Hastelloy C22 vs C276 | Difference Between C22 and C276
Material selection is a combination of property, price, and product availability. Many materials are discussed in the industry, but very few are produced in the product forms required for a project. We often face the difficult decision of which material is the right choice for our purpose, especially when comparing two alloys like Hastelloy® C-22® and Hastelloy® C-276®.
We frequently see that some of these alloys, such as Hastelloy® C-22® and Hastelloy® C-276®, get mixed up and/or welded together regularly.
Hastelloy is a representation of a family of corrosion-resistant alloys. Both C-22 and C-276 are from the Hastelloy family. That similarity can lead to confusion, but C-22 has better overall corrosion resistance than C-276, often referred to as the upgrade from C-276.
A higher percentage of chromium in C-22 provides better corrosion resistance in oxidizing environments, significantly improving the material’s life. Common severe oxidizing mediums include sodium chloride (NaCl), hydrochloric acid (HCl), and sulphuric acid (H2SO4). C-22 also shows outstanding resistance to ferric and cupric chlorides, acetic anhydride, formic and acetic acids, hot contaminated organic and inorganic acids, brine solutions, and seawater.
Hastelloy family
| Alloy | UNS Number | Chromium | Nickel | Molybdenum |
|---|---|---|---|---|
| Hastelloy C-22® | N06022 | 22% | 56% | 13% |
| Hastelloy C-276 | N10276 | 16% | 57% | 16% |
Hastelloy C-22 has been found to have outstanding resistance to pitting, crevice, and stress corrosion cracking when compared to Hastelloy C-276.
Hastelloy Family
Hastelloy C-22 has been found to have exceptional resistance to pitting, crevice, and stress corrosion cracking when compared to Hastelloy C-276.
Both C-22 and C-276 have been tested in oxidizing mediums for pitting and crevice corrosion. It has been proven that C-22 is more resistant to the oxidizing medium, even at higher temperatures. However, C-22 and C-276 behave the same in reducing environments. Reducing agents include oxalic acids (C2H2O4), formic acids (HCOOH), and phosphorous acids (H2PO4).
Critical Pitting and Critical Crevice Corrosion Temperatures
| Alloy | CPT* (°C) | CPT* (°F) | CCCT** (°C) | CCCT** (°F) |
|---|---|---|---|---|
| Hastelloy C-22® | > 150 | > 302 | 102 | 212 |
| Hastelloy C-276 | 150 | 302 | 80 | 176 |
Composition and Properties
Hastelloy C276 and C22 are both high-performance nickel-chromium-molybdenum alloys, but their distinct compositions lead to different properties. Hastelloy C276 contains a higher nickel content and a lower chromium content compared to Hastelloy C22 chromium. Additionally, Hastelloy C276 boasts a higher molybdenum content than Hastelloy C22. These variations in composition significantly influence their corrosion resistance, mechanical properties, and performance at high temperatures. The higher chromium content in Hastelloy C22 enhances its resistance to oxidizing environments, while the increased molybdenum in Hastelloy C276 provides superior resistance to reducing environments and pitting corrosion.
Critical Pitting and Critical Crevice Corrosion Resistance Temperatures
Corrosion Resistance Comparison
When it comes to corrosion resistance, both Hastelloy C276 and C22 are exceptional, but they shine in different scenarios. Hastelloy C276 excels in oxidizing environments, such as those involving nitric acid and chlorine gas, offering better resistance to pitting corrosion, crevice corrosion, and stress corrosion cracking. This makes it a preferred choice for chemical processing, oil and gas, and power generation industries. On the other hand, Hastelloy C22 demonstrates superior resistance in reducing environments, such as hydrochloric acid and sulfuric acid. Its ability to withstand these harsh conditions makes it ideal for applications where greater corrosion resistance is crucial.
High-Temperature Performance
In terms of high-temperature performance, Hastelloy C276 has a slight advantage over Hastelloy C22. Hastelloy C276 can endure temperatures up to 1900°F (1037°C), whereas Hastelloy C22 can withstand up to 1250°F (676°C). This higher thermal stability and resistance to grain boundary precipitation make Hastelloy C276 a popular choice for applications in high-temperature environments. These properties are particularly important in industries where materials are exposed to extreme heat, ensuring longevity and reliability under such conditions.
Mechanical Properties and Applications
Both Hastelloy C276 and C22 exhibit excellent mechanical properties, including high strength, ductility, and toughness. Hastelloy C276 has a slightly higher yield strength and ultimate tensile strength compared to Hastelloy C22. However, Hastelloy C22 offers better formability and weldability, making it a preferred choice for applications requiring complex shapes and welding. These mechanical properties make both alloys suitable for a wide range of applications, including chemical processing, oil and gas, power generation, and aerospace. The choice between the two often depends on the specific requirements of the application, such as the need for greater corrosion resistance or better formability.
Weldability
C-22 has been regularly used as weld filler/consumable insert material because it provides better weldability and over-alloying ability, thus improving corrosion resistance. C-22 also offers excellent resistance to intergranular corrosion in the heat-affected zone of the weldments compared to C-276
Reference: Haynes technical H-2032 0621r information
AVAILABILITY
Availability is the most essential material property. C-22 is readily available in the required product forms for the industry, whether that form is pharmaceutical-grade tubing fittings or round bar, sheet, and plate for other fabrication purposes. It is important to have the material available in reasonable quantity and in the required time.
Although C-276 is available in some product forms, it can be difficult to find sanitary/high-purity grade tubing and fittings in C-276. We have seen that some valves in Hastelloy C (could be C-22 or C-276) are welded to tubing and fittings in C-22. Product availability is a key to the completion of many projects.
Price Comparison
The cost per pound for these alloys is the same, depending on the product form. C-22 is 2% less dense, giving it an edge on the price per square foot.
Each of these factors supports Hastelloy C-22 as the choice for longer life, better performance, and better return on investment (ROI).
Expert Bio
Yogini Dhopade, Product Manager - Alloys
Yogini Dhopade has three degrees, speaks four languages, and has traveled to ten different countries across the world. She has an unmatchable passion for metals and spends her time at CSI managing everything related to corrosion-resistant alloys.
ABOUT CSI
Central States Industrial Equipment (CSI) is a leader in distribution of hygienic pipe, valves, fittings, pumps, heat exchangers, and MRO supplies for hygienic industrial processors, with four distribution facilities across the U.S. CSI also provides detail design and execution for hygienic process systems in the food, dairy, beverage, pharmaceutical, biotechnology, and personal care industries. Specializing in process piping, system start-ups, and cleaning systems, CSI leverages technology, intellectual property, and industry expertise to deliver solutions to processing problems. More information can be found at www.csidesigns.com.