COR-TEN® is the trademarked brand for weathering steel developed by US Steel and licensed to manufacturers like SSAB. While generic weathering steels exist, Ironbound supplies authentic SSAB COR-TEN® to ensure consistency in metallurgy, ASTM A606-4 compliance, and patina development.

Weathering steel was developed in the United States at the beginning of the 20th century when was noticed that steel plate alloyed with copper resisted atmospheric corrosion far better than normal carbon steel plates. Weathering steel was developed as result of long tests 1933. The original chemical composition is Phosphorus 0.07%, Silicon 0.5%, Copper 0.3, Nickel 0.2% and Chromium 0.7%

Weathering steel has traditionally been used for industrial applications. Its popularity has increased over the years and migrated into architectural applications. The natural colour, variation and longevity of weathering steel makes it interesting to the design community.

Weathering steel is characterized by a matte surface, which reduces reflections that are typical of other metals and also reduces any unevenness of the surface .The patina developed over time gives weathering steel a distinguished, brass-like appearance. It is also a long lasting material that can be expected to last up to 100 years inland and up to 60 years in coastal areas.

The oxidation process typically takes 18 to 36 months to reach a stable state. The rate of change depends on local weather conditions and the frequency of wet-dry cycles. The material will transition from an initial orange-to-orange-brown to a final dark-brown, textured protective layer.

Yes. During the initial oxidation phase, iron oxide runoff can stain porous surfaces like concrete, stone, and wood. Ironbound provides technical details for integrated drainage, flashing, and drip-edges to manage runoff and protect adjacent finishes.

The difference is the chemical composition. Weathering steel contains copper, chromium, and nickel alloys that form a dense, protective patina when exposed to the weather. This layer seals the steel and prevents deep-seated corrosion. Mild steel lacks these alloys; it produces a porous rust that traps moisture and leads to continuous oxidation and structural failure.

While it is available it can be quite costly. It is often recommended to spray the sheets with a mixture of peroxide, vinegar and salt. This significantly accelerates the initial stage of patina and reduces the amount of run off.

We stock SSAB COR-TEN® in 22ga, 1mm, 1.5mm, 2mm, and 3mm thicknesses. Standard sheet dimensions are 1500mm width by lengths of 2500mm, 3050mm, 3660mm, and 4500mm.

Yes. We supply weathering steel for custom residential facades as well as commercial and institutional applications.

Panels can be installed using our engineered concealed (System-C) or exposed (System-X) aluminum sub-framing. They are also compatible with standard commercial attachment methods, including Z-girts and hat channels as well as wood.

No. Once the protective patina has formed, the steel is self-healing and zero-maintenance. It does not require painting, clear-coating, or sealing. If the surface is scratched, the exposed steel will re-oxidize and blend into the existing patina.