Alloy content and environmental conditions are key factors influencing the formation of an oxide film on steel. Under appropriate atmospheric conditions, Weathering steel develops a durable, tightly adherent protective oxide coating. The appearance, texture and maturity of this coating depend on three interrelated factors: time, degree of exposure and atmospheric environment. With time, the oxide coating changes from a “rusty” red-orange to a dark purple-brown patina. The moderately rough texture becomes more distinct as the coating thickens. The rich patina of Weathering Steel is being seen more often in unpainted applications for bridges, utility and sign poles, structures and highway guardrails. The aesthetic values of this weathered and textured material, and more importantly, the practical values of Weathering Steel make this steel particularly useful for applications where strength, ease of fabrication and appearance are paramount. This brochure provides owners, designers, structural engineers, bridge engineers and contractors important information about Weathering Steel including its use, handling, fabrication, availability, properties and specifications.