Cladding / Flashing Galvanic Action
lindenboy
| Posted in Construction Techniques on
When it comes to flashing, whether decks, roofs or otherwise, there are certainly some folks who have more expertise on the matter. A recent thread about decks had some folks explicitly instructing “don’t use [metal x] next to [metal y].”
In some cases the information was inconsistent with research data, and I just happend across an article that may be informative: find attached an article from a recent issue of “The Construction Specifier — June 2009” regarding utilizing dissimilar metals primarily in cladding condition. While not specifically relative to every climate, it may give you some supplemental knowledge about the process and reactions to expect in your construction details.
Cheers!
“It depends on the situation…”
Replies
Thanks. I have that downloading now. Probably worth the time even on my dialup.
but I'm curious about the climate comment. Glavanic reaction is a matter of chemistry, not climate, right?
Other than the fact that the presence of water accelerates the reactions, is there some reason why you think climate would affect galvanic reaction?
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I hope it is worth the time...it's about as small as I could compress it.
The reason climate is an issue, as you will find in the article, is (to paraphrase the author) because the galvanic reaction chart uses saltwater as the source of ionic reaction. Inland water, without the presence of as much salt, will change the results of corrosion between differential metals.
The author suggests that not enough study has been performed in via other means of corrosion (inland water sources) to truly predict the effects in a wide distribution, although that is what people have been doing for years.
I'm just the messenger : ) With today's exterior cladding, it can't hurt to try and understand which metals should and should not be together, although the basis of the chart is probably good enough for most situations. Post your thoughts after you've had time to digest.
"It depends on the situation..."
I do live near the ocean where we refer to the "salt air" and how it degrades some metals. I see from the article that there actually are more ions present near salt water to accelerate corrosion and galvanic reactions, so it is not just the humidity.Also, I have observed in 20+ years of roofing, that certain flashings in places where air pollution and acid rain are a problem see really fast decay set in. Downwind from factory areas is one. 'course this goes back to the late sixties when we were just starting to clean up the environment a bit, but I am sure it is still a factor.On the same subject, the calcium and magnesium salts used on the roads in many states now are far more corrosive to cars and critical components than the old rock salt ever thought of being. It is getting to be standard to see brake lines and fuel lines rotting out in 5-6 years up here. After a thousand dollar repair bill to get my inspection sticker, I bought a presure washer to clean the underbody more often.
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"I bought a presure washer to clean the underbody more often."
Ouch.
Hope he stay's away from the zero degree tip.http://www.quittintime.com/ View Image
Funny , I just came in from sandblasting some rusty old tools I acquired, DW took pics of me in the blast hood, and Pif is speaking of the nuclear bidet.
Would that be marketable as an Enematic
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thats funny!
Could electroplated roofing nails be used to apply aluminum stepflashing on a roof?
yuphttp://www.quittintime.com/ View Image
They will be. And the heads will fall off. The last galvanized flashing I took off had eaten the aluminum windows up.
They will be what?
They will be used for aluminum step. Most roofers use the same nails for everything, even copper.
We don't use step flashing here, everything has to have plastic cement.
I don't really nail the stepflashing in place anyways.The upper leg behind siding sees more nails.If I use a nail,it is at the very edge where it doesn't make any difference.
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