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A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 2 0 2 4 was mixed with charcoal and sent to open hearth reverberatory furnaces to cast pigs, before final purification and casting in an electric furnace to produce two-ton ingots [5] . Unlike steel, porosity, slag, folds, or cracks were removed by a cutting down process known as mill- ing, before being passed to the hammer department for chipping off defects. The blooms were then reheated and placed through the rolling mill for bil- lets required at the rod or sheet mill for production [5] . ADVANCEMENTS The Huntington refining process was continually honed. A Russian citi- zen, Otto Lellep, described a more ef- ficient conversion process for refining nickel or nickel-copper matte through steadily reducing conditions at very high temperature as early as 1917. It comes as no surprise that later meth- ods of 1923 and 1926 were assigned to the International Nickel Company. The company subsequently filed a new patent in 1928 that blew superheat- ed steam into the matte at much lower temperature, avoiding lining damage to the converter and removing Lellep from the equation. The use of the natural nickel-copper ore and matte continued until 1947, at which time the company shifted to a nickel sinter and copper in- got charge. Today the process uses an air induction method for production. DISCOLORATION Despite marketing to the contrary, Monel metal did not stay “silvery” and had notable discoloration issues that became apparent from the late 1920s. A report from the correspondence of the famed Philadelphia metalworker, Samuel Yellin, notes the wrought alloy turned white within one year of install- ment; a “fogging” problem with nick- el that was increasingly discussed by the foremost corrosion scientist W.H.J. Vernon [6] . While atmospheric corro- sion in terms of weight loss and pitting has been proven to be minimal, var- ied reports of greens, browns, blacks, and yellows demonstrate the unusual discoloration of Monel from the usual gray or pewter-like color anticipated by the fabricators [7-9] . This aesthetic issue likely harmed Monel’s ability to be con- sidered for anything but utilitarian pur- poses by the 1930s and was probably a key reason for its sole remaining use in roofing. ~AM&P Note: Part II of this series will test the corrosion products found on exterior, historic Monel today and the likely met- allurgical or atmospheric reasons be- hind their formation and discoloration of the base metal. For more information: James E. Chur- chill, Conservator, Kreilick Conser- vation, jchurchill@kreilickconservation. com or james.churchill@columbia.edu , haboneh.academia.edu/JamesChurchill. References 1. J.F. Thompson, and N. Beasley, For the Years to Come: A Story of International Nickel of Canada, New York, NY, Putnam, 1960. 2. D.H. Browne, The Composition of Nickeliferous Pyrrhotite, The Engi- neering and Mining Journal, Vol LVI, December 2, 1893. 3. United States Department of the Interior, and David T. Day, Chief of Division of Mining Statistics and Technology, Mineral Resources of the United States, Calendar Year 1888, ed- ited by Bureau of Mines, Washington, D.C., United States Government Publishing Office, 1890. 4. S.J. Rosenberg, Nickel and Its Alloys, National Bureau of Standards Monograph 106, edited by United States Department of Commerce, 156, Washington, D.C., United States Government Printing Office, May 1968. 5. The International Nickel Company’s Rolling Mills, The Metal Industry, Vol 20, No. 11, November 1922. 6. W.H.J. Vernon, The ‘Fogging’ of Nickel, Journal of the Institute of Metals, Vol 48, 16, 1932. 7. E.L. Hibner, Evaluation of Nickel- Alloy Panels from the 20-year ASTM G01.04 Atmospheric Test Program Completed in 1996, Outdoor Atmos- pheric Corrosion, ed. H. Townsend, ASTM International, p 277-283, 2002, DOI: 10.1520/STP10899S. 8. H. R. Copson, Atmospheric Cor- rosion Behavior of Some Nickel Alloys, Symposium on Atmospheric Corrosion of Non-Ferrous Metals, ASTM International, p 141-158, 1956, DOI: 10.1520/STP44091S. 9. D. van Rooyen and H. Copson, Atmospheric Corrosion Behavior of Some Nickel Alloys, Metal Corrosion in the Atmosphere, ed. W. Ailor and S. Coburn, ASTM International, p 175-186, 1968, DOI: 10.1520/STP34087S. Fig. 3 — Detail of Monel decoration on a door hinge on the Bryn Athyn Cathedral, Pa. Courtesy of James E. Churchill.