US2418932A - Method of making enamel coated articles - Google Patents

Description

April 15, 1947. R. E. HARR 2,418,932

METHOD OF MAKING ENAMEL COATED ARTICLES Filed Nov. 13. 1940 wvmrm 7 RLIHARR a); Arro'k/vir Patented Apr. l5, 1947 UNITED STATES PATENT OFFICE METHOD OF MAKING ENAMEL COATED ARTICLES Russel E. Harr, Chicago, Ill., assignor to Western- Electric Company. Incorporated,

New York,

Y., a corporation of New York Application November 13, 1940, Serial No. 365,453 4 Claims. (Cl. 204-38) This invention relates to methods of making enamel coated articles.

' An object of the invention is the provision of. improved methods for the production of articles having a metal base and a smooth, highly ornamental and serviceable coating of vitreous enamel on the base.

' The present invention is particularly adapted to the product on of articles such as the number plates incorporated in telephone dials, which comprise a ase and a coating of vitreous enamel sued in articles of this type. The enamel on numberplates must be highly adherent to withlarly important that the enamel have a smooth, even and unbroken surface. Number plates are often exposed to dirt-laden atmospheres in service and under these conditions even minute imperfections in the enamel surface tend to acculint and the like, which mars from their utility. Because of these requirements and limitations, it has been customary to employ intermediate an improved 'process for forming this nickel-iron alloy.

In accordance with one embodiment of the invention, a base of desired shape is first formed of sheet iron and then copper plated, after which a layer of nickel-iron alloy is electrodeposited on the copper. The alloy layer is produced in an is applied base is then fired at fuse the enamel into on-the alloy layer and the asuitable temperature to a coating, v

A more complete understanding of the invention may be had by reference to the following de- .Or grit, around 90.1n'esh tailed description, taken accompanying drawing,

Fig. 1 is a plan view of ing the invention, and Fig. 2 is an enlarged sectional view of the number plate taken on the line 2-2 of Fig. 1.

' Inthe first operation for producing a complete in which copper can be applied conveniently in a conventional copper cyanide electroplating -process and a coating weight around 20 milligrams per square inch'is generally satisfactory. I

In the next operation, a nickel-iron alloy I2 is electrodeposited over the copper in a uniform layer. The iron content ofthe alloy should be between 50% and 10.0% with the balance nickel and the best results are secured with an alloy having an iron content around 1.5%.

To apply an alloy containing 1.5% iron and the balance nickel, an aqueous bath of the following composition is first prepared:

' Ounces per gal. of solution Nickel sulphate 24.0 Sodium chloride ;1 3.0 Boric acid 4,0 I Ferrous sulphate .0666 The solution is placed in the tank of a conven.-.

a cloth bag, and then 'suspen'ding the container in the solution. a Several ba s of iron particles may be suspended in the solution, the distribution "ofthe bags depending upon the size andarrangein conjunction with the a number plate embody ment of the tank. The presence of oxidized iron (ferric oxide) in the plating solution produces an alloy which causes enameling defects when enamel is later applied thereto. The addition of metallic iron to the bath reduces the ferric oxide to ferrous oxide which is not detrimental to the production of. a satisfactory nickelriron. alloy. The copper plated bases are thensuspended. the solution and current applied until an alloy coating of desired weight is electrodeposited on: the copper. The process is operated ata temperature between 135 F. and 145*F': and a'current density between 40 and 60 amperes per square foot of cathode sur-face-.. The means. of; these values are used preferably.

The above temperature and current densityranges are critical and their interrelation is im.- portant. A variation in current density; for example, will affect the proportions of irorr inthe deposited alloy for a given solution and temperature, as wellas. the properties oi the. alloy,. and for best results the above combination of solution concentrations,. operating; temperatures. and current densities should be maintained. The. described solution will produce an alloycontaining about 1.5% iron. If an alloy having a lower or higher iron content is desired. the bath is. correspondingly adjusted. by the use of. less-r more ferrous sulfate. or anodesr After. the copper. and. the: alloy coatingshave been: deposited on-the: base, the base. is ready.- to. receive the enamel, which is' applied only on. the face of the ring, or the portion exposed. in service, in order to'minimize the. cost, of. the. article and also to" facilitate: the maintenance: of over-all dimensional tolerances. A coating of white enamel. l3, such. as a lead hero-silicate enamel opacified with arsenic oxide, is: applied first- The. enamel isdistributed on. the alloy surface either. in the form: or dry powder or by a wet process intwhichlthe enamel particles are mixed with. water and a' flotation agent; such as-clay.. Thebase. is their firedsat. a temperature around 1-600 F. for" about three. and; one-half minutes to fuse the: enamel.. I

Identifying characters in contrasting-colors: are usually required to complete the. plate. The application of these charactersusuall-y involves repeated refiring of the initial enamel coating and this practice tendsto aggravate.

or other imperfections present in the initial coatine.

Orretype of plate, shown in the drawing has a background l4, letters and numerals it. These characters are produced with an inky suspension of:colored metallic oxides or frits in. avehicle-such as linseed oil and are applied on the surface of the white enamel by a: pri ting operation. The background,, which may be blue or black, is applied first and the plate is then baked at about '1'300F. to harden the ink' so that it will not be marred in subsequent printing. operations; The letters; which are" usually black; are then applied and the. plate is then again baked at a temperature of about 1300 F. The numerals are usually colored red and are applied the. same manner, after which the. entire plate is again fired to. fully. mature the ceramic ink whichv requires exposure. to. a temperature around.1300' F. for approximately 415' minutes.

Theresultant enamelcoatingis highly adherent and. has a smooth and. continuous surface- In .enameling; number plates the peripheral edge portions. of the enamel surface are critical and plates produced; by prior methnds have tended any roughness to develop a defect commonly known as "edge pimpling in these areas. These pimples may be very small and difilcult to detect, but after a period of service, they accumulate dirt and other foreign material to form smudges which are very dificult to remove, particularly because the number plates are-not. readily accessible for cleaning after they are. assembled. in a dial.

The nickel-iron alloy layer produced as herein: described causes the enamel to fuse into a smooth coating without the formation of pimples anywhere on the coating surface. The initial coat, of white enamel, is glassy and free of pimples. and these desirable surface conditions a are; preserved. during any refiring operations employedi the application of characters on the enamel. Theaction of the metallic iron on depositi'on of the alloy under the prescribed operating conditions contributes largely to the desired alloy properties and, as stated, this metallic iron is. preferably provided in the form. of. smalL particles.

For. most applications,. a. coating weight of 20 milligrams persquare inchfor both the copper. and the alloy. is satisfactory, although. itmay be desirable to vary these. values somewhat for. different enamel compositions, and,. in general, the copper. and. alloy layers. shouldbe of. about equal weight.

Although the. invention has been. described. in connection with. the manufacture. of number plates. for. telephone. dials,. itwill' be. apparent. that is equally applicable. to other ornamented. enameled articles anda it isto. beunderstood that the. invention is limited only. by the. scope. of. the appended claims.

What. is..claime.d is:

1.. A. method of. coating an article with a vitrifia-ble material which comprises electrodepositing. a. layer oi nickel-iron alloy containing from. .5I%- to 1. 0% of iron on..the article in a nickel sulfate, ferrous. sulfate solution, employing anickel anode. andan. ironanode, maintaining a quantity of metallic iron in. a subdivided-state. in the. solution. applying a. vitri-fiable material on the alloy layer, and. heating. the article to fuse the. vitrifiable; material tov form a smoothcoating.

2.4 A method of coating an article with. a vitrifiable material which comprises electrodepositing a layer of nickel-iron alloy containing from .5-%, to 10 of ironon the. article in a nickel sulfate, ferrous sulfate solution, employing a nickel anode. and an iron anode, placing a quantity ofmetallic. iron in. addition to the iron anode in the solution, applying a vitrifiablemateria-l on the alloy layer, and heating, thev article to fuse the vitrifiable material to form a smooth coating.

3-..A method of coating an article with a vitrifiable material which comprises applying a layer of copper onthe article, electrodepositing a layer of nickel-iron alloy containing from .5-% to 10% of iron on the: article ina nickel sulfate, ferrous sulfate solution, employing a. nickel anode and an iron. anode, placing particles of metallic iron in. the solution during the. electrodeposition, applying a, currentdensity of between 40 and. 60 amperes per square foot to. the surface being coated at a. temperature of. F. to. 1.45. E, covering the. surface of the electrodeposited alloy with a vitrifiable material, and heating thearticle to fuse the vitrifiable material to form. a. smooth coating.

4. A method of coating a ferrous base article with a vitrifiable material which comprises applying a layer of copper to. the. ferroua base,

RUSSEL E. HARR.

REFERENCES CITED The following references are of record in the file of this patent:

Number J I v l 'I I UNITED STATES PATENTS Name Date Ketcham Sept. 2, 1902 Eimen Jan. 6, 1925 Burns et a1 Dec. 22, 1931 Scott Nov. 12, 1935 Fink Nov. 1, 1932 Cowper-Coles Feb. 9, 1915 Crowder Sept. 27, 1938 Ramage Oct. 31, 1911 OTHER REFERENCES Cir. Bureau of Standards, No. 100 (1924), p. 9,

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