ALLOY 400 _ UNS N04400 common trade names Monel 400®, Nickelvac® 400, Nicorros® 400 Monel 400® is a nickel-copper alloy that is hardened by cold working only. Monel 400® has low corrosion rate in flowing seawater, therefore it is widely used in marine applications. Monel 400® also has excellent resistance to stress corrosion cracking in most freshwaters. Monel 400® can be used in temperatures up to 1000 ºF. The alloy has great mechanical properties at subzero temperatures. Available forms are seamless pipe, welded pipe, seamless tube, welded tube, bar, wire, sheet, plate, forgings, pipe fittings and flanges.