Key Feature

The High-Alloy Austenitic Corrosion-Resistant Pipe. Exceptional resistance to sulfuric acid, phosphoric acid, and chloride solutions, bridging the gap between stainless steels and nickel alloys.

The standard solution for severe corrosive applications, particularly sulfuric and phosphoric acid environments.

Common Designations

UNS N08904
ASTM B677 (Seamless/Welded Pipe)
EN 1.4539, X1NiCrMoCu25-20-5
Werkstoff Nr. 1.4539
Alloy 904L
F904L (Wrought product designation)

Often classified as a nickel-iron-chromium alloy due to high nickel content.

Chemical Composition (Typical wt.%)

C: ≤ 0.020
Cr: 19.0 - 23.0Ni: 23.0 - 28.0Mo: 4.0 - 5.0Cu: 1.0 - 2.0Mn: ≤ 2.00
Si: ≤ 1.00
P: ≤ 0.045
S: ≤ 0.035

High nickel (25%) + molybdenum (4.5%) + copper (1.5%) combination provides unique corrosion resistance.

Mechanical Properties

Tensile Strength: ≥ 490 MPa
Yield Strength: ≥ 220 MPa
Elongation: ≥ 35%
Hardness: ≤ 217 HB
Impact Toughness: Excellent at low temperatures

Good ductility and toughness despite high alloy content.

Corrosion Resistance

Exceptional: PREN*: 33-36
Superior resistance to: Sulfuric acid (all concentrations up to boiling), phosphoric acid, chloride solutions, organic acids, seawater.
Excellent resistance to stress corrosion cracking.

Copper addition enhances resistance to sulfuric acid; high Mo provides chloride resistance.

Physical Properties

Density: 8.00 g/cm³
Melting Range: 1300 - 1390 °C
Thermal Expansion: 15.9 × 10⁻⁶/K (20-100°C)
Thermal Conductivity: 12.5 W/m·K (100°C)
Non-magnetic when annealed

Higher density than conventional stainless steels due to high nickel content.

Pressure Ratings

Schedule 10S/40S: Standard process piping
Schedule 80S/160: High pressure service
ASME B31.3 compliant
Similar to 316L in mechanical strength

Adequate strength for most pressure applications despite lower yield strength.

Temperature Limits

Continuous Service: Up to 400°C (for corrosion)
Higher Temp: Up to 800°C (with property loss)
Cryogenic Service: Excellent to -196°C
Avoid: 600-900°C (precipitation risk)

Good low-temperature toughness; limited high-temperature corrosion service.

Welding Characteristics

Good weldability with proper procedures
Low carbon prevents sensitizationMatching or overmatched filler metalsHeat input control important
No post-weld annealing required

Similar welding characteristics to other high-alloy austenitic grades.

Key Standards

ASTM B677: Seamless & Welded Pipe (primary standard)
ASTM B674: Welded Pipe
ASTM B675: Welded Tubes
EN 10216-5: Seamless Pressure Tubes
NORSOK M-630: Offshore materials

Comprehensive standardization for quality assurance in critical applications.

Common Applications

• Sulfuric Acid Systems: Production, handling, and transport piping
• Phosphoric Acid Plants: Production equipment, evaporators, piping systems
• Chemical Processing: Reactor piping, acid transport, aggressive chemical lines
• Pollution Control: Flue gas desulfurization (FGD) systems, scrubber piping
• Offshore Oil & Gas: Seawater piping, topside process lines, injection systems
• Pulp & Paper: Digester piping, bleach plants, chemical recovery systems
• Pharmaceutical: Aggressive process piping, API manufacturing systems

Specifically selected for severe corrosive environments, particularly acid services.