Difference Between Hastelloy 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 C22 and Hastelloy C276.

We frequently see that some of these alloys, such as Hastelloy C22 and Hastelloy C276, get mixed up and/or welded together regularly. A higher percentage of chromium in Hastelloy C22 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). Hastelloy C22 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.

This blog will make an in-depth comparison of Hastelloy C22 and Hastelloy C276, and discuss their similarities and differences in chemical composition, mechanical properties, corrosion resistance, and applicable fields. By comparing the properties of these two alloys, I believe you will be able to better understand how to choose between these two alloys and how to take full advantage of their characteristics to ensure the reliability and performance of your equipment.

What is the difference between Hastelloy C276 and C22?

Properties

Hastelloy C22 and Hastelloy C276 are two variations of the same nickel-molybdenum alloy. Both are highly corrosion resistant across a wide range of applications, however robustness among the two varies greatly. Compared to C22, Hastelloy C276 is much more resistant to localized attack, allowing it to perform in chlorine-based environments with high temperatures and pressure. Additionally, with its increased iron content, C276 provides superior resistance to chloride pitting and crevice corrosion when compared to its counterpart. With such features in mind, it’s clear that for applications in harsh conditions — especially those related to chemical processing — Hastelloy C276 offers enhanced durability and strength that makes it an ideal choice for most needs.

Corrosion Resistance

Both alloys are known for their exceptional corrosion resistance in highly aggressive environments, such as wet chlorine gas, sulfuric and hydrochloric acid, and seawater. However, Hastelloy C22 has better resistance to localized corrosion, such as pitting and crevice corrosion, due to its higher chromium and molybdenum contents. This makes it a popular choice for components like valves, pumps, and manifolds in the chemical processing and pharmaceutical industries. On the other hand, Hastelloy C276 has a better overall corrosion resistance, especially in reducing and oxidizing environments, at higher temperatures. This makes it suitable for applications in the oil and gas industry, where well fluids and gases can be highly corrosive.

Mechanical

Hastelloy C22 and C276 both exhibit excellent mechanical properties, including high strength, ductility, and toughness, at both room and elevated temperatures. However, there are some differences. Hastelloy C22 has a lower work-hardening rate, making it easier to form and machine into complex shapes. At the same time, it has a lower yield strength and ultimate tensile strength than Hastelloy C276, but better impact strength. Hastelloy C276, on the other hand, has a higher yield and tensile strength than C22, but its hardness increases rapidly when exposed to high temperatures. This makes it more suitable for high-pressure and high-temperature applications, such as heat exchangers and reactors.

Cost

The cost of Hastelloy C22 vs C276 is another factor to consider when choosing the right alloy for your fasteners. Generally, Hastelloy C276 is more expensive than C22, due to its higher tungsten content and good overall properties. However, the exact cost will depend on the form, size, and quantity of fasteners you need, as well as the supplier you choose. It is always important to compare prices and quality from different suppliers before making a purchase.

Availability

Availability is the most essential material property. C22 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 C276 is available in some product forms, it can be difficult to find sanitary/high-purity grade tubing and fittings in alloy C276. We have seen that some valves in Hastelloy C (could be C-22 or C-276) are welded to tubing and fittings in C22. Product availability is a key to the completion of many projects.

Application of Hastelloy C276 and C22 in different fields

Hastelloy C22 Hastelloy C276 has a very similar range of applications. In practical applications, we should consider more details, such as the specific working environment of the material. We need to select corresponding materials according to different corrosive substances.

Hastelloy C22: Often used in environments where mixed acids are present (e.g., chlorides and oxidizing acids). Common applications include pharmaceutical industries, flue gas desulfurization systems, and chemical process equipment like reactors and pipes.

Hastelloy C276: Due to its versatile resistance to various chemicals, it is used in pulp and paper production, waste treatment, pollution control equipment, and in chemical processing components exposed to harsh acids.