Nickel-iron-chromium alloy with Mo, Cu & Ti — engineered for sour gas and acid service
Inconel 825 is a stabilized nickel-iron-chromium alloy with molybdenum, copper, and titanium additions. It provides exceptional resistance to sulfuric acid, phosphoric acid, sour gas (H₂S), and seawater. The titanium stabilization prevents sensitization and intergranular corrosion after welding.
| Element | Min % | Max % |
|---|---|---|
| Nickel (Ni) | 38.0 | 46.0 |
| Chromium (Cr) | 19.5 | 23.5 |
| Iron (Fe) | 22.0 | — |
| Molybdenum (Mo) | 2.5 | 3.5 |
| Copper (Cu) | 1.5 | 3.0 |
| Titanium (Ti) | 0.6 | 1.2 |
| Aluminum (Al) | — | 0.2 |
| Carbon (C) | — | 0.05 |
| Property | Value |
|---|---|
| Tensile Strength | ≥ 585 MPa |
| Yield Strength (0.2%) | ≥ 241 MPa |
| Elongation | ≥ 30% |
| Hardness | ≤ 200 HB |
| Max Service Temp | 540°C |
| Environment | Resistance | Notes |
|---|---|---|
| Sulfuric acid (all concentrations) | Excellent | Up to 80°C |
| Phosphoric acid | Excellent | All concentrations |
| Sour gas (H₂S / wet) | Excellent | NACE MR0175 approved |
| Seawater | Excellent | Crevice corrosion resistant |
| Nitric acid | Good | Moderate concentrations |
| Acetic acid | Good | All concentrations |
| Hydrofluoric acid | Excellent | Gas dealkylation service |
| Form | Specification | Size Range | Stock |
|---|---|---|---|
| Plate / Sheet | ASTM B424, AMS 5871 | 0.5–50mm x 1000–1500mm | In Stock |
| Seamless Pipe | ASTM B423, ASME SB-423 | 6–168mm OD | In Stock |
| Welded Pipe | ASTM B705, B775 | 15–610mm OD | In Stock |
| Bar | ASTM B425, AMS 5871 | 10–150mm dia. | In Stock |
| Fittings/Flanges | ASME B16.9 / B16.5 | All sizes | On request |
Sour Gas Processing: Christmas tree components, wellhead equipment, flowlines, gathering systems. NACE MR0175 compliant for pH₂S > 0.05 kPa.
Chemical Processing: Sulfuric acid storage tanks, phosphoric acid evaporators, pickling equipment, acid regeneration plants.
Offshore & Marine: Seawater heat exchangers, risers, topside process piping.
Pollution Control: Flue gas desulfurization (FGD) slurry pipelines, wet scrubbers.
Nuclear: Fuel element process solutions, reactor coolant systems.
| Factor | 825 | 316L | C276 |
|---|---|---|---|
| Sour gas (H₂S) | Excellent | Limited | Excellent |
| Sulfuric acid (reducing) | Excellent | Poor | Excellent |
| Phosphoric acid | Excellent | Good | Good |
| Seawater (crevice) | Excellent | Poor | Excellent |
| Price vs 316L | +40–60% | Baseline | +200%+ |
| Cost vs C276 | Baseline | —80% | Reference |
Choose 825 when: acid gas, sulfuric acid, phosphoric acid, seawater, budget-conscious sour service projects. Better value for reducing acid environments.
Choose 625 when: higher temperature (> 500°C), higher strength requirements, oxidizing acid environments, aerospace applications.
Send your spec — we reply within 24h with mill cert and pricing
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