Galvanic Corrosion in Metal Roofing and How to Prevent It

What Is Galvanic Corrosion?

Galvanic corrosion, or bimetallic corrosion, happens when two different metals make electrical contact in the presence of an electrolyte like water. This reaction accelerates the deterioration of one metal beyond its usual rate. In metal roofing, galvanic corrosion can cause early material degradation, leaks, and structural vulnerabilities if not effectively controlled.

How Galvanic Corrosion Affects Metal Roofs

Causes of Galvanic Corrosion in Roofing Systems

Metal Pairing Issues – When different types of metal are used together without proper insulation, the less noble metal (the anode) will corrode faster than normal.
Exposure to Moisture – Rain, humidity, and standing water act as electrolytes, accelerating the corrosion process.
Fastener Selection Mistakes – Using incompatible fasteners with metal panels can lead to localized corrosion.
Coastal and Industrial Environments – Salt in coastal areas and airborne chemicals in industrial zones increase the rate of galvanic reactions.

Common Metal Combinations That Cause Corrosion

Aluminum and steel
Copper and zinc-coated steel (galvanized steel)
Stainless steel and aluminum
Brass and aluminum

Preventing Galvanic Corrosion in Metal Roofing

Selecting Compatible Materials

Using metals with similar galvanic properties reduces the likelihood of corrosion. When mixing metals is unavoidable, proper insulation methods should be applied.

Best Practices for Metal Selection:

Use coated metals, such as galvanized or anodized steel, to minimize direct metal-to-metal contact.
Choose roofing fasteners made of the same metal as the panels to avoid galvanic reactions.
Avoid direct contact between aluminum and copper, as their differing electrochemical properties make corrosion highly likely.

Installing Protective Barriers

Applying non-conductive materials between dissimilar metals prevents direct electrical contact, reducing the risk of corrosion.

Common Barrier Solutions:

Rubber or Plastic Washers – Placed between metal panels and fasteners to isolate them.
Sealants and Coatings – Protective coatings like epoxy or polymer layers act as insulating barriers.
Dielectric Grease – Used in fasteners and connection points to prevent conductive pathways for moisture.

Controlling Moisture Exposure

Since water accelerates galvanic corrosion, effective moisture control strategies are essential for long-term roof performance.

Ways to Reduce Moisture Accumulation:

Ensure proper roof slope and drainage to prevent standing water.
Maintain gutters and downspouts to direct water away from roof seams.
Use ventilation systems to minimize condensation buildup in attic spaces.

Choosing the Right Fasteners

Fasteners must be made from corrosion-resistant materials compatible with the metal roof panels.

Recommended Fastener Options:

Stainless Steel Fasteners – Suitable for aluminum and steel roofs.
Aluminum Fasteners – Ideal for aluminum panels but should not be used with steel.
Zinc-Coated Fasteners – Effective when used with galvanized steel roofing systems.

Regular Roof Maintenance and Inspections

Routine inspections help detect early signs of galvanic corrosion before they cause significant damage.

Inspection Checklist:

Check fasteners for rust or discoloration.
Inspect seams where different metals meet.
Look for paint or coating failures exposing bare metal.
Ensure proper drainage to avoid prolonged moisture contact.

The Role of Protective Coatings in Corrosion Prevention

Applying protective coatings to metal roofing extends its lifespan by shielding it from environmental factors.

Common Types of Coatings:

Galvanization – A zinc coating applied to steel to prevent corrosion.
Powder Coating – A durable, painted finish that provides extra protection.
Acrylic or Silicone Roof Coatings – Ideal for sealing seams and reducing water penetration.

Why Proper Installation Matters

Improper installation increases the risk of galvanic corrosion, making it essential to work with experienced roofing professionals. Roofing contractors should:

Use compatible metal materials throughout the roofing system.
Apply sealants and barriers correctly at metal intersections.
Conduct post-installation inspections to ensure all protective measures are in place.

Working with a Trusted Roofing Contractor

For homeowners and business owners in Midlothian, TX, Vera Roofing And Construction provides expert metal roofing services, including corrosion prevention strategies. As a GAF Master Elite Contractor and Firestone/Elevate Licensed Contractor for Commercial Roofs, the company ensures high-quality installations and long-term durability. With an A+ BBB rating and partnerships with leading brands like Owens Corning, CertainTeed, Atlas, IKO, Firestone/Elevate, Mulehide, and F Wave, Vera Roofing And Construction is committed to providing superior roofing solutions with integrity and expertise.

FAQs

1. Can galvanic corrosion be reversed?

No, once corrosion has occurred, the affected metal must be replaced or repaired. Prevention is the best strategy.

2. How long does a metal roof last with proper corrosion prevention?

A well-maintained metal roof can last 40–70 years, depending on the material and environment.

3. What are the first signs of galvanic corrosion?

Early signs include discoloration, rust spots, pitting, and weakened fasteners.

4. Can I mix different metals on my roof if I use a coating?

While coatings help, it is still best to avoid mixing incompatible metals. If mixing is necessary, proper insulation methods should be used.

5. Does saltwater exposure increase the risk of galvanic corrosion?

Yes, coastal environments accelerate galvanic reactions due to the presence of salt, which acts as an electrolyte.

Conclusion

Preventing galvanic corrosion in metal roofing requires careful material selection, protective barriers, proper drainage, and routine maintenance. Working with an experienced contractor ensures that roofing materials remain durable and resistant to environmental factors. Implementing these strategies prolongs roof lifespan and protects against costly repairs.