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Re: STEEL: Galvanizing of High-Strength Bolting

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Go to the AISC web site and download the RCSC "Specification for Structural Joints Using ASTM A325 or A490 Bolts".  Section 2.3 has a two page commentary on galvanizing high strength bolts.  The short answer is that it is permissible to hot dip or mechanically galvanize A325 bolts however A490 bolts can not be galvanized at all due to possible hydrogen embrittlement.  Note also that A325 twist off bolts may only be mechanically galvanized in order to maintain consistency in the torque values to twist off the spline.

Thomas Hunt, S.E.
ABS Consulting

"Polhemus, Bill" <bill.polhemus(--nospam--at)>

06/07/2005 03:56 PM

Please respond to

STEEL: Galvanizing of High-Strength Bolting

Years ago the claim arose that mechanical galvanizing of A325 bolts was the only acceptable method, that hot-dip galvanizing tended to cause problems with (er, "grain growth?" or something?).

This may be why there are no longer A325 Type 2 bolts, I dunno.

What is the current thinking? I haven't thought about this for some time, and in typical structural engineery fashion I just keep putting "mechanical galvanizing only" on the drawings and specs.

I'd like to know what you all are doing.

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