A588 Standard Specification for Grade A Weathering Steel

The A588 Standard Specification is an American Society for Testing and Materials (ASTM) standard that covers high strength, low-alloy structural steel. Specifically, the A588 Standard Specification defines the requirements for Grade A weathering steel—a type of alloy steel that is designed to provide superior corrosion resistance in outdoor applications.

Grade A weathering steel exhibits greater corrosion resistance than standard carbon steel. This enhanced corrosion resistance is the result of a highly-reactive oxidation layer that forms when the steel is exposed to wet, salty, or acidic conditions. This layer, known as the patina, prevents the spread of corrosion, protecting the steel against damage.

The A588 Standard Specification outlines specific requirements that must be met for Grade A weathering steel. This includes requirements related to chemical composition, tensile strength, microstructure, and mill test report. The chemical composition requirements for Grade A weathering steel are carbon 0.19%, phosphorus 0.03%, sulfur 0.03%, and other trace elements, including copper, chromium, and nickel.

Grade A weathering steel must also meet specific tensile strength requirements. For steel with a minimum thickness of .1875 inch, the minimum tensile strength is 70 KSI (490 MPa). For steel with a minimum thickness of .5000 inch, the minimum tensile strength is 58KSI (400 MPa).

The A588 Standard Specification also requires that Grade A weathering steel exhibit a uniform microstructure with a fine grain size. This ensures that the steel has good resistance to stress and cracking, increasing its longevity and durability.

In addition, the A588 Standard Specification requires that Grade A weathering steel be accompanied by a third-party Mill Test Report that attests to its specific chemical composition. This report must certify that the steel meets the requirements of the A588 Standard Specification.

Grade A weathering steel is widely used in outdoor applications due to its superior corrosion resistance. Its combination of strength and chemical makeup make it an ideal choice for structural elements like bridges and buildings, which are frequently exposed to the elements.

The A588 Standard Specification ensures that Grade A weathering steel meets the necessary criteria for use in outdoor applications. By outlining specific requirements related to chemical composition, tensile strength, microstructure, and mill test report, the A588 Standard Specification ensures that Grade A weathering steel is of the highest quality.