US1583891A - Process for the electrodeposition of metals - Google Patents

Description

May 11 1926.

, C. P. MADSEN PROCESS FOR THE ELECTRODEPOSITION OF METALS Original Filed Sept. 19 1918 Patented May 11,1926.

CHARLES P. MADSEN, NEW YORK, Y., I OF NEW YORK, Y., A CORPORATION OF NEW YORKQ 1,583,891 PATENT; OFFICE.-

ASSIGNOR To MADSENELL CORPORATION,

PROCESS FOR THE ELECTRODEPOSITION OF METALS.

Application filed September 19, 1918, Serial in. 254,793. Renewed October 8, 1925.

My present invention reates to processes for the electrodeposition of metals from aqueous solutions as protective coatings or upon cathodes from which they are subsequently to be removed as final or, intermediate articles of manufacture, especially as applied to metals such as nickel, iron, cobalt, etc.

Up to the present time very little. or no success has been achieved in the production of de osits of such metals of any considerable t iickness wherein the deposits are reguline, homogeneous, smooth and malleable. Thus, in the production of nickel deposit-s as hitherto practiced the deposits are not malleable and internal stresses are developed such that the deposit cracks orcurlsfronr its support on exceeding a thickness of 0.0'02-0003 inch. By extreme care in controlling the conditions of the bath, practicable only in laboratory Work, deposits as thick as 01004 inch have occasionally been made; even then, however, the results have not been dependable, and on exceeding this thickness the deposits invariably becomebrittle and badly pitted and are worthless.- Hencc galvanoplasty in nickel and other members of this group" of metals has hither- .to been impossible. A

All of thephenomen'a which cause these diflicult-ies arenot known, but it is generally accepted that they are due to the formation of hydrogen or of hydrates "of the metals being deposited, according to the conditions of the bath, and the absorption of said hy.

drogen or hydrate by the metal deposited.

The effects of the presence of these absorb-ed compounds in deposits of nickel, iron cobalt-and their mixtures and alfoys are very similar, butas they are more definite and more familiar. in the case ofcnickel deposits,

that metal has been selected herein as typical of the group.

' In operating baths forthe deposition of from the bath. Onrennmersingthe cathode 100 nickel hydrogen is liberated when the bath is acid andapp-arently to a slight extent even when it 'is neutral. On the other hand, when the bath is alkaline the formation 'of hydrate occurs, and, as the hydrates of nickel and the other members of this group are insoluble, the metal tends to precipitate" from the solution and the bath to become. inoperative- To avoid this result it is customary in commercial practice to run the 'baths slightly acid.

' in causing Under conditions of commercial operation hydrogen is always present, and forms minute bubbles which adhere with "ery greattenacity to the cathode. A great many devices have been developed in the operation of baths to remove this hydrogen and to thereby avoid the injurious results which appear-to be due to its absorption; for example, heating the cathode, brushing or rolling the cathode, shaking or striking the cathode, adding organic or other materials to the bath, adding solid foreign matter, agitating the bath, etc. These various treatments do not succeed entirely, as with their use the thickness of the deposit ma not be appreciably increased above the t ckness mentioned, if not actually decreased. Thedevices employed frequently result in embedding dirtparticles in the deposit and thus making it unfit for use, or frequently even greater absorption of hydrogen. Y

My inveutionhas for'its object to render possibTe the production of deposits of greater thickness than hitherto, to effect the production of deposits that, are malleable regardless-of their thickness, to render the I formation of deposits to a considerable extent independent of the conditions of op-' eration. and the amount of impurities andforeign matter in the bath, and such other objects as will hereinafter more fully appear 4 I have drogen bubbles which forms upon and adheres so tenaciously' to the cathode during the formation :of the deposit thereon may be destroyed almost instantaneously by comp cm removal ofthe cathode from the bath and exposure thereof to the air. The bubbles of hydrogen, both large and small, seem to burst or disappear almost imme diately on removal and thehydroge-ncontained therein thus completely removed discovered that the film'of hym inethe bath any remaining hydrogen film and adhering partic'es of impurities, such as nickel oxide, in the case of nlc'kel deposition, or other solid impurities, are washed fromthe cathode by theaction of the-sun ed as to beavoided, as'such steps ordinarily l l o cause the deposit forming after reimmersion to have the character of a separate deposit, and to separate or peel away from the deposit below it. I have discovered, however, that if the period of removal from the bath be sufficiently short the subsequently formed deposit forms a homogeneous and integral part of that formed prior to removal, and the entire deposit is unitary and inseparable.

I have found that by repeated removal and reimmersion of the cathode from thebath during the deposition process the deposit produced is homogeneous and malleable and may be carried to great thickness, and the bath may be operated under conditions of acidity'or alkalinity or impurity which would make deposition otherwise practically 'ofa ample here given, may be of an oxidizing character. This intermittent exposure of the surfaces of the successive deposits to the gaseous medium as by the interposition aseous layer between the surface of each eposit and the liquid of thebath, in the example here given, results in substantially. complete dissipation and elimination of hydrogen from the successive layers of the deposited metal, with the consequent production of an electrodepo-sited metal, such as nickel, in a malleable form.

I have found that the length of the period of removal of the cathode from the bath must be within fairly definite limits in order that the deposit formed after reimmersion may be integral with that formed prior to re moval. This critical limit varies with'the character of the bath, the temperature of the bath, the difference between the temperature of the bath and the temperature of the air,

etc. and may readily be determined by experiment. .Thus, in a nickel depositing bath operating 130 F., I have found that the cathode may be removed fromthe bath forten seconds without destroying the integral character-of the entire deposit, while a removal of fifteen seconds may cause the metal subsequently deposited to'form as a distinct, separable layer. With the bath hereinafter specifically described I have found from two to six seconds to be the proper limits of the 4 period of removal when operating at a temperature of 130- F. In any case I find it advisable that the period of removal from .the bath be at ieTast two seconds.-

\The frequency of removal is also of immeans.

out. my process.

portance in connection with the application of my process. I have found that the frequency of removal also depends upon certain factors of the deposition process, particularly the acidity of the bath and the current density; that is, upon those factors which affect the rate of formation of hydrogen in the bath. Thus, the greater theacidity the greater the frequency of removal necessary.- In a suitable nickel bath, such as that hereinafter described, with a current density of 200 amperes per square foot, if the bath is very acid, a removal every half minute is necessary; if the bath is only slightly acid, as is the standard practice, a removal every minute or every two minutes is sufficient, and if the bath is perfectly neutral, or even slightly alkaline, removal every five or even ten minutes is sufficient.

In removing the cathode from the bath the current may or may not be shut off during or before removahas desired. In the case of small cathodes in particular it is unnecessary to cut the current off by auxiliary means. hen the cathode is very long in the direction of its movement it may be advisable to cut off the current before removing it to avoid the formation of a deposit thicker at the bottom than at the top. For this purpose any form of circuit breaker may be used, the circuit being open for not more. r

than fifteen seconds and the removal and return of the cathode taking place during this period. When the current is not broken by auxiliary means it may be found desirable to partially rotate the cathode at intervals, preferably while removed from the bath, thereby bringing new points of the cathode to the lowermost position in the bath.

The rate of removal and reimmerson of the cathode may be relatively rapid or slow; I find it desirable, however, to effect them at a relatively rapid rate, thereby diminishing the tendency toward lack of uniformity of the thickness.

It is obvious that the removal and reimmersion of the cathode in the bath may be effected by a great variety of mechanical For example, it may be vertically reciprocated into and out of the bath, or it may be mounted on a rotating wheel or arm or moving belt within the bath, a small part of the path of which is outside of the bath. I have illustrated in the accompanying drawing, inpart diagrammatically, forms of apparatus such as may be utilized to carry In the drawing Figs. 1 and 2 aresections at right angles. through a bath in which the cathode is reciprocated vertically into and out of the bath, Fig. 2 being on line 2-2 of Fig. 1. -Figs..3 and 4 are sections at right angles through a bath in which the cathode is moved through a circular path into and'out 1 of the bath.

' of two arms 14, each having a conductor core 15 conductively attached to the cathode, and

surrounded by insulation 16, such as bakelite, hard rubber, or the like. The conductive cores 15 of, supporting arms 14 are attached to terminals 17, to which the leads 18, 18 are likewise attached. Terminals 17 are mounted in bar 19, which is slidably ,mounted on uprights 20 supported by the tank 10 or by any other suitable means. From the rear of bar 19 projects pin 21. which'enters the elongated eye 22 of lever 23, which is fulcrumed .at 24 on a suitable support. The opposite end 25 of lever 23 projects somewhat into the path of movement of arm 26, which is fixed to shaft 27,

* bath,

.ductive core 39 covered terial 40, such as bakelite.

slowly b a pulley or other suitable means 28. The rotation of the arm 26 in the direction indicated by the arrow causes it to engage the end 25 of lever 23 durin a small angle of its movement, which may e determined in accordance. with the relative periods of immersion and removalof the cathode which, in turn, are determined according to the conditions of operation'of the as previously described. The engagement of arm 26 with lever'23 raises the bar 19 and with it the cathode 13 above the surface of the bath (shown in dotted lines) and retains it thereabove until said engagemountedjon a suitable support and rotated ment ceases, at which moment the bar, with the cathode, drops. The forcible reimmersion of the cathode in the bath has a washing action upon the former.

In the device shown in Figs. 3. and 4, 31 is the vessel containing the bath in which the anode 32 is suspended from bar 33. The cathode 34, upon which the deposit is to be formed, is attached to arms 35, which are formed with a conductive core 36, preferably of metal, surrounded by insulating material 37, such as bakelite, the core bein conductively connected with the conductive-surface of the cathode. The arms 35 are fixed to shaft 38, which is also by insulating ma- The cores 36 of the arm 35 are conductively connected to the core 39 of shaft38, which core 39 isconnected to lead 41. Shaft 38 is passed through stufiing boxes 42 in the sides of the tank, and is rotated by a pulley 43 or other suit-- able means. The position of the shaft 38 and the. length of the arms 35 is such that a small arc of its path is outside the surface of the bath, the angle of this are and the formed with a con rate of movement of the shaft being so selected that the periods and frequency of removal of the cathode are those determined as proper for the conditions of operation of the specific bath in use.

It is obvious that many other mechanical devices may be employed for effecting the periodic removal and reimmersion of the cathode, such as devices of the rotating wheel or moving belt type with a plurality of cathodes attached to the periphery of the wheel or belt, or devices wherein the cathode is maintained stationary and the bath moved toward and away from it. When found advantageous one or I more anodes may be placed on each side of the cathode support.

As illustrative of the resultswhich I have obtained, using a bath of the composition:

Nickel sulfate, 240 g.; nickel chloride, 20 g.; boric acid. 40 g.; water, 1 liter, operating at'130 F. and with a current density of 200 amperes per square foot, by removing the cathode for periods of two to six' seconds at intervals of one to two minutes, I have formed deposits upwards of one sixteenth of an inchthick and entirely malleable hoable deposits of greater thickness than could hitherto be obtained with any bath b means of a bath containing only nickel sul ate and a little sulfuric acid. The character of the result of the process I have found to be the same in the deposition of cobalt, iron and alloys or mixtures of cobalt with nickel etc.

I have furthermore found that the use of I my invention prevents to a greatdegree the deleterious effects of i1 purities such as iron,

copper, arsenic, etc., in the salts of the bath or in the anode, and of solid matter in the bath.- 7

I claim as my invention 1. In. the process of electrodepositing metals, repeatedly removing the cathode surface from the bath for a period of time suflicient to permit the hydrogen on the deposited metal to be substantially eliminated from each successive layer of the deposited metal, and returning it thereto during deposition.

2. In the process of electrodeposltmg metals, eriodically removing the cathode surface rom the bath for a'period of time suflicient to permit the hydrogen on the deposited metal to be substantially eliminated from each successive layer of the deposited metal, and returningitthereto during deposition.- i

3. In the process of eleetrodepositing to during deposition, the period ofremoval of the cathode surface being less than the critical period at which a separable deposit is formed. a

4. In the process of electrodepositing nickel, repeatedly removing the cathode surface from the bath for a period of time sufficient to permit the hydrogen on the de posited metal to be substantially eliminated from each successive layer of the deposited metal, and returning it thereto during dep- ()SltlOIL;

5. In the process of electrodepositing nickel; periodically removing the cathode surface from the bath for a period of time sufficient topermit the hydrogen on the deposited metal to be substantially eliminated from each successive layer of the deposited metal, and returning it thereto during deposition. 1

6. In the process of electrodepositing nickel, repeatedly removing .the cathode from the bath and returnin it thereto during deposition, the period 0 removal of the cathode being less than the critical period at which a separable deposit of nickel is formed. 1

7. In the process of electrodepositing nickel, repeatedly removing the cathode from the bath and returning it thereto during deposition, the period of removal of the cathode being not greater than fifteen sec-- onds. i Y

8. In the process of electrodepositing nickel, repeatedly removing the cathode from the bath and returning it thereto during deposition, the period of removal of the cathode being at least two seconds and less than the critical period at which a separable deposit is formed.

.9. In the process of electrodepositing metals, repeatedly removing the cathode from the bath and returning it thereto during deposition, the frequency of removal of the cathode varying in accordance with the rate of formation of hydrogen in the means of a current of hig mg the cathode at intervals of one half to bath.

10. In the process of electrodepositing nickel, repeatedly removing the cathode from the bath and returning'it thereto during deposition, the frequency of removal of the cathode varying in accordance with the rate of formation of hydrogen in the bath.

11. In the process ofde ositing' nickel by dens1ty, removthe cathode surface beingl -ly all of theydrogen on the deposit to -dissi ated but less than the critical fifteen seconds for periods of one to fifteen seconds. V 12. In the process of electrodepositing metals of the iron. group, repeatedly inter posing a gaseous medium between the cathode surface and the bath and restoring contact between said surface and said bath, the period of the interposition of the gaseous medium between said surface and said bath being less than the critical period at which a separable deposit is formed.

13. In the process of electrodepositing .inetals of the iron group, repeatedl interposing a gaseous'ox dizing medium etween-I 1 the cathode surface and-the bath and restoring contact between said surface and said bath, the period of the-interposition of said medium between said surface and said bath being less than the critical period at which a separable deposit is formed.

14. In the process of electrodepositing metals of the iron group, repeatedly interand said bath being less than'the critical period at whicha separable deposit is formed.

15. In the process of electrodepositing metals, repeatedly removing cathode surface from the bath and returning it theretoduring deposition, the period of removal of sufiiciently great to permit substantially a of ,the hydrogen on the deposit to be dissipated but less than the critical period at whlch a separable deposit is formed.

16. In the process of electrodepositing nickel, repeatedly removing cathode surface from the bath and returning it thereto during deposition, the'period of removal of the cathode surface being sufliciently great to permit substantially all of the hydrogen in the deposit to be dissipated but less than the critical period at which a separable deposit of nickel is formed.

17. In the process of electrodepositing metals of the iron group, repeatedly removing cathode surface from the bath and returning it thereto during deposition, the eriod of removal of the cathode surface being suflicientl great to permit substantial; period at w iich a separable deposit is forme w CHARLESP. MADSEN.

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