Weathering steel or Corten steel

Do You know why this steel has name cor-ten? It represents the material’s two primary properties:  ‘”Cor” – for Corrosion Resistance, while “Ten” for Tensile Strength.

It also known as weathered steel. Steel was created to eliminate the need for painting, and when exposed to the elements, it naturally develops a rusted appearance within a few month. 

Corten weathering steel is a type of steel often used for its superior corrosion resistance to weather conditions. Due to the presence of specific alloying elements, it forms a protective oxide layer that shields the metal from further corrosion. This desirable feature makes corten steel popular in sculptures, fence, bridge construction, and other architectural projects. It differs from other types of steel as it doesn’t require additional corrosion protection, and its welding process is equally efficient.

Corrosion Resistance of Corten Steel:

Corten steel is a group of steel alloysspecifically designed for resistance to atmospheric corrosion.

Its unique chemical composition facilitates after undergoing few series of wet and dry cycles the rich oxygenated layer on the surface, serving as a natural protective barrier. In other words, corten steel rusts and this rust becomes its protective coating. This layer prevents further corrosion, making Corten steel ideal for use in extreme atmospheric conditions. 

That make corten steel a highly desirable type of steel, especially for outdoor spaces. Its weather-resistant properties make it an ideal choice for projects exposed to the elements.

Chemical Composition:

• Cor-ten steel contains copper, chromium, nickel, and phosphorus, crucial for creating a stable oxidized layer on the surface of the steel. If the temperature range is right and moisture is present, the oxide will quickly form. 

These elements give Corten steel distinctive properties in terms of both corrosion resistance and aesthetics.

Unique Color and Texture:

• Over time outdoors, Corten steel develops a characteristic rusty color, giving projects a unique and rustic appearance.
• This aesthetic makes Corten steel popular in projects where a distinctive style and lasting beauty are sought.

Mechanical Durability:

Corten steel is characterized by high mechanical strength, making it ideal for applications in construction where solidity and durability are required.

Resistance to High and Low Temperatures:

This exceptional steel maintains its properties even in extreme temperature conditions, making it a versatile construction material.

Ease of Processing:

• Despite its strength, Corten steel is relatively easy to process, allowing for adaptation to various architectural and artistic projects.

Due to its unique properties, this steel has become not only a practical construction material but also an inspiring design element, bringing modernity and lasting aesthetics to projects. 

How does Corten Steel Weather

The protective layer of Corten continuously develops and regenerates over time, responding to the pollutants present in the atmosphere.

Initial Stage (0 – 3 Months)

Appearance: When newly installed, Corten steel has a smooth, dark steel color similar to other unfinished mild steel surfaces. During the first few weeks to months, it begins to oxidize as it reacts with the moisture and oxygen in the environment.

Process: At this stage, a thin, orange-brown rust layer starts to form on the surface. This is the steel’s initial response to exposure to the elements. During these early months, the rust layer is quite loose and easily flakes off, especially when it rains or if the surface is disturbed. This stage is characterized by the most active and noticeable changes in appearance.

Intermediate Stage (3 – 9 Months)

Appearance: The steel starts to develop a deeper, more uniform rust color, transitioning from the bright orange-brown of the initial stage to a darker, richer brown. The surface appears more matte, with some variation in hue depending on the exposure to weather conditions, such as sunlight, humidity, and rain.

Process: As weathering continues, the surface rust layer gradually stabilizes. The corrosion process creates a dense oxide layer that becomes more compact and adherent to the steel. Rainfall and moisture cause some surface rust to wash away, helping the remaining material form a more protective, stable patina. During this stage, rust runoff, commonly referred to as “bleeding,” can stain nearby surfaces (e.g., concrete or stone). Proper placement and design can help mitigate this effect.

Stabilization Stage (9 – 36 Months)

Appearance: The color continues to deepen, shifting from reddish-brown to a darker brown or even purple-gray tone. By this stage, the rust texture becomes more uniform and less prone to flaking.

Process: The protective layer of rust, now fully stabilized, acts as a barrier that significantly slows down further corrosion. This dense oxide layer reduces the steel’s rate of decay, which is the key feature that makes Corten steel suitable for outdoor use. The time for full stabilization depends on environmental conditions; regions with higher humidity or pollution might accelerate the weathering process, while drier climates may slow it. 

Fully Matured Stage (3 – 10 Years and Beyond)

Appearance: After about 3 to 10 years, the steel reaches its final, fully weathered look. The patina becomes darker, varying between deep brown to purplish-gray hues, with a textured, matte finish. This final color remains relatively stable over time, although slight variations might occur based on ongoing exposure to different environmental factors.

Process: At this mature stage, the rust layer has thickened enough to provide an effective barrier against further corrosion. The steel effectively “self-seals,” preventing deeper rust from affecting the material’s structural integrity. Once stabilized, the weathered surface requires minimal maintenance and can last for decades without significant structural degradation.

Corten steel panel delivery

Delivery of corten steel sheets is typically handled with care to ensure the material arrives in optimal condition. Delivery time may vary depending on the size and complexity of the order.

Corten steel online price

Please contact us today to get a personalized quote for corten steel and find out how we can meet your next project needs!