The Hidden Enemy: Understanding Galvanic Corrosion

The Hidden Enemy: Understanding Galvanic Corrosion

Galvanic corrosion occurs when two different metals are in electrical contact in the presence of an electrolyte (like water). Here’s a deeper dive into this issue:

How It Happens:

1. Electrochemical Reaction: When two dissimilar metals are in contact, one metal (the anode) will corrode faster than the other (the cathode). The metal that corrodes is typically less noble (more reactive) than the other.
2. Electrolyte Presence: An electrolyte, such as saltwater or moisture, facilitates the electrochemical reaction. Even small amounts of moisture can initiate this process.

Common Pairings that Cause Problems:

1. Aluminum and Copper: When aluminum (more reactive) is in contact with copper (less reactive), the aluminum will corrode quickly.
2. Zinc and Steel: If zinc (used for galvanizing) is in contact with steel, the zinc will corrode to protect the steel. However, if the zinc coating is damaged, the exposed steel can corrode rapidly.

Signs of Galvanic Corrosion:

1. Pitting or Erosion: Visible pits or eroded areas on the more reactive metal.
2. Color Changes: Discoloration around the contact points of the metals.
3. Loss of Material: Reduced thickness or structural integrity over time.

Prevention Strategies:

1. Insulation: Use non-conductive materials (like rubber or plastic) to separate dissimilar metals.
2. Coatings: Apply protective coatings (paint, galvanization) to prevent contact with electrolytes.
3. Electrolyte Control: Keep the environment dry or minimize exposure to moisture.
4. Proper Material Selection: Choose metals that are compatible or have similar electrochemical potentials for applications.



Considerations:

1. Galvanic corrosion can significantly affect the lifespan and integrity of metal structures, especially in marine or humid environments. It's essential to understand the metals being used in conjunction and take preventive measures to avoid costly repairs or replacements.