Galvanic Corrosion FAQ's

What is galvanic corrosion? Galvanic corrosion is a process in which two metals are touching electrochemically in the presence of an electrolyte, causing one of the metals (the anode) to corrode faster than it would alone, and the other metal (the cathode) to corrode much slower.

Why does galvanic corrosion occur? The presence of an electrolyte allows a conductive path between the two metals, passing an ion from the anode to the cathode, making the anode much more receptive to rust. Galvanic corrosion can also form on a single type of metal when an electrolyte is heavily concentrated in one area of the metal.

What are some factors that can influence the formation of galvanic corrosion?

• The greater the electrical contact between the two metals, the greater risk of galvanic corrosion
• Higher temperature and humidity tend to make steels less resistant to the electrolytes that cause galvanic corrosion
• The size of the anode relative to the cathode. The larger the anode relative to the cathode, the lesser the corrosion. Conversely, a small anode and a large cathode will produce an anode with more corrosion.

How can you avoid the formation of galvanic corrosion? When two metals are in close proximity, you must separate them electrically in order to prevent the ion migration from one metal to the other. This can be accomplished by one of the following methods:

• Separate the metals with plastic or another good insulator.
• Separate the metals by using a layer of grease.
• Electroplating with more noble metals that resist corrosion (gold, silver, nickel, and chrome)
• Protect the metals by using another metal as a sacrificial cathode. For this method, you can use zinc, magnesium, or aluminum.
• Run an electrical power supply to go against the ionic current that causes the galvanic corrosion.