US172862A - Improvements cobalt electroplating - Google Patents

Description

used.

LIN-Iran STATES PAT NT omen;

a s o DAMs, JR, or BOSTON, MASSACHUSETTS.

IMPROVEMENT IN COBALT ELECTROPLATlNG.

Specification forming'part of Letters PatentNo. 172,862, dated February 1, 1876; application filed v January 17, 1876. I v

shows that various experiments have been:

made by electro-metallurgists in the electrodeposition of cobalt;.and so far as these experiments or processes are described in the books, it appears that allusions to such deposits have been made as early as 1844, andsince that date reference to the same subject may be found in the works of Since, Becqu'erel, Ellsner, and Gore.

Gore (1860) simply mentions thesolution of the chloride of cobalt as one which may be Ellsner (Leipsic, 1851) recommends the cyanide of cobalt and potassium. Becquerel, in a note printed in the Oomptes Rendus of the French Academy for July, .1862, states that he has obtained 'a good deposit from the neutral chloride of cobalt. Smee, in his work on electro-metallurgy, (London, 1844,) in a measure contradicts Becquerel as to the chloride of cobalt, and recommends the solution of the chloride of cobalt with excess of ammonia. He says: cobalt may be reduced from its chloride, to which excess of ammonia has been added, by usinga cobalt positive pole connected with a series of batteries, when the deposition will take place upon the negative plate, which may consist of copper.

The reduced metal is white, but it is not thrown down freely. The chloride of cobalt alone seems only to yield an oxide at the neg-' ative pole. The cobalto-cyanuret of potassium, formed by digesting oxide of cobalt in the cyanurct, yields, by decomposition with a compound battery, some metal, but hydrogen 7 has a great tendency to be evolved from this solution.

exigencies of his art. I have found. that a solution made and used in the manner described in the books will not produce such a continuous and uniform deposit of cobalt as is necessary for the successful and practical electroplating of metals with cobalt, and that if the electroplater follows the directions given in the books he not only will be unable to produce successful practical cobalt-plating,

but in some cases will bring his solution into I such a condition as to prevent any useful deposit of cobalt.

I .have found, further, that the simplesalts of cobalt, such as are recommended by Bee querel and others, are not such salts as can .be used in the practical electroplating with cobalt, and this I find to be true even if they are prepared from pure cobalt.

I have found out, also, that the simple saltsof cobalt, when associatedwith another electrolytesnch as the vchloride of ammonium, or the sulphate of ammonia, or the chloride of magnesium, or the sulphate of magnesiacan be used so as to produce good results in practical cobalt-plating; and I find that no good results can be obtained except by the use of a simple salt .of cobalt in combination with some other electrolyte of the alkalies or alkaline I have found that the best of such combined salts are, the chloride of I cobalt and ammonium, the chloride of cobalt and magnesium, the sulphate of cobalt and ammonia, or the sulphate of cobalt and magnesia. 1

I have found, further, that, in order to produce the best results, the cobalt solutions place in solutions in which exist salts of alkaliessuch as the nitrates of soda or potash, or free nitric acid-and the reason of this, I believe, is, that wheiithese salts are present in the solutions in appreciable amount potash and soda are eliminated in the actual use of the solution simultaneously with the deposit of cobalt, and thus the deposit is rendered worthless for the purposes ofthe electroplater. Such salts of alkalies, and likewise free acid, are, liable to exist in the solution when used, either because they have been introduced therein in the process of making, or because they are introduced or formed therein in the actual using of the solution.

I have now stated, in general terms, the process which I find to be the best for practical cobalt electroplating.

' In order to enable a person skilled in the art to practice the process of cobalt electroplating so discovered by me,I give the following as a method by which he can make the necessary solutions and anodes. Pure cobalt is not found in the market, as there is no commercial demand for it, and therefore, in mostinstances, a cobalt solution would be made from black oxide of cobalt, which, in the state in which it is found in commerce, contains as impurities copper, arsenic, tin, iron, and manganese, or some of these substances, which it 1 is necessary to eliminate. Proceed as follows; Dissolve a given weight of the oxide of cobalt in hydrochloric aci'd.- To this solution add, for every pound of oxide used, a half, pound of the chloride of ammonium. Then filter the solution, it necessary, and to it add "sufficient ammonia to render the solution strongly ammoniacal. Then allow this ammoniacal solution to stand, with occasional brisk stirring, until it becomes of a wine-red color. Then add an excess of commercial murij atic acid, and raise the whole to the boilingred'heat in a crucible or other suitable vessel, 1 and a chloride of cobalt will be produced practically free from impurities.

To produce the chloride of cobalt and ammonium, make a solution by dissolving three ounces of the chloride of cobalt and two ounces of pure chloride of ammonium to each gallon of the solution.

To produce a solution of the chloride of cobalt andmagnesium, make a solution as above, substituting chloride of magnesium for the v -chlorideof ammonium.

To produce a solution of the sulphate of co balt and ammonia, dissolve the chloride of cobalt inwater, and for every five parts of such dry salt add four parts, by weight, of sulphuric 1 acid and evaporate 'to dryness; redissolve in; water and add five parts of pure sulphate of 3 If there should be an excess of acid,

ammonia. neutralize with ammonla.

To. produce the sulphate ofcobalt and mag- I do not claim the processes of making these solutions as my invention, and in no way limit my invention to the'iprecise chemical processes by which these solutions are produced ready for use.

The solutions, when made as above described, will mark from 6 to 7 Baum, though much weaker solutions may be used, and even stronger ones, if desired.

I do not confine my inventio n to the particularproportions of each salt contained in the solutions above described, forthe proportions of each salt may be varied in any given solution. I have given theabove proportions of these saltsas those which I prefer.

The method for producing a suitable anode to be'used with these solutions is as follows: Precipitate the chloride of cobalt with potash; soda, or carbonate of ammonia then makea solution of tartaric acid, about three partsof acid to two parts of dry chloride, and add to it the moist oxide of cobalt, and raise the whole to the boiling-point. A tartrate of co balt is formed, which throw uponthe filter and wash several times with boiling water, dry, mix with a little lamp-black or other suitable form of pure carbon, and heat to whiteness in a closed Hessian or other suitable crucible. The tartrate of cobalt is thus reduced to the metallic state and fused, and can then be readily cast into plates or anodes of any desirable form. r

After the solutions and anodes have been prepared as herein described, cobalt may be readily and continuously deposited; but in order to carry on the deposition of cobalt continuously it is necessary to observe certain pre cautions. First, great care should be exercised, in preparing the work for plating, that none of the acid or alkaline dips should be introduced' into the solution. Second, anot too high battery-power should be used a strength of current of two Smee cells is sufficient.

In plating articles of zinc with cobalt it is first necessary to coat them with copper.

Having thus describedmy invention of improved processes of electroplating with cobalt, I claim-- v I i 1. In the electro-deposition of cobalt, the

use of a solution of a simple salt of'cobalt,

combined with another electrolyte, consisting of a salt of the alkalies or alkaline earths, substantially as described' v 2. The use, in the electro-deposition "of cosium, or sulphate of cobalt :andammoniayor 3 the sulphate of cobalt and magnesia, substantially as described. .j

alkaline, substantially as described. Y

I 3. The use,.in th'e-eleetro-deposition of cobalt;iwhich consists'in convertingthe -chlohalt, of a neutral solution, neither acid nor ride or other salt of cobalt into the tartrate,

mixing this with carbon, heating to reduc- .4. The use, in the electro-deposition of co tion, and finally casting, substantially as debalt, of solutions of cobalt, in the manner described. scribed, so as to be at alltimes' during the op- I eration free from the presence of soda, potash, Witnesses: or nitric acid, or either of them. E. N.- DIGKERSON, J r.,

"ISAAC ADA s n.

5. The process of making an-anode of co- JNO. RrLEFFERTs.