The main differences between stainless steel SUS316L and duplex stainless steel are their chemical compositions and properties.

SUS316L is a type of stainless steel that is commonly used in various industries, including food and beverage, pharmaceuticals, and petrochemicals. It is known for its good corrosion resistance, especially in acidic environments. SUS316L has a higher nickel content than other types of stainless steel, which helps to improve its corrosion resistance. It also has a good resistance to temperature, and can be used in applications where the temperature may vary.

Duplex stainless steel is a type of stainless steel that has a different structure than SUS316L. It has a mixed microstructure of ferrite and austenite, which gives it a higher strength and better resistance to stress corrosion cracking than SUS316L. Duplex stainless steel also has a higher resistance to pitting and crevice corrosion than SUS316L, which makes it a good choice for applications where these types of corrosion are a concern.

Overall, the choice between SUS316L and duplex stainless steel will depend on the specific requirements of the application, including the type of corrosion that is a concern, the temperature range, and the strength requirements.  (–Following text: Stainless steel SUS304, SUS316L and Duplex materials use for hot water tanks)