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Publication numberUS2999770 A
Publication typeGrant
Publication dateSep 12, 1961
Filing dateAug 27, 1953
Priority dateAug 27, 1953
Publication numberUS 2999770 A, US 2999770A, US-A-2999770, US2999770 A, US2999770A
InventorsGregoire Gutzeit
Original AssigneeGen Am Transport
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Processes of chemical nickel plating and baths therefor
US 2999770 A
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Description  (OCR text may contain errors)

2,999,770 PROCESSES OF CHEMICAL NICKEL PLATING 'AND RATES THEREFOR Gregoire Gutzeit, Highland, Ind., assignor to General American Transportation Corporation, Chicago, 111., a New York corporation No Drawing. Filed Aug. 27, 1953, Ser. No. 376,977 31 Claims. (Cl. 117-130) The present invention relates to improved processes of chemical nickel plating of catalytic materials employing baths of the nickel cation-hypophosphite anion type and to improved baths therefor; and the invention is an improvement upon that disclosed in the copending application of Gregoire Gutzeit and Abraham Krieg, Serial No. 194,656, filed November 8, 1950, now Patent No. 2,658,841, granted November 10, 1953.

The chemical nickel plating of a catalytic material employing an aqueous bath of the nickel cation-hypophosphite anion type is based upon the catalytic reduction of nickel cations to metallic nickel and the corresponding oxidation of hypophosphite anions to phosphite anions with the evolution of hydrogen gas at the catalytic surface. The reactions take place when the body of catalytic material is immersed in the plating bath, and the exterior surface of the body of catalytic material is coated with nickel. The following elements are catalytic for the oxidation of hypophosphite anions and thus may be directly nickel plated; iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The following elements are examples of materials which may be nickel plated by virtue of the initial displacement deposition of nickel thereon either directly or through a galvanic efiect: copper, silver, gold, beryllium, germanium, aluminum, carbon, vanadium, molybdenum, tungsten, chromium, selenium, titanium and uranium. The following elements are examples of non-catalytic materials which ordinarily may not be nickel plated: bismuth, cadmium, tin, lead and zinc. The activity of the catalytic materials varies considerably; and the following elements are particularly good catalysts in the chemical nickel plating bath: iron, cobalt, nickel and palladium. The chemical nickel plating process is autocatalytic since both the origi-- nal surface of the body being plated and the nickel metal that is deposited on the surface thereof are catalytic; and the reduction of the nickel cations to metallic nickel in the plating bath proceeds until all of the nickel cations have been reduced to metallic nickel, in the presence of an excess of hypophosphite anions, or until all of the hypophosphite anions have been oxidized to phosphite anions, in the presence of an excess of nickel cations. Actually the reactions are slowed-down rather rapidly as time proceeds because the anions, as contrasted with the cations, of the nickel salt that is dissolved in the plating bath combine with the hydrogen cations to form an acid, which, in turn, lowers the pH of the bath, and the reducing power of the hypophosphite anions is decreased as the pH value of the bath decreases. Moreover, there is a tendency for the early formation in the plating bath of a black pre cipitate that comprises a random chemical reduction of the nickel cations. Of course, this formation of the black precipitate comprises a decomposition of the plating bath, and is particularly objectionable in that it causes the nickel deposit to be coarse, rough and frequently porous.

For the dual purposes of retarding the formation of the black precipitate mentioned and of increasing the normal plating rate of the bath, various baths of the present type have been suggested employing different additives. For example, in the previously-mentioned Gutzeit and Krieg patent, there is disclosed a chemical nickel plating bath of this type that contains, as an additive, a

buffer in the form of a soluble salt of an organic acid,

n e States at n 2,999,770 .Patented Sept. 12, 1961 of the bath being within the approximate range 4.5 to 5.6,

the absolute concentration of hypophosphite ions in the bath being in the range 0.15 to 0.35 mole/liter, the ratio between nickel ions and hypophosphite ions in the bath being in the range 0.25 to 0.60, and the absolute concentration of acetate ions in the bath being approximately 0.120 mole/liter.

In carrying out the chemical nickel plating process on a commercial scale employing a plating bath of the type mentioned, there may be utilized a continuous system of the character of that disclosed in the copending application of Paul Talmey and William I. Crehan, Serial No. 222,222, filed April 21, 1951, now Patent No. 2,658,839, granted November 10, 1953; which system involves periodic or continuous regeneration of the plating bath by the addition thereto of appropriate ingredients for the purpose of maintaining substantially constant the composition of the bath. More specifically in this system, there are provided a plating chamber and a reservoir; one portion of the plating solution is stored at a relatively low tempera-- ture well below the boiling point thereof in the reservoir; and another portion of the plating solution is held as a bath at a relatively high temperature slightly below the boiling point thereof in the plating chamber. The solution is continuously circulated at alow rate from the reservoir to the plating chamber and then back to the reservoir, the solution being heated substantially to the relatively high temperature after withdrawal thereof from the reservoir and before introduction thereof into the plating chamber, and the solution being cooled substantially to the relatively low temperature after withdrawal thereof from the plating chamber and before return thereof to the reservoir. The body that is to be nickel plated is immersed in the bath in the plating chamber, and is subsequently withdrawn from the bath in the plating chamber after a time interval corresponding to the thickness of the nickel plating thereon that is desired; and during the time interval soluble reagents are added to the solution in the reservoir to maintain in the bath in the plating chamber during the time interval substantially the predetermined composition of the bath previously mentioned, so as to compensate for the ingredients of the bath that are exhausted during the time interval in the plating chamber; this regeneration of the solution in the reservoir consisting essentially of adding thereto appro priate amounts of soluble nickel-containing and hypophosbath having an optimum pH as low as that mentioned is not always desirable.

The present invention is predicated upon the discovery that in plating baths of the nickel cation-hypophosphite anion type mentioned, the formation of black precipitate may be retarded and the plating rates thereof may be substantially increased by the addition thereto of a com pound selected from the group consisting of short chain aliphatic amino'carboxylic acids and the salts thereof; which compounds function to produce an exaltation phenomenon. Moreover, in the bath thesecompounds are amphoteric, producing zwitterions, and thereby forming stable, water-soluble chelate complexes with nickel so that the useful pH range of the bath can be substantially extended to embrace the neutral and near alkaline regions, without resulting in precipitation of in soluble basic nickel salts. Further, these compounds are stable at elevated temperatures, i.e. near the boiling point of the plating bath, so that no reagent loss occurs in the neutral and alkaline zones where purer deposits are obtained. Finally, these compounds, by forming stable, water-soluble chelate complexes with the nickel ions, retard precipitation of nickel phosphite, which is the normal by-product of the chemical nickel plating process resulting from the oxidation of the hypophosphite anions. The last-mentioned feature is particularly important in continuous nickel plating operation in a system of the character disclosed in the Talmey and Crehan patent in view of the fact that in such a continuous system the phosphite anion concentration soon builds-up, after a number of cycles, to a point where the solubility of nickel phosphite is exceeded, with the resultant formation of nickel phosphite as a precipitate, and the consequent rough nickel plating.

In order to be of utility for the present purpose, the compounds mentioned must, of course, be water-soluble; and moreover, for the purpose of chelate formation with the nickel ions the amino group should be either in the alpha or beta position with relation to the carboxyl group, so that either fiveor six-membered rings will result.

Specifically, the zwitterions of the general formula Nun should have the specific structures:

RR-RL-C 0 o m-a -o 0 oso that the resulting nickel chelates have the specific structures:

0 o n-ii-o o :-n 11,1 1 16: --I\IH2 o n -n -ii-o o-ii-ru-m Hu -Ni "NH;

The hydrogen atoms of the amino group can, of course, be substituted, as the nitrogen atom alone is necessary for ring closure. Water-soluble salts of amino acids, alpha or beta-polyamino acids, monoaminopolycarboxylic acids and polyaminopolycarboxylic acids are suitable for the purpose. In other words, the watersoluble compounds should have the reactive groups:

1 It is noted that the chelate complexes (also called inner complexes) are particularly stable since all primary valences as well as the secondary valences of the bound metal atom are satisfied. While, in an ordinary inorganic cation complex, the coordinated molecules 4 form a first zone around the central cation, which then becomes a new complex ion, this is not the case in chelates; rather in chelates the whole structure represents a new, very slightly dissociated, neutral molecule. A comparison between an ammonia complex of nickel and an amino-acid complex of nickel immediately shows this difference:

In view of the foregoing, it is the primary object of the present invention to provide an improved nickel plating process of the character described in which the reactions involved are carried out more efliciently and under more stable conditions than heretofor, thereby rendering the process more desirable from a commercial standpoint.

Another object of the invention is to provide an improved aqueous chemical nickel plating bath which may be employed with advantage in the practice of the improved process.

Another object of the invention is to provide an improved nickel plating process of the character described that employs a plating bath of the nickel cation-hypophosphate anion type containing as an exaltant a compound selected from the group consisting of short chain aliphatic aminocarboxylic acids and salts thereof.

A still further object of the invention is to provide an improved aqueous nickel plating bath of the character described that contains nickel ions, hypophosphite ions and zwitterions.

These and other objects and advantages of the invention pertain to the particular arrangement of the steps of the method and of the composition of the plating bath, and will be understood from the foregoing and following description.

In accordance with the process of the present invention, the article to be nickel plated and normally having a catalytic surface is properly prepared by mechanically cleaning, degreasing and light pickling, substantially in accordance with standard practices in electroplating processes. For example, in the nickel plating of a steel object, it is customary mechanically to clean the rust and mill scale from the object, to degrease the object, and then lightly to pickle the object in a suitable acid, such as hydrochloric acid. The article is then immersed in a suitable volume of the bath containing the proper proportions of nickel cations, hypophosphite anions and amino acid anions, the pH of the bath having been, if necessary, adjusted to an optimum value by the addition of an appropriate 'acid or base, and the bath having been heated to a temperature, just below its boiling point, such as 99 C. at atmospheric pressure. Almost immediately hydrogen bubbles are formed on the catalytic surface of the steel object and, escape in a steady stream from the bath while the surface of the steel object is slowly coated with metallic nickel (containing some phosphorous). The reaction is continued until the color of the bath (green at the start) shows the absence of nickel, or until the evolution of hydrogen gas stops, or until it is determined that the required thickness of the nickel coating has been deposited on the steel object. Of course the steel object is then removed from the bath and rinsed off with water, and, is then ready for use.

Instead of using a batch plating process, as described above, the steel object may be plated in the plating chamber of the continuous system, previously described, by the immersion thereof in the plating chamber for an appropriate time interval. Thereafter, the steel object is removed from the plating chamber, and is rinsed oil with water and, is then ready for use.

With, respect to the composition of the bath, it essentially comprises an aqueous solution containing; nickel binations thereof; and the zwitterions may be derived from a compound selected from the group consisting of short chain aliphatic'aminocarboxylic acids and the salts thereof. Specifically, a suitable bath may be formed in an exceedingly simple manner by. dissolving in Water, nickel chloride, sodium hypophosphite and sodium aminoacetate. The desired pH of the bath is established by the eventual introduction thereinto 'of hydrochloric acid or by the additionthereto of bicarbonate.

The terms cation, anion and ion, as employed herein, except where specifically noted, include the total quantity of the corresponding elements that are present in the plating bath, i.e. both undissociated and dissociated material. In other words, 100% dissociation is assumedwhen the terms noted are used in connection with molar ratios and concentrations in the plating bath, Also hereinafter the expression percent exaltation is employed with the arbitrary definition as the percent increase in the rate of hydrogen evolution with reference to a given Aminosuccinic acid Iminodiacetic acid CHz-C 0 0H 1'lI OH2OOOH Iminotriacetic acid CHECOOH N-CHz-COOH I v our-coon Ethylenediaminotetraacetic acid orb-coon HgCN v OHr-COOH e Y one-coon HaC-N oHPoooH As a matter of convenience, the zwitterions may be introduced into the plating bath by dissolving therein, the salts, particularly the} alkali salts, of the short chain aliphatic' aminocarboxylic acids mentioned. Ihisis partic:

a weak alkali, preferably sodium ularl'yconvenient, since the alkali salts of? these amino carboxylic acids are usually more readily obtainable For example, the tetrasodium salt of.

upon the market. ethylenediaminotetraacetic acid is available in the market under the various trade names: Versene," Nullapon, and Sequestrene.

For the purpose of studying the increase of the hydrohypophosphite at a concentration of 0.225 mole/liter (to which a trace of a nickel salt, i.e. 0.024 mole/liter was added to initiate the reaction at a vigorous rate).

Pickled pieces of mild steel, 20 cm. in area, were introduced for periods of 30 minutes each. The different test solutions respectively contained no additive, and

additives in the form of salts of the following acids: acetic, citric, lactic, succinic, aminoacetic and aspartic. Specifically, the additives, when used, were employed as the sodium salts of the corresponding acids in a con-- centration of 0.125 mole/liter of the anion, and the hydrogen gas evolved was collected and its volume measured by usual methods. The results of these exaltation tests were:

H2 evolved in 30 min. from Additive (anion) 0.125 111/1. 50 cc. solution Percent at 0.225 m/l. exaltation sodium hypophosphlte By comparison of the unsubstituted, and the aminosubstituted carboxylic acids, it will be observed that a remarkable increase in percentage exaltation is produced by the substitution in the organic radical of one amino group for one hydrogen atom. Specifically, the exaltation figure for acetic anion is 94; Whereas that for aminoacetic anion is 125 (a positive difference of 31). Similarly, the exaltation figure for succinic anion is 175; Whereas that for monoarninosuccinic anion (dl-aspartic) is 213 (a positive difference of 38). Thehydroxy-substituted acids are in this connection inferior to the unsubstituted carboxylic acids. [In conjunction with these tests, it is noted that exaltation is independent of buttering efficiency and of the capability of the organic compound' to complex the nickel ions With the formation of chelates. In other words, the short chain aliphatic aminooarboxylic acids, and the salts thereof, have the three unrelated properties of exalt-ating, buffering and chelating; all of which are highly advantageous in the nickel. plating process.

In the use of short chain aliphatic aminocarboxylic acids for chemical nickel plating exaltation, it is believed that this phenomenon results from the formation of a heteropoly-acid between the organic additive and the hypophosphite anions, which competes with inner-com plex (chelate) formation between the nickel ions and the amino-acid radical. If the nickel amino-acid chelate istoo stable, insuflicient nickel cations are available for deposition, and the plating rate becomes low despite the exalting effect produced by the organic additive. In actual plating tests employing plating baths containing short chain aliphatic aminocarboxylic acids and watersoluble' salts thereof, it has been found that the pH variations have less influence on plating rates, in the optimum nickel and hypophosphite ion concentration ranges, than is the case with other organic additives. This is unquestionably due to the amphoteric character of the zwitterions. For example, with aminoacetic ions (glycine) there are three optimum, although not particularly marked, pH regions, i.e. at about 5.5, 6.5 and 8.5; and in any case, the useful pH range of the plating bath is clearly extended with reference to plating baths buttered with salts of simple, unsubstituted carboxylic acids of the character disclosed in the previouslyment-ioned Gutzeit and Krieg patent.

"On the other hand, in the case of short chain aliphatic amino-acid salts (as opposed to ordinary buffers) added to the plating both, best plating results are obtained when the ratio between the amino group and the nickel ion is above 1.5; in other words, when the amount of amino acid ions is suflicient to complex most or substantially all of the nickel ions contained in the plating bath. In this connection, it is pointed out that substantial exaltation is achieved in the plating bath when the amount of amino radical is such that the ratio mentioned is above about 0.5 and that substantially all of the nickel ions are complexed to form chelates when the amount of amino radical is such that the ratio mentioned is 2 or above.

Again referring to the composition of the aqueous plating bath, the following concentrations of ingredients have been found to be optimum: the absolute hypophosphite ion concentration should be in the range 0.15. to. 1.20 mole/liter; the nickel ion/hypophosphite anion ratio should be in the range 0.25 to 1.60; the ratio between the amino group and the nickel ions should be in the range 0.5 to 6.0; and the pH should be in the approximate range 4.5 to 9.0.

The exalting and other characteristics of the various In 50 cc. of this plating bath, properly cleaned steel samples of 5 cm. area (16 gauge) were plated for 60 minutes, the temperature of the bath being 97 C.-98 C. and the pH having been adjusted with sodium bicarbonate, with the following results induplicate tests:

tory in the near neutral and basic regions of the pH range.

In a third series of these plating tests, anamino; acetate bath was employed that had the following composition:

Sodium hypophosphite m./1.. 0.225 Nickel chloride -m./l 0.1125 Sodium aminoacetate Variable Ratio: Ni++/hypo- 0.5

In 50 cc. of this plating bath properly cleaned steel samples of 20 cm. area were plated for 10 minutes, the temperature of the bath being 97 C'.98 C. and the pH thereof having been adjusted with acetic acid and/ or caustic soda. In this plating bath, the plating rate, without the addition of aminoacetate at pH 6.4 was only 0.84 10- gnu/cmP/min. and with the aminoacetate additive, the plating was bright and smooth. The specific results in these tests were as follows (averages of duplicate tests being given):

short chain aliphatic aminocarboxylic acids in the platv ing baths were established by a series of plating tests that S di aminoacetate /1 )5 were made employing a series of test plating baths of the R i A i /Ni++ 053 general character of thatpreviously described and as explained more particularly hereinafter. T t 1 2 3| In the various plating tests appearing hereinafter 40 as weights of nickel plating deposited are reported in gms., Initial H 6 01 6 49 6 m and Plating rates are usually reported in gm/cm-zlmins mam mfiik'i jjlljiiiZZZIIIIIIIZ 21.10 2191 it; although occasionally plating rates are reported in mils/- hour, i.e. 0.00'l"/hour).

In a first series of these plating tests, an aminoecetate g f f i 7fifii plating bath was employed that had the following coma mmo 1 position:

Test 1 2 3 Sodium hypophosphite m./l 0.225 Nickel chloride m./l 0.075 50 Initial pH 6.00 6.78 7.02 Sodium aminoacetaw 1 1125 Plating rate, RXlO 3. 66 3. 36 3.42 Ratio: Ni++/hypo- 0.33 Ratio: Amino/Ni Sodium aminoacetate m./'l 0.18 Ratio: Amino/Ni 1.60

In 50 cc. of this plating bath properly cleaned steel samples of 20 cm. area were plated for 10 minutes, the temperature of the bath being 96 c.-9s c. and the pH Test 1 2 3 4 thereof having been adjusted with sodium bicarbonate, Inml H 6 98 6 20 6 39 6 62 With the following results! Platihg rafezibz fd i::::::::::: 4144 4199 4:31 4139 Weight Rate (1115/ The above plating tests illustrate that best plating rates Initial pH iiifii fg ii hour) are obtained when the ratio of the amino-nickel ions. is

above about 1.50. 6.5 (as prepared) 0.0996 1.3 In a fourth series of these plating tests, an amino- (as adjusted) Q1030 65 acetate bath was employed that had the following com- In a second series of these plating tests, an amino acetate bath was employed that had the following composition:

position Sodium hypophosphite m./l-.. 0.225 Nickel chloride rn./l 0.0675 Sodium aminoacetate Variable Ratio: Ni++/hypo" 0.3

In 50 cc. ofthis plating bath, properly cleaned steel samples of 20 cm. area were. plated for 10. minutes,v the temperature of the; bathv substantially 96 C. and

the pI-L having been: adjusted with acetic acid and/or caustic soda. In these plating tests, the plating was bright v and smooth, and the specific results were as follows: Test 1 2 3 4 1 Initial pH 5.92 6.35 6.65 0.90 Sodium amlnmpefafe m 00675 5 Final pH 2.90 2.88 2.73 231' Ratio: Amino/N1++ 1.0 Weight gain 0.1015 0.1090 0.1110 0.1186

T 1 2 3 4 Sodium aminoacetate m./1 0.1013v Ratio Amino/Ni++ 1.5 Initial pH 5. 92 e. as 6. 05 s. 90 Plating rate, RXlO 2.22 2. 225 2.18 2. 535

Test; 1 2 3 4 Sodium aminoacetate m./l 0.1013

Initial pH 6.0 6.29 Ratio. Ammo/N1 1.5 Final pH 3. 25 3' 49 v 0. 1698 0. 1728 Test 1 2 3 4 Initial DH 6 0 6 29 6 60 6 94 Sodium aminoacetate m./l 0.135 matingma;rig-:3:::::::::::::::: 3.22.5 3398 4:03 4322 Ram Ammo/NIH Sodium aminoacetate m./l 0.135, Test 1 2 a 4 Ratio: Amino/Ni++ 2.0

Initial pH 6.0 s. 22 6. 5s 0. 9s inal pH 3.37 3.51 1.12 I 4.72 Test 1 2 3 4 Weight gain 0. 1871 0. 1950 0. 2114 v 0. 2141 25 iaifig ga',1550:1333:13:11:33: 4. 18 21%? 2:33 213.? a seventh Senes these Plang tests In both the third and fourth of plating tests, it will be observed that when the Ni++/hypophosphite ion ratio is either 0.5 or 0.3, increased plating rates are obtained with increased ratios of amino/Ni:

In a fifth series of these plating tests an amino-acetate bath was employed that had the following composition:

Sodium hypophosphite m./l 0.225 Nickel chloride m./l 0.0675 Sodium aminoacetate Variable Ratio: Ni++/hypo* 0.3

In 50 cc. of this plating bath properly cleaned steel samples of 20 cm. area were plated for 10 minutes, the

temperature of the bath being 97 C. (:1 C.) and the pH having been adjusted with NaOH and HCl. In these plating tests, the plating was bright and smooth. The

specific results in these tests Were as follows (averages of triplicate tests being given):

Ratio: Amino/Ni 2.0 3.0 4.0

Initial pH 6. 64 70 6. Final pH 5. 58 5. 82 5. Weight gain 0. 0907 0 0984 0. 10 Rate, RX10 4. 54 4. 65 5.

From the fifth series of plating tests, it will be observed that the greatest weight gains were achieved with this:

plating bath when the amino/Ni++ ratio was 4.0.

In a sixth series of these plating tests, an aminoacetate bath was employed that had the following composition:

Sodium hypophosphite m./l 0.225 Nickel chloride m./l 0.0675 Sodium aminoacetate Variable Ratio: Ni++/hypo' 0.3

acetate bath was employed that had the following com position: 7

Sodium hypophosphite ..m./l 0.225 Nickel chloride m./l 0.1125 Sodium aminoacetate Variable Ratio: Ni++/hypo- 0.5

In 50 cc. of this plating bath, properly cleaned steel samples of 20 cm. area were plated for 60 minutes, the temperature of the bath being substantially at 98 C. In these plating tests, the plating was bright and smooth and the specific results were as follows:

Fromthese sixth and seventh series of plating tests, it will be observed that over the time interval of 60 minutes, the weight gains of plating increase with increasing pH and with increasing aminoacetate concentrations. I

From this seventh series of plating tests, it will be observed that the weight gains in plating increase rapidly up to an aminoacetate concentration of 0.18 mole/liter, and from thereon, at a much slower rate. Moreover, it will be observed that the differences between the initial and final pH values become smaller as the aminoacetate concentration is increased due to buffering action in the bath. 1

In an eighth series of these plating tests where the Ni++/hyporatio was varied, an aminoacetate bath was employed that had the following composition:

Sodium hypophosphite ..m./l 0.225. Nickel chlorid Variable Sodium aminoacetate m./l 0.12

Sodium aminoacetate m./l.. 0.0675

Ratio: Amino/Ni++ 1.0

In 50 cc. of this plating bath, properly cleaned steel samples of 20 cm. area were plated for 10 minutes and 60 minutes, the temperature of the bath being substantially at 98 C. and the pH having been adjusted'witli ammonium hydroxideto an initial valuewithin-the rangel 11 6.4 to 6.6. In these plating tests, the plating was bright and smooth and the specific results were as follows:

10 MINUTE TESTS plating solution in the reservoir in excess of 24 cycles (as contrasted with a few cycles of regeneration employing prior baths of the character of that disclosed in the Gutzeit and Krieg patent) before there is an intolerable Nwfhypv n o 128 0. 26 0.36 M12 575 Q 647 build-up in the plating bath of the by-product phosph te. As a matter of interest, the plating rate of the plating N101, m./l 0.0288 0.0585 0. 0310 0.1152 0.1293 0.1450 bath Subsequent cycle? the commuous Plating FlnalpH 5.35 5.42 4.94 5.00 4 gg 485 system is increased over the initial cycles thereof; which Rate, 3- phenomenon is not exactly understood.

in In the continuous plating system, a plating bath was Ni++ h o- 0.705 0.709 1.020 1. 232 1.538 emp oyed having the following composition: N'Cl /l 0 1580 0 1730 0 2303 0 2834 0 3400 Sodium hypophosphite" n""" 0225 1 2-111. 4.80 472 4.32 417 Nickel chloride m-./l 01125 Rate, 8X10 5. 42 4.80 4.29 a. 99 4. 08 Sodium aminoacetate m./l 0.225 Ratio: Ni++lhypo- 0.5 MINUTE T STS Ratio: Amino/NH+ 2.20 60 E Trace ion stabilizer Pb++ p.p.n1 1 Initial pH adjusted with 0.18 m./ l. NaOI-I 6.5 N1++/hyp0- 0.128 0.20 0.30 0.512 0.575 0. 047

The trace of Pb++ was added to the plating bath to Fin-MPH: 504 337 18 317 3,17 2,90 increase the stability thereof as disclosed in the previ- Weight gau1 0.0914 0.1702 0.1890 0.2282 0.2317 0.2300 ously mentioned Talmey and Gutzeit application In the continuous plating system, 6 liters of the plating NiH/h 0 7o5 [L769 Q1026 0, 232 0,1533 bath were used, the plating SOlutiOn being flOW'ed' by gravity through a heating coil and then through the Final H. 3.08 3.12 2.95 2. 2.88 plating chamber having a capacity of about 300 cm. so weight gm M234 051912 M055 @2031 0-2113 that the temperature of the plating bath in the plating I chamber was maintained at 99 C. (:L-l" C.). The plat- Th1s e1ghth series of plating tests shows that there is ing solution was regenerated in the reservoir exteriorly defimte Optlmum Tatlo 0f N1++/ yp p p 10118 111 30 of the plating chamber after each cycle by adding thereto plating baths due to the inclusion in the commercial the necessary r -age t and four steel samples of 20 reagents employed in the production of the plating bath cm. area each (80 cm. total area) were plated in the of stabilizing impurities (particularly lead) with the con plating chamber with the following results:

Cycle N0 1 2 3 4 5 6 7 8 Initial pH 0. 02 0. 02 0. 00 0. 4s 0. 57 0. 50 0. 51 0. 50 Final pH 0.22 0.19 0.29 0.15 0.10 0.29 0. 23 Duration nnn) 115 90 100 39 93 204 101 100 Soln. flow rate co./min- 49 63 57 64 58 22 56 54 Weight gain (gms.) 3. 80 2. 51 3. 34 2. 81 3. 00 3. 57 7. 00 4 10 Plating rate, RX10 4. 13 3. 49 4. 17 3. 95 3.90 4. 52 4. 91 4 80 Depletion percent 9.0 6.0 7.9 6.7 7.7 18.0 8.7 9.9 Cumulative deplet. percent 9.0 15. 0 22. 9 29. 6 37. 3 55. 3 611 0 73. 9

Cycle No 9 10 11 12 13 14 15 10 Initial pH 0. 0. 0; 49 0. 51 0. 49 0. 48 0. 4s 0. 47 Final pH 0. 01 0. 19 0. 31 0. 31 0. 35 0. 32 0. 30 0. 14 Duration (min) 120 114 110 110 90 103 100 147 S0111. flow rate cit/min- 45 49 52 57 54 39 Weight gain (gms.) 4 83 4. 52 4. 09 4. 52 4. 22 4. 50 4. 87 0. Plating rate, 13x10- 4.80 4. 5. 05 5. 14 5. 21 5. 54 5. 75 5. 74 Depletion percent 11. 5 10. 7 11. 7 10. 7 10. 1 10.7 11. 6 16.0 Cumulative deplet. percent 85. 4 96.1 107. 2 117. 9 128.0 138.7 150.3 166.3

Cycle N0 17 18 19 20 21 22 23 24 Initial pH 0.49 0.50 0. 4a 0.45 0.52 0.40 0. 52 0. 52 Final pH 0. 23 0. 25 0. 32 0. 33 0. 32 0. 35 0. 30 0. 42 Duration (min 130 141 102 130 145 128 S0111 flow rate so /m1n 42 40 35 42 48 39 42 44 Weight; gain (gms.) 0. 24 0. 58 7.14 7 41 5. 87 7. 50 0. 05 0. 55 Plating.rate,R 10 5.73 5. 53 5.70 0.81 0.17 0. 45 0.22 0.40 Depletion percent 14.8 15.0 10. 9 Y 17.0 13.9 17.7 15.8 10.5 Cumulative deplet. percent- 181.1 190. 7 213. 0 231. 2 245.1 202. 8 278. 0 295.1

sequent inclusion in the bath of a trace of amount of sulfide ion controller as disclosed in the copending application of Paul Talmey and Gregoire Gutzeit, Serial No. 359,428, filed June 3, 1953. Specifically, the optimum ratio of N-i++/hypophosphite ions in plating baths containing amino-acids is between 0.575 and 0.650, due to the circumstance noted.

In the foregoing series of plating tests, a batch plating process was involved; however, baths of the present type are even more advantageous when employed in a continuous plating system as disclosed in the Talmey and Crehan patent. Specifically,.thesebaths have a fast plating rate amt are stable: permitting; regeneration of the- This test was stopped after 24 cycles without reaching the point where nickel phosphite precipitated in the plating solution, whereby a total weight of 123.81 gms. of nickel was plated from the 6 liters of plating solution without phosphite removal, the volume of the plating solution being kept constant by adding some water as the rate of evaporation was greater than the volume of reagent solution added for regeneration. The percent of depletion is an arbitrary indication of the amount of nickel taken out, as a deposit, from the original solution.

In these plating baths, the nickel ion may be supplied by nickel salts other than the chloride, such, for instance, as the sulfate; and in the following plating tests employgenome 13 ing the continuous plating system, the'following plating bath composition was used:

In the plating system, the conditions were the same as previously described with reference to the preceding plating test and the following results were obtained:

Cycle No l 2 3 4 5 Initial pH 6. 38 6. 49 6. 54 6. 48 6.50 Final H-- 5.96 6.19 6. 20 6. 07 6. 27 Duration (mm.) 117 97 115 155 114 Soln. flow rate cc./m 49 59 49 37 50 Weight gain 4. 66 3. 51 4.05 5. 39 4.14 Plating rate, RXlOt 4. 98 4. 53 4. 40 4. 34 4. 53 Depletion percent 11.1 8.3 9. 6 12. 8 9.8 Cumulative depl. percent 11. 1 19. 4 29. 41. 8 51. 6

Cycle No 6 7 8 9 10 In all of the foregoing plating tests, steel was used as the plating base material; however, it should be understood that other materials, such as, aluminum, brass, bronze, plastic (Bakelite), etc., may be plated with very good results using these plating baths. In the plating of aluminum bodies a bath of the general character of that disclosed in the copending application of Raymond R. Reschan and Abraham Krieg, Serial No. 309,939, filed September 16, 1952, now Patent No. 2,694,017, granted November 9, 1954, is recommended and a plating bath of this character was used in plating tests and havingthe following composition:

In 50 cc. of this plating bath a sample of steel and a sample of 28 aluminum each of 20 cm? area were separately plated for 11 minutes at a temperature of about 98 C., with the following results:

Base material Steel 28 aluminum Initial pH 6. 41 6. 41 Weight gain 0.092 0. 128 Plating rate, R 4. 26 6. 82

The plating on the S2 aluminum sample showed excellent adhesion; and these results were verified in a companion 60 minutes test.

In other plating tests a bath of the general character of that disclosed in the Reschan and Krieg patent was employed that had the following composition: 7

Sodium hypophosphite m./l 0.225 Nickel chloride m./l 0.1125 Sodium aminoacetate m./l 0.18 Sodium fluoride m./l' '0.01

Sodium nitrate m./l 0.20 Initial pH, adjusted with NaOH 6.5 Ratio: Ni++/hypo 0.5 Ratio: Amino/Ni 1.6

In 50 cc. of this plating bath a sample of steel and'a' sample of S2 aluminum each of 20 cm? area were separately plated for 10 minutes, the temperature of the bath being about 98 C., with the following results:

Base material Steel Aluminum Weight gain 0.0969 0.0984. Rate, R 10 4.85 5.29. Appearance Bright, smooth... Very bright, smooth. Adhesion Good Excellent.

In another plating test three brass faucets were plated to 0.4 mil thickness in a bath having the following composition:

In this plating bath the plating rate was 1 mil per 50 minutes and the appearance of the faucets after plating was unusually good.

In another plating test, a sample of general purpose Bakelite was plated in a bath having the following composition:

Sodium hypophosphite m./l 0.225

Nickel chloride m./l 0.1125 Sodium aminoacetate m./l 0.18 Pb++ added as stabilizing ion p.p.m 5

Prior to plating, the sample of Bakelite was prepared in accordance with the methods disclosed in the copending applications of Gregoire Gutzeit, William J. Graham and Abraham Krieg, Serial No. 230,352,'filed June 7, 1951, now Patent No. 2,690,401, granted September 28, 1954, and of William J. Crehan, Serial No. 279,945, filed April 1, 1952, now Patent No. 2,690,402, granted September 28, 1954. Specifically, the outer layer of skin of the Bakelite sample was removed mechanically with fine emery cloth; and then it was soaked in an aqueous solution containing 35 ppm. of palladium chloride for 72 hours. The sample was then thoroughly rinsed in warm water, dried, and the palladium chloride was reduced to metallic palladium in a hot aqueous solution of sodium hypophosphite (0.335 m./l.) until bubbling subsided. The plating was initiated instantaneously upon immersion of the prepared Bakelite sample into the plating bath at a temperature of 92 C.; and the plating was carried out for a time interval of minutes in 50 cc. of the plating bath. The plating appearance was excellent and the adhesion thereof was good. In the plating test the bath remained stable and very clear.

In passing, it is noted that further plating tests showed that a soaking for 3 hours in the aqueous palladium chloride solution is optimum for coating adhesion although a soaking time as short as 5 minutes is adequate to obtain initiation of the nickel plating.

In succeeding plating tests, the same technique was applied in the preparation of other plastic materials including fiberglass reinforced polyester plastic, neoprene and phenolic plastic ,(Hycar). These plating tests were also highly successful in that the plating appearance was excellent and the adhesion was good.

Aplating test ..upon a. fBa-kelite sample was 0.0.11-

'15 ducted employing the continuous plating system previously described and utilizing a plating bath having the following composition:

Sodium hypo-phosphite 'm./l 0.225 Nickel sulfate m./l 0.1125 Sodium aminoacetate m./l 0.2.25 Ratio: Ni++/hypo* 0.5 Ratio: Amino/Ni++ 2.0 Stabilizing ion Pb++ p.p.m 4 Initial pH adjusted with NaOH 6.406.50

In this plating test, the bath had a volume of 4.5 liters and the Bakelite sample was pretreated substantially in the manner previously described. Specifically, the pretreatment of the Bakelite sample consisted of the removal of the skin thereon on a sanding belt, followed by the soaking thereof for about 15 minutes in an aqueous solution of palladium chloride (35 ppm.) at a temperature in the range 60 C.80 C. Thereafter the Bakelite sample was rinsed in hot Water, and then 1 6 In another series of these plating tests, an alpha-- alanine plating bath was employed that had the following composition:

1 Sodium hypophosphite m./l 0.225 Nickel chloride rn./l 0.1125 Alpha-alanine m./l 0.225 Radio: Ni++/hypo* 0.5 Ratio: Amino/Ni++ 2.0 pH, adjusted with NaOH Variable In 50 cc. of this plating bath, properly cleaned steel samples of 20 cm. area were plated, the temperature of the bath being about 97 C. In these plating tests, the plating was bright and smooth in the acid bath, semibright in the substantially neutral baths, and dull in the alkaline baths, and the specific results were as follows:

(a) Rate tests-40 minutes immersed in a hot aqueous solution of sodium hypoy Initial H 5.54 0.01 0.52 7.01 7.53 7.00 8.53 9.00 phosphlte 0.225 111-! 11ml bubbhllg SUbSGded' Them wei ht gam 0.0000 0. 0923 0. 0802 0. 0789 0. 0847 0.0802 0. 0839 0. 0251 after the Bakelite sample was rinsed in hot water Rate, RXlO 3. 48 4. 4.31 3. 4 4424 4.01 4.40 4.10 and transferred to the plating chamber in the continuous plating system; whereby it was plated therein with (b) Plating tests-60 minutes the following results:

. rninai rr 5.54 0.01 0.52 7.01 7. 53 7.99 7.53 9.00 Gym N0 1 2 3 5 6 7 Weightgam 0. 2045 0.2373 0.2544 0.2558 0.2595 0. 2325 0. 2252 0.2044

lnitialpH 0. 44 0.51 0.50 0.47 0.45 0. 48 0.47 In a series of these plating tests, a beta-alanine (dlggf i gq 6:35 beta-aminopropionic acid) plating bath was employed cc./m1'.n 38 40 38 37 43 40 43 that had the following composition: Weightgain, gins... 3. 7475 3.4501 3. 2524 4.1070 3.0540 3. 9210 4.7550 Cumulative depleti0n,percent 12.6 24.2 35.2 49.2 63.0 76.4 91-6 Sodium hypophosphite Il1./l 0.225 Nickel chloride m./l 0.1125 In the foregoing series of plating tests, the short chain Beta-alanine m./l 0.225 aliphatic arninocarboxylic acid additive in the plating Radio: Ni++/hypo- 0.5 bath consisted of aminoacetic acid (glycine) or the alkali Ratio: Amino/Ni++ 2.0

salt thereof, fundamentally due to the practical circumstance that these compounds are both cheap and readily avail-able in large quantities in the commercial market. Moreover, it has been verified that the other short chain aliphatic aminocarboxylic acids do not have any particular advantage over glycine and they are considerably more expensive and only available in small quantities in the market. Accordingly, [from a practical standpoint, it is recommended that the short chain aliphatic aminocarboxylic acid additive in the plating bath take the form of glycine or sodium aminoacetate. However, the other short chain aliphatic aminocarboxylic acids and their salts are entirely satisfactory as additives in the plating bath as indicated by the various series of plating tests reported hereinafter.

In a series of these plating tests, an alpha-alanine (dialpha-aminopropionic acid) plating bath was employed that had the following composition:

In 50 cc. of this plating bath, properly cleaned steel samples of 20 cm. area were plated, the temperature of the bath being 97 C.i1 C. In these plating tests, the plating was bright and smooth and the specific results were as follows:

Duration of test 10 minutes 60 minutes Initial pI-I 6.10 6. 10 Final pH... 5.10 8. 10 Weight gain. 0. 1050 0. 2231 Rate, 11x10 5. 25

Initial pH adjusted with NaOH.

In 50 cc; of this plating bath, properly cleaned steel samples of 20 cm. area were plated, the temperature of the bath being 97 C.J -l C. In these plating tests, the plating was bright and smooth, and the specific results were as follows:

Duration of test 10 minutes 60 minutes Initial pH 6; 05 7. 68 8. 61 6. 7. 58 8. 61 Weight gain 0. 0523 0.0727 0.0820 0. 1294 0. 1378 0. 1639 Rate, RXlO- 2. 01 3. 64 4.10

Sodium hypophosphite m./l 0.225 Nickel chloride m./l 0.09 Alphaeminobutyric acid m./l 0.18 Ratio: Ni+'+/hypo 0.4 Ratio: Amino/Ni 2.0 Initial pH adjusted with NaOH 6.5

In 50 cc. of this plating bath, properly cleaned steel samples of 20 cm. area were plated, the temperature of the bath being 97 C.:L1 C. In these plating tests, the

17 plating was bright and smooth and the specific results were as follows:

Duration of tests 10 minutes 60 minutes 6. 50 6. 50 Final pH 5. 80 3. 60 Weight gain- 0. 0740 0. 2401 Rate, R 10 3. 70

In another series of these plating tests, an alpha-amino butyric acid plating bath was employed that had the following composition:

Sodium hypophosphite m./l 0.225 Nickel chloride m./l 0.1125 Alpha-aminobutyric acid m./l 0.225 Radio: Ni++/hypo* 0.5 Ratio: Amino/Ni++ 2.0 pH adjusted with NaOH Variable In 50 cc. of this plating bath, properly cleaned steel samples of 20 cm? area were plated, the temperature of the bath being about 97 C. In these plating tests, the plating was bright and smooth in the acid baths, dull in the substantially neutral baths, and semi-bright in the alkaline baths, and the specific results were as follows:

(a) Rate testsl mlin'utes Initial pH 5.52 6.05 6.53 7.00 7.56 8.62 9.10

Weight gain 0.0733 0.0684 0.0533 0. 0480 0.0464 0.0608 0.0576

Rate, R 3.66 3.42 2.66 2.40 2.32 3.04 2.88

(b) Plating tests-60 minutes Initial pH 5.53 6.05 6.53 7.00 7. 56 8.08 8.62 9.10

Weight gain 0.1902 0. 2356 0. 2468 0. 2465 0. 2321 0. 2310 0. 2224 0. 2000 In connection with the alpha-aminobutyric acid baths, it is pointed out that while the 10 minute rates are low, the '60 minute rates compare very well with those obtained in the aminoacetic acid bath; which circumstance indicates a long initiation period, possibly due to the fact that a longer time is needed for reaching a complexation equilibrium.

In the continuous plating system, an aminosuccinic acid (aspartic acid) plating bath was employed having the In the plating system, the conditions were substantially the same as previously described with reference to the prior plating tests involving the continuous plating system, except that only 4 liters of the bath were employed and the total area of the steel samples was 6 0 cmfi, the temperature of the bath being about 99 C., and the following results were obtained:

Oycle No 1 2 3 7.00 6. 70 6. 6. 40 6. 20 6. 30 1. 4009 l. 1415 1. 5655 3. 31 3. 73 3. 89 Duration of cycle (min) 72 51 67 Soln. flow rate cc./min 51. 4 78. 4 59. 6

In this aspartic acid bath, the plating was bright and smooth.

In a series of these plating tests, an ethylenediamino tetraacetic acid plating bath was employedtha-t was 18 formed from the tetrasodium salt thereof (Versene) and that had the following composition:

Sodium hypophosphite m./l Nickel chloride m./l Ethylenediaminotetraacetic acid (tetrasodium salt thereof) m /l 0.04 Ratio: Ni++/hypo- 0.4 Ratio: Amino/Ni++ 0.9

Initial pH adjusted with acetic acid or NaOH.

In 50 cc. of this plating bath, properly cleaned steel samples of 5 cm. area (shimstock) were plated for 10 minutes, the temperature of the bath being 97 Oil C. In these plating tests, the plating was bright and smooth and the specific results were as follows:

6. 0, 7. 0 8-. 0 Final pH 3. 5 3. 5 4. 9. Weight gain (gms.) 0. 0345 0. 0367 0. 0679 In passing, it is noted that Versene is chemically identical to Nullapon. and Sequestrene that have also been employed with identical results. In these tests, the weight: gains should be multiplied by four for comparison purposes with the other plating tests (because the area of the steel sample was 5 cm? instead of 20 cm? as previously) and it will be observed that this additive (ethylened'iaminotetraacetic acid) produces optimum results in' the alkaline range where this'complexing agent is most effetcive. a

In connection with Versene-Fe-Sp (an acid sodium salt of ethylenediaminotetraacetic acid), it is pointed out that the optimum results are obtained in the near acid range R and the following bath composition is recommended:

Sodium hypophosphite 0.225 Nickel chloride 0.09 Versene-Fe-Sp 0.04

In 5 0 ccfof this plating bath, properly cleaned steelsamples of 5 cm? area (shimstock) were plated, the tem-' perature of the bath being 97 C. 11 C. In these plating tests, the plating was bright and smooth and the specific results were as follows:

Initial pH 5. 0 6. 0 Final pH 4. 3 4. 1 Weight gain (gms.) 0. 0458 0. 0530 Again it is noted that in these plating tests the weight gains should be multiplied by four for comparison pur-.

poses with the other plating tests.

As previously noted, the utilization of an short chain aliphatic aminocarboxylic acid additive in a plating bath. of the character of that disclosed in the Gutzeit and Krieg patent is'advantageous and a plating bath of this character of the following compositionis recommended:

Magnesium hypophospite 0. 15 6' m./l.

Nickel acetate 0.086 m./l. Versene (38% soln.) Variable (0.2% and 1% corresponding to about 0.0027 and 0.0135 m./l.).' Initial pH adjusted with acetic acid 5.69

In 50 cc. of this plating bath, properly cleaned steel samples of 20 cm? werev plated for 60 minutes, the temperature of the bath being about 97 C. and the following results were obtained:

Versene None 0.2% 1.0% None 1% Duration of test-min 1O 10 10 29 Weight gain 0. 1106 0.1168 0.1246 0. 2296 0. 2426 Stability (min) Stable Stable Stable 20 Stable 19 It is noted that this bath is an acetate buffered bath and that the Versene additive results in increased plating rate and has a stabilizing action at a concentration of 1% (0.0135 m./l.).

In passing, it is noted that in similar tests Bakelite samples, prepared in the manner previously explained, were plated, and it was found that the initiation period was shortened from about 9 minutes :to about 3 minutes, again indicating the advantage of utilizing the short chain aliphatic aminocarboxylic acid additive in an acetate buffered bath of the character of that disclosed in the Gutzeit and Krieg patent.

In a further series of plating tests, several short chain aliphatic arninocarboxylic acid additives were employed in each bath, and it was discovered that their actions were accumulative and good results were obtained. In these plating tests, the following four baths were utilized respectively designed as I, II, III and IV, and having the receptive compositions:

In 50 cc. of these plating baths, properly cleaned steel samples of 5 cm. area were plated for 60 minutes, the temperature of the baths being 98 C: 1 C., with the following results:

Bath No I II III IV Initial pH 5. 7s 6. 0 6. 0 6. 0 Final pH 5. 0 4. 3 4. 4 3. 8 Weight gam (gms) 0.1214 0.1563 0.1506 0.1584

In view of the foregoing, it is apparent that there has been provided an improved process of chemical nickel plating, as well as improved plating baths therefor, wherein the baths are of the nickel cation-hypophosphite anion type containing as an additive a compound selected from the group consisting of short chain aliphatic aminocarboxylic acids and salts thereof. The additives mentioned are very advantageous in the plating bath in that they function both as exaltants and as to the plating rate and as retarders as to the formation of black precipitate. Moreover, in the arrangement, the nickel plating may take place within a wide pH range (from about 4.5 to about 9.0), being most useful around neutrality, Where the base metal is least attacked by the plating bath and where plating equipment corrosion is minimized. Furthermore, when these additives are used in the optimum proportion (am-ino/Ni about 2.0) they keep the nickel phosphite from precipitating after many cycles in the continuous plating system, rendering it possible to reach a phosphite concentration of about 1 molar (instead of the usual 0.07 m-./l.) before precipitation starts in the plating bath.

While there has been described what is at present considered to be the preferred embodiment of the invention,

it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A method of depositing nickel from a chemical reduction plating bath, said method comprising immersing a catalytic article to be coated in a solution of nickel ion and a hypophosphite reducing agent capable of reducing the nickel in solution, said solution having a nickel ion concentration of about 7 grams per liter, a hypophosphite ion concentration of about 15 grams per liter, a relatively high plating temperature that is disposed near the boiling point thereof, and an initial pH Within the range from about 5.5 to 9.1, and allowing said article to remain in said solution until a nickel coating of desired thickness is deposited thereon.

2. A method of depositing nickel from a chemical reduction plating bath, said method comprising immersing a catalytic article to be coated in a solution of nickel ion and a hypophosphite reducing agent capable of reducing the nickel in solution, said solution containing an initial quantity of nickel ion of about 7 grams per liter and an initial quantity of hypophosphite ion of about 15 grams per liter and having an initial pH within the range from about 5.5 to 9.1, said solution having a relatively high plating temperature that is disposed near the boiling point thereof, and allowing said article to remain in said s0lut-ion for a time interval sufiicien-t to reduce said initial quantity of nickel ion therefrom.

3. The method set forth inclaim 2, and further comprising regenerating said solution during said time interval by adding thereto soluble ingredients supplying thereto nickel ion and hypophosphite ion and hydroxyl ion in order to maintain during said time interval in said solution substantially said initial quantity of nickel ion and substantially said initial quantity of hypophosphite ion and substantially said initial pH thereof, and so that the total reduction of nickel ion from said solution during said time interval is in excess of said initial quantity of nickel ion therein.

4. A method of depositing nickel from a chemical reduction plating bath, said method comprising immersing a catalytic article to be coated ina solution of nickel ion and a hypophosphite reducing agent capable of reducing the nickel in solution, said solution having a nickel ion concentration of about 7 grams per liter, a hypophosphite ion concentration of about 15 grams per liter, a relatively high plating temperature that is disposed near the boiling point thereof, and an initial pH within the range from about 5.5 to 9.1, and allowing said article to remain in said solution until the nickel is substantially completely reduced as evidenced by the solution turning from green to colorless.

5. A method of depositing nickel on a catalytic surface by chemical reduction plating, said method comprising immersing the article to be coated in an aqueous solution of nickel acetate and an alkaline hypophosphite, the nickel ion concentration of said solution being about 5 grams per liter and the hypophosphite ion concentration being about 10 grams per liter, said solution having an initial pH within the range of about 5.5 to 9.1 and being maintained at a relatively high plating temperature that is disposed near the boiling point thereof, and maintaining said article in such solution for a time sufficient to reduce substantially all of the nickel in solution as evidenced by the solution turning from green to colorless.

6. A method of depositing nickel from a chemical reduction plating solution which comprises immersing the articles to be plated in an aqueous solution containing nickel ion, acetate ion and hypophosphite ion, and having an initial pH from about 5 .5 to 9.1, the nickel ion concentration being about 5 grams per liter, the hypophosphite ion concentration being about 10 grams per liter and the ratio of acetate ion to nickel ion being about 2 to 1, maintaining said solution at a relatively high plating temperature that is disposed near the boiling point thereof, and allowing said articles to remain in said solution for a time suilicient to reduce substantially all the nickel in the solution.

7. A method of depositing nickel from a chemical reduction plating solution which comprises immersing the articles to be plated in an aqueous solution of nickel chloride, an alkali metal hypophosphite and a soluble acetate, and having an initial pH from about 5.5 to 9.1, the nickel ion concentration being about grams per liter, the hypophosphite ion concentration being about grams per liter and the acetate ion being sufficient to exert a buffering action, maintaining said solution at a relatively high plating temperature that is disposed near the boiling point thereof, and allowing said articles to remain in said solution for a time suflicient to reduce substantially all the nickel in the solution.

8. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum; which comprises contacting said body with an aqueous bath comprising nickel ions and hypophosphite ions and a dissolved compound selected from the group consisting of short chain aliphatic aminocarboxylic acids and salts thereof, wherein the absolute concentration of hypophosphite ions in said bath expressed in mole/liter is within the range 0.15 to 1.20, the molar ratio between nickel ions and hypophosphite ions in said bath is the range 0.25 to 1.60, the numerical ratio between amino ions and nickel ions in said bath is within the range 0.5 to 6.0, and the initial pH of said bath is within the approximate range 4.5 to 9.0.

9. The process set forth in claim 8, wherein the'molecule of said compound comprises from 2. to 10 carbon atoms.

10. The process set forth in claim 8, wherein said compound is selected from the group consisting of alphaaminocarboxylic acids and salts thereof.

11. The process set forth in claim 10, wherein said alpha-aminocarboxylic acid is alpha-aminopropionic acid.

12. The process set forth in claim 8, wherein said compound is selected from the group consisting of beta-aminooarboxylic acids and salts thereof.

13. The process set forth in claim 12, wherein said beta-aminocarboxylic acid is beta-aminopropionic acid.

14. The process set forth in claim 8, wherein said compound is selected from the group consisting of polyaminocarboxylic acids and salts thereof.

15. The process set forth in claim 8, wherein said compound is selected from the group consisting of aminopolycarboxylic acids and salts thereof.

16. The process set forth in claim 8, wherein said compound is selected from the group consisting of polyaminopolycarboxylic acids and salts thereof.

17. The process set forth in claim 8, wherein said compound is selected from the group consisting of ethylene diaminotetraacetic acid and salts thereof.

'18. The process set forth in claim 8, wherein said compound is selected from the group consisting of aminoacetic acid and salts thereof.

19. The process set forth in claim 8, wherein said compound is selected from the group consisting of aminosuccinic acid and salts thereof.

20. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palaldium and platinum; which comprises contacting said body with an aqueous bath comprising nickel ions and hypophosphite ions and short chain aliphatic zwitterions of the general formula:

where R is an al-klyl radical, wherein the absolute con centration of hypophosphite ions in said bath expressed in mole/liter is within the range 0.15 to 1.20, the molar ratio between nickel ions and hypophosphite ions in said bath is within the range 0.25 to 1.60, the numerical ratio between zwitterions and nickel ions in said bath is within the range 0.5 to 6.0, and the initial pH of said bath is in the approximate range 4.5 to 9.0.

21. The process set forth in claim 20, wherein the numerical ratio between zwitterions and nickel ions in said bath is at least 2 so that substantially all of the nickel ions in said bath are chelated.

22. The process set forth in claim 20, wherein the resulting chelate is of the general structure:

H2111 --\-N'/ l where R is an alkyl radical.

23. The process set forth in claim 20, wherein the resulting chelate is of the general structure:

HzN- Ni "NH:

Where R and R are alkyl radicals.

24. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum; which comprises contacting said body with an aqueous bath comprising nickel ions and hypophosphite ions and short chain aliphatic zwitterions of the general formula:

NHa

where R and R are alkyl radicals, wherein the absolute concentration of hypophosphite ions in said bath expressed in mole/liter is within the range 0.15 to 1.20, the molar ratio between nickel ions and hypophosphite ions in said bath is within the range 0.25 to 1.60, the numerical ratio between zwitterions and nickel ions in said bath is within the range 0.5 to 6.0, and the initial pH of said bath is in the approximate range 4.5 to 9.0.

25. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum; which comprises contacting said body with an aqueous bath comprising nickel ions and hypophosphite ions and short chain aliphatic zwitterions of the general formula:

NHa' where R and R are alkyl radicals, wherein the absolute concentration of hypophosphite ions in said bath expressed in mole/liter is within the range 0.15 to 1.20, the molar ratio between nickel ions and hypophosphite ions in said bath is within the range 0.25 to 1.60, the numerical ratio between zwitterions and nickel ions in said bath is within the range 0.5 to 6.0, and the initial pH of said bath is in the approximate range 4.5 to 9.0.

26. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum; which comprised contacting said body with an aqueous bath comprising nickel ions and hypophosphite ions and a dissolved compound selected from the group consisting of short chain aliphatic aminocarboxylic acids and salts thereof, said bath having a hypophosphite ion concentration in the range 10 to grams per liter, the molar ratio between nickel ions and hypophosphite ions in said bath being within the range 0.25 to 1.60, the numerical ratio 23 between amino ions and nickel ions in said bath being within the range 0.5 to 6.0, and the initial pH of said bath being in the approximate range 4.5 to 9.0.

27. A bath for the chemical plating of a catalytic material with nickel comprising an aqueous solution of a nickel salt and a hypophosphite and a compound selected from the group consisting of short chain aliphatic aminocarboxylic acids and salts thereof, wherein the absolute concentration of hypophosphite ions in said bath expressed in mole/liter is within the range 0.15 to 1.20, the molar ratio between nickel ions and hypophosphite ions in said bath is within the range 0.25 to 1.60, the numerical ratio between amino ions and nickel ions in said bath is within the range 0.5 to 6.0, and the pH of said solution is in the approximate range 4.5 to 9.0.

28. A bath for the chemical plating of a catalytic material with nickel comprising an aqueous solution of nickel ions and hypophosphite ions and short chain aliphatic zwitterions of the general formula:

where R is an alkyl radical, wherein the absolute concentration of hypophosphite ions in said bath expressed in mole/liter is within the range 0.15 to 1.20, the molar ratio between nickel ions and hypophosphite ions in said bath is within the range 0.25 to 1.60, the numerical ratio between zwitterions and nickel ions in said bath is within the range 0.5 to 6.0, and the pH of said bath is in the approximate range 4.5 to 9.0.

29. The bath set forth in claim 28, wherein the numerical ratio between zwitterions and nickel ions is at least 2 so that substantially all of the nickel ions are chelated.

30. A bath for the chemical plating of a catalytic material with nickel comprising an aqueous solution of a nickel salt and a hypophosphite and a compound selected from the group consisting of short chain aliphatic aminocarboxylic acids and salts thereof, said bath having a hypophosphite ion concentration in the range 10 to grams per liter, the molar ratio between nickel ions and the hypophosphite ions in said bath being within the range 0.25 to 1.60, the numerical ratio between amino ions and nickel ions in said bath being within the range 0.5 to 6.0, and the pH of said bath being in the approximate range 4.5 to 9.0.

31. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath comprising about 0.15 to 1.20 moles per liter of hypophosphite ions, about .04-2 moles per liter of nickel ions and about .02-l.5 moles per liter of a salt of ethylene diamine tetra acetic acid, said bath having a pH'of about 4.5-6.5.

References Cited in the file of this patent UNITED STATES PATENTS Brenner Dec. 5, 1950 2,658,839 Talmey et al. Nov. 16, 1953 2,658,841 Gutzeit et a1. Nov. 10, 1953 2,721,814 Jendrzymski et al Oct. 25, 1955 OTHER REFERENCES

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2532283 *May 5, 1947Dec 5, 1950Abner BrennerNickel plating by chemical reduction
US2658839 *Apr 21, 1951Nov 10, 1953Gen Am TransportProcess of chemical nickel plating
US2658841 *Nov 8, 1950Nov 10, 1953Gen Am TransportProcess of chemical nickel plating and bath therefor
US2721814 *Jan 26, 1954Oct 25, 1955Gen Motors CorpNickel plating by chemical reduction
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3206324 *Jun 22, 1961Sep 14, 1965Daesen John RMethod and pre-flux for coating ferrous metals with nickel prior to galvanizing
US3416955 *Jan 13, 1965Dec 17, 1968Clevite CorpElectroless cobalt plating bath
US3438798 *Aug 23, 1965Apr 15, 1969Arp IncElectroless plating process
US3661556 *Mar 3, 1969May 9, 1972Du PontMethod of making ferromagnetic metal powders
US4171393 *Jun 20, 1977Oct 16, 1979Eastman Kodak CompanyElectroless plating method requiring no reducing agent in the plating bath
US4386121 *Nov 5, 1981May 31, 1983Amchem Products, Inc.Electroless deposition by reduction of nickel compound with hypophosphite
Classifications
U.S. Classification427/438, 106/1.27
International ClassificationC23C18/36, C23C18/31
Cooperative ClassificationC23C18/36
European ClassificationC23C18/36