Hastelloy B2 is a nickel-molybdenum alloy that is strengthened in a solid solution. It is resistant to sulfuric, acetic, and phosphoric acids, as well as reducing environments like hydrogen chloride gas. The primary alloying element, molybdenum, offers significant resistance to corrosion in reducing environments. Due to its resistance to the formation of grain-boundary carbide precipitates in the weld heat-affected zone, this nickel steel alloy can be used in the as-welded condition.

Hydrochloric acid is extremely resistant to this nickel alloy at all temperatures and concentrations. Hastelloy B2 is also highly resistant to stress corrosion cracking, knife-line attack, and heat-affected zone attack. Pure sulfuric acid and a number of non-oxidizing acids are resistant to Alloy B2.

Due to its poor resistance to corrosion in oxidizing environments, alloy B-2 should not be used in oxidizing media or in the presence of ferric or cupric salts because these salts may result in rapid, premature corrosion failure. When iron and copper come into contact with hydrochloric acid, these salts might form. As a result, the presence of these salts may cause the alloy to fail prematurely if it is used in conjunction with iron or copper piping in a system containing hydrochloric acid. Additionally, due to its decreased ductility at temperatures between 1000 and 1600 degrees Fahrenheit, this nickel steel alloy should not be utilized.