316 Stainless vs 904L Stainless
316 and 904L are both austenitic stainless built for corrosion resistance, but 904L is a super-austenitic grade with far higher nickel, chromium, molybdenum and added copper. Engineers weigh them when 316's pitting or acid resistance falls short — particularly in sulfuric and other reducing acids — and a more heavily alloyed, more expensive grade is justified.
The verdict
Choose 316 for general marine, medical, food and chemical service where its 2-3% molybdenum gives excellent corrosion resistance at moderate cost. Choose 904L when the environment is severe — concentrated sulfuric or phosphoric acid and high-chloride media — where its higher Mo (~4.5%) and copper addition resist attack that pits 316, accepting higher cost and harder machining.
Side-by-side data
| Property | 316 Stainless | 904L Stainless |
|---|---|---|
| Category | Stainless Steel | Stainless Steel |
| Density (g/cm³) | 8.0 | 8 |
| Tensile strength (MPa) | 515 | 520 |
| Yield strength (MPa) | 240 | 220 |
| Elongation (%) | 40 | 35 |
| Hardness | 217 HB | 70 HRB |
| Max service temp (°C) | 870 | 400 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 16 | 12 |
| Typically used for | Marine, medical & chemical environments | Sulfuric acid & severe corrosion |
Which should you choose?
Choose 316 Stainless when…
- The application is general marine, medical, food or moderate chemical service
- Cost matters and 904L's heavy alloying isn't justified by the environment
- The part is widely formed or fabricated from a readily-stocked grade
- Pitting load is moderate — 316's 2-3% Mo handles typical chlorides
- Higher service temperature is needed (316 to ~870°C vs 904L's ~400°C here)
- You want easier machining than the gummy, work-hardening 904L
Choose 904L Stainless when…
- The medium is sulfuric, phosphoric or other reducing acids that attack 316
- High-chloride, high-pitting environments demand maximum corrosion resistance
- Resistance to chloride stress-corrosion cracking is needed (high nickel helps)
- Process equipment for acid handling, scrubbers or pollution control
- Crevice corrosion must be minimized via elevated Cr/Mo and copper
- The added material and machining cost is justified by avoiding corrosion failures
Key differences that matter
- 904L is super-austenitic with much higher Ni, Cr and ~4-5% Mo plus copper; 316 has 2-3% Mo
- 904L's copper addition specifically boosts resistance to sulfuric and other reducing acids
- Both rate at the top of this dataset's corrosion scale, but 904L outperforms 316 in severe acid/chloride media
- 904L's high nickel improves resistance to chloride stress-corrosion cracking versus 316
- 316 is easier and cheaper to machine; 904L is gummier and work-hardens more
- 904L costs significantly more (higher relative cost) due to heavy alloying
- 316 tolerates higher temperature in this data (~870°C) than 904L (~400°C)
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Open the Material SelectorGet a Quote →Frequently asked questions
Is 904L more corrosion resistant than 316?
In severe environments, yes. 904L's higher chromium and ~4-5% molybdenum give greater pitting and crevice resistance than 316's 2-3% Mo, and its copper addition makes it markedly better in sulfuric and other reducing acids. For everyday marine or food service 316 is ample; 904L earns its premium only in aggressive acid or high-chloride media.
Why does 904L resist sulfuric acid better?
Its alloy recipe is tuned for reducing acids: high molybdenum plus a deliberate copper addition stabilizes the passive film in sulfuric and phosphoric acid, where 316 would suffer general and pitting corrosion. That copper content is the signature feature separating 904L from ordinary austenitic grades like 316.
Is 316 cheaper than 904L?
Yes, considerably. 904L carries much higher nickel, chromium and molybdenum plus copper, so its raw-material cost is well above 316's. It also machines more slowly, raising finished-part cost. Unless the corrosion environment demands 904L, 316 delivers strong corrosion resistance for far less money.
Which is easier to machine?
316. Both are soft austenitic grades that work-harden, but 904L's higher alloy content makes it gummier and more prone to work-hardening, demanding rigid setups, sharp tools and slow feeds. Expect lower machining productivity and more tool wear with 904L than with 316.
Does 904L resist stress-corrosion cracking better than 316?
Yes. Austenitic 316 is vulnerable to chloride stress-corrosion cracking in hot chloride service. 904L's much higher nickel content improves resistance to that failure mode, which is one reason it is selected for demanding chloride and acid process equipment where 316 might crack.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.