Austenitic Stainless Steel

304, 316

Cr: 16-20%, Ni: 8-12%, C: ≤0.08% (316 includes Mo: 2-3%)

Non-magnetic, excellent corrosion resistance, ductility, moderate high-temp resistance (≤800°C)

Food processing equipment, chemical tanks, architectural cladding

Ferritic Stainless Steel

430

Cr: 10.5-27%, C: ≤0.15%, No Ni

Magnetic, cost-effective, resistant to chloride corrosion, low strength

Appliance housings, automotive exhaust systems, cookware

Martensitic Stainless Steel

410, 420

Cr: 11.5-18%, C: 0.1-1.2%

High hardness/strength, moderate corrosion resistance, excellent wear resistance

Cutting tools, bearings, valve components

Duplex Stainless Steel

2205

Cr: 21-23%, Ni: 4.5-6.5%, Mo: 2.5-3.5%, N: 0.1-0.3%

Dual-phase (austenitic + ferritic), high strength, excellent chloride resistance, weldability

Marine engineering, petrochemicals, desalination plants

Chromium (Cr)

Forms Cr₂O₃ passive layer; essential for corrosion resistance (≥10.5% required for stainless steel)

Nickel (Ni)

Stabilizes austenitic structure, enhances toughness and acid resistance

Molybdenum (Mo)

Improves resistance to pitting/crevice corrosion (e.g., in 316 and 2205 grades)

Carbon (C)

Increases hardness but reduces corrosion resistance if excessive (risk of chromium carbide precipitation)

Nitrogen (N)

Enhances strength and corrosion resistance; partially substitutes Ni in duplex steels

Corrosion Resistance

Excellent in oxidative environments (e.g., air, freshwater); limited in reducing acids (e.g., HCl)

Formability

Austenitic grades: easy to shape; Martensitic grades: require heat treatment

Heat Resistance

Oxidation resistance up to 800–1000°C (varies with composition)

Surface Treatment

Compatible with polishing, sandblasting, or coatings for aesthetics/performance