F321 UNS-S32100 ASTM-A182	Type 321 is essentially type 304 with addition of titanium that stabilizes carbides against sensitization.  This stabilized grade is more resistant to sensitization by welding or by long-term exposure at temperatures 0f 800 to 1500F, and the stabilized grades are the preferred materials when service involves exposure at these temperatures.
AL6XN UNSN08367 ASTM-B-366 WP6XN	AL6XN, although classified as nickel-base alloy by the UNS system, is part of the "superaustenitic" category of stainless steels.  The superaustenitic alloys were developed for improved resistance to chloride corrosion.
MONEL 400 UNS-N04400 ASTM-B-366 WPNC	Nickel and nickel alloys are used for a wide variety of applications, most of which involve corrosion resistance and/or heat resistance.  Monel 400 exceeds nickel in resistance to sulfuric and hydrofluoric acids and to brine.  Handling of waters, including seawater and brackish water, is a major area of application.  Monel is immune to chloride-ion SCC, which often is a factor in its selection.
HASTELLOY C-276 UNS-N10276 ASTM-B-366 WPC276	Significant additions of molybdenum make Hastelloy C276 highly resistant to pitting.  This alloy retains high strength and oxidation resistance at elevated temperatures, and has a high resistance to a wide variety of aqueous corrodents.