1.4539 Stainless Steel Composition & Super‑Austenitic Corrosion Resistance

1.4539 (X1NiCrMoCuN25‑20‑7) is a super‑austenitic stainless steel grade under EN 10028‑7 and EN 10088‑2, equivalent to 904L. With 19–23% chromium, 23–28% nickel, 4–5% molybdenum, and added copper, it offers exceptional corrosion resistance in highly aggressive environments. The grade performs reliably in sulfuric acid, phosphoric acid, chloride‑rich media, seawater, and strong oxidizing conditions. It is widely used in chemical reactors, marine equipment, pickling systems, pharmaceutical installations, and premium architectural structures. Weldability is good, though strict process control is recommended to maintain microstructural stability. 1.4539 is supplied as plates, tubes, bars, and strips. It is the preferred upgrade when 316/317 stainless steels cannot meet corrosion requirements, providing superior safety margins in extreme corrosive environments.