US3152972A

US3152972A - Electrodeposition of lustrous satin nickel

Info

Publication number: US3152972A
Application number: US45286A
Authority: US
Inventors: Brown Henry; Thaddeus W Tomaszewski
Original assignee: Udylite Corp
Current assignee: Occidental Chemical Corp; Udylite Corp
Priority date: 1960-07-26
Filing date: 1960-07-26
Publication date: 1964-10-13
Anticipated expiration: 1981-10-13
Also published as: NL267501A; NL267502A; NL125957C; FR1299814A; NL267500A; GB936172A; US3152973A; DE1248413B; US3152971A; SE301742B; SE307713B; SE307714B; NL125956C; NL125958C

Description

aluminum silicate.

United States Patent 3,152,972 ELECTRDDEPGSETIQN 0F LUSTROUS SATIN NICKEL Henry Brown, Huntington Woods, and Thaddeus W.

This invention relates to the electrodeposition of nickel v with a satin-like appearance directly from aqueous acidic nickel baths. More particularly this invention provides a method for obtaining a fine-grained lustrous satin nickel plate of exceptional corrosion resistance directly from the plating bath.

Satin or brushed finished nickel or chromium plate is normally more expensive than the bright nickel finishes which are obtained with high-leveling, bright nickel plating which require no further polishing or buffing. To obtain the most pleasing satin finishes, dull nickel or dull chromium plate is most often employed, and is subsequently brush finished to obtain the, satin lustre. This latter step is expensive, and also decreases the corrosion protecting afforded by the satin plate because the brush marks or polishing scratches penetrate appreciably in the plate especially in recessed areas where the plate is thin. For these reasons, that is, expense, and decreased corrosion resistance, satin finished nickel or chromium are not usually used for exterior parts of automobiles or boats.

It is an object of this invention to provide plating baths and methods to produce fine-grained lustrous satin nickel directly from the bath that not only has a very pleasing appearance, but which can be high-lighted by bufiing raised areas to give beautiful two-tone effects, and which will also provide exceptionally good corrosion protection to the basis metal such as ferrous, aluminum, magnesium, brass, copper and zinc articles.

It has now been found that nickel plating baths normally designated as bright nickel baths, or semi-bright nickel baths can be modified to plate a fine-grained lustrous satin nickel deposit, by incorporating in these baths certain quantities or concentrations of certain finely divided bath insoluble compounds, and plating while these powdered materials are maintained in agitation in these baths. The method of the invention also includes the step of removing from the plated surface any excess powdery material clinging to the plate prior to additional treating steps, such as the preferred final step of chromium plating.

The class of fine powders which when added to agitated bright nickel or semi-bright nickel plating baths in concentrations from 10 to 500 grams per liter Produce a pleasing fine-grained lustrous satin nickel directly from the bath, is the bath insoluble silicates of aluminum, magnesium, boron, calcium, strontium and barium, and the mixed silicates of these metals such as barium aluminosilicate, and including the insoluble silicates containing alkali metals. Of these silicates especially outstanding is finely powdered kaolin (china clay), which is a hydrous Finely powdered glass (soft glass, Pyrex, a borosilicate, etc.) is also very good providing most of the particles are less than 5 microns in diameter,

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roughness especially on shelf areas and are not desirable for the purposes of this invention. It is important that the powders are clean and wetted by the aqueous bath. For example, some commercial grades of tale (a hydrous magnesium silicate) must be washed first with alcohol or acetone or both before they can be readily wetted by the bath.

in general, the fine powders must be less than 5 microns in diameter and preferably less than 2 microns diameter, with the best results being obtained with 0.02 to 0.5 micron particle size. If the'powders are from 0.02 to 0.05 micron particle size, then lower concentrations can be used of about 10 to about 50 grams per liter. If the particle size is about 0.1 to 0.4 micron, then concentrations of about 50 to 200 grams per liter give the best results.

Especially desirable results from a decorative as well as a corrosive resistant standpoint are obtained by the addition of very fine powders of kaolin or glass, any color, in concentrations of about 50 to 200 grams per liter to air-agitated bright nickel plating baths such as those described in U.S. 2,647,866, issued August 4, 1953; 2,800,440 and 2,800,442, issued July 23, 1957. Superfine powders of 0.02 to 0.5 micron particle size are especially outstanding in performance. The nickel plate obtained from these agitated bright plating baths containing, for example, about -200 grams per liter of these superfine powders, has a semi-bright microscopically-line pitted surface with a satin smooth sheen of very pleasing appearance. The fine suspended powders tend to cling to the nickel plate, and this effect and the specific physical structure, particle size and shape, amorphous texture, etc., and the chemical structure of the powder apparently causes the microscopically-fine pitting effect which converts the normally bright or semi-bright surface to a satin smooth sheen. The uniformity of the sheen is unusual and especially noteworthy in that a 0.2 mil to 2 thick or thicker plate can have the same satin appearance. Thus, when contoured articles such as camera parts,ornaments, grilles, automobile dashboards, door handles, marine hardware, etc., are plated, the satin appearance of the plate in the recessed areas (low current density areas) is the same as the plate in the higher current density areas.

Concentrations of fine insoluble silicate powders as high as 500 grams per liter in the bath do not produce any appreciably diiferent results than the optimum concentrations of about 50 to 200 grams per liter. agitation or mechanical agitation including ultra-sonic agitation of the baths can be used. The faster or more powerful the agitation and the liner the particle size down to colloidal dimensions, the lower the concentration of fine powder that is necessary, and concentrations as low as 10 grams per liter may be used to obtain a smoky satin finish by using strong agitation'and powders having a size of about 0.1 to 0.3 micron or ultrafine particles having a size of 0.02 to 0.04 micron. Agitation is necessary to keep the fine powder suspended. in the bath during plating. In general, however, it is preferred to use from about 50 to 200 grams per liter of very fine powder having a size less than 5 microns and preferably less than 2 microns in air-agitated baths.

Analysis of a satin nickel plate from an air agitated bright nickel bath containing superfine insoluble silicate Air powders of particle size of 0.02 to 0.5 micron in a concentration of about 100-200 grams per liter shows usually not higher than about 2.5% insoluble powder uniformly distributed in the nickel plate. Microscopic examination of the surface of the plate shows an extremely uniform finely pitted surface. This satin plate has excellent adhesion, for example, to ferrous, copper, and brass surfaces just as the plate from the clear nickel bath, and it is quite surprising that these agitated baths containing 100 to 200 grams per liter of superfine insoluble silicate powders give exceptionally smooth to the touch satin plate even in 20 mil and thicker plates, and that practically no gas pitting occurs. The addition of these fine powders in the 1 same concentrations, that is, 50 to 200 grams per liter of, for example, kaolin or glass, or talc, to agitated plain dull nickel baths, such as the Watts bath, makes the dull nickel plate obtained even duller and more unsightly in appearance;

The throwing power and covering power of the agitated bright nickel baths with the suspended powders is about the same as without the fine powders present. It was found that in plating articles with recessed areas and with shelf areas that no roughness was obtained on the areas on which settling can occur.

The leveling of the bright nickel plate is not decreased by the presence of the finely powdered insoluble silicates in the bath. In fact, the leveling seems definitely improved in most cases.

The satin nickel plate obtained from bright or semibright nickel plating baths containing these fine powders can easily be polished or bufied'to a high lustre, thus, :as already mentioned, beautiful two-tone efiects can readily be obtained by buffing raised or accessible portions of the satin nickel plated object. Also, where a brush satin finish is desired, this can be accomplished by using, for example, 120 or 150 emery polish on the'basis metal, then'these coarse polishing lines can be seen in the satin sheen nickel, despite the high leveling characteristics of the baths. That is, the coarse polishing lines are only partially smoothened out. Thus, in this Way, an excellent brush type satin finish is obtained of higher corrosion protection than when a nickel plate is brushed after plating.

When concentrations of less than about 10 grams per liter of ultra-fine powders of the insoluble silicates are used in agitated bright or semi-bright nickel plating baths, then the satin appearance of the nickel plate decreases, and the plate has a smoky appearance and has more re flectivity, especially in recessed areas. Thus, it is preferred for the most general satin finish applications as Well as corrosion protection applications to use concentrations of the very fine powders greater than about 10'grams' per liter.

The use of dispersing agents, peptizing agents in conjunction with the fine powders is often helpful. It is also helpful to process the dispersion with high energy dispersion machines which accomplishes practically complete dispersion into ultimate particle size, but While helpful, this treatment is not necessary for obtaining excellent satin nickel plate. Such procedures help in reducing the need for using the higher concentrations of powder in the bath such as the 100 to 200 grams per liter concentrations.

However, concentrations of 100 to 200 grams per liter of a commercial fine insoluble silicate powder such as kaolin ,(colloidal) N.F. Merck gives excellent satin nickel plate when used as purchased in regular air agitated bright nickel plating baths. There are no particular operating troubles because concentrations of 150 grams per liter or higher of this powder are used in the bath instead of, for example, to grams per liter of 0.02 to 0.5 micron particle size. The powders of extremely fine or ultra fine particle size of 0.03 to 0.04 micron or less, are generally more expensive, that is, if the great percentage of the particles are of these ultra-fine diameters, however, lower concentration can be used to obtain equivalent effects.

Before technical grade powders are used commercially they should always be checked first in small scale tests such as 14 liter baths before being added to large baths because certain harmful impurities such as metallic powders or too coarse particles may be present which will cause rough plate, especially on shelf areas. Except for the necessity of this precautionary check, technical grade powders normally produce equal results to those obtained from the use of high purity grades of the same particle size and structure. Also, if the powder is not wetted properly by the nickel bath, it should be checked for freedom of fatty or oily films, as already mentioned in the case of talc powder.

It is important to avoid metallic powders in these baths, for example, poorly cast nickel anodes which might powder during use and disperse nickel particles in the bath definitely can cause roughness, also high concentrations of activated carbon in the bath can cause very undesirable roughness. The carbon from rolled or cast carbon-containing nickel anodes, however, does not usually cause roughness when floating in the baths. High concentrations of iron dissolved as ferrous or ferric iron in the baths do not cause settling roughness or gross pitting eifects in the baths even at the pH values of 3.8 to 5.5 although at such' pH values dissolved iron tends to precipitate. Zinc or cadmium ions can be present in the baths in concentrations as high as about one gram per liter without detrimentally affecting the plate. Cadmium tends to whiten the plate somewhat. Copper carbonate is surprisingly not harmful in high concentrations. The presence of sodium and magnesium salts are not harmful. Ammonium salts in concentrations higher than about 15 grams per liter is in general not desirable because of reduction of the limiting cathode current density. In general, bright or, semi-bright nickel plating baths of the Watts, high chloride, sulfamate and fluoborate baths or mixtures can be used. Also, other buifers besides boric' acid may be used, such as formates, citrates, etc.

The pH of the baths may be from about 2 to 6, though the preferred pH values are from about 3.5 to 5.2. The temperature of the baths can be from room to at least 170 F., though in general a temperature of about F. to about F. is preferred. 1

As already mentioned, the use of these fine insoluble silicate powders does not create a satin sheen nickel plate when added to plain nickel baths that normally produce dull nickel deposits such as the Watts nickel bath. The nickel bath must be a semi-bright or bright nickel plating bath. The best addition agents or brighteners to achieve the semi-bright and bright nickel plating conditions necessary to obtain satin nickel after the addition to the bath of the afore-mentioned powders in concentrations of about 10 to 500 grams per liter are the following: the brighteners of the class of organic sulfon-compounds including aromatic and unsaturated aliphatic sulfonic acids,

sulfonamides and sulfonimides, such as benzene sulfonic acids, naphthalene sulfonic acids, p-toluene sulfonamide, benzene sulfonamide, o-benzoyl sulfimide, allyl sulfonic acid, 2-butyne-l,4-disulfonic acid, o-sulfobenzaldehyde, etc; the addition agents which produce semi-bright sulfurfree nickel plate such as formaldehyde, chloral hydrate, bromal hydrate, coumarin, butyne diol, used alone or in combinations; combinations of the sulfur-free addition agents with those ofthe organic sulfon-type, and combina- Surface active agents may be present in the baths, but are not usually necessary in the air agitated baths.

The maximum increase in satin sheen is obtained when the fine powders are used in the agitated full bright nickel plating baths such as the air-agitated bright nickel plating baths possessing good leveling as those illustrated in Examples 1, 2 below. Less satin lustre, for example that of Example 3, is obtained when the nickel baths contain only the carrier type brightener such as benzene sulfonic acids, naphthalent sulfonic acids, p-toluene sulfonamide, benzene sulfonamide, o-benzoyl sulfimide, etc. In the latter cases the satin lustre is flatter. This is also true when the semi-bright sulfur-free type of addition agent such as formaldehyde, chloral hydrate, or bromal, is used solely with the fine powders, and with these sulfurfree semi-bright addition agents such as those mentioned, as well as coumarin, it is best to use the ultra-fine particle size powders of less than 0.2 micron particle size, and preferably less than 0.05 micron particle size as determined with the electron microscope. There seems to be a definite improvement in leveling with the semi-bright sulfur-free addition agents when these ultra-fine particle size powders are used. The corrosion protection to steel, aluminum, magnesium, and zinc base die-castings of such chromium plated nickel is greatly improved as shown by repeated passage of such severe accelerated tests as the Corrodkote, with and without a final, sulfur-containing bright nickel over-lay plate to give a double layered plate, so-called duplex or dual nickel, of 40 to 60 ratio to 80 to 20 ratio of ultra-fine satin semi-bright sulfur-free nickel plating baths containing organic suliion-type addition agents and the fine powders as illustrated in Examples 1, 2 and 3 when plated to a thickness of 1 to 1.5 mils on steel or copper plated zinc die-cast and given the usual 0.01 mil final chromium will itself pass many successive Corrodkote and Cass tests of 20 hours each without any failure; This is due mainly to the development of a very fine favorable porosity pattern in the final thin, 0.01 mil, chromium plate. If the fine powder of kaolin, for example, is omitted, the resulting full bright nickel plate of the same thickness and with the same thin final chromium plate will fail in only one cycle of 20 hours Corrodkote testing.

There is a strong tendency for the finely-divided powders, such as kaolin and tale to remain clinging to the nickel surface after the plated article is withdrawn from the bath and rinsed thoroughly, and remains clinging even after the usual final chromium plate of 0.005 to 0.05 mils is applied. For such clinging particles which are only slowly soluble in acids or sequestering agents, it was found that a very thin plate from a zinc cyanide bath (about 1 to 3 minutes plating) followed by an acidic or alkaline dip to remove the zinc, also removed the tightly clinging kaolin and the like particles. Actually, the particles on the work look like a fine dust and are not really too unsightly'even if left on, 'and they do not hurt the or, they can be removed to a certain extent by ultra-sonic cleaning.

The satin nickel plate accepts chromium plate like regular nickel plate, and in general only the usual thicknesses of final chromium need be used, that is, 0.01 mil, though thicknesses of 0.1 mil or 0.2 mil may be used. Besides, the final satin nickel finish as such, or with the usual final chromium finish, the satin nickel plate can be given a rhodium, silver, tin, brass, bronze, copper, gold, or tinnickel' (65-35) alloy or other final thin coating. Thin wax, or soluble-wax, films or clear lacquers greatly decrease finger marking of the final coating, such as nickel, bronze, silver, brass, etc. Chromium, gold, rhodium,

' and tin-nickel alloy plate do not need these organic coatcentrations of about 10 to 500 grams per liter.

aisasria only 0.2 to 0.5 mil thickness are needed. For outdoor exposure in industrial or marine atmospheres thicknesses of 1 to 1.5 mils should be used. Also, the satin nickel can be used as the top layer of a double layered or duplex nickel coating, with the undercoat consisting of at least 0.7 mil of send-bright sulfur-free nickel. This would be for the most severe outdoor exposure as for marine hardware. As already mentioned, however, the corrosion protection to steel, aluminum, magnesium, brass and zinc of the satin nickel with the usual final chromium plate (0.01 mil) even from baths containing organic sulf'oncompounds is amazingly superior to the fully bright nickel obtained from the same baths without the fine powders present.

Besides the excellent results obtained with finely powdered kaolin (china clay), the essential constituent of whichis the mineral kaolinite (Al Si O (OH) practically equally excellent results are also obtained with the finely powdered minerals, mica (KAl Si O (OH) talc (a hydrous magnesium silicate), pyrophyllite, and celsian (a barium aluminosilicate). A strontium aluminosilicate powder also gives good results. These finely powdered materials produce optimum results in concentrations of about 30 to 200 grams per liter in the agitated bright or semi-bright nickel baths when present in particle sizes of less than 5 micron diameters, and preferably when present in particle sizes of less than 2 micron diameters. Particle sizes of 0.02 to 0.5 micnon diameters produce the most pleasing satin nickel and also the highest corrosion protection when the satin nickel is plated with the usual 0.01 final chromium plate.

Kaolin or china clay powder does not agglomerate or gel to any serious degree in the nickel baths, and it is essential that any natural clay that is used not agglomerate or gel in the nickel bath to such an extent that a major percentage of the particles becomes greater than 5 microns in average diameter. When clay particles larger than 5 microns diameter are formed in a major percentage in the nickel bath by gelation or agglomeration, the desired satin finish is not obtained, that is, the micnofine pitting does not occur to the necessary extent. As an example, montrnorillonite which is the main constituent of bentonite, gels in the bath to part-icles greater than 5 microns diameter and does not produce the satin nickel plate of this invention.

Natural clays usually consist of mixtures of the clay minerals and the ratios of aluminum to silicon and oxygen =atcms can vary within rather wide limits. Also, there may be present iron, calcium, tit-anium, magnesium, potassium and sodium, as in the china clays, ball clays, fire clays etc. The essential factor for the use of clay powders for the purpose of this invention is, as already mentioned, that the major portion of the particles should not gel to sizes greater than 5 microns ave-rage diameter.

Ground glasses (soft glass, Pyrex, or other glasses) which are insoluble silicates give excellent results in con- Particle sizes greater than about 2 microns and especially those greater than about 5 microns in average diameter cause rough deposits. The best satin nickel results are obtained with glass powders finer than 2 microns and preferably of 0.03 to 0.5 micron particle size, The glass powders may be made of colored glasses. Ordinary glass which is a mixed silicate contains about 10% sodium, 5% calcium and 1% aluminum. It consists essentially of an aluminosilicate framework within which are embedded sodium and calcium ions. The fine-grained lustrous satin nickel plate obtained with the finest ground glass (0.03 to 0.5 micron) in agitated bright or semi-bright nickel baths is of excellent appearance.

Below are listed some preferred examples of baths for the production of the satin nickel plate of this invention. Especially excellent results are produced by Examples 1 to 5. In general, the cathode current density is from about 10 to amps./ sq. ft. Mixtures of the silicate powders size) 75-150 NiSO 6H O 15 -3 00 NiCl -6H O 30-100 H 30 30-40 p-Toluene sulfonamide 1-2 o-Benzoyl sulfimide 0.1-2 Allyl sulfonic acid 0.5-6 N-allyl quinaldinium bromide 0.002-0.01 pH=3.0-5.2.

Temp.=room to 160 F. Air agitation of the bath.

Example ll Conc., grams/ liter Powdered glass (0.03-0.3 micron particle size) 40-200 NiSO -6H O 150-300 H BO 30-40 o-Benzoyl sulfimide 1-3 Allyl sulfonic acid 0.5-4 2-butyne-l,4-disulfonic acid 0.1-l0 2-butynoxy-1,4-diethane disulfonic acid 0.05-0.1 pH=2.8 to 5.2.

Temp.=room to 165 F. Air agitation or mechanical agitation.

Example III Conc., grams/liter Ground glass (Whittaker, Clark and Daniels #718 finest powder) 30-200 NiSO -6H O 75-200 NiCl -6H O 30-150 N BO 30-40 o-Benzoyl sulfimide 1-3 p-Toluene sulfonamide 1-2 pH=3.0to 5.0.

- Temp.=room to 180 F.

Air agitation or mechanical or both.

. Example IV Conc., grams/liter Kaolin (colloidal) NF.

Temp.=room to 150 F. Mechanical or air agitation or both.

Example V Conc., grams/liter Kaolin ultrafine powder (0.02-0.04 micron) 10-200 NiSO '6H O 100-300 NiCl2 6H O 30-75 H BO 30-40 Allyl sulfonic acid 1-3 Benzene sulfonamide 1-3 2-butynoxy-1,4-diethane disulfonic acid 0.1-0.2

I 8 pH=5 .0-5 .2.

Temp.=room to 160 F. Air or mechanical agitation.

Z-butynoxy-1,4-diethoxyethane disulfonic acid 0.1-0.2 pH-=3.0-5.0.

Temp.=room to 170 F. Mechanical or air agitation.

- Example VII Conc. grams/liter Ground glass (microfine powder, 0.02-0.5 micron) 40-150 NiCO BaCO orSrCO microfine powder 5-150 NiSO -6H O -300 NiCl -6H O 30-100 H BO 30-40 Ni(BF 1-3 o-Benzoyl sulfimide 0.2-3 p-Toluene sulfonamide 1-2 Allyl sulfonic acid 1-4 2-'butynoXy-l,4-diethane disulfonic acid 0.1-0.3 pH=5.0 to'5.2. Temp.=room to F.

Mechanical agitation.

Example VIII I Grams/liter Kaolin (colloidal) NF. 10-150 NiCO mic-roiine powder 5-150 NiSO -6H O 100-300 H BO 30-60 p-Toluene sulfonamide 1-2 Allyl sulfonic acid 1-4 Z-butynoxy-lA-diethane disulfonic acid 0.1-0.3

pH=5.0-5.2, Temp.=room to F. Mechanical or air agitation.

What is claimed is:

1. A method for electrodepositing a fine-grained lustrous nickel plate comprising the step of electrolyzing with externally applied current an aqueous acidic solution of at least one nickel salt and at least one soluble organic addition agent capable of producing said fine-grained lustrous plate, said bat-h containing about 10 to about 500 grams per liter of at least one material selected from the group consisting of the bath insoluble silicates of aluminum, magnesium, boron, calcium, barium, and strontium, and the mixed silicates thereof including alkali metals, said material being in the form of a fine powder, the major portion of which has a. particle size which is less than 5 microns average diameter and electrodepositing on said lustrous plate an overlayer of 'a metal selected from the group consisting of chromium, rhodium, silver, tin, brass, bronze, copper, gold and an alloy consisting of 65% tin and 35%.nickel.

with claim 1 wherein said with an externally applied current an aqueous acidic solution of at least one nickel salt selected from the group consisting of nickel sulfate, nickel chloride, nickel fluoborate, and nickel sulfamate and at least one soluble organic addition agent capable of producing said fine-grained lustrous plate, said bath containing dispersed therein about 10 to about 500 grams per liter of at least one material selected from the group consisting of the bath insoluble silicates of aluminum, magnesium, boron, calcium, barium, and strontium, and the mixed silicates thereof including alkali metals, said material being in the form of a fine powder, the major portion of which has a particle size which is less than microns average diameter, and thereafter plating on said surface an overlayer of a metal selected from the group consisting of chromium, rhodium, silver, tin, brass, bronze, copper, gold, and an alloy consisting of 65 tin and 35 nickel.

7. A method in accordance with claim 6 wherein the metal of said overlayer is chromium.

8. A composite electroplate on a metal surface susceptible to atmospheric corrosion which comprises a nickel plate with a metallic over-lay, said nickel plate having been electrodeposited from an acidic nickel plating bath containing dissolved therein at least one organic nickel brightener capable of producing semi-bright to fully bright nickel plate and having dispersed therein at least one type of bath insoluble inorganic non-metallic particles, the average diameter of the individual particles thereof being less than about 5 microns, an electrodeposited over-lay plate of a metal selected from the group consisting of chromium, rhodium, silver, tin, brass, bronze, copper, gold and an alloy consisting of 65% tin and 35% nickel on said nickel plate, said over-lay plate being less than about 5 microns in thickness, said type of particles in said nickel bath being selected from the group consisting of the bath insoluble silicates of aluminum, magnesium, boron, calcium, barium and strontium, and the mixed silicates thereof including alkali metals, and said particles being present in said nickel bath in an amount sufficient to produce a fine porosity pattern in the said over-lay plate.

9. A composite electroplate in accordance with claim 8 wherein said nickel plate directly overlies an electrodeposit consisting essentially of nickel.

10. A composite electroplate in accordance with claim 8 wherein said bath insoluble inorganic non-metallic particles are present in the nickel bath in a concentration of at least about 10 grams per liter.

11. A composite electroplate in accordance with claim 8 wherein said dissolved organic nickel brig-htener is selected from the group consisting ofaromatic and unsaturated aliphatic sulfonic acids, sulfonamides and sulfonimides.

12. A composite electroplate in accordance with claim 11 wherein said dissolved organic nickel brightener is oenzoyl sulfimide.

13. A composite electroplate in accordance with claim 8 wherein said over-lay plate is chromium.

14. A composite electroplate in accordance with claim 8 wherein said nickel plate directly overlies an electro deposit consisting essentially of lustrous nickel and said over-lay plate is chromium.

15. A method in accordance with claim 1 wherein said material is dispersed in said bath during plating by air agitation.

16. A method in accordance with claim 6 wherein said material is dispersed in said bath by air agitation.

17. A method in accordance with claim 1 wherein there is present in said solution at least one compound selected from the group consisting of boric acid, formates and citrates.

References Cited in the file of this patent UNITED STATES PATENTS 942,729 Kern Dec. 7, 1909 970,755 Rosenberg Sept. 20, 1910 2,483,996 De Marinis Oct. 4, 1949 2,637,686 McKay May 5, 1953 2,658,839 Talmey et al Nov. 10, 1953 2,756,489 Morris July 31, 1956 2,767,464 Nack et a1. Oct. 23, 1956 2,849,353 Kardos Aug. 26-, 1958 2,904,418 Fahnol Sept. 15, 1959 2,999,798 Eitel Sept. 12, 1961 3,061,525 Grazen Oct. 30, 1962 FOREIGN PATENTS 17,313/28 Australia July 2, 1929

Claims

1. A METHOD FOR ELECTRODEPOSITING A FINE-GRAINED LUSTROUS NICKEL PLATE COMPRISING THE STEP OF ELECTROLYZING WITH EXTERNALLY APPLIED CURRENT AN AQUEOUS ACIDIC SOLUTION OF AT LEAST ONE NICKEL SALT AND AT LEAST ONE SOLUBLE ORGANIC ADDITION AGENT CAPABLE OF PRODUCING SAID FINE-GRAINED LUSTROUS PLATE, SAID BATH CONTAINING ABOUT 10 TO ABOUT 500 GRAMS PER LITER OF AT LEAST ONE MATERIAL SELECTED FROM THE GROUP CONSISTING OF THE BATH INSOLUBLE SILICATES OF ALUMINUM, MAGNESIUM, BORON, CALCIUM, BARIUM, AND STRONTIUM, AND THE MIXED SILICATES THEREOF INCLUDING ALKALI METALS, SAID MATERIAL BEING IN THE FORM OF A FINE POWDER, THE MAJOR PORTION OF WHICH HAS A PARTICLE SIZE WHICH IS LESS THAN 5 MICRONS AVERAGE DIAMETER AND ELECTRODEPOSITING ON SAID LUSTROUS PLATE AN OVERLAYER OF A METAL SELECTED FROM THE GROUP CONSISTING OF CHROMIUM, RHODIUM, SILVER, TIN, BRASS, BRONZE, COPPER, GOLD AND AN ALLOY CONSISTING OF 65% TIN AND 35% NICKEL.