View Sample Alloy Digest Data Sheet (PDF) Since 1952, Alloy Digest has been the leading reference for materials property data on metals and alloys used throughout the world. Featuring graphs, charts and tables, these sheets give facts and figures on composition or characterization, physical and mechanical properties, heat treatment, and machinability.MAT 21 is a newly developed nickel-20 chromium-20 molybdenum-2 tantalum alloy. The very high molybdenum and tantalum content gives excellent general, pitting, and crevice corrosion resistance. The alloy was developed to be resistant to sulfuric acid dew point corrosion. Applications include scrubbers for flue gas desulfurization and heat exchangers to recover waste heat at low temperatures in fossil fuel fired plants. The corrosion resistance of welded joints does not degrade in the as-welded condition.