How to Prevent Galvanic Action in Metal Roofs

Galvanic corrosion occurs when two dissimilar metals are placed in electrical contact with each other in the presence of an electrolyte. When these two metals are in contact with each other, the more anodic metal will corrode, whereas the more cathodic metal will be protected from corrosion. Galvanic corrosion will only occur when the difference in anodic index between the two metals is greater than 0.15 volts; it is therefore important to determine which metals can be used together to prevent either metal from suffering the effects of galvanic corrosion.

Table of roofing metal materials
Anodic index table

Instructions

- 1
  Determine the material you wish to use for your roof. Find the anodic index for that material on the anodic index table.
- 2
  Check the anodic index table to determine what metal fasteners may be used with the roofing material. The fasteners must be made of a material that has an anodic index of fewer than 0.15 volts difference from the anodic index of your roofing material.
- 3
  Choose fasteners that are able to be used with your roofing material. For example, if you are installing a galvanized steel roof (anodic index of 1.20 volts), you may use zinc-plated (anodic index 1.25 volts) or galvanized steel (anodic index 1.20 volts) nails or screws to attach the roof to the building.

What Happens if Porcelain Tile Adhesive Freezes?

How to Lay Masonry Siding

Exterior Remodeling