How to Weld Weathering Corten Steel?

Weathering steel belongs to the group of low carbon steels. The alloy elements like copper, chromium, silicon and phosphorous in these steels are mixed with carbon and iron atoms. 

Let’s tell you more about what is weathering steel and how you can use it in welding.

Weathering steel refers to a type of steel alloy with superior yield strength capability. Its chemical composition makes it highly resistant to corrosion caused by weather and atmospheric conditions such as air and moisture. It develops a paint-like, protective oxide layer (iron oxide or rust) called ‘patina’ on its surface which makes it corrosion-resistant. It will form rust only on the outer surface. This surface layer doesn’t allow the rust to penetrate deeper into the weathering steel and thereby, protects against corrosion.

Weathering steel is also known as corten steel. It was registered under the trademark Cor-Ten which was originally developed and patented by U.S. Steel in 1933. Cor-Ten gets its name from two words – CORrosion Resistance and TENsile Strength. However, the American Society for Testing and Materials (ASTM) standardised it as a product later.

Corten Steel Uses and Applications

Corten steel is used for both practical and visual appeal reason in the following applications:

• Engineering projects

• Architectural projects

• Construction of buildings and bridges

• Outdoor sculptures

• Marine transportation

• Roofs and walls

• Cycle hoops

• Planters

• Tree grilles

Corten Steel Texture

The texture of corten steel is rusty with an orangish-brown shade. Due to corten steel texture seamless, it often gives an aesthetic finish to the product or application wherever it is used. Welders can apply it seamlessly without worrying about mixing the right proportions of various chemicals to get a rusty appearance.

Corten Steel Properties

Corten steel has the following properties:

• Anti-corrosive

• Robust metal

• Ductile

• High structural strength

• Lightweight

• Attractive appearance

• Minimal upkeep

Corten Steel Specification

The primary trademark product is COR-TEN. However, ASTM has also laid down specifications as under:

• A588 (structural weathering steel panels, shapes, plates and bar)

• A242 (steel plate through 1.5 inches in thickness)

• A606-4 (corten steel sheet and coil)

• A847 (tube and pipe)

• A871-65 (steel plate with a minimum yield strength of 65ksi)

• A709-50W (steel plate for construction of bridges)

The weathering steel grades are available as corten A and corten B. For example, A242 is corten A and A588 is corten B.

Corten Steel Prices

Corten is an expensive metal as compared to other grades of steel. It comes in different grades, properties and specifications. Hence, the prices vary from one weathering steel manufacturer to another. 

Welding on steel that is corten is relatively as similar as low carbon steel. The only precaution the welders need to take is regarding the filler or electrode which is different from mild steel. When it comes to choosing a welding electrode for weathering steel, AWS E7018 is most suitable. The choice of electrode depends on two factors - required strength and code requirements.

Corten steel has been the most widely-used metal for decades owing to its look and benefits. It overcomes rust, which is the major drawback associated with steel. The necessary expertise and experience in welding already exist. Hence, welders should be able to use it without any hassles.