Why Certain Metals Can Cause Your COLORBOND® Roof to Rust
COLORBOND® steel is renowned for its durability and resistance to corrosion, thanks to its protective coating of zinc and aluminum. However, certain metals can still cause your COLORBOND® roof to rust if they come into contact with it. Understanding why this happens and how to prevent it is crucial for maintaining the longevity of your roof.
The Science Behind Rust
Rust is a form of corrosion that occurs when iron reacts with oxygen and moisture. This reaction, known as oxidation, leads to the formation of iron oxide, commonly known as rust. While COLORBOND® steel is designed to resist rust, certain conditions and interactions with other metals can compromise its protective coating.
Galvanic Corrosion
One of the primary reasons certain metals cause rust on COLORBOND® roofs is galvanic corrosion. This occurs when two dissimilar metals come into electrical contact in the presence of an electrolyte, such as water. The less noble metal (anode) corrodes faster than it would alone, while the more noble metal (cathode) corrodes slower.
Metals to Avoid
- Copper: Copper is highly conductive and can cause significant galvanic corrosion when in contact with COLORBOND® steel. Water runoff from copper pipes or fittings can accelerate the corrosion process.
- Lead: Lead flashing or any lead-based materials should be avoided. When water flows from lead onto COLORBOND® steel, it can cause rapid corrosion.
- Stainless Steel: Although stainless steel is resistant to corrosion, it can still cause galvanic corrosion when in contact with COLORBOND® steel, especially if the stainless steel contains copper.
Preventing Rust
To prevent rust on your COLORBOND® roof, consider the following best practices:
- Isolation: Use non-conductive barriers or coatings to separate dissimilar metals. For example, rubber or plastic washers can be used with screws and fasteners.
- Proper Drainage: Ensure that water runoff from incompatible metals does not flow onto COLORBOND® steel surfaces. This can be achieved by designing the roof to direct water away from sensitive areas.
- Compatible Fasteners: Use fasteners made from materials that are compatible with COLORBOND® steel, such as zinc-coated steel or aluminum.
- Regular Maintenance: Regularly inspect your roof for signs of corrosion or damage. Early detection and treatment can prevent more significant issues down the line.
Conclusion
While COLORBOND® steel is designed to be highly resistant to rust, interactions with certain metals can still cause corrosion. By understanding the causes of galvanic corrosion and taking preventive measures, you can ensure the longevity and durability of your COLORBOND® roof.
For more detailed information, you can refer to the BlueScope Steel guide on avoiding incompatible metals and the Corrosion Technical Bulletin CTB 12.
If you have any specific questions or need further assistance with your roofing project, feel free to ask!
Dissimilar Metals Colorbond Roofs