Alloy 825
Also known as Incoloy® 825, UNS N08825, Werkstoff 2.4858
Alloy 825 is a nickel-iron-chromium alloy resisting reducing and oxidising acids and chloride stress-corrosion cracking.
Alloy 825 (UNS N08825) is a Nickel-Iron-Chromium alloy with additions of Molybdenum, Copper and Titanium, providing outstanding resistance to corrosion in both reducing and oxidising environments. It resists sulphuric and phosphoric acids across a wide range of concentrations and temperatures, and offers excellent pitting, crevice corrosion and stress corrosion cracking resistance in chloride environments.
Listed in NACE MR0175 / ISO 15156 for sour service. Available as standard annealed bar, HS110 high-strength cold-worked bar and annealed tube. We stock bar in the UK and USA, with annealed tube also stocked. Plate and fittings are available on enquiry; forgings and castings to order.
- Outstanding resistance to both reducing and oxidising acids
- Excellent resistance to pitting and crevice corrosion in chloride environments
- Resistant to stress corrosion cracking
- NACE MR0175 approved for sour service
- Available as high-strength HS110 cold-worked bar for demanding structural applications
| Element | Min | Max |
|---|---|---|
| Nickel (Ni) | 38.0 | 46.0 |
| Iron (Fe) | 22.0 | |
| Chromium (Cr) | 19.5 | 23.5 |
| Molybdenum (Mo) | 2.50 | 3.50 |
| Copper (Cu) | 1.50 | 3.00 |
| Titanium (Ti) | 0.60 | 1.20 |
| Manganese (Mn) | - | 1.00 |
| Silicon (Si) | - | 0.50 |
| Carbon (C) | - | 0.05 |
| Sulphur (S) | - | 0.03 |
| Aluminium (Al) | - | 0.20 |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 35 ksi | 241 N/mm² |
| Tensile strength (min) | 86 ksi | 590 N/mm² |
| Elongation (5.65√S0 & 4D) | 30% | |
| Reduction of area | 40% | |
| Hardness (Brinell) | ≤ 327 HB |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress | 110-140 ksi | 758-965 N/mm² |
| Tensile strength (min) | 115 ksi | 793 N/mm² |
| Elongation (5.65√S0 & 4D) | 11% | |
| Hardness (Rockwell C) | 35 |
| Property | Value |
|---|---|
| Density (kg/m³) | 8140 |
| Magnetic permeability (20°C) | 1.005 |
| Curie temperature (°C) | -196 |
| Young's modulus (kN/mm²) | 196 |
| Specific electrical resistance, 20°C (µΩ.m) | 1.13 |
| Mean coefficient of thermal expansion, 20-100°C (m/m/°C) | 14.1 x 10⁻⁶ |
| Specific heat, 20°C (J/kg.K) | 440 |
| Thermal conductivity, 20°C (W/m.K) | 10.8 |
Equivalents & cross-references
Standard designations
- UNS
- N08825Unified Numbering System
- Werkstoff
- 2.4858German/European material number
- ASTM
- B425Rod and bar
- BS
- 3076 NA16British Standard nickel alloy NA16
- NACE
- MR0175 / ISO 15156Sour service
Alloy 825 is also designated UNS N08825, Werkstoff 2.4858, ASTM B425, BS 3076 NA16 and NACE MR0175 / ISO 15156.
Trade name equivalents
-
Incoloy 825
Special Metals Corporation
Incoloy 825 is a trade name of Special Metals Corporation for Alloy 825.
Common questions
What is the UNS number for Alloy 825?
Alloy 825 is a nickel-iron-chromium alloy with molybdenum, copper and titanium additions (NiCr21Mo), covered by UNS N08825, Werkstoff No. 2.4858, ASTM B425 and BS3076 NA16, and listed in NACE MR0175/ISO 15156. It is supplied in the hot worked and annealed condition and can be significantly strengthened through cold working. Langley Alloys stocks it as bar and tube; plate and fittings are available on enquiry, and forgings and castings are to order.
What is Alloy 825 used for?
Alloy 825 is used for chemical process equipment, pollution control systems and wet scrubbers, waste heat recovery exchangers, tanks, vessels and agitators, downhole equipment for corrosive and sour service, and nuclear reprocessing and handling. It achieves good mechanical properties from cryogenic to medium-high temperatures up to 540°C.
Is Alloy 825 suitable for acids and sour service?
Yes. Alloy 825's high nickel content ensures resistance to stress corrosion cracking, while molybdenum and copper strongly resist reducing environments such as sulphuric and phosphoric acids, chromium resists oxidising environments such as nitric acid, and titanium inhibits intergranular corrosion. It offers overall resistance to pitting and crevice corrosion and is listed in NACE MR0175/ISO 15156 for corrosive and sour service, with a seawater corrosion rate below 0.01 mm/year.
What is Werkstoff 2.4858?
Werkstoff No. 2.4858 is the German/European material number for UNS N08825, a nickel-iron-chromium alloy with molybdenum and copper additions for improved corrosion resistance. Langley Alloys stocks this grade as Alloy 825 to ASTM B425 and NACE MR0175/ISO 15156.
What is the density of Alloy 825?
Alloy 825 has a density of approximately 8.14 g/cm³ (8140 kg/m³).
Is Alloy 825 magnetic?
Effectively no. Alloy 825 has a very low magnetic permeability (around 1.005) and is treated as non-magnetic for most purposes.
Dependable resistance to acids and alkalis
In this Technical Corner, Rodney introduces Alloy 825 as an entry-level nickel alloy, around 40% nickel against the 50 to 60% of grades like 718 and 725.
Developed for sulphuric acid environments, it serves chemical processing, fertiliser, battery production and dyes, much of it pipework. The focus is not strength but dependable resistance to acids and alkalis, with ready availability.
Visit our YouTube channelStandard bar supplied in the hot worked and annealed condition; HS110 high-strength bar supplied cold worked and stress relieved. Each bar ultrasonically tested and visually inspected.
Tools for this grade
Sour-service screen (NACE MR0175)
Sour-Service Screen
Work out whether a service is sour from the H2S partial pressure, and see each alloy's NACE MR0175 / ISO 15156 status and hardness limit. A first-pass screen for oil & gas material selection - the full environmental envelope for a grade is set in ISO 15156-3 Annex A.
Candidate grade
| Grade | Family | NACE status | Hardness limit |
|---|
First-pass screen only. This shows whether the service is sour (from H2S partial pressure) and each material group's NACE MR0175 hardness limit and general suitability. It does not reproduce the full environmental windows (maximum H2S partial pressure, temperature, chloride, in-situ pH per grade) - those are in ISO 15156-3 Annex A and must be checked there for the specific grade, product form and condition. Qualification also depends on heat treatment, cold work and welding.
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