UNS S31803 / UNS S32205 is a typical duplex stainless steel, known for its excellent mechanical properties and corrosion resistance. Its microstructure consists of about 50% austenite and 50% ferrite. This duplex structure gives it high strength (yield strength is about twice that of ordinary austenitic stainless steel), good toughness and excellent resistance to stress corrosion cracking. The high chromium and molybdenum content makes it have excellent resistance to pitting and crevice corrosion in chloride environments (such as seawater and salt water), and the addition of nitrogen further improves the corrosion resistance and stabilizes the austenite phase. In addition, its uniform corrosion resistance is comparable to that of 316L stainless steel, but its localized corrosion resistance is significantly better than that of the 304/316 series.

UNS S31803 / UNS S32205 duplex stainless steel is widely used in harsh environments, including the oil and gas industry (submarine pipelines, pressure vessels, heat exchangers), chemical equipment (reactors, storage tanks, desalination units), seawater treatment systems (pumps and valves, desulfurization equipment), energy fields (flue gas desulfurization towers, nuclear fuel processing) and bleaching equipment in the paper industry. Its high strength and lightweight properties also make it an ideal material for structural parts such as bridge cables and building curtain walls. Compared with high-alloy austenitic stainless steel (such as 904L), UNS S31803 / UNS S32205 can provide similar or better corrosion resistance at a lower cost in most scenarios, while having good weldability. Attention should be paid to controlling heat input to avoid harmful phase precipitation. In short, the alloy achieves a balance between economy and reliability in areas where corrosion and mechanical properties are equally important.