304 vs 316: differences explained
304 vs 316 stainless steel: 316 adds 2–3 % molybdenum for chloride resistance (PREN 24 vs 18) at 20–40 % higher cost; strength, magnetism and weldability are the same. Full table and when to pay for 316.
Overview
304 and 316 are the two austenitic stainless steels that cover about 75 % of all stainless use, and the question of which one to buy comes up on every project that sees water, food or weather. The metallurgical difference is one element: 316 contains 2–3 % molybdenum (and about 2 % more nickel), which roughly triples its resistance to pitting and crevice corrosion by chlorides — salt water, road salt, brine, pool chemicals, many process streams. Everything else — strength, formability, weldability, hygiene, temperature range, non-magnetism — is essentially the same.
The cost of that molybdenum and nickel is 20–40 % on the material price. So the decision is an environment question, not a strength question: if chlorides are present and the surface stays wet, 316 pays for itself; if not, 304 does the job. The table below gives the numbers for both ASTM and EN designations (304 = 1.4301, 316 = 1.4401, 316L = 1.4404).
304 vs 316 side by side
| Property | 304 | 316 |
|---|---|---|
| ASTM / UNS | A240 304 / S30400 (304L: S30403) | A240 316 / S31600 (316L: S31603) |
| EN material number | 1.4301 (304L: 1.4307) | 1.4401 (316L: 1.4404) |
| Chromium | 18–20 % | 16–18 % |
| Nickel | 8–10.5 % | 10–14 % |
| Molybdenum | — | 2–3 % |
| PREN (Cr + 3.3 Mo + 16 N) | ≈ 18–20 | ≈ 24–26 |
| Critical pitting temperature (6 % FeCl₃) | ≈ 5–10 °C | ≈ 15–20 °C |
| Min. yield (annealed) | 205 MPa (30 ksi) | 205 MPa (30 ksi) |
| Min. tensile | 515 MPa (75 ksi) | 515 MPa (75 ksi) |
| Elongation | ≥ 40 % | ≥ 40 % |
| Hardness (annealed max) | 201 HB / 92 HRB | 217 HB / 95 HRB |
| Magnetic (annealed) | No | No (even less after cold work) |
| Max. service temperature (oxidation) | 870 °C continuous | 870 °C continuous |
| Chloride SCC threshold | ≈ 60 °C in chloride water | ≈ 60 °C (marginally better) |
| Seawater / marine atmosphere | tea staining, pitting | good (splash zone); crevice attack if immersed and stagnant |
| Sulphuric acid, dilute | poor | fair (to ~5 % at ambient) |
| Nitric acid | excellent | good |
| Weldability | excellent (ER308L) | excellent (ER316L) |
| Machinability (vs B1112) | ≈ 45 % | ≈ 40 % |
| Density | 8.0 g/cm³ | 8.0 g/cm³ |
| Thermal expansion (0–100 °C) | 17.2 × 10⁻⁶/K | 16.0 × 10⁻⁶/K |
| Relative price (2026, sheet) | 1.00 | ≈ 1.25–1.40 |
| Fastener class (ISO 3506) | A2 | A4 |
Which should you choose?
Buy 316 (or 316L) when chlorides are present and the surface stays wet or is rarely cleaned: coastal buildings within a few kilometres of the sea, marine hardware, swimming-pool and spa fittings, de-icing-salt exposure, brine and pickling lines, most chemical and pharmaceutical process equipment, and anything embedded or crevice-prone outdoors.
Buy 304 (or 304L) everywhere else: kitchens, food and dairy equipment, brewing, inland architecture, water tanks, automotive trim, indoor railings, fasteners in dry service. It is cheaper, marginally easier to machine and polish, and equally strong.
A useful rule: if a 304 part in that location would show 'tea staining' within a year, it should be 316. If you are unsure, the price of 316 is cheaper than the cost of replacing a pitted 304 part.
- Kitchens, catering, food and dairy processing
- Inland and urban architecture, handrails, cladding
- Water tanks, brewing, wine, pharmaceutical dry areas
- Automotive trim, appliance panels, indoor furniture
- Nitric-acid and oxidizing chemical service
- Cost-sensitive fasteners and hardware indoors (A2)
- Coastal and marine exposure, boat fittings, harbours
- Swimming pools, spas, water parks (with maintenance)
- De-icing salt zones: bridges, tunnels, street furniture
- Chemical, petrochemical and pharmaceutical process equipment
- Brine, seawater cooling, desalination pre-treatment
- Medical implants and instruments (316L), A4 fasteners outdoors
Frequently asked questions
What is the main difference between 304 and 316 stainless steel?
316 contains 2–3 % molybdenum (304 has none) and slightly more nickel. Molybdenum raises resistance to pitting and crevice corrosion by chlorides — salt water, road salt, brine — from PREN ≈ 18 to ≈ 24. Mechanical properties are the same.
Is 316 stronger than 304?
No. Both have 205 MPa minimum yield and 515 MPa tensile in the annealed state; 316 is marginally stronger at high temperature and slightly harder (217 vs 201 HB max). Choose between them on corrosion, not strength.
How can I tell 304 from 316?
Not by eye or magnet — both are non-magnetic and look identical. Use a molybdenum spot test (a drop reagent that turns dark on Mo-bearing steel), an XRF analyser, or the mill certificate / stencil.
Is 316 worth the extra cost?
Where chlorides are present and surfaces stay wet — yes; a pitted 304 part costs far more to replace than the 25–40 % premium. Inland, indoor and food-contact uses without chlorides gain nothing from 316.
What about 304L and 316L?
The L versions limit carbon to 0.03 % to avoid sensitization in welds thicker than about 6 mm. Most coil today is dual-certified 304/304L and 316/316L, so you get the low carbon anyway; the 304-vs-316 decision is unchanged.
Which is better for outdoor use?
316 near the coast or road salt; 304 inland with normal rainfall washing. Both will 'tea stain' in unwashed sheltered marine locations; for the worst cases (indoor pools, warm seawater) use duplex 2205 instead.
Is 316 more magnetic than 304?
No — 316 is if anything less magnetic after cold work, because its higher nickel content stabilizes the austenite.
Related comparisons
Verified against ASTM A240/A240M-22. Last checked: September 2026.