US2449422A - Electrodeposition of nickel - Google Patents

Description

SeptI 145 1948.

L. N. SMITH ELECTRODEPOSITION OF NICKEL Filed April 15V; 1944 Patented Sept. 14, 1948 ELECTRODEPOSITION F NICKEL Leslie N. Smith, Cleveland Heights, Ohio, assignor to The Harshaw Chemical Company, Elyria, Ohio, a corporation of Ohio Application April 15, 1944, serialfNo. 531,163

' 2 claims. (ci. 20o-49) 1 This invention relates' to electrodeposition of nickel and is also applicable to electrodeposltion of cobalt. More specifically, the invention relates to an improved process for electrodepositing nickel or cobalt by the use of insoluble anodes, es-

pecially in electroplating on sheet steel in long strips.

One object of theL invention is to secure the advantages which are inherent in the use of insolu- Y ble anodes while avoiding to a large extent the disadvantages which' have attended such met-hods heretofore. More specifically,v it is an object of the invention to provide a process whereby the concentration of the electrolyte with respect to nickel or cobalt can be maintained and a very high current density employed, utilizing a high chloride electrolyte and without excessive loss of chlorine. A further object is to provide for Superior eiiectiveness in the solution of the metal whereby it becomes practical to use highly pure metal, such as electro-sheet nickel or other electrolyticallyl deposited forms of nickel or cobalt, or mixtures thereof.

Still further objects'of the invention will be in part apparent and in part pointed out hereinafter in connection with the accompanying drawings,

` wherein Fig. 1 is a diagrammatic elevation of an electroplating tank and dissolving tank and showing schematically the connections between them for circulating liquids and vapors, and Fig. 2 is a transverse section taken through the 'plating tank of Fig. l, centrally thereof,

Referring now to the drawings, the reference character A indicates generally a plating tank, While the reference character B indicates generally a dissolving tank. The plating tank consists of a. receptacle indicated generally by the numeral I0 through which may be led a continuous strip Il of steel or other metal to be plated. This strip of steel may be guided through the tank by means of` roller guides I2 or in any other suitable fashion. Adjacent to the horizontal reach of the steel strip II is an insoluble electrode I3 which may be composed of any conductive material which is not attacked by the solution, such for example as platinum-clad steel. The insoluble'anode I3 will be suitably spaced from the strip to be plated and current will` be passed between the anode and the strip by connecting a. suitable source of current, one terminal to the insoluble anode and the other terminal to the roller guides I2. Adjacent to the side walls of the tank above the level of the plating solution are downwardly opening, channel shaped gas collectors I4 provided with outlet pipes i5 connected Y with nickel chloride or cobalt chloride, or a mix-` to a pump I6, which is adapted to place a suction on the gas collectors to draw in gases bubbling up through the solution along the sides of the tank and eject them through the pipe I1 into the bottom of the dissolving tank B through a suitable distributing outlet I8, which in its simplest form may be merely a continuation of the pipe I1 curved into a spiral in the bottom of the dissolving tank B and provided with small outlet openings in the top thereof.

Connected to the bottom of the plating tank A is a pipe I9 which leads to al pump 20. The pump 2Il withdraws solution from the plating tank A and delivers the same through the pipe 2l to the spray head 22, which can be of construction similar to the outlet I8 just described. The solution is allowed to return from the dissolving tank B through a pipe 23. The dissolving tank B may be vented througha vent pipe 24 in order to dispose of any chlorine and other gases not absorbed. The dissolving tank B may be filled with pieces of nickel or cobalt indicated at 25, only the upper and lower portions ofthe metal pack in the dissolving tank being indicated. Such metal may rest on a suitable perforated plate or screen to prevent the interference of distribution of gas bubbles bythe pieces of nickel or cobalt.

In operation, the dissolving tank is charged ture of the chlorides of nickel and cobalt, or if desired, with a mixture of the sulfates and chlorides of nickel or cobaltor both, the chlorides however accountingior at least one-third of the nickel present. I preferably use chlorides only. The current is connected as above indicated and the strip II is caused to pass through the solution at a speed such as to apply the desired thickness of metal. In this process, chlorine will be evolved and will pass from beneath the insoluble anode I3 upwardly along the sides of the tank. This chlorine will keep the solution oxidized and prevent pitting. Plating under the conditions indicated Valso produces a degree of brightness of deposit beyond that of the normal Watts or gray nickel which are kept wet with solution through the I spray head 22. The chlorine thus has an opportunity to -be absorbed in the solution and react with the metal whereby metal chloride is formed and goesv into solutionA thus enriching the solu#k 3 tion with respect tc metal. By circulating the solution at a suitable rate, the metal concentration can thus be maintained at the desired level. By the useof this process, I am able to dissolve electrolytic nickel and cobalt which are of such purity, for example, nickel electro-sheet, that they are not satisfactory for useas anodes in ordinary plating solutions.A It is, of course, possible and indeed quite easy to dissolve those forms of nickel and cobalt which are easily dissolved, such for example as the regular nickel anodes now in general use.

A suitable solution for the realization of the invention might be termed an all-chloride solution and be of the following composition:

A suitable mixed chloride-*sulfate bath may be composed as follows:

Nich-61120.--- 75-350 grams, suitably 150 grams NiSO4'6H2O 75-350 grams, suitably 150 grams Formic acid 0-15 grams, suitably 6 grams Boric aeld 25-50'g./l., suitably 37.5 g./l. H2O to make" 1000 cc. v pH 1-5, suitably 3 current density. 10o-zooo amps/sq. fn., suitably 1000amps./sq. ft. f Temperatura-.. 1Z0-200 F.

What I claim is:`

l. A plating process adapted foliutilization of diillcultly soluble masses of electrolytic nickel metal in electrodeposition of nickel comprising the steps of electrodepositing nickel from a body of'acid nickel electrolyte containing nickel chloride whereby chlorine is evolved and the nickel chloride concentration of said electrolyte tends to be reduced and adding nickel chloride to said electrolyte to counteract the tendency to reduced concentration thereof by passing chlorine so evolved and electrolyte from said body of electrolyte containing nickel chloride equivalent to from 75 to 350 grams per liter of NiClz-GI-lzO into simultaneous contact with masses of diili-v cultly soluble electrolytic nickel whereby to `dissolve nickel from such masses as nickel chloride and returning such electrolyte with its resulting increased nickel chloride content to said body of electrolyte.

2. A plating process adapted for utilization of diilicultly soluble masses of electrolytic nickel metal in electrodeposition of nickel comprising the steps of electrodepositing nickel from a body of acid nickel electrolyte containing nickel chloride by passing current through said electrolyte from an insoluble anode to a cathode whereby chlorine is evolved and the `nickel chloride concentration of said electrolyte tends to be reduced and adding nickel chloride to said electrolyte to counteract the tendency to reduced concentration thereof by passing chlorine so evolved'and electrolyte from said body of 'electrolyte containing nickel chloride equivalent to from 75 to 350 grams per liter of NiClz-6HaO- into simultaneous contact with masses of diillcultly soluble electrolytic nickel whereby to dissolve nickel from such masses as nickel chloride and returningU such' electrolyte with its resulting increased nickel chloride content to said body of electrolyte.`

LESLIE N. SMITH.'

REFERENCES CITED I The following references are of record inthe le of this patent:

UNITED STATES PATENTS Great Britain 1920 Number Name Date 714,861 Browne Dec. 2; 1902 1,137,874 McCaskell May 4,1915 1,065,090 Werth June 17, l1913 1,386,094 Dow Aug. 2, 1921 1,456,615 Belcher et al. May 29, 1923 1,516,122 Scarles Nov. 18, 1924. 1,608,706 Madsen Nov. 30, 1926 1,900,534 Wilkins Mar. 7, 1933 Y 2,128,548 White Aug. 30,1938 2,200,987 Hubbell et al. May 14, 1940 2,393,516 Burns Jan. 22, 1946 FOREIGN PATENTS Number Country Date 22,355 Great Britain 1896 154,471

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