Weathering steels are low-alloy steels formulated specifically to form tightly adherent, dense corrosion products that inhibit corrosion in some atmospheric environments.

• A. Stainless steels
• B. Weathering steels
• C. Tool steels
• D. Carbon steels

Answer: (B)

Weathering steels are designed to develop a stable, protective oxide layer on their surface when exposed to certain atmospheric conditions. The alloying elements, including copper and other small amounts of chromium, nickel, or phosphorus, promote the formation of a dense, tightly adherent corrosion product—often called a patina—that acts as a barrier to moisture and oxygen. Once this patina forms, it slows further corrosion, so the long-term corrosion rate in those environments is reduced compared to ordinary carbon steels.

This is why the statement correctly describes weathering steels: their defining feature is the protective patina that forms in specific atmospheres, not the reliance on a passive film like stainless steels or the different purposes of tool steels, and not the behavior of plain carbon steels. In environments with high chloride content or aggressive pollutants, the patina may be compromised, but in suitable atmospheres, the dense, adherent corrosion products effectively inhibit ongoing corrosion.