When Standard Stainless Steel Isn't Enough
In aggressive chemical processing environments — particularly those involving sulfuric acid, phosphoric acid, or mixed acid systems — standard austenitic grades like 304L and 316L may not provide adequate corrosion resistance. This is where SS 904L (UNS N08904) and nickel alloy seamless pipes become essential.
SS 904L: The Cost-Effective Super Austenitic Solution
904L bridges the gap between standard austenitic stainless steels and expensive nickel alloys. With 4-5% molybdenum, 1-2% copper, and 23-28% nickel, it offers:
- Sulfuric acid resistance: Excellent at concentrations from 0-85% at temperatures up to 40°C
- Phosphoric acid resistance: Superior to 316L in all concentrations
- Chloride resistance: Significantly better than 316L (PREN ~36)
- Stress corrosion cracking resistance: Outstanding in chloride environments
Applications by Industry
Fertilizer Plants (Middle East & India)
Saudi Arabia, Qatar, and Oman are major fertilizer producers. 904L is specified for phosphoric acid evaporators, sulfuric acid piping, and acid storage systems. Stancor supplies to SABIC, Ma'aden, and QAFCO projects.
Mining & Mineral Processing (Europe & Americas)
Acid leaching circuits, autoclave piping, and process water systems in copper, nickel, and gold mining operations.
Flue Gas Desulfurization (Global)
Power plant FGD systems handling hot, acidic condensate require 904L or higher alloys.
Available Grades from Stancor
- SS 904L (UNS N08904) — The versatile super austenitic workhorse
- SS 316L — For less aggressive acid environments
- SS 310S — For high-temperature sulfidation resistance
Our metallurgists can recommend the most cost-effective grade for your specific acid concentration and temperature conditions. Contact us for a free material consultation.