Incoloy Alloy 825: A Corrosion-Resistant Nickel-Iron-Chromium Alloy

Incoloy Alloy 825 is a high-performance, corrosion-resistant alloy composed of nickel, iron, chromium, and molybdenum, designed for use in environments where materials are exposed to both high temperatures and aggressive corrosive conditions. It is particularly known for its resistance to a wide range of acids, including sulfuric acid, phosphoric acid, and organic acids, making it ideal for use in chemical processing, pollution control, and other industrial applications that involve harsh environments.

Key Properties of Incoloy Alloy 825:

1. Composition:

   • Nickel (Ni): 38–46%
   • Chromium (Cr): 19–23%
   • Iron (Fe): Balance
   • Molybdenum (Mo): 2.5–3.5%
   • Titanium (Ti): 0.6–1.2%
   • Copper (Cu): 1.5–3.0%
   • Small amounts of carbon, manganese, and other elements.

2. Excellent Corrosion Resistance: Alloy 825 offers outstanding resistance to a variety of corrosive environments, including:

   • Sulfuric acid (at concentrations up to 75% and at temperatures up to around 150°C).
   • Phosphoric acid.
   • Sea water and brine solutions.
   • Acidic gases, such as those found in sulfuric acid manufacturing and acid gas treatment.
   • Stress corrosion cracking (SCC) and intergranular corrosion in environments containing chlorides, thanks to its high nickel content and the presence of titanium, which stabilizes the alloy.

3. Good High-Temperature Performance:

   • Incoloy 825 can withstand temperatures up to approximately 1100°F (593°C) in continuous service, and its resistance to oxidation at elevated temperatures is excellent. This makes it suitable for use in both high-temperature and corrosive environments.

4. Fabricability:

   • Alloy 825 is easy to fabricate, weld, and form. Its ability to be welded and processed into complex shapes without significant degradation of its corrosion resistance makes it highly versatile for manufacturing large equipment and components for harsh environments.

5. Resistance to Corrosive Environments:

   • Incoloy 825 is particularly effective in environments where there is a combination of high temperature and corrosive media. Its ability to resist pitting, crevice corrosion, and stress corrosion cracking in acidic conditions makes it a popular choice in industries such as:
     • Chemical processing.
     • Pollution control equipment (e.g., flue gas desulfurization).
     • Marine environments.
     • Nuclear power plants (especially in equipment exposed to corrosive fluids).

6. Applications:

   • Chemical processing: Used in reactors, heat exchangers, and piping systems for sulfuric and phosphoric acid environments.
   • Marine environments: Employed in the production of seawater heat exchangers, desalination units, and other marine equipment.
   • Pollution control: Utilized in flue gas desulfurization units for controlling sulfur dioxide emissions.
   • Oil and gas: Applied in equipment exposed to aggressive chemical environments, including acid gas treatment systems.

7. Temperature Range: Incoloy 825 is suitable for use in a temperature range up to approximately 1100°F (593°C) under continuous service, and higher temperatures can be tolerated for short-term applications without significant degradation of mechanical properties.

Summary:

Incoloy Alloy 825 is a versatile, corrosion-resistant alloy known for its excellent resistance to acidic environments, as well as its ability to perform well at high temperatures. Its unique combination of nickel, chromium, and molybdenum ensures it resists a wide variety of corrosive media, including sulfuric acid, phosphoric acid, and seawater. These properties make it an ideal material for industries such as chemical processing, pollution control, and marine applications, where both high temperature and aggressive corrosion are common challenges. Additionally, Incoloy 825’s excellent weldability and formability further enhance its value in industrial applications requiring reliable, long-lasting materials.