CA1155082A - Bright nickel plating - Google Patents

Abstract

KGW(CASE 1311)DC

BRIGHT NICKEL PLATING
Abstract of the Disclosure - In accordance with certain of its aspects, this invention relates to an improved process and composition for the preparation of nickel or nickel alloy electrodeposits which comprises passing current from an anode to a cathode through an aqueous acidic electro-plating solution containing:
(1) at least one nickel compound (2) saccharin (3) zinc ions the improvement comprising the presence of a sulfonated acetylenic compound or salts thereof, where the acetylenic bond and the sulfonate radical are connected by a carbon chain of at least one carbon atom and not more than 6 carbon atoms.

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Description

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This invention relates to improved processes and compositions for the electrodeposition of nickel and alloys thereof.
It has been found that the presence of quantities of zinc impurities tends to produce plating defects during the electrodeposition of nickel electroplates using compositions containing primary and secondary brighteners. The problem is especially acute during plating when the secondary brightener is saccharin (o-ben20yl sulfimide). In this case inadequate basis metal coverage may occur in low current density areas; unsightly striated (ribbed) deposits may occur; and dark,thin non-metallic appearing deposits may be produced which not only detract from the final appearance of the article being plated, but may also interfere with the receptivity, appearance, luster, etc. of subsequent deposits such as chromium plate.
In order to overcome the deleterious effects of zinc in the presence of saccharin, the use of sulfinic acids or hydroxy-sulfonates has been suggested.
While these compounds do reduce the problem, their use also reduces the overall brightness and levelling of the deposit. This results in having to use thicker nickel deposits or higher levels of the primary additives in order to obtain commercially acceptable deposits.

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An alternative approach has been to replace saccharin with another Class I additive, i.e., sodium benzene sulfonamide, sodium toluene sulfonate. These Class I additives while not as sensitive to zinc impurities as is saccharin, are inferior to saccharin with respect to stress reduction, luster building (in cooperation with Class II additives), sulfur contribution (especially important in duplex plating).
It is an object of this invention to provide processes and compositions for depositing electrodeposits of nickel in the presence of saccharin and zinc impurities. It is also an object of this invention to accomplish this without interfering with the brightness or levelling of the deposit.
In accordance with the present invention; there is provided in a process for the preparation of an electrodeposit which contains bright nickel which comprises passing current from an anode to a cathode through an aqueous acidic plating solution containing at least one nickel compound, 0.2 gram per liter to 10 grams per liter of saccharin, and 20 parts per million to 500 parts per million of zinc ions, the improvement comprising the presence of 0.01 gram per liter to 1.0 gram per liter of at least one sulfonated acetylenic compound or salt thereof such that the acetylenic bond and the sulfonate radical are connected by a carbon chain of at least one and not more than six carbon atoms.

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The concentrations of said compounds are (1) saccharin - 0.2-10 g/l

(2) zinc ions - 20-500 ppm

(3) sulfonated acetylenics or salts thereof - 0.01-1.0 g/l with a preferred range of (1) saccharin _ 0.5-4.0 g/l (2) zinc - 20-150 ppm (3) sulfonated acetylenics or salts thereof - .2 g/l Examples of sulfonated acetylenics of this invention, but not restricted thereto, are 2-butyne-1,4-disulfonic acid .
2-butyne sulfonic acid lS propyne sulfonic acid L-butyne-sulfonic acid : l-pentyne sulfonic acid The baths of this invention may also contain an effective amount of at least one member selected from the group : 20 consisting of:
~a) other Class I brighteners in addition to saccharin . (b) Class II brighteners : (c) anti-pitting or wetting agents.

The term "Class I brighteners" as used herein, and as described in Modern Electroplating, Third Edition, F. Lowenheim, Editor, is meant to include aromatic sulfonates, sulfonamides, sulfonimides, etc., as well as aliphatic or aromatic-aliphatic olefinically unsaturat'ed sulfonates, sulfonamides, sulfonimides, etc. Specific examples of such plating additives are:
(l) disodium 1,5-naphthalene trisulfonate (2) trisodium 1,3,6-naphthalene trisulfonate (3) sodium benzene monosulfonate

(4) dibenzene sulfonimide

(5) sodium 3-chloro-2-butene-l-sulfonate

(6) sodium ~-styrene sulfonate

(7) sodium allyl sulfonate

(8) monoallyl sulfamide (91 diallyl sulfamide (lO~ allyl sulfonamide Such plating additive compounds, which may be used singly or in suitable combinations, are desirably employed in amounts ranging from about 0.5 to lO grams per liter and provide the advantages described in the above reference and which are well known to those skilled in the art of nickel electroplating.
The term "Class II brighteners" as used herein, and as described in Modern Electroplating, Third Edition, F. Lowenheim, Editor, is meant to include plating additive compounds such as reaction products of epoxides with alpha- . .
. hydroxy acetylenic alcohols such as diethoxylated .
2-butyne-1,4-diol, N-heterocyclics, dye-stuffs, acetylenic amines, etc.
Specific examples of such plating additives are:
(1) 1,4-di-(~-hydroxyethoxy)-2-butyne (2) 1,4-di.-(~-hydroxy-y-chloropropoxy)-2-butyne (3) 1,4-di-~(~-,y-epoxypropoxy)-2-butyne llS5~1;32 (4) 1,4-di-(~-hydroxy-~-butenoxy)-2-butyne (5) 1,4-di(2'-hydroxy-4'-oxa-6'-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) butynoxy ethane sulfonic acids (14) propynoxy ethane sulfonic acids (lS) quinaldine dimethyl sulfate (16) N-allylpyridinium bromide (l?) isoquinaldyl-N-propanesulfonic acid betaine (18) isoquinaldine dimethyl sulfate (19) N-allylisoquinaldine bromide (20) 1,.4-di-(~-sulfoethoxy)-2-butyne (21) 3-(~-hydroxyethoxy)-propyne : ~ - (22) 3-(~-hydroxypropoxy)-propyne ~23) 3-(~-sulfoethoxy)-propyne (24) phenosafranin (25) fuchsin (26) propargyl amine (2.7) 1-diethylamino-2-propyne (28) 5-dimethylamino-2-methyl-3-pentyn-2-OL
(29) 1-dimethylamino-2-pentyne (30) 1-dimethylamino-2-butyne l~5S(~2 When used alone or in combination, desirably in amounts ranging from about 5 to 1000 milligrams per liter, a Class II brightener may produce no visual effect on the electrodeposit, or may produce semi-lustrous, fine-grained deposits. However, best results are obtained when Class II
brighteners are used with one or more Class I brighteners in order to provide optimum deposit luster, rate of brightening, leveling, bright plate current density range, low current density coverage, etc.
The term "anti-pitting or wetting agents" as used herein is meant to include a material which functions to prevent or minimize gas pitting. An anti-pitting agent, when used alone or in combination, desirably in amounts ranging from about 0.05 to 1 gram per liter, may also function to make the baths lS more compatible with contaminants, such as oil, grease, etc.
by their emulsifying, dispersing, solubilizing, etc. action on such contaminants and thereby promote attaining of sounder deposits. Preferred anti-pitting agents may include sodium lauryl sulfate, sodium lauryl ether-sulfate and sodium dialkylsulfosuccinates.
The nickel compounds employed for electrodepositing nickel are typically added as the sulfate, chloride, sulfamate, or fluoborate salts. The sulfate, chloride, sulfamate and fluoborate salts of nickel are employed in concentrations sufficient to provide nickel in the electroplating solutions of this invention in concentrations ranging from about 10 to 150 grams per liter.

115~ 2 The nickel electroplating baths of this invention additionally may contain fram about 30 to 60 grams per liter, preferably about 45 grams per liter of boric acid or other buffering agents to control the pH (e.g.; from about 3.0-5.0, preferably 4.0) and to prevent high current density burning.
In order to prevent "burning" of high current density areas, and provide for more even temperature control of the solution, solution agitation may be employed. Air agitation, mechanical stirring, pumping, cathode rod and other means of solution agitation are all satisfactory.
Additionally, the solutions may be operated without agitation.
The operating temperature of the electroplating baths of this invention may range from about 40C to about 70C, preferably from about 50C to 62C.
The average cathode current density may range from about 0.5 to 12 amperes per square decimeter, with 3 to 6 amperes per square decimeter providing an optimum range.
Typical aqueous nickel-containing electroplating solutions (which may be used in combination with effective amounts of cooperating additives) include the following wherein all concentrations are in grams per liter (g/l) unless otherwise indicated.
TABLE I
Aqueous Nickel-Containing Electroplating Solutions Component Minimum Maximum Preferred 4 2 75 g/1 500 g/l 300 g/l NiC12 6H2 20 g/l 135 g/1 60 g/1 H3BO3 30 g/1 60 g/l 45 g/l pH (electrometric) 3.0 5/0 4.0 1155(~f~Z

During bath operation, the p~ ffl~y normally tend to rise and may be adjusted with acids such as hydrochloric acid, sulfuric acid, etc.
Anodes used in the above baths may be electrolytic or sulfur containing nickel bars, strips or small chunks in titanium baskets. All anodes are usually suitably covered with cloth or plastic bags of desired porosity to minimize introduction into the bath of metal particles, anode slime, etc. which may migrate to the cathode either mechanically or electrophoretically to give roughness in cathode deposits.
The substrates on which the nickel electrodeposits of this invention may be applied may be metal or metal alloys such as are commonly electrodeposited and used in the art of electro-plating such as nickel, cobalt, nickel-cobalt, copper, tin, brass, etc. Other typical substrate basis metals from which articles to be plated are manufactured may include ferrous metals such as iron, steel, alloy steels, copper, tin and alloys thereof such as with lead, alloys o copper such as brass, bronze, etc., zinc, particularly in the form of zinc-base die castings; all of which may bear plates of other metals, such as copper, etc. Basis metal substrates ma~ have a variety of surface finishes depending on the final appearance desired, which in turn depends on such factors as luster, brilliance, leveling, thickness, etc. of the nickel electroplate applied on such substrates.
It is in the electroplating of zinc base die castings that the application of this invention is very useful, as die castings fall into the electroplating solution and cause high levels of zinc impurities. These impurities in the presence of 3~ saccharin cause the unsightly electrodeposits mentioned pre-viously and can result in high operating costs.

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The addition or inclusion of specified amounts of a sulfonated acetylenic compound or salts thereof, where the acetylenic bond and the sulfonate radical are connected by a carbon chain where C=1-6, to an aqueous acidic nickel electro-plating containing saccharin and zinc impurities, will result in a bright, well leveled deposit free from the previously mentioned defects.
The following examples are presented as an illustration to provide those skilled in the art of electroplating a better understanding of the various embodiments and aspects of this invention. These examples should not be construed as limiting the scope of the invention in any way.

Panel #1 Panel #2 Panel #3 1 NiS4-6H2 300 g/l 300 g/l 300 g/l 2. NiC12-6H2O 60 g/l 60 g/l 60 g/l 3. 3B 3 45 g/1 45 g/l 45 g/l 4. pH 4.0 4.0 4.0 5. Temperature 60C 60C 60C
6. Saccharin 1.8 g/l 1.8 g/l 1.8 g/l 7. Zinc Ion 100 ppm 100 ppm 50 ppm 8. Sodium Salt of Propyne Sulfonic Acid Nil 0.1 g/l Nil 9. Sodium Salt of l-Butyne Sulfonic Acid Nil Nil 0.1 g/l 10. Propargyl AlcoholO.Q075 g/l0.0075 g/l 0.0075 g/l 11. Diethoxylated 2-Butyne-l, 4-Diol 0~015 g/l 0.015 g/l 0.015 g/l

12. 2-Butyne-1,4-Diol 0.02 g/l 0.02 g/l 0.02 g/l ~1 1155~

The conditions for plating the panels from the above aqueous nickel electroplating compositions were as follows:
A zinc coated steel test panel was stripped in 50~ hydrochloric acid, rinsed and then scribed with a horizontal single pass of 4/0 grit emery polishing paper and another scribe in a similar manner with #2 grit emery polishing paper. The cleaned panel was then plated in a 267 ml Hull Cell using the aforementioned compositions for 10 minutes at 2 amps. cell current, using cathode rod agitation.

Observations Panel 1 - Shows a bright, well leveled deposit, with low current density skip plate, severe darkness and striations.
Panel 2 - Shows a bright, well leveled deposit, free from defects, over the entire current density range.
Panel 3 - Shows a bright, well leveled deposit with only a very small amount of low current density darkness.

Although this invention has been illustrated by reference to specific embodiments, modifications thereof which are clearly within the scope of the invention will be apparent to those skilled in the art.

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Supplementary Disclosure While bright nickel electrodeposits are obtained from aqueous acidic electroplating solutions containing at least one nickel compound, saccharin and up to 500 parts per million of zinc ions with the addition of at least one sulfonated acetylenic compound or salt thereof, the presence of zinc ions within a limited range, rather than being detrimental, can actually be advantageous.
In accordance with another aspect of the present invention, an improved process and composition for the prepara-tion of nickel or nickel alloy electrodeposits is provided. The process involves passing current from an anode to a cathode through an aqueous acidic electroplating solution containing the combination of at least one nickel compound, 0.2 gm/litre to 10 gm/litre of saccharin 20 parts per million to 250 parts per million of zinc ions and 0.01 gm.litre to 1.0 gm/litre of a sul-fonated acetylenic compound or salts thereof, where the acetylenic bond and the sulfonate radical are connected by a hydrocarbyl chain of at least one carbon atom and not more than 6 carbon atoms.
Zinc is well recognized as a harmful contaminant in acidic nickel plating baths. In general, bright nickel baths are considered capable of tolerating up to about 100 mg pQr liter of zinc, according to Modern Electroplating, Edited by Lowenheim, 3rd Edition, 1974, Wiley-Interscience Publication. However in the range from 20 to 250 ppm of zinc ion, in combination with the acetylenic sulfonate, enhanced brightness can be achieved. At over 500 ppm of zinc ions, the presence of zinc ion produced adverse effects and at a level of under 20 ppm the zinc level is insufficient to produce the desired result.
In the range from about 250 to 500 ppm of zinc ions, ., J

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p~e sc,-~the adverse effects of zinc ions io ncgatcd, although the enhanced brightness is not attained.
Thus concentrations of said compounds are preferably in the range of (1) saccharin _ 0.5-4.0 g/l (2) zinc - 20-250 ppm.

(3) sulfonated acetylenics or salts thereof - .2 g/l The following examples are given, by way of comparison with the preceding examples of Panel #2 in order to demonstrate the suprisingly advantageous effect of zinc ions at lower concentrations together with a sulfonated acetylenic compound in the nickel electroplating composition Panel #4 Panel #5 1. NiSO4 6H2O 300 g/l 300 g/l 2. NiC12.6H2O 60 g/l 60 g/l 3- H3BO3 45 g/l 45 g/l 4. pH 4.0 4.0 5. Temperature 60C 60C
6. Saccharin 1.8 g/l 1.8 g/l 7. Zinc lon Nil Nil 8. Sodium Salt of Propyne Sulfonic Acid Nil 0.1 g/l 9. Sodium Salt of l-Butyne Sulfonic Acid Nil Nil 10. Propargyl Alcohol 0.0075 g/l 0,0075 g/l 11. Diethoxylated 2-Butyne-1,4-Diol 0.015 g/l 0.015 g/l 12. 2-Butyne-1,4-Diol 0.02 g/l a . 02 g/l Panel 4 shows a deposit with fair brightness and levelling with a slight amount of low current density hazing.
30Panel 5 shows a deposit with good brightness and levelling. However, a comparison of Panel 5 with Panel 2 shows ,~

~sso~z that the enhanced brightness and levelling of Panel 2 is better, particularly in the high current density and low current density portions of the panel. Thus, the presence of the zinc ions in the composition for Panel #2 can be seen to be of a positive beneficial effect.

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Claims (24)

WHAT IS CLAIMED IS:

1. In a process for the preparation of an electro-deposit which contains bright nickel which comprises passing current from an anode to a cathode through an aqueous acidic plating solution containing at least one nickel compound, 0.2 gram per liter to 10 grams per liter of saccharin, and 20 parts per million to 500 parts per million of zinc ions, the improvement comprising the presence of 0.01 gram per liter to 1.0 gram per liter of at least one sulfonated acetylenic compound or salt thereof such that the acetylenic bond and the sulfonate radical are connected by a carbon chain of at least one and not more than six carbon atoms.

2. The process of Claim 1 wherein said sulfonated acetylenic is 2-butyne-1,4-disulfonic acid.

3. The process of Claim 1 wherein said sulfonated acetylenic is 2-butyne sulfonic acid.

4. The process of Claim 1 wherein said sulfonated acetylenic is propyne sulfonic acid.

5. The process of Claim 1 wherein said sulfonated acetylenic is l-butyne sulfonic acid.

6. The process of Claim 1 wherein said sulfonated acetylenic is l-pentyne sulfonic acid.

7. In an aqueous acidic electroplating solution containing at least one nickel compound providing nickel ions for electrodepositing nickel, 0.2 gram per liter to 10 grams per liter of saccharin, 20 to 500 parts per million of zinc ions, the improvement comprising the presence of 0.01 gram per liter to 1.0 gram per liter of at least one sulfonated acetylenic compound or salt thereof such that the acetylenic bond and the sulfonate radical are connected by a carbon chain of at least one and not more than six carbon atoms.

8. The composition of Claim 7 wherein said sulfonated acetylenic is 2-butyne-1,4-disulfonic acid.

9. The composition of Claim 7 wherein said sulfonated acetylenic is 2-butyne sulfonic acid.

10. The composition of Claim 7 wherein said sulfonated acetylenic is propyne sulfonic acid.

11. The composition of Claim 7 wherein said sulfonated acetylenic is 1-butyne sulfonic acid.

12. The composition of Claim 7 wherein said sulfonated acetylenic is 1-pentyne sulfonic acid.

Claims Supported by Supplementary Disclosure

13. A process for the preparation of an electrodeposit which contains bright nickel, comprising passing current from an anode to a cathode through an aqueous acidic plating solution containing at least one nickel compound, 0.2 gram per liter to 10 grams per liter of saccharin, 20 parts per million to about 250 parts per million of zinc ions, and 0.01 gram per liter to 1.0 gram per liter of at least one sulfonated acetylenic compound or salt thereof, said acetylenic compound having an acetylenic bond and a sulfonate radical connected by a hydrocarbyl chain of at least one and not more than six carbon atoms.

14. The process of claim 13 wherein said sulfonated acetylenic is 2-butyne-1,4-disulfonic acid.

15. The process of claim 13 wherein said sulfonated acetylenic is 2-butyne sulfonic acid.

16. The process of claim 13 wherein said sulfonated acetylenic is propyne sulfonic acid.

17. The process of claim 13 wherein said sulfonated acetylenic is 1-butyne sulfonic acid.

18. The process of claim 13 wherein said sulfonated acetylenic is 1-pentyne sulfonic acid.

19. An aqueous acidic electroplating solution comprising at least one nickel compound providing nickel ions for electrodeposit-ing nickel, 0.2 gram per liter to 10 grams per liter of saccharin, 20 to 250 parts per million of zinc ions, and 0.01 gram per liter to 1.0 gram per liter of at least one sulfonated acetylenic compound or salt thereof, wherein the acetylenic bond and the sulfonate radical are connected by a hydrocarbyl chain of at least one and not more than six carbon atoms.

20. The composition of claim l9 wherein said sulfonated acetylenic is 2-butyne-1,4-disulfonic acid.

21. The composition of claim l9 wherein said sulfonated acetylenic is 2-butyne sulfonic acid.

22. The composition of claim l9 wherein said sulfonated acetylenic is propyne sulfonic acid.

23. The composition of claim 19 wherein said sulfonated acetylenic is l-butyne sulfonic acid.

24. The composition of claim 19 wherein said sulfonated acetylenic is l-pentyne sulfonic acid.