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Up Topic Welding Industry / Technical Discussions / Galvanized Paint Removal
- - By engineer1 Date 12-10-2002 00:02
AWS D1.1 , section 5.15, allows for welding through "a thin rust inhibitive coating". For structural integrity, should we require removal of cold galvanizing paint on black steel components that are to be welded outdoors for conformance with D1.1, assuming the operators use procedures that mitigate fumes if needed?
Parent - By DGXL (***) Date 12-10-2002 00:18
I would give a whole-hearted: YES.
The galvanizing should be removed. It is possible to weld over the zinc, but the likelyhood of inclusions, porosity and other discontinuities will be high.
Parent - - By TimGary (****) Date 12-10-2002 01:05
I seem to rember that the only way that you may be technically allowed to weld over painted/coated materials is to back up the practice by qualifying a procedure with the same coating applied to the test coupons.
Basically if you can prove that no adverse affects from burning through the coating reduce the physical properties of the weldment you are clear to go. However, if the coating and/or the coating thickness changes you have to re-certify.
Please keep in mind that I am quoting from memory with a brain that has too many burnt cells and may be confusing AWS, ASME and API codes.
Somebody please tell me if I'm right or wrong...
Tim
Parent - - By jwright650 (*****) Date 12-10-2002 15:42
It's easier to just burn off the Galvanized coating with a torch, than to go through all the testing to qualify it. Grinding does not remove all of the coating as you might think, as it remains in the grinding disk and is redistributed back into the joint. There have been several discussions on this topic in previous posts if you care to look back.
Grab that old torch,
John Wright
Parent - By Weldmedic (*) Date 12-11-2002 11:41
Yes the cold galvanizing paint should be removed. It really does not fall into the classification of "thin rust inhibitive coating" . Bloxide primer is one example of the coating we are speaking of. Other shop primers may be weldable according to the mfg or the fabricator but that also depends on the thickness applied to your base metal..Basically if it will interfere with the welding process, best to remove. Also consult the MSDS to assure that removal process will not produce hazardous fumes.
Up Topic Welding Industry / Technical Discussions / Galvanized Paint Removal

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