Excellent Corrosion Resistance of Incoloy 825
Incoloy 825 is a nickel-iron-chromium alloy with additions of molybdenum, copper, and titanium. It offers exceptional resistance to a wide range of corrosive environments, including sulfuric, phosphoric, nitric, hydrofluoric acids, and seawater. It is widely used in chemical processing, marine, pollution control, and nuclear industries.
What is Incoloy 825?
Incoloy 825 (UNS N08825) is a solid-solution-strengthened nickel-based alloy designed for exceptional corrosion resistance in harsh environments. Its high nickel content provides resistance to chloride-induced stress corrosion cracking; chromium improves resistance to oxidizing agents, and molybdenum and copper enhance resistance to reducing environments such as sulfuric acid. It is ideal for use in pickling, wastewater treatment, and sour gas conditions.
Incoloy 825 Equivalent Grades
| Standard | Equivalent Grade |
| UNS | N08825 |
| W.Nr. | 2.4858 |
| ASTM | B424 / B564 / B705 / B366 |
| JIS | NCF825 |
| ISO / EN | NiCr21Mo |
Incoloy 825 Chemical Composition (Typical Range)
| Element | Content (%) |
| Nickel (Ni) | 38.0 – 46.0 |
| Iron (Fe) | Balance |
| Chromium (Cr) | 19.5 – 23.5 |
| Molybdenum (Mo) | 2.5 – 3.5 |
| Copper (Cu) | 1.5 – 3.0 |
| Titanium (Ti) | 0.6 – 1.2 |
| Manganese (Mn) | ≤ 1.0 |
| Silicon (Si) | ≤ 0.5 |
| Carbon (C) | ≤ 0.05 |
| Sulfur (S) | ≤ 0.03 |
Incoloy 825 Mechanical Properties (Annealed, Room Temperature)
| Property | Typical Value |
| Tensile Strength | ≥ 550 MPa |
| Yield Strength (0.2%) | ≥ 220 MPa |
| Elongation | ≥ 30% |
| Brinell Hardness | ≤ 200 HB |
Incoloy 825 Physical Properties
| Property | Value |
| Density | 8.14 g/cm³ |
| Melting Range | 1370–1400 °C |
| Thermal Conductivity | 10.6 W/m·K |
| Electrical Resistivity | ~1.03 μΩ·m |
| Specific Heat | 0.44 J/g·K |
| Magnetic Properties | Non-magnetic |
Applications of Incoloy 825
- Equipment used in sulfuric, phosphoric, nitric, and organic acid production
- Pickling tanks, acid storage vessels, and heat exchangers
- Seawater desalination systems and marine structures
- Sour gas pipelines in petrochemical facilities
- Radioactive waste tanks and nuclear fuel reprocessing
- Flue gas scrubbers, ducting, and absorption towers
Advantages of Incoloy 825
- Excellent resistance to both oxidizing and reducing acids
- Strong resistance to pitting, crevice corrosion, and stress corrosion cracking
- High stability in sulfur- and chloride-rich environments
- Good weldability and formability (both hot and cold)
- Suitable for use in a wide range of acids at varying concentrations and temperatures
Limitations of Incoloy 825
- Not suitable for long-term service above 540 °C due to potential phase precipitation
- Higher cost compared to stainless steels like 304/316
- Strength decreases significantly at very high temperatures
- Lower pitting resistance than higher-grade alloys like Hastelloy C276
FAQ About Incoloy 825
Yes. It has excellent resistance to pitting and crevice corrosion in seawater, making it ideal for condensers, heat exchangers, and submerged marine equipment.
Incoloy 825 is better for mid-temperature, strong acid corrosion; Inconel 625 is stronger at high temperatures. Incoloy 825 is also more cost-effective.
It is highly resistant to sulfuric, phosphoric, nitric, hydrofluoric acids, and chloride-bearing environments—perfect for pickling and acid storage.
Yes. It offers good weldability using filler metals like ERNiFeCr-1 or ERNiCrMo-3. Heat input should be properly controlled to avoid defects.
Summary
This article introduces Incoloy 825, explains the alloy, and discusses its composition, properties, and applications. For more information about Incoloy 825, please get in touch with an MT.BOLTS representative.
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