Historic Monel: the alloy that time forgot

In 2019 I was introduced to a material I had only heard of in passing, Monel^®*.
Having previously come across it through the wrought craft of Samuel Yellin, a field trip to the southern tip of Manhattan placed me in front of a gleaming Monel elevator in an art-deco lobby. My interest was piqued. What was this alloy, how was it used and was it still popular?

In an attempt to hunt down interiors, I found redevelopment of department stores and banks, where the metal had flourished, had sadly led to total loss. I also discovered I was not alone in my ignorance. The break-up of the International Nickel Company (INCO) had thrown proprietary research to the wind, while conservators relied on dated marketing material for information. Worse, contractors were dumping Monel significantly before the end of its life cycle.

Monel has been with us since 1905. It was one of the sole “natural” alloys refined directly from its ore and fit to any and every purpose, a trailblazer for stainless steel that is still found in our built environment today.[1]

Like many metallurgical quests, Monel had its roots in alchemy. Chemists David H. Browne, Victor Hybinette and Robert C. Stanley were all attempting to find a more affordable route to nickel silver from the sulphur laden ores of Sudbury, Ontario.

Stanley ultimately refined the first ingot and, currying favor with his employer, named it after INCO Chairman Ambrose Monell, later truncated due to trademark law.

Monel appeared, rather advantageously, during a frenzied demand for nickel products. As wars of expansion raged, militaries witnessed the technological advantages of a base metal that annihilated the Philippine fleet with only a single American casualty. Armament purchases exploded as conflicts and complicated imperial ententes culminated in the The Great War.

The aftermath of World War I had profound effects on nickel product demand. Used extensively for vessels and munitions prior to the war, demand vanished in the aftermath of the disarmament treaties of 1918. Monel’s success was now firmly tied to its visionary parent, Stanley.
Now First Vice-President of the International Nickel Company, he ignored calls to shutter production and went all in at the height of the crisis. Seeing the need to diversify from mining, he lobbied for a refining plant and research division, while bulking out marketing in New York City.

By the 1920s, Monel was used in 23 different industries, with uses ranging from naval battleship parts to specialized ice-cream cabinetry. Advertising touted Monel as a white metal that was corrosion proof, stronger than steel and of silvery appearance, brighter than nickel. This wonder metal alloy saw its decorative use explode during the heady expansion of the art-deco age, while acid and seawater resistance and low coefficiency of expansion, among other properties, saw utilitarian use for industry methodically rise even through the Great Depression.

Yet, Monel had a flaw. Unlike the plethora of alloys that followed, Monel was not created for purpose and had exposed itself to an orgy of applications. Still in the early stage of research, its base metal, nickel, was a relatively newcomer to the elemental stage, with production not taking off until the 1880s.

When the scientific community did study it, they found that high nickel products did not stay “silvery” in outdoor environments for long, with reports of “fogging” that required constant attention in humid environments.[2]

By the 1930s INCO was facing heavy competition from the Aluminum Company of America (Alcoa) and stainless steel vendors. As nickel prices rose, companies flaunted cheaper products with fractional nickel content and none of the exterior aesthetic issues. New-fangled skyscrapers such as the Empire State Building and the Chrysler Building shunned Monel for more economical and proven alloys, reducing Monel to decorative interior uses and utilitarian marine and chemical applications.

In conservation, this white metal is routinely mistaken and often mistreated. In an exterior shaded environment, it is regularly identified as bronze or brass due to its green weathering, while in an interior location, stainless steel, nickel silver and aluminum. Monel can in fact turn black, gray, brown, yellow and green, and is subsequently painted, waxed and lacquered. Lost elements are replaced and welded together with patinated stainless steel. Yet is this the correct treatment? Evidence points to the fact that Monel was never expected to turn these colors, yet architects and conservators are leaving potentially active corrosion cells in the name of “patina”, while assuming no work is required to maintain this “indestructible alloy.”

Through systematic research I intend to educate both the professional and local community on Monel. My findings to-date have demonstrated not only that the intended color scheme never wandered from pewter or silver, but that green weathering consists of both nickel and copper-based compounds.[3] Adjectives used to describe the oxidation of Monel are a far cry from the superlatives used to describe it in the advertising catalogues of the early twentieth century.

As Derek Trelstad pointed out in Twentieth Century Building Materials, Inco failed to “discuss methods for removing stubborn soiling or preserving existing patinas” and “no known treatments specifically address deterioration.”[4] Working at Kreilick Conservation, LLC, we intend to address this by empirical testing of cleaning Monel in the field, while I will continue my own laboratory-based research to uncover the phases and causes for Monel atmospheric corrosion. It is hoped that this work will encourage greater care and improved treatment of this significant North American nickel-based alloy.

*Monel is a registered trade name of Special Metals Corporation.  The alloy referenced is produced today by several companies worldwide as UNS N04400. 

[1] Today Monel is no longer smelted and refined directly from the ore itself, but created with tightly-controlled computerized tolerances in an air induction furnace.

[2] W. H. J. Vernon, "The "Fogging" of Nickel," Journal of the Institute of Metals 48 (1932).

[3] Many conservation texts have concluded that the green weathering of Monel is due solely to the copper content of the alloy. See “Monel” in the ‘The Aging of the Surface’ L. William Zahner, Architectural Metal Surfaces (Hoboken, NJ: John Wiley & Sons, 2005), 304.

[4] Derek Trelstad, "Monel," in Twentieth-century building materials : history and conservation, ed. Thomas C. Jester (New York, NY: McGraw-Hill, 1995), 24.

A summary of James’ research is available in the Technical library of the Nickel Institute.

 The views and opinions expressed in this blog are those of the author and do not necessarily reflect those of the Nickel Institute.

BIBLIOGRAPHY

Trelstad, Derek. "Monel." In Twentieth-century building materials : history and conservation, edited by Thomas C. Jester. New York, NY: McGraw-Hill, 1995.

Vernon, W. H. J. "The "Fogging" of Nickel." Journal of the Institute of Metals 48 (1932): 16.

Zahner, L. William. Architectural Metal Surfaces. Hoboken, NJ: John Wiley & Sons, 2005.