904L stainless steel (UNS N08904) is a premium superaustenitic alloy engineered for extreme corrosion resistance in aggressive environments. With elevated chromium (19-23%), nickel (23-28%), molybdenum (4-5%), and copper (1-2%) content, it delivers superior performance against pitting, crevice corrosion, and sulfuric acid attack compared to standard 316L or duplex steels. Its high PREN (Pitting Resistance Equivalent >40) and carbon limitation (≤0.02%) make it ideal for chemical processing, offshore oil/gas systems, and pollution control equipment where chloride exposure and acidic media demand uncompromising material integrity.
1. Chemical Composition and Metallurgical Features
We analyze 904L’s chemical makeup and how each element supports performance:
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Nickel (Ni) 24–26 % enhances toughness and stabilizes the austenitic matrix.
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Chromium (Cr) 19–21 % forms the primary passivation film for general corrosion resistance.
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Molybdenum (Mo) 4–5 % boosts pitting and crevice corrosion resistance in chloride-bearing settings.
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Copper (Cu) 1.5–2 % further improves resistance in sulfuric and phosphoric acids.
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Carbon (C) ≤ 0.02 % limits carbide precipitation during welding, preserving grain-boundary integrity.
Trace additions (Mn, Si, N) provide deoxidation and slight strengthening effects.
2. Physical and Mechanical Properties
Key attributes measured at ambient temperature include:
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Density: 8.03 g/cm³
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Tensile Strength: ≥ 500 MPa
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Yield Strength: ≥ 215 MPa
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Elongation (A₅₀ mm): ≥ 40 %
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Hardness (HRB): ≤ 95
Our metallurgists perform full heat treatments to guarantee uniform microstructures and consistent mechanical performance across coil, plate, bar, and welded fabrications.
3. Corrosion Resistance in Aggressive Media
904L excels where chlorides, sulfates, and oxidizers predominate:
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Marine Environments: Outstanding protection against pitting under high-chloride conditions.
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Chemical Processing: Stable against sulfuric, phosphoric, and acetic acids up to moderate concentrations.
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Oil & Gas: Resists H₂S-induced stress corrosion cracking, especially in hydrated environments.
Periodic electrochemical tests confirm pitting potentials above 0 mV (SCE) in 3 % NaCl solutions at 25 °C.
4. High-Temperature Stability and Oxidation
We verify that 904L retains ductility and strength to 400 °C. Oxidation tests up to 870 °C show mass gains below 2 mg/cm², indicating good scale resistance. For service above 600 °C, intermittent cooling cycles preserve structural integrity.
5. Fabrication and Welding Best Practices
We recommend:
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Forming: Substantial work hardening requires annealing at 1040–1120 °C, followed by water quench.
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Welding: Use matching filler (e.g. ERNiCrMo-3). Preheat to 200–250 °C only if thick sections risk cracking; post-weld annealing is usually unnecessary thanks to low carbon.
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Machining: Apply moderate speeds and feeds; flood coolant protects from built-up edge.
6. Surface Finishes and Treatments
Available mill finishes include 2B, BA, and No. 4 polish. Electropolishing further reduces surface roughness to Ra ≤ 0.4 µm and removes embedded particulates, improving hygiene for pharmaceutical or food sectors.
7. Standards and Certification
We manufacture to meet or exceed:
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ASTM A240/A240M – heat-resistant and corrosion-resistant plate, sheet, and strip.
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EN 10204 3.1 inspection certificates.
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NACE MR0175/ISO 15156 – oil and gas sour-service requirements.
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RoHS 3 (2015/863/EU) – restricted substance compliance.
8. Comparison with 316L and 304L
| Property | 304L | 316L | 904L |
|---|---|---|---|
| Nickel (Ni) | 8–12 % | 10–14 % | 24–26 % |
| Molybdenum (Mo) | 0 % | 2–3 % | 4–5 % |
| Pitting Resistance Equivalent | ~15 | ~25 | ~40 |
| Chloride Stress-Corrosion Cracking | Moderate | Good | Excellent |
| Typical Applications | Kitchen, HVAC | Marine, pharma | Chemical, oil & gas |
904L’s higher alloy content comes at a premium, but its lifespan in corrosive settings often offsets initial material cost.
9. Global Price Comparison
We surveyed market quotes in July 2025 for 904L hot-rolled coil (per metric ton, FOB).
| Region | USD/ton (est.) |
|---|---|
| China | 4,800 |
| United States | 6,200 |
| Europe | 6,800 |
| India | 5,500 |
Prices fluctuate with nickel and molybdenum spot markets; Luokaiwei’s 100 % factory-price sourcing ensures competitive rates out of our Shanghai works.
10. Applications and Case Examples
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Chemical Reactors: Liners and piping in sulfuric acid plants.
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Oil & Gas Platforms: Heat exchangers and seawater cooling circuits.
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Pharmaceutical Equipment: Bioreactors and sterile transfer lines after electropolish.
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Nuclear Industry: Heat exchangers in cooling systems, benefiting from low activation impurities.
Case Study: We supplied 50 tons of 904L tubing for an offshore gas‐processing module; performance trials confirmed zero pitting over a 2-year inspection cycle.
11. Inventory, Custom Solutions, and Delivery Speed
At Luokaiwei, we maintain an on-hand stock of 904L coil, sheet, and pipe. Customers may choose:
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Standard dimensions – dispatched within 3–5 business days.
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Tailored sizes – cut-to-length, bent, or welded assemblies ready in 7–10 days.
Our streamlined workflow—from order receipt to quality check—delivers both bulk and small‐batch orders without middle‐man markups.
12. Environmental Footprint and Sustainability
We adhere to ISO 14001 systems. Scrap recycling circuits reclaim over 90 % of off-cuts. Our electric‐arc furnaces run on partially renewable power, lowering CO₂ emissions by approximately 15 % versus conventional practice.
13. Maintenance and Service Life
Routine inspection of polished surfaces and passivation treatments can extend service life beyond 30 years. For welded junctures, We recommend annual ultrasonic testing where safety is critical.
14. Frequently Asked Questions
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How does 904L compare to duplex stainless steels?
While duplex grades offer higher strength, 904L surpasses many in corrosion resistance under reducing acids. Service conditions dictate grade selection. -
Is post‐weld annealing required?
Usually not. Low carbon minimizes carbide formation, but parts exposed to extreme caustics may benefit from a 1040–1120 °C anneal. -
What minimum wall thickness is available for 904L pipe?
We offer seamless tubing from 1.6 mm up to 50 mm thick. Welded sections can be produced thicker on demand. -
Can 904L be used at cryogenic temperatures?
Yes; the austenitic structure maintains toughness down to –196 °C, making it suitable for LNG and cryogenic storage. -
How do shipping and tariffs impact landed cost?
Our direct exports from China reduce freight and customs brokerage fees. We assist with HS codes and documentation to streamline import clearance.
Official References
- 904L stainless steel – Wikipedia
- ASTM A240/A240M Standard Specification for Chromium and Chromium–Nickel Stainless Steel Plate, Sheet, and Strip
- Nickel Institute – Nickel Alloys Datasheets
- ASM International – Alloy 904L Data
- ISO 15156 – Materials for Use in H₂S-Containing Environments in Oil and Gas Production
