13 Apr COR-TEN® vs. ASTM Weathering Steel: What Engineers Need to Know
When specifying weathering steel for bridges, buildings, or architectural applications, engineers often encounter two commonly used terms: COR-TEN® and ASTM weathering steel. While they’re frequently used interchangeably, there are important distinctions that can impact your project’s specifications, sourcing, and long-term performance.
Understanding the difference ensures you select the right material and avoid unnecessary limitations in procurement.
What is COR-TEN® Steel?
COR-TEN® is a trademarked name originally developed by U.S. Steel to describe a group of weathering steels designed to eliminate the need for painting while forming a stable, rust-like appearance over time.
The name comes from its key properties:
- CORrosion resistance
- TENsile strength
Today, COR-TEN® typically refers to two primary grades:
- COR-TEN® A (commonly used in architectural applications)
- COR-TEN® B (more common in structural applications)
However, it’s important to note that COR-TEN® is not a generic material specification—it is a brand name.
What Is ASTM Weathering Steel?
ASTM weathering steels are standardized materials defined by the ASTM International. These specifications ensure consistency in chemical composition, mechanical properties, and performance.
Common ASTM weathering steel grades include:
- ASTM A588 – Widely used for structural applications like bridges and buildings
- ASTM A242 – Often used in architectural and structural applications
- ASTM A847 – Common for hollow structural sections (HSS)
These steels are designed to form a protective patina that reduces corrosion over time when exposed to the environment.
Key Differences: COR-TEN® vs. ASTM Weathering Steel
1. Trademark vs. Specification
- COR-TEN®: A proprietary, trademarked product name
- ASTM Weathering Steel: Industry-standard specifications used across manufacturers
Why it matters: Specifying COR-TEN® may unnecessarily limit sourcing options, while ASTM grades allow for broader supplier flexibility.
2. Availability and Sourcing
- COR-TEN® is not always readily available and may come with longer lead times
- ASTM weathering steels are available through Central Steel Service
Engineer’s tip: Specifying ASTM grades can help avoid delays and reduce costs.
3. Performance and Properties
In most cases, ASTM A588 and COR-TEN® B offer comparable performance in terms of:
- Atmospheric corrosion resistance
- Strength
- Weldability
Similarly, ASTM A242 aligns closely with COR-TEN® A.
4. Specification Best Practices
Many project specs still call out COR-TEN®, but best practice is to use equivalent ASTM standards. This approach ensures:
- Competitive bidding
- Material availability
- Compliance with modern standards
Why Engineers are Moving Toward ASTM Specifications
Modern engineering and procurement practices prioritize flexibility and efficiency. By specifying ASTM weathering steel instead of a brand name, engineers can:
- Avoid proprietary restrictions
- Ensure consistent material quality
- Improve project timelines
- Reduce overall material costs
At the same time, they still achieve the same signature weathering performance and aesthetic.
Partner with Central Steel Service
Choosing the right material is only part of the equation. Working with an experienced weathering steel supplier ensures you get the right product, on time, and to spec.
We are a COR-TEN® and ASTM weathering steel supplier specializing in the distribution of High Strength Weathering, High Strength and Abrasion Resistant Steel products. We understand that the unique applications demanding these specialty products require the utmost attention to quality and material trace-ability. We strive to provide exceptional service while supplying your steel needs and facilitating the success of your company.
Whether you’re designing a pedestrian bridge, façade system, or public art installation, our team can help you navigate specifications and sourcing with confidence.