Stainless Steel 904L (UNS N08904)
SS 904L is a high-alloy super-austenitic stainless steel engineered with 25% nickel, 4.5% molybdenum, and 1.5% copper. The copper addition imparts unique resistance to sulfuric, phosphoric, and organic acids, while the high nickel and molybdenum content provides outstanding immunity to chloride stress corrosion cracking.
Material Quick Reference
| Material Classification | Super-Austenitic Stainless Steel (High Ni-Cr-Mo-Cu) |
|---|---|
| Pitting Resistance (PREN) | 34 - 36 |
| Temperature Limits | -50°C to +400°C |
| Governing Specifications | ASTM B677 (Pipe), ASTM B366 (Fittings), ASTM B649 (Forgings), ASME B31.3 |
Typical Engineering Applications
- Sulfuric acid handling and concentration plants
- Seawater heat exchangers and piping
- Flue gas desulfurization (FGD) scrubbers
- Fertilizer phosphoric acid synthesis loops
Chemical Environment & Corrosion Resistance
Exceptional resistance across the full concentration range of sulfuric acid up to 35°C, and resistant to warm brackish water.
Performance in Qatar's Coastal & Industrial Climate
Widely used in Mesaieed chemical plants and fertilizer complexes for sulfuric and phosphoric acid piping.
Welding & Fabrication Guidelines
Welded with matching ERNiCrMo-3 (Inconel 625) or matching 904L consumables under strict low heat input (< 1.0 kJ/mm).
Positive Material Identification (PMI) Requirements
XRF verification: 23–28% Ni, 19–23% Cr, 4–5% Mo, 1–2% Cu.
Key Advantages
- Immune to chloride SCC in warm waters
- Superior acid corrosion resistance vs 316L
- Fully austenitic (non-magnetic)
Engineering Limitations
- High cost compared to duplex alloys; lower mechanical yield strength than Duplex 2205
Related Products & Contracting Services
Request a Quote for Stainless Steel 904L (UNS N08904)
Submit your piping schedule, isometric drawings, or material take-offs. Our technical engineering team evaluates specifications to deliver accurate pricing and execution schedules.