904L vs 316L Stainless Steel
Side-by-side comparison · Composition · Properties · Selection guide
904L is what you specify after 316L fails. With ~25% nickel, 20% chromium, 4.5% molybdenum and copper, its pitting index (PREN ≈35) and hot-acid resistance leave 316L (PREN ≈25) far behind — at several times the price. 316L remains the rational default for everyday corrosive service.
Full datasheets:904L Stainless Steel·316L Stainless Steel
At a Glance
| 904L | 316L | |
|---|---|---|
| Type | Super-austenitic | Austenitic (low carbon, Mo-bearing) |
| UNS | N08904 | S31603 |
| Standard | ASTM A240/A240M, B625 | ASTM A240/A240M |
| Density | 8 g/cm³ | 7.98 g/cm³ |
Corrosion Resistance and Service Limits
904L
- General corrosion resistance comes from the chromium-rich passive film; nickel, molybdenum, nitrogen and copper change performance by grade.
- Check chlorides, temperature, crevices, deposits, process chemistry and cleaning conditions. A grade designation alone is not a service-life guarantee.
316L
- General corrosion resistance comes from the chromium-rich passive film; nickel, molybdenum, nitrogen and copper change performance by grade.
- Check chlorides, temperature, crevices, deposits, process chemistry and cleaning conditions. A grade designation alone is not a service-life guarantee.
Fabrication and Heat Treatment
| Operation | 904L | 316L |
|---|---|---|
| Welding | Generally weldable with a qualified procedure and matching or over-alloyed filler where required; remove heat tint when corrosion service demands it. | Generally weldable with a qualified procedure and matching or over-alloyed filler where required; remove heat tint when corrosion service demands it. |
| Forming | Good ductility is typical, but rapid work hardening increases forming load and springback; bend radius and intermediate annealing depend on grade and reduction. | Good ductility is typical, but rapid work hardening increases forming load and springback; bend radius and intermediate annealing depend on grade and reduction. |
| Machining | Use rigid tooling, positive feeds and controlled heat because the material work-hardens; free-machining grades require separate corrosion and welding review. | Use rigid tooling, positive feeds and controlled heat because the material work-hardens; free-machining grades require separate corrosion and welding review. |
| Heat treatment | Solution annealing and rapid cooling restore the intended condition where applicable. Austenitic grades are not hardened by conventional quench-and-temper treatment. | Solution annealing and rapid cooling restore the intended condition where applicable. Austenitic grades are not hardened by conventional quench-and-temper treatment. |
Chemical Composition (wt%)
| Element | 904L | 316L |
|---|---|---|
| C | ≤0.020 | ≤0.030 |
| Mn | ≤2.00 | ≤2.00 |
| Si | ≤1.00 | ≤0.75 |
| Cr | 19.0–23.0 | 16.0–18.0 |
| Ni | 23.0–28.0 | 10.0–14.0 |
| Mo | 4.0–5.0 | 2.00–3.00 |
| Cu | 1.0–2.0 | — |
| P | ≤0.045 | ≤0.045 |
| S | ≤0.035 | ≤0.030 |
Mechanical Properties
| Property | 904L | 316L |
|---|---|---|
| Tensile strength | ≥490 MPa (71 ksi) | ≥485 MPa (70 ksi) |
| Yield strength (0.2%) | ≥215 MPa (31 ksi) | ≥170 MPa (25 ksi) |
| Elongation (50 mm) | ≥35% | ≥40% |
| PREN | ≈35 | — |
| Hardness | — | ≤217 HBW |
Which One Should You Choose?
Choose 904L for:
- Sulfuric and phosphoric acid circuits
- Flue-gas desulfurization and scrubber internals
- Hot chloride brines at the edge of 316L capability
- Premium consumer surfaces (watch cases) where polish and inertness sell
Choose 316L for:
- General chemical, food and pharmaceutical equipment
- Marine hardware and coastal architecture
- Everything where 316L has a proven service record
- Cost-conscious projects — 904L runs 3–5× the price
Our verdict
Treat 904L as a corrosion specialist, justified only by an environment audit: acid concentration, temperature and chloride level. Where 316L survives, its lower cost and universal availability win. Where it pits or cracks, jumping to 904L (or duplex 2507, often cheaper for chloride duty) is the established fix.
Cost and Availability
Compare the current stock position, mill route, minimum production quantity, processing yield, testing and delivered cost for 904L and 316L at quotation time. A fixed price ratio would be misleading because product form, size, condition and market timing can change the commercial result.
Do Not Substitute Without Review
Do not replace 904L with 316L, or the reverse, from the grade name alone. Recheck chemistry, mechanical-property condition, product standard, dimensions, corrosion environment, welding procedure and project approval before substitution.
904L & 316L Products We Export
316L Stainless Steel Sheet
316/316L stainless steel sheet for marine and chemical service, in quotation-confirmed dimensions in 2B, BA and brushed finishes, cut to size, with ordered documentation.
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316L Stainless Steel Seamless Pipe
Seamless 316L stainless steel pipe to ASTM A312, in quotation-confirmed NPS and schedule, pickled and annealed, with ordered documentation — for chemical, marine and process service.
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Frequently Asked Questions
Is 904L stronger than 316L?
No — minimum strengths are similar (490 vs 485 MPa tensile). The premium buys alloy content and corrosion margin. For strength plus chloride resistance at lower cost, duplex grades are the better lever.
Why did Rolex choose 904L for watch cases?
High alloy content lets it take an exceptionally bright, uniform polish and shrug off sweat and pool water indefinitely. It is a marketing-visible corrosion upgrade; mechanically it behaves like any austenitic stainless.
Can 904L be substituted without changing fabrication?
Not automatically. It needs compatible filler and qualified welding, and its higher alloy content can affect machining, forming and availability. Confirm the full product and project requirements.
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Technical content updated: 2026-07-29
Organizational author: Tsingshan (Shandong) Iron & Steel Co., Ltd..Review method, status and limitations.