How Corten Steel Compares to Traditional Steel

Corten steel, also known as weathering steel, is a specialized group of steel alloys engineered to work well outdoors. Its most notable characteristic is the formation of a protective patina when exposed to atmospheric conditions.

Corten steel was first used for building railroads in the 1930s. Since then this versatile material has been used for numerous architectural and signage projects. Corten is a brand name for corrosion resistant products developed by United States Steel (USS). Other steel producers – such as Nippon Steel in Japan – have also been licensed to produce Corten.

In this article we’re going to take a look at how Corten steel compares to traditional steel. We’ll look at their properties, how they’re made, and what it takes to maintain them. If you’re deciding between these materials for a new sign or thinking about upgrading your current structures, this guide will help you choose the best option.

Weathering steels are special metals that protect themselves from rust by forming a natural protective layer on their surface. Unlike regular steel, this protective “skin” helps them last much longer by slowing down the rusting process.  This natural aging process sets it apart from traditional steel, which often requires frequent painting or replacement to maintain its look and strength.

One common type, A606-4, is popular for roofing panels and siding, especially when creating a rustic look. While it costs more than regular steel, its superior durability makes it a worthwhile investment for many construction projects.

Corten steel has a unique chemical composition, incorporating specific amounts of copper, chromium, and nickel. These alloying elements contribute to the formation of a stable oxide layer, primarily composed of iron oxides, which acts as a barrier against further corrosion.

One of Corten steel’s advantages is its self-healing property. If the protective layer sustains damage, it will regenerate over time, ensuring continuous protection without the need for regular maintenance or protective coatings.

It also has improved tensile strength, i.e., resistance to breaking under tension, and can lead to significant cost savings over time due to reduced maintenance needs. 

These advantages have made the material increasingly popular in architecture and signage projects. They also gave the product its name – ‘Cor’ for its corrosion resistance, and ‘ten’ for its tensile strength.

Common uses of Corten steel

Corten steel’s unique blend of durability and visual appeal makes it a versatile material for various applications:

• Architecture: It’s often used for building facades and cladding, creating striking exteriors that evolve over time. Artists and designers favor it for outdoor sculptures and installations, considering how it interacts with the environment.
• Structural projects: Engineers use Corten steel in bridge construction and other structural projects, benefiting from its strength and corrosion resistance. 
• Landscaping: Here, Corten steel is used in planters, retaining walls, and decorative elements, complementing natural settings.
• Industrial applications: The material is often used for containers and storage units. 

However, perhaps the most relevant application is Corten steel’s increasing popularity in the signage industry. It offers a perfect combination of longevity and visual interest for outdoor signs and wayfinding structures.

Corten steel’s unique properties

At its core, Corten steel contains small but crucial amounts of copper, chromium, nickel, and phosphorus.

There are two main types of Corten steel: Corten A and Corten B. Here’s the difference:

Copper plays an important role in Corten’s corrosion resistance. As the steel weathers, copper compounds form within the patina, creating a barrier that slows down further corrosion. This process not only protects the steel but also produces the rich, earthy tones that make Corten signage so visually appealing.

When compared to standard steel used in signage, Corten’s corrosion resistance is impressive. Corten steel can maintain its integrity for 40 years or more with very little maintenance.

According to relevant ASTM standards (ASTM A588 for Corten B and ASTM A242 for Corten A), these alloys are carefully controlled for composition and performance, ensuring quality and consistency in signage and architectural applications.

Corten steel’s weathering and patina formation process

This process begins with the oxidation of the alloying elements, particularly copper, chromium, and nickel, as they react with oxygen and moisture in the air. Over time, this patina becomes denser, effectively sealing the surface and preventing further corrosion.

Environmental factors like humidity, temperature, and air pollution can influence how quickly the patina develops. In humid or coastal areas, for example, the patina may form faster, while dry climates slow the process. Typically, Corten steel takes about 6 months to 2 years to fully stabilize, depending on the conditions. During this time, the appearance of the steel will change, transitioning from a bright, rusty orange to a deeper, more subdued brown.

Maintenance is generally minimal, but during the early stages, it’s important to manage any runoff from the steel, as it can stain nearby surfaces until the patina fully develops.

Advantages and disadvantages of Corten steel

Corten steel offers unique benefits for outdoor signage and architectural projects, but it’s important to know its strengths and limitations.

Despite the potential challenges, Corten steel’s natural aging process can be used to create visually dynamic, evolving signs that reflect a brand’s growth or a location’s changing environment, offering a unique aesthetic appeal over time. 

Tips for maintaining Corten steel

While Corten steel is known for its low maintenance requirements, proper care can enhance its performance and appearance over time. Here are some tips for maintaining Corten steel signage and architectural elements:

• Cleaning: Gently wash Corten steel surfaces with mild soap and water annually. Avoid harsh chemicals or abrasive tools that could damage the protective patina.
• Patina development: During the first few years, the patina may develop unevenly. This is normal and will typically even out over time. If desired, you can gently encourage uniform weathering by lightly misting the surface with water.
• Rust transfer: To prevent rust transfer in indoor applications, consider applying a clear, breathable sealant to the surface. This is especially important for lobby signs or other high-traffic areas.
• Environmental considerations: In coastal or highly polluted areas, more frequent inspections may be necessary. Look for signs of accelerated corrosion and resolve issues promptly.
• Lettering and details: For Corten steel lettering or intricate designs, ensure water doesn’t pool in crevices. Proper drainage helps maintain the desired aesthetic and prevents localized corrosion.
• Long-term care: While the patina protects the steel, periodic professional inspections can identify and address any potential issues before they become problems. This is particularly important for large-scale installations or memorial plaques.

Innovative applications of Corten steel in outdoor branding

Corten steel is being used in creative ways for outdoor branding, thanks to its distinctive aesthetic and lasting durability.

Laser-cut corten facades are a popular choice for outdoor branding. By incorporating brand logos or intricate patterns, these facades create a dynamic effect as light and shadow shift throughout the day. Corten steel is also often combined with materials like glass and stainless steel to create striking visual contrasts, enhancing the overall impact of the design.

In some cases, weathering steel is used for interactive public art installations that serve as both a branding tool and an engaging public experience. For nighttime displays, integrating lighting elements with Corten steel creates dramatic, eye-catching installations that bring a brand to life in low-light environments.

Dimensional letters and sculptural signage

Advanced water-jet cutting techniques allow for precise, intricate metal lettering and logo designs, while precision folding and welding create seamless, three-dimensional forms that stand out in any setting.

By playing with contrasting finishes, such as raw edges and patinated surfaces, designers can add layers of visual interest to signage. Oversized weathering steel letters are often integrated into architectural features, creating bold statements that serve both functional and aesthetic purposes.

Corporate monuments and memorial plaques

Corten steel and bronze are frequently used together in creating corporate monuments and memorial plaques, blending modern and traditional aesthetics. Weathering steel structures paired with cast bronze plaques offer a durable and eye-catching solution for commemorative signage.

Techniques like etching and inlays allow for detailed text and imagery to be incorporated into Corten steel surfaces, creating personalized and lasting tributes. Large-scale weathering steel sculptures can double as both corporate branding and public art, serving multiple functions in one installation. The use of cast bronze plaques also adds a level of refinement to memorials, ensuring both aesthetic quality and longevity. 

⚠️ Remember: Proper installation and maintenance are essential to preserve the integrity of these materials in outdoor settings, ensuring they remain impactful for years to come.

Elevate your brand with Impact Signs’ Corten steel solutions

Choosing Corten steel for your signage is an investment in long-term visual impact. As the material weathers, it not only maintains its structural integrity but also develops a unique character that sets your brand apart.

At Impact Signs, our expertise in metal fabrication helps us perfectly harness the power of this innovative material for your branding needs. Our team specializes in creating dimensional sign letters and metal plaques that make businesses stand out. By incorporating Corten steel into our signs, we can provide you with eye-catching, low-maintenance exterior displays that tell your brand’s story in a truly distinctive way.

Ready to explore how Corten steel can elevate your brand? Contact the Impact Signs team today!