What is the difference between C22 and C276?
Material selection involves considering factors such as performance, price and product availability. There are many materials discussed in the industry, but only a few can actually be produced in the form required for a project. We are often faced with a difficult decision as to which material is best for our application, especially when comparing Hastelloy C-22 and Hastelloy C-276.
We often see alloys such as Hastelloy C-22 and Hastelloy C-276 being confused and/or welded together.
Hastelloy is a representative of the corrosion resistant alloy family. Both C-22 and C-276 belong to the Hastelloy family. This similarity can cause confusion, but C-22 has better overall corrosion resistance than C-276 and is often referred to as an upgrade of C-276.
The higher chromium content in C-22 gives it better corrosion resistance in oxidizing environments, which significantly extends the service life of the material. Common strong oxidizing media include sodium chloride (NaCl), hydrochloric acid (HCl) and sulfuric acid (H2SO4). C-22 also exhibits excellent resistance to ferric and cupric chlorides, acetic anhydride, formic and acetic acids, high temperature contaminated organic and inorganic acids, brine solutions, and seawater.
Hastelloy Alloy Family
Hastelloy C-22 exhibits superior resistance to pitting, crevice corrosion, and stress corrosion cracking compared to Hastelloy C-276.
Both C-22 and C-276 have been tested for pitting and crevice corrosion in oxidizing media. C-22 has been shown to better withstand oxidizing media, even at higher temperatures. However, C-22 and C-276 perform equally well in reducing environments. Reducing agents include oxalic acid (C2H2O4), formic acid (HCOOH), and phosphorous acid (H2PO4).
Composition and Properties
Hastelloy C276 and C22 are both high performance nickel-chromium-molybdenum alloys, but their different compositions determine their properties. Compared to Hastelloy C22, Hastelloy C276 has a higher nickel content and a lower chromium content. In addition, Hastelloy C276 also has a higher molybdenum content than Hastelloy C22. These compositional differences significantly affect their corrosion resistance, mechanical properties, and high-temperature performance. The higher chromium content in Hastelloy C22 enhances its corrosion resistance in oxidizing environments, while the higher molybdenum content in Hastelloy C276 gives it excellent corrosion resistance in reducing and pitting environments.
Critical Pitting and Critical Crevice Corrosion Resistance Temperature
Corrosion Resistance Comparison
Both Hastelloy C276 and C22 excel in corrosion resistance, but they perform differently in different environments. Hastelloy C276 excels in oxidizing environments, such as those containing nitric acid and chlorine, with superior resistance to pitting, crevice corrosion, and stress corrosion cracking. This makes it a top choice for the chemical processing, oil and gas, and power generation industries. On the other hand, Hastelloy C22 performs well in reducing environments such as hydrochloric and sulfuric acids. Its ability to withstand these harsh conditions makes it an ideal choice for applications where corrosion resistance is critical.
High Temperature Performance
Hastelloy C276 slightly outperforms Hastelloy C22 in terms of high temperature performance. Hastelloy C276 can withstand temperatures up to 1900°F (1037°C), while Hastelloy C22 can withstand up to 1250°F (676°C). 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 the material is exposed to extreme temperatures, ensuring the material's service life and reliability in such conditions.
Mechanical Properties and Applications
Both Hastelloy C276 and C22 have excellent mechanical properties, including high strength, ductility, and toughness. Hastelloy C276 has slightly higher yield strength and ultimate tensile strength than Hastelloy C22. However, Hastelloy C22 has better formability and weldability, making it the 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 higher corrosion resistance or better formability.
