What is the difference between C22 and C276?

What is the difference between C22 and C276?

Material selection is a combination of performance, price, and product availability. There are many materials discussed in the industry, but few can be produced in the product form required for a project. We are often faced with a difficult decision: which material is our best choice, especially when comparing two alloys such as Hastelloy C-22 and Hastelloy C-276.

We often see that some of these alloys, such as Hastelloy C-22 and Hastelloy C-276, are often mixed 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 upgraded version of C-276.

The higher percentage of chromium in C-22 provides 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, thermally contaminated organic and inorganic acids, brine solutions and seawater.

Hastelloy Alloy Series

Hastelloy family

Hastelloy Series
Hastelloy C-22 was found to have 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 offer better resistance to oxidizing media, even at higher temperatures. However, C-22 and C-276 perform equally in reducing environments. Reducing agents include oxalic acid (C2H2O4), formic acid (HCOOH) and phosphorous acid (H2PO4).

Composition and Properties
Both Hastelloy C276 and C22 are high performance nickel-chromium-molybdenum alloys, but their different compositions lead to different properties. Hastelloy C276 contains a higher nickel content and a lower chromium content than Hastelloy C22 chromium. In addition, Hastelloy C276 has a higher molybdenum content than Hastelloy C22. These composition changes significantly affect their corrosion resistance, mechanical properties, and high temperature performance. The higher chromium content in Hastelloy C22 enhances its resistance to oxidizing environments, while the increased molybdenum content in Hastelloy C276 provides superior resistance to reducing environments and pitting.

Critical Pitting and Critical Crevice Corrosion Withstand Temperature
Corrosion Resistance Comparison
When it comes to corrosion resistance, both Hastelloy C276 and C22 excel, but they shine in different situations. Hastelloy C276 excels in oxidizing environments, such as those involving nitric acid and chlorine, with better 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. Hastelloy C22, on the other hand, exhibits excellent corrosion resistance in reducing environments, such as hydrochloric and sulfuric acids. Its ability to withstand these harsh conditions makes it ideal for applications that require greater corrosion resistance.

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 temperatures 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 the material is exposed to extreme heat to ensure the longevity and reliability of the material under such conditions.