Galvanic corrosion is typically caused when two dissimilar metals are improperly coupled together in a corrosive environment. This common problem is seen in almost every structure, including commercial facades.
Galvanic corrosion is caused by an electrochemical reaction between different classifications of metals rubbing against each other in wet or grimy conditions. This type of corrosion commonly occurs between aluminum and cast iron; copper and steel; and stainless steel and aluminum.
“Galvanic corrosion, which generally appears as clusters of chalky, thick mineral deposits that may turn rusty orange, typically remains hidden on a building until there is an interior water leak that needs investigating,” says Rod O’Bannon, Manager of Western Specialty Contractor’s Sheet Metal Division in Kansas City, MO. “We typically see galvanic corrosion under a parapet cap or behind a panel system when galvanized metal or screws are used to install aluminum or stainless steel. Galvanic corrosion can cause water infiltration of the building envelope which could lead to mold.”
O’Bannon recommends that property managers conduct a yearly inspection of a building’s roof and façade with an experienced specialty contractor to identify and address issues such as galvanic corrosion before they turn into major problems requiring expensive repairs.
One way to avoid galvanic corrosion is by using a single metal type throughout a project, but that may not always be practical due to a metal’s availability or specific properties. When galvanic corrosion is identified, the specialty contractor may recommend placing electrically inert spacer materials such as rubber, plastic, nylon or neoprene between the two metals to separate them, or to isolate the dissimilar metals from moisture using specialized coatings such as bituminous paint.
“Using stainless fasteners when doing metal installations is also an option to prevent galvanic corrosion,” says O’Bannon.
For more information about galvanic corrosion, contact the Western Specialty Contractors branch location nearest you.