SS904L is a high-alloy austenitic stainless steel with about 20% chromium, 25% nickel, 4.5% molybdenum and some copper. It resists sulphuric and phosphoric acids, seawater and chloride pitting far better than SS316L. It is used in chemical and fertiliser plants, acid handling, heat exchangers and seawater equipment.
Quick facts
- Type
- Super austenitic stainless steel
- Nickel
- About 23–28%
- Molybdenum
- About 4–5%
- Copper
- About 1–2%
- Magnetic
- No
- Weldability
- Good, with matching filler
Equivalent grades
| Standard | Grade |
|---|---|
| ASTM | 904L |
| EN | 1.4539 (X1NiCrMoCu25-20-5) |
| UNS | N08904 |
Equivalents are close, not identical. Name the grade and standard on the drawing.
Typical chemical composition
| Element | % |
|---|---|
| Carbon (C) | 0.02 max |
| Chromium (Cr) | About 19–23 |
| Nickel (Ni) | About 23–28 |
| Molybdenum (Mo) | About 4–5 |
| Copper (Cu) | About 1–2 |
Values are typical. The exact limits depend on the standard and supplier; ask for the mill test certificate when it matters.
SS904L or SS316L?
| SS904L | SS316L | |
|---|---|---|
| Acid resistance | Much better | Good |
| Chloride pitting | Much better | Moderate |
| Cost | Much higher | Lower |
| Typical use | Acid plants, seawater | Food, pharma, marine |
Need parts made in SS904L stainless steel?
Post your requirement free. Workshops that take your kind of work see it and get in touch. You only talk to the ones that fit.
Get startedRelated
Related job work
Machines
Questions
- Why is SS904L so expensive?
- It contains about three times the nickel of SS304 plus molybdenum and copper, all costly alloying elements.
- Is SS904L better than duplex 2205?
- 904L resists strong acids better; duplex 2205 is about twice as strong and often cheaper for chloride service.
- Is SS904L magnetic?
- No, it is fully austenitic and non-magnetic.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 23 October 2026.