The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Corrosion of dissimilar metals in the construction industry

 

Please direct me to a good source on corrosion of dissimilar metals in the construction industry. I have recently had copper gutters installed on my home and the were installed with some sort of coated screw not copper and brass as I expected. I remember from high school chemistry that this may lead to accelerated corrosion of the metals. My contractor does not seem to have experience in this area. I would like to find a definitive source on the subject of coated fasteners with the use of copper building materials.

Frank Andryauskas
- Lexington, Massachusetts

---

Copper is more noble than other typical construction materials like steel and aluminum. It will form a 'battery' whereby the copper will be protected while the fastener material will corrode. I'm not sure what the normal construction standards are these days, but if the screws are not copper or brass, I think you need to insulate them from the gutter with rubber or plastic washers.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey