AL-6XN vs Hastelloy: Materials, Equivalents, Key Differences
Key Differences Between AL6XN vs Hastelloy C-22
Environments with high temperatures, low pH, and aggressive chemicals require a material with high corrosion resistance, which traditional stainless steel alloys fail to attain. The unique properties and quick availability of super-austenitic stainless steel alloys AL-6XN® and Hastelloy® C-22® make them both favorable for highly corrosive environments, but they still have some important differences.
Corrosion Resistance
Both AL-6XN® alloy and Hastelloy® C-22® have a face-centered cubic lattice structure and contain chromium, molybdenum, and nickel as the primary ingredients for providing corrosion resistance. However, C-22 has more of these elements, which gives it better resistance to chlorides, mineral acids, and high-temperature oxidation. The chromium adds resistance to pitting, stress corrosion cracking, and crevice corrosion. The molybdenum provides greater resistance against reducing media such as hydrochloric, formic, and phosphorous acid mediums. The nickel better resists attacks from chlorides and other halides. Both AL-6XN and C-22 are materials that can withstand very corrosive environments, but they each have material design limitations and application restrictions.
AL-6XN
AL-6XN was initially developed for seawater applications. However, it is also an excellent material for products such as sports drinks, ketchup, soy, barbecue, salsa, and other products that eat away at regular materials. AL-6XN is also found to resist corrosive attacks from personal care products such as deodorant and hair care products. AL-6XN is usually the best choice for corrosion resistance in applications that require excellent formability, strength, and weldability, which is impossible by any conventional stainless steel alloy.
C-22
C-22 is designed to tolerate extremely corrosive environments. This material's advantage is that it can withstand both oxidizing and reducing acids at high temperatures, exhibiting high resistance to localized corrosion. C-22 has been used in the chemical, food, beverage, and pharmaceutical industries where high temperatures and high concentrations are needed. Some of the processes use extremely high concentrations of chlorides at high temperatures. C-22 works effectively in these aggressive conditions.
However, every material has a threshold limit. AL-6XN will not hold well after reaching this limit, so it is beneficial to opt for C-22 beyond this limit.
AL-6XN is a cost-effective alternative to 316L for higher corrosion resistance and strength. It is considerably less expensive than C-22, yet it provides a comparable level of corrosion resistance.
AL-6XN and C-22 are readily available in forms such as tube, pipe, sheet, plate, bar, billet, and forgings from which components such as fittings, valves, fasteners, and castings can be obtained. Many sanitary piping components made from AL-6XN alloy are readily available.
“AL-6XN” is a registered trademark of ATI Properties, Inc., licensed to Allegheny Ludlum Corp. "Hastelloy” and “C-22” are registered trademarks of Haynes International.
ABOUT CSI
Central States Industrial Equipment (CSI) is a leader in distribution of hygienic pipe, valves, fittings, pumps, heat exchangers, and MRO supplies for hygienic industrial processors, with four distribution facilities across the U.S. CSI also provides detail design and execution for hygienic process systems in the food, dairy, beverage, pharmaceutical, biotechnology, and personal care industries. Specializing in process piping, system start-ups, and cleaning systems, CSI leverages technology, intellectual property, and industry expertise to deliver solutions to processing problems. More information can be found at www.csidesigns.com.