Galvanic corrosion is a type of metal corrosion triggered by the contact of two dissimilar metals. This is one of the reasons you shouldn't repair your metal roof with a different type of metal in case of damage. Here are some tips for preventing galvanic erosion.
Insulate Different Metals
Galvanic corrosion only occurs if two similar metals are in contact with each other. Contact is necessary to facilitate the flow of ions from one metal to another, and the ions can't jump through air or insulation gaps. Take advantage of this fact to prevent galvanic erosion by introducing an insulator, such as a rubber or plastic material, between the dissimilar metals. For example, if you are installing a metal flashing material on a metal roof, and the roof and flashing materials are dissimilar, you can use a rubber seal between the flashing and the roof to prevent galvanic corrosion.
Use Corrosion-Resistant Connectors
If two dissimilar metals have to be joined on the roof, then they should be joined by a material that is corrosion-resistant. That will prevent the spread of corrosion from one side of the joint to another. A common method of joining metal pieces includes making threaded joints (using screws or nuts and bolts), nailing them, or soldering them. In such a case, opt for the method that will introduce the largest piece of corrosion-resistant material between the dissimilar metals. For example, a soldered joint where the solder material is non-corrosive is suitable for this purpose.
Use Protective Coatings
Another nifty trick is to coat the dissimilar materials with protective coatings that will prevent corrosion. The protective coatings work by introducing a thin layer of materials on top of the metal surfaces so that they end up actually not touching each other directly. Even plain old metal paint can provide a protective coating for this purpose, but there are also other forms of corrosion preventive coatings you can use.
Reduce the Surface Area of the Contact Points
The greater the points of contact between the two materials, the more they will exchange ions and the greater the extent of the galvanic corrosion will be. Therefore, it's important to minimize the surface areas of the metals that are actually in contact. Specifically, the less reactive of the two metals should have a small surface area to reduce the rate of galvanic corrosion.
Hopefully, you will be able to stop galvanic corrosion before it begins. Don't despair, however, if the corrosion has already started on your roof; a professional roofing contractor can help you deal with it and prevent further damage. Contact a company like Advanced Roofing and Construction for more information.