Galvanic Corrosion

Galvanic corrosion occurs when two dissimilar metals come into electrical contact in the presence of an electrolyte (like moisture or saltwater). The more anodic metal corrodes while the more cathodic metal remains protected. Below are common metals and how they behave in galvanic pairs:

1. Zinc: Highly anodic — corrodes rapidly when in contact with stainless steel, copper, or brass.
2. Aluminum: Anodic — vulnerable when paired with more noble metals like copper or stainless steel.
3. Carbon Steel / Low-Alloy Steel: Moderately active — can corrode when coupled with cathodic metals such as bronze or stainless steel.
4. Copper: Cathodic — promotes corrosion in less noble metals like zinc, aluminum, or galvanized steel.
5. Brass & Bronze: Cathodic — often causes corrosion in aluminum and steel when in direct contact.
6. Stainless Steel: Highly cathodic — accelerates corrosion of adjacent anodic metals like zinc or aluminum.

Galvanic Series: This electrochemical ranking lists metals from most anodic (active) to most cathodic (noble). The further apart two metals are in the series, the higher the risk of galvanic corrosion when they touch.

Prevention Tips:

• Isolate dissimilar metals: Use gaskets, bushings, or non-conductive barriers to break electrical contact.
• Apply surface protection: Use protective coatings to shield one or both metals from electrolyte exposure.
• Select compatible materials: Choose metals that are close together on the galvanic series to minimize potential difference.

Knowing how different metals interact can help you prevent galvanic corrosion and extend the life of your equipment.

When dissimilar metals are used together in moist or corrosive environments, galvanic corrosion can occur — where the more anodic metal corrodes faster. To prevent this, avoid pairing metals that are far apart in the galvanic series. Some examples include:

1. Aluminum + Copper: Aluminum corrodes quickly when in contact with copper, especially in humid or wet conditions.
2. Zinc + Steel (Stainless or Galvanized): Zinc, being more anodic, sacrifices itself when paired with these steels, leading to rapid breakdown.
3. Steel + Brass/Bronze: Standard carbon steel corrodes when joined with cathodic metals like brass or bronze.
4. Magnesium + Any Metal: Magnesium is extremely anodic and reacts with nearly all common engineering metals, including steel, copper, and aluminum.
5. Carbon Steel + Stainless Steel: When in contact, the carbon steel becomes the sacrificial anode and can degrade quickly without proper insulation.

How to prevent galvanic corrosion between metals:

• Use insulating materials: Plastic, rubber, or composite barriers can block electrical conductivity between metals.
• Apply protective coatings: Surface treatments prevent direct contact and exposure to electrolytes.
• Select compatible metals: Choose metals closer together on the galvanic series to reduce corrosion risk.

Thoughtful material pairing and proper separation techniques are essential for avoiding premature corrosion and extending equipment life.

To prevent galvanic corrosion, engineers must break the electrochemical link between dissimilar metals that are exposed to an electrolyte, such as moisture, saltwater, or condensation. Common strategies include:

• Choose similar metals: Select materials that are close together in the galvanic series to minimize potential differences.
• Add electrical insulation: Use non-conductive washers, bushings, or gaskets to block direct contact.
• Apply protective coatings: Barrier coatings, such as Thin Dense Chrome (TDC), isolate metal surfaces from electrolytes.
• Control the environment: Improve drainage, reduce humidity, seal joints, or use corrosion inhibitors.
• Use sacrificial anodes: In marine or buried systems, a more reactive metal like zinc can corrode in place of the protected part.

For more on how galvanic corrosion starts and how to stop it, see our blog post Understanding Galvanic Corrosion: Causes, Prevention, and Solutions.