What Alloy 825 is
Alloy 825 is a nickel-iron-chromium alloy with molybdenum, copper, and titanium. The nickel gives chloride stress corrosion immunity, the molybdenum and copper give resistance to reducing acids such as sulfuric and phosphoric, the chromium handles oxidizing conditions, and the titanium stabilizes it against sensitization during welding. It is a more economical alternative to C-276 and 625 where the environment is aggressive but not extreme.
Standards we supply to
- ASTM B163 / ASME SB-163, condenser and heat exchanger tube
- ASTM B423 / ASME SB-423, seamless pipe and tube
- ASTM B704 and B705 welded on request
Chemical composition
| Element | Requirement |
|---|---|
| Nickel | 38.0 to 46.0% |
| Chromium | 19.5 to 23.5% |
| Iron | 22.0% min |
| Molybdenum | 2.5 to 3.5% |
| Copper | 1.5 to 3.0% |
| Titanium | 0.6 to 1.2% |
| Carbon | 0.05% max |
Typical mechanical properties, annealed
| Property | Value |
|---|---|
| Tensile strength | 85,000 psi min (586 MPa) |
| Yield strength | 35,000 psi min (241 MPa) |
| Elongation in 2" | 30% min |
Where it is used
- Sour gas production tubing, downhole equipment, and gathering systems.
- Sulfuric acid coolers, pickling tanks, and heating coils.
- Phosphoric acid evaporators and fertilizer plant exchangers.
- Pollution control scrubbers and reheaters.
- Nuclear fuel reprocessing and radioactive waste handling.
- Oil and gas heat exchangers on produced water and CO2-rich streams.
OD, wall, length, quantity, ASTM B163 (heat exchanger) or B423 (pipe and tube), and the service: state acid type and concentration, or the NACE MR0175 sour service requirement and partial pressures.

