Sometimes you can do everything to protect your metal roof against the corrosion, yet with no success. You use only the quality products, your roof is insulated very properly with the right insulation materials, you use just the right ridge and soffits vents and inpregnate your metal roofing regularly with just the right chemicals. And still, over and over again, you experience some parts of your roof are corroding.
If you found some similarities between the „you“ described above and you personally, you may be a victim of the so called galvanic corrosion.
Galvanic corrosion can develop if you use parts on your roof that are manufactured from different metallic materials, if those parts touch one another.
Actually not all different metals interfere this way, but there are some – often used with metal roofing – that would interfere and sooner or later cause rusting. One of the dissimilar metals always is of more anodic character and the other one is more cathodic. To start the galvanic reaction, presence of electrolytic material is necessary (no problem on the roof, rain water is a great electrolyte).
What are these dissimilar and sooner or later corroded metals?
Well, for example a tinplate or tin-lead (terne) plate roofing may corrode when getting in touch with copper or aluminum. Therefor, you should never use copper gutters, copper snow guards or any aluminum objects touching directly the tin plate roof, if you want to avoid it´s rusting.
I was searching around to get more information on how the dissimilar metals react for you and I happened to visit the MetalMart.com at [http://www.metal-mart.com/Guides/Galvanic.htm]. It is a good source if you are interested in this topic, there´s one very interesting chart with galvanic corrosion potential of the particular metallic materials.
So, if you are the happy owner of continuously corroded roof, don´t hesitate and visit this site too.