Hastelloy alloys have long been the gold standard of corrosion resistant bolts; only out performed by metals like Zirconium and Tantalum. This family of high performance nickel alloys can handle strong acids like hydrochloric, sulfuric, acetic, formic and phosphoric acids, yet each grade actually exhibits its own strengths in dealing with specific acids and niche environments. This blog will highlight the unique benefits of the 4 most common Hastelloy grades used for fasteners: C276, C22, B3, and C2000.
Hastelloy B3: Hydrochloric Acid
Hastelloy B3 fasteners provide industry with a material to handle hydrochloric acid at all concentrations and temperatures up to the boiling point. B3 also offers improved thermal stability over other B-type alloys, which helps to minimize fabrication and welding issues.
Hastelloy C22: Oxidizing Environments
Though all Hastelloy grades are known for their corrosion resistance, not all can handle oxidizing environments. (In fact, B grades will experience rapid corrosion failure in the presence of oxidizers.) The ability of C22 to provide protection from strong oxidizers such as ferric acids, cupric chlorides and nitric acid – in addition to non-oxidizing acids like sulfuric and hydrochloric– makes it unique. C22 also provides better resistance to saturated wet chlorine environments, as well as chloride-induced pitting than C276.
Hastelloy C276: Versatility
C276 by far the most common grade of Hastelloy used for bolting. Known for providing very good protection against a broad range of acids from moderately oxidizing to strong reducing conditions. Though it is most often used for its resistance to hot acids, Hastelloy C276fasteners are also very resistant to salt water environments, particularly crevice attack as well as pitting and stress corrosion cracking. Because of Hastelloy C276’s popularity, this grade is available in almost any size whereas the other grades, B3, C22 and C2000 may have limited availability particularly in sizes less the ½”.
Hastelloy C2000: Superior Resistance
C2000 combines the high molybdenum content of C276 with the high chromium content of C22, resulting in a superior corrosion resistant alloy that provides excellent resistance to both reducing and oxidizing environments. In particular C2000 provides enhanced corrosion resistance to sulfuric acid, as well as process streams contaminated with ferric ions.