NO150214B - PROCEDURE FOR ELECTROLYTIC EXPOSURE OF NICKEL, COBOLT AND / OR BINARY OR TERNAIR ALLOYS OF METALS SELECTED FROM THE NICKEL, IRON AND COBOLT AND PLATING SOLUTION FOR THE PREPARATION OF THE PROCEDURE - Google Patents

Description

The present invention relates to a method for the electrolytic deposition of nickel, cobalt and/or binary or ternary alloys of metals selected from the group of nickel, iron and cobalt, comprising passing current from an anode to a cathode through an aqueous, acidic plating solution containing at least one component selected from nickel compounds, cobalt compounds and iron compounds which provide nickel, cobalt and iron ions for precipitation of nickel, cobalt, nickel/cobalt alloys, nickel/iron alloys, cobalt/iron alloys or nickel/iron/cobalt alloys , for a sufficiently long time for a metal deposit to form on the cathode, and a plating solution to carry out the method.

In order to achieve a saving of nickel and reduced costs, a number of methods have been used within the nickel plating industry. Some of the methods include reducing the thickness of the nickel deposit, replacing nickel in whole or in part with cobalt in cases where cobalt is cheaper or more easily available, and more recently electroplating with nickel/iron, cobalt/iron, and nickel/cobalt /iron alloys in which up to 60% of the deposit may contain relatively cheap iron. As the thickness of the deposit is reduced, however, it is necessary to use more effective or "powerful" nickel gloss additives or higher concentrations of gloss additives, so that the degree of gloss to which the nickel plating industry has become accustomed,

can be achieved. The "powerful" nickel gloss additives or high concentration of gloss additive are indeed able to produce

bring the desired shine and leveling, but can nevertheless have unacceptable side effects. For example, the nickel plating can peel off or exhibit strong stress or brittleness, less susceptibility to subsequent chrome plating, hazes, reduced coverage or "spreading" at low current density or streaking and uncovered plate, i.e. areas where no deposit is formed.

Although electrolytic deposition of nickel/iron, cobalt/iron or nickel/cobalt/iron alloys is in many ways very similar to electrolytic deposition of nickel, as similar equipment and operating conditions are used, electroplating with ferrous alloys still offers nickel and/or cobalt on certain special problems. E.g. it is a requirement for the precipitation of iron alloys of nickel and/or cobalt that the iron in the electrolytic plating solution is predominantly divalent iron instead of trivalent. At a pH value of approx. 3.5, basic ferric salts will precipitate which can clog the anode bags and filters and give rough deposits. It is therefore advantageous to prevent precipitation of any basic ferric salts. This can be achieved by adding suitable complexing, chelating, antioxidant or reducing agents to the ferrous alloy plating bath, as described in US-PS 3 35 4 05 9, US-PS 3 804 726 or US-PS 3 806 429. Although these complexing or chelating agents are necessary to provide a solution to the problem with ferric ions, the use of these can lead to unwanted side effects. They can cause a reduction in the evenness of the deposit and can also produce streaky, cloudy or dull deposits which may also show steps or holidays, i.e. areas that are not plated or only very thinly plated compared to other parts of the deposit.

To overcome the harmful effects of high concentrations of brighteners or "powerful" brighteners or to counteract the undesirable side effects of iron or iron-dissolving substances when these are present in electrolytic nickel and/or cobalt or ferrous nickel and/or cobalt plating bath, it has been proposed in US-PS 2,654,703 to add various sulfinic acids or salts thereof. Unfortunately, sulfinic acids and their salts are unstable and subject to rapid oxidation by atmospheric oxygen to the corresponding sulfonic acids or sulfonic salts, and in this state they are no longer effective in overcoming the various above-mentioned side effects. The use of sulfinic acids or their salts also considerably reduces the uniformity of the precipitation.

It is an aim of the present invention to provide methods and plating baths for electrolytic precipitation of nickel, 'cobalt' or binary or ternary alloys of nickel, cobalt and iron which can withstand high concentrations of gloss additives to a greater extent. It is a further purpose of the invention to obtain precipitates of nickel, cobalt or binary or ternary alloys of nickel, cobalt and iron, characterized by increased ductility, glossiness, covering ability and ability to smooth and hide stripes. Yet another purpose of the invention is to overcome the problems caused by the presence of iron or iron-dissolving substances in electrolytic baths for plating ferrous nickel and/or cobalt alloys. Other purposes of the invention will be apparent from the following detailed description.

From SE patent document 205 7 81 and the US patent documents

3 376 207 and 2 697 392 it is known to use sulfolane compounds in nickel plating baths. Sulfolane compounds are saturated compounds that can be prepared from the unsaturated compound sulfone. In US patent document 3,697,392, the compounds used are indeed designated as "sulfolene compounds", but a comparison with the other two above-mentioned patent documents shows that this is wrong terminology, and that in reality it is about the saturated compounds, i.e. . sulfolane compounds .

According to the invention, it has been found that the unsaturated sulpholene compounds can be advantageously used in the electrolytic baths. In general, a plating solution containing 5*10 - 5-10 1 mol/l of an unsaturated cyclosulfone with the following general structural formula can be used:

where R.j , 1*2» R_ and R. mean hydrogen, a lower alkyl or -hydroxyl.

The baths according to the invention can also contain an effective amount of one or more of the following additives:

a) Gloss additives of class I

b) Gloss additives of class II

c) Antipitting agents or wetting agents.

The term "class I gloss additives" as used

in the manufacture and is defined in Modern Electroplating,

Third Edition, with F. Lowenheim as editor, is intended to include aromatic sulfonates, sulfonamides, sulfonimides, sulfinates, etc., besides aliphatic or aromatic-aliphatic alkene- or acetylenically unsaturated sulfonates, sulfonamides, sulfonimides/ etc. Special examples of such plating additives are:

(lj sodium-o-sulfobenzimide

(2) disodium 1,5-naphthalene disulfonate

(3) trisodium 1,3,6-naphthalene trisulfonate

(4) sodium benzene monosulfonate

(5) dibenzene sulfonimide

(6) sodium allyl sulfona.t

(7) sodium 3-chloro-2-butene-1-sulfonate

(8) sodium - -styrene sulfonate

(9) sodium propargyl sulfonate

(10) , monoallyl sulf amide

(11) ' diallyl sulfamide

(12) allyl sulfonamide

Such plating additives, which can be used alone or in suitable combinations, should preferably be used in quantities of

0.5 - 10 g/l. They provide the advantages described in the above-mentioned publication, and which are well known to anyone skilled in the art of nickel plating.

The term "glazing additive of class II" as used in this presentation and described in Modem Electroplating, Third Edition, with F. Lowenheim as editor, is intended to include such plating additives as e.g. the reaction products of epoxides (with oc-hydroxy-acetylene alcohols, e.g. diethoxylated 2-butyne-1,4-diol or dipropoxylated 2-butyne-1,4-diol, other acetylene compounds, N-heterocyclic compounds, dyes, etc. Special examples of such plating additives are:

(1) 1,4-Di-(/4-hydroxyethoxy)-2-butyne

(2) 1,4-di-(j^-hydroxy-f-chloropropoxy)-2-butyne

(3) 4-di-(/*-, N^epoxypropoxy)-2-butyne

(4) 1, 4-di-(^-hydroxy-N^-butenoxy)-2-butyne

(5) 1,4-di-(2'-hydroxy-4'-oxa-6 1-heptenoxy)-2-butyne

(6) N-(2,3-dichloro-2-propenyl)-pyridinium chloride

(7) 2,4,6-trimethyl-N-propargyl-pyridinium bromide

(8) N-allylquinaldinium bromide

(9) 2-butyne-1,4-diol

(10) propargyl alcohol

(11) 2-methyl-3-butyn-2-ol

(12) quinaldyl-N-propanesulfonic acid betaine

(13) quinal didimethyl sulfate

(14) N-allylpyridinium bromide

(15) isoquinaldyl-N-propanesulfonic acid betaine

(16) isoquinaldine dimethyl sulfate

(17) N-allylisoquinaldine bromide

(18) 1,4-di-(^-sulfoethoxy)-2-butyne

(19) 3-(/S-Hydroxyethoxy)-propyne

(20) 3-(^-Hydroxypropoxy)-propyne

(21) 3-(^-sulfoethoxy)-propyne

(22) phenosafranine

(23) fuchsia

When used alone or in combination, preferably in amounts of 5 - 1000 mg/l, a class II gloss additive may produce no visible effect on the precipitate, or it may produce fine-grained precipitates with a semi-gloss. However, the best results are obtained when Class II gloss additives are used together with one or more Class I gloss additives to obtain optimum deposition gloss, degree of gloss, leveling, current density range for bright plating, coverage and low current density, etc.

The term "anti-pitting agent or wetting agent" as used in the present invention is intended to include a material which serves to prevent or reduce gas pitting. An antipitting agent used alone or in combination, preferably in amounts of 0.05 - 1 g/l, can also serve to make the baths more compatible with pollutants such as e.g. oil, fat, etc. by its emulsifying, dispersing or dissolving effect on such contaminants and thereby promoting the achievement of better precipitations. Preferred antipitting agents include sodium lauryl sulfate, sodium lauryl ether sulfate, and sodium dialkyl sulfosuccinates.

The nickel compounds, cobalt compounds and iron compounds used to obtain nickel, cobalt and iron ions for the precipitation of nickel, cobalt or binary or ternary alloys of nickel, cobalt and iron (e.g. nickel/cobalt, nickel/iron, cobalt/iron and nickel/cobalt/iron alloys), are typically added as sulfate, chloride, sulfamate or fluoborate salts. Sulfate, chloride, sulfamate or fluoborate salts of nickel or cobalt are used in the plating solutions according to the invention in concentrations which are sufficient to give nickel and/or cobalt ions in concentrations of 10 - 150 g/l. When the iron compounds, e.g. iron sulfate, iron chloride, etc., if the nickel and/or cobalt-containing jletting solutions according to the invention are added, they are used in quantities sufficient to give iron ions in concentrations of 0.25 - 25 g/l. The ratio between nickel and/or cobalt ions and iron ions can be in the range 50:1 - 5:1.

The iron ions in the plating solutions according to

the invention can also be added through the use of iron anodes instead of by adding iron compounds. If e.g. a certain percentage of the overall anode surface in an electrolytic plating bath for nickel consists of iron anodes, after a certain period of electrolysis sufficient iron will have been introduced into the bath by chemical or electrochemical dissolution of the iron anodes to obtain the desired concentration of iron ions.

The plating baths according to the invention which contain

holds nickel, cobalt, nickel and cobalt, nickel and iron, cobalt and iron or nickel, cobalt and iron, may also contain 30-60 g/l, preferably approx. 45 g/l, boric acid or another buffer agent to regulate the pH value (e.g. from about 2.5 to 5, preferably about 3-4) and to prevent burning as a result of high current density . !

When iron ions are present in the plating baths according to the invention, in order to make the iron ions soluble it is desirable to incorporate one or more agents which have a complexing, chelating, antioxidant or reducing effect on iron or make iron soluble, e.g. citric acid, maleic acid, glutaric acid, gluconic acid, ascorbic acid, isoascorbic acid, muconic acid, glutamic acid, glycemic acid or aspartic acid or similar acids or their salts. These agents, which have a complexing or dissolving effect on iron, can be present in the plating solution i

in

concentrations of 1-100 g/l, naturally depending on how much iron is present in the plating bath.

In order to prevent "burning" in areas with high current density, obtain a more even temperature regulation of the solution and regulate the amount of iron in the iron-containing alloy precipitates, stirring of the solution can be used there. Agitation with air, mechanical agitation, pumping, stirring by means of cathode rods and other means of stirring the solution are all satisfactory. Furthermore, the baths can work without stirring.

The operating temperature of electrolytic plating baths according to the invention can be 40-85°C, preferably 50-70°C.

The average cathode current density may lie in the range

2 2

50-1200 A/m and 300-600 A/m provide an optimal range.

Typical aqueous nickel-containing plating baths (which may be used in combination with effective amounts of synergistic additives) include the following baths, where all concentrations are in g/l unless otherwise stated:

When iron sulphate (FeSO^<*>7H20) is incorporated into the preceding bath, the concentration will be approx. 2.5 - 125 g/l.

A typical nickel plating bath of the sulfamate type that can be used in carrying out the present invention can contain the following components:

When iron sulphate (FeS04'7H20) is incorporated in the preceding bath, the concentration will be approx. 2.5 - 125 g/l.

A typical chloride-free nickel plating bath of the sulfate type that can be used in carrying out the present invention can contain the following components:

When iron sulphate (FeSO^* 71^0) is incorporated in the previous bath, the concentration will be approx. 2.5 - 125 g/l.

A typical chlorine-free nickel plating bath of the sulfamate type that can be used in carrying out the present invention can contain the following components:

When iron sulphate (FeSO^"71^0) is incorporated in the preceding bath, the concentration will be approximately 2.5 - 125 g/l.

In the following, aqueous cobalt-containing and cobalt/nickel-containing plating baths are indicated that can be used in carrying out the present invention:

The pH value of the typical compositions in table V can lie at approx. 3-5 and preferably approx. 4.

When iron sulphate (FeSO^ * 7H20) is incorporated in the previous baths, the concentration will be 2.5 - 125 g/l.

Typical plating baths containing nickel and iron, and which can be used in carrying out the present invention, ] may contain the following components:

When ferrous sulphate (FeS04"7H20) is incorporated into a bath with a composition as stated above, it is also desirable to incorporate one or more agents that have a complex-forming, chelating or dissolving effect on iron, in concentrations of approximately 1 - 100 g/l, naturally depending on the iron concentration present.

It will be understood that the above baths may contain compounds in amounts outside the range defined by the stated preferred minimum and maximum values, but that the most satisfactory and economical operation is usually obtained when the compounds are present in the baths in the amounts indicated.

The pH of all of the foregoing illuminating aqueous compositions containing nickel, cobalt, nickel and cobalt, nickel and iron, cobalt and iron, or nickel, cobalt and iron, during plating can be maintained at 2.5 - 5.0 and preferably between 3.0 and 4.0. During the operation of the bath, the pH value can normally have a tendency to rise, and it can be regulated with the help of acids such as e.g. hydrochloric acid, sulfuric acid etc.

Anodes used in the above-mentioned baths can consist of the specific simple metals that are plated with at the cathode, e.g. nickel or cobalt by plating with nickel and cobalt respectively. When plating with binary or ternary alloys, e.g. nickel and cobalt, cobalt and iron, nickel and iron or nickel, cobalt and iron, the anodes may consist of the respective separate metals suspended in a suitable manner in the bath as rods, strips or small pieces in titanium baskets. In such cases, the ratio between the anode surfaces of the different metals is set in accordance with the particular alloy composition desired at the cathode. For plating with binary or ternary alloys, alloys of the respective metals can also be used as anodes in a weight ratio between the metals corresponding to the percentage weight ratio between the same metals in the desired electroplated alloy on the cathode. These two types of anode systems will usually provide a largely constant ion concentration of the respective metals in the bath. If, with anodes of alloys with a fixed metal ratio, a certain imbalance should occur between the metal ions in the bath, adjustments can be made from time to time by adding suitable corrective concentrations of the individual metal salts. All anodes are usually covered in a suitable way with fabric or plastic bags of the required porosity to reduce to a minimum the supply to the bath of metal particles, anode slime etc. which can migrate to the cathode either mechanically or electrophoretically and cause roughness in the deposit on the cathode.

The substrates as the precipitates according to the invention

which contain nickel, cobalt, nickel and cobalt, nickel and iron, cobalt and iron or nickel, cobalt and iron, can be applied to e.g. nickel, cobalt, nickel-cobalt, copper, tin, brass etc. Other typical substrate materials from which objects to be plated are made include ferrous metals, e.g. steel, copper, copper alloys such as brass, bronze, etc., and zinc, especially in the form of zinc-based mold castings, and all these metals can carry plated layers of other metals, e.g. of copper. The base metal substrates can be given a variety of surface treatments depending on the final appearance desired, which in turn depends on such factors as gloss, shine, leveling, thickness etc. of the galvanic deposition of cobalt, nickel and/or iron applied the substrates.

Although electrolytic deposits of nickel, cobalt, nickel and cobalt, nickel and iron, cobalt and iron or nickel, iron and cobalt can be obtained using the above parameters, the gloss, leveling, ductility and coverage may be unsatisfactory or insufficient. for a specific application. In addition, the precipitate may be cloudy or dull and also show streaks and 'steps, scaling and poor receptivity to chromium. These conditions can especially occur after the addition of excessively large supplementary quantities of class II gloss additives or when using particularly "strong" class II gloss additives. In the case of iron-containing plating baths which also contain agents which have a dissolving effect on iron, the iron or the iron dissolving agents may also cause a loss in leveling and gloss, or they may lead to cloudy, dull or streaky deposits. According to the present invention, it has been discovered that it is possible to remedy the aforementioned disadvantages by adding or incorporating certain unsaturated cyclosulfones according to claim 1 in the plating bath. Moreover, these cyclosulfone compounds allow the use of higher than normal concentrations of class II gloss additives, thereby making it possible to achieve a higher degree of gloss and leveling without unwanted streaks, holidays, brittleness, etc.

which must normally be expected under these conditions.

It is understood that in the cyclosulfone compounds there may also be subgroups such as e.g. chloride, bromide, alkosy etc. which are compatible with the bath without themselves contributing to the action of the unsaturated cyclosulfones, but are either inert towards the plating solution or give increased dissolution in the bath of the basic sulphone.

Typical or representative compounds having the above general formula are listed below:

The unsaturated cyclosulfones used according to the present invention are unusual in that they do not act as gloss additives in themselves as class I or II gloss additives do. They should therefore not be considered as gloss additives, but rather as additives whose function in the bathroom is to overcome cloudiness, streaks, peeling, stepping and holidays. In addition, an improvement in the coverage and uniformity of the deposition can be achieved at low current density by adding these compounds to plating baths containing nickel, cobalt, nickel/cobalt, nickel/iron, cobalt/iron or nickel/cobalt/iron.

The unsaturated cyclosulfones are used in the plating bath

in concentration rations of 5-10 -6 - 5-10 -1mol/l and preferably of 1-10~<5> - 1-10~<1> mol/l.

The following examples illustrate the effect of the invention.

Comparative example

An aqueous nickel plating bath with the following composition was prepared:

A polished brass plate was scratched by a single horizontal pass of 4/0 grit emery paper to give an approx. 1 cm wide band at a distance of approx. 2.5 cm from the lower edge of the plate and parallel to it. The cleaned plate was then plated in a 267 ml Hull cell with a cell current of 2A for 10 min using the above solution and magnetic stirring.

in

The resulting nickel deposit was shiny, but showed severe streaking over the entire current density range of the sample plate. Moreover, the deposit was thin and dark in the current density range 0-120 A/m 2 and peeled off in the range from approx.

150 A/m to the edge of the test plate where the current density was highest (approx. 1200 A/m<2>). The poor physical properties of the precipitate (specifically streaking, dark areas, peeling) are due to the relatively high concentration of class II gloss additive.

_3

By adding 4.1-10 mol/l (0.5 g/l) tetrahydro-

thiophene-1,1-dioxide, (sulfolane)

to stains

ing solution and repetition of the plating experiment, a nickel precipitate was obtained which was the same as that obtained originally. Increasing the sulfolane concentration to 4.1*10 mol/l (5 grams per liter) in the plating solution and repeating the experiment also had no noticeable effect on the resulting nickel precipitation.

Example 1

An aqueous nickel plating bath was prepared and tested in the same manner as described in the first part of the comparative example. The resulting nickel precipitate exhibited the same defects as mentioned above.

By adding 3.4-10~<3> mol/l (0.4 g/l) 2,5-dihydro-

thiophene-1,1-dioxide, (sulfolene)

to spot

tering solution and repetition of the plating experiment, a nickel deposit was obtained that was uniformly shiny over the entire current density range and was free of streaks and dark areas in the low current density area and without originally observed scaling.

Example 2

An aqueous nickel plating bath was prepared and ex-

tried in the same way as indicated in the first part of the comparative example, and the precipitates showed streaks, scaling and dark areas in the area of low current density as already mentioned.

By adding 7.6.10 mol/l (1.0 g/l) 3-methyl-2,5-

i i dihydrothiophene-l-l-dioxide, (3-methylsulfolene) CH=CH-CK-CH3-SO2-CH2,

to the plating solution and repetition of the plating trial, a nickel deposit was obtained which was shiny over the entire current density range of the plate, showed good leveling (demonstrated by the elimination or filling of scratches) and was free of streaks and scaling of the deposit.

Example 3

An aqueous electrolytic nickel plating bath was prepared

and tested in the same way as in the first part of the saimen]j.qninqsekserolet.

The resulting nickel precipitate suffered from the same defects that are

mentioned earlier.

By adding 6,8.10"<3>mol/l (1.0 g/l) 2,4-dimethyl-2,4-dihydrothiophene-2,5-dihydrothiophene-1,1-dioxide, (2,4 -dimethyl-3-sulfolene) CH=C(CH^)-CH2-SO2-dH(CH3), to the plating solution and repetition of the plating experiment, a nickel deposit was obtained which was shiny over the entire current density range, and the stripes, peeling and darkness in the area with low current density was significantly reduced

severed or completely eliminated,

in

in

Example 4

An aqueous nickel/iron plating bath with

the following composition was prepared:

A polished brass plate was scratched by a single horizontal pass of No. 4/0 emery paper to give an approx. 1 cm wide band at a distance of approx. 2.5 cm from the lower edge of the plate and parallel to it. The cleaned plate was then plated in a 26 7ml well cell with a cell current of 2A for 10 min using the above solution and magnetic stirring.

The resulting nickel/iron precipitate was bright and well leveled from the area with a current density of 250 A/m 2 to the edge of the test plate where the current density was highest. In the current density range from approx. 0 to 250 A/m 2 , however, the precipitate was dark and uneven and showed step formation.

By adding 3.4.10<_3>mol/l (0.4 g/l) 2,5-dihydrothiophene-1,1-dioxide (sulfolene) to the plating solution and repeating the plating experiment, a nickel/iron precipitate was obtained which was free for dark areas in the area of low current density and the step formation mentioned above, and showed a smooth transition between the areas of medium and low current density.

Claims (10)

1. Process for the electrolytic deposition of nickel, cobalt and/or binary or ternary alloys of metals selected from the group of nickel, iron and cobalt, comprising passing current from an anode to a cathode through an aqueous, acidic plating solution containing at least one component selected from nickel compounds, cobalt compounds and iron compounds which provide nickel, cobalt and iron ions for precipitation of nickel, cobalt, nickel/cobalt alloys, nickel/iron alloys, cobalt/iron alloys or nickel/iron/cobalt alloys , for a sufficiently long time for a metal precipitate to form on the cathode, characterized in that a plating solution containing 5-10 ^ - 5-10 ^ mol/l of an unsaturated cyclosulfone with the following general structural formula is used: where , R 2 , R 1 and R 4 mean hydrogen, lower alkyl or hydroxyl. 2. Method as stated in claim 1, characterized in that a plating solution containing 2,5 dihydrothiophene-1,1-dioxide (sulfolene) is used. IN 3. Method as stated in claim 1, characterized in that a plating solution containing 3-methylsulpholene is used. 4. Method as stated in claim 1, characterized in that a plating solution containing 2,4-dimethylsulfolene is used. 5. Method as stated in claim 1, characterized in that a plating solution containing 2-hydroxysulfol is used. 6. Aqueous, acidic electrolytic plating solution for carrying out a method as stated in claim 1, the solution containing at least one component selected from nickel compounds, cobalt compounds and iron compounds which provide nickel, cobalt and iron ions for precipitation of nickel, cobalt, nickel /cobalt alloys, nickel/iron alloys, cobalt/iron alloys or nickel/cobalt/iron alloys, characterized in that the solution contains 5-10 — 6 — 5-10 — 1 mol/l of an unsaturated cyclosulfone with the following general structural formula: where R1, R2, R3 and R4 mean hydrogen, lower alkyl or hydroxyl. 7. Plating solution as stated in claim 6, characterized in that it contains 2,5-dihydrothiophene-1,1-dioxide (sulfolene). 8. Plating solution as stated in claim 6, characterized in that it contains 3-methylsulfol. 9. Plating solution as stated in claim 6, characterized in that it contains 2,4-dimethylsulfol. 10. Plating solution as stated in claim 6, characterized in that it contains 2-hydroxysulfol.