SS 904L Pipe Supplier in India — Super Austenitic Acid Resistant

SS 904L was specifically designed for sulphuric acid service where 316L fails. The key advantages are: higher molybdenum (4.5% vs 2.5%) gives far better pitting and crevice corrosion resistance, copper addition (1.5%) provides specific resistance to hot concentrated sulphuric acid, and higher nickel (25% vs 10%) improves resistance to stress corrosion cracking. The PREN (Pitting Resistance Equivalent Number) of 904L is approximately 36 compared to 316L's 25. In sulphuric acid above 60% concentration and 40°C, 316L corrodes rapidly while 904L remains resistant.

SS 904L shows excellent resistance to sulphuric acid across a wide range of concentrations. At room temperature, it resists all concentrations from 0-98%. At elevated temperatures (up to 80°C), it handles concentrations up to about 70% effectively. In hot concentrated H2SO4 (above 80°C), its resistance depends on velocity and aeration conditions. The copper content specifically improves performance in reducing acid environments. For concentrations above 90% at temperatures above 100°C, Hastelloy C-276 may be needed. Creative Metal Industries can help with material selection based on your exact operating conditions.

SS 904L has a PREN (Pitting Resistance Equivalent Number) of approximately 36, calculated as %Cr + 3.3(%Mo) + 16(%N) = 20 + 3.3(4.5) + 16(0.05) ≈ 36. This is significantly higher than 316L (PREN ~25) and approaches duplex 2205 (PREN ~35). PREN predicts resistance to pitting corrosion in chloride environments — higher is better. A PREN above 32 is generally considered resistant to seawater pitting. This makes 904L suitable for seawater cooling systems, chloride-containing chemical processes, and offshore applications.

SS 904L costs approximately 40-50% less than Hastelloy C-276 while providing adequate performance for many acid service applications. Hastelloy C-276 is superior in hot concentrated acids and mixed acid environments, but 904L is sufficient for most sulphuric acid plants, phosphoric acid production, and seawater applications. This makes 904L a cost-effective alternative to exotic nickel alloys where the operating conditions are within its corrosion resistance envelope. Contact CMI at +91 99982 80619 for comparative pricing and material selection guidance.

Creative Metal Industries stocks SS 904L seamless pipes from 1/2 inch (15NB) to 12 inches (300NB) in schedules SCH 10S, 20S, 40S, and 80S per ASTM A312 TP904L. Welded pipes are available from 2 inches to 12 inches. Standard lengths are 5-7 metres (random length). We also stock 904L tubes per ASTM A213 in OD 12.7mm to 114.3mm for heat exchanger applications. Fittings (elbows, tees, reducers) and flanges in 904L are also available to complete your project requirements.