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topic 7757

Galvanized Steel Roof and Paint Adherence Problem


(2001)

I would like to know why the paint on a recently painted roof is peeling. The roof covering was galvanized steel. Since its first construction there have been several coats of paint applied to it. After a recent application the paint started to lift. The lifting was at the base coat level which apparently had been an oil based paint. The recently applied coat sticks quite well to the coat onto which it was applied. It was also noted that the paint lifted more on a southern exposure. (The roof in question is in the northern hemisphere.)

There has been a suggestion that there may have been a reaction with the original oil base paint and the roof, and that the application of successive coats put stresses on this coat which then eventually peeled. Is this possible? Other possibilities?

Peter Zubrzycki
- Boischatel, Quebec, Canada


(2001)

Galvanize sheets, for roofing or siding, may be chemically treated to resist rust or oxidation. This protection is required for the bundles of steel, while they are in storage or during transportation. Galvanize sheets, in bundles, may rust very easily. Normally, you will not see this surface treatment. You may ask your vendor. Are these sheets hot dip galvanize, chemically treated, with no oil ?

This chemical treatment is temporary. It will gradually disappear. You may discover that paint will adhere to your "new" roof; after it has been given time to "weather".

Galvanize sheets for painted applications are usually manufactured with no chemical treatment. Usually, they are produced "dry". Although, they may be lightly oiled, if the paint, pretreatment can adequately remove the oil.

Good Luck,

Terry T. Magyar
Berwick Steel Co. - Columbus, Ohio, USA


(2004)

I have 6000 sq. ft of galvanized/corrugated steel roof on my new island style home. It is too bright and I would like to do a copper paint and patina finish. Any recommendations?

Loren Nancarrow
TV weatherman/ homeowner - Rancho Santa Fe, California, USA


(2005)

I will suggest you contact either Modern Options [linked by editor to product info] or Star Scenic Supplies of Orlando for starters. I would call the company that supplied your roofing to see if you will need to prep the galvalum to rough-up the surface if the roof is new as there sometimes is a temporary coating on galvalum used to protect while in storage and shipping. Benjamin Moore has lots of surface paint coverings available as well. Metal Masters or Modern Options^Triangle Coatings will even supply you with videos on how to apply their coatings. There is an actual real copper containing paint that goes on first followed by a fast oxidizer that works great.

I am an artist that uses a lot of these types of painting techniques.

Hopes this helps.

Patricia Moo
- Deland, Florida

----
Ed. note, Oct. 2011:
We believe that "Modern Options" is now "Triangle Coatings".


October 5, 2011

You can check at Industrial Metal Supply, Ruffin Rd. San Diego. They have the supplies videos and sometimes offer free classes on painted metal finishes ie. Copper, patina, bronze, etc. They also might be able to refer you locally.

Jayne Castillanes
- Olivenhain, California



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