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dik (Structural)
9 Jul 10 14:35
I know there is a problem with zinc saponification with some coatings over a pre-galvanised material.
Is there a similar problem with the application of epoxies over zinc coating? I will check with specific coating suppliers.
Dik
hokie66 (Structural)
9 Jul 10 18:07
If the galvanizing is new, you will need surface preparation first, probably an etch primer or whip blasting. If the galvanizing is aged, this would not be required. As you are doing, best to check with the coating manufacturer.
dik (Structural)
9 Jul 10 19:54
Thanks, Hokie... but I was hoping for some specific information about problems with epoxies and zinc coating. I've used vinager for a wash to 'kill' the surface with other coatings... but, I've not used zinc with an epoxy coating. 字串8
...it's part of a client coating spec and I want to vet it, personally before I accept this.
Dik
hokie66 (Structural)
9 Jul 10 20:27
I don't know about epoxies, but had experience with a proprietary space frame once, galvanized and coated with polyurethane. Already partly erected when we did adhesion testing, which failed. They had to disassemble it, take it back and remove the polyurethane, prepare the surface and recoat. Expensive lesson learned for the space frame supplier.
You are right to be concerned.
SJones (Petroleum)
10 Jul 10 2:48
MIL-HDBK-1110, Clause 4.4.4 Steve Jones
Materials & Corrosion Engineer
http://www.oilandgaspeople.com/cv/11499664
http://www.linkedin.com/pub/8/83b/b04
dik (Structural)
10 Jul 10 9:21
字串3
Thanks Steve, do you know of a link to the text? Doing a search, I get a connection failed type of message on any of links tried.
Thanks Hokie... not over yet, your comment is exactly the reason for my concern.
Dik
dik (Structural)
10 Jul 10 11:49
SJones... found the book...
thanks, Dik
4.4.4.1 Epoxy Systems. Two coats of epoxy will provide longterm protection to galvanizing in interior service, as will one coat of epoxy and one coat of aliphatic urethane to galvanizing in exterior service.
Epoxy Coating System for Exterior Galvanizing Surface
Preparation Primer Topcoat SSPC SP 1 one coat MIL-P-24441 one coat MIL-C-85285 Formula 150 Type II
3 mils dft 2 mils dft
Epoxy Coating System for Interior Galvanizing Surface
Preparation Primer Topcoat SSPC SP 1 one coat MIL-P-24441 one coat MIL-P-24441 Formula 150 of desired color 3 mils dft 3 mils dft 字串1
Thank you, gentlemen...
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