Stainless Steel Grades
SS 304L (1.4307 / UNS S30403) is the most economical stainless option with a cost index of 1.0x. It provides moderate corrosion resistance with a PREN of 18.0, suitable for freshwater applications with chloride levels below 200 ppm. Its excellent weldability makes it the preferred choice for standard wedge wire production. Best for general industrial water filtration and indoor/controlled environments.
SS 316L (1.4404 / UNS S31603) is the industry standard workhorse at a cost index of 1.30x. The addition of 2-3% molybdenum raises the PREN from 18.0 to 24.2, extending chloride tolerance to approximately 1,000 ppm at ambient temperature. It is the only grade that meets FDA, 3-A, and EHEDG food safety requirements and can be electropolished for hygienic surfaces. Best for water treatment, food and beverage, pharmaceutical, and mild chemical processing.
SS 316Ti (1.4571 / UNS S31635) is the high-temperature variant at a cost index of 1.35x. Titanium stabilization prevents sensitization above 400 degrees C, enabling sustained operation up to 900 degrees C while maintaining the chloride resistance of standard 316. Best for petrochemical processing, flue gas treatment, and hot chemical environments.
SS 321 (1.4541 / UNS S32100) provides an economical high-temperature solution at a cost index of 1.10x. Like 316Ti, it operates up to 900 degrees C through titanium stabilization, but without molybdenum it offers no chloride advantage over 304 (PREN 18.0). Best for high-temperature gas filtration, exhaust screening, and furnace applications where chlorides are not present.
Duplex Stainless Steel Grades
Duplex 2205 (1.4462 / UNS S32205) delivers exceptional performance at a cost index of 1.22x. Its dual-phase microstructure provides a yield strength of 450 MPa (2.6 times higher than 316L) and a PREN of 35.0 with chloride tolerance up to 3,600 ppm. Duplex 2205 is NACE-compliant for sour service applications. Best for seawater intake, desalination pre-treatment, offshore oil and gas, and aggressive mining environments.
Super Duplex 2507 (1.4410 / UNS S32750) is the ultimate corrosion-resistant option at a cost index of 1.96x. With a PREN of 42.5 (the highest of any stainless steel grade) and chloride tolerance up to 50,000 ppm, it is the only viable material for full seawater immersion with a 25+ year design life. Yield strength of 550 MPa (3.2 times higher than 316L). Best for desalination plants, offshore platform intakes, and aggressive chemical processing.
Carbon and Alloy Steel Grades
S355 structural steel offers the lowest cost at 0.35x with a yield strength of 355 MPa but provides zero corrosion resistance. S700 high-strength steel at 0.55x doubles the yield strength to 700 MPa for heavy-impact mining applications. Hardox 450/500 wear-resistant steel at 0.70x achieves extreme surface hardness (425-500 HBW) for 3-4 times the wear life of standard steel in abrasive environments.
