In highly corrosive environments such as offshore oil platforms and chemical plants, selecting the right materials is crucial. A major challenge for purchasing managers and system designers lies in balancing material over-design with the risk of pitting corrosion.
Trap: Specifying the high-end Inconel 625 (UNS N06625) for all flanges and linings when Incoloy 825 would suffice. This results in up to 30% wasted purchasing budget.
Risk: Choosing the more affordable Incoloy 825 (UNS N08825) in extreme phosphoric or hydrochloric acid environments. Due to the lack of the 9% molybdenum content found in Incoloy 625, your system will suffer catastrophic stress corrosion cracking (SCC) and localized pitting corrosion.
At Gnee Alloy, we help you find the technical "optimal balance" to ensure the highest industrial durability at the lowest possible cost.
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Inconel 625 vs Incoloy 825 Alloy Plates: How to choose
The choice between Inconel 625 and Incoloy 825 sheets depends on the operating temperature, type of corrosion, and budget. Inconel 625 is suitable for extreme high-temperature environments (> 540°C) and offers excellent mechanical strength. Incoloy 825 is suitable for applications requiring cost-effective acid, alkali, and chloride resistance at moderate temperatures.
What is Incoloy 825 material?
Incoloy 825 (UNS N08825) is an austenitic nickel-iron-chromium superalloy reinforced with molybdenum, copper, and titanium. It is highly regarded for its excellent resistance to oxidizing and reducing acids, its resistance to chloride stress corrosion cracking, and its resistance to pitting corrosion.
1. Overview of Inconel 625 and Incoloy 825 Sheets
| Parameter | Inconel 625 Plate | Incoloy 825 Plate |
|---|---|---|
| UNS Number | N06625 | N08825 |
| Chinese Equivalent | GH3625 | NS142 |
| Material Type | Wrought Nickel-based Corrosion Resistant Alloy | Wrought Nickel-Iron-Chromium Alloy |
| Strengthening Mechanism | Solid-solution strengthening (Mo + Nb) | Solid-solution strengthening (austenitic) |
| Product Forms | Plate, sheet, strip | Plate, sheet, strip |
| Typical Applications | Chemical equipment, marine engineering, FGD scrubbers, aerospace | Chemical processing, oil & gas, acid service, heat exchangers |
| Maximum Service Temperature (Load-Bearing) | ~600°C | ~450 – 550°C |
| Maximum Service Temperature (Oxidation) | ~980°C | ~980°C |
2. Comparison of chemical composition of Inconel 625 and Incoloy 825 sheets (wt%)
| Element | Inconel 625 | Incoloy 825 | Key Difference |
|---|---|---|---|
| Nickel (Ni) | ≥ 58.0 (Balance) | 38.0 – 46.0 | 625 has higher Ni |
| Chromium (Cr) | 20.0 – 23.0 | 19.5 – 23.5 | Similar |
| Iron (Fe) | ≤ 5.0 | ≥ 22.0 (Balance) | 825 has much higher Fe |
| Molybdenum (Mo) | 8.0 – 10.0 | 2.5 – 3.5 | 625 has ~3x more Mo |
| Niobium (Nb) | 3.15 – 4.15 | - | 625 contains Nb |
| Copper (Cu) | ≤ 0.07 | 1.5 – 3.0 | 825 contains Cu |
| Titanium (Ti) | ≤ 0.40 | 0.6 – 1.2 | 825 contains Ti |
| Aluminum (Al) | ≤ 0.40 | ≤ 0.20 | - |
| Carbon (C) | ≤ 0.10 | ≤ 0.05 | 825 lower C |
| Manganese (Mn) | ≤ 0.50 | ≤ 1.0 | - |
| Silicon (Si) | ≤ 0.50 | ≤ 0.5 | - |
| Phosphorus (P) | ≤ 0.015 | ≤ 0.030 | - |
| Sulfur (S) | ≤ 0.015 | ≤ 0.030 | - |
3. Comparison of room temperature mechanical properties of Inconel 625 and Incoloy 825 sheets
| Property | Inconel 625 (Annealed) | Incoloy 825 (Annealed) | Advantage |
|---|---|---|---|
| Tensile Strength, Ultimate (MPa) | ≥ 830 (120 ksi) | 550 – 620 (80-90 ksi) | 625 (~35-50% higher) |
| Tensile Strength, Yield (MPa) | ≥ 415 (60 ksi) | 220 – 280 (32-40 ksi) | 625 (~50-90% higher) |
| Elongation (%) | ≥ 30 | 25 – 40 | Similar |
| Reduction of Area (%) | ≥ 40 | ≥ 40 | Similar |
| Hardness | ~22 HRC (96 HRB) | ~80-85 HRB (~15-18 HRC) | 625 harder |
| Modulus of Elasticity (GPa) | ~207 | ~196 | Similar |
| Poisson's Ratio | 0.29 – 0.30 | 0.29 – 0.30 | Similar |
| Density (g/cm³) | 8.44 | 8.14 | 825 lighter |
Click to download the Inconel 625 alloy PDF file now
4. Inconel 625 and Incoloy 825 sheet metal dimensions and specifications
| Parameter | Inconel 625 Plate | Incoloy 825 Plate |
|---|---|---|
| Thickness Range | 0.5 – 50 mm | 0.5 – 50 mm |
| Width Range | 500 – 2500 mm | 500 – 2500 mm |
| Length Range | 1000 – 8000 mm | 1000 – 8000 mm |
| Thickness Tolerance | ±5% – ±10% | ±5% – ±10% |
| Flatness | ≤ 3 mm/m | ≤ 3 mm/m |
| Surface Finish | AP, BA, CR, Polished | AP, BA, CR, Polished |
Common Plate Thicknesses:
| Thickness (mm) | Thickness (in) | 625 Application | 825 Application |
|---|---|---|---|
| 0.5 – 1.0 | 0.020 – 0.040 | Heat shields, thin liners | Heat shields, liners |
| 1.0 – 2.0 | 0.040 – 0.080 | Ducting, liners | Ducting, liners |
| 2.0 – 4.0 | 0.080 – 0.160 | Engine casings, structural panels | Chemical processing vessels |
| 4.0 – 10.0 | 0.160 – 0.400 | Heavy structural components | Heat exchanger plates |
| 10.0 – 25.0 | 0.400 – 1.000 | Heavy duty equipment | Pressure vessel shells |
Contact us to customize Inconel 625 products to fit your project dimensions
5. Comparison of corrosion resistance between Inconel 625 and Incoloy 825 plates
| Environment | Inconel 625 | Incoloy 825 | Advantage |
|---|---|---|---|
| Oxidizing Acids (HNO₃) | Excellent | Excellent | Similar |
| Reducing Acids (H₂SO₄, HCl) | Excellent | Good | 625 |
| Sulfuric Acid (concentrated) | Good | Excellent | 825 (due to Cu) |
| Phosphoric Acid | Excellent | Excellent | Similar |
| Chloride Pitting | Excellent | Good | 625 |
| Chloride Crevice Corrosion | Excellent | Moderate | 625 |
| Chloride SCC | Excellent | Good | 625 |
| Seawater | Excellent | Good | 625 |
| High-Temperature Oxidation | Excellent to 980°C | Good to 980°C | Similar |
Corrosion Resistance Rating (1-5, 5 = best)
| Environment | 625 | 825 |
|---|---|---|
| Sulfuric Acid (dilute) | 5 | 4 |
| Sulfuric Acid (concentrated) | 3 | 5 |
| Hydrochloric Acid | 5 | 3 |
| Seawater | 5 | 3 |
| Chloride SCC | 5 | 4 |
| Nitric Acid | 5 | 5 |
6. Choosing Between Inconel 625 and Incoloy 825 Plates
If your steel plates will be exposed to severe pitting corrosion, crevice corrosion (e.g., subsea applications and desalination), or extremely high-stress/high-temperature environments (e.g., jet engine exhaust, nuclear reactors, and furnace piping), choose Inconel 625.
If your primary corrosive media are reducing acids, such as sulfuric acid and phosphoric acid, choose Incoloy 825. It performs excellently in mixed acid environments and in contamination control/flue gas scrubbers.
Contact our professionals to recommend the right alloy for your project
7. Why choose to purchase Inconel 625 boards from the inventory of Tier 1 supplier Gnee Alloy?
Regardless of the grade, we provide the metallurgical certainty your project demands:
✅️VIM + VAR Melting: Ensuring ultra-pure chemistry for both grades to maximize fatigue life.
✅️MTC 3.1 Traceability: Full EN 10204 3.1 certificates documenting the PREN value included with every batch.
✅️Wholesale Pricing: Benefit from Direct Factory Price on bulk tonnage of both 625 and 825.
✅️Custom Fabrication: We offer precision laser and waterjet Cut-to-Size services to deliver blanks ready for your assembly line.
Gnee Alloy inconel 625 certificate
Gnee Alloy Product Packaging
All stainless steel products are:
✅️Packed in wooden pallets or crates
✅️Covered with moisture-proof wrapping
✅️Labeled with heat number, standard, and size
✅️Shipped worldwide via sea, air, or express
Gnee Alloy 625 Alloy Packaging
Gnee Alloy Production Equipment and Product Testing
Contact us now to get the latest export price for Inconel 625 in 2026
FAQ
Q1: Can I weld Incoloy 825 to Inconel 625?
A: Yes. They have excellent metallurgical compatibility. We recommend using ERNiCrMo-3 (Alloy 625) filler metal. This ensures the weld joint has a corrosion resistance level equal to the superior alloy (625), preventing weak spots in your assembly.
Q2: Is Incoloy 825 safe for high-temperature oxidation?
A: Up to 540°C, yes. Beyond that, Incoloy 825 begins to lose structural stability. For fire-zones or exhaust manifolds above 600°C, you must upgrade to Inconel 625 or Inconel 600.
Q3: Does Incoloy 825 meet NACE MR0175?
A: Absolutely. Alloy 825 was specifically developed for sour gas service. It is fully NACE MR0175 Compliant, offering a high ROI for downhole components where chloride levels are moderate.
Q4: Do you support small trial orders for material validation?
A: Yes. We support Innovation and R&D projects with Flexible MOQs for both 625 and 825 plates.