Alloy 825™ Corrosion Resistant Alloy, UNS N08825,1

### **Product Datasheet: Alloy 825™ (UNS N08825)** **A Nickel-Iron-Chromium Alloy for Superior Corrosion Resistance in Aggressive Environments** --- #### **1. Overview** **Alloy 825™** is a versatile, corrosion-resistant **nickel-iron-chromium alloy** with additions of molybdenum and copper. It is specifically designed to withstand a wide variety of aggressive corrosive environments. Its key characteristics include excellent resistance to **reducing acids** (e.g., sulfuric and phosphoric), **oxidizing acids** (e.g., nitric), and **localized corrosion** such as pitting and crevice attack. Furthermore, it possesses high resistance to **stress corrosion cracking (SCC)**. The alloy is stabilized with titanium, which prevents sensitization and subsequent intergranular corrosion after exposure to high temperatures, making it suitable for use in the as-welded condition. It is a workhorse material in the chemical process, oil and gas, and pollution control industries. #### **2. Chemical Composition (Typical Weight %)** The composition is meticulously balanced to handle both oxidizing and reducing conditions. | Element | Content (%) | Role in the Alloy | | :--- | :--- | :--- | | **Nickel (Ni)** | Balance (~38-46) | Provides inherent resistance to caustic solutions and reducing environments. | | **Chromium (Cr)** | ~19.5 - 23.5 | Confers resistance to oxidizing environments, sulfurous acids, and nitric acid. | | **Iron (Fe)** | ~22.0 min | The base element, providing a cost-effective matrix with good structural properties. | | **Molybdenum (Mo)** | ~2.5 - 3.5 | Enhances resistance to pitting, crevice corrosion, and reducing acids. | | **Copper (Cu)** | ~1.5 - 3.0 | Provides resistance to reducing acids, particularly sulfuric acid. | | **Titanium (Ti)** | ~0.6 - 1.2 | Stabilizes the alloy against sensitization by forming titanium carbides, preventing chromium carbide precipitation at grain boundaries. | | **Carbon (C)** | ≤ 0.05 | Kept low to minimize carbide formation; titanium ties it up harmlessly. | | **Manganese (Mn)** | ≤ 1.00 | Aids in manufacturability. | | **Silicon (Si)** | ≤ 0.50 | Residual element. | #### **3. Physical Properties (Typical)** | Property | Value / Condition | | :--- | :--- | | **Density** | 8.14 g/cm³ (0.294 lb/in³) | | **Melting Range** | ~1370 - 1400 °C (~2500 - 2550 °F) | | **Thermal Expansion Coefficient** | ~14.0 μm/m·°C (20 - 100°C) | | **Thermal Conductivity** | ~10.8 W/m·K (at 100°C) | | **Modulus of Elasticity** | ~196 GPa (28.4 x 10⁶ psi) at 20°C | #### **4. Mechanical Properties (Typical for Annealed Condition)** **At Room Temperature:** * **Tensile Strength:** ≥ 620 MPa (90 ksi) * **Yield Strength (0.2% Offset):** ≥ 240 MPa (35 ksi) * **Elongation:** ≥ 30% #### **5. Corrosion Resistance** Alloy 825 is effective in a broad range of corrosive media: * **Acids:** Excellent resistance to sulfuric acid, phosphoric acid, and nitric acid. Good resistance to hydrochloric acid. * **Localized Attack:** High resistance to pitting and crevice corrosion in chloride-containing solutions. * **Stress Corrosion Cracking (SCC):** Highly resistant to chloride-induced SCC. * **Other Media:** Resists corrosion in acidic and alkaline salt solutions, seawater, and contaminated oxidizing acids (e.g., nitric acid with contaminants). #### **6. Product Applications** Alloy 825 is widely used in industries where equipment longevity in harsh environments is critical: * **Chemical Processing:** Pickling tanks, heating coils, reaction vessels, and transfer piping for acids. * **Oil and Gas:** Downhole tubing, casing, and components in sour service (H₂S-containing) wells; piping and scrubbers in acid gas environments. * **Pollution Control:** Scrubbers, ducting, and fan components in Flue Gas Desulfurization (FGD) systems. * **Pharmaceutical & Industrial:** Acid production equipment, nuclear fuel reprocessing. * **Marine Engineering:** Seawater cooling systems, propeller shafts, fasteners. #### **7. International and Industry Standards** Alloy 825 is covered by a comprehensive set of international standards for various product forms. * **UNS:** **N08825** * **DIN / Werkstoff Nr.:** **2.4858** * **ASTM Standards (U.S.):** * **ASTM B-424:** Sheet, Strip, and Plate * **ASTM B-423:** Seamless Pipe and Tube * **ASTM B-425:** Bar and Wire * **ASTM B-163:** Seamless Condenser and Heat-Exchanger Tubes * **ASME Standards (U.S.):** * **ASME SB-424:** Plate, Sheet, and Strip (for pressure vessel construction) * **ASME SB-423, SB-425, SB-163** (Equivalent to the ASTM standards for ASME code use). * **ISO:** ISO 15156-3 (NACE MR0175) for use in sour service environments in oil and gas production. --- **Disclaimer:** The information provided herein is for reference purposes only. Properties can vary based on product form, size, and manufacturing process. Corrosion resistance is dependent on specific environmental conditions (temperature, concentration, presence of oxidizers, etc.). For design and procurement, the official, latest issue of the relevant material specification and the manufacturer's technical data must be consulted. Alloy 825 is a trademark of Huntington Alloys, a subsidiary of Special Metals Corporation.

Packing of Standard Packing: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 3372 gallon liquid totes Special package is available on request.