Comparison of 304 and 316 Stainless Steel: Standard vs Molybdenum-Containing Austenitic Grade

304 and 316 are the two most widely used austenitic stainless steels, with the core difference being whether molybdenum is added. 316 has better chloride ion corrosion resistance due to molybdenum addition, while 304 has lower cost. The two are the primary choices for general and harsh corrosion environments respectively.

Core Parameter Comparison

Parameter	304 Stainless Steel	316 Stainless Steel
Chemical Composition (wt%)	C≤0.08, Cr=18.00-20.00, Ni=8.00-10.50, Fe=Balance	C≤0.08, Cr=16.00-18.00, Ni=10.00-14.00, Mo=2.00-3.00, Fe=Balance
Mechanical Properties (Annealed)	Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness ≤201HB	Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness ≤217HB
Service Temperature	-270℃ to 870℃ (continuous service)	-196℃ to 870℃ (continuous service)
Equivalent Grades	SUS304 (JIS), EN 1.4301, UNS S30400	SUS316 (JIS), EN 1.4401, UNS S31600

Key Performance Differences: 1. Corrosion resistance: 316's molybdenum addition makes its chloride ion corrosion resistance 3-5 times higher than 304; in 3.5% NaCl solution, 316's annual corrosion rate is ≤0.005mm, 304 is 0.02-0.05mm. 2. High-temperature performance: 316 has better high-temperature oxidation resistance than 304, suitable for higher temperature corrosive environments. 3. Low-temperature performance: 304 has better ultra-low temperature toughness (-270℃) than 316 (-196℃). 4. Cost: 316 is 40-50% more expensive than 304, due to molybdenum and higher nickel content.

Applicable Scenario Distinction: 304 is suitable for general corrosion-resistant environments, such as household appliances, architectural decoration, food processing equipment (dry or fresh water), and indoor pipelines. 316 is suitable for harsh corrosion environments, such as marine engineering, chemical equipment (chloride-containing media), food processing (pickling), medical implants, and coastal architectural decoration.

Practical Q&A

Q1: What is the core factor for choosing 316 over 304? A1: The presence of chloride ions in the working environment (seawater, salt spray, chloride-containing chemicals); 304 is prone to pitting corrosion in chloride ion environments, while 316 can resist it.

Q2: Can 304 be used in coastal areas? A2: It can be used for indoor decoration, but not recommended for outdoor components (e.g., handrails, door frames) exposed to salt spray for a long time; 316 is preferred for coastal outdoor applications.

Q3: Which is more suitable for food processing equipment, 304 or 316? A3: 304 is suitable for dry food or fresh water processing; 316 is suitable for pickling, salted food processing, or equipment requiring frequent cleaning with chemical detergents.

Q4: What is the wear resistance of 304 and 316? A4: Similar, Brinell hardness ≤201HB (304) and ≤217HB (316); for wear-intensive scenarios, both need surface hardening treatment (nitriding, shot peening).

Q5: How to distinguish 304 and 316 by simple methods? A5: Chemical composition analysis (316 contains 2-3% molybdenum, 304 does not); in magnetic test, both are non-magnetic (annealed state); 316 has better corrosion resistance in salt spray test.