Galvanic Corrosion

April 28, 2015

A galvanic cell is an electrochemical cell that utilizes electrical energy from reactions. Though integral to our daily lives in many ways, galvanic reactions are also the basis of galvanic corrosion, which is one of the most destructive forms of corrosion.

A galvanic cell is an electrochemical cell that harvests electrical energy from electron transfer reactions that occur in the cell. Galvanic reactions are the basis of batteries, which are integral to our everyday lives. Unfortunately, galvanic reactions are also the basis of galvanic corrosion, which is one of the most common and destructive forms of corrosion.

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When salty and moist foods, such as lasagna, are stored in steel pans and covered with aluminum foil, a galvanic “lasagna cell” forms.

Galvanic corrosion occurs when dissimilar metals are coupled in an electrolyte and a galvanic couple forms. One of the metals becomes anodic to the other metal and experiences an increased corrosion rate, while the other metal becomes the cathode and experiences slower corrosion rates than it would all by itself.

Metals can be organized into a list called the galvanic series which determines a metal’s nobility. The galvanic series orders metals based on their electrode potentials, and consequently their susceptibility to galvanic corrosion. When two dissimilar metals are submerged in an electrolyte, the less noble will experience galvanic corrosion.

A well-known example of galvanic corrosion is on the Statue of Liberty. The Statue of Liberty is made of a wrought iron support structure and an outer copper skin. Galvanic corrosion had been anticipated during construction, so an insulating layer was put between the copper and wrought iron to isolate the metals, seemingly preventing corrosion. Unfortunately, this insulating layer degraded and became porous over time. The porous insulation layer harbored moisture and galvanic corrosion ensued.

Galvanic corrosion is not just an issue for structural components. Believe it or not, your food can also be victimized by this form of corrosion. When salty and moist foods, such as lasagna, are stored in steel pans and covered with aluminum foil, a galvanic cell can develop. This “lasagna cell” forms because the aluminum becomes anodic to the steel pan. The moisture in the pan plays the role of an electrolyte and a galvanic cell is created. The aluminum foil can deteriorate, leaving pieces of foil on your food. Yum!

Just like the insulating layer on the State of Liberty was intended to prevent metal-to-metal contact, our ProTek Wear Pads and Flat Plate isolate pipes from contact with other metals. Unlike on the Statue of Liberty, our composite technology is extremely durable and will not degrade over time, effectively preventing your pipes from corroding.

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