To increase the resistance of weathering steels to corrosion, alloying elements such as copper, phosphorous, nickel, or chromium are incorporated. These alloys create an oxide layer which remains stable and adheres to the metal’s surface. A rust ‘patina’ develops as the weathering steel is exposed to alternate wetting and drying cycles. As well as being aesthetically pleasing, the patina creates a protective barrier which impedes the access of oxygen, moisture, and pollutants to the metal’s surface. This results in a much lower corrosion rate than that of untreated structural steels
