Sometimes you just can’t stop your metal roof from rusting (corrosion). Even though you use only the best quality products, your roof is insulated properly with the right insulation materials, you use just the right ridge and soffits vents and impregnate your metal roofing regularly with just the right chemicals, you still have roof corrosion. This problem is usually associated with the dissimilar metal used on the roof. This is also called galvanic corrosion. Here is how to prevent it.

Galvanic corrosion will develop if you use parts on your roof that are manufactured from different metallic materials and if those parts touch one another.

Not all different types of metals react this way, but there are some that are often used with metal roofing that does and sooner or later causes rusting. One of the dissimilar metals always is of more anodic (negative charged) character and the other one is more cathodic (positive charges). To start the galvanic reaction, there must be a presence of electrolytic material. This is usually water from rain or dew. Any kind of water is a great electrolyte. Once the electrolyte material (moisture) comes in contact with two dissimilar metals, an electron transfer will begin to occur which will cause the corrosion.

The most common dissimilar corrosion on metal roofs occurs when a tinplate or tin-lead (terne) plate roofing comes in contact with copper or aluminum. Therefore, you should never use copper gutters, copper snow guards or any aluminum objects that touch directly a tin plate roof if you want to avoid rusting.

To avoid galvanic corrosion completely it is recommended that all the different parts used in metal roofing be the same material. The exception is ice guards that are made from fiberglass or composite material. This will eliminate any chance of unsightly roof corrosion.

See related articles:

Scissor Truss Design

Shelf Making and Installation

Snow Guards for Metal Roofs

Sound Proofing Foam Insulation

Suspended Ceilings

The Pros and Cons of Roofing Materials