DE2417952A1 - METHOD FOR THE ELECTROVAL DEPOSITION OF NICKEL AND / OR COBALT - Google Patents

Description

PATENT LAWYERS

DR.-ING. H. FINCKE DIPL.-ING. H. BOHR DIPL.-ING. S. STAEGER

Fernrufi «24 40 40

Τα legrams: Claims Munich

Poslschockkonto: Munich 270 44-B02

Bank pre-commitment Bayer. Verainsbank Munich, account 420 404

MappoNo. ' 23 ^ 82 - Dr.K / Hö

Please state in the answer

* ■ 'CASE 998

a Munich 5, n, April 1974 Müller »street 31

M & T CHEMICALS INC.,
Greenwich, Conn. - V.St.A.

"Process for the electrodeposition of nickel and / or cobalt"

PRIORITY: April 23, 1973 - Great Britain

The invention relates to improved methods and compositions for the electrodeposition of nickel Cobalt and alloys with each other and with iron * In particular the invention relates to the use of new additives to improve the buffering capacity of galvanic nickel, cobalt and alloy baths

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Nickel and / or cobalt included, and to facilitate the electrodeposition of ferrous alloys of nickel and / or cobalt.

One of the most difficult problems in commercial nickel electroplating baths is the precipitation of basic ferric salts. The main sources for this are impurities in the nickel anode materials used, dissolving attacks from to be removed Metal parts made of iron, chemicals that are used to make up and replenish the baths, and tap water, added to supplement the evaporation losses will. If these basic iron (III) salts precipitate, especially when pH values of about 3.8 or more are reached, they tend to adhere to anode bags remain, whereby the free passage of solution between the anode and cathode compartments is disturbed, resulting in a partial Anode polarization (which in turn leads to the release of oxygen or chlorine or both, which attack and decompose organic additives and thus the behavior of the bath and increase operating costs.) The precipitates also clog pilter media, thereby reducing the Piltration rate is reduced considerably. The consequence of this is that the filters have to be cleaned and replaced frequently, and that in addition deposits with poorer quality Quality are preserved. When the concentration of the suspended Particles in the bath reach a value that is too high, then it can happen that they are electrophoretic along with the nickel are deposited, which can result in voids, dull areas, etc. · ·

In the galvanic deposition of nickel and / or cobalt from a wide variety of galvanic baths, the anode current utilization under normal operating conditions is approximately 100 %, but the cathode current utilization is only approximately

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95%, which results in the development of hydrogen at the cathode, as a result of which the hydroxyl ion concentration in the bath increases, which in turn results in an increase in the pH value. If the pH exceeds an optimal range, for example 3.8 to 4.2 for shiny nickel deposits, then the limiting current density can be reduced, that is the current density at which burnt or powdery deposits are generated on the cathode, especially on the edges or Corners or protrusions of the objects to be coated, where high current densities prevail. This makes periodic rather frequent additions of an appropriate acid, such as sulfuric acid or hydrochloric acid or sulfamic acid, necessary in order to lower the pH to a value within optimal limits.

If the anode area is not properly maintained or if excessively high currents per unit volume are used, then the anode can become partially polarized, which can result in the evolution of oxygen or chlorine (in the case of chloride-containing baths) or both at the anode. It is therefore possible that the anodic current utilization is lower than the cathodic current utilization, resulting in the accumulation of excess hydrogen ions in the resulting bath, which tends to cause the pH to fall below the optimum limits. Under such circumstances, not only will the anionically developed O ₂ or Clv destroy organic bath additives, which of course adversely affect the deposition characteristics such as gloss, but the pH must also be raised periodically to a value within recommended limits. Since this generally requires the addition of a carbonate of the metal or metals to be deposited or a hydroxide or a carbonate or dicarbonate of a cation compatible with the bath, such as Na or Ca or Sr or Ba, and since these materials are either weak are soluble or react slowly or a local precipitation

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of basic nickel salts, they cannot for obvious reasons during operation can be added directly to the galvanic bath. The usual practice is to use one or more of these materials to be introduced into the filter in portions, which is quite inconvenient, since this involves a special filter feed device is necessary and because this also disrupts the filter cake (filter aid + activated carbon, etc.) can and particles can be introduced into the bath, which roughness of the electrodeposition result can have.

It would therefore be extremely desirable to consider the bath composition could be modified so as to increase the buffer capacity of the bath to a considerable extent To be able to counteract the tendency to rise or fall in the pH value. The boric acid usually added helps the buffering of the "cathode film", i.e. the thin layer of the solution that is in the immediate vicinity of the cathode, but it gives a rather poor buffering effect for the body of the electroplating bath.

Baths that are particularly sensitive with regard to the pH value are those for the deposition of semi-glossy m or shiny cobalt that contain one or more organic additives. When the pH gets too high, i.e. a range from 3.8 to 4.2 or even higher, then there is a strong tendency that unsightly and unsatisfactory uneven, brownish colored deposits can be obtained at the upper end of the high current density range.

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The present invention was now based on the object of improving the buffering characteristics and thus the pH stability of the above-mentioned electroplating baths. A special object of the invention was to provide methods and compositions for the production of good electrodepositions which contain nickel and / or cobalt and iron, and indeed within a large concentration range of additives, without considerable amounts of basic iron (III) - Salts are precipitated. Thus, according to the invention, a method is proposed for the production of galvanic deposits which contain nickel and / or cobalt and optionally also iron, the method being carried out by passing a current from an anode to a cathode through an aqueous galvanic bath which contains cobalt compounds and / or nickel compounds and possibly also iron compounds, so that cobalt, nickel and iron ions are made available for the electrodeposition of cobalt or nickel or alloys of both or also with iron. The improvement is that in the bath 2 to 100 g / l, individually or in combination, at least one of the substances mannitol, sorbitol and dulcitol is present. Mannitol, sorbitol and dulcitol are optical isomers represented by the following formula

HIGH ₂ (CHOH) ₁₁ CH ₂ Oh

The baths can contain an effective amount of at least one of the following Substances contain:

a) primary shiners

b) secondary shiners

c) secondary auxiliary shiners

d) anti-wrinkle agents

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The substrates on which the metals according to the invention can be any "metals or metal alloys, as are commonly used in electroplating Technique, such as nickel, cobalt, nickel / cobalt alloys, copper, tin, brass, etc. Other typical Substrates from which the objects to be electroplated can be made are ferrous metals, such as e.g. steel; Copper; Tin and alloys thereof, for example with lead; Alloys of copper such as brass, Bronze, etc .; Zinc, in particular in the form of zinc die castings; these materials all have coatings from others Metals such as copper, etc. The metal substrates can have the most varied of surface properties which depends on the final look desired, which in turn depends on such factors as Gloss, brilliance, leveling, thickness etc. of the substrates applied according to the invention depends.

The term "primary shimmer" as used here refers to additional galvanic connections, e.g. Reaction products of epoxides with aeetylenic alpha-hydro xyalcohols, for example diethoxylated 2-butyne-1,4-diol or dipropoxylated 2-butyne-1,4-diol, other acetylenic substances, n-heterocycles, compounds with active sulfur, dyes, etc. Specific examples of such galvanic additives are:

1,4-di- (β-hydroxyethoxy) -2-butyne

1,4-di- (β-hydroxy- / ^ - chloropropoxy) -2-butyne 1,4-di- (S. * '-epoxypropoxy) -2-butyne

1,4-di- (β-hydroxy - # 'butenoxy) -2-but-yne 1,4-di- (2 ^f -hydroxy-4'-oxy-6 * -heptenoxy) -2-butyne NI, 2 -Dichloropropeny1-pyridinium chloride 2,4,6-trimethyl-N-propargyl-pyry.dinium bromide

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2Λ17952

N -Al Iy 1- quinaldinium-bromi d
2-butyne-1,4-diol

Propargylic alcohol

2-methyl-3-butyn-2-ol

Thiodiproprionitrile

Thiourea
Phenosafranine
Vixen

CH ₂ CH ₂ CN

CH ₂ CH ₂ CN

If it is used alone, then it may be that a primary shimmer has no visible effect on the electrodeposition. But it can also be a semi-glossy one Generate precipitation or a fine-grained precipitate. However, the best results are obtained when primary Glossers with secondary glossers and / or secondary auxiliary glossers can be used, in which case a deposit with optimal gloss, high leveling and good coverage in the low current density range, etc. is obtained.

The term "secondary brightener ¹¹ , as used here, refers to aromatic sulfonates, sulfonamides, sulfonimides, sulfinates, etc. Specific examples of such electroplating additives are:

1. Saccharin

2. Trisodium 1,3,6-naphthalene trisulfonate

3. Sodium benzene monosulfonate

4. Dibenzenesulfonimide

5 Sodium benzene monosulfinate.

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These galvanic additives, which can be used individually or in suitable combinations, have one or more of the following punctures:

1. They give semi-glossy precipitates or a sizeable one Grain refining effect against the usually matt, grainy and non-reflective precipitation from additive-free baths.

2. They act as ductilizers when used in combination can be used with other additives such as primary glossers.

3. They influence the internal stresses of precipitation, generally producing the desired compressive stresses.

4. They cause a controlled introduction of sulfur into the electrodeposition, making it more desirable Way affects the chemical reactivity, the potential differences in composite coating systems, etc. resulting in a decrease in corrosion, an increase in the protection of the base metal from corrosion, etc.

As used herein, the term "secondary auxiliary glossers" refers to aliphatic or aromatic-aliphatic olefinically or acetylenically unsaturated sulfonates, sulfonamides or sulfonimides, etc. Specific examples of such "galvanic" Additions are:

1. Sodium allyl sulfonate

2. Sodium 3-chloro-2-butene-1-sulfonate

3. Sodium ß-styrene sulfonate

4. Sodium propargyl sulfonate

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5. Monoallyl sulfamide

6. Diallylsulfamide

o ₂ s

NH-allyl

NH-allyl

7..Allylsulfonamide

These compounds, which can be used individually (as usual) or in combination are used, all have the punctures that ' in the case of the secondary glossers. They also have one or more of the following punctures:

1. You can prevent or reduce the formation of cavities (as they presumably act as' hydrogen acceptors).

2. You can use one or more secondary glosses and one or more primary glossers work together, resulting in higher gloss formation speeds and higher leveling speeds can be obtained as it is with just one or two compounds from all of the three classes:

1. primary shiners;

2. secondary glossers; and

3. secondary auxiliary glossers

is possible. · '

· ■ •

3 »You can damage the cathode surface through catalytic poisoning condition so that the rate of consumption of the additives (usually the primary shine) is reduced considerably, making operation cheaper and making control easier.

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Ions or also fall under the secondary auxiliary glossers Compounds of certain metals and metalloids, such as zinc, cadmium, selenium, etc., which, although present usually not used, can serve to increase the gloss of the deposit. Other cooperating accessories of an organic nature that can be useful are the hydroxysulfonate compounds, those described in U.S. Patent 3,697,391 are. Typical such compounds are sodium formaldehyde bisulfite, whose puncture consists in making the baths less sensitive to the concentrations of the primary glossers and to improve the insensitivity to metallic impurities such as zinc.

As used herein, the term "anti-shrinkage agent ¹¹ " refers to materials (other than the secondary auxiliary glossers) which prevent or reduce shrinkage due to the formation of gas bubbles. An anti-wrinkle agent can also act to act as a bath become less sensitive to impurities, such as oils, fats, etc., by emulsifying, dispersing or solubilizing such impurities. You thereby promote the formation of better precipitates. Anti-wrinkle agents are optional additives that, in combination with one or more of the above groups of compounds mentioned, namely primary glossers, secondary glossers and secondary auxiliary glossers, can be used.

Typical nickel-containing, cobalt-containing, and nickel and cobalt containing baths that can be used contain besides

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about 2 to 100 g / l mannitol, sorbitol or dulcitol effective Amounts from about 0.005 to 0.2 g / l of the primary brightener, about 1.0 to 30 g / l of the secondary brightener, around 0.5 to 10 g / L of the secondary auxiliary brightener and approximately 0.05 to 1 g / l of the anti-wrinkle agent.

Typical aqueous nickel-containing electroplating baths (which are used in combination with effective amounts of the above additives are the following, all concentrations being given in g / l, unless otherwise stated

Aqueous galvanic baths containing nickel

Table 1 maximum preferred minimum 500 300 200 80 45 30th 55 ^ 5 35 5 1} 3

component

Nickel sulfate

Nickel chloride

Boric acid

pH (electrometric)

If ferrous sulfate (FeSO ₂ J-TH ₂ O) is incorporated into the above bath, its concentration is about 5 g / l to 80 g / l,

A typical galvanic nickel bath containing sulphamate, which can be used according to the invention contains the following components:

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component

Nickel sulfamate

Nickel chloride

Boric acid

pH (electrometric)

When ferrous sulfate (FeSO ₂ J ^ H ₂ O) is incorporated in the above bath, its concentration is about 5 g / l to 80 g / l.

A typical chloride-free galvanic nickel bath of the sulfate type, which can be used according to the invention contains the following components:

Table II minimum maximum preferred 330 400 375 15th 60 45 35 55 45 3 5 4th

Tabel component III maximum preferred Nickel sulfate
Boric acid
pH (electrometric) minimum 500
55 400
H ₅
3-3.5 300
35
2.5

A typical chloride-free galvanic sulphamate niocel bath, which can be used according to the invention contains the following components:

Table IV maximum preferred component minimum 400
55
4th 350
45
3-3.5 Nickel sulfamate
Boric acid
pH (electrometric) 300
35
2.5

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If ferrous sulphate (FeSO ₁ , .7HpO) is used in this bath, then its concentration is approximately 5 g / l to 80 g / l.

It goes without saying that the above baths contain the compounds may contain in amounts falling outside the specified preferred miniina and maxima, but the best and most economical operation is normally achieved when the compounds in the baths in the specified quantities available. A particular advantage of the chloride-free baths of Tables III and IV above is that the deposits obtained largely free of tensile stresses are and using, high performance anodes with high Speed can be deposited.

In the following, aqueous electroplating baths containing cobalt and cobalt and nickel are indicated, which in combination one or more of the above-mentioned additives can be used in effective amounts.

Water pipes containing cobalt and containing cobalt and nickel galvanic baths

V. Cobalt bath. WH ₂ O CoSO ₂ .6H ₂ O CoCl 3 H ₃ BO Cobalt bath VI. 4.7H ₂ O CoSO NaCl 3 H ₃ BO

maximum minimum preferred 400 200 300 75 15th 60 50 ' 37 45

500 300 400 50 15 · 30th 50 37 45

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-ih-

VII. Cobalt bath with high chloride content minimum maximum preferred

₂ 0 350 150 225

₂ o 350 150 225

Η, ΒΌ, 50 37 - 45

CoCl ₂ .

VIII. Cobalt / Niekel alloy bath

NiSO ₄ .7H ₂ O 400 200 300 CoSO ₄ .7H ₂ O 225 15th 80 Ni-Cl ₂ . 6H ₂ O 75 15th 60 H ₃ BO ₃ 50 37 45 IX. Cobalt bath with exclusively Chloride content CoCl ₂ .6H ₂ O 500 200 300 H ₃ BO ₃ 50 37 45 X. SuIfamat cobalt bath Co (O ₃ SNH ₂ ) ₂ 400 200 290 CoCl ₂ .6H ₂ O 75 15th 60

50

37

When iron sulate (PeSO ₄ .7HpO) is incorporated into the above baths
then its concentration is from 5 g / l to 8-0-g / l.

Preferred bath compositions with a cobalt content can contain at least about 30 g / l CoCl ₂ .6H ₃ O and typically 20 to 50 g / l CoCl ₂ .6H ₂ O. Other compounds that contain a cation compatible with the bath (i.e. a cation that
does not interfere with the operation of the bath) which provide at least 7.5 g / l chloride ions (and preferably at least about 9 g / l chloride ions) can also be used.

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the pH of all of the exemplary aqueous nickel mentioned above, cobalt, nickel-cobalt and nickel-cobalt-iron baths, during the electrolytic deposition at 2.5 to 5.0, preferably about 3.0 to ¹ 1 , 0 are held. During operation of the bath there is normally a tendency for the pK value to increase. It can then be adjusted with acids such as hydrochloric acid or sulfuric acid, etc.

The operating temperatures of the above baths be about 30 to 70 ⁰ C, with temperatures in the range of ¹ i5 are preferred to 54 ° C.

The above baths can be stirred during the electrodeposition process by pumping the solution through a moving Cathode rod, carried out by air circulation or a combination of these measures. In applications where ferrous Alloys are deposited from baths in which the iron is predominantly in the divalent state, it is preferred a very mild agitation, for example using a moving cathode rod, to prevent the air oxidation of divalent ^ in to keep trivalent iron low.

Anodes used in the above baths can be made from the only metal deposited on the cathode, how. e.g. nickel or cobalt for the deposition of nickel or cobalt. When depositing binary or ternary alloys, such as nickel-cobalt, nickel-iron or nickel-cobalt-iron alloys, the anodes can be made of the separate metals, which are hung separately in the baths as rods, strips or small lumps in titanium baskets will. In such a case, the ratio of the individual metal anode areas is adjusted to suit the composition the desired alloy at the cathode

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speaks. When depositing binary or ternary alloys, alloys of the metals in question can also be used as anodes use, the metals being present in the weight percent, as it is the weight ratio in the cathodically deposited Alloy. These two types of anode systems generally give a fairly constant content of metal ions of the corresponding metals. If, with fixed metal ratios in the alloy anodes, the ion content If the balance is out of balance, occasional readjustments can be made by adding the appropriate corrective concentrations corresponding metal salts are made. All anodes are usually made with cloth or plastic bags the desired porosity covered to avoid the introduction of metal particles, anode slimy particles, etc. that either mechanically or electrophoretically migrate to the cathode and can result in rough cathode deposits, too little keep.

The invention will now be explained in more detail by the following examples.

example 1

A galvanic nickel bath was prepared by combining the following ingredients in water so that the given concentrations were obtained.

Concentration g / l

NiSO ,,. 7H ₀ O 409844/0914 300 NiCl ₂ .6H ₂ O 60 H ₃ BO ₃ 45 Sodium saccharinate (0.6 mol HpO) 4.0 Sodium lauryl sulfate 0.25 Iron (II) sulfate (FeSO ₂ ^ H ₂ O) 80 Sorbitol 36 PH 3.3

2Λ17952

A polished brass plate was scratched with a single stroke using a 2/0 sandpaper with a width of about 1 cm. The scratched strip was 2.5 cm from the bottom of the plate. After the plate had been cleaned, a thin layer of cyanide copper being applied in order to achieve good physical and chemical cleanliness, the plate was coated in a 267 ml Hull cell with a cell current of 2 × 10 minutes. The temperature was 50 ^° C .; Magnetic stirring was used. The resulting deposit was uniform, fine-grained, had a brilliant education _# see and an excellent ductility and only had a very weak uniform ground fog. The leveling was only moderate.

With the addition of 2.3 g / l sodium allyl sulfonate and with one Repetition of the deposition, the resulting precipitate was glossier and somewhat better leveled, which resulted in a better one Replenishment of the emery paper scraper.

With a further addition of 50 mg / 1 l, 4-di- (ß-hydroxyethoxy) -2-butyne became a brilliant, well-leveled, ductile precipitate with low tensile stress and excellent coverage obtained in the low current density range.

Example 2

Example 1 was repeated, the primary acce "tylenischer Glossy 1,4-di (ß-hydroxypropoxy) -2-butyne instead of 1,4-di- (ß-hydroxyethoxy) -2-butyne was used. Essentially the same results were obtained.

Example 5

Example 1 was repeated, with 20 mg / 1 as the primary gloss

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N-allyl-chlnaldlnium-broraid instead of 1,4-di- (ß-hydroxyethoxy) -2-butyne was used. Substantially the same results were obtained except for the degree of flattening wasn't that high.

Example 4

A zinc-cobalt-iron electroplating bath was prepared as in Example 1. However, it contained only 40 g / l iron (II) sulfate and an additional 40 g / l cobalt sulfate heptahydrate (CoSO ₁ J. 7H ₂ O). The deposition was then repeated as in Example 1, with essentially the same results being obtained.

Example 5

Example 1 was repeated, except that the sorbitol was used in the preparation the bathroom omitted vmrde. Substantially the same results were obtained when the deposition was repeated. When the solution stood, however, a cloudiness developed due to the precipitation of basic iron (III) salts, whereby the iron (III) ion was created by air oxidation of the iron (II) ion. In contrast, the solutions of the examples remained to 4 when standing, it is perfectly clear what the useful complex formation and dissolving effect of sorbitol on basic iron (III) salts demonstrated.

Example 6 " ^l

A bath was made containing the following concentration of salts to make a typical high chloride bath to produce.

Nickel chloride 200 g / l Nickel sulfate 50 g / l Boric acid 40 g / l Sorbitol - 36 g / l

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The additives of Example 1 were added in the same sequence as in Example 1, and the ferrous sulfate was added in Portions added. There were very shiny, ductile deposits with a leveling degree up to an iron (II) sulfate concentration of about 50 g / l obtained. Higher concentrations of iron (II) sulfate resulted in partially milky ones and irregular deposits partially covered with thin stripes, so that the above-mentioned value is an upper limit can be considered for a reasonable ferrous content.

Example 7

The bath of Example 1 was then subjected to an endurance test, with 4 liters of the bath under the following conditions come to use:

Galvanic cell 5 1 cell with a rectangular cross-section (13 cm χ 15 cm) made of Pyrex.

Solution volume - 4 liters, so that a solution depth of approximately 20.5 cm. Was achieved in the absence of an anode. Temperature - 55 ° C (maintained by immersing the Cell in thermostatically controlled water) stirring - moving cathode

Anode - the only bagged titanium basket containing SD nickel squares. · ■

Cathode - brass strip and polished on one side (2.5 ¹ J χ cm 20.3 cm χ 0.071 cm) and up cm immersed to a depth of 17.8. One horizontal bend was 2.54 cm from the bottom and another bend was * "Equally spaced. An interior angle of approximately 45 ° was obtained on the polished side of the cathode. The polished side was spaced from an anode It was vertically scratched in the center in a 1 cm wide bath with a 2/0 emery paper.

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Cell current - 5j0 A

Tent - The solution was electrolyzed for approximately 7 hours per day, occasionally coating cathodes for 30 minutes, to determine deposition level, uniformity, ductility, gloss (overall and in recessed areas of low current density).
Filtration - occasionally intermittently. Additives - pH was adjusted with sulfuric acid periodically as needed to keep it within the range of 3.0 to 3.0 ρ (electrometric). Periodic supplementary additions of the primary brightener and the secondary auxiliary brightener were made in order to maintain the gloss and the leveling of the precipitate Titanium baskets provided with sacks were maintained, corrective additions of iron (II) sulfate were occasionally added in order to keep the nickel and iron (II) contents of the bath largely constant.

The life test was performed for more than 1125 ampere hours using 4 1 and 5 A cell current. A small amount of basic ferric salts was formed in the form of a precipitate, but the amount was so small that it could easily be removed by continuous filtration. The main source of these basic ferric salts was the anode bags . The body of the solution remained pretty clear. A typical precipitate was obtained for 1 hour on a stainless steel substrate to form a brilliant, relatively ductile, well-leveled precipitate which was removed from the substrate and analyzed. The precipitate was found to be approximately 50 wt. # Ni and contained approximately 50 wt. % Fe.

The precipitation had the following general characteristics:

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Shine - very good and easy to maintain.

Ductility - excellent.

Inner tensions - low tension.

Leveling - pretty good (about the same as glossy ' Cobalt).

Embrittlement by hydrogen with chromium deposition - very

small amount. .

Shrinkage tendency - very low.

Smoothness of deposits - excellent.

Example 8

Example 7 was repeated using a bath without sorbitol. Within a relatively short one Electrolysis time of a few hours, the bath took on a cloudy appearance on stirring, due to the formation of basic iron (III) salts. This fact affected the appearance of the precipitates, which had a micro-roughness and had an "orange peel surface" and even took on a dull appearance at the bends of the cathode where the basic salt precipitates accumulated to a greater extent. Conditions deteriorated and the bath had to be taken out of service after 165 ampere hours of electrolysis Vverden.

The solution was then filtered, and then there was 36 g / l of sorbitol admitted. Instead of the electrolytic nickel squares in a titanium basket used in the previous test, In the bath was a rolled depolarized anode, which contained carbon and which had an electrolytic cross-section exhibited, hung. After resumption of electrolysis, excellent deposits were made for an additional 195 ampere-hours received, whereupon the deposits became dull and grainy again. During this second electrolysis, the anode had

4 0 9 8 4 4 1 0 9Y 4

adopted a dark carbon film. It was assumed, that the change in the deposition conditions occurred due to a partial anode polarization which resulted in build-up of trivalent iron in excessive concentration. This was confirmed by analysis that resulted in the presence of 3 »5 g / l trivalent iron. The notable factor was that this too was proportionate high concentration of trivalent iron the bath remained completely clear and free of basic iron precipitates was, although a build-up of anodic carbon flakes was observed at the bottom of the container. Because of of soluble trivalent iron, which gives the solution a yellow color, was the clear, translucent green in a dark olive green turned over. In addition, the solution had a milky appearance.

The pH of the solution was then adjusted (electrometric) 3 * 0 and the solution was stirred at 6O ⁰ C and <40 g of pure iron powder for 30 minutes. At the end of this time, the solution was clear green again, due to the reduction of the trivalent iron to divalent iron by the iron powder. After a filtration to remove the iron powder, the bath was again subjected to electrolysis, a bagged titanium basket now being used contained electrolytic nickel squares (which appear to resist polarization better than rolled depolarized carbonaceous nickel with the mild agitation used). The excellent bathing properties have been restored. This series of experiments undoubtedly shows the remarkable complex formation and the remarkable dissolving effect of sorbitol on trivalent iron under conditions in which normally

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the trivalent iron precipitates as a basic salt.

There are two ways in which - the buffering properties a nickel, cobalt or nickel / cobalt bath can be determined. These are as follows:

1. A known volume of electroplating bath is taken and the pH is brought to a relatively low value set. While stirring the bath, in which a system of glass electrode and calomel electrode is immersed, the connected to a pH meter to monitor pH, a solution of an alkali such as saturated sodium bicarbonate is added in small portions. Every time after the addition of a portion is allowed to take place until equilibrium has been established, after which the pH is read off. This results in a range of pH readings and volumes of alkali additions, which can be entered in a diagram to show the. To obtain the system's buffering curve. The bigger the volume the amount of alkaline solution required to change the pH from one value to another, for example from 2.0 up to 5.0, the greater the system's buffering capacity. A visual indication of the buffering capacity exerted by some Additives (for example mannitol, sorbitol, dulcitol) are obtained, is a more rapid flattening of the buffering curve; i.e. that they runs more parallel to the abscissa.

2. A bath that does not contain any additives to improve the buffering, and a bath that contains an additive to improve buffering, are ^ preferably in series, electrolyzed, with the solutions have the same volumes and at the same temperature, with the same cell current, with the same anode area, with the same Stirring, etc. are operated. The amount of time to set the

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pH is needed to the initial value is then compared at the two baths. The lower the acid consumption, the more the buffering capacity is greater.

The following examples illustrate method 1 using a Watts nickel bath with the following starting composition:

Nickel sulfate 300 s / i Winding chloride 60 g / l Boric acid g / l

Each of the baths was then used in the following examples (250 ml Volume) titrated with saturated NaHCO -.- solution at room temperature, once without and once with addition, after first adjusting the pH of the bath with sulfuric acid to a pH value considerable has been lowered below the initial value to an "initial pH value" to obtain.

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Example 9 additive ■ Example 10 0 NaHCO, - No -te NaHCO, 3 electrometric ml Resatif Electrometric pH 25 g / l sorbitol 7th 1.60 1.65 ml saturated 12th • 1.70 O 1.70 IT 13th 1.95 1 1.80 14th 2.70 "2 1.90 15th 3.00 3 2.00 16 3.25 4th 2.20 17th 3.50 5 3.12 18th 3.65 7th 3.90 19th 3.80 8th 4.20 20th 3.95 9 4.40 21 4.05 10 4.50 22nd 4.15 11 4.60 24 4.25. 12th 4.70 26th 4.35 13th 4.80 .28 4.50 14th 4.85 30th 4.65 15th 4.90 32 4.80 16 5.00 3.5 4-, 90 18th 5.05 40 5.00 20th 45 5.10 5.30 5.40

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- - 25 g / l Dulcit NaHCO ₇ Example 12 2417952 . 0 electrometric Example 11 ml saturated j
H electrometric 25 g / l 2.5 1.65 1.70 Mannitol 5l, 0 1.80 O 1.85 ml saturated NaHCO ₇ '7.5 2.00 . 2.5 2.00 pH 10.0 2.35 5.0 2.35 12.5 2.85 7.5 3.20 15.0 3.25 10.0 3.75 17.5 3.55 12.5 4.10 20.0 . 3.85 15.0 4.30 22.5 3.95 17.5 4.50 25.9 4.10 20.0 4.70 27., 5 4,3O ' 22.5 4.80 30.0 4.45 25.0 4.90 32.5 4.60 27.5 5.05 35.0 4.70 30.0 5.20 37.5 4.80 35.5 40.0 4.90 5.00

409844 / OSLU

2A17952

The following example shows that inositol, which also has the formula CgHg (OH) g, or that 1,2,3,4,5,6-cyclohexane hexol the degree of the buffering capacity, compared to the three compounds used according to the invention, namely Manitol, sorbitol and dulcit do not improve.

Example 13

25 g / l inositol

ml saturated NaHCO ₃ pH

0 1.65

2.5 1.80

5, 2.00

7.5 2.40

10.0 3.90

12.5 4.55

15.0 4.80

17.5 4.95

20.0 x 5.10

22.5 5.20

In a summary of Examples 9 to 13, the ml of saturated NaHCO- ,, consumed results in around the pH to raise from 2 to 5, the following:

1. No addition 14 ml 2. Sorbitol 25 ml 3. Dulcit 25 ml 4th Mannitol 35 ml 5. Inositol 12.5 ml

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The best buffering improvement is therefore with mannitol
preserved, whereas sorbitol and dulcitol are slightly worse. With inositol, the buffering is even worse than with the pure Watts bath.

To explain the beneficial effect of sorbitol in a Watts cobalt bath (the other conditions are the same as in Examples 9 to 13) the following examples specified:

Cobalt sulfate 300 g / l Cobalt chloride 60 g / l Boric acid 15th g / l

Example 14

without addition ml saturated NaHCO ₃ p_H

Example 15

25 g / 1 sorbitol ml saturated NaHCO ₃ p_H

0 1.60 1 1.65 3 1.85 6th 3.10 8th 4.05 9 4.30 10 4.40 11 4.50 12th 4.60 14th 4.70 16 4.80 18th 4.90 20th 5.00

0 1.65 1 1.70 3 1.75 6th 2.20 8th 2.70 10 3.20 12th 3.50 14th 3.75 16 3.95 18th 4.15 20th 4.30 22nd 4.45 24 ■ 4.55 26th 4.70 28 4.80 30th • 4.85 33 5.00 36 5.10 40 5.25

From Examples 14 and 15 it can be seen that to increase of pH from 2 to 5 approximately 16 ml without additive 'and approximately 29 ml at 25 g / l sorbitol are necessary, which illustrates an extraordinary increase in the buffering capacity by sorbitol.

To explain the beneficial effects of sorbitol on a nickel bath the sulfamate type, as is commonly used for electroforming

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is used, the following examples are given

NickelsuIfamat
Nickel chloride
Boric acid

Example 16

no addition
ml saturated NaHCO ., £ H

0
1
2
3
5
7th
10

12.5
15.0
18.0
20.0
22.0
25.0
30.0
35.0

1.65 1.70 1.75 1.80

1.85 2.00

2.15 2.35 2.85 4.05 4 * 40

4.55, 4.85 4.95 5.10

375 g / l p_H 6 g / l 1.65 37.5 g / l 1.70 Example. 17th 1.75 25 g / l sorbitol 1.80 ml saturated NaHCO-, 2.05 0 2.20 1 2.45 2 3.20 VJl 3.60 10 3.80 12.5- 4.10 15.0 4.25 20th 4.50 22.5 4.75 25th 4.95 28 5.05 30th 35 40 45 ' 50

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From Examples 16 and 17 it can be seen that, without addition, at a pH change from 2 to 5, approximately 23 ml and at 25 g / l Sorbitol 40 ml are required.

Example 18

A service life test gave 4 1 under the following conditions carried out:

Plating cell - 5 1 rectangular cross-section (13 cm χ 16 cm) made of Pyrex.

Solution volume - ¹ l, so that a solution depth in the absence of an anode of approximately 20.5 cm is obtained. Temperature - 55 ° C (maintained by immersing the cell in a thermostatically controlled water bath).

Stir - filtered air is passed through glass and a polyethylene spin directed.

Anode - the only bagged titanium basket with electrolytic nickel squares.

Cathode - Brass strip (2.54 cm by 20.3 cm by 0.071 cm) polished on one side and dipped to a depth of approximately 17.8 cm, 2,., 54 cm from the bottom, bent horizontally, and then again bent at a distance of 2.5 * 1 cm so that an interior angle on the polished side of the cathode of approximately 45 ° was obtained, with the polished surface at a distance of 10.2 cm from the anode. In addition, the polished side was provided with a 1 cm wide strip in the middle, which was scratched by means of a single run over with a 2/0 emery paper. Cell current - 5.0 amps.
Time - the solution was electr'olyzed for about 7 hours per day,

occasionally anodes were coated for 30 min Leveling, uniformity, ductility and gloss of the precipitation (i.e. in total and in the area of recesses with low current density).

The bath composition who as follows:

Nickel sulfate 300 g / l

Nickel chloride 60 g / l

Boric acid 45 g / l

Sorbitol 25 g / l

pH 4.0 electrometric

Sodium saccharinate

(0.6H ₂ O) 3.2 g / L

Sodium allyl sulfonate 2.3 g / l

Dipropoxylated 2-butyne

1,4-diol 50 mg / l

Sodium di-n-hexylsulfo-

succinate 0.25 g / l

The above solution was operated for a total of 670 ampere hours with periodic replenishment of the organic additives. At the start of the life test, the pH was found to stabilize at a fourth of about 4.3. This pH was left at this value, except that on two distant days a small amount, ie less than 5 ml, of a 1: 1 volume mixture of concentrated sulfuric acid and water was added to lower the pH to 4.3 When using an electrolysis of an average of 35 ampere hours for 7 hours per day, additions of 1: 1 sulfuric acid in amounts of 5 to 10 ml daily were required to bring the pH to a value in the desired range of 2.8 to 4, 2 bring. This

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Life testing has therefore shown that the addition of sorbitol stabilized the pH significantly and made it possible that Sulfuric acid only rarely had to be added to adjust the pH. In the appearance of the deposits or in the physical Properties, no harmful influences were noticed, from which it follows that, besides the stabilization of the pH the sorbitol was inert in the bath. Mannitol and DuIcit surrendered essentially the same effect. Sorbitol is used because of its ready availability and considerably less Cost as preferred for mannitol and dulcitol in large-scale technology.

PATENT CLAIMS

Claims (10)

PATLNIA CLAIMS ■ ( Iy method of making an electrodeposition made of nickel and / or cobalt and optionally iron which nan a current from an anode to a cathode through an aqueous acidic galvanic bath, which contains nickel compounds and / or cobalt compounds and / oaer contains iron compounds, the .Ionen for the galvanic "Deposition of nickel, cobalt, nickel / cobalt alloys, Deliver nickel / iron alloys or nickel / cobalt / iron alloys, characterized in that the Bad boric acid and 2 to 100 g / l mannitol, sorbitol and / or dulcitol are added. 2. The method according to claim 1, characterized in that the nickel compounds of nickel sulfate and nickel chloride exist. 3. The method according to claim 1, characterized in that the nickel compounds of nickel sulfamate and nickel chloride exist. 4. The method according to claim 1, characterized in that the cobalt compounds of cobalt sulfate and cobalt chloride exist. 5. The method according to claim 1, characterized in that the cobalt compounds of cobalt sulfamate and cobal ^ - chloride. 6. The method according to claim 1, characterized in that the iron compounds of iron (II) sulfate and iron (II) - 409844/0914 Chloride. 7. The method according to any one of the preceding claims, characterized in that the bath additionally one or contains several of the following additives: a) primary shiners b) secondary shiners c) secondary auxiliary shiners
• d) Anti-wrinkle agents 8. The method according to claim 7 »characterized in that the nickel compounds of nickel sulfate and nickel chloride exist.. 9. The method according to claim 7, characterized in that the additives from sodium saccharinate, sodium ally1 sulfonate, 1,4-di- (ß-hydroxyethoxy) -2-butyne and sodium lauryl sulfate consists. 10. The method according to claim 7, characterized in that the additives from sodium saccharinate, sodium allyl sulfonate, 1,4-di- (ß-hydroxypropoxy) -2-butyne and sodium lauryl sulfate exist. 4Q9844 / 09-14