Incoloy 825 Plate (UNS N08825 / W.-Nr. 2.4858)

Key takeaways: Incoloy 825 plate at a glance

• Designation: UNS N08825 / W.-Nr. 2.4858, often mis-ordered as "Inconel 825"; it is a nickel-iron-chromium alloy, not a stainless steel.
• Standard: heavy-gauge plate to ASTM B424 / ASME SB-424 (Ni-Fe-Cr-Mo-Cu plate, sheet and strip); ASTM A240 does not cover N08825 because it is a nickel alloy.
• Sour service: titanium-stabilized, molybdenum- and copper-bearing chemistry that handles sour service (H₂S) to NACE MR0175 / ISO 15156, the step beyond 316L and 904L.
• Dual-acid: resists both reducing and oxidizing acids (notably sulfuric and phosphoric), a combination few single alloys offer.
• Supply: genuine mill plate held ex-stock for immediate dispatch, with an EN 10204 3.1/3.2 mill test certificate provided with every order.

What is Incoloy 825 plate?

Incoloy 825 is a titanium-stabilized nickel-iron-chromium (Ni-Fe-Cr) alloy, built for harsh chemical exposure and sour-gas service. Nickel makes up roughly 42% of it, and that's what suppresses chloride stress-corrosion cracking. Chromium handles oxidizing acids. Molybdenum and copper cover reducing acids, sulfuric in particular. Few single alloys pull off that combination. Titanium stabilization ties up carbon so chromium stays in solution, and that's why the alloy resists sensitization after welding.

In plate form, the grade covers heavier structural and pressure-boundary sections: vessel shells and heads, tubesheets, reactor and column internals, and acid-plant equipment. These are jobs where section thickness goes beyond what Incoloy 825 sheet can handle. Need welded-tube or re-roll feedstock instead? Check Incoloy 825 coil. For the full range of forms, the Incoloy 825 grade hub is the place to start.

"Inconel 825" vs Incoloy 825: clearing up the name

Buyers routinely call this grade "Inconel 825," but no such alloy exists: it's Incoloy / Alloy 825 (UNS N08825), a Ni-Fe-Cr alloy. "Inconel" names a separate family of nickel-chromium alloys (600, 625, 718). The distinction matters commercially. Get the designation right on the purchase order and the mill test certificate, and you avoid receiving-inspection disputes when the heat shows up stamped N08825. We quote and certify against N08825 so the paperwork matches the material. Weighing the two families? See Incoloy 825 vs Inconel 625 and the grade overview, what is Incoloy 825.

Chemical composition (ASTM B424, UNS N08825)

The role of titanium, molybdenum and copper

Titanium does the stabilizing work: it locks up carbon as titanium carbide, so chromium never gets pulled out as chromium carbide. That's the mechanism behind the alloy's resistance to intergranular corrosion / sensitization in the weld heat-affected zone, the same trick that protects stabilized stainless grades 321 and 347. Molybdenum adds further resistance to pitting and to reducing acids. Copper, meanwhile, carries Incoloy 825 through sulfuric and phosphoric acid service that would eat through plain austenitic stainless. Put the three together, and 825 stands up to both reducing and oxidizing acids.

Mechanical properties (plate, annealed: ASTM B424)

For sour-service orders, confirm the hardness cap required by NACE MR0175 / ISO 15156 on the purchase order, so the heat gets supplied and documented in the qualified condition.

Physical properties

The density of 8.14 g/cm³ drives the plate weight calculation below.

Corrosion resistance and performance: why Incoloy 825 plate exists

Incoloy 825 plate is specified when the environment combines hazards that defeat a single lower alloy. Its value is breadth: one chemistry that holds in sour gas and across mixed acids, between where 904L runs out and where a solid-nickel alloy such as Inconel 625 becomes over-specified.

Sour service and NACE MR0175

The alloy's high nickel content resists sulfide stress cracking, which is why it's routinely supplied for sour service (NACE MR0175) in H₂S-bearing oil-and-gas duty. Cite NACE MR0175 on the order itself. That way the plate arrives in the qualified, hardness-controlled condition, with documentation to back it up.

Acid resistance: sulfuric and phosphoric, reducing and oxidizing

Incoloy 825 owes its resistance to both reducing and oxidizing acids to its copper-and-molybdenum chemistry. That combination is what sets it apart. It's used in sulfuric-acid resistance service, and in phosphoric-acid and fertilizer-regeneration duty, where chromium alone handles oxidizing conditions but falls short against reducing ones, and molybdenum alone works the other way around. Neither does the job solo. This dual resistance is the main reason engineers pick 825 over 316L or 904L for mixed-acid and sour-gas work.

PREN and pitting / crevice resistance

With a PREN of roughly 31–40, Incoloy 825 resists chloride pitting and crevice corrosion at a level comparable to 904L and duplex 2205. The ladder below places it in context, though for this grade the sour-service and mixed-acid story, not raw PREN, is the reason to specify it.

Chloride stress-corrosion cracking and sensitization

Incoloy 825 beats austenitic stainless in one key respect: nickel gives it resistance to chloride stress-corrosion cracking, a weakness that caps what 316L and 304 can handle in hot chloride service. The alloy is also titanium-stabilized, which guards against sensitization / intergranular corrosion in the weld heat-affected zone. Field welds hold up without needing a post-weld solution anneal.

Equivalent grades and designations

The trade name "Incoloy 825" belongs to Special Metals, and "Inconel 825" is a common misnomer for the same N08825 alloy. The full cross-reference is on the UNS / Werkstoff cross-reference.

How Incoloy 825 plate compares: when to choose it

Choose Incoloy 825 when sour service meets mixed acids and a super-austenitic stainless can't keep up, but a full Ni-base alloy would be overkill and more expensive than the job calls for.

Against 316L plate, Incoloy 825 is a decisive step up in both chloride SCC and acid breadth, the 904L vs 316L ladder illustrates one rung below. Inconel 625 carries far more molybdenum and a much higher PREN, so it outperforms 825 in the most severe pitting and high-temperature service, but at a cost premium that 825 often makes unnecessary when H₂S and mixed acids, not extreme chlorides, are the problem; see the full Incoloy 825 vs Inconel 625 comparison. It also sits above its sister grade, Incoloy 800, in wet corrosion. Use the grade selector to confirm the right rung for your service.

Forms, sizes and plate thickness ranges

Incoloy 825 is available as plate and sheet; coil and strip come in a limited form. The table lists typical plate dimensions, but confirm exact thickness, width and length when you enquire, since 825 is supplied against your cutting list.

Other Incoloy 825 forms

For lighter gauges, order Incoloy 825 sheet. For welded-tube and re-roll feedstock, see Incoloy 825 coil. Not sure which flat product fits your job? Read the difference between sheet, plate and coil, and take a look at how to choose plate thickness.

Plate weight and how to calculate

Plate weight tracks directly with density, 8.14 g/cm³. For a full plate:

Kg/plate = thickness (mm) × width (m) × length (m) × 8.14

Use the plate weight calculator to get exact figures for any size. Or check out how to calculate steel plate weight if you'd rather work it out yourself.

Finishes and surface condition

Incoloy 825 plate normally ships hot-rolled, solution- or stabilize-annealed and pickled to a No. 1 finish. That's the standard descaled surface for heavy-gauge nickel-alloy plate. Ground or machined surfaces are available too, where flatness or finish tolerances call for it. Spell out the surface condition on your inquiry so it matches your welding, forming or inspection needs downstream. For more, see stainless and nickel-alloy finishes.

Standards and specifications complied

Incoloy 825 plate conforms to ASTM B424 / ASME SB-424 (Ni-Fe-Cr-Mo-Cu plate, sheet and strip) and, for sour duty, to NACE MR0175 / ISO 15156.

ASTM B424 / ASME SB-424 for N08825: and why A240 does not apply

ASTM A240 covers chromium and chromium-nickel stainless plate, sheet and strip. Incoloy 825 is a nickel alloy, not a stainless steel, so N08825 plate is specified to the B-series (B424 / SB-424), not A240, a common spec error worth catching before the order is placed.

Testing, inspection and certification

Every order ships with an EN 10204 3.1/3.2 mill test certificate reporting heat chemistry and mechanical results, traced to the producing heat. On request we add intergranular-corrosion testing per ASTM A262, PMI confirming Ni/Mo/Cu, and ultrasonic (UT) examination plus NACE MR0175 hardness documentation for sour service. See testing, MTC, NDT and PMI, our quality assurance process and the mill test certificate overview.

In our experience, buyers most often trip up on two details on 825 plate orders. The first is the designation: they write "Inconel 825" when the heat will actually be stamped N08825. The second shows up on sour service work, where an explicit NACE MR0175 / ISO 15156 call-out often gets left off the order. Cite both on the purchase order. That way the heat gets supplied and certified in the qualified condition, and the paperwork actually matches the material once it hits receiving inspection.

Applications of Incoloy 825 plate by industry

• Oil & gas (sour) service, vessel shells, internals, and heavy components in H₂S-bearing streams, supplied to NACE MR0175.
• Chemical and acid processing, handling of sulfuric and phosphoric acid, under mixed reducing/oxidizing duty.
• Petrochemical, heat-exchanger tubesheets and process plate in corrosive service.
• Fertilizer and acid-regeneration service, phosphoric-acid plants and pickling-acid recovery.

Fabrication and welding of Incoloy 825 plate

Incoloy 825 plate gets welded with the matching over-alloyed filler ERNiFeCr-1 (FM 65), which keeps the weld metal corrosion-resistant across the joint. When a stabilize anneal is called for, it runs near 940 °C; a solution anneal sits near 940–1010 °C. That's a different treatment from what's used for austenitic stainless, see solution and stabilize annealing. The alloy work-hardens. Plan machining, rolling and forming with that in mind. For full procedure guidance, check how to weld Incoloy 825 and welding stainless and nickel alloys.

Price and availability

Incoloy 825 plate sits ex-stock, ready for immediate dispatch, and we quote it to specification on request. We don't publish price bands, since thickness, width, length, surface condition and test scope all move the number. Send us your thickness, width, length, standard (ASTM B424, plus NACE MR0175 if the service is sour), surface condition and quantity, and you'll get a firm offer back. Nandini Steel has been an ISO 9001:2015-certified stockist and supplier since 2003. Over more than 20 years we've delivered 307+ projects to 260+ clients across 36+ export countries. We supply genuine mill plate, sourced from mills including Aperam, Outokumpu, Jindal, POSCO, Nippon Steel and JFE, with full heat traceability and an EN 10204 3.1/3.2 certificate on every order. Our third-party-certified range also covers 904L, Alloy 28, Incoloy 800 and Hastelloy, the same Ni-Fe-Cr and nickel-base territory Incoloy 825 belongs to.

Frequently asked questions

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