| Author |
Message |
Mark R. Jones, CSI, CCS
Senior Member
Username: mjones
Post Number: 9
Registered: 12-2006
| | Posted on Wednesday, May 12, 2010 - 05:54 pm: |    |
I'm looking for a little information on galvanizing iron process. Is it the same process as galvanizing steel? What are the best products and processes for painting galvanized iron (or steel) for exterior use?
Some background information: A residential project in Chicago will have an exterior decorative metal fence, similar to picket wrought iron fences. The fence and gates will be welded and the client wants a long lasting durable painted finish.
I'm using Section 323119 in Masterspec as a starting point.
Thanks for any information. I'm a frequent reader but seldom poster to 4specs. |
Mark Gilligan SE, CSI
Senior Member
Username: mark_gilligan
Post Number: 280
Registered: 10-2007
| | Posted on Wednesday, May 12, 2010 - 06:22 pm: | |
Galvanizing is the same for steel and iron.
The secret to longivity of paint is the preparation. I would suggest that the same is true for galvanizing. |
John Bunzick, CCS, CCCA, LEED AP
Senior Member
Username: bunzick
Post Number: 1205
Registered: 03-2002
| | Posted on Thursday, May 13, 2010 - 08:47 am: | |
If you specify a manufactured fence with shop-applied coatings, you will likely have the best results. Painting galvanizing in the field is challenging because there are limited products that can do this well. Zinc, which is what galvanizing is, starts to slowly corrode almost immediately. This initial corrosion inhibits the adhesion of paint, and requires careful preparation to insure success. My experience is that the prep is not done well at least half the time. So, galvanizing with a shop-applied primer, at least, or primer and topcoat is a better avenue. The shop should apply the primer within 12 hours of galvanizing so the corrision does not inhibit the adhesion. Use a two-part epoxy primer. Top coat should be a two-part urethane. This is the longest life coating you can get. If done correctly, you could get 30 years or more.
Some shops use a powder-coated polyester, which when done well will give a very long life, too.
Alternatively, skip the galvanizing, and have a paint shop apply a zinc-rich epoxy primer over a "commercial blast cleaning" SSPC prep. Touch up welds and fasteners with zinc-rich, surface-tolerant epoxy, and field-apply a two-coat urethane.
Proper painting prep is the key to any of these finishes, with professional, commercial grade coatings. Your typical wire-brushing with paint-store metal primer will not yield a very long-life finish. |
Paul Gerber
Senior Member
Username: paulgerber
Post Number: 12
Registered: 04-2010
| | Posted on Thursday, May 13, 2010 - 09:57 am: | |
Typically when we have hot dip galvanized steel that is not being left "raw" we specify a High Performance Polyurethane Coating (our "old school" Section 09964 MF04 09 96 59?). The Product we typically specify is a "Two component, fast drying, aliphatic acrylic polyurethane" including such products as:
Devthane 379 by Devoe High Performance Coatings http://www.duspec.com/DuSpec2/product/ProductDocumentSearchController.htm?documentFormat=pdf&systemSetId=13&productCode=379&documentType=datasheet&submit=Get+Document
or
Pitthane Ultra by PPG http://corporateportal.ppg.com/NR/rdonlyres/2E32B130-8678-43F0-BD10-E6DAB749EFBE/0/pittthaneultra.pdf
Hope this helps!
Ride it like you stole it!!! |
Mark R. Jones, CSI, CCS
Senior Member
Username: mjones
Post Number: 10
Registered: 12-2006
| | Posted on Friday, May 14, 2010 - 01:23 pm: | |
This information is very helpful. Thanks! |
Lisa Goodwin Robbins, RA, CCS, LEED ap
Senior Member
Username: lgoodrob
Post Number: 69
Registered: 08-2004
| | Posted on Monday, May 17, 2010 - 09:56 am: | |
I agree with Bunzick here, as with most painting processes, preparation is of primary importance.
You might also want to contact our local galvanizing expert, Howie Levine FCSI, at Duncan Galvanizing, for general questions about galvanizing processes and various coatings. Howie is on LinkedIn and can be reached by email, galvguy at aol dot com. |
Richard Hird (Unregistered Guest)
Unregistered guest
| | Posted on Saturday, May 29, 2010 - 08:07 am: | |
The best way to prepare galvanized steel or iron for painting is phosphatizing, a shop surface conversion process that provides an excellent base for painting. It is a plant dipping process
Check with your galvanizers about its availbility. We use to use it on galvanized material for industrial process coatings. I seldom see it mentioned in Architectural coatings. |
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