The alloying elements contained in weathering steel remain within 2 wt. % and are primarily represented by Cu, Cr, P, and Ni. What matters is the balance of individual alloying elements, especially the Cu–P–Cr combination. Weathering steel is mainly used in designing bridge structures, lattice towers from sections and tubes, but also as roofing and cladding materials or decorative material. The increased resistance to corrosion in the atmosphere results from the development of a compact adhesive corrosion layer on the surface that reduces corrosion rate to a technically permissible limit.