Hastelloy C-276 vs Inconel 625 - Corrosion, Cost & Selection
Date: 2026年9月18日 Categories: News Views: 277
By Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier | ISO 9001:2015 | Est. 2012
Contact: sales@hangboalloy.com | hangbo@nickel-alloy.com | WhatsApp (Lisa): +86 13611656360
Quick Answer: What Is the Difference Between Hastelloy C-276 and Inconel 625?
Hastelloy C-276 (UNS N10276) contains 15-17% molybdenum plus 3-4.5% tungsten and is the choice for severely reducing, chloride-rich media such as wet chlorine, hydrochloric acid and contaminated sulphuric acid. Inconel 625 (UNS N06625) carries 8-10% molybdenum with niobium and is stronger, more weldable and 30-50% cheaper, but its corrosion ceiling in reducing acids is lower. Choose C-276 for chemical plant wetted parts; choose 625 for seawater, high-temperature oxidation service and structural components.
Key Takeaways
- C-276 is the reducing-acid champion. Tungsten plus 15-17% Mo gives it resilience in HCl, wet chlorine and mixed acids where 625 corrodes.
- 625 wins on strength, weldability and price. It is normally 30-50% cheaper per kilogram and does not need the tighter heat-input control C-276 demands.
- PMI must confirm tungsten. A "C-276" delivery without W is almost certainly 625 or C-22 — see the verification section below.
- Neither alloy is a high-temperature strength alloy. C-276 is not designed for sustained service above roughly 400°C; 625 tolerates oxidation service to about 980°C but with only moderate strength.
- Total cost, not unit price, decides. C-276's corrosion allowance is often thinner, which narrows the real gap on large equipment.
What Are Hastelloy C-276 and Inconel 625?
Hastelloy C-276 is a nickel-molybdenum-chromium alloy with a deliberate tungsten addition, developed for the chemical processing industry. Its chromium content (14.5-16.5%) provides oxidizing resistance while the molybdenum and tungsten dominate in reducing environments. It is normally supplied in the solution-annealed condition.
Inconel 625 is a nickel-chromium-molybdenum-niobium alloy. The niobium (plus a small tantalum fraction) is what separates it from the Hastelloy family: it provides solid-solution strengthening and, in welded structures, resistance to heat-affected-zone cracking. 625 is used both as a structural material and as a welding consumable for cladding and dissimilar joints.
Both are austenitic, non-magnetic and supplied as bar, plate, sheet, seamless tube, welded pipe and forgings. See our Hastelloy C-276 plate & bar and Inconel alloy supplier product pages for the stocked size range.
Composition Comparison (wt.%)
| Element | Hastelloy C-276 (N10276) | Inconel 625 (N06625) | Per standard |
|---|---|---|---|
| Nickel | Balance (~57) | 58.0 min | ASTM B575 / ASTM B446 |
| Chromium | 14.5-16.5 | 20.0-23.0 | ASTM B575 / ASTM B446 |
| Molybdenum | 15.0-17.0 | 8.0-10.0 | ASTM B575 / ASTM B446 |
| Tungsten | 3.0-4.5 | — | ASTM B575 |
| Iron | 4.0-7.0 | 5.0 max | ASTM B575 / ASTM B446 |
| Niobium + Tantalum | — | 3.15-4.15 | ASTM B446 |
| Cobalt | 2.5 max | 1.0 max | ASTM B575 / ASTM B446 |
| Carbon | 0.01 max | 0.10 max | ASTM B575 / ASTM B446 |
| Silicon | 0.08 max | 0.50 max | ASTM B575 / ASTM B446 |
| Manganese | 1.0 max | 0.50 max | ASTM B575 / ASTM B446 |
Table note: Values are standard composition limits published in the specifications listed. The single most useful discriminator between the two in the warehouse is tungsten: C-276 legally contains 3.0-4.5% W, 625 contains none. Molybdenum level (15%+ versus 9%) is the second check.
Mechanical Properties Comparison
| Property | Hastelloy C-276, solution annealed | Inconel 625, annealed | Per standard |
|---|---|---|---|
| UTS at 20°C | 690 MPa min (100 ksi) | 827 MPa min (120 ksi) | ASTM B575 / ASTM B446 |
| 0.2% yield at 20°C | 283 MPa min (41 ksi) | 414 MPa min (60 ksi) | ASTM B575 / ASTM B446 |
| Elongation at 20°C | 40% min | 30% min | ASTM B575 / ASTM B446 |
| Typical hardness | 90-95 HRB (typical) | 95-100 HRB (typical) | ASTM E18 |
| UTS at 400°C | ~560 MPa (typical) | ~700 MPa (typical) | ASTM E21 (typical, not a standard minimum) |
| Design temperature ceiling | ~400°C for load-bearing use (in-house guidance) | ~650°C load-bearing / ~980°C oxidation (in-house guidance) | — |
Table note: Tensile values are standard minima from the listed ASTM specifications; elevated-temperature figures are typical values for orientation only — they are not standard minima. Verify against the actual mill certificate and, for critical design, against ASTM E21 elevated-temperature tensile data.
Which Alloy Resists Which Chemicals?
| Environment | Hastelloy C-276 | Inconel 625 | Practical note |
|---|---|---|---|
| Seawater (3.5% NaCl), ambient to 40°C | Excellent | Excellent | Both are used; 625 is the offshore standard |
| 5% HCl, 50°C | Good | Poor to fair | 625 develops rapid general corrosion; C-276 is the default |
| 10% H2SO4, 60°C (aerated) | Excellent | Fair | Deaeration changes the ranking |
| 50% H2SO4, 60°C | Good | Poor | Reducing acid regime — C-276 required |
| Wet chlorine gas, humid | Excellent | Unsuitable | C-276 was developed for this duty |
| Chloride pitting (ASTM G48 practice) | Excellent (PREN ~69) | Excellent (PREN ~51) | C-276 has the wider margin |
| Nitric acid, oxidizing | Fair | Good | Oxidizing regime favours chromium-rich 625 |
| Caustic (25% NaOH, 120°C) | Good | Good | Watch stress-corrosion cracking in both |
Table note: Service ratings are qualitative engineering guidance based on published corrosion data and our own field experience; they are not ASTM G48/G28 test results for a specific heat. Request a corrosion test report for critical services.
High-Temperature Behaviour: Where Does Each Alloy Stop?
C-276 was never intended as a high-temperature strength alloy. Above roughly 400°C the alloy is subject to a slow precipitation reaction that reduces both ductility and corrosion resistance, so long-term load-bearing service at elevated temperature is normally avoided. Where a hot, corrosive environment is unavoidable, engineers either accept a reduced design life or move to a different alloy family.
625 goes the other way. It resists oxidation and scaling to about 980°C and is widely used for hot flue-gas, exhaust and afterburner components. Its limitation above 650°C is not corrosion but strength: 625 is a solid-solution alloy and will creep where a precipitation-hardened grade such as 718 or Nimonic 90 would not. For high-temperature structural duty see our Nimonic 80A bar page and the alloy technical knowledge center.
Which Alloy for Which Application?
| Application | Best choice | Why |
|---|---|---|
| Chlorinated organic / phosgene containment | C-276 | Wet chlorine and halide-heavy process streams |
| Titanium dioxide chlorination trains | C-276 | Reducing chloride at moderate temperature |
| FGD scrubber internals and dampers | C-276 plate, 625 for hot gas path | C-276 for wet-acid zones, 625 for higher-temperature oxidation |
| Seawater piping and offshore fasteners | 625 | Strength plus corrosion resistance; no tungsten cost |
| Reactor vessels and columns (mixed acids) | C-276 | Broadest envelope in reducing-to-mixed chemistry |
| High-temperature ducting to 900°C | 625 | Oxidation resistance where C-276 is not applicable |
| Overlay / weld cladding consumable | 625 | Excellent weldability and HAZ cracking resistance |
| Large fabricated tanks with moderate chemistry | 625 | Capital cost advantage when C-276 is not required |
Fabrication and Welding Notes
Both alloys are weldable by GTAW, GMAW and SMAW processes, but they behave differently on the shop floor.
C-276 requires clean, low-heat-input practice. Contamination from carbon steel tooling, sulfur-bearing marking crayons or chlorinated solvents can cause preferential weld corrosion, and the finished weld should be pickled or brushed rather than ground with iron-bearing abrasives. Interpass temperature is controlled, and filler metal of matching composition is used.
625 is more forgiving. It tolerates higher heat input, resists strain-age cracking in the heat-affected zone and is frequently chosen precisely because the fabricator has to weld a lot of it. A common and legitimate design is a 625-clad or 625-overlay component on a carbon steel or 316L shell, which gives C-276-like corrosion resistance to process contact surfaces at a fraction of solid C-276 cost.
One practical pitfall we see: fabricators transfer C-276 offcuts into a general-purpose rack and later weld them to a 625 or 316L component. Without PMI at the point of issue the two look identical, and the mismatch is only detected at final inspection.
Price Reference (2026, EXW Shanghai)
| Form | Hastelloy C-276 | Inconel 625 | Comment |
|---|---|---|---|
| Round bar, annealed | \$70-110/kg | \$48-75/kg | C-276 typically 40-50% higher |
| Plate / sheet | \$72-115/kg | \$50-78/kg | Thickness and width add spread |
| Seamless tube | \$85-140/kg | \$60-95/kg | Cold-work and testing dominate cost |
| Forging / ring | Quote by drawing | Quote by drawing | Cost driven by yield and NDT |
Table note: Reference range only — floats with LME nickel price. 2026, EXW Shanghai, USD/kg. Quotations must be confirmed against current nickel, molybdenum and tungsten raw-material levels, and against the specific size, tolerance and certification package required.
Standard Index
| Standard | Title / scope | Covers | Form |
|---|---|---|---|
| ASTM B575 | Low-carbon Ni-Cr-Mo alloy plate, sheet, strip | Composition + mechanical | plate, sheet, strip |
| ASTM B574 | Low-carbon Ni-Mo-Cr alloy bar | Composition + mechanical | bar, forging stock |
| ASTM B622 | Ni-Cr-Mo alloy seamless pipe and tube | Composition + mechanical | seamless tube |
| ASTM B446 | Ni-Cr-Mo-Nb alloy bar, forging | Composition + mechanical | bar, forging |
| ASTM B444 | Ni-Cr-Mo-Nb alloy pipe and tube | Composition + mechanical | pipe, tube |
| ASTM E1476 | Standard guide for metals identification (PMI) | Test method | — |
| ASTM G48 | Pitting and crevice corrosion resistance | Test method | — |
| ASTM E8/E8M | Tension testing of metallic materials | Test method | — |
How We Verify C-276 Before Shipment
Every C-276 heat we ship is verified on three levels before release, and this is the check that most often saves buyers money:
- Incoming heat verification by OES. The mill's wet-chemistry or OES report is compared against our own spectrometric reading on the finished bar or plate, specifically checking tungsten (3.0-4.5%), molybdenum (15-17%) and chromium (14.5-16.5%).
- Tungsten discrimination on the finished product. Handheld XRF is fast but unreliable for light elements; on tungsten-bearing nickel alloys we confirm with OES or spark analysis so that a C-22 or 625 substitution cannot pass.
- Certificate-to-heat-number reconciliation. EN 10204 3.1 certificates are reconciled line by line with the physically marked heat number on the product, and the reconciliation is photographed into the batch record.
A typical case: an incoming lot labelled "C-276" returned Cr 21%, Mo 13% and W 3% — consistent with C-22, not N10276. It was rejected before it reached the customer's fabrication line. Ask your supplier whether they perform that check, and ask to see the batch record. Full verification methodology is described in our related technical guides, and our quality and inspection workflow explains how third-party SGS/BV/TUV witness testing is arranged on request.
FAQ
Q1: Which alloy is more corrosion resistant, C-276 or 625?
It depends entirely on the medium. In reducing acids such as hydrochloric and deaerated sulphuric acid, and in wet chlorine, C-276 is clearly superior because of its 15-17% molybdenum and 3-4.5% tungsten. In oxidizing environments such as nitric acid and hot aerated solutions, 625's higher chromium (20-23%) gives it the advantage. Neither alloy is "better" in the abstract — the process chemistry decides.
Q2: Is C-276 always more expensive than Inconel 625?
Usually, yes. C-276 typically carries 15-17% molybdenum plus tungsten, both expensive alloying additions, so bar and plate generally run 40-50% above comparable 625. The gap narrows on fabricated equipment because C-276 often allows a thinner corrosion allowance, and widens on small-diameter tube where processing cost dominates.
Q3: Can I substitute Inconel 625 for Hastelloy C-276?
Only after reviewing the specific medium, temperature and concentration. In seawater, hot gas ducting and general structural duty 625 is often a legitimate and cheaper substitute. In wet chlorine, hydrochloric acid or reducing mixed acids it is not — 625 will corrode at rates that make the saving meaningless within months.
Q4: How can I tell C-276 from 625 in a warehouse?
Instrumentally. Tungsten is the discriminator: C-276 contains 3.0-4.5% W and 625 contains none, so an accurate reading for tungsten settles it. Handheld XRF units vary in their ability to quantify tungsten, so ask for OES or spark confirmation, and confirm the heat number against the EN 10204 3.1 certificate.
Q5: Is C-276 suitable for high-temperature service?
Not for sustained load-bearing service. C-276 is a solution-annealed corrosion alloy, not a heat-resistant structural alloy, and it is normally limited to roughly 400°C in long-term service because secondary phases reduce ductility and corrosion resistance. For hot oxidizing service, 625 is the appropriate choice up to about 980°C, with a strength ceiling around 650°C.
Q6: Which alloy welds more easily?
Inconel 625. It tolerates higher heat input and has good resistance to heat-affected-zone cracking, which is why it is used as a welding consumable and as cladding on cheaper substrates. C-276 must be welded clean, with controlled heat input and matching filler, and requires proper cleaning afterwards.
Q7: What is the UNS number for each alloy?
Hastelloy C-276 is UNS N10276. Inconel 625 is UNS N06625. Both appear on EN 10204 3.1 and 3.2 certificates, and the UNS number — not the trade name — is what should appear on your purchase order.
Q8: Can I use 625 as a cladding on carbon steel instead of solid C-276?
Yes, and it is common practice for large vessels and towers. A 625 overlay or clad plate gives corrosion resistance at the process contact surface at far lower cost than solid C-276. The engineering decision is whether the 625 surface chemistry is sufficient for the medium; where it is, the clad solution is usually the better project economics.
Q9: Does C-276 need heat treatment after welding?
Generally no post-weld heat treatment is required for C-276, and it is usually avoided. The alloy is supplied in the solution-annealed condition, and the low carbon content (0.01% max) limits sensitization. What is required is cleanliness, correct filler metal and mechanical/chemical cleaning of the weld area.
Q10: What forms do you supply these alloys in?
Both grades are stocked and produced as round bar (6-500 mm), plate and sheet (0.1-100 mm), seamless and welded tube (OD 6-610 mm), forgings and wire. Certification options include EN 10204 3.1, third-party witness inspection by SGS, BV or TUV, and UT/PMI testing on request.
Contact & Complete Product Range
Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier
Email: sales@hangboalloy.com | WhatsApp (Lisa): +86 13611656360 | www.nickel-alloy.com
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