Monel or Alloy 400, is a nickel alloy containing 65-70 percent nickel, 20-29 percent copper, and small amounts of iron, manganese, silicon and carbon discovered due to the efforts of Robert Crooks Stanley, who worked for the International Nickel Company (INCO) in 1901. The new alloy which was named in honor of the president of the company, Ambrose Monell, was said to be:
Stronger than steel
Resistant to corrosion
Low coefficient of thermal expansion
Highly resistant to alkalis
Improved sanitation (??)
Can be welded, brazed and soldered
In the 1920s and 30s, Monel was available in both hot-rolled and cold-rolled sheets typical finishes included brightly polished, "hand-forged" black, and two-toned in outdoor applications, Monel develops a patina ranging from light gray-green to medium brown.
Popular between 1909 and the mid 1950s
Available in sheet form for architectural applications
Installed as a sheet roofing membrane in 1908
In the late 1920s, Monel was began to be used for grocery coolers, countertops, sinks, laundry and food preparation appliances, roofing and flashing
Other uses for sheet and plate Monel were ductwork, flashing, gutters and downspouts, mail chutes, laundry chutes, elevator fittings, lighting fixtures, and skylights
Monel castings were also popular and included grilles, rosettes, plaques, handrail fittings, molding, pilasters, mullions, and door jambs
Monel forgings were used for hardware
Monel bar and rod stock were used for window screens, gates, public directory boards, railings, and divider strips in terrazzo floors
Other common applications for Monel included tie wire for securing lath in plaster walls and suspended ceilings, fasteners for tile roofs and anchors for stone cladding
Monel began to be displaced by stainless steel in the 1950s, as stainless steel could produce the same forms at a lower cost (due to use of less nickel)
A modified, less expensive use of Monel included laminating a thin sheet of Monel to an inexpensive backing material; two examples include Monel-clad steel and Monel-laminated plywood
Monel is still manufactured by INCO, primarily in the form of sheet goods; cast and rolled forms are also available, but are extremely expensive
Surface discoloration: Can occur from exposure to atmospheric condition
Pitting: Can occur if exposed to stagnant salt water.
Galvanic corrosion: Metals, such as aluminum, zinc and iron will corrode when in contact with Monel and exposed to severe weather conditions. Therefore, use of these metals as fasteners for Monel should be avoided.
Stress corrosion cracking: Exposure to aerated hydrofluoric acid in moist conditions can cause this to occur.
Nitric oxides and sulfur dioxides, combined with water, are very corrosive to Monel.
Nitric and nitrous acids can be very corrosive to Monel at room temperature
Hypochlorites are severely corrosive to Monel if notdiluted
Acid and alkaline oxidizing salts, ferric chloride, ferric sulfate, cupric chloride, stannic chloride, mercuric chloride and silver nitrate are all corrosive to Monel.
Resistance to sulfurous acid varies depending on climatic conditions
Organic acids (acetic and fatty acids) have little to no effect on Monel