A Retrospective View of Nickel Plating
A review article originally printed as Plating & Surface Finishing, 71 (6), 64-70 (1984) on the occasion of the 75th anniversary of the founding of the American Electroplaters Society.
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by W. Wallace Sellers
A review article originally printed as Plating & Surface Finishing, 71 (6), 64-70 (1984) on the occasion of the 75th anniversary of the founding of the American Electroplaters Society.
The fascinating story of nickel plating is characterized by resourceful individuals and companies responding to industry needs.
A chronicler’s view is seldom completely objective. It is colored by his perspective. My 38 years in the nickel-plating industry causes me to view it differently than would one writing not from involvement but solely from facts garnered in a library or from interviews. His story might well be more objective than mine. And developments I see as most significant may not be those the reader would have chosen. This, therefore, is not a complete history of nickel plating over these past 75 years but only a citation of salient developments that, in my view, brought the industry from its infancy in the early 1900s to its maturity today. Fascinating things happened along the way.
Dr. Isaac Adams is credited by George Dubpernell with being the father of nickel plating in the U.S.1 From the days of Adams, who reputedly spent more time with plating baths than with medicine, to the comprehensive work of O.P. Watts, progress in the industry inched along. The main patent on Adams' bath and process, issued in 18692, served as a cornerstone on which subsequent researchers built. But it was not until Watts reported his work in 19153 that nickel plating really began to grow. An investigation by H.T. Kalmus and coworkers dealing with cobalt as well as nickel was summarized in the Transactions of the Electrochemical Society of 1915. This work led the authors to the opinion that nickel could not be plated under commercial conditions at current densities as high as those possible for cobalt4. Accepting the challenge, Watts did further work that led to his famous paper of 19165, in which he suggested the formula known the world over as the "Watts bath." This laid the foundation for modern nickel plating. Although the merits of Watts' formula were not immediately recognized, acceptance grew steadily. By 1924 it was used to plate automobile bumpers1,6. According to Watts' personal survey, 200,000 gallons were in use in 19311. The bath was on its way to becoming the basic electrolyte of the nickel-plating industry.
Watts' formula was an aqueous solution of nickel sulfate, nickel chloride and boric acid. Although these continue to be the basic ingredients of the majority of nickel-plating baths used in industry, the amounts and their ratios have varied significantly, so that a more precise name for such baths is "Watts-type." These baths yield soft, ductile deposits that are easily buffed to an appealing bright finish. If deposited over a bright surface to a thickness not exceeding 1 mil, the coatings usually exhibit a degree of brightness without buffing. But to achieve the luster demanded by a discriminating buyer, the object being coated must be polished and the coating must be buffed. Both are costly. With the development of automatic polishing and buffing, costs were reduced. But this was not enough. Hence, the simple Watts-type bath is used today for non-decorative, or functional, plating. Other electrolytes were developed for decorative coatings. Most of these used some modification of the Watts-type formula as the basic electrolyte.
Schloetter, who had established a plating supply house in his native Germany in 1912, was reported to have 73 patents by 1930 dealing chiefly with tin, iron, copper, lead and zinc plating10. Having successfully used aromatic sulfonates in some of the processes, he decided to try them in a nickel bath. The result was his U.S. patent of 193411 claiming use of unsubstituted aryl poly-sulfonates with two to three sulfonic groups. Schloetter's patent was preceded in 1931 by one granted to G. Lutz and L.R. Westbrook for use of other brighteners in this class12. The alkyl naphthalene sulfonic acids of Lutz and Westbrook, however, proved less useful than Schloetter's compounds.
Following the Schloetter patent, fruitful research netted a succession of processes. In 1936 and 1937, L. Weisberg and W.B. Stoddard were issued a patent in the U.S., Canada and the United Kingdom on an application filed in 193513. To cover their inventions, E.D. Vries and B.C. Case were issued a U.S. patent in 1938 and another in 193914,15. Also in 1938, W.J. Harshaw and K.E. Long were granted a patent suggesting diphenyl sulfonates16 and H.V. Waite was granted one covering the use of naphthalene disulfonic acids17.
The Weisberg-Stoddard bath contained cobalt and, under certain conditions, a small amount of ammonium ion. In a succession of technical papers, Weisberg promoted cobalt-nickel plating18,19,20. In 1936, a leading plating supply house, Hanson-Van Winkle-Munning, made bright cobalt-nickel plating a commercial reality and announced the process with at least two ads in the technical press21,22.
Competing supply houses quickly followed Hanson-Van Winkle-Munning: Harshaw Chemical Co. in 1935, 1936 and 19401; The Udylite Co. in 19381; Seymour Manufacturing Co. in 19381 and the McGean Chemical Co. in 1938 and 19391.
Tendency for deposits to pit was a common fault, but one that proved easy to correct through the use of anti-pitting compounds. An effective one was sodium lauryl sulfate, use of which was patented in 1941 by V.H. Waite and V.P. Martin, with assignment to McGean Chemical Co.23
Deposits from baths using Schloetter-type compounds were highly stressed and therefore easily cracked. There was also a problem with brightness. Although benzene disulfonate and naphthalene trisulfonate were dependable brighteners and could be used in substantial quantities without harmful effect, rate of brightening tended to decrease with thickness.
Fortunately, the advantages of bright nickel processes impelled researchers to spend money and effort to overcome the deficiencies. Their work uncovered other effective brighteners that were compatible with the Schloetter type and that could be added in small amounts to give decided improvements. But confusion followed their discovery. Some called the Schloetter type "secondary brighteners" and the newly discovered, more powerful compounds "primary brighteners." Others used a different nomenclature. Their importance, though, lay not in what they were called but in what they did. Together with suitable wetting agents to control pitting and other additives to reduce stress they made nickel plating an outstanding industrial development of the period.
Here we digress to note other developments without which decorative nickel plating may never have achieved its dominant position.
Several scientists are credited with the discovery of bright chromium plating. A German chemist, E. Liebreich, disclosed his invention in a series of patents issued in 1925, 1926 and 1927.1 Colin G. Fink and C.H. Eldrich invented a similar process about this same time24,25. Although significant changes and some improvements have been made, this early work was the foundation for commercial bright chromium plating, particularly in the U.S. Without bright chromium, much of the work that followed in the field of decorative nickel plating may have been only of academic interest. Or it may not have occurred at all.
But to debate this is to quibble unnecessarily. The key points are: (1) good semibright nickel coatings were an important bridge between the development of early bright nickels and the multilayer coatings to come later; (2) many skilled people in the automobile industry as well as in the plating supply houses contributed their talents and time to bring semibright nickels to the stage where they would be a dependable base for the multilayer coatings that were to follow.
Accuracy would be violated by an attempt to set the precise date for the commercial introduction of multilayer coatings. Although dates on patents may be an indication, they do not tell when the claims in the patents became a commercial reality. We, therefore, must approximate a time. As we shall discuss later, growth of the nickel-plating industry has been stunted by periods of imbalance between supply and demand. A severe imbalance spanned the years of 1950 through 1956. In the U.S. all civilian nickel-dependent industries had to eke out on less than was needed. Plating was no exception. Coating thickness was often reduced to little more than enough to cover the surface. Lacquers applied to help stave off the ravages of corrosion did not keep objects from quickly losing their bright, good looks. Automobile bumpers looked sad. Automobile owners looked sadder. Nickel-chromium coatings lost much of their respectability. When in 1958 it became clear that the crises had passed, developers of multilayer systems and The International Nickel Company, Inc. (Inco), the leading supplier of nickel anodes whose research between 1945 and 1955 had demonstrated the efficacy of multilayer coatings in enhancing corrosion protection of plated nickel, concurrently and independently set out to improve the reputation of decorative nickel-chromium. The processes, which had been shelved or used ineffectively during the imbalance, were zealously promoted. This was truly a turning point. For without multilayer coatings it is doubtful that nickel-chromium would have remained the only coating used on steel bumpers for so many years.