US3488264A - High speed electrodeposition of nickel - Google Patents

Description

United States Patent 3,488,264 HIGH SPEED ELECTRODEPOSITION 0F NICKEL Raymond E. Bailey, Mentor, and Arthur H. DuRose, Richmond, Ohio, assignors to Kewanee Oil Company, Bryn Mawr, Pa., a corporation of Delaware No Drawing. Continuation-impart of application Ser. No. 443,077, Mar. 26, 1965. This application Sept. 27, 1968, Ser. No. 763,409

Int. Cl. C23b 5/08, 5/46 US. Cl. 20449 9 Claims ABSTRACT OF THE DISCLOSURE A process for the high speed electrodeposition of nickel comprising electrodepositing nickel on a cathode while employing an insoluble anode from a chloride and bromide free bath consisting essentially of an aqueous solution of nickel ions having a pH within the range of 2.0 to 4.5 and containing a 1,2-benzopyrone compound, during said electrodeposition said bath being rapidly passed over said cathode at a current density of at least 500 amperes per square foot and at a temperature of at least 150 F.

This application is a continuation-in-part of application Ser. No. 443,077 filed Mar. 26, 1965, now abandoned.

The present invention relates to high speed electrodeposition of nickel, cobalt, or nickel-cobalt alloys. More particularly, the invention relates to an improved process for such electrodeposition whereby smooth lustrous nickel, cobalt, or nickel-cobalt alloy is deposited on a cathode at very high current densities and temperatures while avoiding a brittle deposit.

Theg reat majority of conventional processes for electrodepositing nickel, cobalt or nickel-cobalt alloy have refrained from utilizing high current densities despite some practical advantages, such as faster plating. Depending upon the composition of the plating bath, current densities of 200 amperes per square foot or higher have resulted in so-called burning; that is, the production of nickel hydrate at the cathode. Concentration polarization is associated with such high current densities under these conditions; and whatever the cause may be, the nickel deposit has been commercially unacceptable.

Attempts to utilize higher current densitites more satisfactorily have included the use of plating baths operated at unusually high temperatures, as well as baths which contain higher conducting solutions. In particular, it has been suggested that the chloride content of the bath should be markedly increased or even that an allchloride bath should be employed to assist in the use of such high current densitiessee High Speed Nickel Plating, Pinner & Kinnaman, Monthly Review, Amer. Electroplastics Assoc, 32, 22734 (1945). Such baths, particularly when operated at high temperatures, have not proved at all satisfactory. If insoluble anodes are used, chlorine is given off, and will, of course, attack the anode as Well as the plating equipment, and since it is a poisonous gas it must be removed from the area. Furthermore, the nickel deposited from such a bath is exceedingly fine grained and although it tends to be quite hard, it also tends to be quite brittle.

Attempts to utilize a very high current density with other types of baths, particularly all-sulfate baths, have overcome some of these objections but also have been 3,488,264 Patented Jan. 6, 1970 unsatisfactory. An all-sulfate bath will produce a very coarse grained nickel deposit which tends to be more ductile than that deposited from the chloride-containing bath. But it has been very rough and not sufficiently ductile to be wholly satisfactory. In this connection, it has been observed that for the all-sulfate bath, if the pH is increased, the ductility of the nickel deposit is decreased. Thus, it has been considered necessary to use a low pH which, of course, presents difficulties.

Thus, no matter what general type of bath is employed, it is a most difficult problem to secure very high current densities under practicable plating conditions and still maintain the bath properly while producing the desired properties in the nickel deposit. In fact, these results cannot be obtained without considerable agitation in the bath since it is necessary to provide a high rate of flow of the electrolyte over the cathode surface. Theoretically, the limiting current density for a sound nickel deposit increases with rate of flow of the electrolyte. There are, of course, many practical difliculties. In addition to some discussed above, these include the high voltage needed, overheating of the electrolyte, the difliculties of anode to cathode spacing, and the problems caused by failure to maintain uniform flow of the electrolyte.

The electrodepositing of bright or semibright nickel under high current densities and high temperature conditions while at the same time obtaining a deposit which is satisfactory as to ductility, smoothness, and adhesion presents a particularly difiicult problem. Addition agents incorporated into a bath to provide a bright or semibright deposit, or to act as levelers; that is, to provide a smoother surface and to assist in hiding small imperfections in the basis metal, or both, are rendered much less effective, or in some cases completely ineffective, by the conditions of a high speed plating process. In fact, it has been stated by one authority, ClaussA Study of Variations in Certain Characteristics of Bright Nickel Deposits With Variations in Bath Temperature, Technical Proceedings, American Platers Society (1960), pp. -109, this investigation of organic addition agents certainly shows that satisfactory bright nickel deposits may be obtained at high temperatures but the efiiciencies of existing useful compounds is decidedly low when compared with the effectiveness at normal plating temperatures. It should be noted that this investigation did not utilize high current densities or high flow rates of the electrolyte; but the author noted, which has been our observation, that many common brighteners are rendered most ineffective or are completely destroyed by hot plating baths, paticularly those depending upon unsaturation for their effectiveness. The use of such addition agents is surely most desirable if bright or semibright nickel is to be obtained and they are most desirable in order to produce a grain structure of the desired type. They also should assist in producing a smooth surface; that is, they should provide some appreciable leveling effect or at least not interfere with the leveling otherwise obtainable. Under the conditions of the high speed plating process, it has not proved possible heretofore to provide addition agents capable of gaining those desired results although some have aided in one way or another to some extent.

The addition agents contemplated by the present invention, contrary to expectations, were found to enhance the brightening and leveling of the nickel deposit as compared with such efiects in a conventional nickel plating process despite the very high current densities and temperatures, as well as the high flow rate of the electrolyte across the cathode. In fact, in some instances, it has proved possible to produce a fully bright nickel deposit from a bath by utilizing these very high current densities. Contrary to expectations, the desired concentration could be maintained readily in the bath without undue loss, while obtaining a deposit of satisfactory ductility and smoothness.

Inasmuch as it is a necessary part of the present high speed plating process to obtain a high flow rate of the electrolyte, it is most desirable that contoured insoluble anodes be employed. Such anodes make it easier to provide a uniform but minimum spacing between the anode and the cathode so that more uniform current densities may be maintained across the cathode. While this result is always desirable, it is especially important in the present process in view of the high current densities employed. In addition to the substantial saving in time, this process also saves nickel since it has been shown that the recessed areas of the cathode or other parts of the cathode which would normally have a low current density, can be plated more readily. Thus, it is not necessary to build up the thickness of the plate in high current density areas to such a marked extent as is done in conventional processing.

Broadly, the instant invention comprises a high speed process for the electrodeposition of nickel, cobalt, nickelcobalt alloy wherein the metal is deposited from a chloride and bromide free bath which employs insoluble anodes. The bath is maintained at a pH in the range of 2.0 to 4.5. Coumarin or a substituted coumarin is present as an addition agent in the bath. The bath of the instant invention is operated at a temperature of at least 150 F. utilizing current densities of at least 500 amperes per sq. foot. The electroplating bath of the instant invention must also be subjected to high agitation during plating with the minimum agitation being a flow rate past the cathode of at least 300 feet per minute. Each of the above mentioned essential aspects of the instant invention will be discussed in detail in the remainder of the specification.

In the practice of the present invention, the electroplating bath composition can be varied extensively so long as the bath is maintained substantially free of chloride and bromide ions. Nickel salts such as nickel sulfate, fiuoborate, acetate, sulfamate, perchlorate, and trichloroacetate may be used for supplying nickel to the solution. However, the all sulfate solution is preferred, and one substantially free of chloride. Lead anodes can be used with the sulfate solution but not when a substantial concentration of the other anions are present. During the electrolysis, nickel is deposited at the cathode and the pH decreases. The solution may be regenerated by the addition of basic nickel compounds, such as nickel hydrate, carbonate, or oxide. It may also be regenerated by use of nickel powder or electrolytic means in auxiliary equipment. Also, semipermeable membranes have been used. Later in the instant specification, a preferred embodiment will be discussed with respect to pH which permits the most economical regeneration of nickel baths useful in the instant invention.

During the practice of the instant invention, the temperature of the plating bath is maintained above 150 F., and preferably, although not necessarily, within the range of 180 F. to 210 F. As the current is applied, the plating solution is agitated very rapidly. This may be accomplished by various well-known means, but preferably the agitation is carried out by pumping the electrolytic solution over the surface of the cathode at a rapid rate, which is at least 300 feet per minute and preferably at least 600 feet per minute. When insoluble anodes are employed, a very small spacing can be used between the anode and the cathode thus making this high flow rate easier to obtain. It is desirable, however, that a substantially uniform flow rate be maintained at the surface of the cathode, and due to turbulence, eddying, and other'fluid flow problems this may not be easily accomplished. It may even be necessary to place baffles at strategic points best learned through experience.

As stated previously, the current density in the practice of the instant invention must be greater than 500 amps per square foot. However, the maximum current density operable for a given plating operation is directly dependent on the rate of agitation or flow rate of the bath past the cathode. For example, if the flow rate past the cathode is maintained at 5 feet per second, the limiting current density in the practice of the instant invention is about 700 amps per square foot. At 22 feet per second the limiting current density is 3,000 amps per square foot whereas at a flow rate of 50 feet per second the limiting current density is 8,000 amps per square foot.

The use of insoluble anodes such as lead, carbon, graphite, platinum, platinized titanium, and lead alloyed with small amounts of tin, silver, or cobalt is a necessary part of the present invention and results in a particular advantage in the practice of the instant invention. Normally, insoluble anodes are never used in plating baths which contain organic additives, the reason being that such organic addition agents are rapidly consumed by anodic oxidation. Surprisingly, however, in the practice of the instant invention, it has been found that the anodic oxidation inherent in the use of insoluble anodes has a beneficial result in the practice of the instant invention. The coumarin or substituted coumarin addition agents used in the instant invention gradually breaks down at the cathode to form deleterious reduction products. However, these deleterious reduction products are controlled and maintained at a harmless level due to the anodic oxi dation effected at the insoluble anode. The exact mechanism is not known with certainty but it is known that melilotic acid is formed and its harmful effects on the plating process are avoided whether it be by oxidation of the harmful acid at the anode which destroys side chains and gives off CO or whether it polymerizes the melilotic acid so that the standard activated carbon treatment of such bath removes the same. Under ordinary plating conditions, the deleterious product formed at the cathode in baths containing a coumarin or derivative thereof will accumulate to a concentration from about 0.025 M and begins to have harmful effects at about 0.005 M. Under the high speed conditions of the instant invention utilizing insoluble anodes in a substantially chloride free bath, these deleterious reduction products are destroyed at the anode and accumulate to a concentration of only about 0.001 to 0.002 M.

Coumarin may be used as a leveling and brightening agent under the above described high plating speed conditions which involve high temperatures, high agitation rates, insoluble anodes, and chloride free nickel solutions. However, because of these conditions coumarin has a higher than normal consumption rate. Because of the high temperature, the volatilization of coumarin is higher than would be desired. Therefore, the use of leveling agents which have a lower electrolytic consumption rate and/or volatilization rate would be advantageous. We have found that certain 1,2-benzopyrone compounds have these properties. For example, the volatility of 3-chlorocoumarin is not appreciably less than that for coumarin but the electrolytic consumption rate is about 25% less than that for coumarin. Methyl-coumarin has about the same electrolytic consumption rate as coumarin but a lower volatility. Acetylcournarin has both a lower electrolytic consumption rate and lower volatility.

The substituent groups may be on either the aromatic ring or the heterocyclic ring of the coumarin molecule. The substituent groups may be halogen, acetyl, hydroxy, hydroxymethyl, hydroxyethyl, methoxy, ethoxy, acetamino, N-formylamino, propargyl, cyano, methyl, ethyl, dirnethylamino, or diethylamino. Acidic substituents, such as carboxy, sulfonate, and sulfonamide groups are not Substituted 1,2-benzopyrone Moles per liter (1) B-chIorocoumarin (bromo, iodo, fluoro) 0. 0002-0. 003 (2) 3-acetylcoumarin 0. 0002-0. 003 (3) dacetylaminocournarin 0. 0002-0. 002 (4) 3-hydroxycoumarin 0. 0002-0. 002 (5) 3-cyanocoumarin 0. 0002-0. 002 (6) 3- or 4-rnethyl coumarin 0. 0002-0. 003 (7) dmethyl coumarin 0. 0002-0. 003 (8) 4,8-dimethylooumarin 0. 0002-0. 003 (9) 7-diethylamino-4-methyl 0. 0002-0. 002 (10) G-hydroxycoumarin 0.001 -0.004 (11) 6(1-glucoseamino) couma 0. 0002-0. 002 (12) 6-hydroxymethylcoumarin. 0.0002-0003 (13) S-hydroxyethylcoumarin 0. 0002-0. 003 (14) 7-methoxycoumarin 0. 0002-0. 003 (15) B-ethoxycoumarin 0. 0002-0. 003

In order that those skilled in the art may better understand how the present invention may be carried into effect, the following examples are provided by way of illustration, but not of limitation. Unless otherwise specifically indicated all temperatures are in degrees centigrade and all parts and percentages are by weight.

EXAMPLE I Two solutions containing 50 ounces per gallon of nickel sulfate and 6 ounces per gallon of boric acid were stirred uniformly at a temperature of 185 F. One solution contained 0.0004 mole per liter of coumarin and the other 0.0004 mole per liter of 3-chlorocoumarin, The solution surface area was 27 square inches. The loss of coumarin by volatilization was 0.001 mole per liter per 1,000 hours and the loss of 3-chlorocoumarin was 0.0008 mole per liter per 1,000 hours. When the solution was electrolyzed at 1,000 amperes per square foot, the consumption rate of chlorocoumarin was markedly less than that of coumarin, being at least 25 percent less.

Using the above solution but employing instead of 3- chlorocoumarin, the compounds numbered 2, 3, and 8 of Table I, no measureable volatilization loss of the addition agent was found.

EXAMPLE II A vinyl plastic sheet 12" x 16" was silvered by a common reduction method and rinsed. It was then placed in a rectangular horizontal cell and clamped into place so that it was one inch above a lead anode of similar size. A solution containing 50 ounces per gallon of nickel sulfate, 6 ounces per gallon of boric acid, and 0.005 gram per liter of acetylaminocoumarin at about 150 F. was pumped through the cell at a speed of about 400 feet per minute. The pH of the solution was 3.5 and was maintained at approximately this point by feeding nickel carbonate into an auxiliary tank. Electrolysis was started at 100 amperes per square foot for two minutes and then increased to 1,000 amperes per square foot for nine minutes. The deposit was approximately 7 mils in thickness and was semibright. However, it was burned in some areas.

The same experiment was conducted at 160 F. and 800 feet per minute, and in this instance the nickel deposit was considerably more ductile and no burning was observed.

Utilizing a set of conditions similar to that described in Example II above and utilizing a temperature of 160 F, and 500 feet per minute for the rate of flow of the electrolyte; but employing 0.1 gram per liter of 7-diethylamino-4-methyl coumarin as the addition agent, the deposit was bright-semibright but slightly brittle. The addition of 0.1 gram per liter of trichloroethoxy ethanol made the deposit somewhat brighter and more ductile.

EXAMPLE III One gallon of a Watts nickel solution containing 0.2 gram per liter of 3-chlorocoumarin was operated at F. and 600 amperes per square foot for 600 ampere hours with 1%." rotating brass cylindrical cathode having a dimeter of 1%". An anode composed of nickel was so configured as to operate at an average current density of 50 amperes per square foot. The addition agent was maintained at 02:0.1 gram per liter. At the end of this period, the build-up of the reduction products of the addition agent (principally melilotic acid) had become 0.8 gram per liter. For this reason the nickel deposit was not fully semibright.

An experiment similar to that of Example In in an all sulfate bath was performed and a platinized titanium anode was used; that it, an insoluble anode. As a result the breakdown products of the addition agent reached equilibrium at about 0.2 gram per liter and the deposit was fully semibright.

As stated earlier in the application, the plating bath of the instant invention must be maintained in the pH range of about 2.0 to 4.5. In an plating bath employing the present invention, the bath should be bufiered so that the pH remains relatively constant during operation. When operating at pHs above approximately 3.0, it is beneficial to use boric acid to regulate the pH. The presence of the boric acid in addition to affecting pH appears to have an effect on the ductility and brightness of the deposit and is beneficial above a pH 3.0. At a pH of 4.0 and above, boric acid is necessary to eliminate burning of the deposit unless the agitation rate is extremely high.

The preferred pH range is between 2.5 and 3.2. Boric acid will not buffer in this pH range and thus it is necessary to utilize an acid having a high buffer capacity in this pH range. Such buffers would include any acid having a pK value of between 2.0 and 4.85. Of course, these same buffering agents could be used at the other pH ranges operable in the instant invention. The concentration of the buffering agent used can vary from approximately 1 to 10 grams per liter depending of course on the extent of use of the bath and the buffering capacity desired. Typical buffers and their buffering concentrations are as follows.

When operating in the preferred pH range or lower, an additional advantage is obtained by the practice of the instant invention. When operating a chloride free nickel solution such as a nickel sulfate bath with insoluble anodes, the pH drops and the nickel content of the solution also decreases. It is therefore necessary to replenish the nickel and at the same time raise the pH to obtain uniform operating conditions. The nickel supply can be replenished by the use of nickel hydrate, nickel oxide, nickel carbonate, nickel metal powder or electrolytic means using anodes in an auxiliary tank. At a given pH the dissolution rate of nickel hydrate or commercial nickel carbonate is relatively fast compared to nickel oxide or metal. However, the cost of the hydrate 7 and. carbonate is considerably higher than that of the metal or oxide.

It is therefore desirable to operate under conditions which will effect more rapid dissolution of the metal or oxide. The higher the hydrogen ion content (lower pH) the faster the metal or its oxide will dissolve. Therefore, by using the buffers of the instant invention, the pH of the solution is maintained in the pH range wherein the metal and the oxide will readily ionize and there is no need to use the more expansive nickel hydrate or nickel carbonate. Also the buffering agents tend to maintain the pH at the same value and therefore permit easily obtained uniform operating conditions.

To further illustrate the present invention, various examples are given in the following tables using various buffering agents. The operating conditions of the plating bath in the following examples consisted of 52 oz. per gallon of nickel sulfate at a cathode current density of 1,000 amperes per square foot and a temperature maintained at 180 F.

or a substituted coumarin compound in a concentration range of approximately 0.05 to about 0.5 gram per liter. The preferred concentration of the coumarin compounds are between 0.1.and 0.3 gram per liter.

It has been stated earlier in the specification that in the lower pH rangebuffering agents having a pK value between 2.0 and 4.85 are preferred and should also be pointed out that along with such buffering agents boric acid may be added as a secondary buffer and in such cases the concentration range of the boric acid can vary from preferably 1-3 oz; per gallon.

We claim:

1. A process for the high speed electrodeposition of nickel comprising electrodepositing nickel on a cathode while employing an insoluble anode from a chlorine and bromine ion free bath consisting essentially of an aqueous solution of nickel sulfate having a pH within the range of 2.0 to 4.5 and containing a 1,2-benzopyrne compound, during said electrodeposition said bath being passed at least 300 feet per minute over said cathode at Addition Agents pH Ductility Appearance (1) N0 buffer 2. 8-2. 4 Dull S.B. (2) N0 bufier 4. 0 Burned and exfoliated. (3) Boric acid 5 oz./gal 4. 0 5 Grey. (4) Boric acid 5 oz./gal 2. 8-2. 4 05-. 15 Dull S.B. (5) Boric acid 5 oz./gal. plus .2 g/l. coumar 2.5 5 S.B. and leveling. (6) Na citrate 6.8 g./i 2. 5 5 Grey. (7) Na citrate 6.8 g./l. plus .2 g./l coumarin. 2. 5 5 S.B. and leveling. (8) Na citrate 6.8 g./l. plus .2 g./l. coumarin. 3. 8 06 Bt. With 81. burning.

2.5 .3 Dull S.B.

2. 5 5 S.B. and leveling. 3. 3 5 Bt. S.B. and leveling. 3. 8 04 Do. 3.8 5 Do. 2. 5 5 S.B. 2. 5 5 S.B. and leveling. 3. 8 08 Bt. S.B. with burning. (17) Acetic acid 2 cc./l 2. 5 4 S.B. (18) Acetic acid 2 cc./l plus .2 g./l. coumarin 2. 5 5 S.B. and leveling. (19) o-Phthalic acid 3 g./l 2. 5 5 Grey. (20) o-Phthalic acid 3 g./l plus .2 g./l. coumarin 2. 5 5 S.B. nd leveling. (21) o-Phthalic acid 3 g./l. plus 2 g./l. courmarin p 2. 5 5 Bt. S.B. leveling. (22) Boric acid 5 oz./gal. plus .25 g./l. butynediol. 2. 5 07 Bt. S.B. (23) n-Butyric acid 4 g./l 2. 5 5 S.B. (24) n-Butyric acid 4 g./1. plus .2 g./l. coumarin 2. 5 5 S.B.- and leveling. (25) Formic acid 3 cc./l 2. 5 25 S.B. (26) Formic acid 3 cc./1. plus .2 g./l. coumarin- 2. 5 5 S.B. and leveling. (27) Ni(BF4)z, 4.0 g./l 2. 6 07 Bt. S.B. (28) Nl(BFa)2, 4.0 g./l. plus .2 g./l. coumarin 2. 6 5 Bt. S.B. and leveling. (29) KF'2H20, 2 g./l 2v 5 .3 Dull .B. (30) KF-2H2O, 2 g./l. plus .1 g./l. butynediol. 2. 5 25 S.B. with leveling. (31) KF-2H1O, 2 g./l. plus .1 g./l. butynediol plus 2 g 2. 5 Bt. S.B. with leveling. (32) o-Phthalic acid 3 g./l 2. 5 5 Grey. (33) o-Phthalic acid 3 g./l. plus .2 g./l. oi fi-acetamide coumarin 2. 5 5 S.B. with leveling.

In the ductility values given in the above table, the value .5 indicates .5 or better; S.B. indicates semi-bright; Bt. indicates bright and s1. indicates slight.

As can be noted from the examples given in the a v table in addition to the presence of coumarin and a bulfering agent, certain unsaturated compounds may also be included in the plating bath and result in brighter electroplate. Typical such unsaturated materials include bi (fl-hydroxyethoxy butyne-Z), diethyleneglycolmonopropargyl ether and butynediol-1,4. These materials may be present in a concentration from about 0.005 to 0.5 gram per liter. The preferred concentration of the butynediol is between about 0.2 and 0.3 gram per liter with a maximum utility appearing at a concentration of .25 gram per liter. The bis-(B-hydroxyethoxy butyne-2) and diethyleneglycolmonopropargyl ether are present preferably in concentrations from 0.1 to 0.3 grams per liter. Maximum brightening appears when using bis-(B-hydroxyethoxy butyne-2) at a concentration of about 0.1 gram per liter while with diethylene glycolmonopropargyl ether maximum brightening appears to coincide with a concentration of 0.15 gram per liter. Such concentration of these additional brightening agents may be added to the plating h f the nstant invention which contains a coumarin a current density of at least 500 amperes per square foot and at a temperature of at least F., said compound having a boiling point greater than about 290 C. and a melting point greater than about 70 C.

2. A process for the high speed electrodeposition of nickel comprising electrodepositing nickel on a cathode while employing an insoluble anode from a chlorine and bromine ion free bath having a pH within the range of 2.0 to 4.5 consisting essentially of an aqueous solution of nickel sulfate and containing an addition agent selected from the group consisting of 3-chlorocoumarin, 3-acetylcoumarin, 6-acetylaminocoumarin, 3-hydroxycoumarin, 3-cyanocoumarin, 3- or 4-mcthyl coumarin, 6- methyl coumarin, 4,8-dimethyl coumarin, 7-diethyl-amino- .4-n1ethyl coumarin, 6-hydroxycoumarin, 6-(l-glucoseamino) coumarin, -6-hydroxymethyl coumarin, S-hydroxyethyl coumarin, 7-methoxycoumarin, and S-ethoxycoumarin, during said electrodeposition said bath being passed at least 300 feet per minute over said cathode, at a current density of at least 500 amperes per square foot at a temperature of at least 150 F.

3. A process for the high speed electrodeposition of nickel comprising electrodepositing nickel on a cathode while employing an insoluble anode from a chlorine and bromine ion free bath having a pH Within the range of 2.0 to 4.5 consisting essentially of an aqueous solution of nickel sulfate and containing an addition agent selected from the group consisting of 0.0002 to 0.003 mole per liter of 3-chlorocoumarin, 0.0002 to 0.003 mole per liter of 3-acetylcoumarin, 0.0002 to 0.002 mole per liter of 3-hylroxycoumarin, 0.0002 to 0.002 mole per liter of 6-acetylaminocoumarin, 0.0002 to 0.002 mole per liter of 3-cyanocoumarin, 0.0002 to 0.003 mole per liter of 3- or 4-methyl coumarin, 0.0002 to 0.003 mole per liter of 6-methyl coumarin, 0.0002 to 0.003 mole per liter of 4,8-dimethyl coumarin, 0.0002 to 0.002 mole per liter of 7-diethylamino-4-methyl coumarin, 0.001 to 0.004 mole per liter of 6-hydroxycoumarin, 0.0002 to 0.002 mole per liter of 6-(1-glucoseamino) coumarin, 0,0002 to 0.003 mole per liter of 6-hydroxymethyl coumarin, 0.0002 to 0.003 mole per liter of 8-hydroxyethyl coumarin, 0.0002 to 0.003 mole per liter of 7-methoxycoumarin, and 0.0002 to 0.003 mole per liter of S-ethoxycoumarin, said bath being subject to high agitation so that the bath is rapidly passed over the surface of the cathode at a rate equivalent to at least 600 feet per minute, is supplied at a current density of at least 500 amperes per square foot and a temperature of at least 150 F.

4. A process for the high speed electrodeposition of nickel comprising electrodepositing nickel on a cathode while employing an insoluble anode from a chlorine and bromine ion free bath having a pH within the range of 2.0 to 4.5 consisting essentially of an aqueous solution of nickel sulfate and containing an addition agent selected from the group consisting of 0.0002 to 0.003 mole per liter of 3-chlorocoumarin, 0.0002 to 0.003 mole per liter of 3-acetylcoumarin, 0.0002 to 0.002 mole per liter of 6-acetylcoumarin, 0.0002 to 0.002 mole per liter of 3- hydroxycoumarin, 0.0002 to 0.002 mole per liter of 3- cyanocournarin, 0.0002 to 0.003 mole per liter of 3- or 4-methylcoumarin, 0.0002 to 0.003 mole per liter of 6- methyl coumarin, 0.0002 to 0.003 mole per liter of 4,8- dimethyl coumarin, 0.0002 to 0.002 mole per liter of 7-diethylamino-4-methyl coumarin, 0.001 to 0.004 mole per liter of 6-hydroxycoumarin, 0.0002 to 0.002 mole per liter of 6-(l-glucoseamin0) coumarin, 0.0002 to 0.003 mole per liter of 6-hydroxymethyl coumarin, 0.0002 to 0.003 mole per liter of 8-hydroxyethyl coumarin, 0.0002 to 0.003 mole per liter of 7-methoxycoumarin, and 0.0002 to 0.003 mole per liter of 8-ethoxycoumarin, said bath being passed over the surface of the cathode at a rate of at least 600 feet per minute at a current density in excess of 1,000 amperes per square foot and at a temperature in the range of about 180 to 210 F.

5. A process for the high speed electrodeposition of nickel comprising electrodepositing nickel on a cathode while employing an insoluble anode from a chlorine and bromine ion free bath having a pH within the range of 2.0 to 4.5 consisting essentially of an acidic aqueous solution of nickel sulfate and containing a 1,2-benzopyrone compound having a boiling point greater than 290 C. and a melting point greater than about 70 C., said electrodeposition being further characterized in that the bath is subject to high agitation such that a flow rate at the cathode of at least 300 feet per minute is produced and the current density at the cathode is at least 500 amperes per square foot and the bath temperature is at least 150 F.

6. A process for the high speed electrodeposition of nickel comprising electrodepositing nickel on a cathode while employing an insoluble anode from a chlorine and bromine ion free bath consisting essentially of a buffered aqueous solution of nickel ions having a pH within the range of 2.0 and 4.5 and containing a 1,2-benzopyrone compound, said buffering being produced by a buffer effective in the pH range of 2.0 to 4.0, during said electrodeposition said bath being passed over said cathode at a rate of at least 300 feet per minute while employing a current density of at least 500 amperes per square foot and operating said bath at a temperature of at least F.

7. A process for the high speed electrodeposition of nickel comprising electrodepositing nickel on a cathode while employing an insoluble anode at current densities of at least 500 amperes per square foot at the cathode under high agitation conditions wherein the flow rate past the cathode is at least 300 feet per minute from a chlorine and bromine ion free bath consisting essentially of an aqueous solution of nickel ions having a pH within the range of 2.5 to 3.2 and containing a 1,2-benzopyrone compound along with a buffering agent capable of buffering said bath in the pH range of 2.5 to 4.0 which has a pK value in the range of 2.0 to 4.85, said bath being maintained during said electrodeposition at a temperature of at least F.

8. A process for the high speed electrodeposition of nickel comprising electrodepositing nickel on a cathode while employing an insoluble anode at current densities of at least 500 amperes per square foot at the cathode under high agitation conditions wherein the flow rate past the cathode is at least 300 feet per minute from a chlorine and bromine ion free bath consisting essentially of an aqueous solution of nickel ions having a pH within the range of 2.5 to 3.2 and containing between about 0.05 and 0.5 gram per liter of a 1,2-benzopyrone compound along with from 1 to 10 grams per liter of a buffering agent capable of buffering said bath in the pH range of 2.5 to 4.0 which has a pK value in the range of 2.0 to 4.85, said bath being maintained during said electrodeposition at a temperature of at least 180 F.

9. A process for the high speed electrodeposition of nickel comprising electrodepositing nickel on a cathode while employing an insoluble anode at current densities of at least 500 amperes per square foot at the cathode under high agitation conditions wherein the flow rate past the cathode is at least 300 feet per minute from a chlorine and bromine ion free bath consisting essentially of an aqueous solution of nickel ions having a pH within the range of 2.5 to 3.2 and containing 0.1 to 0.3 gram per liter of a 1,2-benzopyrone compound, 1 to 10 grams per liter of a buffering agent capable of buffering said bath in the pH range of 2.5 to 4.0 which has a pK value in the range of 2.0 to 4.85 and between about 0.005 and 0.5 gram per liter of a compound selected from the group consisting of bis-(,B-hydroxyethoxy butyne-Z), diethyleneglycolmonopropargyl ether and butynediol, said bath being maintained during said electrodeposition at a temperature between 180 F. and 210 F.

References Cited UNITED STATES PATENTS 2,312,517 3/1943 Baker 20449 2,449,422 9/ 1948 Smith 20449 2,683,115 7/1954 Du Rose et a1 20449 2,694,041 11/1954 Brown 20449 2,782,152 2/1957 Du Rose et al 20449 OTHER REFERENCES W. A. Wesley et al.: 36th minual Proceedings of the American Electroplaters Society, pp. 79-91 (1949).

A. G. Gray: Modern Electroplating, p. 307 (1953).

The Electrochemical Society, Modern Electroplating, p. 17 (1942).

JOHN H. MACK, Primary Examiner G. L. KAPLAN, Assistant Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,488 ,264 January 6 1970 Raymond E. Bailey et al It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 10, "expansive same column 7, addition agent No. 21, acid 3 g/l plus .2 g/l coumarin plus .25 g/l butynediol Column 9, line 15, 0,0002" should read 0.0002 line 34, "6-acetylcoumarin" should read 6-acetylaminocoumarin Signed and sealed this 10th day of November 1970.

" should read expensive should read o-Phthalic (SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, IR.