Monel® alloys are nickel-based alloys that contain between 29 and 33 percent copper. Initially created by metallurgist Robert Crooks Stanley and patented in 1905 by the International Nickel Company. The metal was given the name Monel in honor of the then-director of International Nickel. Not surprisingly, Stanley later became Director of International Nickel.
Types of Monel
There are six types of Monel. All contain a large percentage of nickel (up to 67%), while some iron, manganese, carbon, and/or silicon. Small additions of aluminum and titanium, which form the K-500 alloy, increase strength, particularly at high temperatures, making it useful in aerospace applications.
| Designation | Cu % | Al % | Ti % | Fe % | Mn % | Si % | Ni % |
| Monel 400 | 28-34 | - | - | 2.5 max. | 2.0 max. | - | 63 min. |
| Monel 405 | 28-34 | - | - | 2.5 max. | 2.0 max. | 0.5 max. | 63 min. |
| Monel K-500 | 27-33 | 2.3-3.15 | 0.35-0.85 | 2.0 max. | 1.5 max. | - | 63 min. |
Monel® alloys are most often found in chemical plant equipment due to their strong resistance to chemical corrosion. They are also used in the aerospace industry. Products built with Monel (particularly before the advent of stainless steel) include heat exchangers, screw machine products, wind instruments, piping systems, fuel and water tanks, kitchen sinks, and roofing.
Pros of Monel
Monel® alloys have a great deal to offer. Prior to the 1950s, they were the "go to" choice for many critically important industries. It could also be easily welded, soldered, and brazed. This is because of its:
high corrosion resistance to acids and alkalis
high mechanical strength
good ductility (easy to shape and form)
resistance to alkalis
relatively low cost
availability in different forms including hot and cold-rolled sheets, plates, rods, bars, and tubes
attractive appearance and finishes, including a gray-green patina similar to copper
