Specification Sheet: Alloy 904L (UNS N08904) W. Nr. 1.4539 A Superaustenitic Stainless Steel Designed for Corrosion and Pitting Resistance in a Wide Range of Process Environments

Alloy 904L (UNS N08904) is a superaustenitic stainless steel that is designed for moderate to high corrosion resistance in a wide range of process environments. The combination of high chromium and nickel content, coupled with additions of molybdenum and copper, assure good to excellent corrosion resistance.

With its highly alloyed chemistry—25% nickel and 4.5% molybdenum, 904L provides good chloride stress corrosion cracking resistance, pitting and general corrosion resistance superior to 316L and 317L molybdenum enhanced stainless steels.

Alloy 904L was originally developed to withstand environments containing dilute sulfuric acid. It also offers good resistance to other inorganic acids such as hot phosphoric acid as well as most organic acids.

Alloy 904L is easily welded and processed by standard shop fabrication practices.

Applications :

• Air Pollution Control— scrubbers for coal-fired power plants
• Chemical Processing—process equipment for the production of sulfuric, phosphoric, inorganic and organic acids and the production of phosphate-based fertilizers
• Metallurgical Processing— pickling equipment using sulfuric acid
• Oil and Gas Production— offshore process equipment
• Pharmaceutical Industry— process equipment
• Pulp and Paper—processing equipment
• Seawater and Brackish Water— condensers, heat exchangers and piping systems

Standards :

• ASTM …………… A 240, B 625
• ASME …………… SA 240, SB 625

Chemical Analysis :

Weight % (all values are maximum unless a range is otherwise indicated)

• Nickel : 23.0 min. – 28.0 max.
• Silicon : 1.00
• Chromium : 19.0 min. – 23.0 max.
• Phosphorus : 0.045
• Molybdenum : 4.0 min.– 5.0 max.
• Sulfur : 0.035
• Copper : 1.0–2.0 max.
• Iron : Balance
• Manganese : 2.00