US3706634A

US3706634A - Electrochemical compositions and processes

Info

Publication number: US3706634A
Application number: US199028A
Authority: US
Inventors: Xavier Kowalski
Original assignee: Monsanto Co
Current assignee: Monsanto Co
Priority date: 1971-11-15
Filing date: 1971-11-15
Publication date: 1972-12-19
Anticipated expiration: 1989-12-19
Also published as: DE2255728C2; DE2255728A1; JPS4861337A; JPS568113B2; BE791401A; US3706635A; FR2160458B1; FR2160458A1; CA1009177A; GB1370387A

Abstract

An electrically conductive medium for the electrodeposition of metals is described which comprises an aqueous solution of a composition comprising (1) a complex consisting of a metal ion and an ethylenediamine tetra(methylene phosphonate) ligand, (2) a complex consisting of a metal ion and a 1-hydroxy, ethylidene1,1-diphosphonate ligand, and (3) a complex consisting of a metal ion and an amino tri(methylene phosphonate) ligand.

Description

United States Patent 1151 3,706,634 Kowalski 1 1 Dec. 19, 1972 [54] ELECTROCHEMICAL COMPOSITIONS FOREIGN PATENTS OR APPLICATIONS AND PROCESSES Inventor: Xavier Kowalski, St. Louis, Mo.

Assignee: Monsanto Company, St. Louis, Mo.

Filed: Nov. 15,1971

Appl. No.: 199,028

US. Cl. ..204/46, 204/43, 204/44, 204/45 R, 204/48, 204/49, 204/50 R, 204/52 R, 204/54 R, 204/55 R, 204/D1G. 2

Int. Cl. ..C23b 5/02, C23b 5/46 Field of Search ..204/45 R, 46, 47,48, 49, 50 R; 204/50 Y, 51, 52 R, 52 Y, 53, 54 R, 54 L, 55 R, 55 Y, 43, 44, DIG. 2; 106/1; 117/130 E References Cited UNITED STATES PATENTS ethylenediamine 1.539.226 9/1968 France ..204/46 1,909,144 9/1970 Germany ..204/46 2,023,304 11/1970 Germany ..204/45 Primary Examiner--G. L. Kaplan Attorney1ames J. Mullen et al.

57] ABSTRACT 11 Claims, N0 Drawings ELECTROCHEMICAL COMPOSITIONS AND PROCESSES The present invention relates to the electrodeposition or electroplating of metals and to novel media which may be employed in the electrodeposition or electroplating of metals. The invention further relates to novel processes for the preparation of such media and to novel processes for the electrodeposition of metals.

Processes for theelectrodeposition of metals are well known and involve electrolyzing an electrically conductive medium (e.g., an electroplating bath also known as a galvanic solution) which usually comprises an aqueous solution of an inorganic metal cyanide. The metal of the metal salt dissolved in such a medium is usually the metal which it is desired to electrically deposit upon a substrate.

Classically the electrodeposition or electroplating system consists of an electroplating bath and two or more electrodes in which the cathode or cathodes comprise -the object upon which the metal is to be deposited. The anode usually, although not necessarily, consists of a solid metal or metal alloy containing metal identical to the metal of the plating metal ions in the electroplating bath. Such metal ions will be trans formed into a film or plate of elemental metal as they are electrically deposited upon the cathode.

Electroplating baths (galvanic solutions) are usually aqueous alkaline solutions or dispersions of metal cyanides and often have disadvantages (depending upon the particular metal ion and/or the particular surface on which the metal ion is to be deposited) of producing relatively dull or lusterless plates or coatings and/or deposits of coatings of uneven thickness. Furthermore, the use of metal cyanide solutions can be hazardous since, if the pH of the electroplating medium should drop to neutral or below, there is a danger of poisonous hydrogen cyanide gas being produced. Also the use of metal cyanides presents a disposal problem due to their toxicity and such disposal, unless the cyanides are dumped into sewers or streams in which they cause pollution, is expensive.

It has been proposed heretofore in U.S. Pat. No. 2,195,409 to partially overcome some of the disadvantages of dull plates or plates of uneven thickness by adding to an electric bath, containing a metal cyanide, a nuclear alkyl derivative of an aromatic sulfonic acid of the benzene series (as distinguished from nuclear alkyl derivatives of condensed polynuclear aromatic sulfonic acids such as those of the naphthalene series). According to this patent the presence of a small amount of an alkyl aromatic sulfonate eliminates pitting (e.g., uneven thickness) and the formation of pin holes in the metal plate. Further, according to this patent, the plates are bright, uniform deposits of metal. Still further, according to this patent, employment of such sulfonates has a further advantage in that they act as emulsifying agents and also form soluble salts with many of the metals used in electroplating. However, these organic compounds are used with metal cyanides and the resulting media possess the disadvantages possessed by metal cyanides.

Basically, the problems connected with the cyanide electroplating were overcome as pointed out in the inventions described and claimed in US. Pat. No. 3,475,293 via the utilization of certain diphosphonates or mono-amino lower alkyl phosphonates. As a supplement and improvement to the inventions of U.S. Pat. No. 3,475,293, via the utilization of certain diphosphonates or mono-amino lower alkyl phosphonates. As a supplement and improvement to the inventions of U.S. Pat. No. 3,475,293, I have now found that certain compositions comprising three different species of organophosphorus compounds are cooperatively effective in electroplating plating'baths at a pH greater than about 6.0 and said baths are characterized by having'a high degree of stability over a wide temperature range.

In accordance with the present invention, it has been found possible to electrically deposit certain hereinafter defined metals on a wide variety of substrates or basis metals by the use of certain aqueous solutions or dispersions of hereinafter defined complexes of metal ions and three different species of organophosphorus compound ligands. The electrolysis of these solutions or dispersions (having a high pH of 6 to 13) results in metal deposits of uniform thickness which have a continuity and brightness which can be controlled as desired.

It is one object of this invention to provide a novel electrically conductive medium which may be employed in the electrodeposition of metals.

It is a further object of this invention to provide processes for preparing an electrically conductive wherein M is hydrogen, alkali metal (such as sodium, potassium, lithium and the like) ammonium, alkylam monium and amine; (2) a complex consisting of a metal ion and a l-hydroxy, ethylidene-l,l-diphosphonate ligand of the formula:

wherein M is the same as described above; and (3) a complex consisting of a metal ion and an amino tri( methylene phosphonate) ligand of the formula:

(III) wherein M is the same as described above. The threecomplex-containing composition is present in such solution (or dispersion) in an amount sufficient to electrically deposit the metal of ametal ion when an electric current is passed through said solution (or dispersion). More specifically, it is found that the use of this three complex-containing composition results in a unique cooperative effect as contrasted to the use of complexes (1), (2) or (3)" above on an individual basis. This cooperative effect is quite. unexpected as will be ,seen from the results hereinafter described in the Examples.

It is to be understood that the following terms, phrases or words used hereinafter, have the meanings so indicated:

a. aqueous solution includes and means both a solution and a dispersion of the. composition (described below).

b.'(aqu eous solution of a) composition includes and means the complexes (1), (2)" and (3) described above, and/or a single complex consisting of a metal ion, the ethylenediamine tetra-(methylene phosphonate) ligand, the l-hydroxy, ethylidene-l,ldiphosphonate ligand and the amino tri(methylene phosphonate) ligand.

c. EDTMP or ethylenediamine tetra(methylene phosphonate) ligand includes and means all of the compounds falling within Formula I above (e.g., full acid, salts and partial salts). A

d. HEDP or l-hydroxy, ethylidene-l,ldiphosphonate ligand" includes and means all of the compounds falling within Formula 11 above (e.g., full acid, salts and partial salts). I

e. ATMP" or amino tri(methylene phosphonate) ligand includes and means all of the compounds A falling within Formula 111 above (e.g., full acid, salts and partial salts).

Regarding items (c), (d) and (e) above, it is to be understood that where one so desires, and there is no substantial adverse effect on the desired end result, and ester (full or partial) of EDTMP and/or HEDP and/or ATMP could be employed. 1n the above medium (galvanic bath), the metal ion is advantageously a metal ion from the group cobalt, silver, tin, copper, iron, nickel, zinc, gold and cadmium ions. The particular metal employed to form the aforementioned complexes with the EDTMP, HEDP and ATMP ligands will generally depend upon the metal which it is desired to electrically deposit.

It is to be understood that the metal ions to be employed-are preferably those water-soluble metal compounds which form chelates with EDTMP, HEDP and ATMP, i.e., the chelate constituents. Illustrative, but not limiting, metal compounds used in the present invention can be 1) simple ionic metal salts which, when dissolved, set free a metal ion capable of a chelate formation, for example, copper sulfate, or (2) they are more complex salts which, when dissolved, give a metal ion capable of a chelate formation, for example, sodium zincate, or (3) metal salts, such as the carbonates, which react with the EDTMP, HEDP and ATMP chelate constituents, and form metal chelate salts. Furthermore, the plating of alloys can be accomplished according to the invention by the use of two or more different metals capable of a chelate formation used in correct proportions. As examples of the plated alloys of the invention, there may be mentioned copper-nickel alloys and copper-zinc alloys "yellow brass and white brass. v

The amounts of metal ions (in the form, for example, of water-soluble metal salts) and the EDTMP, HEDP and ATMP ligands utilized in the electroplating medium or galvanic baths can vary depending upon several variables such as bath temperature, pH, substrates to be plated, water-solubility of the composition, i.e., the metal ion EDTMP, HEDP and ATMP complexes, and the like. 0f the above-described composition, it is preferred to be water-soluble to an extent such as to provide from about 0.1 to about 5 percent by weight, preferably 1 .to about 5 percent by weight, based on the total weight of said aqueous solution, of a transitional metal ion (in water when dissolved therein). In this connection, suitable electroplating baths of the invention can be prepared by using from about 0.01 to about 400 grams of the EDTMP-HEDP- ATMP (chelate constituent) per liter; a concentration of S0 to grams per liter is utilized effectively.

Within thecomposition per se, it is a critical feature of this invention that the mole ratios of EDTMP, ATMP and HEDP to metal ion be within a certain range in order to produce the cooperative effect heretofore described. Regarding HEDP, the mole ratio of HEDP to metal ion is from about 1:1 to about 4:1. preferably from about 1.5:1 to about 3:1. Regarding ATMP, the mole ratio of ATMP to metal ion is from about 0.521 to about 2:1, preferably from about 0.75:1 to about 1.5:]. Regarding EDTMP, the mole ratio of EDTMP to metal ion is from about 0.1 :1 to about 1:1, preferably from about 0.25:1 to about 1:1. In all cases, however, it is critical that the mole ration of HEDP to metal ion and ATMP to metal ion be higher in numerical valuethan the mole ratio of EDTMP to metal ion. For example, where the mole ratio of HEDP and ATMP to Cu is, respectively, 1:1 and 0.5:1, the mole ratio of EDTMP to Cu must be less than 0.5:1, such as 0.4:1. Additionally, for example, where the mole ratio of HEDP and ATMP to Cu is, respectively, 4:1 and 2:1, the mole ratio of EDTMP to Cu can be as high as 1:1. A typical overall mole ratio of HEDP and ATMP and EDTMP to metal ion such as copper would be, respectively, (1.5 1.0 0.25 ):l.

It is to be understood that outside of the aforegoing molar ratios, the cooperative effect does not manifest itself. For example, and when using copper cations, it has been found in the present invention experimentation that increasing the amount of EDTMP-ligand (above that stated above) in the overall composition narrows the brightness range (hereinafter defined) by producing wider burns in the high current density area. Conversely, decreasing the amount of EDTMP ligand (above that stated above) in the overall composition" results in a less effective plating in a low current density area or in a lower covering power." Similar observations are made when using ATMP in amounts outside of aforegoing mole ratios.

The amount of the composition comprising a metal ion and the EDTMP-HEDP-ATMP ligands which may. be present in the electrically conductive medium may vary considerably and will usually depend upon the solubility of the composition. Generally speaking, the amount of composition is based upon the amount of metal employed and the composition" is usually present in an amount which is sufficient to provide from about 0.1 to about 5 percent by weight, based on the weight of the aqueous solution of metal in the form of metal ion. Such compositions comprising these metal complexes are usually substantially soluble under these circumstances. The particular concentration of the composition" within the above range will depend primarily upon the particular metal of the metal complexes. Thus, for example, whena divalent metal ion is iron or copper, the concentration of the composition preferably is a concentration sufficient to provide from about 1 to about 5 percent by weight of copper or iron. When the metal of the metal complexes is nickel, the concentration of the composition is preferably a concentration sufficient to provide from about 1.5 to about 3 percent by weight of the nickel. In the case of zinc the concentration of the composition is preferably such as to provide a concentration from about 2 to about 5 percent by weight of the zinc; and in the case of cadmium the concentration of the composition is preferably such as to provide a concentration from about 1 to about 4 percent by weight of cadmium.

As noted hereinbefore, the electrically conductive medium, which comprises an aqueous solution of the composition comprising the metal complexes, operates only at a high pH range, for example, a pH range of from about 6.0 to about 13.0; lower pHs are not operative for producing the cooperative effect. The pH of the medium will depend to some extent upon the metal ion of the metal complexes, the alkali metal or hydrogen cation and also to some extent upon the substrate upon which the metal ion is to be electrically deposited in the elemental state. Thus, by way of example, when the electrically conductive medium comprises an aqueous solution of divalent copper and the EDTMP-HEDP-ATMP ligands, the pH of the medium may be in the range of from about 6.0 to about 13.0, the higher pHs being attained when M in the above described Formulae i or 11 or III is an alkali metal cation instead of a hydrogen cation. If the electrically conductive medium containing a copper complex is to be used, for example, in plating copper on steel or brass, the PH of the medium is preferably in the range of from about 6.0 to about 10.5. if the electrically conductive medium containing copper EDTMP-HEDP- ATMP complexes is to be used for plating, for example, copper on aluminum the pH of the medium may be in the range of from about 8.0 to about 13.0.

If the electrically conductive medium comprises an aqueous solution containing iron ions and the EDTMP- HEDP-ATMP ligands, the medium preferably has a pH in the range of from about 9.0 to about 11.0. When such medium is to be used, for example, to deposit iron on brass the pH of the medium preferably is in the range of from about 9.5 to about 11.0, whereas if the medium is to be used, for example, to deposit iron on zinc the pH of the medium preferably should be in the range of from about 9.5 to about 12.

When the electrically conductive medium comprises an aqueous solution of a complex containing nickel ions and the EDTMP-HEDP-ATMP ligands, the pH of the medium preferably should be in the range of from about 8.5 to about 11. Media having pHs within this range have been found to be particularly advantageous when it is desired to deposit nickel on zinc, brass or steel.

When the electrically conductive medium comprises an aqueous alkaline solution of a composition containing divalent zinc ions and the EDTMP-HEDP-ATMP ligands, the pH of the medium usually should be in the range of from about 8.5 to about 12, preferably in the range of from about 9.0 to about 11, and such a medium has been found particularly advantageous in the electrodeposition of zinc on steel and brass. When the electrically conductive medium comprises an aqueous alkaline solution of a composition containing divalent cadmium ions and the EDTMP-HEDP-ATMP ligands, the pH of such medium usually should be in the range of from about 8.0 to about 1 1.5, preferably in the range of from about 8.5 to about 10.0, and such medium has been found to be particularly advantageous in the electrodeposition of cadmium on steel or brass.

The electrically conductive medium, comprising the aqueous solution of the composition, may be prepared in a variety of ways which will depend upon the particular class or species of the individual ligands which it is desired to employ to form the metal complexes and more particularly the metal (ion) which it is desired to complex with the ligands. Although in many instances the metal complexes may be synthesized prior to its dissolution or dispersion in water, it has been found generally desirable to dissolve component precursors of the complexes in water to form the composition containing the desired metal ion and the EDTMP-HEDP-ATMP ligands. The components of the composition which usually comprises the EDTMP- HEDP-ATMP ligands, an alkali metal ion and a divalent metal ion, may be dissolved in the aqueous medium (usually water) simultaneously or in any order. However, it has been found advantageous and preferred to dissolve the EDTMP-HEDP-ATMP ligands in water containing the alkali metal, and thereafter to add the metal, usually in the form of a water soluble metal salt, to the medium.

It has been found particularly advantageous to disperse the EDTMP-HEDP-ATMP ligands either in the acid form or in the alkali metal ester form and to add to the resulting solution the metal (ion), in the form of a water soluble salt consisting of the metal (ion) and a nonoxidizing anion. Alternatively, the EDTMP-HEDP-ATMP ligands, in the acid form, may be dissolved in water, the metal (ion) salt added to the solution and thereafter the alkali metal is dissolved in the solution. The anions of the metal salts, e.g., the metal (ion) and the alkali metal salts, are preferably nonoxidizing anions such as, for example, sulfate, chloride, phosphate, citrate, carbonate, oxide, or acetate anions. For example, anions such as carbonate or sulfate anions are preferred for copper cations.

When the EDTMP-HEDP-ATMP ligands are added as the hydrogen or acid form, it may also be desirable to add the alkali metal, in the fonn of a water soluble alkali metal salt, containing any of the anions referred to above. When it is desired, for example, to prepare an aqueous alkaline dispersion of a composition" comprising divalent copper ions and the EDTMP-HEDP- ATMP ligands either in the acid or alkalimetal form appropriate quantities of copper carbonate, the EDTMP-HEDP-ATMP ligands in the acid form, and an alkali metal carbonate are dissolved in water with agitation. During the addition ofthe ingredients, when a carbonate is employed, carbon dioxide is evolved and the resulting dispersion is free of the added anions thus eliminating the necessity for pH adjustment due to the presence of the anion. By so proceeding, as will be evident hereinafter from the examples, there is provided an aqueous alkaline solution of a composition from which, when an electric current is passed therethrough, the metal (ion) can be deposited upon a suitable cathode. v l

, A plating bath which has been found particularly-advantageous may be prepared by first dissolving the full acids of EDTMP, RED? and ATM? ligands in water containing KQH, NaOH or NH OH. (Where the solubility of these materials in water, i.e., EDTMP, HEDP and ATM? is not sufficient toprepare' to desired concentration, it is desirable to utilize commercially available products such as Monsanto Company's Dequest brand of EDTMP, 'HEDP and ATMP, whereby these materials are already present in an aqueous solution via the manufacturing process.) To the resulting solution there is added the desired amount of metal salt and the resulting solution may then be adjusted to the desired pH by the further addition of an alkali material such as KOl-l, NaOH or NH OH.

The present invention further provides a process for the electrodeposition of a metal (ion) which comprises the steps of electrolyzing an aqueous solution of a composition comprising metal complexes consisting of any of the metal ions hereinbefore described and the EDTMP-HEDP-ATMP ligands. The amount of composition" present in the solution is, for example, an amount sufficient to provide fromabout l to about 5 percent'by weight, based on the weight of the dispersion, of said metal. By so proceeding, metals such as copper, iron, nickel, zinc and cadmium may be electrically deposited on a cathode comprising substrates such as steel, aluminum, brass, zinc and the like.

During the electrolysis, that is, the passing of an electric current through the aqueous solution, the bath is maintained at a temperature of from just above the freezing point to justbelow the boiling point of the aqueous solution, generally from room temperature to 90C. For reasons of current efficiencies, it has been found preferably to maintain the temperature of the electrically conductive medium in the range of from about 40C to about 80C.

The amount of current employed in the electrodepositionmay vary widely depending upon the particular metal ion in the form of complexes with the EDTMP-HEDP-ATMP ligands, the particular 'EDTMP-HEDP-ATMP ligands, the temperature of the current sufficient to provide a current density of from about 0.5 to about 300 amperes per square foot of electrode surface. Ordinarily when the current is passed through an electrically conductive medium which is quiescent or unagitated, the current employed will be an amount'sufficient to provide a current density of from about 1 to about 150 amperes per square foot and when the electrically conductive medium is agitated to the current employed will be an amount sufficient to provide a current density in the range of from about 1 to about 300 amperes per square foot of electrode surface. The amount of current employed will depend to some extend on the metal (ion) which it is desired to deposit. I

When it is desired, for example, to deposit or to electroplate copper, the electrically conductive medium will comprise an aqueous alkaline solution containing complexes of divalent copper ions and the EDTMP- HEDP-ATMP ligands and the current employed will be preferably an'amount sufficient to provide a current density of from about 1 to about 120 amperes per square foot of electrode surface. When such electrically conductive medium is not agitated, the preferred amount of current will be an amount preferably sufficient to provide a current density in the range of from about 2 to about 60 amperes per square foot. When the medium is agitated the amount of current employed will be an amount sufficient to provide the current density of from about 2 to about 120 amperes per square foot.

In preferred processes, when it is desired to electrodeposit copper, the electrically conductive medium (the galvanic or plating bath) will comprise an aqueous alkaline solution containing divalent copper ions and EDTMP-HEDP-ATMP ligands. The current employed preferably is an amount sufficient to provide a current density of from about 1 to about 100 amperes per square foot of electrode surface. When the medium is not agitated the preferred amount of current will be an amount sufficient to provide a current density in the range of from about 2- to about 50 amperes per square foot of electrode, whereas when the medium is agitated, the preferred amount of current employed will be an amount sufficient to provide a current density of from about 2 to about 100 amperes per square foot of electrode.

When is it desired to deposit or electroplate nickel, the electrically conductive medium will comprise an aqueous alkaline solution containing divalent nickel ions and EDTMP-HEDP-ATMP ligands, and the current employed will usually be an amount sufficient to provide a current density of from about 1 to about 300 amperes per square foot of electrode surface.

When such electrically conductive medium is unagitated the amount; of current will be that which preferably will provide a current density in the range of from about 5 to about amperes per square foot, whereas when the medium is agitated the amount of current will preferably be an amount sufficient to provide a current density of from about 1 to about 50 amperes per square foot of electrode surface.

. When it is desired to electrodeposit zinc, the electrically conductive medium willcomprise an aqueous alkaline solution containing complexes of divalent zinc ions and EDTMP-HEDP-ATMP ligands, and the current employed will be an amount sufficient to provide a current density of from about 1 to about 50 amperes per square foot of electrode surface. When the medium is not agitated, the preferred amount of current employed will be an amount sufficient to provide a current density of from about 1 to about 25 amperes per square foot whereas, when the medium is agitated, the current employed will be an amount sufficient to provide a current density of from about 1 to about 50 amperes per square foot of electrode surface.

When it is desired to electrodeposit cadmium, the electrically conductive medium will comprise an aqueous alkaline solution containing complexes of divalent cadmium ions and EDTMP-HEDP-ATMP ligands. The current employed will be an amount sufficient to provide a current density of from about 1 to about 50 amperes per square foot of electrode surface. When the electrically conductive medium is not agitated they preferred amount of current will preferably be an amount sufficient to provide a current density in the range of from about 2 to about 40 amperes per square foot whereas if the electrically conductive medium is agitated, the amount of current will preferably be an amount sufficient to provide a current density of from about 1 to about 50 amperes per square foot of elec trode surface.

The time required to electroplate or to electrically deposit the metals will vary with the current density in the medium and will depend upon the thickness of the plate or deposit which it is desired to obtain. Generally, the greater the current density, the shorter will be the time required to produce a deposit or plate comprising a given thickness of electrically deposited metal.-

In accordance with a preferred embodiment of the processes of this invention, it has been found possible to electrically deposit copper on a wide variety of basis metals or substrates such as zinc, iron, brass, steel, aluminum and the like. This preferred process comprises passing an electric current, at a density in the range of from about 5 to about 150 amperes per square foot of electrode surface, through an aqueous alkaline solution containing complexes of divalent copper ions and potassium salts of the EDTMP-HEDP-ATMP ligands, i.e., hexapotassium ethylenediamine tetra(methylene phosphonate) tetrapotassium l-hydroxy, ethylidenel, l -diphosphonate and hexapotassium amino tri(methylene phosphonate), having a pH in the range of from about 8.0 to about 12.0. The amount or concentration of the composition containing these complexes in the solution is an amount sufficient to provide from about 1 to about 5 percent by weight, based on the weight of the solution, of copper and the tempera ture of the solution is maintained within the range of from about 50C to about 70C during the passage of the electric current therethrough.

In accordance with another preferred embodiment of the processes of this invention an electric current at a density in the range of from about 5 to about 150 amperes per square foot of electrode surface is passed through an aqueous alkaline solution containing complexes of divalent nickel ions and potassium salts of the EDTMP-HEDP-ATMP ligands, i.e., hexapotassiurn ethylenediam ine tetra( methylene phosphonate tetrapotassium l-hydroxy, ethylidene-l ,l diphosphonate, and hexapotassiurn amino tri(methylene phosphonate) having a pH in the range of from about 8.0 to about 10.5. The concentration of the composition containing these complexes in the solution is sufficient to provide from about 1 to about 5 percent by weight, based on the weight of the solution, of nickel and the temperature of the solution is maintained in the range of from about 50C to about C during the passage of the electric current therethrough. It is to be understood that the plating (galvanic) solutions of the present invention can contain the known brighteners, buffers, and leveling agents and other additives. Boric acid and its salts are the compatible buffers for many formulas of the invention. The known brighteners suitable for a certain metal, when present in the galvanic solutions described here, are in general beneficial for the same metal; for example, selenites and arsenites are useful for the copper plating baths and aldehydes and ketones for the zinc plating baths.

Other additives which maybe employed in the electroplating solutions of the present invention are disclosed in the 39th Annual Edition, Metal Finishing Guidebook Directory For 1971, published by Metals and Plastics Publications, Inc., 99 Kinderkamack Road, Westwood, New Jersey, and which publication is incor porated herein by reference.

The following examples are intended to illustrate the invention but not to limit the scope thereof, parts and percentages being by weight unless otherwise specified.

EXAMPLE 1 Approximately 24 tests were conducted in this Example in order to show the cooperative effect of the HEDP, EDTMP and ATMP ligands in the electrodeposition of metals from an electroplating solution containing such ligands, as contrasted to the utilization of these ligands on an individual basis.

Twenty four plating solutions were individually prepared in a glass beaker in the following manner. The solutions were prepared in deionized water by first adding potassium hydroxide followed by the particular ligand and then a copper salt which was copper sulfate. Final adjustment of the pH of each solution was made with the addition of potassium hydroxide. The pH of each solution was approximately 8.0. It was noted in some cases that considerable heat was evolved during the addition of the ligand to the potassium hydroxide aqueous solution and that the temperature reached 6070C within a few minutes. This temperature range resulted in a quick dissolution of the ligand and the copper sulfate into the aqueous solution. In certain instances, when the copper sulfate would not dissolve at the 60-70C temperature range, the solution was heated up to C and stirred vigorously for an additional 20 minutes. The solutions were cooled, if necessary, to the plating temperatures indicated in Table l and transferred from abeaker to a Hull Cell. The particular ligand utilized, the ligand to copper mol ratio and the percent copper in solution are all shown in Table l.

The Hull Cell was constructed substantially as the electrolysis cell described in US. Pat. No. 2,149,344 (which is incorporated herein by reference) and the galvanic deposition was performed with intermittent agitation. The Bull Cell utilized in this case had a capacity of l,000 milliliters. This type of Hull Cell is standard equipment for the evaluation of electroplating solutions by the determination of the brightness range. By subjective evaluation, this permits the formulalMllll 02M g indicated the overall electroplating effect was "poor to fair. In ted in Table l and were each X 3% inches 5 test Nos. 6 9, utilizing a steel cathode, the brightness Nos. and 11, and l2, respectively, with brass and steel cathodes, the brightness rating is poor to fair.

Nos. 13 with brass and steel cathodes ilpoori! Referring to Table I, test Nos. 1 5 were made utilizing the HEDP ligand per se with a brass cathode and the results shown under the brightness ratin rating was also basically poor.

In using the EDTMP ligand per se in test The use of the ATMP ligand per se in test and 14, respectively, resulted in the brightness rating range of from to very bad.

The unique cooperative effect of the HEDP, ATMP in this test were brass or steel o 952d 0 3:3 2: omen. $05.55 2: .623 2 tion of a brightness rating" which takes into con-.; sideration the overall variables utilized in and the end results obtained from the electroplating test. The particular cathodes utilized as so indi in size. The anode utilized in these tests was made of copper and was 2* X 2% inches in size.

As noted in the footnotes of Table I, each test was conducted for a period of 5 minutes at a constant current of 5 amperes. The results of these 24 tests are set forth in Table l and particular attention is directed to the column designated Brightness Rating which is the basic criteria for an evaluation of the electroplating ,sfissts an. a ral b EE E divas-Ea o2 cgaozua .3: 231: one: 253 c o 8'0 2. .33 5 553- 33 23 0 310 2. 5 .m6 9 0 a 9: co nsuuoom an: nco moa 30583.3 95. 30 0070 8 w ZMnmd my n su 3 q v 050a uc fi m u u co e on H a" nd a. 5 3 30 new Joana 2.3.3 20 To. 03 0 2. u nqoauvu 2m n or uoe n 2.3.3 he; 20 02 0 3 m dlmm my .5: nomuasn oiow Joann 3m n 93 oma c OF H nowusan neon 53m 23. -o P7; 00 00 H 13 0 v 3 awe. oomusan uzmfim v o QnH o o. w d e 258 23 8-0 8 m 12 0 mi haze-van: mc e a oz 3.; o o 2. in 19:!- 0o owe: v n boom ma e 8 a; c0323 noon 2921: 03 one: 25 .3: on o 00 1 sol-n: coo owe: 2m n .SPA mm o 00 m a iota: co once. 2m n uoom 0 00 N 1nd essence poem com 070 8 A 1: e335. noon 325 33 m 3 0 o: n 1.. coflnunnu uoom an: awmo. ovmozaw noon oo o co m um 335 3 8 33 6 2 0 0 8 m H; .93 3 couga- .=5 3: 235 S a To 2. H 1: 32 23 .33 $6 9. A A".. w 0: :3. 5 .223 3 m 9.6 on H HI. n z 5 :33 6-32: 8 6 35 3 mo e 8 m 1m vouuoau -5 oumwaim noon c-c 8 m 1 3:26 :ocvnu m :0 3:35am m nes invuofi o. 03am env sion ome; 30:23am o\nz o3 s 3 EH at;

ma nm EH On was were conducted utilizing copper cyanide as a standard. The brightness rating on all four of these tests was good as shown in Table II. This is contrasted to the good" to very good brightness rating with the utilization of the present invention electroplating solutions containing the combination of the HEDP, ATMP and EDTMP ligands; however, these present invention solutions did not exhibit the disadvantages associated with the copper cyanide solution as heretofore described.

TABLE II Eleetroplating of brass and steel cathodes with Cu at pli 12.0 in a 1,000 ml. hull cell 1 Brightness Ligand] Percent range, Bright- Cu Cu in so- Temp. amperesl ness Test N o. Ligand ratio 2 lutien 3 C. it. rating Remarks on brightness quality CuCN-Standard n Brass 25 CN;Cu 3.8:1 1. 22 60 0-150 Good. Bright plate, dark in the LCDA. 26 CN:Cu 3.811 2.44 60 0-150 .-do Better than Test N0. 25.

On Steel 27 ON: Cu 3. 8:1 1. 22 60 0-150 Good... Bright plate, smudged, very good adhesion. 28 CN: Cu 3. 8:1 2. 4-1 60 0 150 ..do Do.

1 At amperes for 5 minutes using constant supply of current and agitating the bath by bubbling into it compressed clyinder air.

2 Molar ratio of Ligand acid, 100% to Cu. 3 From 01180 4 The wider the brightness range the better the plating; 0-150amperes/lt.'- maximum. 5 Subjective rating based on the width of the brightness range, uniformity of brightness, good adhesion of Cu to steel, the absence of pronounced sniudges, stains and discoloration.

LCDA=low current density area.

three ligands are used together.

Test Nos. 22 show the cooperative effect of the HEDP and EDTMP ligands. The cooperative effect of these combined ligands results in a brightness rating ranging from good to very good. Thus, the combination of l-lEDP and EDTMP also results in unexpected results in view of the fact that when either one of these individual ligands is utilized, the results are substantially less than when the two ligands are utilized together. However, one of the advantages of the present invention (i.e., HEDP ATMP EDTMP) is the fact that this three ligand-containing composition is at least as effective as the l-lEDP-EDTMP combination, but the former is less expensive than the latter. Specifically, ATMP, on a commercial basis, costs approximately 50 percent of the commercial cost of HEDP. Consequently, if part of the HEDP is replaced with ATMP, e.g., (HEDP EDTMP): Cu mole ratio (4.0 0.25): l (HEDP ATMP EDTMP): Cu mole ratio (2.0 2.0 0.25):l, the overall cost of the composition is substantially reduced and yet the effectiveness of the composition is substantially the same as compared to the use of the two ligand complex-containing material. Thus, the present invention not only exhibits a uniqueness in the end-use thereof, but the economics thereof is quite attractive.

EXAMPLE ll Example l was repeated in the same manner as set forth above, however, each electroplating solution was adjusted to a pH 10 in this Example ll as compared to the pH 8 of Example I plating solutions. The Hull Cell was the same in both examples.

The results obtained from this Example ll were substantially the same as those results shown in Table 1 (Example l).

For a comparative basis, test Nos. 25, 26, 27, and 28 I In conjunction with the utilization of the EDTMP ligand per se in an electroplating solution, this usage has been suggested in German Patent application 2,023,304 which was published Nov. 18, 1970 and which publication is incorporated herein by reference. In view of this German publication and the aforementioned US. Pat. No. 3,475,293, it can readily be seen that the unique combination of the HEDP, ATMP and EDTMP ligands of the present invention is an improvement over these publications and is unexpected in view of the results set forth in Example I above.

EXAMPLE Ill Where one so desires to achieve the cooperative effect derived from the present invention, other plating solutions can be prepared and different cathode and anode materials utilized all in an electrodeposition process. Thus, cathodes such as zinc and aluminum can be interexchanged with anodes prepared from copper, nickel, cadmium, iron, zinc, cobalt and cadmiumnickel materials. Furthermore, the plating solutions can be prepared utilizing salts (which supply the metal ion for the HEDP-ATMP-EDTMP complexes) such as copper carbonate, potassium carbonate, nickel carbonate, cadmium carbonate, iron chloride, zinc oxide, cobalt citrate, sodium zincate, nickel sulfate and iron sulfate.

it is to be understood that the aforegoing examples are merely illustrative of the present invention and are not to be considered as restrictive or limiting thereto and that other ramifications can be effected and variables changed all of which are within the scope of the present invention.

What is claimed is:

l. A process for the electrodeposition of a metal which comprises the step of electrolyzing an aqueous solution having a pH of from about 6.0 to about 13.0 of a composition comprising (i) a complex consisting of a diphosphonate ligand and (3) a complex consisting of a metal ion and an amino tri (methylene phosphonate) ligand; wherein said composition is present in'said solution in an amount sufficient to providefrom about 0.1 to about percent by weight, based on the weight of said solution, of said metal and wherein said diphosphonate to metal ion mol ratio is from about 1.011 to about 4.0:1, said tetra (methylene phosphonate) to metal ion mol ratio is from about 0. 1 :l to about 1.1 :1 and said tri (methylene phosphonate) to metal ion mol ratio is from about 0.5:1 to about 2:1; with the proviso that the mol ratio of the diphosphonate to metal ion and the tri (methylene phosphonate) to metal ion be higher in numerical value than the mol ratio of tetra (methylene phosphonate) to metal ion; said solution being at a temperature in which the solution produces galvanic deposits.

2. The process as set forth-in claim 1 wherein the metal ion is a transitional metal ion selected from the group consisting of gold, copper, iron, nickel, zinc and cadmium ions. g

3. The process as set forth in claim 1 wherein such tetra(methylene phosphonate) ligand is ethylenediamine tetra-(methylene phosphonic acid).

4. The process as set forth in claim 1 wherein such diphosphonate ligand is l-hydroxy, ethylidene-1,ldiphosphonic acid.

5. The process as set forth in claim 1 wherein such tri(methylene phosphonate) is amino tri(methylene phosphonic acid).

6. The process as set forth in claim 1 wherein said solution is maintained at a temperature of from about 40C to about 80C during the electrodeposition of said metal.

an ethylenediamine tetra (methylene phosphonate) (3) a complex consisting of a metal ion and an amino tri (methylene phosphonate) ligand; said composition being present in said solution in an amount sufficient to provide'from about 0.1 to about 5 percent by weight, based on the weight of said solution, of said metal; and wherein diphosphonate to metal ion mol ratio is from about 1.0:1 to about 4.0;1, said tetra (methylene phosphonate) to metal ion mol ratio is from about 0.1 :1 u

to about 1.1:1, and said tri (methylene phosphonate) to metal ion mol ratio is from about 0.5:1 to about 2:1, with the proviso that the mol ratio of the diphosphonate tometal ion and, the tri (methylene phosphonate) to metal ion be higher in numerical value than the mo] ratio of tetra (methylene phosphonate) to metal ion.

8. The bath as set forth in claim 2 wherein said tetra(methylene phosphonate) ligand is ethylenediamine tetra-(methylene phosphonic acid).

9. The bath as set forth in claim 2 wherein said diphosphonate ligand is l-hydroxy, ethylidene-1,1- diphosphonic acid.

10. The bath as set forth in claim 2 wherein said tri(methylene phosphonate) is amino tri(methylene phosphonic acid).

11. The bath as set forth in claim 2 wherein the metal ion is a transitional metal ion selected from the group consisting of gold, copper, iron, nickel, zinc and cadmium ions.

Claims

2. The process as set forth in claim 1 wherein the metal ion is a transitional metal ion selected from the group consisting of gold, copper, iron, nickel, zinc and cadmium ions.
3. The process as set forth in claim 1 wherein such tetra(methylene phosphonate) ligand is ethylenediamine tetra-(methylene phosphonic acid).
4. The process as set forth in claim 1 wherein such diphosphonate ligand is 1-hydroxy, ethylidene-1,1-diphosphonic acid.
5. The process as set forth in claim 1 wherein such tri(methylene phosphonate) is amino tri(methylene phosphonic acid).
6. The process as set forth in claim 1 wherein said solution is maintained at a temperature of from about 40*C to about 80*C during the electrodeposition of said metal.
7. A galvanic bath useful for the preparation of galvanic metal deposits which comprises a substantially cyanide-free aqueous solution having a pH of from about 6.0 to about 13.0 which contains a composition comprising (1) a complex consisting of a metal ion and an ethylenediamine tetra (methylene phosphonate) ligand, (2) a complex consisting of a metal ion and 1-hydroxy, ethylidene - 1, 1 - diphosphonate ligand and (3) a complex consisting of a metal ion and an amino tri (methylene phosphonate) ligand; said composition being present in said solution in an amount sufficient to provide from about 0.1 to about 5 percent by weight, based on the weight of said solution, of said metal; and wherein diphosphonate to metal ion mol ratio is from about 1.0:1 to about 4.0:1, said tetra (methylene phosphonate) to metal ion mol raTio is from about 0.1:1 to about 1.1:1, and said tri (methylene phosphonate) to metal ion mol ratio is from about 0.5:1 to about 2:1, with the proviso that the mol ratio of the diphosphonate to metal ion and the tri (methylene phosphonate) to metal ion be higher in numerical value than the mol ratio of tetra (methylene phosphonate) to metal ion.
8. The bath as set forth in claim 2 wherein said tetra(methylene phosphonate) ligand is ethylenediamine tetra-(methylene phosphonic acid).
9. The bath as set forth in claim 2 wherein said diphosphonate ligand is 1-hydroxy, ethylidene-1,1-diphosphonic acid.
10. The bath as set forth in claim 2 wherein said tri(methylene phosphonate) is amino tri(methylene phosphonic acid).
11. The bath as set forth in claim 2 wherein the metal ion is a transitional metal ion selected from the group consisting of gold, copper, iron, nickel, zinc and cadmium ions.