904L Super Austenitic Stainless Steel Pipe for Corrosive Service
Mar 16, 2026
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What is 904L super austenitic stainless steel pipe for corrosive service?
904L (UNS N08904/EN 1.4539) is a premium super austenitic stainless steel pipe engineered specifically for severe corrosive environments such as sulfuric acid, phosphoric acid, and seawater. Adopting a high-alloy composition design (containing 19-23% Cr, 23-28% Ni, 4-5% Mo, and 1-2% Cu), its Pitting Resistance Equivalent Number (PREN) is ≥ 43, far surpassing standard 316L stainless steel (PREN ~25). Meanwhile, it features low carbon characteristics (C ≤ 0.020%), preventing intergranular corrosion during welding. This ensures long-term structural integrity in flue gas desulfurization (FGD) systems, phosphoric acid processing, offshore engineering systems, and highly corrosive chemical production facilities.
904L Stainless Steel Pipe Suppliers and Manufacturers
Our supplied 904L steel pipes are manufactured strictly in accordance with ASTM B677 (seamless pipe) and ASTM B673/B674 (welded pipe) standards, achieving annealed yield strength (Rp0.2) of 220 MPa, tensile strength (Rm) of 490 MPa, and elongation after fracture (A) greater than 35%. Covering various nominal specifications from Schedule 10S to Schedule 80S, they maintain structural integrity over a wide temperature range from cryogenic temperatures up to 400°C. Every steel pipe undergoes 100% Positive Material Identification (PMI), eddy current/ultrasonic Non-Destructive Testing (NDT), and hydrostatic pressure testing, accompanied by complete EN 10204 3.1 quality certificates.
904L Super Austenitic Stainless Steel Pipe specification
| Feature | Details |
| Grade | 904L / Super Austenitic |
| UNS Designation | N08904 |
| EN Designation | 1.4539 (X1NiCrMoCu25-20-5) |
| Standard (Seamless) | ASTM B677 / ASME SB677 |
| Standard (Welded) | ASTM B673, B674 / ASME SB673, SB674 |
| General Pipe Specs | ASTM A312 / ASME SA312 |
| Outer Diameter (OD) | 6mm to 630mm (1/8" to 24") |
| Wall Thickness (WT) | 0.5mm to 30mm (SCH 5S, 10S, 40S, 80S, etc.) |
| Length | Standard 6m, 12m or customized |
| Surface Finish | Annealed & Pickled, Bright Annealed, Polished |
Chemical Composition (%)
The high Nickel and Molybdenum content, combined with the addition of Copper, provides exceptional resistance to strong reducing acids.
| Element | Content (%) |
| Chromium (Cr) | 19.0 – 23.0 |
| Nickel (Ni) | 23.0 – 28.0 |
| Molybdenum (Mo) | 4.0 – 5.0 |
| Copper (Cu) | 1.0 – 2.0 |
| Carbon (C) | 0.020 max |
| Manganese (Mn) | 2.00 max |
| Silicon (Si) | 1.00 max |
| Phosphorus (P) | 0.045 max |
| Sulfur (S) | 0.035 max |
Mechanical Properties (At Room Temperature)
As an austenitic grade, 904L maintains high ductility and toughness even at cryogenic temperatures.
| Property | Metric Value |
| Tensile Strength (UTS) | ≥ 490 MPa |
| Yield Strength (0.2% Offset) | ≥ 220 MPa |
| Elongation (in 50mm) | ≥ 35% |
| Hardness (Rockwell B) | 70 – 90 HRB |
| Hardness (Brinell) | 150 – 190 HBW |
904L Stainless Steel Corrosion Resistance Performance
| Performance Metric | Details |
| PREN Value | 34 – 36 (Formula:Cr+3.3Mo+16N) |
| Sulfuric Acid (H2SO4) | Excellent resistance across the entire concentration range up to 35°C. |
| Chloride Pitting | Superior to 316L; resistant to pitting in seawater and brackish water. |
| Stress Corrosion (SCC) | Highly resistant due to the high Nickel content (25%). |
| Intergranular Corrosion | Very low risk due to extremely low carbon content (0.020%). |
904L Stainless Steel pipe Applications:
Chemical Processing: Equipment for the production of sulfuric, phosphoric, and acetic acids.
Oil & Gas: Piping for sour gas service and offshore platforms.
Pollution Control: Scrubbing systems for coal-fired power plants (Flue Gas Desulfurization - FGD).
Marine: Seawater cooling systems, desalination plants, and heat exchangers.
Pharmaceutical: Production of highly pure chemical compounds and medicines.
If you are planning a project,
please let me know the specific chemicals or fluids the piping will transport, as well as the operating temperature and pressure.
I can help determine whether 904L is suitable or if a more cost-effective alternative-such as duplex stainless steel-would meet your requirements.
SS 904L Pipe HS Code
| Product | Material / Grade | Product Type | HS Code (6-Digit) |
|---|---|---|---|
| 904L Stainless Steel Pipe | UNS N08904 / EN 1.4539 | Seamless Pipe | 7304.41 |
| 904L Stainless Steel Pipe | UNS N08904 / EN 1.4539 | Welded Pipe | 7306.40 |
Quality Inspection
Inspection parameters include tensile strength, yield strength, elongation, hardness, dimensions, and visual appearance; for ASTM A312 standard pipes, hydrostatic testing or non-destructive electric testing is also required. For service in harsh acidic or chloride-containing environments, additional tests-such as ASTM A262 intergranular corrosion testing and specific corrosion tests like ASTM G48-can be performed. Each shipment is accompanied by an EN 10204 3.1 Material Test Certificate (MTC) and heat number traceability records.
Standard Packaging
Pipes are typically supplied in securely strapped bundles with plastic protective caps on the ends and wrapped in polyethylene (PE) film or waterproof material to minimize moisture exposure during container transport. For long-distance shipments or those involving multiple transshipments, additional protection such as wooden supports, pallets, or export-grade wooden crates can be provided.
FAQ
Q: How should one choose between 904L and 316L for corrosive environments?
A: 316L: Suitable for general chemical processing, food industry applications, fresh water, and mildly corrosive environments.
904L: An upgrade to 904L is necessary when the environment involves warm concentrated acids, high chloride ion concentrations (such as seawater or brine), or conditions where 316L is prone to pitting and crevice corrosion.
Q: Is 904L magnetic? How does this affect its application?
A: It is completely non-magnetic. Even after cold working, 904L retains a stable austenitic structure and exhibits virtually no magnetism.
Q: Can 904L be used in seawater environments?
A: 904L performs excellently in ambient-temperature seawater, outperforming 316L. However, in high-temperature seawater (such as circulating cooling water in certain chemical plants), duplex steel 2507 or super-austenitic steel 254SMO may offer more robust performance. Nevertheless, for most marine architectural features, coastal structures, or ambient-temperature seawater systems, 904L piping is an ideal high-end choice.
Q: Why is 904L so much more expensive than 316L?
A: Nickel content: 316L contains approximately 10–12% nickel, whereas the nickel content in 904L is more than double, at 23–28%. Nickel is an expensive metal.
Molybdenum and copper: High molybdenum content and the specific addition of copper increase raw material costs.
Processing difficulty: Producing 904L seamless pipe places extremely high demands on hot-working processes, resulting in a relatively lower yield rate.
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