In industries where corrosion resistance is critical, selecting the right alloy can mean the difference between long-term durability and costly failure. Alloy 20 and Hastelloy are two leading contenders, often used in chemical processing, marine environments, and pharmaceutical applications. But which one is better?
This article explores the key differences between Alloy 20 and Hastelloy, comparing their composition, mechanical properties, corrosion resistance, applications, and costs to help you determine the best material for your specific needs.
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What Is Alloy 20?
Alloy 20 (also known as Carpenter 20 or UNS N08020) is a nickel-iron-chromium austenitic alloy developed for maximum resistance to acid attacks, particularly sulfuric acid. It also contains copper and molybdenum to enhance its resistance to pitting, crevice corrosion, and chloride stress corrosion cracking.
Main Alloy 20 features:
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Excellent resistance to sulfuric acid
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Good weldability and formability
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Useful in a wide range of chemical environments
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Lower cost than many high-nickel alloys
What Is Hastelloy?
Hastelloy is a family of corrosion-resistant metal alloys primarily made of nickel, with varying additions of molybdenum, chromium, iron, and other elements. Produced under the trademark of Haynes International, common grades like Hastelloy C-22, C-276, and Hastelloy X are designed for extremely aggressive environments.
Main Hastelloy features:
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Exceptional resistance to a broad range of oxidizing and reducing chemicals
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Excellent resistance to pitting and crevice corrosion
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High performance under extreme temperatures and pressures
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Widely used in critical applications like aerospace, nuclear, and chemical plants
Chemical Composition Comparison
| Element | Alloy 20 (%) | Hastelloy C-276 (%) |
|---|---|---|
| Nickel (Ni) | 32–38 | 57 |
| Chromium (Cr) | 19–21 | 14.5–16.5 |
| Molybdenum (Mo) | 2–3 | 15–17 |
| Copper (Cu) | 3–4 | – |
| Iron (Fe) | Balance | 4–7 |
| Carbon (C) | <0.07 | <0.01 |
Verdict: Hastelloy, especially C-276, has a higher nickel and molybdenum content, giving it greater corrosion resistance in aggressive conditions.
Corrosion Resistance
Alloy 20
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Best known for resisting sulfuric acid
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Good performance in nitric acid and phosphoric acid
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Decent resistance to chloride-induced stress corrosion
Hastelloy
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Outstanding resistance to hydrochloric acid, sulfuric acid, nitric acid, and more
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Superior resistance to oxidizing and reducing agents
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Performs well in high-chloride and acidic environments
Verdict: Hastelloy offers a broader and more robust corrosion resistance profile than Alloy 20, especially in mixed chemical environments and under harsh conditions.
Mechanical Properties
| Property | Alloy 20 | Hastelloy C-276 |
|---|---|---|
| Tensile Strength | ~620 MPa | ~790 MPa |
| Yield Strength | ~300 MPa | ~355 MPa |
| Elongation | ~35% | ~60% |
| Hardness (HB) | ~200 | 200–240 |
| Density | ~8.1 g/cm³ | ~8.9 g/cm³ |
Verdict: Hastelloy is stronger and more ductile, making it more suitable for applications requiring higher mechanical performance in extreme environments.
Heat Resistance
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Alloy 20: Performs well in moderate temperatures, but not ideal for prolonged high-temperature service above 500°C.
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Hastelloy C-276: Performs reliably in environments with continuous exposure up to 1040°C depending on the grade.
Verdict: Hastelloy is better suited for high-temperature applications.
Fabrication and Weldability
Both Alloy 20 and Hastelloy are considered weldable and workable, but:
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Alloy 20: Easier to machine and fabricate, less tool wear
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Hastelloy: Requires more careful machining practices due to work-hardening behavior
Verdict: Alloy 20 is easier to fabricate, which may lower production time and cost in less demanding applications.
Cost Comparison
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Alloy 20: Generally more economical than Hastelloy due to lower nickel and molybdenum content
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Hastelloy: Considerably more expensive, reflecting its higher alloy content and specialized performance
Verdict: For cost-sensitive projects where extreme corrosion resistance is not mandatory, Alloy 20 may be the better choice.
Applications: When to Use Each
Alloy 20 Ideal Applications
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Sulfuric acid storage tanks and piping
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Pharmaceutical and food processing
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Heat exchangers and process piping
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Plastic and synthetic fiber manufacturing
Hastelloy Ideal Applications
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Chemical reactors and vessels exposed to mixed acids
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Pulp and paper bleaching equipment
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Desalination and marine applications
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Nuclear reactors and power plant components
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High-temperature, high-pressure environments
Verdict: Use Hastelloy in high-risk, high-performance environments. Choose Alloy 20 when corrosion resistance is essential, but budget or fabrication efficiency is also a concern.
Summary Comparison Table
| Feature | Alloy 20 | Hastelloy C-276 |
|---|---|---|
| Corrosion Resistance | High (esp. sulfuric) | Superior (all major acids) |
| Mechanical Strength | Moderate | High |
| Heat Resistance | Moderate | Excellent |
| Weldability | Easier | More demanding |
| Cost | Lower | Higher |
| Application Environments | Chemical, pharma | Chemical, nuclear, marine |
Final Verdict: Which Is Better?
It depends on your application.
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If your application deals primarily with sulfuric acid, operates at moderate temperatures, and requires good corrosion resistance at a reasonable cost, Alloy 20 is a great choice.
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If your environment involves mixed acids, high chlorides, oxidizers, or elevated temperatures, and failure is not an option, Hastelloy is the better option despite the higher cost.
Verdict: Hastelloy is better in terms of corrosion resistance, strength, and temperature tolerance, but Alloy 20 offers an excellent balance of performance and value for less extreme conditions.
Conclusion
Choosing between Alloy 20 and Hastelloy is not about which alloy is universally better—it’s about which one is right for your specific operating environment. By understanding the differences in corrosion resistance, mechanical strength, heat tolerance, and cost, you can make an informed decision that ensures long-term reliability and efficiency.
If you need support selecting the appropriate alloy or sourcing certified materials, contact sasaalloy. With extensive expertise in supplying high-performance alloys like Alloy 20 and Hastelloy, sasaalloy helps clients around the world achieve project success in the most challenging environments.
Post time: Aug-01-2025