What Is Galvanic Corrosion and How Do Other Metals Affect It?
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When building a structure that will be exposed to moisture—especially in marine environments—durability is everything. You want to eliminate any long-term threats to your structure’s integrity, and that often means considering galvanic corrosion.
In this article, we’ll explore the question ‘What is galvanic corrosion?’ providing a concrete answer that will help you, whether you’re working on a bridge or a new construction project. We’ll also take a closer look at what metals are safe to pair with galvanized pieces and the underlying cause of galvanic corrosion.
What Is Galvanic Corrosion?
This is a corrosive process that occurs when you place two dissimilar metals in electrical contact with each other while an electrolyte, like saltwater, is present. An electrolyte is any mineral that has an electrical charge when it is exposed to water or certain bodily fluids.
One metal will start to corrode — sometimes rapidly — while the other is protected.
This is why galvanic corrosion is a critical facet to consider, especially when working with materials that will be used in a project that is in a marine or high-moisture environment.
What Causes Galvanic Corrosion to Happen?
For galvanic corrosion to happen, the following must occur:
- There must be contact between two dissimilar metals
- An electrolyte must be present
As a result, this creates a circuit where one metal becomes the anode (corrodes) and the other becomes the cathode (protected).
For example, when copper pipes are connected to galvanized steel, water acts as a conductor, creating a circuit that causes the zinc coating on the galvanized steel to corrode.
What Is The Galvanic Series?
This is a chart used by engineers to determine which are “active” metals (that can corrode more easily) or “noble” metals (that resist corrosion). The further apart two metals are on the galvanic series, the higher the risk of corrosion for the more active one.
What Metals Are Safe to Pair With Galvanized Steel?
- Other zinc-coated metals are generally safe to pair with galvanized steel.
- Painted steel (if the steel has a durable, well-maintained coating system)
- Aluminum (However, in highly corrosive environments, it may require electrical isolation.)
Examples of How the Most Common Metal Combinations Interact
- If aluminum and steel are combined, the aluminum will corrode.
- If copper and steel are combined, the steel will corrode.
- If stainless steel and zinc are combined, the zinc will corrode.
What Factors Can Accelerate Galvanic Corrosion?
The following factors can have an impact on galvanic corrosion:
- Exposure to moisture and humidity
- Extensive saltwater exposure
- Temperature and pH levels
- Pollutants that can speed up the corrosion process
- The drainage and ventilation used for the project
What Are the Consequences of Galvanic Corrosion?
If galvanic corrosion occurs, the consequences can be devastating because it can lose structural integrity. Other results of galvanic corrosion include:
- Equipment and machinery malfunction
- Environmental contamination
- Aesthetic deterioration
- Additional maintenance costs
How to Prevent or Minimize Galvanic Corrosion
Fortunately, there are a few basic steps you can take to easily minimize the possibility of galvanic corrosion.
- Choose compatible metals or metals close together on the galvanic series.
- Use insulating materials (non-conductive washers, sleeves).
- Apply protective coatings (paint, galvanization, sealants).
- Use sacrificial anodes in marine or underground applications.
- Design considerations:
- Isolate dissimilar metals
- Minimize contact area
- Allow for drying
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Galvanizing is your first line of defense against the elements. By working with our experienced team, you’ll have high-performance zinc coatings that extend the life of your project, even when it is subjected to the harshest environments.
Learn more about how we can assist with your latest project. Contact us for a quote.
Key Takeaways:
- Galvanic corrosion occurs when two dissimilar metals are in contact in the presence of an electrolyte like water or saltwater.
- One metal corrodes (the anode) while the other is protected (the cathode), often leading to rapid material degradation.
- This form of corrosion is especially important to consider in marine or moisture-rich environments.
- The galvanic series is a tool that ranks metals by how likely they are to corrode, helping guide safe metal pairings.
- Several environmental factors can speed up the corrosion process. These include:
- Humidity
- Saltwater
- Temperature
- pH
- Pollutants
- Consequences of galvanic corrosion can include:
- Structural failure
- Equipment malfunction
- Increased maintenance costs
- Safety hazards
- Good design practices—such as minimizing metal contact and ensuring proper drainage—are key to preventing long-term corrosion damage.
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Sources:
American Galvanizers Association, “Dissimilar Metal Corrosion With Zinc,” https://galvanizeit.org/design-and-fabrication/design-considerations/dissimilar-metals-in-contact
American Galvanizers Association,“In Contact with Other Metals,” https://galvanizeit.org/hot-dip-galvanizing/how-long-does-hdg-last/in-contact-with-other-metals
The Association for Materials Protection and Performance, “Galvanic Corrosion,” https://www.ampp.org/technical-research/impact/corrosion-basics/group-1/galvanic-corrosion
