904L Stainless Steel Plate

904L stainless steel plates are not merely corrosion-resistant—they’re chemical warfare specialists. With a rare 23% nickel, 4.5% molybdenum, and 1.6% copper, this super-austenitic alloy laughs at sulfuric acid, seawater pitting, and chloride stress corrosion cracking. Designed to outperform 316L by 5x in salt spray tests, 904L plates are the clandestine heroes of offshore oil platforms, pharmaceutical reactors, and uranium processing plants.

Why 904L Dominates Extreme Environments

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.”

Common Surfaces

Stainless Steel Standards Comparison Table