissolving the aluminum in caustic).

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Ted is available for instant help
or longer-term assistance.
September 11, 2010

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