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Up Topic Welding Industry / Technical Discussions / Welding Over Shop Coat
- - By kpauley (*) Date 04-25-2003 16:48
Has anyone out there had to deal with erectors welding over shop coat primers in the field? Bar Joist to beams, Joist Girders to columns, etc... My question is: Are shop coat primers considered "a thin rust-inhibitive coating" as mentioned in D1.1 Section 5.15? Thanks, KP
Parent - - By WBI (*) Date 04-25-2003 17:31
Shop primers are not thin rust inhibiters. They are usually quite thick and have a definite effect on the quality of welds. Thin primers went the way of the wild goose with air quality restrictions on spray painting.

I was involved with a project where primer painted imbeds were set in pre-cast beams with the intention of welding shear clips to the imbeds on the job site. After just two failed tests I required the contractor to heat and wire brush all the imbeds in the area of the shear plates or grinding to bare metal before welding. The design engineer had a fit when he heard what they had done. I think the architect wanted the paint to match the concrete and didn't consult the engineer about what the result might be.
Parent - - By jwright650 (*****) Date 04-25-2003 18:15
They must remove this coating before welding unless an "approved" (submitted and approved by the EOR) weldable coating is used.
John Wright
Parent - By jwright650 (*****) Date 04-25-2003 18:19
I personally don't like the weldable paints in any of the joints that will be field welded either, due to high rejection rates of welds when this paint is used. But some engineers request that we use it.
John Wright
Parent - By CHGuilford (****) Date 04-25-2003 20:13
I wonder if the architect thought burned paint will match the concrete color? Last I knew concrete is light gray instead of black? :)
Chet Guilford
Parent - - By G.S.Crisi (****) Date 04-25-2003 19:14
Good Heavens! I've always thought that welding on painted structural steel was a custom of third world, underdeveloped contractors, like the ones existing in these third world, underdeveloped countries like mine.
I'm astonished at knowing that first world, superdeveloped contractors do the same ..............
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - By jwright650 (*****) Date 04-25-2003 19:35
Yes, Giovanni we do some dumb things sometimes, maybe some out of ignorance, others know better and try to get away with it.
John Wright
Parent - By jon20013 (*****) Date 04-25-2003 19:24
Be EXTRA careful if you go ahead with welding over shop coatings. I was an expert witness in one case where the engineer substituted a shop coating with an "alternate" which "appeared" to have "identical" characteristics. 2 welders died when the weld joints failed due to inclusions ~ need I say more? If you do go ahead with welding over shop coatings, make certain that they are intended for welding over, some are fine but others, which "appear" to have identical characteristics, are not intended to be welded over.
<WHEW! - sorry for the wordiness!>.
Up Topic Welding Industry / Technical Discussions / Welding Over Shop Coat

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