US3312604A

US3312604A - Electrodeposition of nickel

Info

Publication number: US3312604A
Application number: US318109A
Authority: US
Inventors: Wells Frederick Herbert; Worrall Peter John
Original assignee: Albright and Wilson Mfg Ltd
Current assignee: Albright and Wilson Mfg Ltd
Priority date: 1962-10-25
Filing date: 1963-10-22
Publication date: 1967-04-04
Anticipated expiration: 1984-04-04
Also published as: GB1000311A

Description

United States Patent Ofifice 3,3 12,604 Patented Apr. 4, 1967 3,312,604 ELECTRODEPOSITION F NICKEL Frederick Herbert Wells, Sutton Coldfield, and Peter John Worrall, Kidderminster, England, assignors to Albrrght & Wilson (Mfg.) Limited, Oldbury, Warwickshu'e, England, a British company No Drawing. Filed Oct. 22, 1963, Ser. No. 318,109 Claims priority, application Great Britain, Oct. 25, 1962, 40,384/62; June 17, 1963, 23,987/63 12 Claims. (Cl. 204-49) This invention relates to the electrodeposition of nickel. It is an object of the invention to provide on a basis metal a nickel electrodeposit having a satin-like finish, that is a surface which exhibts a lustrous sheen and, although bright, gives a difiuse image lacking in contrast when used as a reflecting surface. Such a finish is desirable as a decorative finish for many articles but also I as a basis electrodeposit to which there is subsequently to be applied a chromium or other further electrodeposit to provide the article with an extremely hard-wearing, smooth and bright surface.

Hitherto, a satin-like finish has been provided by mechanical treatment of the basis metal to alter its surface prior to electrodeposition of the nickel, or by sand, shot or vapour blasting of the surface of the nickel plated article.

We have now found that a nickel electrodeposit having a pleasing satin-like finish can be obtained by using an aqueous nickel electrolyte which comprises nickel sulphate and a levelling agent and to which has been added a small quantity of a water-soluble strontium salt. Such an electrolyte provides the desired satin-like finish without requiring special filtration equipment or agitation of the electrolyte during use. We have tried to produce a similar effect by the analogous use of a water-soluble calcium salt but without success and in our experience satisfactory electrodeposition to produce a satin-like finish using a Water-soluble barium salt as additive to the electrolyte is only obtained if the electrolyte is vigorously agitated using a special device in order to disperse the precipitated barium sulphate. The need to use such agitation renders the operation of the process unduly complex.

Accordingly, the present invention provides an aqueous electrolyte for the electrodeposition of nickel, which comprises nickel sulphate, a levelling agent (as hereinafter defined) and from parts per million to 1 gram per liter of strontium which has been added to the electrolyte in the form of a water-soluble salt thereof.

The invention also provides a process for the electrodeposition of nickel which comprises employing therein an electrolyte of the invention. The invention further provides articles having a nickel electrodeposit Whenever obtained by such a process.

The electrolyte of the invention comprises nickel sulphate. This may be the sole nickel salt in the electrolyte or there may be present also other nickel salts, for instance nickel chloride, fluo-borate and/or sulphamate. The total content of nickel is such as to provide a concentration of nickel between 16 and 400 grams per liter, preferably between 70 and 120 grams per liter. A particularly suitable electrolyte is one known commercially as the Watts bath. The modern variation of this contains nickel sulphate in a concentration of about 200-450 grams per liter (calculated as the hexahydrate) and nickel chloride in a concentration of 3060 grams per liter (calculated as the hexahydrate). The Watts bath also contains boric acid in a concentration of from 30 to 50 grams per liter. The present process can also be operated with an electrolyte in which the nickel chloride content is equal to or greater than the nickel sulphate content.

The present electrolyte also often contains other inorganic constituents in addition to the nickel salt or salts. Thus, there may be present one or more of the following: boric acid; ammonium salts such as ammonium or nickel ammonium sulphate; sodium sulphate, magnesium sulphate, Zinc sulphate, sodium thiocyanate, acetic acid, sulphamic acid, hydrochloric acid, fluoboric acid or sulphuric acid.

The water-soluble strontium salt added to the electrolyte is usually strontium chloride or nitrate.

The concentration of strontium provided in the electrolyte by this addition may vary from 10 parts per million to 1 gram per liter (calculated as strontium), but it is preferred that the concentration should not exceed 500 parts per million.

To provide the desired satin finish to the electrodeposit it is necessary that the electroylte also contain a levelling agent, that is an agent which causes the electrodeposit formed to be of varying thickness and to exhibit a level surface despite minor undulations in the surface of the basis metal. Any compound, the presence of which results in an electrodeposit more smooth than the surface of the basis metal, is herein termed a levelling agent. Many such agents are known for use in nickel plating electrolytes and they include coumarin, substituted coumarins such as alkyl-, alkoxyand halo-coumarins, p-sulphocinnamic acid, o-hydroxycinnamic acid, acetylenic compounds, thiourea and nitrogen-heterocyclic amines such as quinoline, isoquinoline and quinaldine compounds. There may also be employed precursors of such compounds, that is compounds which react to form a levelling agent under the conditions of operation for the electrolyte.

Many of the known levelling agents also function as brightening agents, that is the surface of the resulting electrodeposit exhibits a greater reflectance than when the agent is omitted from the electrolyte. Thus an agent which is at the same time a good levelling and brightening agent will impart specularity to the electrodeposit. However, specularity is not desired of the present invention and therefore levelling agents which are also among the most efiective of the brightening agents are much less preferred in the present invention since the brightening effect tends to supercede the satin-finish which is then only obtained on localized areas of the electrodeposit. Thus we have found that only marginally successful results of uniform satin-like finish to the electrodeposit are obtained when the present electrolytes contain acetylenic alcohols, such as butyn-l, 4-diol, or thiourea as the levelling agent since these are also brightening agents of high efliciency. The preferred levelling agents for present use are therefore only moderately-active brightening agents. The levelling agent maybe employed in the concentration conventional to its use for this purpose.

A particularly preferred levelling agent for present use is coumarin or a substituted coumarin. For such a levelling agent the optimum concentration is from 0.1 to 0.5 gram per liter. Another particularly preferred levelling agent for present use is o-benzaldehyde sulphonic acid or a Water-soluble salt thereof, especially in its optimum concentration of from 0.1 to 5 grams per liter. If desired, mixtures of levelling agents may be present provided that they do not provide too great a degree of brightening to the electrodeposit. Thus, mixtures of o-benzalde'hy-de sulphonic acid or a salt thereof and coumann or a substituted coumarin may be employed, if desired.

The electrolyte of the invention preferably also contams a carrier brightener to relieve any stress in the electrodeposit. These carrier brighteners are usually organic sulpho-oxygen compounds and do not, in general, also act as levelling agents. However, o-benzaldehyde sulphonic acid is also a levelling agent so that when it is present in the electrolyte of the invention no other carrier brightener needs to be present to relieve stress in the electrodeposit, though, if desired, some other organic sulphooxygen compound may be present as an additional carrier brightener. As carrier brighteners there may be used, for 1nstance, aromatic or unsaturated aliphatic sulphonic acids, sulphonamides or sulphonimides, for example a naphthalenesulphonic acid, allyl sulphonic acid or saccharin. The sulphonic acids are often conveniently added to the electrolyte in the form of their sodium salts. The preferred additive of this type for present use is a naphthalenetrisulphonic acid, particularly 1,3,6-naphthalenetrisulphonic acid. The carrier brightner may be present in any concentration up to saturation, but a concentration of from 1 to 10 grams per liter usually provides optimum results. Particularly advantageous results are obtained when the present electrolytes contain either o-benzaldehyde sulphonic acid or a water-soluble salt thereof as combined levelling agent and carrier brightener, or the combination of a coumarin compound as the levelling agent and a sulpho-oxygen compound as carrier brightener, especially the combination of coumarin. and 1,3,6-naphthalenetrisulphonic acid in the above-mentioned preferred proportions.

The present electrolytes also often contain surfaceactive agents, particularly those of the anionic or non-' ionic type. For instance there may be present up to 5 grams per liter, usually not more than 1 gram per liter, of such agents, particularly of sodium lauryl sulphate or a lauryl-, octylphenylor nonylphenyl-polyethylene ether alcohol.

The electrolytes of the invention normally have a pH value of less than 7, that is they are acidic electrolytes; preferably the present electrolyte has a pH value of at least 1.5 and particularly of 2.7-4.5.

The present process is a conventional one of electrodeposition of nickel using one or more anodes, which may be of nickel or of an inert material such as carbon, and making the article to be plated the cathode in the system, but in which the electrolyte employed is an electrolyte according to the present invention. However, best results are obtained from the process of the invention if it is operated at a moderately high or high current density, that is a current density of at least amps per square foot; the preferred current density for present use is one from 20 to 60 amps per square foot. The process of the invention is normally operated with a warm electrolyte, for example, at a temperature of from 30 to 60 C., though temperatures between 0 C. and 100 C. can be used if desired. The process may be carried out for any convenient period, but usually a period of from 5 to 60 minutes is sufficient to provide the preferred thickness of electrodeposit which is from 0.0001 to 0.001 inch. Greater thicknesses are possible. If desired, mild air-agitation of the electrolyte may be carried out during the electrodeposition, but such agitation is by no means essential and, if excessive, results in bright patches being obtained on the electrodeposit which, otherwise, has a satin-like finish. Indeed agitation of the electrolyte during use is preferabl yto be avoided.

After electrodeposition has been completed the plated article is washed and dried. This article has a very pleasing satin-like finish, and, if desired, may readily be polished to provide a two tone effect, that is by mechanical polishing of only part of the surface of the article to which has previously been imparted the satin-like finish.

Particularly useful results are obtained from the present invention if, after the satin-like nickel electrodeposit has been applied, the article is transferred to a second electrolyte and subjected to a further electrodeposition process, particularly chromium electrodeposition. A chromi urn-plated article prepared in this manner has an electrodeposit of chromium, whose surface is very bright and hard wearing and whose adherence to the basis metal is enhanced by the intervening nickel electrodeposit with the satin-like finish provided by the present invention. Such a combined electrodeposit has been shown to have a particularly high corrosion resistance.

The invention will now be illustrated by the following 1,3,6-naphthalenetrisulphonic acid (sodium salt) 2.0

The electrolyte was used to provide electrodeposits of nickel on test pieces of polished zinc alloy, brass and steel. The electrolyte was used at 60 C. employing a current density of 60 amps per square foot. After 20 minutes the panels were removed from the electrolyte and found to possess a nickel deposit of 0.001 inch thickness having a satin-like surface finish of high luster and sheen.

Example 2 A further sample was plated using an electrolyte of pH 3.5 having the composition:

Concentration (grams per liter) Nickel sulphate (NiSO .6H O) 312 Nickel chloride (NiCl .6H O) 78 Boric acid 43 1,3,6-naphthalenetrisulphonic acid (sodium salt) 1 Coumarin 0.2 0.5

Strontium chloride The sample plated was a polished zinc-alloy diecasting that had been given an initial electrodeposit of copper which was then followed by a satin-like nickel coating from the above mentioned bath. The thickness of the nickel coating was 0.00025 inch and was obtained by plating at 60 amps/sq. ft. for 5 minutes; the bath temperature was 50.

The nickel-plated die-casting was then itself used as basis -metal and an electrodeposit of chromium applied from a high temperature high ratio chromium electrolyte having a ratio of CrO to H 50 of -150z1 by weight employing a current density of about 300 amps/ sq. ft. at 55 C. There was obtained an electrodeposit of chromium which was extremely hard and very adherent to the underlying electrodeposit.

Example 3 An electrolyte of pH 4.5 was prepared of the composition:

Concentration (grams per liter) Nickel sulphate (NiSO .6H O) 312 Nickel chloride (NiCl .6l-I O) 78 Boric acid 43 1,3,6-naphthalenetrisulphonic acid (sodium salt) 6 Sodium lauryl sulphate 0.4

Coumarin 0.2

Strontium chloride 0.1

This electrolyte was employed to provide an electrodeposit of nickel of thickness 0.0005 inch having a satin finish on a zinc alloy diecasting to which had previously been applied an electrodeposit of copper. The temperature of the electrolyte was 60 C. and a current density of 30 amps/ sq. ft. was applied for 20 minutes.

To this nickel plated diecasting there was then applied a chromium electrodeposit as described in Example 2 which again exhibited the properties of high adherence and hardness.

Example 4 To an electrolyte of the Watts bath type having the composition there were added 20 parts per million of strontium chloride, 0.5 gram per liter of sodium o-benzaldehyde sulphonate and 100 parts per million of sodium lauryl sulphate as surface-active agent. The resulting electrolyte had a pH value of from 3.0 to 3.5.

This electrolyte was used to provide electrodeposits of nickel on test pieces of polished zinc alloy, brass and steel. The electrolyte was employed at 35-45 C. without agitation and a current density of 50 amps per square foot. After 12 minutes the panels were removed from the electrolyte and found to possess a nickel deposit of 0.0005 inch thickness having a uniform satin-like surface finish of high luster and sheen.

Example 5 To an electrolyte of the Watts bath type having the composition there were added: 30 parts per million of stronium chloride, 0.5 gram per liter of sodium o-benzaldehyde sulphonate and 100 parts per million of sodium lauryl sulphate. The pH value of the resulting electrolyte was 3.5 and it was operated at a temperature between 40 and 50 C.

This electrolyte was used to provide electrodeposits of nickel on test pieces of gilding metal and brass. At a current density of 50 amps per square foot a deposit thickness of 0.00025 inch was produced in 6 minutes Without agitation of the electrolyte. The surface had a uniform satin-like appearance of high luster.

Example 6 A satisfactory nickel electrodeposit having a satin-like surface of high luster and sheen was obtained when EX- ample 1 was repeated with the electrolyte therein used, but in which the napthalenetrisulphonate had been replaced by either saccharin or p-toluenesulphonamide, each in a concentration of 2 grams per lite-r.

Example 7 An electrolyte containing at least the same concentration of nickel chloride as nickle sulphate was prepared and had the composition:

Nickel sulphate (NiSO .6H O) grams per liter 150 Nickel Chloride (NiCl .6H O) do 150 Boric acid do 35 Coumarin do 0.2 Strontium chloride -parts per million 30 Sodium 1,3,6-naphthalenetrisulphonate,

grams per liter 1 concentration of nickel sulphate varied between and 200 grams per liter.

What we claim is:

1. In an acidic aqueous electrolyte for the electrodeposition of nickle which comprises nickel sulphate and a nickel electrodeposition levelling agent, the improvement which consists in there having been added to said electrolyte a water-soluble salt of strontium in an amount within the range of 10 parts per million to 1 gram per liter (calculated as strontium), whereby the electrolyte maybe operated to provide a nickel electrodeposit having a satin-like finish.

2. In an acidic aqueous electrolyte for the electrodeposition of nickel which comprises nickel sulphate and a nickel electrodeposition levelling agent selected "from the group consisting of coumarin, alkyl-coumarins, alkoxycoumarins, halo coumarins, o benzaldehydesulphonic acid and water-soluble o-benzaldehydesulphonate salts, the improvement which consists in there having been added to said electrolyte a water-soluble salt of strontium in an amount within the range of 10 parts per million to 1 gram per liter (calculated as strontium), whereby the electrolyte may be operated to provide a nickel electrodeposit having a satin-like finish.

3. In an acidic aqueous electrolyte of the Watts type for the electrodeposition of nickel which comprises nickel sulphate in an amount of from 200 to 400 grams per liter (calculated as the hexahydrate), nickel chloride in an amount of from 30 to 60 grams per liter (calculated as the hexahydrate), boric acid in an amount of from 30 to 50 grams per liter, and a nickel electrodeposit levelling agent which is at best a moderately-active brightening agent, the improvement which consists in there having been added to said electrolyte a water-soluble salt of strontium in an amount within the range of 10 parts per million to 1 gram per liter (calculated as strontium), whereby the electrolyte may be operated to provide a nickle electrodeposit having a satin-like finish.

4. In an aqueous electrolyte of the Watts typ'e for the electrodeposition of nickel which has a pH value within the range 2.7 to 4.5 and which comprises nickel sulphate in an amount of from 200 to 400 grams per liter (calculated as the heXahyd-rate), nickel chloride in an amount of from 30 to 60 grams per liter (calculated as the hexahydrate), boric acid in an amount of from 30 to 50 grams per liter, an organic sulpho-oxygen compound as carrier brightener and a nickel electrodeposition levelling agent selected from the group consisting of coumarin, alkylcoumarins, alkoXy-coumarins, halo-coumarins, o-benzaldehydcsulphonic acid and water-soluble o-benzaldehydesulphonate salts, the improvement which consists in there having been added to said electrolyte a water-soluble salt of strontium in an amount within the range of 10 parts per million to 1 gram per liter (calculated as strontium), whereby the eelct-rolyte may be operated to provide a nickel electrodeposit having a satin-like finish.

5. In an aqueous electrolyte of the Watts type for the electrodeposition of nickel which has a pH value within the mange 2.7 to 4.5 and which comprises nickel sulphate in an amount of from 200 to 400 grams per liter (calculated as time hex athy dmate), nickel chloride in an amount of from 30 to 60 grams per liter (calculated as the hexahydrate), boric acid in an amount of from 30 to 50 grams per liter, an organic sulpho-oxygen compound as carrier brightener and, as nickel electrodep osition leveling agent, coumatrin in an amount of from 0.1 to 0.5 gram per liter, the improvement which consists in there having been added to said electrolyte a watersoluble salt of strontium in an amount within the range of 10 per million to 1 gram per liter (calculated as strontium), whereby the electrolyte may be operated to provide a nickel electrodeposit having a satin-like finish.

6. In an aqueous electrolyte of the Watts type for the electrodeposition of nickel which as a pH value within the range 2.7 to 4.5 and which comprises nickel sulphate in an amount of from 200 to; 400 grams per liter (calculated as the hexahydrate), nickel chloride in an amount of from 30 to 60 grams per liter (calculated as the hexahydrate), boric acid in an amount of from 30 to 50 grams per liter, an organic sulpho-oxygen compound as carrier brightener and, as nickel electrodeposition levelling agent, o-benzaldehydesulphonic acid in an amount of from 0.1 to grams per liter, the improvement which consists in there having been added to said electrolyte water-soluble salt of strontium in an amount within the range of parts per million to 1 gram per liter (calculated as strontium), whereby the electrolyte may be operated to provide a nickel electrode-posit having a satin-like finish.

7. In a process for the electrodeposition of nickel on a cathode wherein there is employed an acidic aqueous electrolyte which comprises nickel sulphate and a nickel electrodeposition levelling agent, the improvement which consists in there having been added to said electrolyte a water-soluble salt of strontium in an amount within the range of 10 parts per million to 1 gram per liter (calculated as strontium), whereby there is obtained a nickel electrodeposit having a satin-like finish.

8. In a process for the electrodeposition of nickel on a cathode wherein there is employed an acidic aqueous electrolyte which comprises nickel sulphate and a nickel electrodeposition levelling agent, the improvement which consists in there having been added to said electrolyte a water-soluble salt of strontium in an amount within the range of 10 parts per million to 1 gram per liter (calculated as strontium) and in operating the said process without agitation of the said electrolyte, whereby there is obtained a nickel electrodeposit having a satinlike finish.

9. In a process for the electrodeposition of nickel on a cathode wherein there is employed an acidic aqueous electrolyte which comprises nickel sulphate in an amount of from 200 to 400 grams per liter (calculated as the hexahydrate), nickel chloride in an amount of from 30 to 60 grams per liter (calculated as the hexahydrate), boric acid in an amount of from 30 to 50 grams per liter, and a nickel electrodeposit levelling agent which is at best a moderately-active brightening agent, the improvement which consists in a there having been added to said electorlyte a water-soluble salt of strontium in an amount within the range of 10 parts per million to 1 gram per liter (calculated as strontium), whereby there is obtained a nickel electrodeposit having a satin-like finish.

10. In a process for the electrodeposition of nickel on a cathode there isemployed an aqueous electrolyte having a pH value within the range 2.7 to 4.5 and which comprises nickel sulphate in an amount of from 200 to 400 grams per liter (calculated as the hexahydrate), nickel chloride in an amount of from 30 to 60 grams per liter (calculated as the hexahydrate), boric acid in an amount of from 30 to 50 grams per liter, an organic sulpho-oxygen compound as carrier brightener and a nickel electrodeposition levelling agent selected from the group consisting of cournarin, alkyl-coumarins, alkoxyooumarins, hialoeoum arins, o benzialdehydesulphionic acid and water-soluble o-benzaldehydesulphonate salts, the improvement which consists in there having been added to said electrolyte a water-soluble salt of strontium in an amount within the range of 10 parts per million to 1 gram per liter (calculated as strontium) land in operating the said process without agitation of the said electrolyte, whereby there is obtained a nickel electrodeposit having a satin-like finish.

11. In a process for the electrodeposition of nickel on a cathode wherein there is employed an aqueous electrolyte having pH value within the range 2.7 to 4.5 and which comprises nickel sulphate in an amount of from 200 to 400 grams per liter (calculated as the hexahydrate), nickel chloride in an amount of from 30 to grams per liter (calculated as the hexahydrate), boric acid in an amount of from 30 to 50 grams per liter, an organic sulpho-oxygen compound as carrier brightener and, as nickel electrodepositionlevelling agent, coumarin in an amount of from 0.1 to 0.5 gram per liter, the improvement which consists in there having been added to said electrolyte a water-soluble salt of strontium in an amount within the range of 10 parts per million to 1 gram per liter (calculated as strontium) (and in openating the said process without agitation of the said electrolyte, whereby there is obtained a nickel electrodeposit having a satin-like finish.

12. In a process for the electrodeposition of nickel on a cathode wherein there is employed an aqueous electrolyte having a pH value within the range 2.7 to 4.5 and which comprises nickel sulphate in an amount of from 200 to 400 grams per liter (calculated as the hexahydrate), grams per liter (calculated as the hexahydrate), boric acid in an amount of from 30 to 50 grams per liter, an organic sulpho-oxygen compound as carrier brightener and, as nickel electrodeposition levelling agent, o-benzaldehydesulphonic acid in an amount of 0.1 to 5 grams per liter, the improvement which consists in there having been added to said electrolyte a water-soluble salt of strontium in an amount within the range of 10 parts per million to 1 gram per liter (calculated as strontium) and in operating the said process without agitation of the said electrolyte at a current density of fiI'OIIl 20 to 60 amps per square foot, whereby there is obtained a nickel electrodeposit having a satin-like finish.

References Cited by the Examiner UNITED STATES PATENTS 3,130,135 4/1964 Ericson 204-49 JOHN H. MACK, Primary Examiner. G. KAPLAN, Assistant Examiner.

nickel chloride in an amount of from 30 to 60

Claims

1. IN AN ACIDIC AQUEOUS ELECTROLYTE FOR THE ELECTRODEPOSITION OF NICKLE WHICH COMPRISES NICLEL SULPHATE AND A NICKEL ELECTRODEPOSTION LEVELLING AGENT, THE IMPROVEMENT WHICH CONSISTS IN THERE HAVING BEEN ADDED TO SAID ELECTROLYTE A WATER-SOLUBLE SALT OF STRONTIUM IN AN AMOUNT WITHIN THE RANGE OF 10 PARTS PER MILLION TO 1 GRAM PER LITER (CALCULATED AS STRONTIUM), WHEREBY THE ELECTROLYTE MAY BE OPERATED TO PROVIDE A NICKEL ELECTRODEPOSIT HAVING A SATIN-LIKE FINISH.