Monel: Characteristics, Uses And Problems
MONEL: CHARACTERISTICS, USES AND PROBLEMS
Margot Gayle, David Look, John Waite. Metals in America's Historic Buildings. Washington,DC: National Park Service, 1995.
L. William Zahner. Architectural Metals. New York: John Wiley & Sons, 1995.
This standard includes general information on the characteristics
and common uses of Monel and identifies typical problems associated
with this material along with common causes of its deterioration.
Characteristics of Monel:
- a nickel alloy containing 65-70 percent nickel, 20-29 percent
copper, and small amounts of iron, manganese, silicon and
- discovered due to the efforts of Robert Crooks Stanley, who
worked for the International Nickel Company (INCO) in 1905;
the new alloy was named in honor of the president of the
company - Ambrose Monell; the last "L" was dropped for trademark purposes.
- stronger than steel
- resistant to corrosion
- low coefficient of thermal expansion
- highly resistant to alkalis
- improved sanitation
- fairly inexpensive
- can be welded, brazed and soldered
- in the 1920s and 30s, Monel was available in both hot-rolled
and cold-rolled sheets; today it is available in plates, rod & bar, tubing, and more rarely in castings
- 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- popular between 1909 and World War II when nickel was diverted to war use and lower priced stainless steel superceded Monel.
- 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
- 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 mid-20th century
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
NATURAL OR INHERENT PROBLEMS
- Surface discoloration: Can occur from exposure to atmospheric
- Pitting: Can occur if exposed to stagnant salt water.
- 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 not
- Acid and alkaline oxidizing salts, ferric chloride,
ferric sulfate, cupric chloride, stannic chloride,
mercuric chloride and silver nitrate are all corrosive to
- resistance to sulfurous acid varies depending on climatic
- organic acids (acetic and fatty acids) have little to no
effect on Monel
- Stress corrosion cracking: Exposure to aerated hydrofluoric
acid in moist conditions can cause this to occur.
- 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.
END OF SECTION