NO761680L - - Google Patents

Description

The present invention concerns improved methods and bath compositions for the production of galvanic deposits and iron alloys with nickel or nickel and cobalt. More specifically, the invention concerns the use of a new additive to improve galvanic plating with ferrous alloys of nickel or nickel and cobalt.

As a result of the fact that iron and iron salts are much cheaper than nickel and cobalt; and their salts, it would be very desirable to be able to galvanically precipitate alloys of nickel or nickel and cobalt with iron where the iron content is significant, in order in this way to reduce material the costs. It has been found that of the two common forms of iron with

2+ 3+

different values, specifically Fe and Fe , the ferrous form (Fe 2+ ) is the best when plating with these alloys, although the baths can generally tolerate low concentrations of trivalent iron. The problem with plating with these iron alloys, however, has been that Fe^+, as a result of being present in too high concentrations which can occur by air oxidation or anodic oxidation of Fe 2+, is prone to precipitate as basic salts which not only to the desired extent, tend to clog anode bags and filters, but also co-precipitate so that the precipitates are unsatisfactory. Such deposits may show opacities or locally dull areas, especially on "shelf" areas, and if the concentration of suspended basic ferric salt is exceptionally high, a general formation of small elevations (micro-mourid formation) often referred to as "orange peel" may occur This problem with the precipitation of basic ferral salts has thus far made it very difficult to master an industrial galvanic precipitation of alloys of iron with nickel or with nickel and cobalt.

To overcome the problems associated with the formation of basic ferric salt precipitates, one can go two ways. One involves using a reducing agent that tries to retain essentially all of the iron as Fe 2+ . Although such reducing agents exist, most tend to be unstable, form harmful reduction products, or adversely affect the properties of the electrodeposited coatings or the general control and performance of the bath.

Another way would be to incorporate into the plating bath an additive that will make Fe 3+ soluble by complexing or chelating action. In order to be used in practice, such an addition must have the following properties: 1. It must be relatively stable against electrolysis, i.e. against reducing (cathode) and oxidizing (anode) conditions. 2. It must be compatible with other additives that are used individually or in combination as a grain refining additive or gloss additive, i.e. that it must not adversely affect the performance of these other additives. 3. It must be relatively cheap and not critical with respect to permissible concentration limits. 4. It must withstand fairly large fluctuations in the concentration of Fe in the bath.

There are some complexing compounds that can have some of the above properties, but you usually find that they lack the other properties.

It is an object of the present invention to improve galvanic depositions of alloys of nickel and iron and of nickel, cobalt and iron. A particular purpose of the invention is to provide methods and plating baths for the production of proper galvanic deposits containing iron and nickel or iron, nickel and cobalt, in a wide concentration range for the additives without significant precipitation of basic ferric salts. At the same time, the invention allows the plating of nickel and/or cobalt with a very low iron content (mostly well below 1 percent by weight, e.g. 0.025%) in the galvanic deposition as a result of iron contamination in the bath.

A preferred range for the iron content is 1-70% and a very preferred range is 5-50% iron in the precipitate.

It has been discovered that monosaccharides, oligosaccharides and polysaccharides have desirable properties, in that they can be oxidized and have a complexing effect on trivalent iron.

The present invention thus concerns a method for producing a galvanic deposit which contains nickel and/or cobalt, and which also contains iron, comprising passing current from an anode to a cathode through an aqueous, acidic plating solution containing nickel- , cobalt and/or iron compounds that provide cobalt, nickel and iron ions for galvanic deposition of

cobalt, nickel and alloys thereof and also iron alloys of cobalt and/or nickel, characterized by the presence in the solution

at least an effective amount of boric acid and at least one compound from the group of monosaccharides, oligosaccharides and water-hydrolyzable polysaccharides

in a concentration alone or in combination of 2-100 g/l and in a quantity sufficient to form a proper galvanic metal deposit on the cathode surface. The saccharides reduce it

unwanted trivalent iron to divalent iron and also prevents oxidation of divalent iron to trivalent iron. This reducing ability is largely due to the presence of aldehyde or keto groups in these saccharides.

3+ Furthermore, the saccharides together with Fe form strong complexes which remain in solution.

Typical examples of the aforementioned saccharides are:

Monosaccharides;

Glucose, fructose, xylose, arabinose, mannose, erythrose, glyceraldehyde etc.

Olgosaccharides:

Maltose, cellobiose, gentiobiose etc.

Polysaccharides;

Lactose©, starch, cellulose.

The baths may contain an effective amount of one or more of

the following additions:

a) primary gloss additive

b) secondary gloss additive

c) secondary auxiliary gloss additive, and"V

d) antipitting agent.

The substrates such as nickel, cobalt, nickel/cobalt, nickel/

iron or nickel/cobalt/iron-containing galvanic deposits according to the present invention can be applied to, can be of metal or

metal alloys of the kind that are usually supplied with galvanic deposits and used in the trade, e.g. nickel, cobalt, nickel/cobalt, copper, tin, brass etc. Other typical base metals from which objects to be plated are produced include ferrous metals, e.g. steel, copper, tin and tin alloys, e.g. with lead, alloys of copper, e.g. brass, bronze etc, and zinc, especially 1 form of castings of zinc, and all these metals can carry plating layers of other metals, e.g. copper. Gruhnmetall-

, the 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 cobalt, nickel or ferrous deposition applied to the substrates . The term "primary gloss additive ** as used in this preparation is intended to include such plating additives as, for example, the reaction products of epoxides with α-hydroxy-acetylene alcohols such as, for example, diethoxylated 2-butyne-1,4 -diol or dipropoxylated 2-butyne-1,4-diol, other acetylene compounds, M-heterocyclic compounds, active sulfur compounds, dyes, etc. Special examples of such plating additives are: 1,4-di-{B-hydroxyethoxy)-2-butyne

1,4-di-(O-hydroxy-Y-chloropropoxy)-2-butyne

1,4-di-(B~y-epoxypropoxy)-2-butyne

■ ■ ■ o • •

1,4-di-'(ω-hydroxy-Y-butenoxy)-2-butyne

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

N-1,2-dichloropropenyl-pyridinioxachlor id

2, 4,6-trimethyl-EJ-propargyl-pyridinium bromide

N-ally1-quinaldinium bromide

2-butyne-1,4-diol

propargyl alcohol

2-methyl-3-butyn-2-ol

thiodiproprionitrile

thiourea phenosafranine

fuchsin

When used alone or in combination, a primary gloss additive may have no visible effect on the galvanic deposition.

or it may have fine-grained precipitates with a semi-gloss. The best

however, results are achieved when primary gloss additives are used together with either a secondary gloss additive, one secondary gloss additive or both to obtain optimum deposition gloss, degree of gloss, smoothing, current density range for bright plating, coverage at low current density, etc.

The term "secondary gloss additive" as used in the present formulation is meant to include aromatic sulfonates, sulfonamides, sulfonimides, sulfinates, etc. Special examples of such plating additives are:

1. Saccharin

2. Trisodium 1,3,6-naphthalene trisulfonate

3. Sodium benzene monosulfonate

4. Dibenzene-sulfonamld

5. Sodium benzene monosulfinate.

Such plating additives, which can be used alone or in suitable combinations, have one or more of the following functions: 1. To obtain semi-gloss deposits or provide a significant grain refinement compared to the usually dull, matte, grain-shaped, non-reflective precipitates obtained from additive-free baths. 2. To serve as ductility agents when used together with other additives such as e.g. primary gloss rates. 3. To control internal stresses in the deposits largely by turning the stresses into desired compressive stresses. 4. To introduce regulated quantities of sulfur in the galvanic deposits in order to influence the chemical reactivity, potential differences in composite coating systems etc. to the desired extent in order to reduce corrosion and better protect the base metal against corrosion etc.

The term "secondary auxiliary gloss additive" as used in the preparation is intended to include aliphatic © or aromatic-aliphatic alkene- or acetylene-unsaturated sulfonates, sulfonamides or sulfonimides, etc. Special examples of such plating additives are:

1. Sodium allyl sulfonate

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

3. Sodium e-styrene sulfonate

<,irø—■ arwntstravl — «til fnnaf 5. Monoallyl sulfamide (H2H-S02-NH-CH2-CH==CH2)

6. Diallyl sulfamide

7. Allyl sulfonamide.

Such compounds, which can be used alone (usually) or in combination, have all the effects indicated for the secondary gloss additives, and can also have one or more of the following functions: 1. They can serve to prevent or reduce pitting ( probably by acting as hydrogen acceptors). 2. They may cooperate with one or more secondary gloss additives and one or more primary gloss additives to provide much better gloss levels and leveling than would be achievable with one and Sh or two and two of any compound selected from the following three classes:

(1) primary gloss rates

(2) secondary gloss charges and

(3) secondary auxiliary gloss additives.

3. They can affect the cathode surface by catalytic poisoning, e.g. so that the rate of consumption of interacting additives (usually of primary gloss additive) can be significantly reduced, so that the operation becomes more economical and can be better controlled.

Among the secondary auxiliary gloss additives, one can also incorporate ions or compounds of certain metals and semi-metals such as e.g. zinc, cadmium, selenium etc. which, although they are not usually used at present, have previously been used to increase the gloss of the precipitate

etc. Other synergistic additions of an organic nature that may be useful are the hydroxy-sulfonate compounds described in

US-PS 3 697 391, i.e. as a typical example sodium formaldehyde bisulphite, the function of which is to make the baths better able to withstand concentrations of primary gloss additives, increase the tolerance towards metallic contaminants such as e.g. zinc, etc.

The term "anti-pitting agent" as used herein is intended to include a material (different from and in addition to the secondary gloss additive) which serves to prevent or reduce gas pitting.

The anti-cavitation agent can also serve to make the baths more compatible with pollutants such as e.g. oil, fat etc. by an emulsifying, dispersing or dissolving effect on such contaminants and thereby promote the achievement of good galvanic deposits. Antipitting agents are optional additives that can possibly be used in combination with a primary gloss additive, a secondary gloss additive and/or a secondary auxiliary gloss additive. Preferred antipitting agents are sodium lauryl sulfate, sodium lauryl ether sulfate, and sodium alkyl sulfosuccinates.

Typical nickel-containing, cobalt-containing and nickel/cobalt-containing bath compositions that can be used in 1 combination with effective amounts of approx. 2-100 g/l of the monosaccharides, oligosaccharides and polysaccharides, and effective amounts of approx. 0.005-0.2 g/l primary gloss additive, approx. 1.0-30 g/l secondary gloss additive, approx. 0.5-10 g/l secondary gloss additive and approx. 0.05-1 g/l antipitting agents of the type specified in the description are specified below.

Typical aqueous, nickel-containing, galvanic 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.

' ■ .

Aqueous nickel-containing galvanic plating baths

The ratio between nickel ions and iron ions in this bath is in the range 1:1 - 50:1.

A typical nickel plating bath of the sul feisa t type which can be used in carrying out the present invention may contain the following components: The ratio between nickel ions and gem ions in this bath is in the range 1:1 50:1.

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

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

The ratio between nickel ions and yem ions in the previous bath is in the range 1:1-50:1.

pet will be clear that the above-mentioned baths may contain compounds in quantities that are outside the range defined by

the indicated preferred minimum and maximum values, but that the most satisfactory and economical operation is usually achieved when the compounds are present in the baths in the indicated amounts. A special advantage

by the chloride-free baths According to the above-mentioned tables III and IV, the galvanic deposits obtained can be mainly free of tensile stresses and can allow very fast plating using fast-acting anodes.

In the following, aqueous cobalt holding solutions and cobalt/nickel-containing galvanic plating baths are indicated, where the combination of effective amounts of one or more interacting additives according to the present invention will produce beneficial effects.

Aqueous cobalt-containing and cobalt/nickel-containing

galvanic plating baths

VI Cobalt bath VII Cobalt bath with high chloride content VI11 Cobalt/ nickel alloy bath IX Cobalt bath with only chloride x Sulfamate/ cobalt bath

The ratio between nickel ions and iron ions in the previous baths is in the range 1*1 - 50:1.

Preferred cobalt-containing bath compositions can contain at least approx. 30 g/l eoC<l>2<*>6H20, and typically 20-50 g/l CoCl2<*>6<H>2<0.>Other compounds containing a cation compatible with the bath (ie a cation which does not interfere with the operation of the bath), and which will provide at least 7.5 g/l of chlorine ions, Cl" (and preferably at least about 9 g/l Cl"), can also be used.

The pH value of all the preceding illuminating aqueous compositions containing nickel, cobalt, nickel and cobalt, resp. nickel, cobalt and iron, during plating, can be kept at 2.5-5.0 og

preferably 3.0-4.0. During the operation of the bath, the pH value usually tends to rise and can be regulated with the help of acids such as hydrochloric acid or sulfuric acid etc.

The working temperatures for the above mentioned baths can be between 30 and 70°C with preferred temperatures in the range from 45 to 65°C. Agitation of the above-mentioned baths during plating may consist of pumping the solution, movement of cathode rods, air agitation or combinations of these methods. For applications involving the precipitation of alloys containing iron, from baths where the iron is predominantly in divalent form, it is preferred to use very gentle agitation, i.e. by moving cathode rods, to keep the air oxidation of divalent iron to trivalent iron as low as possible.

For plating binary or ternary alloys such as nickel/cobalt, nickel/iron or nickel/cobalt/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 galvanically deposited 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 made of alloys with a fixed ratio between the metals, a certain imbalance between the metal ions in the bath should occur, adjustments can be made from time to time by adding suitable corrective concentrations of the individual metal salts. All anodes or anode baskets are usually covered in a suitable way with fabric or plastic bags of the desired 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 run-net in the galvanic deposition on the cathode.

The following examples are given to illustrate the invention.

Example 1

A galvanic plating bath for nickel and iron was prepared by mixing the following ingredients 1 water to give the indicated concentrations:

A polished brass plate was scribed by a single horizontal pass of 20/0 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. After cleaning the plate, including the application of a thin coat of copper cyanide to ensure excellent physical and chemical purity, the plate was plated in a 267' ml-'s Hull cell at a cell current of 2 A for 10 min and a temperature of 50 C under application of magnetic stirring, the resulting precipitate was uniformly fine-grained, well leveled, had a glossy appearance, and exhibited excellent ductility and good coverage in areas of low current density.

Example 2

Example 1 was repeated using 40 g/l sucrose, which is a disaccharide, instead of fructose, but with the same results.

Example 3

Example 1 was repeated using 40 g/l glucose, which is a monosaccharide, instead of fructose, but with the same results.

Example 4

Example 1 was repeated using 20 g/l of lactose, which is a disaccharide. Instead of fructose, but with the same results.

Example 5

A galvanic nickel/iron bath composition was prepared by mixing the following ingredients in water to give the indicated concentrations:

The resulting precipitate was glossy, relatively well leveled and ductile.

Example 6

A galvanic plating bath of nickel and iron was prepared by mixing the following ingredients in water to give the indicated concentrations:

The bath was filtered and subjected to a Hull cell test. The precipitate was glossy and uniform, but the ductility was poor.

Example 7

A galvanic plating bath of nickel and iron was prepared by mixing the following ingredients in water to give the indicated concentrations:

The resulting deposit was glossy, ductile and workably smooth.

Example 8

A galvanic bath composition containing nickel and iron was prepared by mixing the following ingredients in water to give the indicated concentrations:

The resulting precipitate was glossy, well leveled<p>g ductile.

Example 9

Example 8 was repeated, but the amount of FeSO 4 *7H 2 O was increased to 40 g/l. The resulting precipitate was glossy and smooth but had poor ductility.

Example 10

A galvanic nickel/iron plating bath was prepared by mixing the following ingredients in water to give the indicated concentrations:

The resulting precipitate was relatively smooth, shiny and ductile.

Example 11

Example 10 was repeated using a mixture of 10 g/l glucose and 10 g/l erythorbic acid instead of starch. The resulting precipitate was glossy, relatively smooth and ductile.

Example 12

Example 10 was repeated using a mixture of 10 g/l dextrose and 10 g/l sodium gluconate instead of starch. The resulting precipitate was glossy, ductile and well leveled.

Example 13

Example 10 was repeated using one mixture of

10 g/l glucose and 10 g/l sodium citrate. The precipitate was ductile, glossy and well leveled.

Claims (38)

1. Method of making a galvanic deposit containing nickel and/or cobalt, and also containing iron, comprising passing current from an anode to a cathode through an aqueous, acidic plating solution containing nickel, cobalt and/or iron compounds which provide ions for the precipitation of nickel, cobalt, a nickel/cobalt alloy, a nickel/iron alloy or a nickel/ cobalt/jem alloy, characterized in that in the solution there is at least an Sn compound from the group of monosaccharides, oligosaccharides and polysaccharides in a concentration alone or in combination of 2-100 g/l. 2. Method as specified in claim 1, characterized in that nickel sulfate and nickel are used as nickel compounds chloride. 3. Method as stated in claim 1, characterized in that nickel sulfamate and nickel chloride are used as nickel compounds. 4. Method as specified in claim 1, characterized in that cobalt sulfate and cobalt chloride are used as cobalt compounds. 5. Method as stated in claim 1, characterized in that cobalt sulfamate and cobalt are used as cobalt compounds chloride. 6. Method as stated in claim 1, characterized in that ferrous sulfate or ferrous chloride is used as the iron compound. 7. Method as stated in claim 1, characterized in that glucose is used as monosaccharide. 8. Method as stated in claim 1, characterized in that fructose is used as monosaccharide. 9. Method as stated in claim 1, characterized in that xylose is used as monosaccharide. 10. Method as stated in claim 1, characterized in that arabinose is used as monosaccharide. 11. Method as stated in claim 1, characterized in that mannose is used as monosaccharide. 12. Method as set forth in claim 1, characterized in that erythrose is used as monosaccharide. 13. Method as stated in claim 1, characterized in that glyceraldehyde is used as monosaccharide. 14. Method as stated in claim 1, characterized in that maltose is used as oligosaccharide. 15. Method as stated in claim 1, characterized in that cellobiose is used as oligosaccharide. 16. Method as stated in claim 1, characterized in that gentiobiose is used as oligosaccharide. 17. Method as stated in claim 1, characterized in that lactose is used as polysaccharide. 18. Method as stated in claim 1, characterized in that starch is used as polysaccharide. 19. Method as stated in claim 1, characterized in that cellulose is used as polysaccharide. 20. Aqueous plating solution for carrying out a method as stated in one of the preceding claims, containing nickel, cobalt and/or iron compounds which provide ions for the precipitation of nickel, cobalt, a nickel/cobalt alloy, a nickel/iron alloy or a nickel/cobalt/jem alloy, characterized in that the solution contains boric acid and at least one compound from the group of monosaccharides, oligosaccharides and polysaccharides in a concentration alone or in combination of 10-50 g/l. 21. Plating solution as stated in claim 20, characterized in that the nickel compounds are nickel sulfate and nickel chloride. 22. Plating solution as stated in claim 20, characterized in that the nickel compounds are nickel sulfamate and nickel chloride. 23. Plating solution as stated in claim 20, characterized in that the cobalt compounds are cobalt sulfate and cobalt chloride. 24. Plating solution as stated in claim 20, characterized in that the cobalt compounds are cobalt sulfamate and cobalt chloride. 25. Plating solution as stated in claim 20, characterized in that the iron compound is ferrous sulfate or ferrous chloride. 26. Plating solution as stated in claim 20, character 1 - characterized in that the monosaccharide is glucose. 27. Plating solution as specified in claim 1, characterized in that the monosaccharide is fructose. 28. Plating solution as stated in claim 20, characterized in that the monosaccharide is xylose. 29. Plating solution as stated in claim 20, characterized in that the monosaccharide is arabinose. 30. Plating solution as stated in claim 20, characterized in that the monosaccharide is mannose. 31. Plating solution as stated in claim 20, characterized in that the monosaccharide is erythrose. 32. ; Plating solution as stated in claim 20, characterized in that the monosaccharide is glyceraldehyde. 33. Plating solution as stated in claim 20, characterized in that the oligosaccharide is maltose. 34. Plating solution as stated in claim 20, characterized in that the oligosaccharide is cellobiose. 35. Plating solution as stated in claim 20, characterized in that the oligosaccharide is gentiobiose. 36. Plating solution as stated in claim 20, characterized in that the polysaccharide is lactose. 37. Plating solution as stated in claim 20, characterized in that the polysaccharide is starch. 38. Plating solution as stated in claim 20, characterized in that the polysaccharide is cellulose.