US3093557A

US3093557A - Methods and electrolytes for depositing nickel and cobalt

Info

Publication number: US3093557A
Application number: US133800A
Authority: US
Inventors: Jr Richard P Cope; John R Drobne
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1961-08-25
Filing date: 1961-08-25
Publication date: 1963-06-11
Anticipated expiration: 1980-06-11

Description

United States Patent 3,093,557 METHODS AND ELECTROLYTES FOR DEPOSIT- ING NICKEL AND COBALT Richard P'- Cope, JL, Wilkiusburg, and John R. Drobne,

Munhall, Pa.,. assignorsv to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvama No Drawing. Filed Aug. 25, 196.1, Ser. No. 133,800 14 Claims. (Cl. 204 -43) This invention relates to bright metal electroplating methods and novel electrolyte compositions. More particularly, this invention relates to an electrolyte from which bright nickel, cobalt and alloys of nickel-cobalt may be electrodeposited.

Many compounds are known to be useful as additives to nickel, cobalt and nickel-cobalt alloy electrolytes. Aliphatic nitriles are among the compounds that have been usedf These nitr-iles have beenusedincon-junct-ion with well known organic sulfon=compounds known in the art as carriers or regulators. Examples of systems incorporating'nitriles in conjunction with organic sulfon-compounds as carriers or regulators are disclosed in US. Patent 2,882,- 208 and US. Patent 2,524,010. The known n-itrile brighteners are volatile, poisonous liquids. They are extremely hazardous because they are nerve poisons that migrate through the skin, possibly effecting permanent brain damage. Not only are such compounds dangerous to handle, but many twillboil out of plating baths at high tern peratures. The hazards'of exposure to such vapors is obvious.

Accordingly, it is the general object of this invention to provide a novel system for bright nickel plating incorporating soluble solid dicyano compounds as 'brighteners.

It is a more particular object of this invention to provide a system for bright nickel, cobalt, and nickel-cobalt alloy plating incorporating soluble solid dicyano compounds which may be safely handled.

We have discovered a method of improving electrolytes of nickel, cobalt and nickel-cobalt alloys by the incorporation therein of a predetermined amount of a series of dicyano' compounds that are solid at room temperature and are highly effective brighteners. Since they are solids, the corn-pounds are safer to handle than the volatile nitrile liquids. While these compounds cannot be ingested without possible serious consequences, the problemv of inhalation is essentially eliminated. Higher plating bath temperatures may be employed without generating hazardous vapors. Higher temperatures permit the use of higher current densities;

Using these compounds in the hereinafter described electrolytes, it is possible to electrodeposit bright coatings which are fairly ductileand level. The compounds are selected from the group consisting of dicyanoketeneethyleneacetal and compounds having the formula:

. NEG R wherein R is a radical selected from at least one of the group consisting of NH 0R and NHR in which R is an aliphatic monovalent hydroc-arbonradical with one to three carbon atoms. The R substituents need not be the same in a given compound. The brighteners of this invention may be used with sulfur-containing carriers or regulators known in the art. The aliphatic monovalent hydrocarbon radical R is limited to those radicals having from one to three carbon atoms. Radicals with a greater number ofcarbon atoms ordinarily result in compounds that are relatively insoluble in the electrolyte. It is ap- 3,093,557 Patented J mm 1 1, 1963 ice parent, then, that all solid dicyanoketene compounds cannot be satisfactorily employed in the invention.

The following series of compounds used in Examples I to IV hereinafter was produced as indicated:

(a) The d-icyanoketeneethyleneacetal used in Example- I was prepared as follows:

12.89 grams of tetracyanoethylene, two grams of urea as a catalyst, and 24 ml. of ethylene glycol were heated on a steam bath until the tetracyanoethylene went into solution. The product was poured into ml. of ice water, filtered and recrystallized in an alcohol-water solution. The resulting fluffy light brown needles had a melting point of 112,113 C.

(b) The. 1,1-dicyanos2,2 diaminoethylene used in Example II was prepared as follows:

6.7 grams of d-icyanoketeneethyleneacetal and 21.5 of concentrated ammonia were refluxed for ten minutes. The product was permitted to stand overnight. The light lzarowr3 material recovered had a melting point of 247- (c) The 1,1-dicyano-2,Z-diethoxyethylene used in Example III was prepared as follows:

' 6.4 grams of tetracyanoethylene, 3 gram-s of urea as a catalyst and 50 ml. of alcohol were heated ona steam bath for 20 minutes. The product was cooled and then evaporated to 25' m1. at room temperature by blowing air across it. Then, 25 ml. of water Was added. The material was cooled, filtered and air dried. The white crystals produced had a melting point of 54 to 56 C.

(d) The l,l-dicyano-Z,2-di-n-propylamine used in EX- ample IV was prepared as follows:

6.7 grams of dicyanoketeneethyleneacetal dissolved in, 50 ml. of Water and 10 ml. of n-propylamine were refluxed for 20 minutes. The product was cooled to 0 C. and then filtered. A light brown precipitate resulted.

' The foregoing compounds are incorporated into plating baths as illustrated by the following specific, examples:

The bath is agitated with air. A highly bright, leveled and fairly ductile nickel deposit is obtained. The deposit 1sv bright in the current density range from 10 to 250 amps/sq. ft. 1

Example 11- Cobalt sulfate, CoSO .7I-I O oz ./gal. 67 Sodium chloride, NaCl ..oz./gal. 2 Boric acid -c "oz/gal.-- 6. 1,1-dicyano-2,2-diaminoethy1ene ;oz./gal., .01 Napthalene trisulfonic acid oz./gal... 1 Sodium 2-ethylhexyl sulfate oz./gal; 0.003 pH a f 4.5. Temperature F..'. i 120,

Agitation is achieved with cathode rod movement. A bright'leveled and fairly ductile deposit is obtained. The deposit is bright in the current density range from 10 to 200 amps/sq. ft.

Example III NiCl- .6H O oz/gal.-- 10-30 H BO oz./ gal.-- .0-8- 1,1-dicyano-Z,Z-diethoxyethylene oz./gal.;.. 0.01 Sodium styrene sulfonate oz gal. 0.01 Sodium lauryl sulfate ..oz./gal. 0.02 pH A I 3.5 Temperature F 3 Agitation is achieved with cathode rod movement. A bright, leveled and ductile nickel deposit is obtained. The deposit is bright in the current density range of from to 150 amps/sq. ft.

l,l-dicyano-2,2-n-propylaminoethylene oZ./ga1. 0.001

8-acetamido-3,6-naphthalene disulfonate oz./gal. 2.0 pH 4.0 Temperature F 150 Thebath is agitated with air. A bright nickel cobalt alloy deposit is obtained. The deposit is bright in the current density range of from 10 to 100 amps/sq. ft. In a similar way dimethoxy and dipropoxy compounds may be employed in the bath to replace the 1,1-dicyano- 2 ,2-diethoxyethylene.

The chloride of the electrolyte can be added as sodium chloride or magnesium chloride. The sodium lauryl sulfate and sodium 2-ethyl hexyl sulfate are well known wetting agents. Other wetting agents, known in the art, may also be used in the baths.

The brightener components of this invention may also be incorporated into sulfamate and fiuoroborate plating baths, as well as those in the examples, with equally good results. Bright plate may be obtained with brightener compounds of this invention at concentrations in the range of from 0.0005 to 0.05 oz./gal., in any of the foregoing experimental electrolytes.

Nickel-containing electrolytes suitable for electroplating nickel may be any acidic nickel salt solutions employed in the art for plating. It has been found that the single or double nickel sulfate and nickel chloride salts alone or in any combination may be employed. Other platable nickel salts may be employed. The nickel plating baths are acidic, having a pH of from 0.5 to 6. In many cases buffers, such as boric acid, and other addition agents, may be present; in some cases marked benefical results are obtained when they are present. Examples of suitable addition agents are organic sulfonates, such as naphthalene-1,5-disulfonic acid, ammonium sulfate, formaldehyde, nickel formate, sodium sulfate, sodium lauryl sulfate, and ammonium chloride. Gum arabic and gum tragacanth and the like may be present. If required, additions of hydrochloric or sulfuric acid may be made to the electrolytes.

For plating cobalt, the electrolyte may contain cobalt sulfate, cobalt chloride or mixtures thereof. Similar addition agents to those used with nickel electrolytes may be added to these solutions to advantage. The pH of the aqueous electrolytes may be from 0.5 to 6.

In plating nickel-cobalt alloys, mixtures of nickel salts and cobalt salts are dissolved in the aqueous electrolyte. The baths have a pH range of from 0.5 to 6. For alloy plating cobalt-nickel anodes are used. Particularly useful alloys are those containing from 80% to 97% nickel by weight and 20% to 3% cobalt by weight. However, alloys containing greater amounts of cobalt may be readily plated. Alloys of nickel and/or cobalt and iron and iron alone may also be deposited from electrolytes containing the additives described heretofore with similar advantage.

The compounds of this invention are particularly valuable in fast cycle reverse current plating baths. Lower concentrations of the brighteners may be used in the fast cycle reverse current processes with excellent results. A desirable periodic reverse current process is described in US. Patent No. 2,470,775 to Jernstedt et al., assigned to the assignee of the instant application. A periodic reverse current in which the cathodic portion of the cycle, applied to the member being plated with nickel, is two seconds or less or, preferably, less than one-half second and an anodic portion of the cycle from one-half to one-twenty fifth of the cathodic portion with the current densities adjusted so that the anodic portion of the cycle applies from 4% to 60% of the coulombs of current applied during the cathodic portion of the cycle, will produce excellent electrodeposits. The cycles may be reduced in time to as little as A of a second cathodic period and of a second anodic period with benefit. Below an anodic time period of about second, the deplating is not effective enough to give the full advantage of periodic reverse current plating.

The following examples illustrate the results obtained with the brightener compositions of this invention in the periodic reverse current process:

A periodic reverse current cycle is used with periods of 1s second and second for the cathodic and anodic portions, respectively. Bright ductile and leveled electrodeposits of nickel are obtained at from 10 to 200 amps/sq. ft.

A periodic reverse current cycle is used with periods of second and second for the cathodic and anodic portions, respectively. Bright, ductile and leveled electrodeposits of cobalt are obtained from about 10 to 60 amps/sq. ft.

In the periodic reverse current processes, excellent bright deposits of nickel, cobalt and nickel-cobalt alloys can be produced from solutions having brightener com pounds of this invention at concentrations as low as 0.00005 02/ gal. and as high as 0.05 oz./ gal. The regular uninterrupted current processes employ the compounds at concentrations from 0.0005 to 0.05 oz./gal., as outlined heretofore. The economics of such low brightener concentrations in the periodic reverse current processes are obvious.

While there have been shown and described what are presently considered to be the preferred embodiments of the invention, modifications thereto will readily occur to those skilled in the art. It is not desired, therefore, that the invention be limited to the specific arrangements shown and described and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention. We claim as our invention:

1. An acidic solution for electrodepositing a metal selected from the group consisting of nickel, cobalt and nickel-cobalt alloys containing a soluble salt of said metal and a brightener compound selected from the group consisting of dicyanoketene-ethyleneacetal and compounds having the formula:

NEG R NEO \R wherein R is selected from the group consisting of CR NH and NHR wherein R is an aliphatic monovalent hydrocarbon radical with 1 to 3 carbon atoms, said brightener being present in a concentration range of from 0.00005 oz./gal. to 0.05 oz./gal. of solution.

2. An acidic solution for electrodepositing a metal selected from the group consisting of nickel, cobalt and nickel-cobalt alloys containing a soluble salt of said metal and dicyanoketeneethyleneacetal in :a concentration range from 0.00005 to 0.05 oz./gal. of solution.

3. An acidic solution for electrodepositing a metal selected from the group consisting of nickel, cobalt and nickel-cobalt alloys containing a soluble salt of said metal and 1,1-dicyano 2,2-diaminoethylene in a concentration range from 0.00005 to 0.05 oz./ gal. of solution.

4. An acidic solution tor electrodepositing a metal selected firom the group consisting of nickel, cobalt and nickel-cobalt alloys containing a soluble salt of said metal and 1,l-dicyano-2,2-ethoxyethylene in a concentration range from 0.00005 to 0.05 02/ gal. of solution.

5. An acidic solution for electrodepositing a metal selected from the group consisting of nickel, cobalt and nickel-cobalt alloys containing a soluble salt of said metal and 1,1-dicyan=o-2,2-n-propylaminoethylene in a concentration range from 0.00005 to 0.05 oz./ gal. of solution.

6. A method of electrodepositing a metal selected from the group consisting of nickel, cobalt and nickel-cobalt alloys comprising the steps of electrolyzing an acidic electrolyte of said metal containing a brightener compound selected from the group consisting of dicyano-keteneethyleneacetal and compounds having the formula:

NEG R NEC/ R wherein R is selected from the group consisting of NH CR and NHR wherein R is an aliphatic monov-alent hydrocarbon radical with 1 to 3 carbon atoms, said brightener compound being present in a concentration range from 0.00005 to 0.05 oz./ga1. of solution.

7. A method in accordance with claim 6, wherein said brightener compound is dicyanoketeneethyleneacetal.

'8. A method in accordance with claim 6, wherein said brightener compound is 1,l-dicyano-2,2-diaminoethylene.

9. A method in accordance with claim 6, wherein said brightener compound is 1,1-dicyano-2,2-n-propylarninoethylene.

10. A method of electrodepositing a metal selected from the group consisting of nickel, cobalt and nickelcobalt alloys on a member comprising the steps of applying current to the member, While in contact with an acidic electrolyte of said metal containing a brightener compound selected from the group consisting of dicyanoketeneethyleneacetal and compounds having the formula:

NEG R NEC R wherein R is selected from the group consisting of NH CR and NHR wherein R is an aliphatic monovalent hydrocarbon radical with 1 to 3 carbon atoms, said bright ener compound being present in a concentration range from 0.00005 to 0.05 oz/gal. of solution, said current being periodically reversed so that the member is successively cathodic for a period less than two seconds, then anodic for a period /2 to of the cathodic period but not less than of a second.

11. A method in accordance with claim 10, wherein said brightener compound is dicyanoketeneethyleneacetal.

12. A method in accordance with claim 10, wherein said brightener compound is 1,1-dicyano-2,2-diaminoethylene.

13. A method in accordance with claim 10 wherein said brightener compound is 1,1-dicyano-2,2-ethoxyethylene.

14. A method in accordance with claim 10, wherein said brightener compound is 1,l-dicyano-2,2-n-propylaminoethylene.

References Cited in the file of this patent UNITED STATES PATENTS 2,470,775 J ernstedt et \al May 24, 1949 2,524,010 Du Rose et al. Sept. 26, 1950 2,781,306 Brown Feb. 12, 1957 2,882,208 Becking et al. Apr. .14, 1959 2,972,571 Towle Feb. 21, 1961 2,978,391 Du Rose Apr. 4, 1961 OTHER REFERENCES Middleton et al.: J. Am. Chem. Soc, vol. 80, pp. 2788- 2795, June 1958.