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Problems with Galvanized A325 bolts

Problems with Galvanized A325 bolts

Problems with Galvanized A325 bolts

(OP)
Is anyone aware of potential problems with ASTM A325 galvanized bolts?  We are specifying them on a project, which is new for this company, and they are very leary of doing so.  Do any of you know of typical problems with these bolts, uses that they are not good for, etc?

RE: Problems with Galvanized A325 bolts

The nuts and bolts should be galvanized by the same supplier and the threads "chased" to ensure the galvanizing does not muck up the threads.

The can only be tightened once, i.e., they can not be reused.

Best regards - Al  

RE: Problems with Galvanized A325 bolts

Provided they are installed and inspected per RCSC spec., this is a common practice.  Galvanized bolts and nuts are considered an "assembly", so they should come from the same supplier/manufacturer, as noted above.   

http://www.FerrellEngineering.com

RE: Problems with Galvanized A325 bolts

I built power transmission towers using lots of galvanized bolts and I dont know of any problems.  

Their practice was to torque the bolts to a much smaller value than you would in typical structural steel.

RE: Problems with Galvanized A325 bolts

Have you considered coated bolts & nuts like a Magna coat?

RE: Problems with Galvanized A325 bolts

They typically use male and female threads that have different tolerances to accommodate the added thickness.

Dik

RE: Problems with Galvanized A325 bolts

(OP)
no, we have not tried that, but i think they are sufficiently comfortable with galvanized A325 bolts and prepared to use them on this project.

thank you for all of the comments.

RE: Problems with Galvanized A325 bolts

As long as they fresh from the factory with the oiled surfaces they are no problem but dry zinc surfaces, moved over each other, under pressure tend to gall. I've seen it when someone tried to use some left over galvanized bolts, left out in the weather for years and very dry and perhaps a little corroded..

Michael.
Timing has a lot to do with the outcome of a rain dance.

RE: Problems with Galvanized A325 bolts

Regarding the A325 bolt (galvanized finish): Does anyone know if the F436 hardened washers are required to be furnished with the bolt/nut assembly? My customer is indicating this is required by code. I understand the requirements of the nut and bolt since A563-S1 requires the testing of the lubricated nut with the bolt to confirm ability to rotate.

thanks
Bryan

RE: Problems with Galvanized A325 bolts

Like any other A325 bolting application, a washer is only required for using torque to install the bolts, vs. turn-of-the-nut or 'snug tight'.  Washers are also required to cover slotted holes.  Period.

RCSC A325 & A490 requirements are attached.

RE: Problems with Galvanized A325 bolts

bradleyelwood,
I doubt your application is nearly as critical as most applications for machine screws.   

RE: Problems with Galvanized A325 bolts

I don't want to sound alarmist but Buy domestic.  We had several thousand 1/2" A325's on a snug-tight pedestrian bridge job that guys were stripping out by hand. Got back to the shop, put them through some torque tests and found out they barely made spec. The domestics were capable of almost twice the load. From that experience I realized some manufacturers will use whatever voodoo they can to hit the numbers.

RE: Problems with Galvanized A325 bolts

We have had engineers specify that A325 assemblys not be galvanized due to concerns about the process making the bolts brittle. I have attached one link that details the problem. these bolts are used on thousands of structures but once in a while some enginner will refuse to accept them. As stated above the problem migh just be offshore stuff but it still is a problem.

RE: Problems with Galvanized A325 bolts

Hydrogen embrittlement is an issue with hot dip galvanizing of A490 bolts.  However research found no embrittlement issues with Zn/Al Inorganic coating of A490 bolts.  Additional information is available in the RCSC Spec commentary.   

http://www.FerrellEngineering.com

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