Description
Why 904L Dominates Extreme Environments
| Threat |
904L Plate |
316L |
6% Mo Alloys |
| Sulfuric Acid (50%) |
Safe up to 40°C |
Fails at 25°C |
Safe up to 35°C |
| Chloride Pitting Temp |
60°C (ASTM G48 Method A) |
25°C |
45°C |
| Cost per Ton |
$18.500 |
$5.800 |
$22.000 |
Key Specifications
Composition: 20% Cr / 23% Ni / 4.5% Mo / 1.6% Cu (UNS N08904 compliant)
PREN Value: 36+ (vs. 28 for 316L) due to Mo-Cu synergy
Surface Finishes: 2B mill, electropolished (Ra ≤0.1 µm for FDA/GMP compliance)
Industry-Specific Dominance
1. Chemical & Petrochemical
Sulfuric acid concentrators | Phosphoric acid evaporators | Chlorine dioxide reactors
2. Offshore & Marine
Seawater piping systems | Subsea valve bodies | LNG heat exchanger plates
3. Nuclear & Energy
Uranium enrichment centrifuges | Geothermal brine condensers | Flue gas scrubber liners
4. Pharmaceutical
High-purity API reactors | Vaccine purification columns | CIP (Clean-in-Place) system manifolds
Fabrication Mastery
Welding Protocol:
Filler Metals: ER385 or NIMO-Cr27Mo7Cu3 for critical welds | Strict interpass temp <100°C
Gas Shielding: 98% Ar + 2% N₂ for TIG welding to prevent sigma phase formation
Machining Tips:
Use carbide tools with 10° positive rake | Lubricate with chlorinated-free oils
Post-Treatment:
Electrolytic pickling (HNO₃ + HF) to restore passive layer | Passivation per ASTM A967
Global Proof of Unyielding Performance
Shell Offshore: “904L plates in seawater pumps showed zero pitting after 10 years in 35.000 ppm chlorides.”
Pfarma Global: “CIP manifolds passed 1.000+ sterilization cycles with no intergranular attack.”
Chilean Copper Mine: “904L acid leaching tanks outlasted 317L by 300% in 30% H₂SO₄ at 50°C.”
