US2291590A - Electrodeposition of metals - Google Patents

Description

- art.

Patented July 28, 1942 2,291,590 I C E 2,291,590 amo'monnrosrrron or METALS Rudolf Lind, Euclid, William J. Harshaw, Shaker Heights, and Kenneth E. Long, South Euclid, Ohio, asslgnors to The Harshaw Chemical Company, Elyria, Ohio, a corporation of Ohio No Drawing. Application March 11, 1940,

Serial No. 323,380

17 Claims.

This invention relates as indicated to electrodeposition of metals and more specifically, to a process of and materials for use in the process of electrodepositing nickel characterized in that the resultant nickel plate, as deposited, is both bright and ductile. More particularly, the pres ent invention has to do with new addition agents for producing the above-named desirable characteristics in the nickel plate and which may be used with acid nickel baths of usual composition operating under usual conditions.

In order to properly evaluate the present invention, it is necessary to define brightness and ductility or brittleness, terms used in the old art, but used loosely to describe all degrees of brightness or brittleness.

BRIGBTNESS It is obvious that an extremely thin deposit of nickel over a highly buffed surface will appear bright. Bright plates of this type have been made for years and are well recognized in the article is exposed to the atmosphere or to wear, the plate soon disappears or wears off. A plate thin enough so that it will retain substantially the full brightness of the polished base metal is impractical for use even as a base for the electrodeposition thereover of a protective coating of other metals such as chromium. If a heavier deposit is plated out, the brightness of the highly buffed surface diminishes and a gray or white dull deposit is obtained.

A nickel plate which is thick enough to be practical for use and which is brought without bufling is not only desirable per se, but it is particularly advantageous where it is destined for use as the base for an electrolytically deposited chromium plate, since, if the nickel plate does not require to be polished and bufied, a relatively thin plate gives the same protection as the necessarily heavier gray plate, some of which must be taken off in the polishing to secure the desired brightness. Furthermore, a very considerable saving in time and in cost on the production of plated articles becomes possible, whether with nickel plate per se or with additional chromium finish.

Various so-called addition agents have been proposed from time to time for inclusion in nickel plating baths in order to control or afiect the character of the electrolytically deposited metal. One principal objective in such modification of the plating bath has been to increase the brightness or luster of the deposited metal.

Many of these previous nickel plating addition agents have allowed a much heavier deposit of nickel to be built up before the brightness of the base metal was materially diminished. When polished articles are plated in such baths, the

Their limitations are that if the plated deposit is not truly bright but merely, at best, has the same character as the base metal. The brightness produced by such addition agents may, therefore, be characterized as-brightness diminishing with increased thickness of plate on a polished surface.

Others of these previous nickel plating addition agents have produced a plate which would maintain the brightness of the polished base surface, even though the plate was built up to a substantial thickness. They would not build up any substantial brightness on an unpolished surface and, at best, would only very slowly build up brightness on an unpolished surface when plates of extreme thickness were made. The brightness produced by such addition agents may, therefore, be characterized as brightness maintaining itself with increased thickness of plate on a polished surface.

The addition agents of produce a plate that not only maintains the brightness of the most highly polished base metal, irrespective of the thickness of the plate within practical limits, but also increases in brightness with increase in thickness of the plate on an unpolished surface. The brightness produced by such addition agents may, therefore, be characterized as brightness increasing with thickness of plate on'an unpolished surface.

DUCTILITY The question of ductility is one of vital concern to the plater. harder and, therefore, more brittle than ordinary dull nickel. When enough of many of. the previously employed addition agents was added to a bath to produce a bright plate, the plate was often too brittle for commercial use and yet if less addition agent was used, the plate would not be fully bright. A test for ductility may be made by plating on a non-adherent surface and stripping off the foil and bending it double on itself. A plate .001" thick which will pass this test without breaking is considered to have good ductility. A plate .0005" thick which will just pass this test is considered to have passable ductility. A plate .0002" thick which will not pass this test without breaking is considered to have poor ductility.

The addition agents of the present invention not only produce plates with the highest order of brightness, but also with a high order of ductility as defined by the above scale. This is desirable and essential to the practical use of bright nickel plating.

The principal object of the present invention, therefore, broadly stated, is to provide an improved process of and materials for use in the process of electrodepositing nickel which will not only render the nickel plate desirably bright but the present invention In general, all bright plates are,.

which will also preserve or render the plate desirably ductile.

Other objects of our invention will appear as the description proceeds,

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter more particularly pointed out in the claims, the following description setting forth in detail certain approved modes of operation of our process and combination of ingredients embodying our invention, such disclosure constituting, however, but certain of various forms in which the principles of our invention may be used.

Broadly stated, our invention. comprises the discovery that by the use in acid nickel electrolytes of a plurality of addition agents respectively selected from certain different classes of compounds, we are able to produce deposits which are superior to those obtainable by the use of addition agents from either one of such classes alone. We find that the addition agents from one of said classes, although characterized by an embrittling tendency, are productive of extreme brightness when used in combination with addition agents from the other class and that addition agents from said other class not only cooperate in the production of brightness but also exert a ductilizing effect in the combination. The use of one addition agent from each class is preferable but a plurality from each class can be used successfully. Our cooperating addition agents are suitable for use in a wide variety of nickel electroplating solutions. we have found them to be very effective in aqueous acid nickel sulfate solutions and aqueous acid nickel chloride solutions. Among the nickel sulfate solutions in which they are effective are aqueous acid solutions of nickel sulfate, nickel sulfate and nickel chloride, nickel sulfate and sodium chloride, nickel sulfate and hydrochloric acid, nickel sulfate and ammonium chloride, nickel sulfate and alkali metal chlorides other than sodium chloride, the chlorides serving to produce good anode corrosion. Our addition agents are effective in nickel chloride solutions with and without nickel sulfate. In each of said solutions it is desirable, although not necessary, to employ boric acid or another suitable buffering agent. We prefer to employ a bath containing nickel sulfate together with a suitable chloride, preferably nickel chloride and a suitable buffer, preferably boric acid. We prefer to employ one or more addition agents from one of said classes in quantity to produce the desired brightness and one or more from the other class in quantity to overcome to a substantial extent the resulting embrittling tendency.

Representative of separate classes of mpounds which, when used in combination as above stated, produce improved results, are those classes of compounds which may be identified as (1) aromatic compounds containing the group classes of addition agents are distinct, they will be discussed separately.

Aromatic nitrogen compounds Our invention contemplates, as indicated, the use of aromatic compounds of adequate solubility containing the group group, etc. The bonds shown to each aryl group are ortho to each other and the links connecting the Ar and Ar groups with N and :1: indicate single or double bonds. We do not know with certainty in all cases what type of bond exists but we have made use of materials having the acridine, azine, thiazine and oxazine nuclei. Reference is made to Schultz, infra, for accepted the- I cry of structure of these nuclei, the expression z Ar Ar' N being intended to indicate them generically. Ar and Ar may be identical or different. Ar and Ar indicate aromatic cyclic structures such as, for example, benzene or naphthalene nuclei which carry substituent groups. We prefer to employ compounds carrying one or more amino groups connected to ring carbon. Alkyl amino or aryl amino substituents such as N(Me)z. NHMe, --N(Ph)2 and the like also are desirable and may be regarded as amino groups. Compounds containing alkyl, such as methyl, ethyl, etc., halogen, sulfonate, hydroxy and nitro groups may also be used. The substituent groups such as aminogroups, including alkyl amino groups, appear to be desirable as such while groups such as the sulfonate and halogen groups, unless needed to improve the solubility, apparently are undesirable or indifferent.

The salts of such of these compounds as are basic, e. g. the chlorides, hydroohlorides, acetates and sulfates are to be preferred to such basic compounds themselves because of their greater solubility. It is essential that these compounds, a single one or a mixture of two or'more thereof, be present in the solution to an extent to exert their brightening eflect. preferably at least two milligrams per liter.

Some specific examples of compounds suitable for our purpose are as follows, being identified where possible by reference to Farbstofitabellen by Gustav Schultz, 7th edition, volume I (1931).

TABLE I l. Tetramethyl diamino acridine hydrochloride.

Schultz No. 902. An acridine dye, Rhodamine Orange, or Acridine Orange having the nucleus and carrying for methyl and two amino substituents.)

2. Dimethyl diamino acridine hydrochloride. 8. Diamino acridine hydrochloride.

Ar and Ar representing benzene nuclei.) 4. Diamino diphenazine.

Ar and Ar indicating benzene nuclei.) Safranine Y. Schultz 'No. 967. (A mixture of two dyes of the azine type, i. e. having the nucleus N Ar Ar) N ms-Phenyl diamlno diphenylazonium chloride.

(A compound of the formula ride. Oxazine nucleus.) 10. Diamino phenoxazine.

(H:N.Al' AI'NH:

Ar and Ar indicating benzene nuclei.)

-Lauths Violet, Diamino diphenazthionium chloride. Schultz No. 1036. (Thiazine nucleus.)

Methylene Blue. Schultz No. 1038. (Tetramethyl diamino diphenazthionium chloride.)

Methylene Green B. D. Schultz No. 1040.

(Tetramethyl diamino nitro diphenazthionium chloride. Thiazine nucleus.) Toluidine Blue. Schultz No. 1041. (Dimethylamino phenoamino tolazthionium chloride. Thiazine nucleus.)

Thionine Blue SO. Schultz No. 1042. (Trimethyl ethyl diamino diphenazthionium chloride. Thiazine nucleus.)

New Methylene Blue. Schultz No. 1043. (Diethyldiamino ditolazthionium chloride. Thiazine nucleus.)

Thiocarmine R. Schultz No. 1044. (Sodium salt of sulfonic acid of symmetric diethyl dibenzyl diamino diphenazthionium sulfonate; internal suli'onate.)

Brilliant Alizarine Blue G. A. Schultz No.

1048. (Dimethylamino dihydroxynaphthophenazthionium sulfonate and/or benzyl ethylamino dihydroxy naphtho phenazthionium sulfonate.)

While the quantity of these substances employed is not sharply critical, they are used in small amounts, that is, amounts of the order of 2 to 100 milligrams per liter of the bath, the upper limit being determined by their embrittling effect and in some cases, their solubility.

Most of the specific examples given in Table wherein Ar and Ar represent benzene nuclei, carrying at least one amino group on each benzene ring but not more than three amino groups on either benzene ring andtheir salts such as chloride, hydrochloride, acetate and sulfate are of outstanding value from the standpoint of control of the operation of the bath and are somewhat superior in respect to brightening effect to the more complex compounds. g The second class of materials, representative particular ones of which are employed in combination with one or more substances of the first class of compounds above identified, may be and for the purposes of this specification are designated as aromatic sultan-compounds. These materials are capable of cooperating with' the materials of the first class to produce nickel deposits having a high order of brightness accompanied by commercial ductility.

Particular examples which we have found to give excellent results are as follows:

TABLE II Alpha-naphthalene mono-sulfonate Beta-naphthalene mono-sulfonate Naphthalene disulfonates Naphthalene trisulfonates Sulfonated naphthalene o-Benzoic sulfimide (saccharin,.pre1erably as sodium salt) 7. Benzene sulfonamide 8. Benzene sulfohydroxamic acid 9. p-Toluene sulfonamide 10. o-Toluene sulfonamide "The above named addition agents of this second class, suitably in the form of the sodium or the nickel salt, may be used in various quantities upwards from 0.2 g./l., however, 5 g./l., or less is usually suificient concentration for best results. Larger quantities, within the limits of solubility, do no harm.

Specific Example 5 of Table II above is such as may be produced by reacting 2 parts of 20% oleum on one part of naphthalene at C. for two hours, neutralizing the resulting mixture with nickel carbonate. filtering and diluting to 26 B. Where quantities of sulfonated naphthalene" are referred to hereinafter, it is to be understood that the quantity specified represents roughly the nickel-naphthalene-mixed-sulfonate content of the mixture. Five cc. of the nickel neutralized reaction mixture is taken as equivalent .to one gram of nickel-naphthalene-mixed sulfonates. Other mixtures of compounds of the second class of materials also are satisfactory.

A conventional aqueous acid nickel bath in which the combined use of the two classe of addition agents will be found to give improved results, as above indicated, consists of NiSO4.6HaO' 120-450 grams per liter NiC12.6H2O 15-75 grams per liter HaBOa 15 grams per liter to saturation Sodium lauryl sulfate -1.0 grams per liter Current density Up to 60 amperes per sq .ft. pH... ...1.5-5.5 Temperature Room to 170 F.

referred to. the material Where this compound is M. E. Dry is sold under the trade name of Duponol to be understood. It is sold as the techjncal compound. Other equivalent surface tension reducing agents may be used instead of Duponol. Preparations known as Tergitol 7 and- Tergitol 08, sold by Carbide & Carbon Chemicals Co. and said to be sodium secondary alcohol sulfates. may be used instead of Duponol. The quantities required are of the same order.

Some heptahydrate is usually present. Where nickel sulfate is used herein in specific examples, this mixture of hydrates is to be understood.

In the above table giving the composition of a conventional bath, sodium lauryl sulfate is added for the purpose of reducing the surface tension in order to prevent pitting of the plate. The sulfates of normal primary aliphatic alcohols, having from 8 to 18 carbon atoms, are a class of compounds preferred for use for this purpose.

The following specific examples will serve to illustrate the invention:

EXAMPLEI Nickel sulfate grams 240 Nickel chloride do 37.5 Borac acid do 37.5 Mixture of ms-phenylditolazonium chloride and ms-o-tolylditolazonium chloride (Safranine Y) gram 0.01 o-Benzoic sulfimide (saccharin, sodium salt) grams 2.0 Sodium lauryl sulfate do 0.25

Water to make liter 1 pH 4. 0 Temperature C 50 Current density amp./sq. ft 40 EXAMPLE II Nickel sulfate; grams 240 Nickel chloride do.. 37. Boric acid do 37.5 Dimethylaminophenonaphthazoxonium chloride (Basic Navy Blue D cone.)

am" 0.030 Sulfonated naphthalene (nickel salt) grams 4.0

Water to make liter 1 pH 4.0 Temperature C 50 Current density amp./sq. ft. 40

' EXAMPLE III Nickel sulfate grams 240 Nickel chloride do 37.5 Boric acid do 37.5 Tetramethyldiaminodiphenazthionium chloride (Methylene Blue, extra, conc. do 0.025 Sulfonated naphthalene ,(nickel salt) do 5.0 Sodium lauryl sulfate do 0.25 Water to make liter 1 pH 3.3 Temperature C-.. 60 Current density -amp./sq. ft 50 EXAMPLE IV Nickel sulfate grams 240 Nickel chloride do 37.5 Boric acid do 37.5 5 Tetramethyldiaminonitrodiphenazthionium chloride (Methylene 'Green BD) do 0.025

"Sulfonated naphthalene (nickel salt do 4.0

Water to make liter 1 pH 4.0 Temperature L C 50 Current density amp./sq, ft 40 5 ExAMrLaV Nickel sulfate grams 240 Nickel chloride do 37.5 Boric acid do 37.5 Rhodamine Orange (or Acridine Orange,

20 Schultz #902) milligrams Sulfonated naphthalene" cc 5 Water to make liter 1 pH 3.5 Current density amp./sq. ft 40 25 EXAMPLE VI Nickel sulfate grams 240 Nickel chloride do 37.5 Boric acid do 37.5

Nigrosine (Schultz #986) milligrams 100 Sulfonated naphthalene cc 20 Sodium lauryl sulfate gram 0.25 Water to make liter 1 pH 3.0

Temperature C 60 Current density amp./sq. ft 50 EXAMPLE VII Nickel sulfate grams 240 40 Nickel chloride do 37,5 Boric acid -4 do 37.5 Induline R (Schultz #984) milligrams 25 Sulfonated naphthalene cc 5 Sodium lauryl sulfate gram 0.25

Water to make liter 1 pH 3.5 Temperature C 45 Current density amp./sq. ft 40 EXAMPLE VIII Nickel sulfate grams 240 Nickel chloride do 37.5 Boric acid do 37.5 Lauths Violet (Schultz #1036) milligrams 25 Sulfonated naphthalene" cc 3 saccharine (soluble, soda salt) gram 0.5 Sodium lauryl sulfate do .25 Water to make liter 1 Temperature C 60 Current density amp./sq. ft 40 This application is a continuation-in-part of our co-pending application, Serial No. 217,774, filed July 6, 1938, now Patent No. 2,238,861. This application is also a continuation-in-part of our co-pending applications, Serial Nos. 309,232 and 309,233 filed December 14, 1939, now Patents No, 2,198,267 and No. 2,198,268, respectively, which were in turn continuations-in-part respectively of our applications, Serial Nos. 200,120 and 200,121, filed April 5, 1938.

Having thus described our invention, what we claim is:

1. An electroplating bath comprising an aqueous, acid solution of a nickel electrolyte of the where a: is selected from the group consisting of N, 0,8 and O, and which are soluble in the bath to the extent of at least one milligram per liter and mixtures of such compounds, and the other of said addition agents being selected from the class consisting of naphthalene sulfonates, the

single ring aryl sulfonamides and single ring aryl sulfimides and mixtures thereof present in solution in the bath to the extent of at least 0.2 gram per liter. Y

2. An electroplating bath comprising an aqueous, acid solution of a nickel electrolyte of the class consisting of nickel sulfate and nickel chloride, said solution having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being maintained in solution in the bath in quantity from 2 to 100 milligrams per liter and being selected from the group of compounds containing the grouping I where a: is selected from the group consisting of N, C, S and 0, having requisite solubility to permit such concentration and mixtures of such compounds, and the other of said addition agents being selected from the group consisting of naphthalene sulfonates, the single ring aryl sulfonamides and single ring aryl sulfimides and mixtures thereof present in solution in the bath to the extent of at least 0.2 gram per liter.

3. An electroplating bath as defined in claim 2 further characterized in that said first mentioned addition agent comprises a. compound having at least one amino group connected to ring carbon.

4. An electroplating bath as defined in claim 2 further characterized in that said first men?" tioned addition agent is an azine compound havingba't least one amino group connected to ring car 11.

5. An electroplating bath as defined in claim 2 further characterized in that said first mentioned addition agent is diamino diphenazine.

6. An electrodeposition bath as defined in claim 2 further characterized in that said first mentioned addition agent is diamino acridine hydrochloride.

. 7. An electrodeposition bath as defined in claim 2 further characterized in that said first mentioned addition agent is Iauths Violet.

8. An electroplating bath comprising an aqueous, acid solution containing nickel sulfate and nickel chloride, said solution having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents,'one of said addition agents being maintained in solution in the bath in quantity from 2 to 100 milligrams per liter and being selected from the group of compounds containing the grouping 1 Ar Ar' where :c is selected from the group consisting of N, C, S and 0, having requisite solubility to permit such concentration and mixtures of such compounds, and the other of said addition agents being selected from the group consisting of naphthalene sulfonates, the single ring aryl sulfonamides and single ring aryl sulfimides and mixtures thereof present in solution in the bath to the extent of at least 0.2 gram per liter.

9. An electroplating bath as defined in claim 8 further characterized in that said first mentioned additionagent comprises a compound having at least one amino group connected to ring carbon.

10. An electroplating bath as defined in claim 8 further characterized in that said first mentioned addition agent. is diamino diphenazine.

11. An electrodeposition bath as defined in claim 8 further characterized in that said first mentioned addition agent is diamino acridine hydrochloride.

12. An electrodeposition bath as defined in claim 8 further characterized in that said first mentioned addition agent is Lauths Violet.

13. The electroplating bath as defined in claim 1 wherein the second mentioned addition agent is an ortho benzoic sulfimide (saccharine, soluble saccharine).

14. The electroplating bath as defined in claim 8 wherein the second mentioned addition agent is an ortho benzoic sulfimide (saccharine, soluble saccharine).

'15. An electroplating bath as defined in claim 2 further characterized in that said first men-,- tioned addition agent is diamino diphenazine and said second mentioned addition agent is an ortho .16. An electroplating bath as defined in claim 2 further characterized in that said first mentioned addition agent is diamino acridine hydrochloride and said second mentioned addition agent is an ortho benzoic sulfimide.