Weathering Steel: What is it?

Weathering steel, commonly referred to as A606 steel, has recently gained popularity in the architectural world for its distinctive orange-brown oxide (or rust) finish. This layer of rust aids in the resistance to corrosive elements. When weathering steel is produced, it is not rusted. It gradually develops the rust-like appearance as it is exposed to the elements over time.

But, how does it develop the layer of rust and how does that actually aid in corrosion resistance? Let’s find out!

How Weathering Steel Works

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Unlike most corrosion resistant steels that resist rust, weathering steel does rust. However, it only rusts on the outer layer and will not penetrate into the steel once the initial layer has formed. With weathering steel, the layer of rust acts as a barrier to protect the steel from corrosion, whereas with other metals the rust is porous and breaks off allowing another layer to form. The specific alloying elements in the steel produce a stable layer of rust that adheres to the base metal and isn’t as porous as typical rust.

Benefits of Weathering Steel

Weathering steel has many benefits, which make it ideal for architecture.

  • Resists further rusting and staining
  • A high strength low alloy steel (HSLA)
  • Heat and corrosion resistant
  • Ease of formability
  • Low maintenance
  • Long-term performance
  • Environmentally friendly and can be recycled

What is Weathering Steel Used For?

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Because it is corrosion resistant, weathering style is frequently used for exposed structures. These can include bridges, building siding and roofing panels, truck and bus frames, as well as metal sculptures. It was initially used in the 1930s for ore wagons to help them resist corrosion. With its unique finish, it also eliminates the need for repainting or recoating of the steel.

There are elements that weathering steel can’t withstand, however. It shouldn’t be used for applications that will be exposed to chlorine. Chlorine will cause the rusted surface to corrode and can lead to premature failure of the material.

At OFR Metals we stock A606 Type 4 in coil and sheet. For more information on product availability, contact your local sales representative as it may very between branches