Municipal wastewater: 304 is commonly used for tanks and piping; 316L is recommended for chlorinated disinfection stages; pay attention to H2S and microbial corrosion.

Seawater desalination: The high-pressure section of reverse osmosis and energy recovery devices mostly use 2205, 2507, or super duplex stainless steel; 316L carries high risk on the concentrated brine side.

Pure water/ultrapure water: The internal surfaces of 316L are electropolished to control roughness and precipitates; pipe welding requires high-purity argon shielding.

Common key points: Crevices and deposits are the starting points of corrosion, so structural design should avoid dead corners; chloride ion concentration and temperature are the core parameters for material selection.