Choosing the right material for a particular application is crucial, especially for equipment in demanding environments such as chemical processing, oil and gas, and power generation industries. Two commonly used materials for this purpose are Hastelloy C22 and Stainless Steel 316. Both are popular due to their corrosion-resistant properties but differ in composition, properties, and cost. This blog post will closely examine these two materials and understand their differences.
What is Hastelloy C22?
Hastelloy C22 is a nickel-chromium-molybdenum alloy with excellent corrosion resistance in oxidizing and reducing environments. It is known for its ability to resist localized corrosion such as pitting, crevice attack and stress corrosion cracking due to its high chromium content. Its good weldability makes it popular in petrochemical, chemical processing and pollution control industries.
What is Stainless Steel 316?
Stainless Steel 316 (SS316) is an austenitic chromium-nickel alloy containing molybdenum. It is a more corrosion-resistant steel than SS304, with higher strength and better toughness properties. SS316 is commonly used in chemical, food-processing, marine, and oil & gas industries.
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Differences Between Hastelloy C22 and Stainless Steel 316
Composition
Hastelloy C22 is a nickel-chromium-molybdenum-tungsten alloy with enhanced resistance to corrosive environments, particularly in halide-containing aqueous solutions. It comprises 22% chromium, 13% molybdenum, and 3% tungsten, with smaller amounts of iron, nickel, and other elements. On the other hand, Stainless Steel 316 is a chromium-nickel-molybdenum alloy that contains 16% chromium, 10% nickel, and 2% molybdenum. It also has small amounts of carbon, manganese, phosphorus, sulfur, and silicon. The higher nickel and molybdenum content of Hastelloy C22 makes it more resistant to pitting and crevice corrosion than Stainless Steel 316.
Properties
Hastelloy C22 has superior corrosion resistance to various aggressive media, including oxidizing and reducing environments. It also has excellent resistance to intergranular attack, stress corrosion cracking, and erosion. Its thermal stability and resistance to oxidation up to 1250°C (2282°F) make it suitable for high-temperature applications. Stainless Steel 316, on the other hand, is widely used in aqueous applications and has good resistance to corrosion in most environments, except highly oxidizing and chloride-containing solutions. It has strength and flexibility at elevated temperatures and can withstand repeated heating and cooling cycles.
Cost
Hastelloy C22 is a premium alloy and is more expensive than Stainless Steel 316. Its high nickel, molybdenum, and tungsten content makes it more difficult to fabricate and machine. Its corrosion resistance, however, justifies its cost when used in critical applications where downtime and maintenance costs are high. Stainless Steel 316 is a more economical material with good corrosion resistance in most applications. It is readily available, easily fabricated, and machined, making it a popular choice for general-purpose equipment.
Applications
Hastelloy C22 is commonly used in chemical processing, petrochemical, and oil and gas industries. It is used for vessels, heat exchangers, pumps, valves, and fittings that handle corrosive fluids such as acids, chlorides, and sulfur compounds. It is also used in pollution control equipment, scrubbers, and flue gas desulfurization systems. Stainless Steel 316 is widely used in applications that require good corrosion resistance, such as food processing, pharmaceutical, and marine industries. It is used for tanks, piping, pumps, and fittings that handle water, steam, and mild corrosives.
Conclusion
Choosing the right material for a particular application requires careful consideration of various factors such as corrosion resistance, mechanical properties, cost, and availability. Hastelloy C22 and Stainless Steel 316 are two materials commonly used in corrosive environments due to their excellent corrosion resistance. While Hastelloy C22 offers superior resistance to aggressive media and high-temperature applications, it is more expensive and difficult to machine. Stainless Steel 316, on the other hand, is a more economical option that offers good corrosion resistance in most applications. Ultimately, choosing these two materials depends on the application’s specific requirements and the available budget.
