US1953758A - Cast anode - Google Patents

Description

April 3, 1934- s. B. HoGABooM CAST ANODE Filed Dec. 29, 1931 VENT R ratented Apr. 3, 1934 PTENT OFFICE 1,953,158 cAs'r ANonE George B. Hogaboom, New Britain, Conn., assignor to Hanson-Van Winlxle-Munnimr Company. Matawan, N. J., a corporation of New Jersey Application December 29, 1931, semi No. s'3,s49

2 Claims.

This invention relates to soluble anodes for use in the electrodeposition of metals, and has for its particular object to provide a cast soluble anode of improved grain structure and homogenelOusness.

In the electrodeposition of metals, soluble anodes are commonly employed for the purpose of maintaining the metal concentration of the solution and for preventing the acid or alkali content of the solution from becoming too high for satisfactory work. Such use of soluble anodes involves considerable diflculty on account of the tendency of the anode to dissolve or corrode at a different rate from that at which the metal is deposited at the cathode, and the tendency to corrode unevenly. The nature of the grain structure and the uniformity of the metal in cast anodes are known to have considerable influence on the satisfactory operation of soluble anodes, but the provision of the proper grain structure and uniformity by economical methods has in many cases been difficult to accomplish in the case of castI anodes.

The invention is applicable to the production of anodes of various metals and alloys, among which I may mention as examples copper, nickel, brass and zinc. While the diiliculties mentioned are present to greater or less extent in all cast metal anodes, they are particularly severe in the case of cast nickel anodes. Cast nickel anodes, for example, have very little cohesion between the grains, and in the process of solidification, sulphides and oxides of nickel, and of certain metallic impurities such as manganese, magnesium, silicon and iron, are concentrated locally in or between the grain boundaries. A eutectic of nickel and nickel oxide is commonly found between the grains of nickel. These grain boundary materials are much more readily attacked than the pure metal grains during the electrolytic action, and especially when they are chemically soluble in the electrolyte. This objection is particularly marked in the case of acid electrolytes for copper and nickel. The corrosion of the grain f boundaries more rapidly than the crystals of pure metal tends constantly to release undissolved grains or fine particles of metal into the solution, which grains or fine particles of metal are either Wasted or they are carried over to the cathode and cause objectionable roughness on the cathode. This latter action is so detrimental that it is common practice to put a diaphragm between anode and cathode to act as a filter.

I have ascertained that cast anodes, substantially free from the objectionable features of ordlnary cast anodes, can be economically produced by solidifying the fused metal while it is under the action of centrifugal force, and particularly centrifugal force applied transversely of the major axis of thev anode or anode rod being formed.

In centrifugally cast metal anodes the intergrain boundary' elements or impurities do not exist as local concentrates, but are dispersed or distributed throughout the Whole mass. Any gases present may even be expelled from the mass by the centrifugal force. 'I'he result of the centrifugal action is thus to make a substantially homogeneous anode which may at the same time be given the desirable flne grain, dense structure that has the property of corroding uniformly at the proper rate, and the tendency of fine particles of undissolved metal to be set free in the electrolyte is substantially eliminated.

One example of the manufacture of cast anodes, in accordance with the present invention, is illustrated diagrammatically in the accompanying drawing, in which Figure 1 is a longitudinal vertical section through a conventional centrifugal casting apparatus, and

Figure 2 is a transverse section through the rotating chill or mold.

In said drawing, 10 and 11 indicate bearing standards in which is journalled the rotating member comprising the chill or mold 12, the end ring 13 at the feed end, and the end plate 14, from which projects the trunnion 15, at the opposite end of the mold. A suitable drive 16 is applied for example to the projecting end of trunnion 15. A pouring spout 17 is mounted on standard 18 at the open feed end of the mold and projects into the latter so that charges of molten metal can be introduced while the mold is being rotated to ll the molding spaces 19. These charges of molten metal are allowed to 9 solidify at the proper rate of cooling to provide -the desired fine grained structure.

The cast anodes may readily be removed by separating the members of the molding unit.

It will be particularly noted that centrifugal force is applied transversely of the major axis of each anode rod so that any difference in density of metal, due to difference in radius of the rotation, will be correspondingly minimized.

The molds or chills may obviously be of suflicient length to produce castings of single anode lengths, or they may be of such length that each casting can later be cut or severed to form a plurality of separate anodes.

Anodes constructed in the manner described have been foundin practice to be free from passivity, and to corrode uniformly and evenly without. the occurrence of fine particles of undissolved metal in the electrolyte.

I wish it to be distinctly understood that the apparatus and method illustrated in the accompanying drawing are set forth merely for the purpose of giving an example of how the anode may be centrifugally cast, and that the inven'

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