A588

A588 is a designation under the ASTM International specification for high-strength, low-alloy structural steel with enhanced atmospheric corrosion resistance. It is commonly referred to as weathering steel and is marketed in various forms, including plates and shapes, for outdoor structural use. The most widely used grades are A588 Grade A and Grade B, which share the weathering characteristics that allow the steel to form a protective oxide layer in outdoor environments.

The corrosion resistance of A588 arises from deliberate alloying with copper and other elements, which promotes the formation of a stable patina. When exposed to the atmosphere, the initial iron oxide is transformed into a denser, adherent layer that slows further corrosion. This self-protecting patina enables many outdoor applications to reduce or eliminate routine painting, provided the structure is in a suitable environment free from severe chloride exposure.

In terms of mechanical properties, A588 is a high-strength structural steel. It offers a relatively high yield strength and tensile strength for its class, with minimum values that are commonly cited around 50 ksi (345 MPa) for yield and approximately 70 ksi (480 MPa) for tensile strength, varying with grade and thickness. The material is designed for structural performance in general construction, bridges, and other load-bearing outdoor uses.

Applications for A588 include bridge components, building frames, columns, trusses, and outdoor architectural elements where long-term durability and reduced maintenance are prioritized. Fabrication involves standard HSLA practices, with attention to welding and finishing to maintain the corrosion-resistant characteristics. While it can be used without painting in many environments, coastal or highly chlorinated settings may require protective measures or periodic inspections.