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View Diary: The New SF Bay Bridge: Proof We Are Now a Banana Republic (163 comments)

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  •  No, it's not a forging issue. (2+ / 0-)
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    Ray Pensador, turn blue

    Hydrogen embrittlement can occur during manufacturing but this is not the problem at hand.

    The problem for the Bay Bridge is that marine environments can create reducing anoxic conditions where hydrogen is produced and migrates into the metal to cause embrittlement.

    Galvanized steel is a cost effective and highly reliable material as long it is used in an oxidizing environment so it can maintain its properties. But, here, it looks like they decided to use it in the wrongestest place possible.

    I would have to dig further into the particulars but I can see at least five different factors at play here.

    - Use of HSLA steel
    - Heavy tensile loads
    - Wet anoxic reducing environment
    - Presence of chlorides (and, likely, presence of sulfides)
    - Use of zinc coating

    It happens that this combination of materials and physical and chemical conditions is extremely favorable to hydrogen embrittlement and failures.

    I deal in facts. My friends are few but fast.

    by Farugia on Fri Aug 23, 2013 at 05:32:24 PM PDT

    [ Parent ]

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