Galvanic protection

David Molina
5/7/2012
Hi, I'm considering to install a Galvalume shingles roof but I have a concern regarding to the galvanic protection of galvalume. my house is close to the ocean and the conditions are pretty extreme. According to what I've read the cut edges of aluminum are protected by the sacrifice of the zinc contained in the surface of the galvalume. but when the sheetmetal is pre-painted and then cut as you say in your materials section this chemical reaction doesn't happen and the edges are rusted very severely. Is that right? how do you solve that problem? does the special paint you use allow this reaction? or maybe you just paint one side of the shingles and the reaction still happens underneath? Thanks
Todd Miller
Isaiah Industries, Inc.
5/7/2012
David, these are good questions best answered, really, by the manufacturer of the metal roofing. They will know exactly what their product is comprised of and what steps they have taken for corrosion resistance. One thing I do feel compelled to point out is that galvalume is steel, not aluminum. It is steel coated with a corrosion-resistant metallic coating of aluminum and zinc. Then it is usually painted or clear coated on both sides prior to being formed into roofing. The edges should be cut with a smooth shearing action in order to minimize the exposed edges. Thanks to the zinc in the coating, exposed edges do heal over time for corrosion resistance. You will also want to check with the individual manufacturer in regards to what warranty they offer based upon how close you are to the coastline.
Guest User
5/7/2012
Thanks for your quick answer, Do you know about any manufacturer that could explain to me those details? Thanks
Todd Miller
Isaiah Industries, Inc.
5/7/2012
It would need to be the company that manufactures the product you're having installed. Have you chosen a product or a contractor yet?
Dick Bus
5/8/2012
If you feel you are in an agressive enviornment, I would recommend that you consider zinc or aluminum. These metals will out perform galvalume by a factor of two or more.
Guest User
5/8/2012
It is like 50 miles from the coast so I don't think the environment is that aggressive, an y suggestion for installer and product? Thanks
Eric Novotny
An informed customer is the Best Customer!
5/9/2012
Have them end prime any cuts if you are worried about it.

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