48605

Copper/Galvalume Roof [Oregon] 

April 24, 2008

I am an architect in Portland, Oregon mounting a photovoltaic array over a Butler Manufacturing, Galvalume Plus roof. A #10 bare copper wire will be used between each frame to serve as a ground. The ground wire will not touch the roof. We are expecting a 40 year life expectancy. Should we be concerned about rain water driping from the copper wire deteriorating the aluminum coating on the steel roof through galvanic action? Can the copper migrate to the roof. Is the possiblity of copper sulfate developing on the wire as it ages and dripping on the roof an "East Coast problem"?

Thank you.

Ernie Munch
Architect - Portland, Oregon, USA

Hi, Ernie. I have never heard of that phrase "East Coast problem" associated with anything like this, but I guess it could be :-)

So I would suggest that you have some picnic lunches at local parks and memorials and see if the concrete plinths below the copper and brass statues have green discoloration on them. Back East they do.

If this was installed on the east coast, I think it would be problematical. The green copper salts do drip, and I'd be reasonably confident that the copper would galvanically attack the aluminum roof. Perhaps you can put a little dilute copper salts on a galvalume panel and salt spray test it?

Ted Mooney, P.E.  finishing.com Brick, NJ