A588 weathering steel, also known as Cor-Ten (trademark name), is a high-strength low-alloy (HSLA) steel that forms a stable, self-protecting rust layer when exposed to atmospheric conditions. This unique property makes it exceptionally durable for outdoor structures such as bridges, transmission towers, railcars, and building facades.
How It Works. A588 contains small amounts of copper (0.25–0.40%), chromium (0.40–0.65%), nickel (up to 0.45%), and silicon (0.30–0.65%). During repeated wet/dry cycles, these alloying elements promote the formation of a dense, adherent patina that is approximately 50–100 microns thick. Unlike ordinary rust, which flakes off and allows continued oxidation, this patina acts as a barrier that slows further corrosion by 4–8 times compared to plain carbon steel. Once established (usually after 1–3 years of exposure), the patina eliminates the need for painting, reducing maintenance costs significantly over the structure’s lifetime.
Mechanical Properties. A588 has a minimum yield strength of 50 ksi (345 MPa) for thicknesses up to 4 inches, and 46 ksi for heavier sections. Tensile strength ranges from 70 to 90 ksi. This strength level is comparable to ASTM A572 Grade 50, allowing designers to use thinner sections than with ordinary A36 steel, reducing dead weight. Elongation is at least 18%, providing good ductility. The material retains toughness at low temperatures (down to -20°F) and is suitable for seismic zones.
Applications. Classic examples include the New York City’s Queensboro Bridge (using bare weathering steel), many highway sign structures, and the famous Picasso sculpture in Chicago. For pedestrian bridges, A588 provides a natural aesthetic that blends with landscapes. In railway hopper cars, it withstands abrasive coal and corrosive fertilizers. Transmission towers benefit from reduced weight and no painting, lowering installation costs in remote areas.
Fabrication Considerations. A588 welds similarly to other HSLA steels but requires low-hydrogen welding electrodes (E7018 or E80xx series) to prevent hydrogen-induced cracking. Preheat and interpass temperatures of 50–100°F are recommended for thick sections. Bolted connections should use galvanized or weathering steel fasteners. Do not bury A588 in continuously wet soil or use it in severe industrial environments with concentrated chlorides; it is not stainless steel. With proper detailing to avoid water traps, A588 offers an unmatched combination of strength, durability, and lifecycle economy.
Just like you, 70% customers choose long-term cooperation with BBN steel not only for our good product and service quality, good reputation in the international market, but also for our experienced one-stop raw material supply and further steel processing!
