Additive composition, acid zinc and zinc-alloy plating baths and methods for electrodedepositing zinc and zinc alloys

An additive composition is described with comprises a mixture of PA0 (a) poly(N-vinyl-2-pyrrolidone), and p0 (b) at least one sulfur-containing compound selected from compounds of the formulae EQU RS(R'O).sub.n H (I) or EQU S--[(R'O).sub.n H].sub.2 (II) PA0 wherein R is hydrogen or an alkyl group containing up to about 24 carbon atoms, each R' is independently an alkylene group containing 2 or 3 carbon atoms, and each n is independently an integer of from 1 to about 100. This additive composition is useful in acidic plating baths containing zinc or a mixture of zinc ions and at least one additional metal selected from nickel and cobalt. The plating baths also contain chloride ions or a mixture of chloride and sulfate ions.

TECHNICAL FIELD 
This invention relates to additive compositions, plating baths and methods 
of electrodepositing zinc and zinc alloys. More particularly, the 
invention relates to additive compositions and zinc and zinc-alloy plating 
baths containing poly(N-vinyl-2-pyrrolidone) and certain sulfur-containing 
compounds. 
BACKGROUND OF THE INVENTION 
Considerable attention has been directed to providing improved corrosion 
protection to metallic surfaces. One way of providing this corrosion 
protection is by electrodepositing a zinc coating on the surface. For 
decades, electroplated zinc has been used by the automative industry to 
provide an economical, highly corrosion-resistant coating. However, with 
today's unprecedented demands for higher quality and extended warranties, 
both the automotive manufacturers and their suppliers have had to develop 
new coatings. Zinc deposits from electroplating baths have been modified 
to provide improved overall brightness, range of allowable current 
densities and ductility. Good overall performance also is being 
demonstrated by zinc-cobalt and zinc-nickel alloy platings. These alloys 
are being introduced as replacements for conventional zinc electroplates 
in automotive as well as other applications requiring extended 
corrosion-resistance. The term "alloy", as used in this specification and 
claims is defined as a mixture of two or more metallic elements which may 
be microscopically homogeneous or microscopically heterogeneous. 
In recent years, the activity in the plating area has been concentrated on 
the development of cyanide-free alkaline baths or improvements in acid 
plating baths. This invention relates to acid zinc and zinc-alloy baths. 
Typically, acid zinc plating baths are based on a suitable inorganic zinc 
salt such as zinc chloride or zinc sulfate, and the baths usually include 
buffers such as the corresponding ammonium salt. Other additives are 
included in the baths to promote and improve ductility, brightness, 
throwing power and covering power. Surface active agents are normally 
included to improve crystal structure, reduce pitting, and increase the 
solubility of other additives. 
Brighteners for acid zinc baths are described in U.S. Pat. No. 3,920,528 
which are compounds having a carboxyl or a sulfo group attached directly 
or through an alkylene, vinyl, carbonyl or phenyl group to various 
heterocyclic rings including pyrrolidine or pyrrolidone. 
Polyvinylpyrrolidone (PVP) has been incorporated into zinc plating baths to 
impart various desirable properties. U.S. Pat. No. 4,397,717 describes 
alkaline zinc electroplating baths which contain various additives 
including polyvinylpyrrolidone. The use of polyvinylpyrrolidone in acid 
zinc plating baths is described in U.S. Pat. Nos. 3,594,291, 3,891,520, 
3,919,056, 4,226,682 and 4,444,630. In U.S. Pat. No. 3,594,291, a 
brightener system is described for acid zinc plating solutions which 
comprises the combination of N-polyvinylpyrrolidone with a secondary 
brightener which is a carbonyl compound such as acetophenone, 
benzalacetone, etc. The concentration of the polyvinylpyrrolidone in the 
bath is between 0.5 to 100 g/l. The combination is reported to produce a 
level of brightness which is greater than the individual effects. 
Polyvinylpyrrolidone is described as a surfactant in the acid zinc plating 
baths described in U.S. Pat. No. 3,919,056, and U.S. Pat. No. 4,226,682 
describes the use of certain specified dispersing agents including PVP in 
combination with a brightener compound such as 1-phenyl-1-penten-3-one. 
U.S. Pat. No. 2,495,668 describes plating baths for electrodepositing 
copper wherein the plating bath contains, in addition to copper cyanide, 
sulfur compounds such as .beta.-mercaptoethanol, dithiodiglycol, 
.beta.,.beta.'dihydroxyethyl sulfide and thioglycolic acid. Polymeric 
sulfur-containing compounds having the general formulae RS(R'O).sub.n H 
and S[(R'O).sub.n H].sub.2 wherein R is an alkyl group containing up to 
about 24 carbon atoms, each R' is independently an alkylene group 
containing 2 or 3 carbon atoms, and each n is independently an integer of 
from 1 to about 100 have been described in U.S. Pat. No. 4,229,268 as 
being useful in providing a level and bright zinc deposit from acid zinc 
plating baths. In U.S. Pat. No. 4,832,802, these polymeric 
sulfur-containing compounds, in combination with a ductility-improving 
amount of at least one specified acetylenic derivative, provide an 
additive composition for aqueous acidic zinc-nickel plating baths useful 
in depositing level and bright zinc-nickel alloy deposits. 
SUMMARY OF THE INVENTION 
An additive composition is described with comprises a mixture of 
(a) poly(N-vinyl-2-pyrrolidone), and 
(b) at least one sulfur-containing compound selected from compounds of the 
formulae 
EQU RS(R'O).sub.n H (I) 
EQU or 
EQU S--[(R'O).sub.n H].sub.2 (II) 
wherein R is hydrogen or an alkyl group containing up to about 24 carbon 
atoms, each R' is independently an alkylene group containing 2 or 3 carbon 
atoms, and each n is independently an integer of from 1 to about 100. This 
additive composition is useful in acidic plating baths containing zinc or 
a mixture of zinc ions and at least one additional metal selected from 
nickel and cobalt. The plating baths also contain chloride ions or a 
mixture of chloride and sulfate ions. The plating baths of the invention 
provide bright and ductile electrodeposits at low current densities.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The additive compositions of the present invention comprise a mixture of 
(a) poly(N-vinyl-2-pyrrolidone), and 
(b) at least one sulfur-containing component selected from compounds of the 
formulae 
EQU RS(R'O).sub.n H (I) 
EQU or 
EQU S--[(R'O).sub.n H].sub.2 (II) 
wherein R is hydrogen or an alkyl group containing up to about 24 carbon 
atoms, each R' is independently an alkylene group containing 2 or 3 carbon 
atoms, and each n is independently an integer of from 1 to about 100. In 
one embodiment, the additive compositions comprise from about 10 to about 
90 parts by weight of the poly(N-vinyl-2-pyrrolidone), and from about 10 
to about 90 parts by weight of the sulfur-containing component(b). 
The poly(N-vinyl-2-pyrrolidones) useful in the additive compositions of the 
present invention include polymers characterized by the following general 
formula 
##STR1## 
wherein n is an integer of from about 50 to about 5000. The degree of 
polymerization of the polyvinyl pyrrolidones is not critical. Thus, the 
polyvinyl-pyrrolidones may have molecular weights of from about 4500 to 
about 500,000. In one embodiment, n in Formula (III) is from about 90 to 
about 3500. Satisfactory results are obtained, for example, with a polymer 
having a molecular weight of from about 10,000 to about 30,000. 
Poly(N-vinyl-2-pyrrolidones) are available commercially from a variety of 
sources including GAF. For example, PVP K-15 is a 
poly(N-vinyl-2-pyrrolidone) is available from GAF Chemicals Corporation. 
The sulfur-containing compositions which have been found to be useful in 
the additive compositions and the plating baths of the present invention 
are characterized by the following general formulae 
EQU RS(R'O).sub.n H (I) 
EQU or 
EQU S--[(R'O).sub.n H].sub.2 (II) 
wherein R is hydrogen or an alkyl group containing up to about 24 carbon 
atoms, each R' is independently an alkylene group containing 2 or 3 carbon 
atoms, and each n is independently an integer of from 1 to about 100. The 
compositions according to Formula (I) can be prepared by reacting hydrogen 
sulfide, a mercaptan with from 1 to about 100 moles of ethylene or 
propylene oxide or mixtures of such oxides. An alkaline catalyst generally 
is used in promoting the condensation reaction. Examples of alkaline 
catalysts include alkali metal hydroxides, oxides and alcoholates. The 
preparation of compounds represented by Formula (I) is described in more 
detail in U.S. Pat. No. 2,494,610 which disclosure is hereby incorporated 
by reference. 
Compounds of the type represented by Formula (II) can be prepared by 
reacting one mole of hydrogen sulfide, 2-hydroxyethyl sulfide or 
3-hydroxypropyl sulfide with from 1 to 100 moles of ethylene or propylene 
oxide or mixtures of such oxides. A minimum of 2 moles of the oxide is 
required if the initial sulfur compound is hydrogen sulfide. Preferably, 
an excess of the oxide and an alkaline catalyst can be employed. 
In one preferred embodiment, the sulfur-containing composition is derived 
from one mole of hydrogen sulfide or 2-hydroxyethyl sulfide and up to 100 
moles of ethylene oxide. For example, a useful compound is obtained by 
reacting 1 mole of 2-hydroxyethyl sulfide with 21 moles of ethylene oxide. 
In another embodiment, the hydrogen sulfide is replaced by a mercaptan 
containing 6 to 24 carbon atoms. 
Sulfur-containing compositions of the type useful in the plating baths of 
the present invention also are available from GAF under the general trade 
designation "PEGOL TDG" and from the Alcolac Company under the general 
trade designation "SIPONIC". An example is PEGOL TDG 1250 which is the 
product obtained by ethoxylating 2-hydroxyethyl sulfide with about 28-30 
moles of ethylene oxide. 
The additive compositions of the present invention are useful in particular 
in acidic zinc and zinc alloy electroplating baths. The additive 
compositions comprising a PVP and the above-described sulfur-containing 
compounds produce zinc and zinc-alloy deposits exhibiting improved 
brightness and ductility at low current densities. 
The aqueous acidic zinc and zinc-alloy plating baths to which the additive 
compositions of the present invention may be added include the 
conventional zinc and ammonium containing plating baths as well as the 
ammonium-free acidic plating baths known to those skilled in the art. The 
zinc plating baths of the present invention contain free zinc ions and may 
be prepared with zinc sulfate, zinc chloride, zinc fluoborate, zinc 
acetate, zinc sulfamate and/or zinc alkane sulfonic acid, e.g., zinc 
methane sulfonate. The zinc ion concentration in the plating baths may 
range from about 5 g/l to about 180 g/l with concentrations of from about 
7.5 to about 100 g/l being preferred and from about 10-40 g/l being most 
preferred. 
When the plating baths are zinc-alloy plating baths, the baths contain 
nickel and/or cobalt ions in addition to zinc. The nickel ions may be 
present in the aqueous plating bath in the form of aqueous-soluble salts 
such as nickel chloride, nickel sulfate, nickel fluoborate, nickel 
acetate, nickel sulfamate, and nickel alkane sulfonic acid salts. When 
cobalt ions are present in the aqueous plating baths of the present 
invention, the cobalt is usually present in the form of cobalt sulfate, 
cobalt chloride, cobalt fluoborate, cobalt sulfamate and cobalt acetate. 
When present in the plating baths, the nickel ions and the cobalt ions 
generally are present in concentrations of from about 10 to about 150 g/l. 
The plating baths of the invention generally will contain one or more 
conducting salts such as sodium chloride, sodium fluoride, sodium sulfate, 
potassium chloride, potassium fluoride, potassium sulfate and ammonium 
chloride, ammonium fluoride and ammonium sulfate. The conductive salts may 
be present in the plating baths in amounts ranging from about 50 to about 
300 g/l or more. The plating baths of the present invention contain 
chloride ions or mixtures of fluoride ions and sulfate ions. Preferably 
the baths contain chloride ions but no sulfate ions. The concentration of 
chloride ions in the baths may range from about 50 to 200 g/l. More often, 
the concentration of chloride ions is from about 100 to 175 g/l. 
Boric acid may be included in the acid zinc and zinc-nickel plating baths 
of the present invention to serve as a weak buffer to control the pH and 
the cathode film. The boric acid also may be helpful in smoothing the 
deposit and is believed to have a cooperative effect with the leveling 
agents. The concentration of boric acid in the bath is not critical and 
generally will be in the range of up to about 60 g/l. In one embodiment 
the boric acid concentration in the plating baths is from about 10-40 g/l. 
The acidity of the acid baths of the present invention may vary from a pH 
of from 0 to about 6.5 or 7. The pH may be lowered if desired by the 
addition of acid solution such as 10% sulfuric acid solution. If the pH 
falls below the desired operating range, it can be increased by the 
addition of ammonium hydroxide or potassium hydroxide. Preferably, the 
acid-zinc plating baths are operated at a pH of from about 3 or 4 to about 
6.5. 
The amount of the additive compositions of the present invention which 
comprise PVP and at least one of the sulfur-containing components 
described above which is included in the acidic plating baths of the 
present invention is an amount sufficient to provide a bright zinc 
deposit. The additive composition may be preformed as a mixture and added 
to the plating bath, or the components of the additive composition can be 
added individually to the acid plating baths of the invention. The acidic 
plating baths of the present invention containing a 
poly(N-vinyl-2-pyrrolidone) and a sulfur-containing compound characterized 
by Formulae (I) and/or (II) can be prepared by either technique, and 
plating baths thus prepared generally will contain from about 0.1 to about 
10 g/l of the poly(N-vinyl-2-pyrrolidone) and from about 0.1 to about 15 
g/l of the sulfur-containing compound. 
When the additive compositions of the present invention are preformed and 
added to an acidic plating bath, the additive composition may be an 
aqueous additive composition comprising water, and 
(a) from about 10 to about 60 g/l of poly(N-vinyl-2-pyrrolidone) and 
(b) from about 25 to about 150 g/l of at least one of the sulfur-containing 
compounds of Formulae (I) and/or (II). 
The brightness of the zinc and zinc-alloy deposited from the aqueous acidic 
plating baths described above is improved when the bath also contains at 
least one carbonyl-containing compound such as aromatic and olefinic 
aldehydes, ketones, carboxylic acids and salts of carboxylic acids. The 
supplementary brighteners impart optimum leveling action over a wide 
current density range. The following compounds illustrate the types of 
carbonyl-containing compounds which are useful as brighteners in the 
plating baths of the invention, and these carbonyl compounds include 
aldehydes, ketones and carboxylic acids, esters and salts, particularly 
olefinic and carboxylic acids, esters and salts thereof: 
ortho-chlorobenzaldehyde, para-chlorobenzaldehyde, o-hydroxybenzaldehyde, 
aminobenzaldehyde, veratraldehyde, benzylidene acetone, coumarin, 
3,4,5,6-tetrahydrobenzaldehyde, acetophenone, propiophenone, furfurylidene 
acetone, 3-methoxybenzal acetone, benzaldehyde, vanillin, 
hydroxybenzaldehyde, anisicaldehyde, benzoic acid, sodium benzoate, sodium 
salicylate, 3-pyridine carboxylic acid (nicotinic acid), methacrylic acid, 
methyl methacrylate, sodium methacrylate, etc. Mixtures of one or more of 
the acids with one or more ketones also are useful. When employed in the 
baths of the invention, the carbonyl-containing brighteners will be 
included within the range of from about 0.02 to about 5 g/l. The 
carbonyl-containing brighteners may be added directly to the plating 
baths, or the brighteners can be included in the additive compositions of 
the invention, and the composition can thereafter be added to or used in 
the preparation of the acidic plating baths of the invention. When 
included in the aqueous additive compositions, the additive compositions 
may contain from about 50 to about 200 g/l of the carbonyl brightener. 
The properties of the zinc and zinc-alloy deposited from the aqueous acidic 
plating baths of the invention may be enhanced further by including in the 
bath, (or additive composition) small amounts of at least one anionic 
aromatic sulfonic acid or salt thereof. These compounds are obtained by 
the polycondensation of formaldehyde and an aromatic sulfonic acid which 
generally is a naphthalene sulfonic acid. Polycondensation products of 
this type are known compounds and their production has been described in 
the literature such, for example, Houben-Weyl, "Methoden Der Organishen 
Chemie", Vol. XIV/2 at page 316, and said description is hereby 
incorporated by reference. The utility of these condensation products in 
acid zinc baths is described in U.S. Pat. Nos. 3,878,069 and 4,075,066. 
The general method of preparing these polycondensation products involves 
reaction of a formaldehyde solution with naphthalene sulfonic acid at a 
temperature of from about 60.degree. C. to about 100.degree. C. until the 
formaldehyde odor has disappeared. Similar products can be obtained by 
sulfonation of naphthalene formaldehyde resins. The condensation products 
obtained in this manner contain two or more naphthalene sulfonic acids 
linked by methylene bridges which can have from one to three sulfonic acid 
groups. 
Some examples of aromatic sulfonic acids which may be used include: a 
bath-soluble salt of tetrahydronaphthalene sulfonic acid such as those 
available commercially from DuPont; a bath-soluble salt of a xylene 
sulfonic acid such as those available from Arco Chemical Company under the 
general trade designation "Ultrawet"; and a bath-soluble salt of cumyl 
sulfonic acid. 
These anionic aromatic sulfonic acid compounds may be introduced into the 
plating baths either in their acid form or as the water-soluble salts 
which may be the sodium or potassium salts. 
Polycondensation products of these types are available commercially from 
GAF under the general trade designations BLANCOL N and BLANCOL DISPERSANT; 
from BASF under the designation TAMOL NNO; from Kokko Corporation under 
the designation DEMOL N; and from Stepan Chemical Company under the 
designation STEPANTAN A. These condensation products are included in the 
baths of the present invention in amounts which may be varied depending 
upon other ingredients in the plating bath, and generally, the amounts 
which improve the brightness is from about 0.1 to about 15 g/l of plating 
bath. 
The plating baths of the invention also may contain at least one nonionic 
ethylene oxide and/or propylene oxide condensate surfactant. These 
surfactants may be selected from the group consisting of ethoxylated alkyl 
phenols, ethoxylated fatty alcohols, ethoxylated fatty acids, ethoxylated 
fatty acid amides, polyethylene oxide condensates, and block copolymers of 
ethylene oxide and propylene oxide based on propylene glycol or ethylene 
glycol. Generally, the surfactants will contain up to about 40 or more 
ethylene oxide units. The amount of nonionic surfactant included in the 
baths of the invention may vary over a wide range although it is preferred 
to include from about 0.5 to about 10 g/l of the condensate in the bath. 
The ethoxylated alkyl phenols may be represented by the formula 
##STR2## 
wherein R is an alkyl group containing up to about 20 carbon atoms and n 
is an integer from about 10 to about 30. Preferably the alkyl group 
contains from about 6 to 20 carbon atoms. Examples of such alkyl groups 
include octyl, isooctyl, nonyl, dodecyl, octadecyl. Ethoxylated alkyl 
phenols are available commercially under a variety of trademarks such as 
"Surfonic" from Jefferson Chemical Co., "Renex" from Atlas Chemical 
Industries, Inc., and "Igepal" from GAF Corporation Chemical Products. 
Polyethylene oxide or polyethylene glycol condensates having different 
molecular weights have been found to give good results. Condensates of 
this type which may be represented by the general formula 
EQU HO(CH.sub.2 CH.sub.2 O).sub.n H (V) 
wherein n is an integer from about 5 to about 100 or more are known in the 
art and are commercially available such as for example under the general 
trade designation Carbowax from Union Carbide. Specific examples include 
Carbowax No. 1000 which has a molecular weight range of from about 950 to 
1050 and contains from 20 to 24 ethoxy units per molecule. Carbowax No. 
4000 has a molecular weight range of from about 3000 to 3700 and contains 
from 68 to 85 ethoxy units per molecule. 
Ethoxylated aliphatic alcohols are useful as surfactants in the plating 
baths of the invention and may be characterized by the formula 
EQU RO(CH.sub.2 CH.sub.2 O).sub.n -H (VI) 
wherein R is an alkyl group containing from about 8 to 24 carbon atoms and 
n is an integer of from 5 to about 30. Fatty alcohols such as tridecyl 
oleyl and stearyl are preferred examples. A number of ethoxylated 
aliphatic alcohols are available commercially such as from Emery 
Industries under the general trademark "Trycol". A specific example is 
"Trycol OAL-23" which is an ethoxylated oleyl alcohol. 
Alkoxylated alcohols also are available from Chemax, Inc. under the general 
trade designation "Chemal". Examples include Chemal TDA which is an 
ethoxylated tridecyl alcohol, Chemal OA which is an ethoxylated oleyl 
alcohol and Chemal LA, an ethoxylated lauryl alcohol. 
The surfactant also may be an ethoxylated fatty acid represented by the 
formula 
EQU RC(O)--O(CH.sub.2 CH.sub.2 O).sub.n H (VII) 
or an ethoxylated fatty acid amide represented by the formula 
EQU RC(O)--N(H)(CH.sub.2 CH.sub.2 O).sub.n H (VIII) 
wherein R is an alkyl carbon chain containing from about 8 to 24 carbon 
atoms and n is an integer from about 5 to about 20. 
The ethoxylated fatty acid can be obtained by reacting ethylene oxide with 
a fatty acid such as oleic acid, stearic acid, palmitic acid, etc. The 
ethoxylated fatty acids are available commercially such as from Armak 
Industries, Chemical Division under the trademark "Ethofat". Specific 
examples are: Ethofat C/15, coco acid ethoxylated with 5 moles of ethylene 
oxide, and Ethofats O/15 and O/20, which are oleic acid reacted with 5 and 
10 moles of ethylene oxide respectively. The ethoxylated fatty acid amides 
can be obtained by reacting ethylene oxide with a fatty acid amide such as 
oleamide, stearamide, coconut fatty acid amides and lauric amide. The 
ethoxylated fatty acid amides, which may also be identified as ethoxylated 
alkylolamides are commercially available from, for example, The Stepan 
Chemical Company under the general trade designation Amidox, and from 
Armak under the trademark ETHOMID. 
Another type of nonionic ethoxylated surfactant which is useful in the 
plating baths of the invention are block copolymers of ethylene oxide and 
propylene oxide based on a glycol such as ethylene glycol or propylene 
glycol. The copolymers based on ethylene glycol generally are prepared by 
forming a hydrophilic base by reaction of ethylene oxide with ethylene 
glycol followed by condensation of this intermediate product with 
propylene oxide. The copolymers based on propylene glycol similarly are 
prepared by reacting propylene oxide with propylene glycol to form the 
intermediate compound which is then condensed with ethylene oxide. By 
varying the proportions of ethylene oxide and propylene oxide used to form 
the above copolymers, the properties may be varied. Both of the above 
types of copolymers are available commercially such as from BASF Wyandotte 
under the general trademark PLURONIC. The condensates based on ethylene 
glycol are identified as the "R" series, and these compounds preferably 
contain from about 30 to about 80% of polyoxyethylene in the molecule and 
may be either liquids or solids. The condensates based on propylene glycol 
are identified generally by BASF Wyandotte as the "F", "L", or "P" series 
and these may contain from about 5 to about 80% of ethylene oxide. The "L" 
series of propylene glycol based copolymers are liquids, the "F" series 
are solids and the "P" series are pastes. The solids and pastes can be 
used when they are soluble in the bath formulation. The molecular weights 
of these block copolymers range from about 400 to about 14,000. 
The acidic plating baths of the present invention also may be improved by 
the incorporation therein of small amounts of bath-soluble metal salts of 
the sulfate ester of 2-ethyl-1-hexanol. These sodium salts are available 
commercially from a number of vendors including, for example, Niaset 
Corporation under the designation NIAPROOF O8; The Henkel Chemicals 
Company (Canada) under the designation SULFOTAX CA; from BASF under the 
trade designation LUGALVAN TC-EHS; etc. From about 0.1 to about 15 g/l of 
these salts can be included in the plating baths of the present invention. 
The acid plating baths of the present invention deposit a level, bright and 
ductile zinc or zinc alloy on substrates at any conventional temperature 
such as from about 25.degree. C. to about 60.degree. C. Still plating 
baths generally will be operated at a lower range of the temperature such 
as from about 25.degree. C. to about 40.degree. C. whereas high-speed 
plating baths for strip or wire-plating may be operated over the entire 
range of from about 25.degree. C. to about 60.degree. C. The baths of the 
present invention may also be used in barrel plating. If the bath is to be 
agitated, an antifoaming agent should be included. An example of a useful 
antifoaming agent is a mixture of Dow Corning A and sodium sulfate. 
Solvents for improving the solubility of benzylidene acetone in the plating 
baths and additive compositions are also desirable. Examples of 
solubilizers include: 2-methoxy ethanol; ethylene glycol ethyl ether; 
propylene glycol methyl ether; propylene glycol-n-butyl ether, and butyl 
cellosolve. 
The following examples illustrate the additive compositions or concentrates 
which may be prepared and utilized in accordance with the invention for 
preparing or maintaining acid baths of the invention and/or improving the 
performance of the baths. 
______________________________________ 
Additive Composition-1 
PVP 50 g 
Ethoxylated (21 ETO) 2-hydroxyethyl 
50 g 
sulfide 
Additive Composition-2 
PVP 30 g/l 
TDG-1250 75 g/l 
Water to 1 liter 
Additive Composition-3 
PVP K-15 36 g/l 
TDG-1250 86 g/l 
Sodium benzoate 132 g/l 
Water to 1 liter 
Additive Composition-4 
Propylene glycol methyl ether 
600 cc 
Benzylidene acetone 60 g/l 
Blancol N 0.34 g/l 
PVP K-15 0.12 g/l 
Chemal TDA-15 0.44 g/l 
TDG-1250 0.29 g/l 
Sodium benzoate 0.44 g/l 
Water to 1 liter 
Additive Composition-5 
Chemal TDA-15 57.3 g/l 
Blancol N 44.0 g/l 
pH to 6.0-6.5 with HCl 
Water to 1 liter 
______________________________________ 
The following Examples 1-10 illustrate typical aqueous acidic zinc and zinc 
alloy plating baths to which various additive compositions may be added in 
accordance with the present invention. 
______________________________________ 
Example 1 
Zinc chloride 41.6 g/l 
Potassium chloride 229 g/l 
Boric acid 20 g/l 
Example 2 
Zinc chloride 105 g/l 
Potassium chloride 210 g/l 
Boric acid 20 g/l 
Example 3 
Zinc chloride 28 g/l 
Ammonium chloride 202.5 g/l 
Example 4 
Zinc chloride 33.4 g/l 
Ammonium chloride 60.75 g/l 
Potassium chloride 137.4 g/l 
Boric acid 38.75 g/l 
Example 5 
Zinc chloride 38.5 g/l 
Potassium chloride 67.5 g/l 
Ammonium chloride 76.3 g/l 
Sodium chloride 56.4 g/l 
Boric acid 22.5 g/l 
Example 6 
Zinc chloride 20.8 g/l 
Zinc sulfate monohydrate 14.0 g/l 
Potassium sulfate 60.0 g/l 
Potassium chloride 114.5 g/l 
Boric acid 10.0 g/l 
Example 7 
Zinc Chloride 100 g/l 
Nickel Chloride 155 g/l 
Ammonium Chloride 240 g/l 
Concentrated Ammonium Hydroxide 
75 g/l 
Solution 
Example 8 
Zinc Chloride 35 g/l 
Nickel Sulfate 102 g/l 
Ammonium Chloride 120 g/l 
Concentrated Ammonium Hydroxide 
40 g/l 
Solution 
Example 9 
Zinc chloride 73 g/l 
Cobalt chloride hexahydrate 
32 g/l 
Sodium chloride 125 g/l 
Boric acid 30 g/l 
Example 10 
Zinc chloride 35 g/l 
Nickel chloride hexahydrate 
40 g/l 
Cobalt chloride hexahydrate 
20 g/l 
Boric acid 30 g/l 
______________________________________ 
The following examples illustrate the aqueous acidic plating baths of the 
invention. The utility of the baths is demonstrated by plating steel Hull 
Cell panels on a 267 ml. Hull Cell. 
Bath A 
Bath of Example 1 to which is added 1% of Additive Composition-3 and 
______________________________________ 
Chemal TDA-15 1.72 g/l 
Blancol N 1.32 g/l 
Benzylidene acetone 0.045 g/l 
Propylene glycol methyl ether 
0.45 g/l 
______________________________________ 
Bath B 
Bath of Example 3 to which is added 
______________________________________ 
Additive Composition 3 at 1% 
Additive Composition 4 at 0.75 cc/l 
Additive Composition 5 at 3% 
______________________________________ 
A 2 amp, 5 minute Hull Cell panel at 110.degree. F. with mechanical 
agitation is ductile and bright overall. 
Bath C 
Bath of Example 4 to which is added 
______________________________________ 
Additive Composition 3 at 1% 
Additive Composition 4 at 0.75 cc/l 
Additive Composition 5 at 3% 
______________________________________ 
A 2 amp, 5 minute Hull Cell panel at 110.degree. F. with mechanical 
agitation is ductile and bright down into extremely low current densities. 
Bath D 
Bath of Example 5 to which is added 
______________________________________ 
Additive Composition 3 at 1% 
Additive Composition 4 at 0.75 cc/l 
Additive Composition 5 at 3% 
______________________________________ 
A 2 amp, 5 minute Hull Cell panel at 110.degree. F. with mechanical 
agitation is ductile and bright down into extremely low current densities. 
Bath E 
Bath of Example 6 to which is added 
______________________________________ 
Additive Compsition 3 at 1% 
Additive Composition 4 at 0.75 cc/l 
Additive Composition 5 at 3% 
______________________________________ 
A 2 amp, 5 minute Hull Cell panel at 110.degree. F. with mechanical 
agitation is ductile and bright up to 125 apsf. The results are improved 
over a similar bath containing sulfate ions but no chloride ions. 
While the invention has been explained in relation to its preferred 
embodiments, it is to be understood that various modifications thereof 
will become apparent to those skilled in the art upon reading the 
specification. Therefore, it is to be understood that the invention 
disclosed herein is intended to cover such modifications as fall within 
the scope of the appended claims.