US3758386A

US3758386A - Novel zinc plating process

Info

Publication number: US3758386A
Application number: US00591412A
Authority: US
Inventors: C Chan
Original assignee: M&T Chemicals Inc
Current assignee: M&T HARSHAW
Priority date: 1966-11-02
Filing date: 1966-11-02
Publication date: 1973-09-11
Anticipated expiration: 1990-09-11
Also published as: CH508731A; ES346650A1; DE1621119B2; GB1212536A; SE338910B; NL6714923A; DE1621119A1

Abstract

AND ANHYDRIDES THEREOF, WHEREIN N IS AN INTEGER 1-4 AND R'''''' IS SELECTED FROM THE GROUP CONSISTING OF A HYDROCARBYL GROUP AND AN INERTLY SUBSTITUTED HYDROCARBYL GROUP.

R''"-(COOH)N

WHEREIN R IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, ALKYL, ARYL, AND HETEROCYCLIC OXYGEN AND SULFUR RADICALS, AND R'' AND R" ARE EACH SELECTED FROM THE GROUP CONSISTING OF ALKYL AND ARYL RADICALS; AND AT LEAST ONE ORGANIC ACID COMPONENT OF THE FORMULA:

O=CH-R, AND R''-C(=O)-R"

THIS INVENTION RELATES TO NOVEL COMPOSITION AND TO A PROCESS OF PRODUCING BRIGHT ZINC DEPOSITS WHICH COMPRISES PASSING CURRENT FROM AN ANODE TO A METAL CATHODE THROUGH AN AQUEOUS ALKALINE PYROPHOSPHATE SOLUTION CONTAINING AT LEAST ONE ZINC COMPOUND PROVIDING ZINC IONS FOR ELECTROPLATING ZINC AND AT LEAST ONE ORGANIC CARRIER COMPOUND SELECTED FROM THE GROUP CONSISTING OF: (A) BIS(SULFONAPHTHYL) METHANE AND SALTS THEREOF, (B) NAPHTHALENE DERIVATIVES WHICH CONTAIN SUBSTITUENTS SELECTED FROM THE GROUP CONSISTING OF SULFONIC ACIDS AND THEIR ALKALI METAL SALTS, HYDROXYL, AMINO, AND IMINO RADICALS, (C) BENZENE DERIVATIVES CONTAINING SUBSTITUENTS SELECTED FROM THE GROUP CONSISTING OF SULFONIC ACIDS AND THEIR SALTS WITH ALKALI METAL, AMMONIUM, ALKYL, AND IMINO RADICALS, AND (D) ALLYL SULFONIC ACID AND ITS SALTS WITH ALKALI METALS AND AMMONIUM; AT LEAST ONE CARBONYL COMPOUND HAVING A STRUCTURAL FORMULA SELECTED FROM THE GROUP CONSISTING OF:

Description

United States Patent 3,758,386 NOVEL ZINC PLATING PROCESS Chee Keung Chan, Murray Hill, N.J., assignor to M&T Chemicals Inc., New York, N.Y. No Drawing. Filed Nov. 2, 1966, Ser. No. 591,412

Int. Cl. C23b 5/10 US. Cl. 204-55 26 Claims ABSTRACT OF THE DISCLOSURE This invention relates to novel compositions and to a process of producing bright zinc deposits which comprises passing current from an anode to a metal cathode through an aqueous alkaline pyrophosphate solution containing at least one zinc compound providing zinc ions for electroplating zinc and at least one organic carrier compound selected from the group consisting of:

at least one carbonyl compound having a structural formula selected from the group consisting of:

wherein R is selected from the group consisting of hydrogen, alkyl, aryl, and heterocyclic oxygen and sulfur radicals, and R and R are each selected from the group consisting of alkyl and aryl radicals; and at least one organic acid component of the formula:

and anhydrides thereof, wherein n is an integer l-4 and R is selected from the group consisting of a hydrocarbyl group and an inertly substituted hydrocarbyl group.

This invention relates to the electrodeposition of bright zinc from an alkaline pyrophosphate bath. More particularly, this invention relates to improved brightener compositions, bath compositions, and to methods of using and preparing such brightener compositions and bath compositions.

Alkaline solutions containing complex compounds of zinc and alkali metal pyrophosphates have been proposed as a replacement for the cyanide bath in processes for the electrodeposition of bright zinc due to the troublesome and costly disposal problems associated with the use of cyanide baths. However, the electrodeposition of zinc using a pyrophosphate bath may give relatively poor low current density coverage, spore formation, roughness, lack of brightness, and non-uniform deposits. Furthermore, anode corrosion may result in passivation of the anode. In addition, undesirable precipitates may form during operation which tend to clog filter systems and may result in intermittent operation due to frequent change of filter media. Attempts to overcome the de' ficiencies of the bath by the addition of certain expensive additives have met with only partial success and pyrophosphate zinc plating baths containing these additives have not attained widespread commercial acceptance.

It is an object of this invention to provide novel processes and compositions for electroplating of bright zinc plate. Other objects will be apparent to those skilled-inthe-art on inspection of the following description.

In accordance with certain of its aspects, this invention relates to a process of producing bright zinc deposits which comprises passing current from an anode to a metal cathode through an aqueous alkaline pyrophosphate solution containing at least one zinc compound providing zinc ions for electroplating zinc and at least one organic carrier compound selected from the group consisting of:

(a) bis[sulfonaphthyl] methane and salts thereof,

(b) naphthalene derivatives which contain substituents selected from the group consisting of sulfonic acids and their alkali metal salts, hydroxyl, amino, and imino radicals,

(c) benzene derivatives containing substituents selected from the group consisting of sulfonic acids and their salts with alkali metal, ammonium, alkyl, and imino radicals, and

(d) allyl sulfonic acid and its salts with alkali metals and ammonium;

wherein R is selected from the group consisting of hydrogen, alkyl, aryl, and heterocyclic oxygen and sulfur radicals, and R and R" are each selected from the group consisting of alkyl and aryl radicals; and at least one organic acid compound of the formula:

0 ugle and anhydrides thereof, wherein n is an integer 1-4 and R" is selected from the group consisting of a hydrocarbyl group and inertly substituted hydrocarbyl group.

Examples of suitable organic carrier compounds (corresponding to groups (a)-(d) set forth above) which may be used according to the invention are set forth in Table I.

TABLE 1 Organic carrier compounds bis [sulfonaphthyl] methane,

sodium salt of bis[sulfonaphthyl] methane, potassium salt of bis [sulfonaphthyl] methane, ammonium salt of bis[sulfonaphthyl] methane;

Typical bis[sulfonaphthyl] methane compounds (and salts thereof) which may be used include compounds of the formula:

wherein each of m and k is an integer -3 such that the sum rm-i-k is at least one and preferably 1-6. Examples of salts of such compounds include:

I SOaNa SOaNa t t-o I H m 0 3K 3K OaK etc.

In the above formulas, it is understood that all unsub stituted carbon atoms are bonded to hydrogen atoms.

sodium allyl sulfonate Suitable carbonyl compounds of the aldehyde and keone type which cooperate effectively with the other additives of the invention and may be used in the processes and compositions of the invention have a structural formula selected from the group consisting of:

R\ R 0:0 and wherein R is selected from the group consisting of hydrogen, alkyl, aryl, and heterocylic radicals containing oxygen and/or sulfur as the hetero-atoms, and R and R" are each selected from the group consisting of alkyl and aryl radicals. Both the alkyl and the aryl radicals in R, R, and R" may contain substituents such as alkoxy or hydroxy radicals. Table II sets forth suitable examples of carbonyl compounds which may be used in combination with the other additives according to the invention:

TABLE II Aldehydes formaldehyde benzaldehyde meta-hydroxy-benzaldehyde para-hydroxy-benzaldehyde ortho-hydroxy-benzaldehyde piperonal veratraldehyde (i.e. 3,4-dimethoxy-benzaldehyde) isovanillin (i.e. 3-hydroxy-4-methoxy-benzaldehyde) vanillin ethyl ether beta-methoxy-propionaldehyde furfural glyceraldehyde ethyl vanillin anisaldehyde salicylaldehyde propyl sultone thiophene-Z-aldehyde Ketones acetophenone acetylacetone isophorone dihydroxy acetone Examples of suitable organic acid compounds of the formula and anhydrides thereof, wherein n is an integer 1-4 and R' may be selected from the group consisting of a hydrocarbyl radical and an inertly substituted hydrocarbyl radical, are provided in Table III.

In this compound, R may be a hydrocarbyl radical preferably selected from the group consisting of alkyl, alkenyl, cycloalkyl, aralkyl, aryl, alkaryl, including such radicals when inertly substituted. When R' is alkyl, it may typically be straight chain alkyl or branched alkyl, including methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-amyl, neopentyl, isoamyl, nhexyl, isohexyl, heptyls, octyls, decyls, dodecyls, tetradecyl, octadecyl, etc. Preferred alkyls includes lower alkyl i.e. having less than about 8 carbon atoms i.e. octyls and lower. When R" is alkenyl, it may typically be vinyl, allyl, l-propenyl, methallyl, buten-l-yl, buten-2-yl, buten- 3-yl, penten-l-yl, hexenyl, heptenyl, octenyl, decenyl, dodecenyl, tetra-decenyl, octadecenyl, etc. When R is cycloalkyl, it may typically be cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, etc. When R' is aralkyl, it may typically be benzyl, fl-phenylethyl, -phenylpropyl, fi-phenylpropyl, etc. When R is aryl, it may typically be phenyl, naphthyl, etc. When R is alkaryl, it may typically be tolyl, xylyl, p-ethylphenyl, p-nonylphenyl, etc. K may be inertly substituted e.g. may bear a non-reactive substituent such as alkyl, aryl, cycloalkyl, aralkyl, alkaryl, alkenyl, ether, halogen, nitro, ester, etc. Typical substituted alkyls include 3-chloropropyl, Z-ethoxyethyl, carboethoxy-methyl, etc. Substituted alkenyls include 4-chlorobutyl, 'y-phenyl-propenyl, chloroallyl, etc. Substituted cycloalkyls include 4 methyl-cyclohexyl 4-chlorocyclohexyl, etc. Inertly substituted aryl includes chlorophenyl, anisyl, biphenyl, etc. Inertly substituted aralkyl includes chlorobenzyl, p-phenylbenzyl, p-methylbenzyl, etc. Inertly substituted alkaryl includes 3-chloro-5-methylphenyl, 2,6- di-tert-butyl-4-chlorophenyl, etc. Other suitable R' groups include alkoxyalkyl, alkoxyaryl, aryloxyalkyl, alkylene, alkenylene, alkynyl, as well as trivalent and tetravalent hydrocarbyl and inertly substituted hydrocarbyl groups.

TABLE 111 Organic acids (and anhydrides) acetic acid acetic anhydride chloroacetic acid chloroacetic anhydride dichloroacetic acid dichloroacetic anhydride trichloroacetic acid trichloroacetic anhydride bromoacetic acid bromoacetic anhydride dibromoacetic acid dibromoacetic anhydride tribromoacetic acid tribromoacetic anhydride iodoacetic acid iodoacetic anhydride methoxyacetic acid methoxyacetic anhydride ethoxyacetic acid ethoxyacetic anhydride phenoxyacetic acid phenoxyacetic anhydride 2-hydroxyethoxyacetic acid malonic acid malonic anhydride succinic acid succinic anhydride glutaric acid glutaric anhydride adipic acid adipic anhydride pimelic acid pimelic anhydride fumaric acid fumaric anhydride The halogenated organic carboxylic acids which may be added, either as such or e.g. as their anhydrides or salts (typically the sodium salt), to zinc plating baths in practice of this invention may typically include:

(a) Monohalogenated aliphatic monocarboxylic acids having at least two carbon atoms,

(b) Polyhalogenated aliphatic monocarboxylic acids having at least two carbon atoms,

(c) Monohalogenated aliphatic polycarboxylic acids having at least two carbon atoms,

(d) Polyhalogenated aliphatic polycarboxylic acids having at least two carbon atoms,

(e) Monohalogenated aromatic monocarboxylic having at least two carbon atoms,

(f) Monohalogenated aromatic polycarboxylic having at least two carbon atoms,

(g) Polyhalogenated aromatic monocarboxylic having at least two carbon atoms, and

(h) Polyhalogenated aromatic polycarboxylic having at least two carbon atoms.

acids acids acids acids Typical illustrative monohalogenated aliphatic monocarboxylic acids having at least three carbon atoms which may be employed may include:

2-chloropr0pionic acid 3-bromopropionic acid 3-iodopropionic acid Z-chlorobutanoic acid chloropivalic acid (monochlorinated tertiary pentanoic acid) 2-chloropentanoic acid Typical illustrative polyhalogenated aliphatic monocarboxylic acids having at least three carbon atoms which may be employed may include:

2,2-dichloropropionic acid 2,2,3-trich1oropropionic acid Typical illustrative monohalogenated aliphatic polycarboxylic acids having at least three carbon atoms which may be employed may include:

chloromalonic acid 2-chlorosuccinic acid 2-bromosuccinic acid 2-chloroadipic acid Typical illustrative polyhalogenated aliphatic polycarboxylic acids which may be employed may include:

2,2-dichlorosuccinic acid 2,2-dichloroadipic acid tetrachlorosuccinic acid 2,3-dibromosuccinic acid 3,3-diiodosuccinic acid 3,4-dichloroadipic acid Typical illustrative monohalogenated aromatic monocarboxylic acids which may be employed may include:

3-chloro-4-sulfobenzoic acid 3-bromo-4-sulfobenzoic acid Typical illustrative monohalogenated aromatic polycarboxylic acids which may be employed may include:

4-chlorophthalic acid 2-bromoterephthalic acid Typical illustrative polyhalogenated aromatic monocarboxylic acids which may be employed may include:

3,S-dichloro-4-sulfobenzoic acid 3,6-dibromo-4-sulfobenzoic acid Typical illustrative polyhalogenated aromatic polycarboxylic acids which may be employed may include:

3,4-dichlorophthalic acid 3,4-dibromophthalic acid 4,5-dichlorophthalic acid Other acids falling within the scope of this invention will be apparent to those skilled-in-the-art.

According to another aspect of the invention, a mixture of organic acids may be employed in combination with the other additives. Examples of such mixtures include acetic and chloroacetic acid, acetic acid and hydroxyacetic acid, trichloroacetic acid and hydroxyacetic acid, dihloroacetic acid and bromoacetic acid, etc. Preferred mixtures of acids which may be used include mixtures of hydroxyacetic acid and at least one other acid such as acetic acid, iodoacetic acid, chloroacetic acid, bromoacetic acid, etc. The use of hydroxyacetic acid in combination with at least one other acid (such as acetic acid, a haloacetic acid, or a polyhaloacetic acid) results in further improved reduction and/or inhibition of undesirable precipitate formation in alkaline pyrophosphate plating baths containing zinc ions. Alkoxy and aryloxy acids,

including methoxyacetic acid, phenoxyacetic acid, etc. may be employed.

According to still another aspect of the invention, a used pyrophosphate zinc plating bath which is contaminated with undesirable precipitate may be regenerated by the addition of suitable quantities of organic carrier, carbonyl compound, and organic acid compound.

The basis metal onto which the bright zinc deposits of this invention may be applied may include ferrous metals such as steel; copper, including its alloys such as brass, bronze, etc.; die cast metals which may bear a plate of another metal such as copper; thin metal coating, e.g. of silver, nickel, or copper, on a non-conductive article (such as a rigid or flexible plastic) which coating may be applied by chemical reductive techniques, etc.

According to another aspect of the process of the invention, the preferred operating conditions such as pH, temperature, and current density may vary depending upon the paticular bath composition and the nature of the article being plated. In general, good bright zinc deposits can be obtained within a specific range of operating conditions. For example, when the pH is within the desired range a zinc deposit may attain maximum brightness and when the pH is within the desired range the current efliciency may be optimum.

Table IV sets forth the ranges and conditions suitable for the bath compositions which may be used according to the process of this invention.

Vigorous and uniform agitation of the plating bath may be provided, if necessary, either by mechanical or solution agitation during the electrodeposition. Such agitation may permit the use of higher plating current densities on the article being plated. During the plating operation, it is desirable to remove or eliminate metal and other contaminants to insure a bright metal zinc deposit. Such contamination from metal ions (such as cadmium, copper, iron, and lead) may be the most troublesome, and conventional purification methods may be used to eliminate or reduce the amounts of such contaminants. Other types of contaminants (such as organic contaminants) may also be eliminated or reduced by circulation of the pyrophosphate solution using a suitable filter media such as activated carbon or other types of exchange or absorption media.

Although numerous combinations of organic carrier compounds, carbonyl compounds, and organic acid compounds may be used according to the invention, a particularly preferred embodiment of the invention comprises the utilization of an alkaline pyrophosphate zinc plating bath containing organic carrier bis[sulfonaphthyl] methane (or the alkali metal salts thereof), furfuraldehyde as the carbonyl compound, and an aqueous mixture containing acetic acid and hydroxyacetic acid as the organic acid component. This composition may give particularly good results with respect to reduction of roughness, increase in brightness of the zinc deposit, reduction of spore formation, and elimination or reduction of excessive precipitate formation.

Thus, according to a preferred embodiment, the invention relates to a process for the production of bright zinc deposits which may comprise electrodepositing bright zinc by passing current from an anode to a metal cathode through an aqueous alkaline pyrophosphate solution containing at least one zinc compound providing zinc ions for electroplating zinc and about 0.5 to about 18.0 grams per liter of an organic carrier compound, from about 0.025 to about 0.2 gram per liter of a carbonyl compound selected from the group consisting of aldehydes and ketones, and about 4.0 g./l. to about 50.0 g./l. of at least one organic acid selected from the group consisting of acetic acid, haloacetic acids, alkoxyacetic acids, phenoxyacetic acid, and hydroxyacetic acids (preferably a mixture of acetic acid and hydroxyacetic acid).

While the additives and carriers of this invention may be used at any concentrations within the broad ranges stated above, it is generally preferable to employ the organic carriers in concentration of from about 4.0 to about 14.0 grams per liter, the most preferable concentration being about 9-10 g./l.; the carbonyl compounds in concentrations of from about 0.05 to about 0.1 gram per liter, and the organic acids in concentrations of from about 12.0 grams per liter to about 22.0 grams per liter, and most preferably about 16 grams per liter.

The additives and carriers may be added either separately or simultaneously to the zinc plating bath. For the carbonyl compound, it is often most convenient to incorporate the compound into the bath in the form of dilute aqueous solution. Aqueous solutions containing alkali metal hydroxide may be used for the preparation of baths with higher concentrations of carbonyl compounds. To prepare solutions of carbonyl compounds which have longer shelf lives, the carbonyl compounds may be dissolved in the form of an aqueous-alcoholic solution. The organic acid additive may similarly be added to the zinc plating bath, preferably in the form of an aqueous solution. When a mixture of acids (e.g. acetic acid and hydroxyacetic acid) is used, the mixture may contain suitable amounts of water as a diluent. Concentrated solutions may be diluted directly in the bath.

The zinc plating operation may be carried out at a temperature at which the bath remains a liquid. Generally, temperatures of from about 20 C. to 6 5 C. may be employed, typically temperatures of from 45 C. to 55 C. and preferably temperatures of from 50 C. to 52 C.

The following examples are submitted for the purpose of illustration only and are not to be construed as limiting the scope of the invention in any way. The compositions of the metal panels used in these plating experiments were as follows.

(I) STEEL PANEL Type: Low carbon cold rolled steel SAE number: 1010 Element: Percent by weight Carbon 0.08-0.13. Manganese 0.30-0.60. Phosphorus 0.040 (maximum). Sulfur 0.050 (maximum). Iron Remainder.

Impurities Element: Percent by weight Silicon 0.08 Nickel 0.07 Chromium 0.04 Molybdenum 0.02 Aluminum 0.002

Arsenic 0.032

Copper Trace 9 11) BRASS PANEL Type: 70% copper and 30% zinc; half-hard brass (ingot not sand cast) 10 EXAMPLE 3 This example may illustrate the advantage of the use of an organic acid in combination with a bis [sulfonaphthyl] Element; Percent by Weight 5 methane compound (including salts thereof) and a car- Copper 65.00 (min.)69.00 (max.). bonyl Compound Tin 1.50 In a control experiment, 300 milliliters of pyrophos- Lead 5 5 (max) phate zinc plating Solution A as described in Example 1 Zinc Remainden may be added to 0.36 gram of the sodium salt of bis[sullmpurities 1O fonaphthyl] methane and 0'03 gram of furfuraldehyde. Element: Percent by Weight The resulting solution (pH 11 3) may be heated to 50 C. Nickel O5. and a steel panel was plated in a standard Hull cell at 1 Iron 0 5. ampere for ten m nutes. The resulting zinc plated control Silicon (max panel may contain black spore-deposits. Repetition of 15 this control plating procedure using the same bath with EXAMPLE 1 another steel panel at 1.5 amperes for ten minutes may A pyrophosphate stock solution designated Zinc-Platgivea zinc-plated steel panel which was disfigured with ing Solution A may be prepared containing the following unsightly black spores on the surface of the zinc plate. components: In a process carried out in accordance with this inven- Zn g /1 22 0 tion, the same solution asernployed in the preceding ex- K P O periment but with the addition of 2.5 grams of a mixture fi 8 of 0.1 gram of glacial acetic acid and 2.4 grams of by- P0 i" 7 5 droxyacetic acid may be employed to plate an identical 0 steel panel at 1.5 amperes for ten minutes at 50 C. in 10 5 a standard Hull cell, the pH of the solution being 11.3, P as in the preceding experiment. No spores may be formed To 3.5 liters of Solution A may be added about 3.8 on the experimental zinc-plated steel panel. Repetition of grams of the sodium salt of bis[sulfonaphthyl] methane, the experiment using the same zinc plating solution but at 0.44 gram of furfuraldehyde, and 6.3 grams of hydroxy- 1.0 ampere for 10 minutes may give a zinc-plated steel acetic acid, the electrometeric pH of the solution being panel free of spores. approximately 11.2. The temperature of the bath may be held at about 25 C. and a 6.25 cm. x 10 cm. x 0.15 cm. EXAMPLES 4-13 h lf-h d brass panel (70% b i h copper d 30% Table V gives examples of various combinations of zinc) of the same composition as brass panel II as precarbony1 COmPOImd, Organic carrier compound, and viously described may be immersed in the bath and zinc gamc d Compound which y P Significantly plated using a current of three amperes for a time period improved Spore-free bright Zinc Plate with reduced anode of te i t A ll t bright i l t d panel was deterioration and reduced sludge or precipitate formation obtained. The anodes remained clean and no spores were in the Plating hath- A yp basic Zinc p g bath which formed on the zinc-plated panel. Similar results are oby he used in Combination with the ingredients of Table tained using steel panels. 40 V y be composed as follows:

EXAMPLE 2 Zinc (as the metal) g./l 22.8-27.0 This example illustrates the regeneration of a deterio- $32 9 6 ;:ig rated zinc plating bath. 3.5 liters of a pyrophosphate K P 0, g zfi stock Solution A containing 0.1 g./l. of \furfuraldehyde 6 2 7 7 and 1.2 g./l. of the sodium salt of bis[sulfonaphthyl] e 03 methane may be used for several days. At the end of this 10 3 5 time, a crust of precipitate may have formed at the bottom 21 C 5 of the bath and the bath may no longer produce satisfacp6 tory bright zinc deposits. To a sample of 3.5 liters of In the examples of Table the bath temperature may this spent bright zinc plating bath may be added sufficient he maintained at about the P y he PP hydroxyacetic acid to dissolve the precipitate in the bath mately and mild agitation y be p y The (approximately 15-25 grams), Glacial acetic acid (0,5 zinc-plating experiments may be carried out in 3. Hull g./l.) may be added, the anodes were bagged, and several cell for 10 minutes at 1 ampere, using steel panels as brass panels were plated using a current of 4 amperes for previously described. i

TABLE V Ex. No. Carbonyl compound G./l. Organic carrier compound G./l. Organic acid compound 4 p-Hydroxy benzaldehyde 0.25 bis(sulionaphthyl)methaue* 1.2 Iodoacetic acid, 0.2 (g./l.). 5 Veratraldehyde 0.1 do 1.2 Glacial acetic acid, 0.2 (g./l.). 6. Benzaldchyde.-. 1.2 Hydroxyacetic acid, 8 (g./l.). 7- Fur 1. 2 0.2 g./l. glacial acetic aci plus 8 g./l. hydroxyacetic acid. 8- Glyceraldehydc 1.2 Trichloroacetic acid, 0.32 (g./l.). 9- Anisaldehyde 1.2 Bromoacetic acid, 0.75 (g./1.). 10 Salicylaldehyde propyl sultoneI- 1. 2 Trichloroacetic acid, 0.32 (g./l.). 11 Ethyl vanillin 1. 2 0.2 g./l. glacial acetic acid plus 8 g./l. hydroxyacetic acid. 12 Thiophene-Z-aldehyde 1.2 Bromoacetic acid, 0.75 (g./1.). 1% Aeetylacetnne 1.2 Iodoacetic acid, 0.2 (g./l.).

As sodium salt.

twenty minutes. Excellent bright zinc plated brass panels may be obtained and it may be noted that the andoes remained clean even at current densities in the range of 30 amperes per square decimeter (ASD).

EXAMPLES 14-23 Improved results may be obtained in a similar manner when steel panels are zinc plated in a standard Hull cell using the same plating conditions as in the preceding 11 Examples 4-13, but employing the following acids at a concentration of 0.2 g./l. in combination with 3.4 g./l. of the sodium salt of bis[sulfonaphthyl]methane and 2.03 g./l. of furfuraldehyde.

Example No. Organic acid 14 'Butyric acid. 15 2-bromobutyric acid. 16 Propionic acid. 17 a-Chloropropionic acid. 18 Succinic acid. 19 Benzoic acid. 20 Glutaric acid. 21 Adipic acid. 22 'Succinic anhydride. 23 Phthalic acid.

Similar results may be obtained using sodium pyrophosphate in place of potassium pyrophosphate in the pyrophosphate zinc plating Solution A.

Although this invention has been illustrated by reference to specific examples, numerous changes and modifications thereof which clearly fall within the scope of the invention will be apparent to those skilled-in-the-art.

I claim:

1. The process of producing bright zinc deposits which comprises passing current from an anode to a metal cathode through an aqueous alkaline pyrophosphate solution containing at least one zinc compound providing zinc ions for electroplating zinc and at least one organic carrier compound selected from the group consisting of:

-(a) bis (sulfonaphthyl) methane and salts thereof;

(b) naphthalene derivatives wherein each substituent is selected from the group consisting of sulfonic acids and their alkali metal salts, a hydroxyl radical, an amino radical, and an imino radical;

(c) benzene derivatives containing substituents selected from the group consisting of sulfonic acids and their alkali metal and ammonium salts, an alkyl radical, and an imino radical; and

(d) allyl sulfonic acid and its alkali metal and ammonium salts;

at least one carbonyl compound having a structural formula selected from the group consisting of wherein R is selected from the group consisting of hydrogen, an alkyl radical, an aryl radical, and heterocyclic radicals containing oxygen and sulfur as the hetero-atoms, and R and R" are each selected from the group consisting of alkyl and aryl radicals;

and at least one organic acid compound and anhydrides thereof of the formula:

wherein n is one and R' is selected from the group consisting of methyl, hydroxymethyl, halomethyl groups, and haloethyl groups.

2. The process of producing bright zinc deposits as claimed in claim 1 wherein the organic acid is a mixture of glacial acetic acid and hydroxyacetic acid.

3. The process of producing bright zinc deposits as claimed in claim 1 wherein the carbonyl compound is furfuraldehyde and the organic acid is a mixture of glacial acetic acid and hydroxyacetic acid.

4. The process of producing bright zinc deposits as claimed in claim 1 wherein the carbonyl compound is acetylacetone and the organic acid is iodoacetic acid.

5. The process of producing bright zinc deposits as claimed in claim 1 wherein the carbonyl compound is benzaldehyde and the organic acid is hydroxyacetic acid.

6. The process of producing bright zinc deposits as claimed in claim 1 wherein the carbonyl compound is furfuraldehyde and the organic acid is chloropropionic acid.

7. A zinc plating composition comprising at least one organic carrier compound selected from the group consisting of:

(a) bis(sulfonaphthyl) methane and salts thereof;

(b) naphthalene derivatives wherein each substitu ent is selected from the group consisting of sulfonic acids and their alkali metal salts, a hydroxyl radical, an amino radical, and an imino radical;

(c) benzene derivatives containing substituents selected from the group consisting of sulfonic acids and their alkali metal and ammonium salt, an alkyl radical, and an imino radical; and

(d) allyl sulfonic acid and its alkali metal and ammonium salts;

at least one carbonyl compound having a structural formula selected from the group consisting of 0:0 and wherein R is selected from the group consisting of hydrogen, an alkyl radical, an aryl radical, and bet: erocyclic radicals containing oxygen and sulfur as the hetero-atoms, and R and R are selected from the group consisting of alkyl and aryl radicals;

and at least one organic acid compound of the formula (and anhydrides thereof):

wherein n is one and R'" is selected from the group consisting of methyl, hydroxymethyl, halomethyl groups, and haloethyl groups.

8. The zinc plating composition according to claim 7 wherein the organic acid is a mixture of glacial acetic acid and hydroxyacetic acid.

9. The zinc plating composition according to claim 7 wherein the carbonyl compound is furfuraldehyde and the organic acid is a mixture of glacial acetic acid and hydroxyacetic acid.

10. The zinc plating composition according to claim 7 wherein the carbonyl compound is acetylacetone and the organic acid is iodoacetic acid.

11. The zinc plating composition according to claim 7 wherein the carbonyl compound is benzaldehyde and the organic acid is hydroxyacetic acid.

12. The zinc plating composition according to claim 7 wherein the carbonyl compound is furfuraldehyde and the organic acid is wchloropropionic acid.

13. The process of producing bright zinc deposits which comprises passing current from an anode to a metal cathode through an aqueous alkaline pyrophosphate solution containing at least one zinc compound providing zinc ions for electroplating zinc and at least one organic carrier compound which is selected from the group consisting of:

(a) bis(sulfonaphthyl) methane and the sodium,

potassium, or ammonium salts thereof; (b) naphthalene derivatives selected from the group consisting of 2,6-naphthalene-disulfonic acid; 8-amino-l-naphthalene-Z-sulfonic acid; 6,6'-irnino-bis-(1-naphthol-3) sulfonic acid; Z-naphthol-6,8-disulfonic acid; 2,3 dihydroxy 6 naphthalene sulfonate, so-

dium salt; 1,S-dihydroxy-naphthalene; |1,4-naphthalene diol; (c) benzene derivatives selected from the group consisting of:

sodium salt of benzene monosulfonate; benzene sulfonamide; sodium toluene sulfonate; o-sulfobenzimide; and (d) sodium allyl sulfonate; at least one carbonyl compound having a structural formula selected from the group consisting of wherein R is selected from the group consisting of hydrogen, an alkyl radical, an aryl radical, and heterocyclic radicals containing oxygen and sulfur as the hetero-atoms, and R and R" are each selected from the group consisting of alkyl and aryl radicals; and at least one organic acid compound and anhydrides thereof of the formula:

wherein n is l and R' is selected from the group consisting of methyl, hydroxymethyl, halomethyl and haloethyl groups.

14. The process of producing bright zinc deposits as claimed in claim 13 wherein the carbonyl compound is furfuraldehyde and the organic acid is a mixture of glacial acetic acid and hydroxyacetic acid.

15. The process of producing bright zinc deposits as claimed in claim 13 wherein the carbonyl compound is acetylacetone and the organic acid is iodoacetic acid.

16. The process of producing bright zinc deposits as claimed in claim 13 wherein the carbonyl compound is benzaldehyde and the organic acid is hydroxyacetic acid.

17. The process of producing bright zinc deposits as claimed in claim 13 wherein the carbonyl compound is furfuraldehyde and the organic acid is chloropropionic acid.

18. A zinc plating composition comprising an aqueous alkaline pyrophosphate solution containing at least one zinc compound providing zinc ions for electroplating zinc and containing in combination at least one organic carrier compound selected from the group consisting of (a) bis(sulfonaphthyl) methane and the sodium,

potassium, or ammonium salts thereof; (b) naphthalene derivatives selected from the group consisting of:

2,6-naphthalene-disulfonic acid; 8-amino-1-naphthalene-2-sulfonic acid; 6,6'-imino-bis-(l-naphthol-3) sulfonic acid; 2-naphthol-6,8-disulfonic acid; 2,3-dihydroxy-6-naphthalene sulfonate sodium salt; 1,5-dihydroxy-naphthalene; 1,4-naphthalene diol;

wherein R is selected from the group consisting of hydrogen, an alkyl radical, an aryl radical, and heterocyclic radicals containing oxygen and sulfur as the hetero-atoms, and R' and R" are each selected from the group consisting of alkyl and aryl radicals;

and at least one organic acid compound and anhydrides thereof of the formula:

I O RIII C wherein n is l and R is selected from the group consisting of methyl, hydroxymethyl, halomethyl and haloethyl groups.

19. The zinc plating composition according to claim 18 wherein the carbonyl compound is furfuraldehyde and the organic acid is a mixture of glacial acetic acid and hydroxy acetic acid.

20. The zinc plating composition according to claim 18 wherein the carbonyl compound is acetylacetone and the organic acid is iodoacetic acid.

21. The zinc plating composition according to claim 18 wherein the carbonyl compound is benzaldehyde and the organic acid is hydroxyacetic acid.

22. The zinc plating composition according to claim 18 wherein the carbonyl compound is furfuraldehyde and the organic acid is u-chloropropionic acid.

23. A process of producing bright zinc electrodeposits which comprises passing current from an anode to a metal cathode through an aqueous alkaline pyrophosphate solution containing at least one zinc compound providing zinc ions for electroplating zinc and containing in combination about:

05-180 g./1. of the sodium salt of bis(sulfonaphthyl) methane;

0.025-0.2 g./l. of furfuraldehyde; and

4.0-50 g./l. of hydroxyacetic acid.

24. A process of producing bright zinc electrodeposits which comprises passing current from an anode to a metal cathode through an aqueous alkaline pyrophosphate solution containing at least one zinc compound providing zinc ions for electroplating zinc and containing in combination about:

0.3-18.0 g./l. of the sodium salt of bis(sulfonaphthyl) methane;

0.025-0.2 g./l. of furfuraldehyde; and

4.0-50.0 g./l. of a mixture of acetic acid and hydroxyacetic acid.

25. A zinc plating composition comprising an aqueous alkaline pyrophosphate solution containing at least one zinc compound providing zinc ions for electroplating zinc References Cited and containing in combination about: UNITED STATES PATENTS 0.5-18.0 g./l. of the sodium salt of bis(su1fonaphthyl) methane; 905,785 12/1908 Bianco 204-55 (1025-02 g,/l. of furfuraldehyde; and 5 1,109,181 9/1914 Sacerdote 204-55 of hydroxyacetic acicL 2,277,668 3/1942 Ruebeusaal 20455 2,451,426 10/1948 Balr et a1 20455.1 26. A zinc plating composition consisting essentlally 2 488 246 11/1949 Stareck et a1. 204 55 of an aqueous alkaline pyrophosphate solution contain- 3296104 1/1967 Eppensteiner 204 55 ing at least one zinc compound providing zinc ions for 10 electroplating zinc and containing in combination about: DANIEL WYMAN, Primary Examiner 0.518.0 g./l. of the sodium salt of bis(sulfonaphthyl) w H. CANNON, Assistant Examiner methane;

0.0250.2 g./l. of furfuraldehyde; and US. Cl. X.R.

4.o-so g./l. of a mixture of acetic acid and hydroxy- 15 204-114 acetic acid.