Hastelloy C276 vs Incoloy 825: Which Alloy Should You Choose?

Pick Hastelloy C276 when hydrochloric acid, hot chlorides, wet chlorine or mixed oxidising-reducing acids are in the stream. Pick Incoloy 825 when the duty is moderate sulfuric or phosphoric acid, sour gas inside its ISO 15156-3 envelope, or any large-tonnage job where paying two to two-and-a-half times more per kilogram buys nothing.

Both alloys are solid-solution nickel grades delivered in the annealed condition, both weld with nickel-base filler, and both outlast every stainless steel inside their intended window. The real question is not which grade is better in the abstract, it is which failure mode you are willing to pay to avoid.

The gap starts with chemistry. C276 carries 15-17% molybdenum plus 3-4.5% tungsten and reaches a PREN of roughly 65-70. Incoloy 825 carries 2.5-3.5% molybdenum plus 1.5-3% copper and lands near 31-35. That single difference explains most of the spread in hydrochloric acid, seawater and FGD service, and it is also why 825 usually costs less per kilogram while C276 usually costs less per year of service in severe duty.

Key Facts: Hastelloy C276 vs Incoloy 825 at a Glance

What Is the Difference Between Hastelloy C276 and Incoloy 825?

The difference is intent. C276 is a universal severe-service alloy built around molybdenum and tungsten; Incoloy 825 is a cost-controlled acid and sour-service alloy built around copper and titanium on a partly iron base. That design choice, not quality, is what separates them.

Hastelloy C276 (UNS N10276) is nickel-balanced with 15-17% molybdenum and 3-4.5% tungsten. That chemistry is what lets it survive reducing acids such as hydrochloric, mixed streams that swing between oxidising and reducing, and chloride brines that pit almost everything below it. Its carbon is capped at 0.01% and its silicon at 0.08% deliberately: those limits keep grain-boundary precipitates out of the weld heat-affected zone, so C276 is normally placed in service as-welded. The full chemistry is set out in the C276 chemical composition guide.

Incoloy 825 (UNS N08825) holds nickel at 38-46% and lets iron carry roughly 22% of the mix, and that iron is where the cost saving comes from. It answers sulfuric and phosphoric acid with 1.5-3% copper, buys resistance to intergranular attack with a 0.6-1.2% titanium addition, and holds useful strength to about 540 °C. It is the alloy you reach for when 904L or Alloy 20 is failing but C276 is more than the process will ever need.

On the familiar selection ladder, both sit above the stainless options: 316L, then 904L or Alloy 20, then 825, then C276. JN's chemical-plant comparison puts 825 at roughly 3-4x the cost of 316L and C276 at roughly 6-8x, which is the single most useful number to have in your head before a specification meeting.

What Is the Difference in Chemical Composition?

C276 is a nickel-molybdenum-chromium-tungsten alloy; 825 is a nickel-iron-chromium alloy with molybdenum, copper and titanium. The molybdenum gap - roughly five to one - drives nearly every performance difference discussed below.

Nominal composition limits, weight percent. PREN is calculated from typical mid-range values, not from specification limits.

Read that table as three separate decisions. Molybdenum sets pitting and crevice resistance, and C276 has five times more of it. Copper sets performance in non-oxidising sulfuric and phosphoric acid, and only 825 has it - which is why 825 can post lower corrosion rates than C276 in a few clean sulfuric duties even though it loses almost everywhere else. Titanium lets a welded 825 vessel go into service without a full re-anneal, which matters on large shop-fabricated tanks.

Which Alloy Wins in Each Corrosive Medium?

C276 wins on halides and on mixed or contaminated acid; 825 wins on clean sulfuric and phosphoric acid at moderate concentration and temperature, and it wins on price. Two rows in the table below - hydrochloric acid and hot chlorides - settle most real projects before cost is even discussed.

Media-by-media verdict. Ratings describe typical process duty, not reagent-grade laboratory acid.

If your stream contains hydrochloric acid or hot chloride, the comparison is over. If it is clean sulfuric or phosphoric acid at moderate strength, 825 deserves a serious look, because it will very likely cost half as much and last just as long.

Which Is Better for Sulfuric Acid Service?

In clean, non-aerated sulfuric acid up to roughly 65-70% and up to about 80 °C, Incoloy 825 is usually the better purchase - and it can post lower corrosion rates than C276, because its 1.5-3% copper is specifically effective against non-oxidising acid. Raise the temperature, add chlorides, add oxidising contaminants, or push towards oleum, and C276 takes over.

That is not a technicality. Commercial sulfuric acid rarely stays clean: it picks up chloride from cooling water leaks, ferric and cupric ions from upstream equipment, and heat from exothermic dilution. Each of those shifts the balance towards C276, which is why plant specifications usually jump straight to C276 once temperature exceeds about 80-100 °C or chloride exceeds a few hundred ppm.

Counter-intuitive but worth remembering: in some clean sulfuric duties 825 outperforms C276, because copper attacks the weak point of non-oxidising H2SO4 and C276 has none. The moment the stream stops being clean, that advantage disappears and C276 wins. This is the one acid where the cheaper alloy can be the technically better one.

For equipment-level selection, the nickel-alloy pipe selection guide by acid type and the C276 acid-service guide cover the concentration and temperature bands in more detail; the 98% sulfuric acid case study shows where stainless stops working altogether.

Can Incoloy 825 Handle Hydrochloric Acid?

No, not beyond traces at ambient temperature. Hydrochloric acid is the single clearest dividing line between these two alloys, and it should be settled before any other argument is heard.

Hydrochloric acid attacks through the chloride ion, and resistance to it scales with molybdenum. With only 2.5-3.5% Mo and a PREN of about 31-35, 825 has no margin: published guidance limits it to very dilute acid at room temperature and rules it out for process duty. C276, with 15-17% Mo plus tungsten, is among the best commercial alloys available for HCl and is routinely specified across all concentrations well above ambient. The C276 hydrochloric acid selection guide gives the iso-corrosion detail.

The practical trap is hidden HCl. Acid cleaning, amine and catalyst regeneration, hydrolysis of chlorinated solvents and upset conditions all generate chloride in streams that look chloride-free on the datasheet. If any of those are possible, treat the specification as a C276 decision, because the upset, not the normal case, is what destroys equipment.

Which Is Better for Phosphoric Acid and Fertiliser Duty?

Both are established, but Incoloy 825 has the longer track record in wet-process phosphoric acid evaporators and heat exchangers. Move to C276 when the acid carries significant fluorides, chlorides or abrasive solids, or when the stream runs hot.

Wet-process acid is never pure H3PO4. It brings sulfate, fluoride, chloride, silica and suspended solids out of the rock, and that package is what defeats stainless steels. 825 handles it well at moderate temperature, which is why it is the conventional evaporator-tube and heat-exchanger alloy in fertiliser plants. C276's molybdenum gives it the wider margin when fluoride and chloride climb; typical published rates put C276 below about 0.3 mm/year in 10% acid where 825 sits nearer 0.5 mm/year.

Most fertiliser plants end up zoning the plant rather than picking one alloy: 825 for bulk evaporator surface and piping, C276 for agitators, pump wet-ends, and the hottest or most concentrated sections. The same zoning logic is set out for vessels and piping in the C276 chemical-plant guide.

How Do They Handle Nitric, Hydrofluoric and Mixed Oxidising Acids?

825's higher chromium - 19.5-23.5% against 14.5-16.5% - gives it the edge in straightforward oxidising nitric duty, while C276 wins whenever oxidising species are mixed with chlorides or with reducing acids.

Neither alloy is the right answer for hot concentrated nitric acid. Grades such as Hastelloy C22 or G30, or in some cases a correctly specified stainless, make more sense there - see the C22 vs C276 comparison. At moderate concentration and temperature, however, 825's chromium is a genuine advantage.

For hydrofluoric acid and nitric-hydrofluoric pickling lines, C276 is the safer choice: 825 is reported to struggle in high-concentration unbuffered HF, while the Mo-W chemistry of C276 tolerates fluoride far better. Where the pickle liquor is mostly sulfuric, 825 remains the industry workhorse for tanks, heating coils and racks.

Which Resists Chloride Pitting, Crevice Attack and Seawater Better?

C276, by roughly a factor of two in PREN and by a wide margin in every standard pitting test. This is the second decisive row in the comparison, and it is the one that catches 825 specifications out most often.

Chloride resistance indicators. CPT values are method- and heat-dependent, so always state the test method when you specify one.

PREN is a ranking tool rather than a design number, but a gap between roughly 31-35 and roughly 65-70 is too large to argue with. In standard ferric chloride testing C276 is routinely reported off-scale above 100 °C, while 825 typically lands around 50-55 °C. Because CPT moves with the test method and with the individual heat, always name the method - G48 Method C for pitting, Method D or E for crevice - when you put a corrosion test on a purchase order.

In real seawater that translates into a simple rule: 825 is acceptable for flowing seawater, pump shafts and moderate chloride process water, and is not the alloy for stagnant, creviced, chlorinated or warm seawater. C276 handles all of it. For a wider view of the options, see what alloy to use for seawater piping and the marine engineering materials overview.

Both alloys resist chloride stress-corrosion cracking far better than any austenitic stainless - 825 because of its 38-46% nickel, C276 because of its nickel base. SCC is therefore rarely the discriminator between them. Pitting and crevice corrosion are.

What Are the Temperature Limits and ASME Code Ceilings?

C276 is listed to 677 °C (1250 °F) in ASME Section VIII Division 1; Incoloy 825 is listed to 538 °C (1000 °F). Above roughly 540 °C, 825 begins to precipitate phases and loses both toughness and corrosion resistance, so high-temperature duty moves to Incoloy 800H/800HT or Inconel 625 instead.

Temperature ceilings. The Code ceiling is a mechanical-design limit; the metallurgical ceiling is where the alloy itself changes.

Two ceilings matter here and they are easy to confuse. The first is the Code ceiling, the temperature to which allowable stresses are tabulated, which governs mechanical design. The second is the metallurgical ceiling, above which the alloy changes and corrosion resistance falls. For 825 those two sit close together, which is why pressure-vessel designs in corrosive service rarely approach the listed 538 °C.

JN's own chemical-plant comparison quotes a more conservative process-side band for 825 - roughly 550 °F (288 °C) in sour and phosphoric duty - because corrosion, not creep, is usually what governs. For the C276 side in detail, see Hastelloy C276 temperature limits.

How Do Mechanical Properties and Pressure Design Compare?

C276 is roughly 15-20% stronger in the annealed condition, but the design consequences that matter most come from density, stiffness and thermal expansion rather than from strength.

Room-temperature mechanical and physical properties in the annealed condition. Strength values are specification minima.

Density matters more than it looks. A C276 spool weighs about 9% more than the same spool in 825 and also costs more per kilogram, so the installed price gap on a large piping run is wider than the per-kilogram ratio alone suggests.

Thermal expansion matters whenever either alloy is welded to carbon steel or to austenitic stainless. 825 at 14.0 µm/m·°C sits close to austenitic stainless (about 16) and far from carbon steel (about 12); C276 at 11.2 sits nearer carbon steel. Where dissimilar joints and thermal cycling are involved, that difference changes the expansion-joint and support design.

Which Is Easier to Weld and Fabricate?

Both weld well with conventional processes and neither normally needs post-weld heat treatment - but the filler rules are not interchangeable, and mixing them is one of the most common specification errors with this pair of alloys.

Welding and fabrication comparison.

Put this on the drawing: 825 to 825 uses ERNiCrMo-3 or a matching ERNiFeCr-1; C276 to C276, and C276 to any lower alloy, uses ERNiCrMo-4. Welding C276 with an 825 filler dilutes molybdenum and tungsten in the weld metal and leaves a seam that corrodes faster than the plate around it.

Procedure qualification follows ASME Section IX, and both alloys need clean, dedicated tooling: grinding wheels and wire brushes used on carbon steel will contaminate the joint and can cause cracking. Parameter-level detail for the C276 side is in the C276 welding guide, and the shop versus field welding comparison explains why CRA spools are best built under cover.

Which Machines Better?

825 is the easier of the two, but neither is easy. Both work-harden, both conduct heat poorly, and both punish a light cut or a dull tool.

Incoloy 825 machines much like an austenitic stainless with higher cutting forces: positive rake geometry, sharp carbide, rigid setup, generous coolant and no dwelling. C276 adds a stronger tendency to work-harden and to smear, so machinists typically drop cutting speed further, keep feed rates up, and flood the cut - see the C276 machining tips page.

The consequence shows up in lead time and part cost rather than in feasibility. Complex C276 components - valve trim, impellers, instrument bodies - cost noticeably more to finish, which is one more reason to reserve C276 for the zones that genuinely need it.

What Do They Cost, and Where Does Incoloy 825 Actually Save Money?

Per kilogram, C276 is typically about two to two-and-a-half times 825. On the 316L = 1 scale used across JN's chemical-plant guides, 825 sits near 3-4x and C276 near 6-8x, so the gap between these two is roughly the same size as the gap between 825 and 316L.

Cost and availability. Prices move with the nickel and molybdenum markets, so treat them as indicative bands rather than quotations.

825 saves real money on large surface area at moderate severity. Vessel shells, evaporator tube bundles, long piping runs, tank linings and structural internals in sulfuric or phosphoric service are exactly where paying double for C276 buys no extra life.

It stops saving money on any component whose failure stops the plant. On agitators, pump wet-ends, valve trim, nozzle welds and the hottest or most contaminated zones, the C276 premium is small against even one shutdown. The usual industry answer is zoning - 825 in bulk, C276 at the critical points - an approach covered in depth in the Incoloy 825 vs Hastelloy C276 sour-gas comparison.

For current numbers, see the C276 pipe price guide and Incoloy 825 pipe sizes and prices; both move with the market, so confirm before budgeting.

What Do the ASTM, ASME and NACE Standards Require?

Order each alloy to its own ASTM product specification, and check ISO 15156-3 separately if H2S is present - because the two alloys sit in different tables with different qualification envelopes.

Product specifications and governing standards.

On the purchase order, name the UNS number, the ASTM specification and its edition, the product form, the heat-treatment condition, and any supplementary requirements - grain size, corrosion test (ASTM G28 or G48), hardness limit for sour service, and EN 10204 3.1 certification. Writing Incoloy 825 or Hastelloy C276 alone is not a specification.

If H2S is in the stream, go straight to the sour-service comparison: 825 is qualified under ISO 15156-3 Table A.1 with a 35 HRC hardness cap and environmental limits on H2S partial pressure, chloride and temperature, while C276 sits in Table A.14 with a far broader window.

How to Choose Between Hastelloy C276 and Incoloy 825?

Use these five checks in order. The first one that fails usually ends the discussion, so there is no need to score anything.

1. Write the service envelope down. List every wetted species and its range: acid type and concentration, temperature (including upsets), chlorides and fluorides in ppm, pH, velocity, solids, and whether H2S is present. Most wrong alloy decisions trace back to an envelope that was never written down.

2. Run the halide gate first. If hydrochloric acid, hydrofluoric acid, wet chlorine or hot chloride brine appears at meaningful concentration, stop and specify Hastelloy C276. Incoloy 825 fails on halides long before it fails on sulfuric acid, so this check ends most comparisons.

3. Check temperature against both ceilings. Compare the design temperature with the Code ceiling (538 °C / 1000 °F for 825, 677 °C / 1250 °F for C276) and with the metallurgical ceiling. Above roughly 540 °C, 825 precipitates phases and loses toughness, so move to Incoloy 800H/800HT or Inconel 625 instead.

4. Verify the sour-service envelope if H2S is present. Incoloy 825 is qualified under ISO 15156-3 Table A.1 with a 35 HRC hardness cap and limits on H2S partial pressure, chloride and temperature; C276 sits in Table A.14 with a far broader window. Confirm hardness on the delivered material, not just on the mill certificate.

5. Price the lifecycle, then zone the severity map. Compare material plus fabrication plus downtime risk, not price per kilogram alone. Where severity varies across the plant, zone it: 825 for bulk surface area, C276 for agitators, pump wet-ends, valve trim, nozzles and the hottest or most contaminated sections.

Twelve common service conditions and the alloy that normally wins.

If none of these fits, run coupons. Immersion testing in the actual process stream, at the actual temperature and with the actual contaminants, settles in a week what a month of table-reading will not - and both alloys are stocked in common forms, so the test is cheap to arrange.

Where Is Each Alloy Typically Used?

Incoloy 825 dominates sulfuric and phosphoric acid plant and moderate sour service; Hastelloy C276 dominates hydrochloric acid, wet chlorine, FGD and the mixed-acid duties at the top of the severity scale.

Typical applications by industry and equipment.

Both are supplied in the full range of mill forms: 825 as plate, sheet, seamless and welded pipe, bar and forgings under B424, B423, B425 and B564; C276 as plate, pipe, bar, fittings and flanges under B575, B622, B574, B366 and B564. JN stocks and ships both - see Incoloy 825 products and Hastelloy C276 products, or the C276 bar and 825 bar pages for those specific forms.

What Happens If You Choose the Wrong Alloy?

Choosing wrong in either direction costs money, but choosing 825 for a chloride or HCl stream costs the equipment. That asymmetry is why the halide check comes first in the selection procedure.

Common specification mistakes and how to catch them before the material is cut.

When Should You Still Choose Incoloy 825 Over C276?

Choose 825 when four conditions hold at once: no meaningful HCl or HF, chloride levels inside its PREN range, temperature below roughly 540 °C (and usually well below the Code ceiling in corrosive service), and enough surface area that the material premium is real money.

• Sulfuric acid up to about 65-70% and about 80 °C, where copper does the work and molybdenum is not needed.

• Wet-process phosphoric acid evaporators, heat exchangers and piping with moderate halide loading.

• Sour gas gathering, separators and tubulars inside the ISO 15156-3 Table A.1 envelope - see the dedicated sour-service comparison.

• Pickling plant tanks, heating coils and racks in sulfuric-based liquor.

• Nuclear fuel reprocessing streams that mix sulfuric, nitric and caustic at moderate strength.

• Zoned equipment: 825 for the shell and bulk surface, C276 for nozzles, agitators, valve trim and pump wet-ends.

And the honest counterweight: if you are unsure, coupons cost less than a shutdown. Both alloys are available from stock in common forms, and a two-week immersion test in the real stream is the cheapest insurance available. Talk to JN ALLOY technical sales if you want the coupons cut and the test arranged.

Related Reading and Further Comparisons

• Hastelloy C276 hub guide - the pillar page for this cluster.

• Hastelloy C276 vs Inconel 625 - the next step up the comparison ladder.

• Hastelloy C276 vs Alloy 20 and Hastelloy C276 vs 904L.

• Incoloy 825 vs Hastelloy C276 for sour gas service - the H2S-specific comparison.

• Inconel 625 vs Incoloy 825 and the difference between 625 and 825.

• C276 corrosion resistance, temperature limits and welding guide.

• C276 for acid service, FGD systems and pulp and paper.

• What is Incoloy 825 and 825 plate and sheet.

• Nickel alloy pipe selection by acid type and chemical equipment materials.

• Material FAQ library and contact JN ALLOY for a quotation.

Frequently Asked Questions

What is the main difference between Hastelloy C276 and Incoloy 825?

C276 is a nickel-molybdenum-chromium-tungsten alloy with 15-17% molybdenum, built for the most aggressive reducing acids and chloride streams. Incoloy 825 is a nickel-iron-chromium alloy with 2.5-3.5% molybdenum plus copper and titanium, built for sulfuric and phosphoric acid and moderate sour service at roughly half the material cost.

Is Hastelloy C276 better than Incoloy 825?

In severe service yes: C276 wins on hydrochloric acid, hot chlorides, wet chlorine and FGD duty, and its PREN is roughly double. In clean sulfuric acid below about 65-70% and 80 degrees C, 825 can be technically equal or better and is considerably cheaper, so better depends entirely on the stream.

Is Incoloy 825 cheaper than Hastelloy C276?

Yes, typically by a factor of two to two-and-a-half. Indicative plate prices run about US$35-55/kg for 825 against about US$75-110/kg for C276. On the common 316L = 1 scale, 825 sits near 3-4x and C276 near 6-8x. Prices move with nickel and molybdenum markets.

Which alloy is better for sulfuric acid, C276 or Incoloy 825?

For clean, non-aerated acid up to about 65-70% and 80 degrees C, 825 is usually the better buy because its 1.5-3% copper handles non-oxidising acid well. Once temperature rises, chlorides appear, or the acid is contaminated with oxidising ions, C276 takes over and 825 should not be specified.

Can Incoloy 825 be used with hydrochloric acid?

Not for process duty. With only 2.5-3.5% molybdenum, 825 is limited to trace or very dilute HCl at ambient temperature. Any meaningful concentration or temperature requires a high-molybdenum alloy such as Hastelloy C276, which is routinely used for HCl across all concentrations.

Is Hastelloy C276 suitable for hydrochloric acid?

Yes, it is among the best commercial alloys for HCl. Its 15-17% molybdenum plus 3-4.5% tungsten gives resistance across all concentrations well above ambient temperature, which is why C276 is the standard answer for HCl reactors, pickling lines and chloride-bearing process streams.

Which alloy should I use for phosphoric acid production equipment?

Incoloy 825 is the traditional choice for wet-process phosphoric acid evaporators, heat exchangers and piping at moderate temperature. Move to C276 when the acid carries higher fluoride or chloride, when it runs hot, or when abrasive solids loading is high - C276 is typically below 0.3 mm/year in 10% acid where 825 sits nearer 0.5 mm/year.

Which has better pitting resistance, Hastelloy C276 or Incoloy 825?

C276, by a wide margin. Typical PREN is about 65-70 for C276 against about 31-35 for 825, and in ASTM G48 Method C testing C276 is reported above 100 degrees C (off-scale) while 825 lands around 50-55 degrees C. In practice 825 is fine in flowing seawater and fails in warm, chlorinated or creviced seawater.

Can Incoloy 825 be used in seawater?

Yes for flowing seawater, pump shafts and moderate chloride process water. It is not the right choice for stagnant, creviced, chlorinated or warm seawater, where its PREN of about 31-35 leaves too little margin. C276 handles all of those conditions.

What is the maximum service temperature of Incoloy 825 versus Hastelloy C276?

ASME Section VIII Division 1 lists allowable stresses to 538 degrees C (1000 degrees F) for 825 and 677 degrees C (1250 degrees F) for C276. Metallurgically, 825 starts to precipitate phases above about 540 degrees C and loses toughness and corrosion resistance, so most corrosive-service designs stay well below the Code ceiling.

Can Incoloy 825 replace Hastelloy C276?

Only inside its envelope: no significant HCl or HF, chlorides within its PREN range, temperature below roughly 540 degrees C, and severity moderate. In hydrochloric acid, wet chlorine, hot chloride brine or FGD absorber duty, 825 is not a substitute and will fail early.

Can Hastelloy C276 replace Incoloy 825?

Technically almost always, commercially rarely. C276 covers a broader envelope, but at about two to two-and-a-half times the material cost it is hard to justify on large surface area in sulfuric or phosphoric duty. The usual answer is zoning: 825 in bulk, C276 at critical points.

What filler metal should I use to weld Incoloy 825?

ERNiCrMo-3 (Alloy 625 filler) is the common choice for GTAW and GMAW, with matching ERNiFeCr-1 also available and ENiFeCr-1 electrodes for SMAW. Use low heat input, keep interpass temperature below about 100 degrees C, back purge root runs with argon, and weld only in the annealed condition.

Can you weld Incoloy 825 to Hastelloy C276?

Yes, and the filler should be ERNiCrMo-4. Never weld C276 with an 825 or 625 filler: it dilutes molybdenum and tungsten in the weld metal and produces a seam that corrodes faster than the parent C276. Qualify the procedure to ASME Section IX before production welding.

Does Incoloy 825 need post-weld heat treatment?

Normally no. 825 is titanium-stabilised and is used as-welded in most service. For severe corrosive duty, a stabilising anneal at 930-1010 degrees C followed by rapid cooling restores maximum corrosion resistance and removes any sensitisation in the heat-affected zone.

Is Incoloy 825 approved for sour service under NACE MR0175?

Yes. UNS N08825 is listed in NACE MR0175 / ISO 15156-3 Table A.1 in the solution-annealed condition at a maximum hardness of 35 HRC, with environmental limits on H2S partial pressure, chloride content, temperature and elemental sulfur. C276 sits in Table A.14 with a much broader envelope.

Which alloy is better for FGD and flue gas scrubbers?

Hastelloy C276. FGD liquors combine acidic condensate, chlorides, oxidising species and abrasive solids, all of which sit outside 825's comfortable range. C276 is the standard material for absorber shells, outlet ducting and wet stack liners; 825 is sometimes used in milder upstream zones.

Which alloy is easier to machine?

Incoloy 825. It machines like an austenitic stainless with somewhat higher cutting forces. C276 work-hardens and smears more readily, so speeds are lower, feeds must stay positive, and flooded coolant is essential - which adds cost to complex finished parts.

What are the equivalent grades of Incoloy 825 and Hastelloy C276?

Incoloy 825 is UNS N08825, W.Nr 2.4858, NiCr21Mo, covered by ASTM B424, B423, B425, B163, B704, B705 and B564. Hastelloy C276 is UNS N10276, W.Nr 2.4819, NS3304, covered by ASTM B575, B574, B622, B619, B626, B366 and B564.

Is Incoloy 825 magnetic?

No. Annealed 825 is austenitic and essentially non-magnetic, with a magnetic permeability around 1.005. Hastelloy C276 is also non-magnetic, at about 1.0002. Neither alloy should be expected to show magnetic response in the annealed condition.

Which alloy should I use for acid pickling equipment?

For sulfuric-based pickling liquor, Incoloy 825 is the industry workhorse for tanks, heating coils, racks and hooks. For nitric-hydrofluoric mixed pickle liquor, or where fluorides are concentrated and unbuffered, C276 is the safer choice.

What should I write on the purchase order for each alloy?

Name the UNS number, the ASTM specification and edition, the product form, the heat-treatment condition, and any supplementary requirements: grain size, corrosion testing to ASTM G28 or G48, a hardness cap for sour service, filler metal callout, and EN 10204 3.1 certification. A trade name alone is not a specification.

References and Standards

1. Haynes International, Hastelloy C-276 alloy data sheet and corrosion data (H-2002C): composition, mechanical and physical properties, acid iso-corrosion behaviour.

2. Special Metals, INCOLOY alloy 825 bulletin: composition limits, mechanical properties, physical constants, heat treatment and welding filler recommendations.

3. ASTM B424 / B423 / B425 / B564 / B163 / B366 (Incoloy 825 plate, pipe, bar, forgings, tube and fittings) and ASTM B575 / B574 / B622 / B619 / B626 / B366 / B564 (Hastelloy C276 equivalents).

4. ASME Boiler and Pressure Vessel Code, Section II Part D (allowable stresses) and Section VIII Division 1 (design rules); ASME B31.3 for process piping.

5. ASME Section IX, welding procedure and performance qualification, including filler metal grouping for nickel alloys.

6. AWS A5.14 (ERNiCrMo-3, ERNiCrMo-4, ERNiFeCr-1) and AWS A5.11 (ENiCrMo-4, ENiFeCr-1) filler metal specifications.

7. NACE MR0175 / ISO 15156-3, Table A.1 (Incoloy 825) and Table A.14 (Hastelloy C276): qualification envelopes and hardness limits for H2S service.

8. ASTM G48, test methods for pitting and crevice corrosion resistance of stainless steels and related alloys in ferric chloride solution.

9. JN ALLOY, Hastelloy C276 hub guide: the pillar page for this comparison cluster.

10. JN ALLOY, Incoloy 825 vs Hastelloy C276 for sour gas service: the dedicated sour-service comparison.

11. JN ALLOY, Hastelloy C276 for chemical plants: relative cost ladder and plant-level application map.

12. JN ALLOY, Hastelloy C276 temperature limits and C276 welding guide.

Written by Monica · Technically reviewed by JN ALLOY technical team.
Published 2026-09-24 · Last updated 2026-09-24.
Part of the JN ALLOY Hastelloy C276 hub guide.