All three types are duplex stainless steels (a mixed microstructure of austenite and ferrite). Their key characteristic is that their strength is twice that of 316L, and they possess exceptional resistance to stress corrosion cracking. In simple terms: 2304 is an "entry-level economical grade", 2205 is an "all-round mainstay", and 2507 is a "super heavy-duty grade". The core differences lie in their alloy content and Pitting Resistance Equivalent Number (PREN): approximately 25 for 2304, around 35 for 2205, and as high as 42+ for 2507. This means 2507 offers more than three times the resistance to chloride-induced pitting corrosion compared to 2304. A comparison of their specific properties and applications is as follows: · 2304 (low-alloy economical grade): Contains 23% chromium and 4% nickel, offering excellent cost performance. It has higher strength than 304, with corrosion resistance between that of 304 and 316. It is mainly used in storage tanks, water heaters, bridge components, and other scenarios requiring strength but not extreme corrosion resistance, often replacing 304 to reduce wall thickness.· 2205 (the most widely used mainstay grade): Contains 22% chromium, 3% molybdenum, and 5.5% nickel, with the most balanced overall performance. Its resistance to pitting and crevice corrosion far exceeds that of 316L, and it has outstanding resistance to chloride-induced stress corrosion cracking. It is the primary choice for medium-to-high corrosion environments such as chemical pipelines, offshore platforms, pulp digesters, and flue gas desulfurization systems.· 2507 (super high-end grade): Contains 25% chromium, 4% molybdenum, 7% nickel, and nitrogen, boasting the top-tier corrosion resistance and strength among duplex stainless steels. It is specifically designed for extremely harsh environments where 316L fails within weeks, such as high-pressure pumps for seawater desalination, subsea oil and gas pipelines, and heat exchangers for strong acids (e.g., sulfuric acid).