US1607994A - Means for electrodepositing metals - Google Patents

Description

7 move the Patented} Nov. 23, 1926.

' UNITED STATES vCHARLES I". MADSEN, 01f YORK, N. Y., ASSIGNOR TO MAIDSIEEI'EIILL COBPORATiION, OF NEW YORK, N. Y., A' CORPORATION OF YORK.

: mama non nnnornonnrosrrmo mnrnns.

Ho Drawing. Application filedAug'nst 4, 1921, Serial No. 489,352. Renewed June 4, 1826..

' My present invention relates to. theelectrodeposition of "metals, particularly the nickel metals, by which I mean'metals oi the nickel. group, particularly nickel, cobalt, e andzalloys containing substantial amounts of either or of both of these metals, It is an object of the present invention to provide means for electrodepo'siting such metals in'such a form that they will be mechan- 1U jeally perfect, that is, substantially free fromv pores and its, and will be annkalable as well as uctile and malleable. "It

. is a further-object of the present invention to-devise means of the character described which will be. simple to put into operation and which will permit the production of metal of the character specified within a wider range of working conditions than has heretofore been deemed possible.

In other words, it is an object of the present invention: to provide a readily workable, commercial process for electrodepositing nickel metals, the process being so simple and efi'ective aseto permit its ready adoption andi'cperation under ordinary factory conditions without elaborate precautions and without a lar e number of tests and checks to ensure this proper result.

In the accompanying specification I shall 3' set' forth several illustrative embodiments 0f 'the' means of my present invention, it

being understood, however, that my invention s not limited to the particularernbodiinents thereof which are herein described 3- for purposes of. illustrationbnlyn Before describing in detail the aforesaidillustrative embodimentsLof-my present invention, it m-aybe desirable to! point out briefly= .certaindisadvanta 'es of. the rior 4c .Meenan to the electrodeposition 0 the fcannot be made ductile even by annealing,

It is; generally understood that; this condl-v t-ion is due largely to the presence of hydro-- gen in the electrolytic nickel. However, nickel made by processes-'calcnlated to re-'.

,iietzling, while both' kinds of electrolytic nickel as now made are frequently filled produced such metal -by a hydrogen, although initially Lslightly more malleable than the ordinaryelectrolytic'nic'kel, becomes less 'soupon an In my copending application, Serial No: 254,793 filed Se 12.19, 1918, entitled Processfor the electro eposition of metals, I have; disclosed means for mechanically manipulating the cathode so as to llar el ,and' in many instances, entirely, 'avoi t e formation of pits. d m S In another co n ingapplication erial No. 292,793 filed I Electrodeposition of metals, I'have disclosed "April 26, 1919, entitled an improved form ar bath by means of which, when the factors of. deposition are properly regulated, I may still further minimize'the formation of. its and at the same time produce a meta which is annealable. 7 j

in still another copending application, Serial No. 388,812 filed June 14, 1920,'an(l entitled Anodes and methods of preparing the" same I have disclosed a new typeof' anode which practically continuously maintains the proper working conditions of my new bath mentioned above, and by means of which I am enabled, in combination with the mechanical manipulation of the cathode detcribed above, to ,prod-uce'pitless nickel metal ofa high degree of ductility, which metal is at [the sameftimeannealable. I have, in fact, under favorfble conditions 'process which uses only the ubove ba'th an, anode.

I have discovered new means for accomoperate to obtain pitless, malleable; ductile While I and annealable nickel metal. may use the new means of my present 111-.

. vention to great advantaged-n connection pl-ishing the same general result of my pre- 7 with most of the old and well known nickel electrodcposition processes with which I am familiar, my present invention finds p articularly successful applicat on in connection with the bath and anode. ofymy two pre viously filed applications last referred to above."

It has been' -thoughtior sometime that. e hydrogen is'a .factor "in'causmg the formation of pits, but prior. to thedevelopment of they improvements referred to above,

means for the complete IGmOVaIOf hydrogen had not'been found, and the mechanism of 1 pit formation has not, untilmy present inyention, been satisfactorily explained. The indicat ons are that another factor in the formations of pits is the presence in the bath of solid foreign particles. These particles are often deposited on the cathode, and, either by catalysis or by the'formation of a local cell, or for bothreasons, apparently I causg the combination of atomic hydrogen ried over mechanically from the anode.

- 1 I have, moreover, discovered thatanother class of foreign bodies, which I believe has not hitherto been suspected as being a factor in the formation of pits, is probably another cause of pit formation. This class comprises organic materials in the nature of small par.

ticles of dust, spores, bacteria, microscopic seeds, and the like. Most of these organic particles drop in from the air during electr0l-' ysis, but'many of them are already present inthe commercial nickel salts and in the other materials from which the bath is made up. It appears that not only can these organic materials exist in the bath but that they may even propagate and grow there.

' I have found large growths of funga and other plant life, the exact description of which, however, is unknown, present in nickel baths which have stood idle for as long as several weeks.

- That these organic materials comprise one of the factors of pit formation is indicated by the fact that a newly prepared bath generally makes more pits than one which has been incdntinuous use. Moreover, a bathwhich has been standing idle for several weeks makes still more pits than either of the baths mentioned above, and in this case the organic material is often clearly visible.

Removal of this organic material by filtration or other mechanical means alone is not effective, ne ther has' 1t been found practical .to. prevent the transfer of foreign'particles from the anode by means of bags, as any bag material fine enough to stop the particles will interfere with the electrolysis,

I have stated above that all, and particularly commercial nickel, salts and other ingredients used in making up a nickel bath, contain organic material. Commercial nickel salts-also contain iron and copper, generally in the form of their chlorides and sulphates. I prefer, therefore, as a preliminary step to my new process, to purify the nickel salts or electrolyte made from the same. For this purpose I may use any agent, preferably an oxidizing agent, which will act to remove the organic matter and also the iron and copper salts from the nickel salts or from the electrolyte containing the same in solution. Where, as is preferred, an oxidizing agent is used for this purpose, I find that there are several oxidizing agents which, while they will remove'the organic matter and the iron, will not ordinarily effect the removal of the copper. I have found, however, that the use of chlorine gas as the oxidizing agent will, under certain conditions,-produce'a new and unexpected result in that this agent not only removes the organic matter and the iron from the bath, but at the same time removes substantially all of the copper.

To carry out this proposed. preliminary purifying step, I preferably make up a concentrated nickel salt solution intended to contain, for example, about 240 grams of nickel sulphate and about 20 grams of nickel chloride per liter of bath, by dissolving the salts in only half of the required amount of water, at the same: time heating this concentratedsolution of nickel saltsto keep the same in solution, for which purpose I prefer to heat the concentrated solution to a temperature of from 30 to about 40 C. To the other half of the required water I add an amount of caustic, as sodium, hydrate, somewhat-in excess of the chemical equivalent of the free acid and of the ironand copper salts present in the nickel salt solution.

These two solutions are then mixed together and stirred very rapidly. An'almost completeand immediate alkelinization of the solution takes place, precipitating very little nickel, while the-iron is at once precipitated in the form of a precipitate of gelatinous or colloidal ferrous hydrate, which acts as a reducing agent. Chlorine gas is now bubbled slowly through the mixture while stirring the same, the addition of chlorine gas continuing until the precipitate, as indicated by asample, is of a light brown color. If the ferrous hydrate has not been oxidized to the point indicated by the light brown color of the precipitate, it will not filter outvreadily',

whereas if the chlorination is carried out.

much beyond this point, the copper apparently goes into solution again. All of the reasons for this action are not clearly understood. My present theory, however, is that the cupric sulphate present in the bath is converted, into the corresponding chloride which. in the presence of the ferrous hydrate initially present in the bath, is reduced to cuprous chloride. with the simultaneous oxidation of the ferrous hydrate to the ferric condition indicated by the light brown'color referred to. The cuprous chloride, being insoluble. is precipitated from the solution while the ferrous hydrate, which has acted as a reducing agent for converting the cupric salt into the cuprous condition-and which has thus been converted into the ferric state,

-settles all the more readily than it otherwise would. It may here be stated that there is generally more added. Where the bath is to be used with an anode which is being used as such for the first time, it may be desirable to permit any residual chlorine to remain in the bath, since this residual chlorine is carried by the current to the anode, where it acts to more effectively help to dissolve the same and to break down the outer, diflicultly soluble skin present on many types of anodes. Otherwise, the residual chlorine may be eliminated by any'suitable means, as by boiling the bath.

1 the anodes.

A bath so prepared will, in combination with my anodes referred to above, produce ductile, pitless and annealable' nickel until particles commence to be transferred from At this juncture pits may form. Moreover, if the anode-cathode surface ratio is not correct, the pH reading may change and cause pits to be formed. Furthermore, after such a bath has been kept standing idlefor even comparatively short periods, especially if the bath is warm,

its may be formed on resuming operation of the bath. In such cases re-chlorinating the bath is often effective in preventing further pit formation.

I have, however, discovered that other oxidizing agents besides chlorine are effective in overcoming the pits when they once commence to be formed after the bath has been preliminarily treated with chlorine. Such other oxidizing agents effective inpreventing pit formations comprise,- for instance, the permanganates and also those salts which, during electrolysis, pass through intermediate stages duringuvhich they give off oxygen. An example of ItIhese ever, these materials are open to the objection that the by-products of decomposition either make more sludge, which may serve to darken and roughen the deposit and to cause other difficulties. or may add increasing amounts of undesirable soluble" salts to the electrolyte.

I have discovered that hydrogen peroxide is even more effective than any of these reagents and is even more effective than chlorine for preventing pit formation after the preliminary oxidation. treatment, although hydrogen peroxide may also be used for the preliminary oxidation treatment. although for this purpose it" is not so effective for removing the copper, however eflicient it is for precipitating the iron and oxidizing the organic matter present in the bath. Hydrogen peroxide is desirable for use for pit prevention since it does not produce any 7 sludge, nor does it add any undesirable or other soluble salts to the bath. It is also probable that the hydrogen peroxide profduces other desirable results in the bath I than that of merely oxidizing the organic 7 matter. In fact, this substance appears to act as a perfect cathode depolarizer to pre vent the evolution of hydrogen in either atomic or molecular condition at the cathode and thus to prevent the formation of its.

p Under the above conditions the hydro-.

gen, in atomic 'or molecular condition, de'

composes hydrogen peroxide instantly, with the formation of water. believed that the presence of hydrogen peroxide in the bath acts as a true cathode depolarizer .by combining chemically with both atomic and molecular hydrogen as soon as the same is formed. peroxide thereby acts to remove one of the principal factors in the mechanism of pit formation, so. that pits are prevented even though one of the other factors, such as inorganic foreign particles transferred from the anode, may still be present.

The addition of even small amounts of hydrogen peroxide to the nickel'bath produces highly satisfactory results. I find that it is generally not; necessary to use more than about cc. of a 3% solution of hydrogen peroxide per litre of bath for each It is therefore The hydrogen twenty-four hour run, providedthe bath is.

.amount of hydrogen peroxide, I prefer to 7 add about 4 cc. per litre to the bath upon the commencement of deposit-ion, after i which the bath may be fed at intervals with the calculated amount of hydrogen peroxide solution. Since, however, nickel baths are preferably run at elevated temperatures and are therefore preferably fed with distilled water, either through an automatic feed or by the drip system, I prefer-to add the. peroxide at intervals to the feed water. For this purpose I may add 4 cc. of a 3% solution of hydrogen peroxide per litre of bathto that amount of feed water which the bath takes for twenty-four hours. I The effect ofven this, small .am'ount of peroxide in absorbing hydrogen so as to prevent pit formation isso great that the bath 1 ,not only produces annealable and pitless fully, but also produces ductile metal which a is both pitless and annealable with afree excessive consumption of the hydrogen peroxide, with consequently greater likelihood of forming pits and unannealable metal. While I may also add colloidal nickel hydrate to the bath containing the peroxide, I find that this is no longer necessary and that any considerable quantity of such hydrate,

particularly if the bath is heated over 40 (1,

may cause difficulties through reacting with the. peroxide and decomposing the same faster than is desirable, as well as by itself becoming oxidizet txor otherwise decomposed and settling out of the bath as a sludge which may act to roughen the cathode deposit. Similarly, I may provide sodium or other alkali sulphate in the bath, this material, in the form of the invention described abovefbeing already present in the bath, due to the reaction between caustic soda and the sulphuric acid sulphates, particularly ferrous sulphate, present in the nickel salts of which the bath is prepared.

By means of the above described embodiment of my present process I am enabled to produce a ductile nickel metal which is not only softer than any new metal'hitherto known to me, but it is also at the same time pitless and perfectly annealable. By theterm annealable I mean that the nickel metal made in accordance with the preient invention and Whether or not it has previously had mechanical work performed upon it, may be heated to a red heatand cooled either slowly or quickly without embrittlement. Moreover if such metal has been annealed after it has been cold-worked, it will be softer than before. To illustrate the duotility of this new nickel metal, I have drawn a strip one sixteenth of an inch square, which has been sawed from a cathode, into 1 a wire .002 of an inch in diameter without annealing, during which operation the strip waselongated from eight inches to a length of eight hundred and thirty feet. This 'metal alsohas the unusual property of re tain'g, upon cold-working, considerable elongation power, while acquiring at the same, time a high degree of hardness as determined by the Brinell test. The Brinell factor of hardness of the deposited metal will vary from about 63 to about 80, according to conditions, and the elongation factor of such metal is approximately 32%. Upon cold-working the deposited metal to the ex tent indicated in'the example of wire drawing given above, the Brinell factor of hardness increases to about 183, and the tensile strength of the metal has'corre'spondingly risen from 72,000 lbs. per square inch to 250,000 lbs. per square inch, while the coldworked metal still retains an elongation factor of 10%.

The present process has the further advantage that it avoids the necessity of the exactitude of control of the various factors of deposition, such as pH concentration,

temperature, the current density, anodecathode surface ratio, etc-, former] i deemed necessary for the production of perfect metal. The present process is therefore chelaper to operate, particularly on a large scae. I

It is of course to be understood that my invention is not limited to the particular embodiments thereof herein described for purpo es of illustration only.

What I claim is: l

1. The method of electrodepositing nickel metals which comprises treating the electrodeposition bath with chlorine to oxidize organic matter present in the bath.

2, The method of clectrodepositing nickel metals which comprises treating the electrodeposition bath with an alkali hydrate to effect a removal of a part at least of the iron salts in solution in the bath. The method of electrodepositing nickel metals which comprises treating the electrodeposition. bath with chlorine in the presence of a metallic reducing agent to effect a removal of a part at least of the copper in solution in the bath.

4. The method of electrodepositing nickel metals which comprises treating the electrodeposition bath with chlorine in the presence of a metallic reducing agent under alkaline conditions to effect a removal of a part at least of the copper in solution in the bath. 1

The method of electrodepositing nickel metals which comprises giving the electrodeposition, bath an oxidizing treatment to oxidize organic matter present in the bath, and thereafter conducting the electrodeposition in the presence of an oxidizin'g agent. I

6. The method of electrodepositing nickel .metals which comprises treating the electrodeposition bath with chlorine to oxidize organic matter present in the bath, and thereafter adding hydrogen peroxide to the bath. 7. The method of nickel metals which comprises treating the electrodeposition bath with chlorine in the" presence of a metallicreducing agent electrodepositing toefl'ect a removal of a part at least of the copper in solution in the bath, and .thereafter adding hydrogen peroxide to the bath,

8. The method of electrodepositing nickel metals which comprises treating the electrodeposition bath with chlorine in the presence of a metallic reducing agent under alkaline conditions to efl'ect a removal of a part at least of the copper in solution in the bath, and thereafter adding hydrogen peroxide to the bath.

9. The method of electrodepositing nickel metals which comprises treating the electrodeposition bath with an alkali hydrate to remove a part at least of the iron salts 'in solution in the bath, and thereafter treating the bath with chlorine to etiect a removaluof .a part at least of the copper salts in solution in, the bath, and thereafter adding hydrogen peroxide. to the bath.

trodepositing nickel metal in the presence ofan oxidizing agent while regulating the acidity of the bath whereby-the deposit is rendered malleable.

13. The method of iron and copper salts in solution, which comprises removing the iron and copper salts from the solution and thereafter electrodepositing nickel metal in the presence of hydrogen peroxide while regulating the acidity of the-bath whereby the deposit is rendered. pitless.

14. Themethod of electrodepositing nickel metals which comprises passingchlorine through the bath and thereafter electrodepositing nickel -metalin .the

v electrodepositing k l metals from a bath containing presence of an oxidizing .agent while fegulating the acidity of'the" bath so that the deposited metal is malleable.

15. The nickel metals which comprises passing chloi'ine through the bath and thereafter electrodepositin nickel metal in the presence of hy ogen peroxide while regulating the acidity of the bath so that the deposited metal is malleable.

In testimonyv whereof, I have signed my name of this specification this 31st day-of 'July, 1921.

CHAS P. MADSEN.

method of electrodepositing,