Why This Comparison Matters
Choosing the wrong nickel alloy for a corrosive service environment is not just an engineering oversight — it is a costly operational failure. A valve body specified in C276 instead of C2000 for a concentrated sulfuric acid loop can corrode four times faster, turning a five-year service life into 14 months of unplanned shutdowns and expensive replacements.
Hastelloy C2000 (UNS N06200), C276 (UNS N10276), and C22 (UNS N06022) are the three most widely specified alloys in the Hastelloy C-family. All three belong to the nickel-chromium-molybdenum system and offer outstanding general corrosion resistance. Yet they differ meaningfully in composition, corrosion behavior, fabrication characteristics, and cost — differences that determine whether your equipment lasts 18 months or 18 years.
This guide is written for materials engineers, process engineers, and procurement specialists who need a defensible alloy selection backed by data. It draws on published corrosion data from Haynes International, ASTM compositional standards, and the forging production experience of Jiangsu Liangyi Co., Limited, an ISO 9001:2015 certified manufacturer of open-die forgings and seamless rolled rings in all three alloys.
This comparison focuses on wrought and forged product forms. All corrosion rate data referenced is from solution-annealed material tested under laboratory conditions. Real-world performance depends on temperature, flow velocity, surface finish, and contaminants. Always perform a site-specific corrosion assessment before final specification.
Alloy Identities at a Glance
Before diving into data, here is a concise identity card for each alloy — what it is, why it was developed, and where it shines.
Hastelloy C2000
The newest of the three, developed by Haynes International as a single-alloy solution for both reducing and oxidizing acid environments. Its defining feature is a deliberate 1.3–1.9% copper addition — completely absent in C276 and C22 — which dramatically improves resistance to concentrated sulfuric and hydrochloric acids. Combined with 22–24% chromium (the highest of the three), C2000 offers an unmatched dual-environment performance envelope.
→ The all-rounder for mixed acid serviceView UNS N06200 open-die forgings and seamless rolled rings →
Hastelloy C276
The industry workhorse since the 1960s — the most widely used and stocked nickel alloy in the world. Lower chromium (14.5–16.5%) is offset by tungsten additions (3–4.5%) and high molybdenum (15–17%), giving exceptional resistance to reducing conditions, pitting, and crevice corrosion in chloride-rich environments. It is the default specification when engineers need a proven, broadly available corrosion-resistant alloy for reducing or sour service.
→ The proven standard for chloride + reducing serviceHastelloy C22
Developed as an upgrade to C276 for oxidizing environments. C22 raises chromium to 20–22.5% while reducing tungsten, giving markedly better resistance in oxidizing acids such as nitric acid. Its versatility makes it the common choice for chemical plants handling multiple process streams and environments where the oxidizing/reducing balance is uncertain or variable throughout the production cycle.
→ Best for oxidizing media & mixed process streamsChemical Composition Comparison
Three elements drive the performance differences: chromium (oxidizing resistance), molybdenum (reducing acid resistance), and copper (unique to C2000, supercharging sulfuric and hydrochloric acid resistance).
| Element | C2000 (N06200) | C276 (N10276) | C22 (N06022) | Role in Corrosion Resistance |
|---|---|---|---|---|
| Nickel (Ni) | Balance (~59%) | Balance (~57%) | Balance (~56%) | Base metal; overall corrosion resistance and ductility |
| Chromium (Cr) | 22.0 – 24.0% ✦ | 14.5 – 16.5% | 20.0 – 22.5% | Oxidizing environment & oxidizing acid resistance |
| Molybdenum (Mo) | 15.0 – 17.0% ✦ | 15.0 – 17.0% ✦ | 12.5 – 14.5% | Reducing acid & localized corrosion resistance |
| Copper (Cu) | 1.3 – 1.9% ✦ (unique) | ≤ 0.50% | ≤ 0.50% | Concentrated H₂SO₄ & HCl resistance — only in C2000 |
| Tungsten (W) | Not present | 3.0 – 4.5% | 2.5 – 3.5% | Supplements Mo in reducing resistance; aids localized corrosion |
| Iron (Fe) | 3.0 max | 4.0 – 7.0% | 2.0 – 6.0% | Controlled impurity; minimized for best corrosion performance |
| Carbon (C) | 0.010 max | 0.010 max | 0.015 max | Ultra-low carbon prevents carbide precipitation during welding |
| Silicon (Si) | 0.08 max | 0.08 max | 0.08 max | Controlled impurity |
The 1.3–1.9% copper in C2000 is the entire rationale for the alloy's existence. Neither C276 nor C22 contains meaningful copper. In Ni-Mo-Cr alloys without copper, there is a performance gap in concentrated sulfuric acid above ~65% concentration, where the corrosion mechanism shifts and molybdenum alone is insufficient. Copper fills this gap precisely — making C2000 the only standard Hastelloy C-grade that performs well across the full H₂SO₄ concentration range from dilute to 98% concentrated.
Corrosion Resistance: Head-to-Head Data
Corrosion rate data is the engineer's primary tool for alloy selection. The figures below compare published data for all three alloys in the most industrially relevant acid systems. Rates below 0.127 mm/year (5 mpy) are generally acceptable for industrial process equipment.
Performance in Sulfuric Acid (H₂SO₄)
Sulfuric acid is the world's most produced industrial chemical. Its corrosivity varies strongly with both concentration and temperature — and this is precisely where C2000's copper addition creates a visible, measurable advantage.
| H₂SO₄ Concentration | C2000 (N06200) | C276 (N10276) | C22 (N06022) | Best Alloy |
|---|---|---|---|---|
| 10%, boiling | 0.127 | 0.330 | 0.280 | C2000 |
| 20%, boiling | 0.254 | 0.480 | 0.420 | C2000 |
| 40%, boiling | 0.381 | 0.760 | 0.610 | C2000 |
| 60%, boiling | 0.508 | 0.890 | 0.730 | C2000 |
| 80%, boiling | 0.254 | 0.380 | 0.310 | C2000 |
| 96% (concentrated), boiling | 0.051 | 0.120 | 0.085 | C2000 |
Need C2000 forgings for a corrosive chemical application? See forging sizes, delivery standards, and full corrosion data on the Hastelloy C2000 forging specifications page.
Performance in Hydrochloric Acid (HCl)
Hydrochloric acid is among the most aggressively corrosive environments for metallic materials. All three alloys show good resistance in dilute HCl, but the gap widens significantly at higher concentrations and temperatures.
| HCl Concentration | C2000 (N06200) | C276 (N10276) | C22 (N06022) | Best Alloy |
|---|---|---|---|---|
| 1% HCl, 50 °C | < 0.025 | < 0.025 | < 0.025 | All equivalent |
| 5% HCl, 50 °C | 0.051 | 0.076 | 0.102 | C2000 |
| 10% HCl, 50 °C | 0.076 | 0.127 | 0.200 | C2000 |
| 20% HCl, 50 °C | 0.127 | 0.200 | 0.355 | C2000 |
| 37% HCl (conc.), 20 °C | 0.076 | 0.102 | 0.165 | C2000 |
C22 performs notably worse than both C2000 and C276 in hydrochloric acid. Its higher chromium content, while beneficial in oxidizing environments, does not help in this strongly reducing acid system. C22's lower molybdenum (12.5–14.5%) is the root cause. If HCl resistance is a key requirement, do not specify C22 — use C2000 first, or C276 as a second choice.
Pitting Resistance Equivalent Number (PREN)
PREN quantifies theoretical resistance to pitting corrosion in chloride-containing media:
PREN = %Cr + 3.3 × %Mo + 16 × %N
of the three alloys
due to Mo + W combination
resistance compensates
All three alloys have PREN values far exceeding super-austenitic stainless steels (316L ≈ 24; 6Mo ≈ 42–47), confirming suitability for severe chloride environments. C2000's higher PREN comes from its higher chromium, despite equal molybdenum to C276.
Mechanical Properties
In most corrosion-critical applications, mechanical properties are secondary — all three alloys exceed requirements for the vast majority of chemical processing and oil & gas applications. However, engineers specifying for HPHT service need to understand elevated-temperature differences.
| Property | C2000 (N06200) | C276 (N10276) | C22 (N06022) |
|---|---|---|---|
| Tensile Strength (UTS) | 752 MPa (109 ksi) | 790 MPa (115 ksi) | 759 MPa (110 ksi) |
| Yield Strength (0.2%) | 345 MPa (50 ksi) | 355 MPa (52 ksi) | 359 MPa (52 ksi) |
| Elongation at Break | 62% | 60% | 62% |
| Brinell Hardness | ≤ 220 HB | ≤ 230 HB | ≤ 220 HB |
| Density | 8.50 g/cm³ (lightest) | 8.89 g/cm³ | 8.69 g/cm³ |
| Max Service Temperature | 650 °C (1,202 °F) | 650 °C (1,202 °F) | 650 °C (1,202 °F) |
| Magnetic Permeability | 1.0002 (lowest — non-magnetic) | 1.0010 | 1.0008 |
The mechanical properties of all three alloys are very close. C276 is marginally stronger at room temperature due to higher iron content and tungsten additions — rarely engineering-significant. C2000's lower density can be a minor advantage for large rotating components. Its exceptionally low magnetic permeability makes it the preferred choice for MRI-adjacent equipment and marine electromagnetic sensor housings.
Weldability & Fabrication
All three alloys are weldable using standard nickel alloy practices. However, filler metal selection, interpass temperature limits, and contamination protocols differ in ways that affect fabrication cost and quality.
| Parameter | C2000 (N06200) | C276 (N10276) | C22 (N06022) |
|---|---|---|---|
| Preferred GTAW Filler | ERNiCrMo-17 (matching) | ERNiCrMo-4 (matching) | ERNiCrMo-10 (matching) |
| Acceptable Alternate Filler | ERNiCrMo-10 (C22 wire) | ERNiCrMo-10 (C22 wire) | ERNiCrMo-4 (C276 wire) |
| Preheat Required (≤ 50 mm) | None | None | None |
| Max Interpass Temperature | 150 °C (stricter) | 175 °C (300 °F) | 175 °C (300 °F) |
| PWHT Required (typical) | Not required (optional for critical) | Not required | Not required |
| Hot Cracking Sensitivity | Moderate — sulfur contamination risk | Low–moderate | Low–moderate |
| Filler Metal Availability | Good (fewer mills than C276) | Excellent (widest global stock) | Good |
Hastelloy C2000 is particularly sensitive to hot cracking from sulfur contamination during welding — more so than C276 or C22. All tools, fixtures, and work surfaces must be completely free from sulfur-containing compounds, oils, greases, and marking materials. This is a common cause of weld rejection during fabrication inspection and adds a process-discipline requirement that shops experienced only with C276 may overlook.
Cost & Availability
All three alloys are premium materials priced several times higher than stainless steel grades. The relative cost relationships below reflect 2025–2026 market conditions.
| Factor | C2000 (N06200) | C276 (N10276) | C22 (N06022) |
|---|---|---|---|
| Relative Material Cost | Premium (+10–20% over C276) | Benchmark (lowest) | +5–12% over C276 |
| Global Mill Availability | Good (fewer stocking mills) | Excellent (most widely stocked) | Good |
| Standard Mill Lead Time | 8–14 weeks | 4–10 weeks | 6–12 weeks |
| Forging Lead Time (Jiangsu Liangyi) | 4–8 weeks | 4–8 weeks | 4–8 weeks |
| Life Cycle Cost in H₂SO₄ Service | Lowest — longest service life | Higher — corrodes faster in H₂SO₄ | Higher — corrodes faster in H₂SO₄ |
A real-world example: 316L stainless steel components in a 98% H₂SO₄ plant were replaced every 8–12 months. Switching to C276 extended service life to approximately 24–30 months. Switching to C2000 extended service life to over 6 years — reducing total cost of ownership (including downtime, replacement parts, and labor) by more than 60% over a 10-year operating horizon. Paying 15–20% more for C2000 over C276 is routinely justified in sulfuric acid service.
Application Scenarios: Which Alloy Wins Where?
The most useful alloy selection guide translates data into real scenarios. Below are six specific application scenarios with clear, defensible recommendations.
Sulfuric Acid Plant — Pumps, Valves, Reactor Vessels
For equipment handling H₂SO₄ across any concentration from 10% to 98%, particularly at elevated temperatures, C2000 is the clear choice. Its copper content suppresses corrosion at concentrations where C276 and C22 corrode 2–4× faster. Both pump casings and valve bodies benefit from the superior fatigue and erosion-corrosion resistance of C2000 forgings versus cast alternatives.
→ Specify C2000 (UNS N06200)Wellhead Equipment & Christmas Tree Components (NACE MR0175)
For downhole and wellhead equipment in H₂S-containing (sour) service with high-chloride brine, C276 remains the most widely specified alloy under NACE MR0175 / ISO 15156. Its decades-long track record in HPHT wellhead service, broad API 6A acceptance, and excellent SSC resistance make it the lower-risk procurement choice. C2000 is also acceptable and preferred when sulfuric acid contamination is additionally present.
→ Specify C276 (UNS N10276)Mixed Oxidizing / Reducing Process Streams
When process chemistry alternates between oxidizing and reducing conditions — reactors handling mixed acids containing both nitric acid and HCl, or environments with variable ferric ion content — C22 is specifically designed for this service. Its higher chromium gives markedly better performance during oxidizing phases, while molybdenum protects during reducing phases better than chromium-rich stainless steels.
→ Specify C22 (UNS N06022)API Manufacturing Reactors and Heat Exchangers
Active pharmaceutical ingredient (API) manufacturing uses a wide range of aggressive solvents, acids, and alkaline solutions. C2000's superior corrosion resistance across both acidic and alkaline environments, non-leaching behavior (critical for product purity), and excellent cleanability make it the premium material for API reactors. The higher cost relative to C276 is easily justified by batch-loss prevention and regulatory compliance.
→ Specify C2000 (UNS N06200)Chlorine Dioxide Bleaching Equipment
Pulp and paper bleaching environments expose equipment to ClO₂, Cl₂, NaOCl, and residual sulfuric acid in high-chloride aqueous solutions. C276 has decades of proven performance in this environment and remains the standard specification for digesters, washers, and bleaching equipment. The tungsten addition in C276 is particularly beneficial in environments with fluctuating oxidizing chlorine species.
→ Specify C276 (UNS N10276)Flue Gas Desulfurization (FGD) Scrubbers
FGD systems expose equipment to a corrosive mix of H₂SO₄ aerosols, HCl, HF, and chloride-saturated scrubbing slurries at temperatures up to 90 °C. C22's superior resistance to oxidizing conditions and wet chloride environments makes it a strong candidate. C2000 is equally appropriate and may offer advantages where HCl content is the dominant corrosive species. Both significantly outperform C276 in highly oxidizing FGD conditions.
→ Specify C22 or C2000Quick-Reference Decision Matrix
Use this matrix to assess which alloy best fits your specific service conditions at a glance.
Strong fit Acceptable, not optimal Not preferred
Final Verdict: The Decision Framework
Choose Hastelloy C2000 (UNS N06200) when:
Your process involves sulfuric acid at any concentration, hydrochloric acid at elevated temperature or concentration, mixed acid environments with both oxidizing and reducing components, pharmaceutical or food-grade service requiring non-leaching materials, or any application where you need the broadest single-alloy corrosion resistance envelope. C2000's copper addition is a genuine performance differentiator that neither C276 nor C22 can replicate. For full technical data — chemical composition, mechanical properties, corrosion tables, and available forging sizes — see the Hastelloy C2000 forged parts specifications.
Choose Hastelloy C276 (UNS N10276) when:
Your primary corrosive threats are reducing conditions, high-chloride environments without strong oxidizers, H₂S-containing sour gas service under NACE MR0175, pulp and paper bleaching environments, or when maximum global supply chain availability and the lowest unit cost among the three alloys is a procurement priority. C276 is the world's most used and best-understood corrosion-resistant nickel alloy — its track record in demanding service is unmatched.
Choose Hastelloy C22 (UNS N06022) when:
Your environment alternates between oxidizing and reducing conditions, oxidizing acids such as nitric acid are a significant process stream component, for FGD systems and incineration plants where multi-acid oxidizing gas mixtures are present, or when you need better oxidizing environment performance than C276 provides without the sulfuric acid-specific advantages of C2000.
Frequently Asked Questions
Need Hastelloy C2000, C276, or C22 Forgings?
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