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Fw: Welding Over Galvanizing

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I use to work for an architectural precast concrete panel manufacturer who
did a lot of in-house testing of welding galvanized steel.  Consistently,
filet welds of A36 flat bar in a "T" configuration were found to posses
excessive porosity and micro-cracking, as determined by coupon-sectioning
and etching.  After much in-house experimentation and consultation with AWS,
a procedure was developed to provide a 1/16 inch "gap" between parts being
welded.  This gap provided a path for the molten zinc to escape and not be
trapped within the weldment.  Consistent testing with this procedure
indicated "no" porosity and "no" microcracking as evidenced by
coupon-sectioning and etching.  All other portions or a normal AWS fillet
weld procedure were followed.  The resulting welding procedure was approved
by AWS in the form of a letter.

It became company policy to gap rather than remove galvanizing from weldment
areas after field study determined it to be the  solution that cost the
least.

Hope this is of some help.

----- Original Message -----
From: <Tom.Hunt(--nospam--at)d-fd.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Monday, October 01, 2001 11:20 AM
Subject: Welding Over Galvanizing


> Normally when welding galvanized steel we remove the zinc coating by
> grinding or other suitable means two inches either side of the weld.  I
> have heard that leaving the galvanizing is not good but not necessarily
> detrimental as long as all the other procedures and QA are followed.
> Obviously there is a venting concern for the gasses produced.
>
> Does anyone know the extent of the problems and detrimental effects the
> zinc may have on the weld?  I have a case where I need to fix a field
> problem and removing the galvanizing may be difficult.  This would be a
1/2
> inch fillet weld on new A36 3 inch diameter galvanized rods (+/- 4
months).
>
> Thanks,
>
> Thomas Hunt, S.E.
> Duke/Fluor Daniel
>
>
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