EN 10253-2 Type BAlloy 825 · NiCr21MoPRE ~32 · NACE MR0175
2.4858 (Alloy 825) Pipe Fittings
EN 10253-2 Type B buttweld pipe fittings in 2.4858 — Alloy 825 / Incoloy 825 (NiCr21Mo, N08825). A nickel-iron-chromium alloy with molybdenum, copper, and titanium additions. PRE ~32. The high nickel content (38–46%) provides SCC resistance in H₂S-containing environments per NACE MR0175, while Mo and Cu give resistance to sulphuric and phosphoric acids. Cost-positioned between 316L (too low PRE for sour gas) and Inconel 625 (PRE ~51, higher cost).
PRE (approx.)
~32
Ni Content
38–46%
ASTM UNS
N08825
Chemistry (ASTM B366 / EN equivalent)
Element
Min
Max
Role
Ni (Nickel)
38.0%
46.0%
SCC immunity in H₂S per NACE MR0175
Cr (Chromium)
19.5%
23.5%
Passive film and pitting resistance
Mo (Molybdenum)
2.5%
3.5%
PRE contribution; acid resistance
Cu (Copper)
1.5%
3.0%
Reducing acid resistance (H₂SO₄, H₃PO₄)
Ti (Titanium)
0.6%
1.2%
Stabilisation — prevents sensitisation
Fe (Iron)
22% min
—
Balance
Alloy 825 vs Competing Grades
Grade
PRE
Ni %
NACE MR0175
Cu
Best Use
316L (1.4404)
~24
10–14%
Limited
None
Mild service
Alloy 825 (2.4858)
~32
38–46%
Yes
1.5–3%
Sour gas + mild acid — intermediate cost
Duplex 2205 (1.4462)
≥35
4.5–6.5%
Yes (limited)
None
Chloride pitting; no acid need
Inconel 625 (2.4856)
~51
≥58%
Yes
None
Aggressive seawater/mixed acid — higher cost
Cross-References
W.Nr.
2.4858
EN Name
NiCr21Mo
ASTM UNS
N08825
Trade Name
Incoloy 825 / Alloy 825
Welding
Filler: ERNiCrMo-3 (Inconel 625 filler) commonly used. Dedicated Alloy 825 filler (ERNiFeCr-1) also available. No PWHT required.
