Austenitic
Duplex Steel
Nickel Alloy
Cobalt Alloy

Is there such a strange building around you: it is a solid steel structure, but its whole body is covered with thick red and black rust. That's weathering steel.

Weathering steel, also known as atmospheric corrosion-resistant steel, is a low-alloy steel between ordinary steel and stainless steel. It is made of ordinary carbon steel with a certain amount of copper and corrosion-resistant elements such as phosphorus, chromium, nickel, titanium and vanadium. It not only has the characteristics of easy extension, high strength and fatigue resistance of ordinary steel, but also can reach 2-8 times of ordinary carbon steel in terms of corrosion resistance.

Why can weathering steel rust but not rot?

Weathering steel is different from ordinary steel. At the beginning, it will rust on the surface like ordinary steel. Due to its high alloying degree, this process is even faster than ordinary steel. However, due to the more complex lattice inside the weathering steel, a dark black dense rust layer will grow under the loose rust on the surface. In this uniform dense rust layer, nickel atoms replace some iron atoms, so that the rust layer has cation selectivity and inhibits the transmission of corrosive anions.

The weathering steel and the rust steel

This dense rust layer that makes the surface of weathering steel rusty, but the interior will not continue to rust. Because of its excellent performance, weathering steel is expensive. The price of weathering steel with similar properties is about 60% higher than that of ordinary steel. Therefore, although weathering steel looks ugly, ordinary buildings can't afford it.

Only containers, railway vehicles, oil derricks, drilling platforms and other structures with poor service environment and high requirements for steel corrosion resistance can use weathering steel.