US3475293A - Electrodeposition of metals - Google Patents

Description

United States Patent Of U.S. Cl. 204-48 Claims ABSTRACT OF THE DISCLOSURE An electrically conductive medium for the electrodeposition of metals is described which comprises a neutral to alkaline aqueous dispersion of a complex consisting of a divalent metal ion and an organophosphorus ligand of the formula:

wherein n is an integer of from 2 to 3, M is a member selected. from the group consisting of hydrogen and an alkali metal cation and Z is a connecting radical equal in valence to n and containing not more than about 12 atoms exclusive of hydrogen in chemical combination and selected from the group consisting of (i) an aliphatic radical and (ii) an N-substituted aliphatic radical containing from 2 to 3 alkyl groups, said connecting radical having a carbon atom linked to the phosphorus atom in said ligand, said complex being present in said dispersion in an amount suflicient to provide from about 1% to about 5% by weight, based on the weight of the dispersion, of said divalent metal and the mol ratio of said divalent metal ion to said ligand is from about 1:2 to about 1:1, respectively.

This application is a continuation of Ser. No. 398,379, filed Sept. 22, 1964, now abandoned.

The present invention relates to the electro-deposition or electroplating of metals and to novel media which may be' employed in the electrodepo'sition 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 the electrodeposition of metals are well known and involve electrolyzing an electrically conductive medium (e.g., an electroplating bath) 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 transformed into a film or plate of elemental metal as they are electrically deposited upon the cathode.

Electroplating baths 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 3,475,293 Patented Oct. 28, 1969 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. I

It has been proposed heretofore in U.S. Patent 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.

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 neutral to alkaline dispersions or hereinafter defined complexes of metal ions and an organophosphorus ligand. The electrolysis of these dispersions results in metal deposits of uniform thickness which have a continuity and a 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 medium.

It is a still further object of this invention to provide processes for electroplating or electrically depositing a wide variety of metals on a spectrum of substrates.

Still further objects of the present invention will become apparent from the following description and the appended claims.

The present invention provides, in part, an electrically conductive medium comprising a neutral to alkaline aqueous dispersion of a complex consisting of (l) a divalent metal ion and (2) an organophosphorus ligand of the formula:

0 OM i OM n wherein n is an integer of from 2 to 3, inclusive, M is either a hydrogen ion, ammonium, lower alkyl amine or an alkali metal cation and Z is a connecting radical equal in valence to n and containing not morethan about 12 carbon atoms exclusive'of hydrogen in chemical combination and is selected from the group consisting of (i) an aliphatic radical, (ii) an N-substituted aliphatic radical containing from 2 to 3 alkyl groups in which the connecting radical has a carbon atom linked to a phosphorus atom in the ligand. This complex is present in such dispersion in an amount sufficient to electrically deposit the metal of a divalent met-a1 ion when an electric current is passed through said dispersion. In the above formula Z is a connecting radical equal in valence to n and contains no more than 12 atoms, exclusive of hydrogen, in chemical combination. The cherri- In the above medium the divalent metal ion is advantageously a divalent transitional metal ion and is preferably a divalent transitional metal ion selected from the group consisting of copper, iron, nickel, zinc and cadmium ions. The particular metal employed to form the aforementioned complex with the organophosphorus ligand will generally depend upon the metal which it is desired to electrically deposit.

THE ORGANOPHOSPHORUS LIGAND In the hereinbefore described formula for the organophosphorus ligand when Z is an aliphatic radical containing from 1 to 12 carbon atoms the ligand will preferably have the formula:

X 0M .1. l l Y OM 2 wherein X is selected from hydrogen, hydroxyl or a lower alkyl group containing from about 1 to about 4 carbon atoms and Y is a member selected from the group consisting of hydrogen, hydroxyl and lower alkyl containing from about 1 to about 4 carbon atoms, and M is as hereinbefore described.

In the above Formula I when Z is an N-substituted aliphatic connecting radical containing 3 alkyl groups the organophosphorus ligand will have the formula:

(III) III (fi/OM N- C-P Y OM a where X, Y and M are as hereinbefore described.

Particular classes of compounds falling within the scope of the foregoing general formula include aminotrit lower alkylidene phosphonic acid) compounds and specific compounds falling therein include, for example, aminotri- (methylene phosphonic acid), aminotri(ethylidene phosphonic acid), aminotri(isopropylidene phosphonic acid), aminodi(methylene phosphonic acid) mono(ethylidene phosphonic acid), aminodi(methylene phosphonic acid) mono(isopropylidene phosphonic acid), aminomonomethylene phosphonic acid) di(ethylidene phosphonic acid), aminomono(methylene phosphonic acid) diisopropylidene phosphonic acid) and the like.

Lower alkylidene diphosphonic acid compounds falling within the scope of the above general formula include methylene diphosphonic acid, ethylidene diphosphonic acid, isopropylidene diphosphonic acid, l-hydroxyethylidene diphosphonic acid, l-hydroxypropylidene diphosphonic acid, -butylidene diphosphonic acid and the like.

As noted hereinbefore M in the above formula may be either hydrogen or an alkali metal cation. It is preferred that M be an alkali metal cation such as sodium, potassium and lithium, and it is particularly preferred that M be potassium.

Particularly preferred organophosphorus ligands employed in the form of a divalent transitional metal ion complex, include, for example, pentapotassium amino(trimethylene phosphonate), tetrapotassium l-hydroxyethylidene diphosphonate, pentasodium aminotri(methylene phosphonate), tetrasodium l-hydroxyethylidene diphosphonate.

Of the above-described metal complexes those which are preferred are water soluble to an extent such as to provide from about 1% to about 5% by Weight of divalent transitional metal ion in water when dissolved therein.

THE ELECTRICALLY CONDUCTIVE MEDIUM The amount of any of the above-described complexes, consisting of a divalent metal ion, hereinbefore described, and any of the organophosphorous ligands hereinbefore described which may be present in the electrically conductive medium may vary considerably and will usually depend upon the solubility of the particular metal complex. Generally speaking the amount of complex is based upon the amount of metal employed and the metal complex is usually present in an amount which is sufiicient to provide from about 1% to about 5% by weight, based on the weight of the dispersion, of metal in the form of metal ion. Such metal complexes are usually substantially soluble under these circumstances. The particular concentrations of the complex within the above range -will depend primarily upon the particular metal of the metal complex. Thus, for example when the divalent metal ion is iron or copper the concentration of the complex preferably is a concentration sufficient to provide from about 1% to about 5% by weight of copper or iron. When the metal of the metal complex is nickel the concentration of the complex is preferably a concentration sufiicient to provide from about 1.5 to about 3% by weight of the nickel. In the case of zinc the concentration of the complex is preferably such as to provide a concentration from about 2% to about 5% by weight of the zinc; and in the case of cadmium the concentration of the complex is preferably such as to provide a concentration from about 1 to about 4% by weight of cadmium.

As noted hereinbefore the electrically conductive medium Which comprises an aqueous dispersion of a divalent metal ion and the hereinbefore described organophosphorous ligand is a neutral to alkaline medium and is usually characterized in having a pH in the range of from about 6. 0 to about 11.5. The pH of the medium will depend to some extent upon the divalent metal ion of the metal complex, 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 alkaline dispersion of divalent copper and any of the hereinbefore described organophosphorous ligands the pH of the medium may be in the range of from about 6.0 to about 10.0, the higher pHs being attained when M in the above described formulae 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 the pH of the medium is preferably in the range of from about 7.0 to about 7.5. If the electrically conductive medium containing a copper complex is to be used for plating, for example. copper on aluminum the pH of the medium may be in the range of from about 7.0 to about 10.0.

If the electrically conductive medium comprises an aqueous alkaline dispersion containing divalent iron ions and the aforementioned ligand the medium preferably has a pH in the range of from about 7.0 to about 9.0. 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 7.0 to about 8.0, 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 7 to about 9.0, more preferably from about 8.0 to about 9.0.

When the electrically conductive medium comprises an aqueous alkaline dispersion of a complex containing divalent nickel ions and the ligand the pH of the medium preferably should be in the range of from about 8.0 to about 10.5, or more preferably from about 8.0 to about 9.0, and 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 dispersion of a complex containing divalent zinc ions and the ligand, the pH of the medium usually should be in the range of from about 7.5 to about 11.5, preferably in the range of from about 7.5 to about 8.5, 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 dispersion of a complex containing divalent cadmium ions and the ligand, the pH of such medium usually should be in the range of from about 8.0 to about 10.0, preferably in the range of from about 8.0 to about 9.0, and such medium has been found to be particularly advantageous in the electrodeposition of cadmium on steel or brass.

The aqueous alkaline medium comprising an aqueous alkaline dispersion of any of the aforementioned complexes may contain in addition to the complexes, an excess of-ligand and from a practical standpoint it has sometimes been found more advantageous to have an excess of ligand in terms of a metal to ligand mol ratio as high as 1:2. Differently stated the ratio of divalent metal ion to ligand may be in the range of from about 1:2 to about 1:1 and when the mol ratio of 1:1 the aqueous medium will consist substantially of metal ions which are entirely complexed with the ligand and some excess of ligand having no divalent metal ions complexed therewith. When the mol ratio is from just above 1:1 to about 1:2 excess ligand will be present in the medium. Whether or not excess ligand will be present in the electrically conductive medium depends upon the par- .ticular divalent metal ion in the medium and the substrate or basis metal upon which the divalent metal is to be electrically deposited. By way of example, when the electrically conductive medium comprising an aqueous alkaline dispersion of copper ions and the ligand, the copper to ligand ratio will be in the range of from about 1 ion of copper to about 2 mols of ligand to about 1 copper ion to about 1 mol of ligand preferably a ratio of from about 111.5 to about 1:1.25.

By way of further example when the electrically conductive medium comprises a dispersion consisting of a complex containing divalent iron ions and the ligand, the metal ion:ligand ratio will preferably be a ratio in the range of from about 1:2 to about 1:1, most preferably from about 111.25 to 111. Also when the electrically conductive medium comprises an aqueous alkaline dispersion ofa complex of divalent nickel ions and the ligand the nickelzligand (ionzmol) ratio will preferably be in the range of from about 1:22 to about 1:1, more preferably from about 1:2 to about 1:1.4. When the electrically conductive medium comprises an aqueous alkaline disersion of a complex consisting of divalent zinc ions and the ligand, the zinc:ligand (ionzmol) ratio will preferably be in the range of from about 1:2 to 1:1, more preferably from about 121.5 to 1:125 and when the electrically conductive medium comprises an aqueous alkaline dispersion of a complex containing divalent cadmium ions and the ligands, the ratios are usually the same as the ratios of the divalent zinc and the ligand.

THE PREPARATION OF THE ELECTRICALLY 'CONDUCTIVE MEDIUM The electrically conductive medium, comprising the aqueous alkaline dispersion of the metal complex, may be prepared in a variety of Ways which will depend upon the particular class or species of ligand which it is desired to employ to form the metal complex and more particularly the divalent metal which it is desired to complex with the ligand. Although in many instances the metal complex may be synthesized prior to its dispersion in water it has been found generally desirable to dissolve component precursors of the complex in water to form the complex containing the desired divalent metal ion and any of the hereinbefore described ligands. The components of the metal complex which usually consist of an organo-phosphorus ligand, 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 ligand in water and thereafter to add the metal, usually in the form of a water soluble metal salt, to the medium and thereafter to add the alkali metal, also usually in the form of a water soluble salt.

It has been found particularly advantageous to disperse the ligand either in the acidic form (e.g., as an organophosphonic acid) or in the alkali metal ester form and to add to the resulting solution the divalent metal, in the form of a water soluble salt consisting of the divalent metal and a nonoxidizing anion. Alternatively the ligand, in the acid form, may be dissolved in water, the divalent metal salt added to the solution and thereafter the alkali metal is dissolved in the solution. The anions of the metal salts, e.g., the divalent metal and the alkali metal salts, are preferably nonoxidizing anions such as for example sulfate, chloride, phosphate, citrate, carbonate or acetate anions. Preferably however, such anions should be thermally decomposable anions, for example, carbonate or acetate anions.

When the ligand is added as the hydrogen or acid form it may also be desirable to add the alkali metal, in the form of a water soluble alkali metal salt, containing any of the anions above referred to but preferably a decomposable anion such as an acetate or a carbonate anion. When it is desired, for example, to prepare an aqueous alkaline dispersion of a complex consisting of divalent copper ions and the ligand either in the acid or alkali metal form appropriate quantities of copper carbonate, the ligand in the acid form, and an alkali metal carbonate are dissolved in water with agitation. During the addition of'the 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 specific examples, there is provided an aqueous alkaline dispersion of a complex from which, when an electric current is passed therethrough, the divalent metal can be deposited upon a suitable cathode.

A plating bath which has been found particularly advantageous may be prepared by first dissolving amino tri- (methylene phosphonic acid) in water. To the resulting solution there is added the desired amount of divalent metal carbonate and the resulting solution may then be neutralized or adjusted to the desired pH by the addition of an alkali metal carbonate.

THE ELECTRODEPOSITION PROCESS The present invention further provides a process for the electrodeposition of a divalent metal which comprises the steps of electrolyzing a neutral to alkaline dispersion of a metal complex consisting of any of the divalent metal ions hereinbefore described and any of the hereinbefore referred to organophosphorus ligands. The amount of complex present in the dispersion is an amount sufficient to provide from about 1% to about 5% by weight, based on the weight of the dispersion, of said divalent metal. By so proceeding divalent 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 alkaline dispersion, the bath is maintained at a temperature of from just above the freezing point to just below the boiling point of the aqueous alkaline dispersion. For reasons of current efiiciencies it has been found preferable to maintain the tem- 7 perature of the electrically conductive medium in the range of from about 50 C. to about 70 C.

The amount of current employed in the electrodeposition may vary widely depending upon the particular divalent metal ion in the form of a complex with the ligand, the particular ligand, the temperature of the medium and whether or not the medium is agitated during the passage of the electric current therethrough. Generally, the amount of current employed will be a current sufiicient to pro vide a current density of from about 1 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 5 to about 150 amperes per square foot and when the electrically conductive medium is agitated the curernt 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. As noted hereinbefore the amount of current employed will depend to some extent on the divalent metal which it is desired to deposit.

When it is desired, for example, to deposit or to electroplate copper the electrically conductive medium Will comprise an aqueous alkaline dispersion consisting of a complex of divalent copper ions and any of the ligands hereinbefore described and the current employed will be preferably an amount sufiicient 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 20 to about 60 amperes per square foot. When the medium is agitated the amount of current employed will be an amount sulficient to provide the current density of from about 5 to about 120 amperes per square foot.

In preferred processes, when it is desired to electrodeposit copper, the electrically conductive medium (e.g., the plating bath) will comprise an aqueous alkaline dispersion consisting of divalent copper ions and the ligand. 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 sufiicient to provide a current density in the range of from about 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 10 to about 100 amperes per square foot of electrode.

When it is desired to deposit or electroplate nickel the electrically conductive medium will comprise an aqueous alkaline dispersion consisting of divalent nickel ions and a ligand, 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 150 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 5 to about 50 amperes per square foot of electrode surface.

When it is desired to electrodeposit zinc the electrically conductive medium will comprise an aqueous alkaline dispersion consisting of a complex of divalent zinc ions and a ligand, the current employed will be an amount sulficient 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 suflicient to provide a current density of from about 5 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 5 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 dispersion consisting of a complex of divalent cadmium ions and a ligand. The current employed will be an amount sufiicient 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 the preferred amount of current will preferably be an amount sufficient to provide a current density in the range of from about 10 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 5 to about 50 amperes per square foot of electrode surface.

The time required to eletctroplate or to electrically deposit the divalent transitional 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, 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 amperes per square foot of electrode surface, through an aqueous alkaline dispersion of a complex consisting of divalent copper ions and tetrapotassium amino trimethyl phosphonate having a pH in the range of from about 7.0 to about 10.0. The amount or concentration of complex in the dispersion is an amount sufiicient to provide from about 1% to about 5% by Weight, based on the weight of the dispersion, of copper and the temperature of the dispersion is maintained within the range of from about 50 C. to about 70 C. 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 dispersion of a complex consisting of divalent nickel ions and tetrapotassium amino trimethyl phosphonate having a pH in the range of from about 8.0 to about 10.5. The concentration of the complex in the dispersion is sufficient to provide from about 1% to about 5% by weight, based on the Weight of the dispersion, of nickel and the temperature of the dispersion is maintained in the range of from about 50 C. to about 70 C. during the passage of the electric current therethrough.

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

EXAMPLE I Ten plating baths were prepared by dissolving an alkali metal carbonate, the below designated organophosphorus ligands and the below designated divalent metal salts in water in the proportions listed.

Plating bath 1 Ingredient: Percent Copper carbonate 3.11 Potassium carbonate 9.39 Aminotri(methylene phosphonic acid) 10.18

Watetr 77.32

r 9 Plating bath 2 Ingredient: Percent Nickel carbonate 3.62 Potassium caronate 9.22 Aminotri(methylene phosphonic acid) 10.32 Water 76.84

Plating bath 3 Ingredient: Percent Cadmium carbonate 2.91 Potassium carbonate 6.69 Aminotri(methylene phosphonic acid) 6.31 Water 84.09

Plating bath 4 Ingredient: Percent Iron chloride 10.34 Sodium carbonate 18.75 Aminotri(methylene phosphonic acid) 15.56 Water 55.35

Plating bath 5 Ingredient: 7 Percent Zinc oxide 2.30 Potassium carbonate 1 11.18 1 .Arninotri(methylene phosphonic acid) 10.49 Water 76.03

p Plating bath 6 Ingredient: Percent Copper carbonate 3.13 Potassium carbonate 10.01 1 hydroxyethylidene diphosphonic acid 7.00' .Water, 79.86

" Plating bath 7 Ingredient: Percent Potassium carbonate 12.97 Nickel carbonate 3.89 l-hydroxyethylidene idphosphonic acid 9.06 Water 74.08

Plating bath 8 Ingredient: Percent Cadmium carbonate 2.69 Potassium carbonate 6.14 l-hydroxyethylidene diphosphonic acid 4.33 Water 86.84

I Plating bath 9 Ingredient: I I Percent Iron chloride 6.21 Sodium carbonate 7.57 l-hydroxyethylidene diphosphonic acid 6.88 ,Water 79.34

' Plating bath 10 Ingredient: Percent Zinc oxide 2.18 Potassium carbonate 10.55 l-hydroxyethylidene diphosphonic acid 7.41 I Water 79.86-

- EXAMPLE II Ten plating baths were prepared by first dissolving the below designated organophosphorus ligands, and adding to these solutions the below designated divalent metal salts and thereafter-adding, to the resulting solution, an alkali metal carbonate, all ingredients being added in the percentages listed below.

10 Plating bath l1 Ingredient: 7 Percent Copper carbonate 3.12 Potassium carbonate 10.01 l-hydroxybutylidene diphosphonic acid 7.37 Water 79.50

Plating bath 12 Ingredient: Percent Nickel carbonate 3.88 Potassium carbonate 12.90 l-hydroxybutylidene diphosphonic acid 9.53 Water 73.69

Plating bath 13 Ingredient: Percent Cadmium carbonate 2.68 Potassium carbonate 6.14 l-hydroxybutylidene diphosphonic acid 4.54 Water 86.64

Plating bath 14 Ingredient: Percent Iron chloride 6.22 Sodium carbonate 7.59 l-hydroxybutylidene diphosphonic acid 6.92 Water 79.27

Plating bath 15 Ingredient: Percent Zinc oxide 2.18 Potassium carbonate 10.58 l-hydroxybutylidene diphosphonic acid 7.79 Water 79.45

Plating bath 16 Ingredient: Percent Copper carbonate 3.11 Potassium carbonate 10.00 Methylaminodi(methylenephosphonic acid) 6.89 Water 80.00

Plating bath l7 Ingredient: Percent Nickel carbonate 3.89 Potassium carbonate 12.97 Methylaminodi(methylene phosphonic acid) 8.95 Water 74.19

Plating bath 18 Ingredient: Percent Cadmium carbonate 2.69 Potassium carbonate 6.14 Methylaminodi(methylene phosphonic acid) 4.24 Water 86.93

Plating bath 19 Ingredient: Percent Iron chloride 6.21 Sodium carbonate 7.62 Methylaminodi(methylene phosphonic acid) 6.83 Water 79.34

Plating bath 20 Ingredient: Percent Zinc oxide 2.18 Potassium carbonate 10.55 Methylaminodi(methylene phosphonic acid) 7.29 Water 79.98

EXAMPLE III The electroplating solutions prepared as' described in Examples I and II were separately placed into a Hull cell constructed substantially as the electrolysis cell described in US. Patent 2,149,344. The cell had a capacity of 267 ml. Plates were made using cathodes described under the heading Basis Metal in the following table.

Current densities and bath temperatures are also designated (for each plating solution) in the following table.

Plating metal Current density, Temper- Time in amps/ ature minutes pH sq. ft. Basis metal 41 3 7. 2 24 37 8 7. 9 19 24 5 7. 5 10 41 10 7. 1 5 37 15 7. 6 24 24 3 7. 5 19 41 8 8. 2 10 37 5 7. 6 5 24 10 7. 1 24 41 15 7. 8 19 37 3 7. 3 10 24 8 8. 1 5 41 5 8. 2 24 37 10 7. 9 19 24 15 7. 2 10 41 3 7. 5 5 37 8 8. 24 24 7. 8 19 Steel..- 41 7. 1 10 Zinc 37 7. 6 5 Aluminum" Copper. Nickel. Cadmium.

The plates obtained varied in thickness and luster depending primarily upon the time and current density employed. All plates were of uniform thickness on the particular cathode and in many instances the copper plates were far brighter than those obtained from a similar bath in which copper cyanide instead of divalent copper, ion complex and the ligand comprising an electroplating bath of this invention.

What is claimed is:

1. A process for the electrodeposition of a divalent metal which comprises the steps of electrolyzing a neutral to alkaline aqueous dispersion of a complex consisting of a divalent metal ion and an organophosphorus ligand of the formula:

OOM

wherein n is an integer of from 2 to 3, M is a member selected from the group consisting of hydrogen, ammonia, lower alkyl amines wherein the alkyl group contains 1 to 4 carbon atoms, alkali metals and Z is a connecting radical equal in valence to n and containing not more than about 12 atoms exclusive of hydrogen in chemical combination and selected from the group consisting of (i) an aliphatic radical, (ii) an N-substituted aliphatic radical containing from 2 to 3 alkyl groups, said connecting radical having a carbon atom linked to the phosphorus atom in said ligand, said complex being present in said dispersion in an amount sufficient to provide from about 1% to about 5% by weight, based on the weight of the dispersion, of said divalent metal.

2. A process as in claim 1, wherein the divalent metal ion is a divalent transitional metal ion selected from the group consisting of copper, iron, nickel, zinc and cadmium ions.

3. A process as in claim 2, wherein the organophosphorus ligand in said complex is pentapotassium amino- (trimethylene phosphonate) the temperature of said dispersion is in the range of from about 50 to about 70 C., the density of the current which is passed through said dispersion is in the range of from about 5 to about 150 amperes per square foot of electrode surface and the pH of said dispersion is in the range of from about 7 to about 11.5.

4. A process for the electrodeposition of metal which comprises the steps of passing an electric current through an aqueous neutral to alkaline dispersion of a complex consisting .of a divalent transitional metal ion and an onganophosphorous ligand of the formula:

containing from about 1 to about 4 carbon atoms, and M is selected from the group consisting of hydrogen and an alkali metal cation; said dispersion being at a temperature in the range of from just above the freezing point to just below the boiling point of the dispersion; said complex being present in said dispersion in an amount sufficient to provide from about 1% to about 5% by weight, based on the weight of the dispersion, of said divalent metal; the density of said current being in the range of from about 1 to about 300 amperes per square foot of electrode surface.

5. A process for the electrodeposition of a divalent metal which comprises passing an electric current through -a neutral to alkalineaqucous dispersion of a complex consisting of a divalent transitional metal ion and an organophosphorus ligand of the formula:

wherein M is a member selected from the group consisting of hydrogen and an alkali metal cation and X is a member selected from the group consisting of hydrogen and a lower alkyl group containing from about 1 to about 4 carbon atoms and Y is a member selected from the group consisting of hydroXyl and a lower alkyl containing from about 1 to about 4 carbon atoms; said dispersion being at a temperature in the range of from just above the freezing point to just below the boiling point of said dispersion, said complex being present in said dispersion in an amount sufiicient to provide from about 1% to about 5% by weight, based on the Weight of the dispersion, of said divalent transitional metal, the density of said current being in the range of from about 1 to about 300 amperes per square foot of electrode surface employed.

6. A process as in claim 5, wherein the ligand is tetrapotassium l-hydroxyethylidene diphosphonate, the temperature of said dispersion is in the range of from about 50 to about 70 C., the density of the current which is passed through said dispersion is in the range of from about 5 to about amperes per square foot of electrode surface, and the pH of said dispersion is in the range of from about 7.0 to about 11.5.

7. A process for the electrodeposition of a divalent metal which comprises passing an electric current through a neutral to alkaline aqueous dispersion of a complex consisting of a divalent transitional metal ion and an organophosphorus ligand of the formula:

X o OM N 41 it \OM wherein X and Y are members selected from the group consisting of hydrogen, hydroxyl and lower alkyl radicals containing from about 1 to about 4 carbon atoms, and M is selected from the group consisting of hydrogen and an alkali metal cation; the temperature of said dispersion being in the range of from just above the freezing point to just below the boiling point of the dispersion, the density of said electric current being in the range of from about 1 to about 300 amperes per square foot of electrode surface. a

8. A process as in claim 7, wherein the organophosphorus ligand is tetrapotassium trimethylaminophosphonic acid, the temperature of said medium is in the range of from about 50 to about 70 C. and the density of the current which is passed through said dispersion is in the range of from about 5 to 150 amperes per square foot of electrode surface.

9. A process for the electrodeposition of copper which comprises passing an electric current at a density in the rang of from about 5 to about 150 amperes per square foot of cathode surface through an aqueous alkaline dispersion of a complex consisting of divalent copper ions and tetrapotassium aminotrimethyl phosphonic acid having a pH in the range of from about 7.0 to about 100, said complex being present in said dispersion in a concentration sufiicient to provide from about 1% to about 5% by weight, based on the weight of the dispersion, of copper, the temperature of said dispersion being maintained in the range of from about 50 C. to about 7 C.

10. A process for the electrodeposition of nickel which comprises passing an electric current at a density in the range of from about to about 150 amperes per square foot of cathode surface through an aqueous neutral to UNITED STATES PATENTS 2,599,807 6/1952 Bersworth 260500 2,841,611 7/ 1958 Bersworth 260500 3,149,151 9/1964 Schiefer et a1. 260-500 X 3,234,124 2/1966 Irani.

3,234,140 2/1966 Irani 260-500 X 3,298,956 1/1967 Irani et a1 260500 X 3,299,123 1/ 1967 Fitch et a1 260-500' OTHER REFERENCES Smith, R. L., The Sequestration of Metals, pp. 163- 171, 1959.

Chaberek, Stanley, et al., Organic sequestering Agents, pp. 354-355 .(1959) JOHN H. MACK, Primary Examiner G. L. KAPLAN, Assistant Examiner US. Cl. X.R.