copper flashing, galvanized nails...

sharp

I just replaced a turne flashing apron with copper. I used copper nails to fasten the copper flashing but would like to know if the roofing nails used to fasten the existing roof asphalt shingles which now sit under the copper may cause any type of oxidation to the copper. I don't think the nails were stainless or aluminum, they should be galvanized, but not sure for certain.

Also, I have aluminum around the chimney, I would like to make a transition from copper to galvanized to sit next to the aluminum on the chimney. Will this work?
Thanks.

echase

If I'm reading my galvanic series chart (see link) correctly copper your copper flashing has potential to eat away zinc (galvanization) and iron (the body of the nails). This is more of an issue when the metals are wet (hopefully they won't be under the flashing). If the nail heads were corroded away the shingles would be more susceptible to blow-off... but at least they won't be eating holes in your flashing!

My comments are strictly theoretical, as I have no experience with the combination you are talking about. My guess is that it will be fine, but you could always put a dab of sealant on the nail-heads, or a layer of 15# felt between them and the flashing if it makes you sleep better.

Hopefully a real roofer will chime in with some more experienced advice.

seeyou

The galvy nails might eventually fail if there is moisture under the flashing. The copper is more noble, so it's unlikely it will be damaged.

As far as the transition from copper to aluminum, aluminum is more noble than zinc, so aluminum touching copper is better than galvanized touching copper. Also, copper downstream from galvanized is not as bad as the inverse.

AaronB

I was about to come in here and see what kind of crap was posted, but its all good... Thumbs up

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sharp

Thanks guys.