Nickel-molybdenum alloys, or B-type alloys, are known for their excellent resistance to nonoxidizing (reducing) media, such as hydrochloric and sulfuric acids. The original B alloy (N10001) was invented in the 1920s, and it had a nominal composition of Ni-28Mo-5Fe0.3V, with a maximum carbon content of 0.05 wt% and a maximum silicon content of 1 wt%. The alloy was used successfully for many years, but it suffered an important drawback in that fabricated components required a solution heat treatment in order to avoid corrosion attack in the weld HAZs. Experimental work from 1958 to 1960 indicated that the corrosion resistance of the alloy could be significantly improved by reducing the carbon, iron, and silicon levels (Ref 4, 5). However, the achievement of very low carbon levels on a production scale did not occur until the invention of the argon-oxygen decarburization (AOD) melting process (Ref 6). This enabled the commercialization of an improved nickel-molybdenum material, B-2 alloy (N10665), in the early 1970s (Ref 7).