MonEl

Monel refers to a family of nickel–copper alloys known for high strength and outstanding corrosion resistance. The best-known grades are Monel 400 and Monel K-500. Monel 400 is a solid-solution alloy containing roughly 60–70% nickel and 30–40% copper, with iron and manganese as common impurities. Monel K-500, in addition to nickel and copper, contains aluminum and titanium to enable age-hardening, yielding higher strength.

Monel alloys exhibit excellent resistance to corrosion in many environments, including seawater and a wide range of acids and alkalis. They maintain toughness at low temperatures and are non-magnetic. Most Monel alloys are not heat-treatable, with the exception of K-500, which gains strength through aging. They are typically welded and brazed with standard techniques, though work hardening and cost are considerations; machining can be challenging and often requires carbide tools and slow speeds.

Common uses include marine hardware, shipbuilding components such as propeller shafts and fasteners, valves, pumps, heat exchangers, and chemical processing equipment. Monel is valued for its combination of strength and corrosion resistance, particularly in aggressive saltwater and certain chemical service.

Limitations include cost and limited resistance to some oxidizing acids and hot, concentrated chloride environments. In addition, galvanic corrosion can occur when Monel is paired with dissimilar metals in chloride-containing media.