EN 1.4539 904L: Super Austenitic Steel Overview

Mar 18, 2026

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1.4539 stainless steel, widely known as 904L or UNS N08904, is a high-alloy, low-carbon austenitic stainless steel with exceptional corrosion resistance, particularly in sulfuric acid and chloride-containing environments. Distinguished by its high chromium, nickel, molybdenum, and copper content, it delivers superior performance where standard austenitic grades like 316L are inadequate. Its excellent resistance to both oxidizing and reducing acids makes it a premium material for critical applications in chemical processing, pharmaceutical, and pollution control industries.

Standard	Equivalent Grade
EN (Europe)	1.4539
ASTM/AISI (USA)	904L, UNS N08904
JIS (Japan)	SUS904L
Common Name	904L

Element	C	Si	Mn	P	S	Cr	Ni	Mo	Cu
Content (%)	≤ 0.02	≤ 1.0	≤ 2.0	≤ 0.045	≤ 0.035	19.0 - 23.0	23.0 - 28.0	4.0 - 5.0	1.0 - 2.0

Property	Yield Strength (Rp0.2)	Tensile Strength (Rm)	Elongation (A)	Hardness (HB)
Typical Value	≥ 220 MPa	490 - 690 MPa	≥ 35%	≤ 230

Outstanding Acid Resistance: Excels in resisting uniform corrosion from sulfuric, phosphoric, and acetic acids across a wide range of concentrations and temperatures, particularly in sulfuric acid up to 40°C at concentrations up to 95%.

High Alloy Content: The significant amounts of nickel, chromium, molybdenum, and copper work synergistically to handle both oxidizing and reducing environments.

Low Carbon & Good Weldability: The low carbon content (≤0.02%) minimizes carbide precipitation, and it can be welded using common techniques with matching high-alloy filler materials without post-weld heat treatment.

Excellent Chloride Resistance: Offers good resistance to chloride-induced pitting and crevice corrosion, with PREN typically 32-34.

Chemical Processing: Reactors, tanks, heat exchangers, and piping for producing and handling sulfuric acid, phosphoric acid, and other aggressive chemicals.

Pollution Control: Scrubbers, ducting, and chimney liners in flue gas desulfurization (FGD) plants.

Pharmaceutical: Equipment requiring high purity and resistance to cleaning agents and process chemicals.

Pulp & Paper: Bleaching equipment and handling systems for aggressive process streams.

Sea Water Applications: Heat exchangers and piping where resistance to brackish water or seawater is needed.

Oil & Gas: Sour gas processing equipment and components in corrosive environments.

The key differences are the much higher overall alloy content and the addition of copper. 904L contains significantly more chromium (19-23% vs. 16-18%), nickel (23-28% vs. 10-14%), and molybdenum (4-5% vs. 2-3%) than 316L, and its 1-2% copper content dramatically enhances its resistance to reducing acids like sulfuric acid. With PREN 32-34 vs. 316L's 24-26, 904L offers superior resistance to pitting and crevice corrosion. This makes 904L suitable for severe chemical environments where 316L would rapidly corrode, particularly in sulfuric acid service and where higher chloride levels are present at elevated temperatures.

Due to its high work hardening rate and toughness, 904L can be more challenging to machine and form than standard austenitic grades like 304 or 316. It requires powerful machinery, rigid setups, sharp cutting tools, and appropriate speeds and feeds. For forming, it may require more force and careful attention to springback due to its higher strength. However, with the correct techniques and tools, it can be successfully processed. In the annealed condition, it has good formability and can be bent, deep drawn, and fabricated using standard methods, though with higher power requirements than conventional austenitic grades.

904L has good weldability using common techniques including TIG, MIG, and SMAW. Matching filler metals (such as ER385 or 904L type) are recommended to maintain corrosion resistance in the weld zone. The low carbon content minimizes sensitization, so post-weld heat treatment is not required. However, care should be taken to control heat input (typically 0.5-2.0 kJ/mm) and interpass temperature (<150°C) to avoid excessive grain growth. Post-weld cleaning and pickling/passivation are recommended to restore the passive layer and ensure optimum corrosion resistance.

GNEE Steel stocks and supplies high-performance 904L (1.4539) stainless steel in plate, sheet, pipe, tube, bar, and fitting forms to meet the demands of the most corrosive applications. Our materials come with full traceability and certification (EN 10204 3.1). If you have any requirements, please feel free to contact us.