What is Corten Steel?

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What Is Corten Steel?


Corten Steel, also known as weathered steel, is a type of steel alloy commonly used in outdoor construction. It was created to eliminate the need for painting, and when exposed to the elements outdoors, it develops a rusted appearance within a few months.

What is corten steel?

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Corten steel, also known as weathering steel, is a type of steel designed to resist corrosion and maintain its tensile strength. The name COR-TEN reflects its key features: corrosion resistance and steel strength.

This alloy was developed to reduce the need for primers, paints, and coatings on steel, saving both time and costs. When exposed to the elements, corten steel forms a protective layer called patina, which prevents rusting and corrosion over time.

Due to its unique composition, corten steel is well-suited for various applications like bridges, railcars, outdoor sculptures, panels, and installations.

Is it true that Corten Steel is owned by U.S. Steel?

Corten Steel was actually developed by the United States Steel Corporation (USS) in the 1930s. It was initially created for use in railroad coal wagons due to its durability.

Over time, Corten Steel gained popularity as a material for outdoor art projects, particularly during the 1960s. In the United States, you can still find early examples of Corten Steel structures showcasing its unique aesthetic and durability.


Is Corten Steel still around? Can you actually buy Corten Steel?

a06 4 flat sheets building

While U.S. Steel does hold the registered trademark for the name COR-TEN, the actual product is not currently available under that name. U.S. Steel sold its discrete plate business to International Steel Group, and now it sells branded material in strip-mill plate and sheet forms. Therefore, COR-TEN is not available for purchase.

However, steel with similar properties and finishes is available under ASTM standards such as A606-4, A588, and A847. When someone refers to COR-TEN, they are typically talking about steel that meets these ASTM standards, not the specific COR-TEN brand. So, if you’re looking for COR-TEN-like steel, you would inquire about A606 Type 4, A588, or A847 steel products.

What is A606-4, A588, A847? What can I purchase and what can I use this material for?

Corten Steel, also known as weathering steel, was indeed developed by U.S. Steel in the 1930s. It was originally designed for railroad coal wagons and later gained popularity in outdoor art projects during the 1960s. However, U.S. Steel sold its discrete plate business, including the COR-TEN brand, to International Steel Group. While U.S. Steel still sells branded material in strip-mill plate and sheet forms, COR-TEN is not currently available for purchase. Instead, you can find steel with similar properties under ASTM standards such as A606-4, A588, and A847.

standing seam a606 corten

Regarding A606-4, A588, and A847:

  1. A606-4: This steel is available in metal roofing/siding panels, standing seam panels, flat sheets, and coil form. It provides a rustic look and has superior corrosion resistance.
  2. A588 (COR-TEN “B”): This is typically used for heavier gauge plates compared to A606.
  3. A847: Used for pipe and tube applications.

All these alloys exhibit superior corrosion resistance compared to regular carbon steel, forming a protective oxide film on the surface that slows down future corrosion. They are commonly used in various construction applications where weather resistance is required, such as outdoor structures, architectural elements, and metal roofing/siding.

I understand they use Corten for sculptures and structures, a very natural outdoor selection. Are there any disadvantages to Corten or Weathered Steel?

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Absolutely, like any material, Corten or weathered steel has its pros and cons. Here are some disadvantages to consider:

  1. Welding Challenges: Welding weathering steel requires special techniques as the weld-points weather at the same rate as the rest of the material. Specialized welding procedures and materials may be necessary.
  2. Potential for Corrosion: While Corten steel is highly resistant to atmospheric corrosion, it’s not entirely rustproof. Accumulation of water in certain areas without proper drainage can lead to higher corrosion rates in those spots.

However, with proper care and attention to these challenges, Corten steel remains a popular and durable choice for outdoor sculptures and structures. Its natural weathering properties and resistance to atmospheric corrosion make it an attractive option for builders looking for a distinctive aesthetic coupled with durability.

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