Advanced Metal Knowledge

Corten vs Weathering Steel

Corten steel is often associated with its weathering steel properties, but there are different grades within the Corten family. The two most recognized grades used for Corten are Corten A and Corten B. Below, we’ll explore the differences between these two grades.

Understanding Corten Steel Grades – Corten A vs. Corten B

Selecting the right grade of Corten steel is crucial when working with this material, as it can impact the final appearance and performance of your project.

Corten A, with a higher phosphorus content, is commonly used in architectural and aesthetic applications, such as building facades, sculptures, and indeed, planter edging.

Corten B, which has higher strength and is less focused on phosphorus, is more often applied in industrial and structural settings, including shipping containers, railway cars, and load-bearing structures like bridges and retaining walls.

Explore other common architectural steel finishes here.

Corten A:

Chemical Composition: Corten A is primarily composed of iron, with small amounts of copper, chromium, nickel, and phosphorus. The presence of these alloying elements enhances the steel’s resistance to atmospheric corrosion.
Weathering Properties: Corten A is known for its excellent weathering properties. When exposed to the elements, it develops a protective layer of rust on the surface, which not only prevents further corrosion but also gives the steel its distinctive reddish-brown appearance. This patina acts as a barrier against atmospheric corrosion and can extend the material’s lifespan.
Applications: Corten A is commonly used in architectural applications, outdoor sculptures, cladding, and structural components. Its aesthetic appeal, combined with its corrosion resistance, makes it a popular choice for outdoor and exposed environments.

Corten B:

Chemical Composition: Corten B has a slightly different chemical composition compared to Corten A. It contains small amounts of copper, chromium, nickel, and phosphorus, similar to Corten A. However, Corten B has a higher phosphorus content.
Weathering Properties: Corten B shares the same weathering characteristics as Corten A. It forms a protective rust layer when exposed to the elements, which provides corrosion resistance and a unique appearance.
Applications: Corten B is used in similar applications as Corten A, particularly in structural and architectural projects. The choice between Corten A and Corten B may depend on factors such as availability, project requirements, and design preferences.

In summary, both Corten A and Corten B are excellent choices for projects requiring weathering steel properties and a distinctive appearance.

For planter edging and architectural uses, Corten A is most suited as it develops a stable rust-like appearance that enhances aesthetic appeal while offering long-lasting durability and low maintenance in outdoor environments.