US3677913A - Nickel plating - Google Patents

Abstract

THE NOVEL PROCESS OF THIS INVENTION FOR ELECTROPLATING A SEMI-BRIGHT SUFLUR-FREE, NICKEL PLATE ONTO A BASIS METAL COMPRISING PASSING FROM AN ANODE TO A BASIS METAL CATHODE THROUGH AN AQUEOUS ACIDIC NICKEL PLATING SOLUTION CONTAINING AT LEAST ONE NICKEL COMPOUND PROVIDING NICKEL IONS FOR ELECTROPLATING OF NICKEL, AND INCLUDING AS COOPERATING SEMI-BRIGHT ADDITIVES: (A) THE ALIPHATIC ACETYLENIC COMPOUND 3-HEXYNE-2,5-DIOL, AND (B) A COMPOUND CONTAINING AN OXYAMEGASULFOHYDROCARBON-DI-YL COUMARIN ANION WHEREIN THE HYDROCARBON-DI-YL MOIETY CONTAINS AT LEAST TWO CARBON ATOMS AND WHEREIN THE OXYOMEGASULFOHYDROCARBON-DI-YL GROUP IS SUBSTITUTED ON THE CARBOCYLIC NUCLEUS OF THE COUMARIN GROUP.

Description

United States Patent 3,677,913 NICKEL PLATING Frank Passal, Detroit, Mich., assignor to M & '1 Chemicals, Inc., Greenwich, Conn. No Drawing. Filed Apr. 1, 1971, Ser. No. 130,479 Int. Cl. C23b 5/08, 5/46 US. Cl. 204-49 12 Claims ABSTRACT OF THE DISCLOSURE The novel process of this invention for electroplating a semi-bright sulfur-free, nickel plate onto a basis metal comprising passing current from an anode to a basis metal cathode through an aqueous acidic nickel plating solution containing at least one nickel compound providing nickel ions for electroplating of nickel, and including as cooperating semi-bright additives: (a) the aliphatic acetylenic compound 3-hexyne-2,5-diol, and (b) a compound containing an oxyomegasulfohydrocarbon-di-yl coumarin anion wherein the hydrocarbon di yl moiety contains at least two carbon atoms and wherein the oxyomegasulfohydrocarbon-di-yl group is substituted on the carbocyclic nucleus of the coumarin group.

This invention relates to the electroplating of a semibright nickel characterized by its fine grain, uniformity, ductility, freedom from sulfur, and by its high leveling ability.

When it is desired to produce a nickel surface possessing maximum brightness and luster and/or when the surface of the basis metal may possess numerous scratches or other minor imperfections, it is common to electroplate onto the surface a first layer of nickel particularly characterized by its leveling ability. This deposit is called a semi-bright nickel deposit because it does not posses the extremely high brilliance and luster commonly attained by a bright-nickel deposit. There may commonly be deposited onto this first semi-bright nickel layer a second bright nickel layer. The semi-bright nickel layer may for certain applications be polished and buffed prior to deposition of the bright nickel layer. The resulting duplex-nickel system is characterized by high degree of brilliance and by superior resistance to corrosion, even when the bright nickel deposit is relatively thin.

The first or semi-bright layer of nickel has heretofore commonly been deposited from various nickel-plating baths, including for example Watts baths, sulfamate baths, chloride-free baths, etc. which contain an additive or a combination of additives. One of such additives commonly used in prior art semi-bright nickel plating baths has been coumarin. Although it may be possible to produce a semi-bright nickel deposit by prior art methods, there are numerous defects which render these processes less than fully satisfactory. Semi-bright nickel deposits formed from some plating baths of the prior art also may sufier from inadequate leveling, high tensile stress, and non-uniform grain size.

In an effort to correct these deficiencies of semi-bright nickel plating baths, various combinations of additives have been used some of which have been coumarin derivatives having various groups attached to the aromatic or to the heterocyclic ring. These compounds, however, have been found not to be satisfactory in that they do not 3,677,913 Patented July 18, 1972 permit attainment of an improved semi-bright nickel plate, but rather they have suffered from defects such as very low solubility, difficulty of synthesis, and tendency to readily decompose during electrolysis to give undesirable products, typically resinous or polymeric materials which result in inferior deposits, unsatisfactory degrees of leveling and narrow ranges of leveling current density.

It is an object of this invention to provide a combination of additives that increase the luster, leveling, and the width of the leveling current density range to increase the uniformity of deposits and grain size and at the same time maintaining ductility and without creating internal stresses in the electroplating of semi-bright nickel. Other objects will be apparent to those skilled in the art on inspection of the following description.

The novel process of this invention for electroplating a semi-bright, sulfur-free, nickel plate onto a basis metal comprises passing current from an anode to a basis metal cathode through an aqueous acidic nickel plating solution containing: at least one nickel compound providing nickel ions for electroplating of nickel and as cooperating semibright additives: (a) the aliphatic acetylenic compound 3-hexyne-2,5-diol and (b) a compound containing an oxyomegasulfohydrocarbon-di-yl coumarin anion wherein the hydrocarbon-di-yl moiety contains at least two carbon atoms and the oxyomegasulfohydrocarbon-di-yl group is substituted on the carbocyclic nucleus of the coumarin group.

Practice of this invention results in a high degree of leveling and a high width of current density range to give optimum results in the plating of ferrous basis materials and rigid articles such as automobile bumpers. The novel combination of cooperating additives of this invention also eliminates the problem of maintaining low current density deposits sufiiciently lustrous and fine grained to provide sufiicient build-up of brightness in the low current density areas. All nickel plating bath in a commercial operation accumulate metallic (zinc, copper, etc.) and organic impurities (which may include decomposition products of the coumarin derivatives). The cooperating additives of the invention reduce and minimize deleterious effects of such impurities. For example, if some of the organic impurities tend to give coarser-grained, duller low current density deposits, the cooperating additives tend to counter-act these effects.

The basis metal onto which the semi-bright deposits of this bath may be applied may include basis metals which are characterized by a low degree of luster or brightness or which possess a degree of surface roughness which would fail to permit attainment of a satisfactory quality of final finish and appearance if they were directly plated with a bright nickel plate. Typically the basis metals may include ferrous metals such as steel; copper, including its alloys such as brass, bronze, etc.; zinc, particularly in the form of die castings which may bear a plate of copper, etc.

The novel baths of this invention may typically include Watts-type baths, sulfamate-type baths, fluoboratetype baths, chloride-free sulfalte baths, chloride-free sulfamate baths, etc.

A typical Watts bath which ma be used in practice of this invention may include the following components in aqueous solution, all values being in grams per liter (g./l.) except for the pH.

A typical sulfamate-type bath which may be used in practice of this invention may include the following components:

TABLE II Min- Max- Pre- Component imum irnum ferred Nickel sulfamate 330 400 375 Nickel chloride 15 6O 45 Boric acid 35 55 45 pH electrometric 3 5 4. 0

A typical fluoborate-type bath which may be used in the practice of the invention may include the following components:

TABLE I11 Min- Max- Pre- Compcnent inunn lmmn ferred Nickel fluoborate 250 400 300 Nickel chloride 45 60 50 Boric acid 15 30 30 pH electrometrlc 2 4 3. 0

A typical chloride-free sulfamate-type bath which may be used in practice of this invention may include the following components:

TABLE IV Min- Max- Pre- Component imum imum fened Nickel sulfate- 300 500 400 Boric acid 55 45 pH electrornetric 3 5 4. 0

A typical chloride-free sulfate-type bath which may be used in practice of this invention may include the following components: I

TABLE V Min- Max- Pre- Component imnrn imum ierred Nickel sulfamate 300 400 350 Boric acid 35 55 45 pH electrometric 3 5 4. 0

In the above bath compositions nickel sulfate is present as NiSO -7H O and nickel chloride as NiCl -6H O; all other compounds are given as their anhydrous form.

It will be apparent that the above baths may contain compounds in amounts falling outside the preferred minima and maxima set forth, but most satisfactory and economical operation may normally be effected when the compounds are present in the baths in the amounts indicated. A partciular advantage of the chloride-free baths of Tables 1V and V, supra, is that they may be used for high speed plating with insoluble anodes, such as lead, or with soluble anodes having low polarization tendency, such as SD nickel, to avoid the possible evolution of toxic chlorine gas at the anode.

Only an amount of cooperating additive sufiicient to provide improved plating characteristics for the nickel plating solution containing at least one nickel compound providing nickel ions for electroplating nickel is necessary. The amount of the first cooperating additive, the aliphatic acetylenic compound 3hexyne-2.5-diol, presem; in the nickel plating solution shown be from 0.1 gram per liter to 1.0 gram per liter, preferably from 0.2 gram per liter to 0.8 gram per liter. The concentration of the second cooperating additive, a compound containing the oxyomegasulfohydroearbon-di-yl group present in the nickel plating solution should be from 0.2 gram per liter to 1.0 gram per liter, preferably from 0.4 gram per liter to 0.8 gram per liter.

The second cooperating semi-bright additive employed in practice of this invention comprises compounds containing the oxyomegasulfohydrocarbon-di-yl coumarin anion wherein the hydrocarbon moiety contains at least two carbon atoms. The oxyomegasulfohydr'ocarbon-di-yl group is substituted on the carbocyclic ring of the coumarin nucleus. The hydrocarbon-di-yl moiety may bear inert substituents. Typically such compounds include those wherein the cation M (see infra) may be a bath-compatible cation, i.e. a cation which is soluble in the electroplating bath and which does not interfere with attainment of the desired semi-bright plate. Typically, the cation M includes hydrogen and alkali metals including sodium, potassium, lithium, etc.; polyvalent metals such as nickel, cobalt, magnesium, etc. The omega carbon atom of these novel compounds is the carbon atom linking the sulfo group to the remainder of the molecule. Most commonly the omega position is the carbon atom most distant from the coumarin nucleus. However, when a hydrocarbon-diy1 group in the chain linking the coumarin nucleus to the sulfo group contains carbon-containing substituents, the omega position as herein defined may not be the carbon atom most distant from the coumarin nucleus.

The cooperating acetylenie additive used in cooperation with the coumarin derivatives, besides increasing the general deposit luster and uniformity and acting as a low current density coverage and luster promoter, also acts as an extender and markedly improves leveling.

The compounds containing the oxyomegasulfohydrocarbon-di-yl coumarin anion typically have the following formula:

HJII-O-SOa-R-OL, (I)

wherein a, b, c and d are each integers less than two, i.e. 0 and 1, the sum of a, b, c and at being greater than 0 and preferably 1 and wherein M is a cation as defined supra, R is a hydrocarbon-di-yl group wherein the hydrocarbon moiety contains at least two carbon atoms, and X is an inert substituent. Typically inert substituents (i.e. substituents which do not cause unfavorable efiects to occur in electroplating baths including the novel compounds of this invention), include hydrogen; halogen, e.g. chloro; alkyl, alkaryl, aralkyl, aryl, alkoxy, aryloxy, etc. As shown, the inert substituent when present is preferably on the aromatic ring of the coumarin nucleus.

In the above formula R may be a divalent hydrocarbon group having at least two carbon atoms. Typically R may be arylene such as o-phenylene, m-phenylene, pphenylene; aralkylene such as o-benzyl, m-benzyl or pbenzyl; alkarylene such as l-methyl-2,3-phenylene, 1- methyl-2,4-phenylene, l-methyl 2,5 phenylene, etc.; alkylene such as ethane-1,2-di-yl, propane-1,2-di-yl, propane-1,3-di-yl, butane-1,4-di-yl, bntane-l,3di-yl, pentane- 1,5-di-yl, etc. These groups may bear inert substituents including hydrocarbon substituents. The preferred R group may contain at least three carbon atoms, and more preferably 3-5 carbon atoms in a straight chain extending from the carbon atom closest to the coumarin nucleus to the omega carbon atom, the omega position being as hereinbefore defined. Preferred R groups may contain a linked 5 chain of methylene groups and the most preferred R may be propane-1,3-di-yl, CH CH CH In formulae containing a plurality of R groups, the R groups may preferably be the same.

With respect to Formula I supra, it will be apparent that when a is 1, b is 1, c is 0, and d is the formula is:

M-OS OPE- 0 (II) and that when a is O, b is 1, c is l, and d is 0 the formula may be:

(III) and that when a is 0, b is l, c is 0, and d is 0 the formula may be:

It will be apparent that the values of a, b, c, and d may be independently varied between 0 and 1 to produce coumarin derivatives other than those specifically set forth.

It will also be apparent that when M is polyvalent, the valences thereof may be satisfied by linkage to other oxyomegasulfohydrocarbon-di-yl groups which may be on the same or on another coumarin nucleus.

The preferred compounds include those wherein the oxyomegasulfohydrocarbon-di-yl group is substituted on the 7-position of the coumarin and M is an alkali metal; also preferred are those compounds wherein R is a hydrocarbon-di-yl group having 3-5 carbon atoms and most preferably one wherein R is a polymethylene chain preferably having 3 carbon atoms. Typical preferred specific compounds which may be used in practice of this invention include:

TABLE VI potassium 7-oxyomegasulfopropyl coumarin potassium 6-chloro-7-oxyomegasulfopropyl coumarin sodium 7-oxyomegasulfopropyl coumarin sodium 6-chloro-7-oxyomegasulfopropyl coumarin disodium 6,7-di(oxyomegasulfopropyl) coumarin disodium 7,8-di(oxyomegasulfopropyl) coumarin nickel 6,7-di(oxyomegasulfopropyl) coumarin cobalt 7,8-di(oxyornegasulfopropyl) coumarin nickel di(7,7'-oxyomegasulfopropyl) coumarin potassium 8-oxyomegasulfopropyl coumarin potassium 6-oxyomegasulfopropyl coumarin sodium -oxyomegasulfobutyl coumarin potassium 7-oxyomegasulfobutyl coumarin sodium 7-0xyomegasulfobenzyl coumarin (i.e., sodium 7-oxy-ortho sulfobenzyl coumarin), viz:

The 'most preferred compounds may typically be the first four compounds in Table IV. It will be apparent that other cations as hereinbefore noted may replace those present in the specific compounds in Table VI.

The oxyornegasulfohydrocarbon-di-yl coumarin compounds of this invention, wherein the hydrocarbon-di-yl moiety contains at least 2 carbon atoms and the oxyomegasulfohydrocanbon-di-yl is substituted on the carbocyclic nucleus of the coumarin group, may be prepared by the process which comprises mixing in a solvent dispersion, a hydroxy coumarin wherein the hydroxy group is substituted on the carbocyclic nucleus of the coumarin group, a compound of the formula MOH wherein M is a cation including those hereinbefore noted, and a hydrocarbon sultone wherein the hydrocarbon moiety contains at least 2 carbon atoms thereby forming a reaction mixture, and heating said reaction mixture.

The solvents used in this preparation may preferably be those in which the reactants are dispersible, i.e. suspendable or soluble and most preferably one in which the compound MOH is soluble. Such solvents may typically include organic solvents such as alcohols, etc.

The sultones which may be employed to prepare the novel compounds of this invention may include those containing a carbon-oxygen-sulfur-carbon linkage in a ring, the hexavalent sulfur atom being further bonded to two additional oxygen atoms. The sultone which may preferably 'be used may contain 3-5 carbon atoms, these sultones being characterized by generation of a minimum of foaming. The most preferred sultone may be 1,3-propane sultone,

although sultone such as 1,4-butane sultone,

and 1,3-butane sultone,

also may produce highly useful additives. The longer chain alkane sultones or other sultones containing more than 5 carbon atoms, such as tolyl sultone,

may also be used to produce additives within the scope of the invention.

Hydroxy-coumarins which may be used in preparing the novel compounds may include the following hydroxy coumarins which carry one hydroxyl substituent on the carbocyclic nucleus of coumarin, typically including monoand poly-hydroxy coumarins such as:

S-hydroxy coumarin 6-hydroxy coumarin 7-hydroxy coumarin 8-hydroxy coumarin 6,7-dihydroxy coumarin 7,8-dihydroxy coumarin 6-chloro-7-hydroxy coumarin Preferred coumarins may include the 7-hydroxy coumarins such as 7-hydroxy coumarin, per se.

These hydroxy coumarins may be readily available or may be prepared by the reaction of the corresponding resorcinol with malic acid in the presence of catalyst, e.g. concentrated sulfuric acid, e.g. to prepare 6-chlor0 7-hydroxy coumarin, malic acid may be reacted with 4-chloro resorcinol. Besides concentrated sulfuric acid other catalysts may be used such as the pyrophosphates of titanium and zirconium used singly or in combination.

The preferred compounds MOH which may be used in the process of this invention include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide.

In a preferred embodiment of the invention, 2.3-3.3 parts, say 2.8 parts of MOH, preferably potassium hydroxide, may be added to 3-4 moles, say 3.1 moles of solvent, preferably methanol. 7541 parts, preferably 8.1 parts of 5-, 6-, 7- or S-hydroxy coumarin, preferably 7- hydroxy coumarin, may then be added together with 4.9- 7.3 parts, say 6.7 parts of hydrocarbon sultone, preferably 1,3-propane sultone. Preferably the molar ratio of MOH to hydrocarbon sultone may be about 1 to 1.. The reaction mixture may then preferably be heated typically to reflux temperature for 1-4 hours, say 2 hours. All parts referred to above are parts by weight.

At the conclusion of the reaction time the reaction vessel may be cooled and the desired product may precipitate. The product may be separated, washed with a solvent in which the product is sparingly soluble, such as methanol, and dried. Typically the pure yield may be at least about 60% by weight based on the coumarin starting material, although crude yield may also be used as semi-bright additives to electroplating baths without deleterious results. Alternatively, the solvent, such as methanol, may be removed by heating under reduced pressure and the residual product dissolved in water to a convenient concentration and used as the additive stock solution to essentially obtain a quantitative yield of the active ingredient.

If it be desired to convert the alkali metal salt of the oxyomegasulfohydrocarbon-di-yl coumarin to other salts, the alkali metal salt of the oxyomegasulfohydrocarbondi-yl coumarin compound may preferably be reacted with a cationic exchange resin such as a sulfonic acid cationic exchange resin on the hydrogen cycle. The free sulfonic acid in the eluate may then be reacted with the oxide, hydroxide, carbonate, etc., of the metal desired, e.g. nickel or cobalt to neutrality to form the desired metal salt of the free sulfonic acid. Any excess of the oxide, hydroxide, carbonate, etc., may be removed by filtration.

The semi-bright oxyomegasulfohydrocarbon-di-yl coumarin moiety wherein the hydrocarbon-di-yl moiety contains at least two carbon atoms and wherein the oxyomegasulfohydrocarbon-di-yl group is substituted on the carbocycl-ic nucleus of the coumarin group may preferably be used in nickel plating baths such as those of Table I-V. in amounts of at least 0.2 g./l. of plating bath. Lower concentrations may give appreciable grain refinement but the deposits may be less glossy. When the concentration of the oxyomegasulfohydrocarbon-di-yl compound or group exceeds 3 g./l. of plating bath, the results obtained generally do not provide additional advantages over the lower ranges. The preferred concentration ranges from about 0.51 g./l. of additive in the plating bath.

The presence of the cooperating additive 3-hexyneand low foaming anionic wetting agents such as sodium dialkyl sulfosuccinates may be used with air agitation. Although these wetting agents may commonly contain sulfur, it has unexpectedly been found that no increase in the sulfur content of the nickel deposits may be observed when these wetting agents are used with the semibright cooperating additives of the invention. The use of formaldehyde as an auxiliary additive is usually not necessary but it may be used if desired and is compatible with the other cooperating additives.

It is a particular feature of this invention that medium or very high-speed electroplating of semi-bright nickel may be eifected by the process comprising passing current from a substantially non-polarizing anode to a basis metal cathode through an aqueous nickel plating solution including at least one nickel compound capable of providing nickel ions for electroplating nickel and as a first cooperating semi-bright additive 3-hexyne-2,5-diol and as a second semi-bright additive a compound containing oxyomegasulfohydrocarbon-di-yl coumarin anion wherein the hydrocarbon moiety contains at least two carbon atoms and the oxyomegasulfohydrocarbon-di-yl group is substituted on the carbocyclic nucleus of the coumarin group, maintaining the cathode current density during said plating at a level of at least 10 amperes per square decimeter (ASD), and maintaining a high relative velocity between said nickel plating solution and said basis metal cathode thereby obtaining a glossy, leveled, semi-bright high-speed nickel plate with good low current density coverage and good ductility.

Semi-bright nickel plating in accordance with this invention may also be carried out under lower speed conditions by immersing a basis metal cathode into a nickel plating bath as hereinbefore disclosed. The anode may be either a soluble anode, typically nickel metal, or an insoluble anode, typically lead.

If nickel is used as the anode, it is preferably SD type of nickel and plating may be carried out in chloride-containing baths for 30-60 minutes, say 30 minutes at 40-60 C., say 50 C., with mechanical or air agitation.

The current density may typically be 2.5-5 a.s.d., preferably 5 a.s.d.

The novel process of this invention may permit attainment of a 12.5 to 50 microns, says 25 microns of semi bright nickel plate characterized by its fine grain, high ductility, high gloss, uniform appearance, high leveling, and high covering power. The plate is also characterized by its essentially sulfur-free character.

The following examples illustrate the beneficial efiects of the cooperating additives comprising the aliphatic acetylenic compound 3-hexyne-2,5-diol and compounds containing an omegasulfohydrocarbon-di-yl coumarin anion.

EXAMPLE 1 Nickel sulfate 300 g./1.

Nickel chloride 60 g./l. Boric acid 45 g./l. pH

4.0 electrometric.

To the above bath there was added the equivalent of 0.4 g./l. of potassium oxyomegasulfopropyl coumarin plus 0.1 g./l. formaldehyde plus 0.25 g./l. sodium d-nhexyl sulfosuccinate and a Hull Cell test was run under the following conditions:

Solution volume 267 ml.

Agitation n Magnetic stirring. Anode Electrolytic nickel. Cathode Polished brass panel on which there was inscribed a single 1.25 cm. wide horizontal band of 4/0 grit emery scratches about 2.54 cm. from bottom edge of panel.

Temperature 50 C. Current 2 amperes. Time minutes.

After plating, the panel was water-rinsed, dried and examined. The high current density end from about 7 to 12 a.s.d. showed a slightly milky well-leveled deposit. From about 1 to 7 a.s.d. the deposit had only fair leveling and the luster was also only fair with some tendency toward a yellowish smeary haze. Below about one a.s.d. the deposit was lustrous. The deposit ductility was excellent.

EXAMPLE 2 EXAMPLE 3 Using the bath composition of Example 2 a 4-liter life test was run using the following conditions:

Plating cell-5 liter rectangular cross-section (13 cm. x 15 cm.) made of Pyrex.

Solution volume-4 liters to give a solution depth, in

absence of anode, of about 20.5 cm.

Temperature-45 C. (maintained by immersing cell in a thermostatically controlled water bath).

Agitation--filtered air through a glass and polyethylene s ider.

An desingle bagged titanium basket containing SD nickel squares.

Cathode-brass strip (2.54 cm. x 20.3 cm. X 0.071 cm.) buffed and polished on one side and immersed to a depth of about 17.8 cm.-horizonta1 bend 2.54 cm. from bottom and the next 2.54 cm. bent to give an internal angle on the polished side of cathode of about 45polished side facing anode at an approximate distance of 10.2 cm. and scribed vertically in center with a 1 cm. wide band of a single pass of 2/0 grit emery paper scratches.

Cell current5.0 amperes.

Time-solution electrolyzed about 7 hours per dayoccasional cathodes plated for 30 minutes to evaluate deposit leveling, uniformity, ductility, luster (overall and in low current density recessed area).

Filtrationbatch, about every 200 ampere hours of total electrolysis.

Additions-the pH was periodically adjusted when necessary with dilute sulfuric acid to within a range of 3.8 to 4.2 electrometric; periodic additions of the coumarin derivatives and 3-hexyne-2,5-diol were made to maintain deposit luster, ductility and leveling.

10 Electrolysis was continued for a total of about 400 ampere hours during which time the following amounts of additives were consumed:

Grams Potassium oxyomegasulfopropyl coumarin 13.6 3-hexyne-2,5-diol 13.2

The life test started excellently and highly ductile, very uniformly glossy, well-leveled deposits were obtained having practically zero internal stress (as observed by lack of any tendency for the originally perpendicularly positioned cathode to bend toward the anode). During the course of the life test the quality of the deposits was easily maintained. The most remarkable and striking observation was that not a single deposit plated showed any dullness, dull bands, or low current density dullness, all of which are normally obtained with the coumarin derivative and formaldehyde as the cooperating additives unless careful and periodic additions of the latter two additives are made very frequently. In other words, the 3- hexyne-2,5-diol permitted more consistent operational characteristics, i.e. it provided a basic grain refinement and luster development which made possible wider fluctuations in the coumarin derivative content without sacrificing the quality of deposit.

At the end of 400 ampere hours of operation, corresponding to a commercial operation of 50 days, assuming the use of 1 ampere per 4 liters per 8 hour day, there was no indication of having reached a level of additive degradation product accumulation which would necessitate a purification treatment. In addition, at the end of 400 ampere hours of operation the low current density recesses were lustrous and the deposit levelling, ductility and uniformity were excellent.

Although this invention has been illustrated by reference to specific examples, numerous changes and modifications thereof which clearly fall within the scope of the invention will be apparent to those skilled in the art.

I claim:

1. A process of electroplating a semi-bright sulfurfree, nickel plate onto a basis metal which comprises passing current from an anode to a basis metal cathode through an aqueous acidic nickel plating solution containing at least one nickel compound providing nickel ions for electroplating nickel; and, in an amount suflicient to provide improved plating characteristics, as a first cooperating semi-bright additive the aliphatic acetylenic compound 3-hexyne-2,5-diol and as a second semi-bright additive a compound containing an omegasulfohydrocarbon-di-yl coumarin anion wherein the hydrocarbon-di-yl moiety contains at least two carbon atoms and wherein the oxyomegasulfohydrocarbon-di-yl groups are substituted on the carbocyclic nucleus of the coumarin group.

2. The process of claim 1 wherein said second semibright additive is Xid[MO-SO2R-O]d X1-e[Mo SOl R -O] X ,[M0S0aR-O] \O/0 X ,[MOS0gR0].. wherein X is an inert substituent, M is a cation, R is a hytdrocarbon-di-yl group containing at least two carbon atoms, and a, b, c, and d are each integers less than 2, the sum of a, b, c, and d being at least 1.

3. The process of claim 1 wherein said second semibright additive is 1 1 wherein M is a cation and X is an inert substituent.

4. The process of claim 1 wherein said first semi-bright additive is present to the extent of at least about 0.1 g./ I; of the solution and the cooperating second semi-bright additive is present to the extent of 0.14.0 g./1. of the solution.

5. A process of electroplating a semi-bright nickel deposit which comprises passing current from a substantially non-polarizing anode to a basis metal cathode through a chloride-free aqueous acidic nickel plating solution including at least one metal compound capable of providing nickel ion for electroplating nickel; and, in an amount sufiicient to provide improved plating characteristics, as a first cooperating semibright additive the aliphatic acetylenic compound 3-hexyne-2,S-diol andas a second semi-bright additive a compound containing oXyomegasulfohydrocarbon-di-yl coumarin wherein the hydrocarbon moiety contains at least two carbon atoms and the oxyomegasulfohydrocarbon-di-yl group is substituted on the carbocyclic nucleus of the coumarin group; maintaining the cathode current density during said plating at at level of at least ten amperes per square decimeter, and maintaining a high relative velocity between said chloridefree nickel plating solution and said basis metal cathode thereby obtaining a glossy leveled, semibright high speed nickel plate characterized by good low current density coverage and good ductility.

6. A nickel plating solution comprising an acidic aqueous nickel plating solution including: at least one nickel compound capable of providing nickel ions for electrodeposition of nickel on a basis metal cathode; and in an amount sufficient to provide improved plating characteristics as a first cooperating semi-bright additive the aliphatic acetylenic compound 3-hexyne-2,5-diol and as a second cooperating semi-bright additive a compound containing an oxyomegasulfohydrocarbon-di-yl coumarin ion wherein the hydrocarbon moiety contains at least two atoms and the oxyomegasulfohydrocarbon-di-yl group is substituted on the carbocyclic nucleus of the coumarin group.

7. The nickel plating solution of claim 6 wherein the semi-bright additive is 12 wherein X is an inert ,substituent, M is a cation, R is a hydrocarbon di-yl group containing atflea'st two carbon atoms, and a, b, c, and d are each integerslessthan 2, the sum of a, b, c, and ,dbeing at least 1. V 8. The nickel platingsolution of claim '6 wherein 'said semi-bright additive'isf i wherein M is a cation and X is an inert substituent. 9. The nickel plating solution of claim 6 wherein said semi-bright additive is wherein M is a cation.

10; The nickel plating Solutibil of claim 5' wherein said semi-bright additive is nearen-ces caea UNITED STATES PATENTS I p 3,367,854 2/ 1968 Passal 204 49 3,556,959" 1/1971 1 Passal I. 204-49 GERALD L. KAPLAN; Primary Examiner