The protective oxide film on weathering steel structures requires from 3 to 5 years to stabilize in urban environments with some industrial activity. In rural areas the color stays light and the texture stays dusty for a longer period of time. The more tightly adherent chocolate brown oxide eventually begins to form. In proper protective oxide formation the color changes from an early yellow orange to light brown and is generally referred to as “dusty” because loose oxide particles can be easily rubbed off. Eventually the color approaches a chocolate brown and little can be rubbed off, as the surface becomes smoother.