Inconel 625 (UNS N06625 / 2.4856) — The Corrosion Champion of Nickel Superalloys
Best Seller — Best Corrosion Resistance
Huaxiao Metal supplies Inconel 625 sheet, plate, bar, tube, pipe, wire, and forging per ASTM B443/B444/B446 and AMS 5666/5599/5581. With 9% molybdenum and 3.6% niobium, Inconel 625 is immune to pitting and crevice corrosion in seawater, chloride environments, oxidizing acids, and reducing acids — making it the definitive choice for marine, offshore, chemical processing, and aerospace applications. Full MTC with every order.
Inconel 625 solves the problem that 316L can’t. If your equipment is failing due to pitting corrosion in seawater, chloride stress corrosion cracking, or attack from sulfuric/hydrochloric/phosphoric acid — Inconel 625 is the answer. Its 9% molybdenum gives it a PREN (Pitting Resistance Equivalent Number) of ≥48, versus ~26 for 316L. It is fully immune to chloride stress corrosion cracking. It welds without post-weld heat treatment — a huge cost advantage in fabrication. It serves from cryogenic temperatures to 980°C.
The most common forms are ASTM B443 sheet/plate (for vessel fabrication and cladding), ASTM B446 bar (for shafts and fasteners), and ASTM B444 seamless tube (for heat exchangers and process piping). Huaxiao Metal stocks all three — request a quote with your dimensions and get a response within 12 hours.
Inconel 625 Product Forms — Size Range & Standards
Huaxiao Metal supplies all common forms of Inconel 625. Standard mill sizes in stock; custom cutting to your dimensions.
| Product Form | ASTM Standard | AMS Standard | Typical Size Range | Availability |
|---|---|---|---|---|
| Sheet | ASTM B443 | AMS 5599 | 0.3–6.0 mm × 1000×2000 / 1220×2440 mm | ✅ Stock |
| Plate | ASTM B443 | AMS 5599 | 6.0–80 mm × up to 3000 mm wide | ✅ Stock |
| Round Bar | ASTM B446 | AMS 5666 | 6–300 mm diameter × 1000–6000 mm | ✅ Stock |
| Seamless Tube | ASTM B444 | AMS 5581 | OD 6–219 mm × WT 0.5–20 mm | ✅ Stock |
| Seamless Pipe | ASTM B444 | — | NPS 1/8″–8″ × SCH 10S–80S | ✅ Stock |
| Welded Tube | ASTM B704 | — | OD 12–100 mm × WT 0.5–3 mm | ⏳ Quick Order |
| Wire | — | AMS 5837 | 0.1–12 mm diameter, coil/spool | ✅ Stock |
| Forging | ASTM B564 | AMS 5666 | Custom shapes, up to 500 kg | ⏳ Made to Order |
| Flange / Fitting | ASTM B366 | — | ANSI/ASME B16.5, B16.9, B16.11 | ⏳ Quick Order |
| Strip / Coil | ASTM B443 | AMS 5599 | 0.1–3.0 mm × 5–650 mm width | ⏳ Quick Order |
✅ Stock = Available from Shanghai warehouse | ⏳ Quick Order = 2–4 week lead time | Custom sizes and non-standard lengths available on request
Inconel 625 at a Glance — Key Specifications
One glance at the data that matters for your Inconel 625 material selection.
Why Inconel 625? — The Molybdenum Advantage
The 9% molybdenum content defines Inconel 625. It is the single element that makes this alloy the corrosion champion.
Seawater Immunity
Inconel 625 is one of the few alloys completely immune to pitting and crevice corrosion in stagnant seawater. PREN ≥48 far exceeds the seawater threshold of 40. This is why offshore platforms, submarine components, and desalination plants specify 625.
Chloride SCC Resistance
Unlike austenitic stainless steels (304/316), Inconel 625 is immune to chloride stress corrosion cracking (SCC). In hot chloride environments above 60°C where 316L cracks, 625 runs indefinitely.
Acid Resistance
625 resists sulfuric acid (all concentrations to 40°C, dilute to boiling), hydrochloric acid (dilute, ambient), phosphoric acid (all concentrations), nitric acid (passive), and organic acids. Few alloys match this breadth of acid compatibility.
Weld Without PWHT
Niobium stabilization prevents intergranular corrosion in the heat-affected zone after welding. No post-weld heat treatment is needed to restore corrosion resistance — saving significant fabrication cost vs 316L and other stainless steels.
Inconel 625 Standards & Certifications
All Inconel 625 supplied by Huaxiao Metal meets applicable ASTM, AMS, ASME, and NACE standards. Full traceability to mill heat number.
| Category | Standard | Product Forms Covered |
|---|---|---|
| ASTM | B443 | Sheet, Plate, Strip — UNS N06625 |
| ASTM | B444 | Seamless Pipe & Tube — UNS N06625 |
| ASTM | B446 | Bar, Rod, Wire — UNS N06625 |
| ASTM | B704 | Welded Tube — UNS N06625 |
| ASTM | B705 | Welded Pipe — UNS N06625 |
| ASTM | B366 | Fittings — UNS N06625 |
| ASTM | B564 | Forgings — UNS N06625 |
| AMS | 5599 | Sheet, Strip, Plate — Solution Heat Treated |
| AMS | 5666 | Bar, Forging, Ring — Annealed |
| AMS | 5581 | Seamless Tubing — Solution Heat Treated |
| ASME | SB-443 / SB-444 / SB-446 | Pressure Vessel Code equivalents |
| NACE | MR0175 / ISO 15156 | Sour service to Level VII (232°C) |
| NORSOK | M-650 | Offshore Norway qualification |
| PED | 2014/68/EU | European Pressure Equipment Directive |
Inconel 625 Corrosion Resistance — By Environment
Quantitative corrosion data for the environments Inconel 625 is most commonly specified for.
| Environment | Condition | Corrosion Rate | Rating | Notes |
|---|---|---|---|---|
| Seawater (stagnant) | Ambient | < 0.001 mm/year | ⭐⭐⭐⭐⭐ Immune | No pitting, no crevice attack |
| Seawater (flowing) | Up to 40°C | < 0.005 mm/year | ⭐⭐⭐⭐⭐ Immune | Standard for offshore risers |
| H₂SO₄ 10% | Boiling | < 0.1 mm/year | ⭐⭐⭐⭐ Excellent | Acceptable for process equipment |
| H₂SO₄ 40% | 40°C | < 0.05 mm/year | ⭐⭐⭐⭐ Excellent | Common in chemical plants |
| HCl 1% | Ambient | < 0.02 mm/year | ⭐⭐⭐⭐ Excellent | 316L fails at any concentration |
| H₃PO₄ (all conc.) | Up to boiling | < 0.1 mm/year | ⭐⭐⭐⭐ Excellent | Fertilizer industry standard |
| HNO₃ 65% | Boiling | 0.05–0.2 mm/year | ⭐⭐⭐⭐ Good | Passive film protects well |
| NaOH 50% | Boiling | < 0.01 mm/year | ⭐⭐⭐⭐⭐ Immune | Excellent caustic resistance |
| Wet Cl₂ gas | Ambient | < 0.01 mm/year | ⭐⭐⭐⭐ Excellent | Critical for chlorine industry |
| Flue gas (SO₂/SO₃) | Up to 200°C | < 0.01 mm/year | ⭐⭐⭐⭐ Excellent | FGD scrubber standard |
| H₂S (sour gas) | NACE MR0175 | Pass | ⭐⭐⭐⭐⭐ Certified | Full NACE compliance to 232°C |
Inconel 625 Chemical Composition — Element Limits (%)
Per ASTM B443/B444/B446. The key is 9% Mo for pitting resistance + 3.6% Nb for stabilization and strength.
| Element | Ni | Cr | Mo | Nb+Ta | Fe | C | Mn | Si | Al | Ti | P | S |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Inconel 625 | 58.0 min | 20.0–23.0 | 8.0–10.0 | 3.15–4.15 | ≤ 5.0 | ≤ 0.10 | ≤ 0.50 | ≤ 0.50 | ≤ 0.40 | ≤ 0.40 | ≤ 0.015 | ≤ 0.015 |
Ni: 58%+ → Austenitic matrix, non-magnetic
Cr: 20-23% → Self-healing Cr₂O₃ passive layer
Mo: 8-10% → Pitting & crevice corrosion champion
Nb+Ta: 3.6% → Stabilization + precipitation strengthening
Inconel 625 Physical & Mechanical Properties
Room-temperature properties in annealed condition. Solution-annealed values differ; contact us for specific temper data.
Physical Properties
| Property | Value | Property | Value |
|---|---|---|---|
| Density | 8.44 g/cm³ (0.305 lb/in³) | Melting Range | 1290–1350°C (2350–2460°F) |
| Thermal Conductivity | 9.8 W/m·K (at 20°C) | Electrical Resistivity | 1.29 μΩ·m (at 20°C) |
| Specific Heat | 410 J/kg·K (at 20°C) | Thermal Expansion | 12.8 ×10⁻⁶ /°C (20–100°C) |
| Modulus of Elasticity | 207 GPa (30.0 ×10⁶ psi) | Shear Modulus | 78.6 GPa (11.4 ×10⁶ psi) |
| Poisson’s Ratio | 0.312 | Magnetic Permeability | ~1.0006 (non-magnetic) |
Mechanical Properties — Annealed vs Solution-Treated
| Property | Annealed (Grade 1) | Solution-Treated (Grade 2) | Condition |
|---|---|---|---|
| Tensile Strength | ≥ 827 MPa (120 ksi) | ≥ 690 MPa (100 ksi) | Room temperature |
| Yield Strength (0.2%) | ≥ 414 MPa (60 ksi) | ≥ 276 MPa (40 ksi) | Room temperature |
| Elongation | ≥ 30% | ≥ 30% | 50 mm / 2 in gauge |
| Hardness | ≤ 287 HBW | ≤ 287 HBW | Brinell |
| Reduction of Area | — | — | Report per ASTM |
Note: Grade 1 (annealed) is the standard supply condition for most applications. Grade 2 (solution-treated) is specified where weldability with maximum intergranular corrosion resistance is required. AMS 5666 covers bar in the annealed condition.
Inconel 625 Applications — Where Corrosion Resistance is Non-Negotiable
When 316L fails and Monel falls short on temperature — Inconel 625 is the answer. Eight industries where 625 is the material of choice.
Marine & Offshore
Subsea wellhead components, platform riser cladding, propeller shafts, seawater piping, mooring cables, desalination heat exchangers. NORSOK M-650 qualified.
PREN ≥48
Chemical Processing
Heat exchangers, reaction vessels, distillation columns, acid-handling piping, evaporator tubes, scrubbers handling mixed H₂SO₄/HCl/HF streams.
Acid-Resistant
Aerospace
Engine thrust reverser components, exhaust ducting, turbine seal rings, fuel and hydraulic line tubing, bellows, expansion joints. AMS 5599 qualified for sheet.
AMS Certified
Nuclear Power
Reactor core components, control rod drive mechanisms, steam generator tube support plates, waste processing equipment. Excellent resistance to high-temperature pure water.
Nuclear Grade
Flue Gas Desulfurization (FGD)
Scrubber towers, mist eliminators, outlet duct liners, stack liners, dampers. 625-clad steel for cost-effective FGD construction. ASTM A265 for clad plate.
625-Clad
Oil & Gas
Sour gas wellhead components (NACE MR0175 to 232°C), downhole hangers, subsurface safety valves, gas lift mandrels, instrument tubing.
NACE MR0175
Pharmaceutical & Food
Clean-in-place (CIP) systems, sterile processing equipment, pharmaceutical reactor vessels, heat exchangers for aggressive cleaning chemicals.
FDA-compatible
Water Treatment & Desalination
Multi-stage flash (MSF) and reverse osmosis (RO) desalination, brine heaters, evaporator tubes, high-pressure brine piping.
Desalination
Inconel 625 vs 718 vs 600 — When to Choose Which
625 isn’t always the right answer. Here’s a quick decision guide for the three most popular Inconel grades.
| Criteria | Inconel 625 | Inconel 718 | Inconel 600 |
|---|---|---|---|
| Best For | Corrosion resistance | Mechanical strength | Caustic / high-temp oxidation |
| Max Temp | 980°C | 700°C | 1090°C |
| Tensile Strength | 830 MPa | 1035 MPa 🥇 | 550 MPa |
| Seawater | ⭐⭐⭐⭐⭐ Immune | ⭐⭐⭐ Good | ⭐⭐ Fair |
| Acid Resistance | ⭐⭐⭐⭐⭐ | ⭐⭐⭐ | ⭐⭐⭐ |
| Weldability | ⭐⭐⭐⭐⭐ No PWHT | ⭐⭐ Needs PWHT | ⭐⭐⭐ Standard |
| Cost (Relative) | ★★★★ | ★★★★★ | ★★ |
| Key Applications | Marine, Chemical, FGD, Offshore | Jet Engines, Gas Turbines, Cryogenic | Nuclear, Furnace, Heat Exchangers |
Explore Related Inconel Grades
Inconel 625 FAQ — Your Questions, Answered
What is Inconel 625 made of?
Inconel 625 (UNS N06625 / 2.4856) is a nickel-chromium-molybdenum-niobium superalloy. Key composition: Ni 58% min, Cr 20-23%, Mo 8-10%, Nb+Ta 3.15-4.15%, Fe ≤5%, C ≤0.10%. The 9% molybdenum content gives Inconel 625 its legendary resistance to pitting and crevice corrosion.
What makes Inconel 625 corrosion resistant?
Three mechanisms: (1) 9% molybdenum provides outstanding pitting resistance (PREN ≥48 — far above the seawater immunity threshold of 40), (2) 20-23% chromium forms a self-healing passive Cr₂O₃ oxide layer, (3) 3.6% niobium stabilizes the microstructure against sensitization during welding. This makes 625 immune to chloride stress corrosion cracking and resistant to sulfuric, hydrochloric, and phosphoric acids.
What is the difference between Inconel 625 and Inconel 718?
Inconel 625 is optimized for corrosion resistance (9% Mo), serving marine, chemical, and offshore up to 980°C. Inconel 718 is optimized for mechanical strength (5% Nb), precipitation-hardened to 1035+ MPa, serving jet engine disks and cryogenic tanks up to 700°C. 625 welds easily without PWHT; 718 requires careful heat treatment. 625 costs less than 718.
Can Inconel 625 be used in seawater?
Yes — Inconel 625 is one of the best alloys for seawater. It is immune to pitting and crevice corrosion in stagnant and flowing seawater at all temperatures up to 980°C. Unlike stainless steels, it does not suffer chloride SCC. Widely used for offshore risers, subsea wellhead components, submarine propeller shafts, and desalination heat exchangers.
What is the price of Inconel 625 per kg?
Approximate ranges (dependent on form, size, quantity, and nickel LME): sheet/plate $45-65/kg, bar $40-58/kg, tube/pipe $55-80/kg, wire $50-70/kg. All prices include MTC. Contact Huaxiao Metal with your specification for a firm quote — typically within 12 hours.
What are the ASTM and AMS standards for Inconel 625?
ASTM: B443 (sheet/plate), B444 (seamless tube/pipe), B446 (bar), B704 (welded tube), B705 (welded pipe), B366 (fittings), B564 (forgings).
AMS: 5599 (sheet/strip/plate), 5666 (bar/forging/ring), 5581 (seamless tube).
ASME SB-443/444/446 for pressure vessels.
NACE MR0175 for sour service to 232°C.
Can Inconel 625 be welded?
Yes — Inconel 625 has excellent weldability. GTAW (TIG), GMAW (MIG), SMAW, and SAW processes all work well. Standard filler: ERNiCrMo-3 (AWS A5.14). Niobium stabilization means no post-weld heat treatment is needed to restore corrosion resistance — a major cost advantage over 316L and other stainless steels.
What is the maximum temperature for Inconel 625?
980°C (1800°F) maximum service temperature. Above this, gamma-double-prime dissolves and creep resistance declines. For applications above 1000°C, consider Inconel 600 (1090°C) or Inconel 601 (1200°C). For the best combination of corrosion resistance and moderate high-temperature strength, 625 is optimal up to 980°C.
Is Inconel 625 magnetic?
No — Inconel 625 is non-magnetic in the annealed condition. Its austenitic FCC structure gives it a relative magnetic permeability of approximately 1.0006 — effectively zero. Cold working may introduce slight magnetism, but 625 remains substantially non-magnetic. This makes it suitable for electronic, medical, and sensitive instrumentation applications.
How does Inconel 625 compare to 316L stainless steel?
Inconel 625 outperforms 316L in every corrosion metric: PREN ≥48 vs ~26, immune to chloride SCC (316L is susceptible), usable to 980°C vs ~500°C, far superior in acids.
However, 625 costs 5-8x more and is denser (8.44 vs 8.0 g/cm³). Use 316L for general service below 500°C; upgrade to 625 when 316L fails.
Ready to Order Inconel 625?
Send us your grade (Inconel 625), product form, dimensions, quantity, and any certification requirements. You’ll receive a competitive quote with lead time — typically within 12 hours.