US2878172A - Production of silver-plated stainless steel ware - Google Patents

Description

United States Patent PRODUCTION OF SILVER-PLATED STAINLESS STEEL WARE Angelo C. Scavullo, Jamaica, N. Y., assignor to Victor K. Scavullo, Charles Scavullo, Frank Scavullo, Marie Scavullo Saegert, and Margaret Scavullo Scott No Drawing. Application August 16, 1956 Serial No. 604,313

1 Claim. (Cl. 204-40) My invention relates generally to metal hollow-ware and fiat-ware, and more particularly silver-plated stainless steel ware and a method of producing the same.

Among the objects of my invention is to provide stainless steel articles, particularly those either for the table or for decoration about house, apartment, hotel or office, with an enduring surface of silver on at least a selected area thereon; and to provide a method for producing such ware, which method is at once simple, direct and certain in result, enabling the use of base stock which is free of corrosion attack by foodstuffs or the atmosphere, although incorporating only a minimum of metals either strategic in nature or in short supply, of which nickel is typical; and which method lends itself to the production in simple and direct manner of a variety of different and pleasing finished surfaces, which surfaces, in subsequent use, are advantageously characterized by substantial absence of detrimental corrosion and minimum tendency towards surface conversion into toxic compounds.

All the foregoing as well as many other objects and advantages attend the practice of my invention, some of which will be obvious and some of which will be more fully pointed out hereinafter during the course of the following disclosure.

Accordingly, my invention may be considered as residing in the combination of elements and arrangement of parts; and in the several procedural and manipulative steps and the relation of each of the same with one or more of the others, the scope of the application of all of which is more fully set forth in the claims at the end of this disclosure.

To permit a more ready understanding of my invention, it may be noted at this point that over a period of years much attention has been given in the art to the problem of plating base metals with silver or other precious metals, this in order to produce at minimum expense satisfactory fiat and hollow ware articles intended primarily for either table or ornamental use. Successful results attended the efforts to plate silver onto the so-called German silver, i. e., the well-known nickel-silver base. But articles produced therefrom were not entirely satisfactory because the base metal was soft. And oxidation set in following the wear of the silver-plate at the points or regions of greatest wear.

Moreover, important quantities of the highly strategic element nickel were required in the nickel-silver base metal. As is well known, the metal nickel with ever increasing frequency, encounters periods of short supply. From time to time in the recent past, use in civilian fields has been severely restricted by the government. Illustratively, in World War 11, Federal authorities prohibited the use of 18% nickel-silver inthe production of silverplated hollow-ware. Again, during the Korean situation, the civilian use of nickel in stainless steels was severely curtailed.

On the other hand, experience demonstrates that silverplated products having a mild steel base prove generally Satisfactory. Apparently, however, the bond between the See silver and the base metal is not strong. Moreover, the

silver plate wears rapidly and the product becomes highly susceptible to attack by conventional silver polishes. Actually, the mild steel does not retain its silvered surface nearly so long as does the nickel-silver base. It quickly shows rust. And this rust creates serious hazard due to the mechanical irregularity of the rusted surface and to its chemical interaction with materials to which the plated article is commonly subjected, particularly in combination with those silver polishes which are currently in use and which include substantial amounts of oxalic acid and cyanide.

Accordingly, an object of my invention is to provide a simple, direct and certain method of producing stainless steel hollow-ware and the like with long-wearing silver outer surface, especially the production of silver-plated stainless steel ware making use of grades of stainless steel in which the nickel content is low.

In the practice of my invention in making silver-plated stainless steel hollow-ware, and in the application of silver-plating to stainless steel base metal, I employ four important steps, each of which is essential to successful end result. As well, the sequence of such steps assumes critical importance. These four steps are as follows: First, a nickel strike is applied to finished and cleaned stainless steel ware. Second, a copper strike is next applied thereto. Third, a silver strike is applied. And finally, a substantial silver plate is laid down on the treated and conditioned metal ware. Preliminary caustic and acid treatments are employed, together with intermediate rinsing in water.

In producing hollow or fiat ware, either functional or ornamental in nature, or both, I first completely fabricate and finish the article of the base metal. And any desired ornamentation is applied before I undertake the plating process which I am about to describe. As base metal I employ a selected grade of stainless steel embodying a minimum quantity of the strategically important metal nickel. Only so much nickel is embodied as is necessary to impart the required stainless and corrosion-resistant qualities. Typically, I may use an 18-8 chromium-nickel stainless steel. But where necessity dictates, I have successfully employed stainless steel containing the ingredient nickel in a proportion as low as 2%. This I find to be a critical minimum figure.

For the proper practice of my invention, it is essential that the base metal article, prior to plating, be rendered as clean as possible as to surface detail. To this end I find it advantageous to scour the article in. hot potash solution. After the potash, or other suitable alkali treatment, has been employed, I completely remove this alkali through an elfective water rinse. Next I dip the article in a dilute acid solution, preferably a 5% solution of hydrochloric acid. This is followed by water rinse. It will be noticed that I have now cleansed the article thoroughly, preliminary to the actual plating steps, through the use of, first an alkali treatment, followed by an acid treatment. The product is now ready for plating action.

I first lay down a thin and closely adherent nickel surface on the base metal. Apparently the nickel of the strike solution is thoroughly compatible with the nickel content of the base metal.

and cleaned stainless steel article to a nickel strike which typically is for a period of about one minute-at a current density of around 60 to amperes per square foot of article surface. The article is then withdrawn from the nickel bath and subjected to thorough water rinse. This removes all traces of the nickel bath and leaves the article with clean, thin film of nickel adherent thereto.

I next subject the article, with thin nickel film thereon,

And it can be laid down with comparative readiness. To this end I subject the formed 3. to :a' copper strike in a copper cyanide solution. Typically, treatment in this bath endures for approximately 30 secends. I find that this time is sufficient to provide the requisite thin film of copper. The current density employed is of approximately 30 amperes per square foot of surface area. Residual copper bath solution is removed through thorough water rinse.

Next, with thin film of copper tenaciously adherent to the underlying thin film of nickel, the product is ready for an initial application of silver. This I achieve in a silver strike, the purpose of which is to lay down a thin layer of silver on the product. To this end I subject the coated product for approximately 30 to 60 seconds to treatment in silver cyanide solution. In each case, the precise duration of the treatment depends upon the size of the article, the greater the size of the article, the longer time the duration of the strike. I conduct the silver strike at a current density of approximately 30 amperes per square foot. A thorough water rinse follows. And to make sure that final plating is successfully and uniformly distributed, I now brush the article clean, preferably using for that purpose a soft brass wire brush. I use a water rinse to remove surplus material.

Finally, I subject the prepared article to a plating operation .in which a substantial layer of silver is laid down over the silver strike. In this operation I subject the article to a silver cyanide solution for a period of approximately half an hour at sharply reduced and moderate current density. Typically the current density ranges from about 8 to 10 amperes per square foot of the surface area of the article. I find that in a typical situation this yields a silver deposit ranging from about 0.0025 inch to about 0.0030 inch in thickness. A water rinse follows to remove surplus plating solution.

I polish the plated article with a soft brass brush, to achieve a desired surface. Waste material brushed out is rinsed away. And this step is followed by exposure to extremely hot water, to condition the article for air dry which follows immediately. Thereafter it is hand-cleaned with a towel.

As indicated above, I consider the initial nickel strike as a first truly essential step of my process; it is absolutely necessary in order to achieve desired results. And

' the sequence of strike and plating steps thereafter must be faithfully followed. Illustratively, I have found that where the nickel strike is omitted, and effort is thereupon made to apply the copper strike directly to the base metal, successful plating is not had. Such plating as is laid down wears poorly and does not cling tightly.

While in known earlier processes copper has been plated on steel, nickel onto the copper and finally silver onto the nickel, this has been in the treatment of mild steels.

Here the plating material wears rapidly and gives rise to serious exposure of the user to toxic aftermaths, as pointed out above. Plating of copper on nickel-containing base metal has not proven to be entirely satisfactory. And the art has heretofore considered it impractical to achieve a satisfactory silver plating of stainless steel. So far as I know, I am the first one to successfully silverplate a stainless'steel base. Certainly, this is so as concerns a four-step operation in which the base metal is first provided with a thin overlie of nickel (through a nickel strike), then with a thin overlie of copper (through a copper strike), next with a thin coating of silver (through a silver strike), followed by the provision of a thicker layer of nickel, through a prolonged silver-plating step.

My new process has important advantages of readily lending itself to a variety of highly practical modifications. Through the use of these modifications a variety of articles can be produced having attractive appearance and functio'nality.

Illustratively, the stainless steel base metal may be silverplated on one .side only, usually the exterior surface. Such a feature maybe carried over to a variety of items formed initially of stainless steel. These, illustratively, include a coffee service, vegetable dishes, sugar and creamers, and generally like hollow-ware articles. All of these combine the attractive soft bright exterior appearance of silver, while displaying all the desirable qualities, such as high resistance to corrosion and noncontamination of food, which are so advantageously peculiar to stainless steel, particularly as compared to silver.

In employing this valuable modification, that surface which is to be kept unplated so as to display the base metal, is masked with a coating of suitable wax or plastic, of which beeswax is typical. So conditioned initially, the article is then plated in accordance with the practice of my method as outlined hereinbefore. The completed article displays a substantial silver-plated exterior surface with the stainless steel interior surface, this being the surface which has been initially masked.

By the practice of my invention hollow-ware articles wtih silver-plated stainless steel exterior are successfully achieved, and this in reliable manner. The procedural step themselves are simple and require only minimum time. Certainly of result is assured, provided only that reasonable care is observed to maintain absolute cleanliness throughout the operational procedure. Effective adherence of a rapidly built-up coating is ensured, with nickel content sharply reduced from that required in the conventional 18% nickel-silver base metal. An 18-8 chromium-nickel stainless steel can be successfully employed. And I may employ a base of stainless steel with reduced nickel content, this as low as 2%, all with satis factory results attending the practice of my invention, as noted above.

My invention is admirably suited to the production of plated flatware and hollow-ware during periods of restrictcd use of critical materials, the products themselves displaying long useful wear with minimum loss of pleasing surface characteristics. All the foregoing, as well as many other highly practical advantages attend the practice of my invention.

It is apparent from the foregoing that once the broad aspects of my invention are disclosed, many modifications thereof will suggest themselves to those skilled in the art, and that as well, many other embodiments thereof will likewise come to mind. Since all these fall within the scope and province of my invention, I intend the foregoing disclosure to be considered as purely illustrative and not as a limitation.

I claim as my invention:

In the production of silver-plated stainless steel ware, the art which comprises fashioning the ware of chromiumnickel stainless steel having a nickel content of at least about 2%; then subjecting the ware in sequence to a nickel strike at a current density ranging from about 60 to amperes per square foot enduring for approximately one minute; then copper-striking the base article for a period of about 30 seconds in a copper cyanide solution at a current density of about 30 amperes per square foot; then silver-striking the article in a silver cyanide bath for about 30 to 60 seconds at a current density of approximately 30 amperes per square foot; then wire brushing the article; finally plating the article this treated for approximately one-half hour in a silver cy anide bath at a current density of about 8 to 10 amperes per square foot, until a silver deposit is achieved ranging in thickness from 0.0025 inch to about 0.0030 inch; and polishing the plated article.

Schiele Mar. 3, 1 903 Belous Aug. 4, 1925 (Other references onfollowing page) UNITED STATES PATENTS Schwartz Oct. 16, 1928 Davignon Dec. 17, 1935 Stareck Mar. 9, 1943 Schaefer Dec. 18, 1945 5 Martz Dec. 2, 1947 Holbrook June 19, 1951 6 Donley Dec. 16, 1952 Davis Nov. 13, 1956 Cross Nov. 20, 1956 FOREIGN PATENTS Great Britain Dec. 19, 1935 Great Britain Oct. 7, 1938