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Historic Preservation - Technical Procedures

Spectitle:

Monel: Characteristics, Uses And Problems

Procedure code:

0501016S

Source:

20Th Century Bldg Materials (Ed. Tom Jester, Nps)

Division:

Metals

Section:

Metal Materials

Last Modified:

11/12/2014

Details:

Monel: Characteristics, Uses And Problems



MONEL: CHARACTERISTICS, USES AND PROBLEMS

 

REFERENCES:

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.


INTRODUCTION

Characteristics of Monel:

-    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 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

-    malleable

-    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


TYPICAL USES

-    popular between 1909 and World War II when nickel was diverted to war use and lower priced stainless steel superceded Monel.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
    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 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
    conditions.

-    Pitting: Can occur if exposed to stagnant salt water.

-    Corrosion:

    -    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
         diluted

    -    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

-    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
 


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