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Should I use 304 or 316 stainless steel?
Use 304 for indoor, food and fresh-water service: it costs about 25% less than 316 and machines faster. Use 316 wherever salt or chlorides are present, including coastal hardware, road de-icing salt, pools and many process chemicals. Its 2–3% molybdenum raises the pitting resistance equivalent number (PREN) to about 24, from about 19 for 304.
Stainless steel 304
Stainless steel 316
By the numbers
Priced on the same representative part: plate, cnc machining, 50 pcs.
Tensile strengthMPa
304 SS
505
316 SS
580
Yield strengthMPa
304 SS
215
316 SS
290
Densityg/cm³
304 SS
8
316 SS
8
Max service temp°C
304 SS
925
316 SS
925
Elongation%
304 SS
70
316 SS
50
Raw material cost$/kg
304 SS
6
316 SS
8
Which should you pick?
Pick 304 SS when
- Service is indoor, food or fresh water with no salt
- The part is deep drawn or stamped in volume
- Material cost matters and 304 meets the environment
- Machine time matters: 304 rates 45% versus 36% for 316
Pick 316 SS when
- Parts sit near the coast or see road salt
- Wash-down uses chlorinated sanitizers
- It is marine hardware above the waterline
- Service is chemical, pharmaceutical or water treatment
Key differences
| 304 SS | 316 SS | |
|---|---|---|
| Molybdenum | None | 2–3% |
| PREN (pitting resistance) | About 19 | About 24 |
| Chloride service | Pits and crevice-corrodes in salt spray, pool water and de-icing salt | Resists salt air and splash; still pits in warm seawater and tight crevices |
| Welded grade | 304L, 0.03% carbon maximum | 316L, 0.03% carbon maximum |
| Magnetism after cold work | Becomes slightly magnetic | Stays less magnetic because of higher nickel |
| Next step up | 316 for chlorides | Duplex 2205 or super-austenitic grades for seawater |
| Relative cost | Baseline | About one-third more |
Questions
Is 316 stainless stronger than 304?
Slightly. Annealed 316 runs about 84 ksi (580 MPa) tensile and 42 ksi (290 MPa) yield versus 73 ksi (505 MPa) and 31 ksi (215 MPa) for 304. The reason to choose 316 is chloride resistance, not strength.
How can I tell 304 from 316?
Not with a magnet; both are non-magnetic when annealed. Check the mill certification, or test with an XRF analyzer or a molybdenum spot test, which detects the 2–3% molybdenum in 316.
Is 304 stainless OK outdoors?
Inland, usually yes. Near the coast, or where road salt or pool chemicals reach the part, 304 tea-stains and pits; use 316. Passivation after fabrication helps both grades.
Try both on your part.
The builder prices the same geometry in every suitable process and material, with DFM for each.