Why Does My Post-Frame Building Rust?


Despite being one of the most common and useful manufactured materials in the world, steel has always had one major flaw…it rusts. Why steel products rust in the first place makes for an interesting topic.


How Does Rust Form?

When any type of steel rusts it undergoes a chemical reaction called corrosion. Rust only forms on the outside of a metal surface because it requires exposure of oxygen and moisture.

For example, if you pour a concrete pad around your building and your sides are emerged in the concrete, corrosion will from two to four times faster than the steel that isn’t exposed to the concrete. This is due to the lack of oxygen surrounding the steel.


How does Galvalume Steel Function Differently Than Galvanized Steel When Resisting Rust?

Galvanized metal is a sheet of steel that has been coated with a thin layer of zinc oxide. The zinc is applied to protect the steel from the elements that can lead to corrosion and rust. This corrosion and rust will eventually weaken the metal and lead to a complete breakdown of the steel. Galvanized metal may begin to breakdown within 10 to 15 years of element exposure.

Galvalume metals are made with steel panels having a coating of corrosion resistant aluminum-zinc alloy applied by a continuous hot dip process. The alloy coating of aluminum and zinc combines the best properties of both metals.

Galvalume is an excellent product for long-life roofing and siding material. The aluminum additive, along with the zinc, allows small particle areas to form within this coating. Any corrosion that occurs does so within these open particle areas. Galvanized metal corrodes in a linear fashion and eventually depletes the zinc coating entirely. Galvalume, on the other hand experiences some corrosion, but on a smaller and less significant scale.


What is FBi’s Solution To Rusted Steel?

FBi uses Galvalume-coated steel for metal-building roofs and siding. Galvalume battles corrosion and rust two to four times longer then galvanized steel that many other builders use. Galvalume is a combination of aluminum, silicon and zinc. This improved coating keeps on fighting corrosion years after “corrosion-resistant “systems. If necessary, we will still use galvanized steel, but if we do, we use a heavier coating so that it will last longer.


What if My Building Has Rust?

If your metal storage building is already showing signs of rust, you can treat the rusted areas by sanding it until the rust is gone and then apply a primer to the spot. Once dry, you can paint over it.

Power-washing your building to remove any dirt or debris will also help with rust prevention.  Just remember, anything that holds water to your steel will likely cause rust.


Resources: Englert Inc., Weatheredge