Hastelloy C22 vs. Hastelloy C276

Attribute	Hastelloy C22	Hastelloy C276
Composition	Ni 56%, Cr 22%, Mo 13%, Fe 3%, W 3%	Ni 57%, Cr 16%, Mo 16%, Fe 5%, W 4%
Temperature Resistance	Up to 1250°C	Up to 1200°C
Corrosion Resistance	Excellent resistance to a wide range of corrosive environments	Excellent resistance to oxidizing and reducing environments
Applications	Chemical processing, pollution control, waste treatment	Chemical processing, pharmaceutical, pulp and paper production

Composition

Hastelloy C22 and Hastelloy C276 are both nickel-based alloys that are known for their excellent corrosion resistance in a wide range of aggressive environments. However, they have slightly different compositions that give them unique properties.

• Hastelloy C22 is composed of nickel, chromium, molybdenum, and tungsten, with trace amounts of iron, cobalt, and manganese. This composition gives it superior resistance to pitting, crevice corrosion, and stress corrosion cracking.
• On the other hand, Hastelloy C276 contains higher levels of nickel and molybdenum, along with chromium and tungsten. This composition provides better overall corrosion resistance in oxidizing and reducing environments.

Corrosion Resistance

Both Hastelloy C22 and Hastelloy C276 are highly resistant to a wide range of corrosive media, including acids, salts, and oxidizing agents. However, their specific compositions give them different strengths in certain environments.

• Hastelloy C22 is particularly well-suited for applications involving mixed acids, such as sulfuric acid with hydrochloric acid, due to its high chromium and molybdenum content.
• On the other hand, Hastelloy C276 is better suited for environments with high concentrations of chlorides, such as seawater or brine solutions, thanks to its higher nickel and molybdenum content.

Temperature Resistance

Both alloys exhibit excellent resistance to high temperatures, making them suitable for use in a variety of industrial applications where heat and corrosion are concerns. However, there are slight differences in their temperature capabilities.

• Hastelloy C22 has a higher temperature limit for continuous service compared to Hastelloy C276, making it a better choice for applications where elevated temperatures are a factor.
• On the other hand, Hastelloy C276 has better overall resistance to hot sulfuric acid environments, making it a preferred choice for applications involving this corrosive medium.

Weldability

Both Hastelloy C22 and Hastelloy C276 are readily weldable using conventional welding techniques. However, there are some differences in their welding characteristics that may influence the choice of alloy for certain applications.

• Hastelloy C22 has excellent weldability and can be easily welded using techniques such as TIG, MIG, and SMAW. It also exhibits good resistance to post-weld cracking and stress corrosion.
• On the other hand, Hastelloy C276 may require more care during welding to avoid issues such as hot cracking and reduced corrosion resistance in the heat-affected zone. However, with proper welding procedures, it can still be successfully welded.

Applications

Both Hastelloy C22 and Hastelloy C276 are widely used in a variety of industries where corrosion resistance is critical, such as chemical processing, pharmaceuticals, and oil and gas production. Each alloy has specific applications where it excels.

• Hastelloy C22 is often chosen for applications involving mixed acids, such as pickling solutions, chlorination systems, and chemical processing equipment.
• On the other hand, Hastelloy C276 is preferred for applications in harsh environments with high chloride concentrations, such as seawater desalination plants, pulp and paper processing, and flue gas desulfurization systems.