Hastelloy B2 is a nickel-molybdenum alloy with significant resistance to reducing environments, such as hydrogen chloride gas and sulfuric, acetic and phosphoric acids. Hastelloy B2 provides resistance to pure sulfuric acid and a number of non-oxidizing acids. The alloy should not be used in oxidizing media or where oxidizing contaminants are available in reducing media. Premature failure may occur if alloy B2 is used where iron or copper is present in a system containing hydrochloric acid.

Industry users like the resistance to a wide range of organic acids and the resistance to chloride-induced stress-corrosion cracking.

Hastelloy B2 resists the formation of grain boundary carbide precipitates in the weld heat-affected zone, making it suitable for most chemical process applications in the as-welded condition. The heat-affected weld zones have reduced precipitation of carbides and other phases to ensure uniform corrosion resistance.
Alloy B2 also has excellent resistance to pitting and stress corrosion cracking.

Alloy B2 (UNS N10665 / W.Nr. 2.4617) is a solid solution strengthened, nickel-molybdenum alloy, typically used in extreme reducing conditions. B2 has significantly lower carbon, silicon and iron compared to its’ predecessor, Alloy B (UNS N10001), making the alloy less susceptible to decreased corrosion resistance in the weld zone, in the as-welded condition. Controlling other alloying elements such as iron and chromium
solved other issues concerning fabricability. Stringent chemistry control along with years of development has resulted in the alloy used today, both in Alloy B2 and Alloy B-3 Today, Alloy B2 with restricted chemistry can be used in the welded condition and is less susceptible to SCC under many conditions. As always, care must taken in selecting the right alloy for the desired application.