US1433618A - Metal anode for electrodeposition and process of producing same - Google Patents

Description

Patented Oct. 31, 1922.

UNITED STATES PATENT orrlcs;

GEORGE HOGABOOM, OF NEW BRITAIN, CONNECTICUT, ASSIGNOE TO SCOVILL MANU- FACTURING COMPANY, OF WATERBURY, CONNECTICUT, A CORPORATION OF CON- METAL ANODE FOR ELECTI CODEPOSITION AND PROCESS OF PRODUCING SAME.

We Drawing.

To all whom it may concem:

Be it known that I, GEORGE B. HOGABOOM, a citizen of the United States, residing at New Britain, county of Hartford, and State I of Connecticut, have invented certain new and useful Improvements in Metal Anodes for Electrodeposition and Processes of Producing same, fully described and represented in the following specification.

This invention relates to metal anodes for electrodeposition and to a process of producing the same.

In electrodeposition it is important to keep the metal content of the bath within definite limits, which may be accomplished either by changing the bath content or through the corrosion of the anode, or both. It is, however, more economical and generally preferable to maintain the metal content of the bath throughcorrosion of the anode, as far as this is possible.

Referring for convenience of description to nickel deposition as an example, it is the customary practice to add suitable salts to keep up the metal content of the bath even where corrosion is depended on to some extent to maintain the metal content. Metal in form of saltsis, however, usually more expensive than the nickel itself.

With some salts of nickel the acid content of the bath increases to such an extent that the deposit is inferior. Other salts decrease the'amount of metal that can be held insolution or tend to render the solution alkaline. As a result changes in the composition of thefbath complicate the operation and the deposition products are inferior and nonuniform.

Cast nickel anodes, such as are in general wise in electroplating, have a fair rate of corrosion but are objectionablefor other reasons. For example, cast nickel anodes are I impure, the impurities ordinarily consisting of carbon and non. They seldom run over 96% nickel and the most common commercial products are 90 -92% nlckel. The carbon present, under certain conditions, forms a coating on the anode which is insoluble and vals. the like, so that the iron goesinto solution,

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which also act to partially insulate the an- This coating, therefore,- must be scraped ofi at more or less frequent inter- Tf the solution contains a fluoride or Serial No. 447,799.

the iron deposits with the nickel, and the n1ckel lating is darkened in color, and its protective effectiveness is decreased. On the other hand, with the more customary solutlon's, the iron does not go into solution but is preclpitated and becomes a thick sludge which is the cause of considerable trouble and annoyance.

The use of rolled nickel anodes has also been attempted. These are obtainable with very. low total iron and carbon content, for example, 1%. It has been found, however, that then rate of corrosion is so low as to necessitate frequent additions of saltsto the bath, the objections to which have already been outlined.

In the case of anodes formed from electrolytic nickel it has been found almost impossibleto obtain any corrosion with the solutions ordinarily used. 7

While the above considerations apply particularly tonickel anodes, alike or analogous situation exists in the case of other metals of similar characteristics. Further with certain metals, for example, copper with cer tain .baths, the rate'of corrosion is too high. As a result the bath has to be diluted or its content changed in some other manner.

Further, in the electroplating art as commonly practised, the anodes are suspended from a supportby means of a hook or the ike. known, the anode cannot be completely submerged in the bath because the book, being made of a different metal so as not to corrode, contaminates the bath or causes other objectionable results. There is, therefore, a considerable portion of the anode proper that is not subjected to the action of the bath. As a result there is an undue amount of scrap loss. This loss is considerable in plalnts carrying on electroplating on a large sca e.

- It is one of the principal objects of the present invention to provide a metal anode for electrodeposition having an improved rate ofcorrosio'n. More specifically it is the object of the invention to provide a nickel anode of a high degree of purity and having such. a rate of corrosion as to reduce the additions to the bath to a minimum.

It is a further object of the present in- Vtlltion to reduce scrap loss to a minimum and to provide an anode that can be wholly submerged in the bath without objectionable results.

WVith these general objects in view the invention consists in the anode and process of producing the same, as herein described and more particularly pointed out 1n the appended claims.

In carrying out the invention as to the first aspect above outlined, process and product may vary widely as to detail. Considering, again, nickel anodes as an example, and in order to obtain an increased rate of corrosion, particularly Where nickel anodes of high purity are used, an anode blank is shaped either by casting or from wrought, e. g., rolled, or electrolytic stock. For reasons above stated, rolled anodes are preferable to cast anodes on account of their purity, and electrolytic anodes are less preferable for commercial reasons. The shaped anode blank is formed by any of the above methods and is then heated to a temperature sufiicient to cause a substantial change in its crystalline structure. .While the degree and duration of heat treatment may vary within considerable limits it has been found that heating for two hours at temperatures ranging from 750 to 1100 centigrade gives satisfactory results, though higher heating temperatures within proper limits give better results; A preheating of a half hour more or less may be advantageously given the blanks. After the heating the heated anode blanks are cooled, which may be done either by air cooling or quenching, the latter-giving the better results in both as to composition and freedom from scale.

Examination of the anodes after the treatment above described shows the crystals to be considerably enlarged and the structure coarsened, and tests disclose the fact that the larger the crystals the higher the rate of corrosion. The treatment described, therefore, makes it possible to utilize anodes of a high degree of purity without undue addition of salts to maintain the metal'content of the bath. The same result may be obtained by heat treating other metal anodes which corrode slowly.

In the case of certain metals, such as cop per, corroslon is ordinarily too rapid for commercial purposes with as acid baths; In this case, to improve the rate of corrosion, the rate is decreased. This may be. accompllshed, for example, by work mg the anode blank mechanically so as to vary the crystalline structure. This workmg has the opposite effect of the heat treatment, that is to say, the crystals appear to be made smaller and the structure less coarse. The result is a; decreased rate of corrosion in the kind of bath mentioned.

Referring to the other aspect of the invention, name y, that involvlng the suspencertain baths, such sion member, product and process may vary widely in this connection also. The result desired is an anode comprising anode proper and a suspending member of like metal, but in which the anode proper has a substantially higher rate of corrosion. In what is considered the best embodiment of the invention, both elements are formed of the same rolled metal, for example, nickel. The anode proper is then heated and cooled as above described to vary its crystalline structure and increase its rate of corrosion. The

anode proper and the suspension member are then joined together, which may advantageously be accomplished by welding, casting in, or any other method giving a firm lll'llOIl.

With the anode described the anode proper may be completely submerged in the bath and both contamination of the bath and undue scrap loss are avoided.

The-desired result may be attained in va 2. A metal anode for electrodeposition,

the corroding rate of which has been increased by producing a variation in the crystalline structure of the metal, from that presented by the metal in its cast, rolled or elec-- trolytic form.

3. A nickle anode for electrodeposition, the corroding rate of which has been increased by producing a variation in the crystalline structure of the metal, from that presented by the metal in its cast, rolled or elec v trolytic form.

4. A wrought nickle anode for electrodeposition, the corroding rate of which has been increased by producing a variation in the crystalline structure of the metal, from that presented by the metal in its cast, rolled or electrolytic form.

5. A wrought metal anode for electrodeposition having a higher rate of corrosion than a similar cast anode.

6. The herein described process of producing a metal anode for electrodeposition,

which consists in varying thecrystalline structure of the metal of which said anode is composed to improve the rate of corrosion.

7. The herein described process of produciiig a metal anode for electrodeposition,

hi h 9P $ts in heating the meta of hich,

said anode is composed to a temperature suflicient to cause a substantial change in the crystalline structure, and then cooling.

8. The herein described process of pro ducing a metal anode for electrodeposition. which consists in heating the metal of which said anode is composed to a temperature sufiicient to cause a substantial change in the crystalline structure. and then quenching the heated blank.

9. The herein described process of producing a metal anode tor electrodeposition, which consists in rolling the metal stock of which the anode is formed. heating the metal of said anode to a temperature sufficient to cause a substantial change in the crystalline structure. and then cooling.

10. A metal anode for electrodeposition. including a suspension member. in which both elements are of the same metal but in which the anode proper has a higher rate of corrosion than the suspension member.

11. A metal anode for electrodeposition. including a suspension member. in which anode proper and suspension member are of the same metal but of such different crystalline structure that the anode proper corrodes at a substantially faster rate than the suspension member.

12. A metal anode for electrodeposition, including a suspension member welded to the anode proper. both elements being of the same metal. but of such different crystalline structure that the anode proper corrodes at a substantially faster rate than the suspension member.

13. A metal anode for electrodeposition, including a wrought anode proper and a wrought suspension member of the same metal. in which the crystalline structure of the anode proper has been varied from that presented by the wrought form to increase its rate of corrosion.

14:. A nickel anode tor elect-rodeposition. including a suspension member also of nickel. the two elements having such different crystalline structure that the anode proper corrodes at a substantially faster rate than the suspension member.

15. A nickel anode for electrodepo'sition, including a wrought nickel anode proper and a wrought nickel suspension member. the crystalline structure of the anode proper having been varied from that of the wrought form to increase its rate of corrosion.

In testimony whereof, I have hereunto set