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Base Metal Preparation

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I am interested in List opinions regarding the need to grind the zinc
coating off of galvanized metals prior to welding. The following text is
from an e-mail message I sent to the Senior Staff Engineer with AWS.

----------------------------------------------------------
Dear Mr. Campbell:

My name is Brent Koch. I am a project engineer and a project manager with
Willis Construction Company, an archictural precast and GRFC cladding panel
manufacturer in California.  I have been referred to you by Mark Hildebrand,
our chief engineer, for your opinion regarding the need to grind the zinc
coating off of galvanized metals prior to welding.

As I'm sure you know, galvanized finishes are occasionaly specified for
connections of precast cladding panels. I've run across two opposed schools
of thought [and two schools of enforcement] regarding the necessity to
remove the coating at and around welds.

AWS D1.1 Section 3.2.1 says, "Surfaces to be welded, and surfaces adjacent
to a weld shall be also be free from loose or thick scale, slag, rust,
moisture, grease and other foreign material that would prevent proper
welding or produce objectionable fumes."  This is the only specification
section that I have been able to associate with welding of galvanized metal
finishes.

Is the galvanizing a foreign material that prevents proper welding and
therefore must be removed? (FYI - The welder will be wearing a respirator so
the fumes produced will not be 'objectionable' according to his employer.)

Thank you in advance for information and insights you can provide on this
subject.

Sincerely,

Brent Koch, P.E
Willis Construction Company
Brent(--nospam--at)willislivermore.com