The Myth and Reality of “Rust-Proof” Siding
When homeowners choose aluminum siding, they are often drawn to one big promise: it does not rust. But does “rust-proof” mean it is completely immune to the elements forever? The answer is a bit more complex. The core question is whether aluminum siding can still corrode or degrade over time, especially in a challenging Canadian climate with its freeze-thaw cycles, road salt, and humid summers. This guide will explain the science behind why aluminum does not rust, clarify the real threat of corrosion, and provide practical tips on how to protect your siding for the long haul.
The Science Simplified: Rust vs. Corrosion
It is important to understand the difference between the two often-confused terms: rust and corrosion. Rust, or iron oxide, is a very specific type of corrosion that only happens to metals containing iron, like steel. Since aluminum is a non-ferrous metal, meaning it contains no iron, it is physically impossible for it to rust. This is the source of its “rust-proof” reputation, and it is a major advantage over steel siding, which can rust if its protective coating is scratched.
Corrosion, on the other hand, is the general term for the gradual destruction of a metal when it reacts with its environment. Think of it this way: rust is a specific breed of dog, like a Golden Retriever, while corrosion is the entire category of “dogs.” Aluminum has a secret weapon against general corrosion. When it is exposed to oxygen, it instantly forms a very thin, hard, and transparent layer of aluminum oxide on its surface. This layer is incredibly stable and acts as a natural, self-repairing shield that prevents further corrosion.
The Real Threat: When Aluminum’s Shield is Broken
While this natural oxide shield is impressive, it can be damaged. Physical damage from ladders, hail, or a stray hockey puck can scrape away the protective layer, exposing the raw aluminum underneath. The use of abrasive cleaners, like harsh scouring pads, or acidic chemicals, can also strip away this layer. While the oxide layer is strong, prolonged contact with certain environmental elements can weaken it over time, leaving the underlying metal vulnerable to the effects of moisture and oxygen.
When this protective shield is broken and the raw aluminum is exposed, a different kind of corrosion occurs. Instead of the reddish-brown flaking of true rust, exposed aluminum corrodes by forming a white, chalky powder. This is still aluminum oxide, but it is in a thicker, less protective form that can be unsightly. A more insidious form of corrosion is pitting, where small, localized pits or holes can form on the surface. This is often accelerated by the presence of salt and moisture.
Environmental Factors That Accelerate Corrosion in Canada
The Canadian climate presents several unique challenges that can accelerate aluminum corrosion. In many parts of the country, road salt used during the winter is a major catalyst. Salt spray from passing vehicles can coat the siding on your home. If not washed off, these salt deposits can aggressively attack the protective oxide layer and lead to pitting corrosion. This is a significant concern for homes located near busy roads or highways.
High humidity during the summer, especially in coastal regions or near the Great Lakes, also poses a threat. This constant moisture means that siding surfaces stay damp for longer periods. This gives corrosive processes more time to work, especially in shaded areas of your home that do not dry out quickly. Furthermore, in urban or industrial areas, pollutants in the rain can create a more acidic environment. This acid rain can slowly eat away at both the siding’s factory finish and its natural protective layer over time.
Prevention and Maintenance: Keeping Your Siding Strong
The best way to prevent corrosion and keep your aluminum siding looking great is through a simple, gentle cleaning routine. It is a good practice to wash your siding once a year, typically in the spring, to remove the dirt, salt deposits, and pollutants that have accumulated over the winter. A simple and safe solution is to mix a mild, biodegradable detergent, like car wash soap, into a bucket of warm water. Apply it with a soft-bristled brush or a large sponge.
After applying the cleaning solution, it is crucial to rinse the siding thoroughly with clean water from a garden hose. This ensures that no detergent residue is left behind, as this can attract more dirt. It is also a good idea to do an annual walk-around of your property to inspect for any deep scratches or dents. Small scratches can be touched up with a matching paint to seal the aluminum and prevent corrosion from starting. Finally, manage the water flow around your home by keeping your gutters clean and ensuring your downspouts direct water away from the siding.
A Finish That Lasts: The Truth About Aluminum
The final verdict is clear. Aluminum siding does not rust, but it can corrode if its natural, protective layer is damaged and then neglected over time. However, this is not a reason to be concerned; it is a reason to be proactive. A simple, regular cleaning and inspection routine is all that is needed to prevent corrosion and keep your aluminum siding looking great for decades, even in our challenging Canadian climate. By understanding the real threats to your siding and taking these simple, preventative steps, you can ensure your home’s exterior remains a durable, attractive, and low-maintenance shield for years to come.
