Stainless steel, also called corrosion-resistant steel, can resist corrosion when exposed to air and moisture. Its non-rusting characteristic mainly depends on a special alloy element contained, that is, chromium. If the chromium content of steel is up to 12%, chemical reactions will take place between chromium and oxygen, which leads to a thin passive film of chromium oxide. The film may cover the steel and protect it from further corrosion. Besides that, other common alloy elements, like nickel, molybdenum, titanium, niobium, copper, nitrogen, contribute to other characteristics of stainless steel.
Stainless steel can be divided into four types by alloy element, namely, ferritic, austenitic, duplex and martensitic stainless steel.
1. Ferritic stainless steel possesses 12% to 30% chromium content, with better chloride resistance than other stainless steels. The more chromium content it has, the higher stain resistance, ductility and weldability it may be provided with.
2. Austenitic stainless steel contains a minimum of 18% chromium content, nearly 8% nickel and a small amount of molybdenum, titanium and nitrogen, which contributes to excellent corrosion resistance.
3. Duplex stainless steel enjoys the characteristics of austenite and ferrite, as well as superplasticity.
4. Martensitic stainless steel owns high strength, low plasticity and weldability.
Stainless steel has developed continuously and been well received in architecture industry. It won’t corrode, rust or abrade as long as it is appropriately machined and maintained. With high strength and corrosion resistance, it is able to permanently remain the same. The material can be made into building components easily because of high malleability.