U.S. patent application number 11/425294 was filed with the patent office on 2006-12-21 for zinc-nickel alloy electroplating system.
This patent application is currently assigned to PAVCO, Inc.. Invention is credited to Leonard L. JR. Diaddario, Bradley J. Proper, Gregory E. Storer.
Application Number | 20060283715 11/425294 |
Document ID | / |
Family ID | 37507624 |
Filed Date | 2006-12-21 |
United States Patent
Application |
20060283715 |
Kind Code |
A1 |
Diaddario; Leonard L. JR. ;
et al. |
December 21, 2006 |
ZINC-NICKEL ALLOY ELECTROPLATING SYSTEM
Abstract
The invention provides an aqueous zinc-nickel alloy
electroplating composition particularly useful in an electroplating
method for depositing a zinc-nickel alloy layer on a substrate,
wherein the deposited layer exhibits uniform nickel concentration
and good aesthetics across a broad range of current densities. The
electroplating composition comprises an electrolyte composition and
an organic composition. In one embodiment, the electrolyte
composition comprises a zinc ion source, a nickel ion source, a pH
buffering agent and at least one additional salt, and the organic
composition comprises a Class I nickel brightener, a Class II
nickel brightener, an aromatic carboxylic acid, an aldehyde or
ketone compound, and a non-ionic or anionic surfactant. The
electroplating composition is particularly free of chelators and
free ammonium-producing agents.
Inventors: |
Diaddario; Leonard L. JR.;
(Independence, OH) ; Storer; Gregory E.;
(Eastlake, OH) ; Proper; Bradley J.; (Garfield
Heights, OH) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA
101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Assignee: |
PAVCO, Inc.
|
Family ID: |
37507624 |
Appl. No.: |
11/425294 |
Filed: |
June 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60692204 |
Jun 20, 2005 |
|
|
|
Current U.S.
Class: |
205/245 |
Current CPC
Class: |
C25D 3/565 20130101;
C25D 3/562 20130101 |
Class at
Publication: |
205/245 |
International
Class: |
C25D 3/56 20060101
C25D003/56 |
Claims
1. An aqueous zinc-nickel alloy electroplating composition
comprising an electrolyte composition and an organic composition,
wherein the electrolyte composition comprises: a) a zinc ion
source; b) a nickel ion source; c) a pH buffering agent; and d) at
least one additional inorganic salt; the organic composition
comprises: a) a Class I nickel brightener; b) a Class II nickel
brightener; c) an aromatic carboxylic acid; d) an aldehyde or
ketone compound; and e) a non-ionic or anionic surfactant; and
wherein the electroplating composition is acidic, substantially
free from chelating agents, and substantially free from agents
producing free ammonium ions in solution.
2. The electroplating composition of claim 1, wherein the
composition comprises a zinc ion source selected from the group
consisting of zinc chloride, zinc sulfate, zinc acetate, zinc
carbonate, zinc sulfamate, and combinations thereof.
3. The electroplating composition of claim 1, wherein the
electrolyte composition comprises zinc ions in an amount of about
15 g/L to about 120 g/L.
4. The electroplating composition of claim 1, wherein the
composition comprises a nickel ion source selected from the group
consisting of nickel chloride, nickel sulfate, nickel acetate,
nickel carbonate, nickel sulfamate, and combinations thereof.
5. The electroplating composition of claim 1, wherein the
electrolyte composition comprises nickel ions in an amount of about
10 g/L to about 100 g/L.
6. The electroplating composition of claim 1, wherein the
composition comprises a pH buffering agent selected from the group
consisting of carboxylic acids, salts of carboxylic acids, borates,
phosphoric acid, salts of phosphoric acid, and combinations
thereof.
7. The electroplating composition of claim 6, wherein the
composition comprises a pH buffering agent selected from the group
consisting of boric acid, sodium acetate, phosphoric acid, sodium
dihydrogen phosphate, potassium dihydrogen phosphate, and
combinations thereof.
8. The electroplating composition of claim 1, wherein the pH
buffering agent provides buffering at a pH range of about 2 to
about 7.
9. The electroplating composition of claim 1, wherein the pH
buffering agent is present at a concentration of about 20 g/L to
about 60 g/L.
10. The electroplating composition of claim 1, wherein the at least
one additional inorganic salt is selected from the group consisting
of chloride salts, sulfate salts, and combinations thereof.
11. The electroplating composition of claim 1, wherein the at least
one additional inorganic salt is selected from the group consisting
of sodium chloride, potassium chloride, sodium sulfate, potassium
sulfate, sodium acetate, methansulfonic acid, sulfamic acid, and
combinations thereof.
12. The electroplating composition of claim 1, wherein the at least
one additional inorganic salt is present at a concentration of
about 50 g/L to about 500 g/L.
13. The electroplating composition of claim 1, wherein the
electrolyte component comprises zinc chloride, nickel chloride
hexahydrate, boric acid, sodium acetate, and potassium
chloride.
14. The electroplating composition of claim 1, wherein the
composition comprises one or more Class I nickel brightener
selected from the group consisting of alkyl naphthalenes, benzene
sulfonic acids, benzene disulfonic acids, benzene trisulfonic
acids, naphthalene disulfonic acids, naphthalene trisulfonic acids,
benzene sulfonamides, naphthalene sulfonamides, benzene
sulfonamides, naphthalene sulfonimides, vinyl sulfonamides, allyl
sulfonamides, salts thereof, and combinations thereof.
15. The electroplating composition of claim 1, wherein the
composition comprises one or more Class I nickel brightener
selected from the group consisting of saccharin, saccharin salts,
bis-benzenesulfonylimide, carboxyethyl isothiuronium betaine,
2-thiohydantoin, trisodium 1,3,6-naphthalene trisulfonic acid,
trisodium 1,3,7-naphthalene trisulfonic acid, benzene sulfinic
acid, sodium styrene sulfonate, p-toluene sulfinic acid, p-toluene
sulfonic acid, ditolylsulfimide, sodium salt of di-o-tolyl
disulfimide, sodium salt of dibenzene disulfimide,
pyridine-3-sulfonic acid, p-vinylbenzene sulfonic acid, sodium
allyl sulfonate, sodium vinyl sulfonate, sodium propargyl
sulfonate, sodium benzene monosulfonate, dibenzene sulfonamide,
sodium benzene monosulfinate, sodium-3-chloro-2-butene-1-sulfonate,
sodium .beta.-styrene sulfonate, monoallyl sulfamide, diallyl
sulfamide, sodium propyne sulfonate, sodium allyl sulfonate, allyl
sulfonamide, and combinations thereof.
16. The electroplating composition of claim 1, wherein the Class I
nickel brightener is present at a concentration of about 0.1 g/L to
about 5 g/L.
17. The electroplating composition of claim 1, wherein the
composition comprises one or more Class II nickel brightener
selected from the group consisting of derivatives of acetylenic
alcohols, derivatives of acetylenic amines, derivatives of
ethylenic alcohols, derivatives of ethylenic amines, reaction
products of epoxides with acetylenic or ethylenic alcohols or
amines, N-heterocyclics, ethoxylated acetylenic alcohols,
propoxylated acetylenic alcohols, coumarins, compounds containing a
C.ident.N group, and combinations thereof.
18. The electroplating composition of claim 1, wherein the
composition comprises one or more Class II nickel brightener
selected from the group consisting of dipropoxylated
2-butyne-1,4-diol, 1,4-di-(.beta.-hydroxyethoxy)-2-butyne,
1,4-di-(.beta.-hydroxy-.gamma.-chloropropoxy)-2-butyne,
1,4-di-(.beta.-.gamma.-epoxypropoxy)-2-butyne,
1,4-di-(2'-hydroxy-4'-oxa-6'-heptenoxy)-2-butyne,
N-1,2-dichloropropenyl pyridinium chloride, 2,4,6-trimethyl
N-propargyl pyridinium bromide, N-allyl quinaldinium bromide,
N-allyl quinolinium bromide, 2-butyne-1,4-diol, propargyl alcohol,
N,N-diethyl-2-propyne-amine, dimethyldiallylammonium chloride,
pyridinium-propyl-sulfobetaine, 2-methyl-3-butyn-2-ol,
thiodiproprionitrile, hydroxyethyl propynyl ether,
.beta.-hydroxypropyl propynyl ether, bis-(.beta.-hydroxypropyl
ether)-2-butyn-1,4-diol, .gamma.-propynoxy propyl sulfonic acid,
.gamma.-propynoxy-.beta.-hydroxypropyl sulfonic acid,
1-(.gamma.-sulfopropoxy)-2-butyn-4-ol,
1,4-di-(.beta.-hydroxy-.gamma.-sulfonic propoxy)-2-butyne,
derivatives thereof, and combinations thereof.
19. The electroplating composition of claim 1, wherein the Class II
nickel brightener is present at a concentration of about 0.05 g/L
to about 3 g/L.
20. The electroplating composition of claim 1, wherein the
composition comprises one or more aromatic carboxylic acid selected
from the group consisting of benzoic acid, sodium benzoate,
salicylic acid, sodium salicylate, niacin, niacinamide, cinnamic
acid, phenyl propiolic acid, benzoyl acetic acid, o-coumaric acid,
benzoyl acetic acid ethyl ester, and combinations thereof.
21. The electroplating composition of claim 1, wherein the aromatic
carboxylic acid is present at a concentration of about 0.01 g/L to
about 3 g/L.
22. The electroplating composition of claim 1, wherein the
composition comprises one ore more aldehyde or ketone compound
useful as a top brightener in a zinc electroplating system.
23. The electroplating composition of claim 1, wherein the
composition comprises one or more aldehyde or ketone compound
selected from the group consisting of aryl aldehydes, aryl ketones,
ring-halogenated aryl aldehydes, ring-halogenated aryl ketones,
heterocyclic aldehydes, heterocyclic ketones, aryl olefinic
aldehydes, aryl olefinic ketones, aryl olefinic lactone,
carbocyclic olefinic aldehydes, carbocyclic olefinic ketones, and
combinations thereof.
24. The electroplating composition of claim 1, wherein the
composition comprises one or more aldehyde or ketone compound
selected from the group consisting of o-anisic aldehyde, p-anisic
aldehyde, o-chlorobenzaldehyde, p-chlorobenzaldehyde, cinnaldehyde,
piperonal, benzylidene acetone, 2,4-dichlorobenzaldehyde,
2,6-dichlorobenzaldehyde, 2-hydroxy-1-naphthaldehyde, furfuryl
acetone, thiophene aldehyde, benzal acetone, .beta.-ionone, and
combinations thereof.
25. The electroplating composition of claim 1, wherein the aldehyde
or ketone compound is present at a concentration of about 1 mg/L to
about 100 mg/L.
26. The electroplating composition of claim 1, wherein the
composition comprises two or more aldehyde or ketone compounds.
27. The electroplating composition of claim 1, wherein the
composition comprises one or more non-ionic surfactant selected
from the group consisting of homopolymers of ethylene oxide,
homopolymers of propylene oxide, propylene oxide-ethylene oxide
block copolymers, ethylene oxide condensation products of naphthol
and long chain fatty alcohols, ethylene oxide condensation products
of naphthol and long chain fatty amines, ethylene oxide
condensation products of naphthol and long chain fatty acids,
ethylene oxide condensation products of naphthol and long chain
alkyl phenol, alkoxylated alkyl phenols, alkyl naphthols, aliphatic
monohydric alcohols, aliphatic polyhydric alcohols, oxo alcohol
ethoxylates, alkylphenol ethoxylates, fatty alcohol ethoxylates,
.beta.-naphthol ethoxylates, and combinations thereof.
28. The electroplating composition of claim 1, wherein the
composition comprises one or more anionic surfactant selected from
the group consisting sodium dialkylsulfosuccinates, sulfonated or
sulfated alkylalkoxylates, alkylphenol sulfonates or sulfates,
naphthalenesulfonic acids, and combinations thereof.
29. The electroplating composition of claim 1, wherein the
non-ionic or anionic surfactant is present at a concentration of
about 0.05 g/L to about 10 g/L.
30. The electroplating composition of claim 1, wherein the
composition comprises a non-ionic surfactant and an anionic
surfactant.
31. The electroplating composition of claim 1, further comprising
one or more hydrotrope compounds.
32. The electroplating composition of claim 1, wherein the one or
more hydrotrope compounds comprises sodium cumene sulfate.
33. The electroplating composition of claim 1, wherein the
composition is prepared batchwise combining the components of the
electrolyte composition and the components of the organic
composition at the time of use.
34. The electroplating composition of claim 1, wherein the
electrolyte composition and the organic composition are prepared as
separate compositions and predetermined volumes of the electrolyte
composition and the organic composition are combined at the time of
use to form the electroplating composition.
35. The electroplating composition of claim 1, wherein the
electrolyte composition is prepared prior to a time of use and the
components of the organic composition are added to the electrolyte
composition at the time of use to prepare said electroplating
composition.
36. The electroplating composition of claim 1, wherein the
electroplating composition is completely free from chelating
agents.
37. The electroplating composition of claim 1, wherein the
electroplating composition is completely free from agents producing
free ammonium ions in solution.
38. A method for depositing a zinc-nickel alloy on a substrate, the
method comprising immersing the substrate in an aqueous
electroplating composition comprising an electrolyte composition
and an organic composition, wherein the electrolyte composition
comprises: a) a zinc ion source; b) a nickel ion source; c) a pH
buffering agent; and d) at least one additional salt; the organic
composition comprises: a) a Class I nickel brightener; b) a Class
II nickel brightener; c) an aromatic carboxylic acid; d) an
aldehyde or ketone compound; and e) a non-ionic or anionic
surfactant; and wherein the electroplating composition is acidic,
substantially free from chelating agents, and substantially free
from agents producing free ammonium ions in solution; and applying
an electrical current to the immersed substrate for a time
sufficient to deposit a layer of a zinc-nickel alloy on the
substrate.
39. The method of claim 38, wherein the zinc-nickel alloy layer
deposited on the substrate comprises an average nickel
concentration in a range of about 5% to about 15%, based on the
overall weight of the deposition layer, when the zinc-nickel alloy
layer is deposited at a current density of about 2 ASF to about 50
ASF.
40. The method of claim 38, wherein the zinc-nickel alloy layer
deposited on the substrate comprises an average nickel
concentration in a range of about 5% to about 15%, based on the
overall weight of the deposition layer, when the zinc-nickel alloy
layer is deposited at a current density of about 0.5 ASF to about
120 ASF.
41. The method of claim 38, wherein the zinc-nickel alloy layer is
deposited such that the average nickel concentration varies from a
highest concentration to a lowest concentration by less than about
3 percentage points when the zinc-nickel alloy layer is deposited
at a current density of about 2 ASF to about 50 ASF.
42. The method of claim 38, wherein said electroplating composition
during said method is within a temperature range of about
85.degree. F. to about 120.degree. F.
43. The method of claim 38, wherein the electrolyte composition
comprises zinc ions in an amount of about 15 g/L to about 120
g/L.
44. The method of claim 38, wherein the electrolyte composition
comprises nickel ions in an amount of about 10 g/L to about 100
g/L.
45. The method of claim 38, wherein the pH buffering agent provides
buffering at a pH range of about 2 to about 7.
46. The method of claim 38, wherein the pH buffering agent is
present at a concentration of about 20 g/L to about 60 g/L.
47. The method of claim 38, wherein the at least one additional
inorganic salt is present at a concentration of about 50 g/L to
about 500 g/L.
48. The method of claim 38, wherein the Class I nickel brightener
is present at a concentration of about 0.1 g/L to about 5 g/L.
49. The method of claim 38, wherein the Class II nickel brightener
is present at a concentration of about 0.05 g/L to about 3 g/L.
50. The method of claim 38, wherein the aromatic carboxylic acid is
present at a concentration of about 0.01 g/L to about 3 g/L.
51. The method of claim 38, wherein the aldehyde or ketone compound
is present at a concentration of about 1 mg/L to about 100
mg/L.
52. The method of claim 38, wherein the organic composition
includes two or more aldehyde or ketone compounds.
53. The method of claim 38, wherein the non-ionic or anionic
surfactant is present at a concentration of about 0.05 g/L to about
10 g/L.
54. The method of claim 38, wherein the organic composition
includes a non-ionic surfactant and an anionic surfactant.
55. The method of claim 38, wherein the organic composition further
comprises one or more hydrotrope compounds.
56. The method of claim 38, wherein said electroplating composition
is prepared batchwise combining the components of the electrolyte
composition and the components of the organic composition at the
time of carrying out said method.
57. The method of claim 38, wherein said electrolyte composition
and said organic composition are prepared as separate compositions
and specified volumes of the electrolyte composition and the
organic composition are combined to form said electroplating
composition at the time of carrying out said method.
58. The method of claim 38, wherein said electrolyte composition is
prepared prior to carrying out said method and the components of
the organic composition are added to said electrolyte composition
at the time of carrying out said method to prepare said
electroplating composition.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/692,204, filed Jun. 20, 2005, which is
incorporated herein in its entirety.
FIELD OF THE INVENTION
[0002] The present invention is directed to electroplating
compositions, and more particularly to compositions useful for
electroplating zinc-nickel alloys. The invention is specifically
directed to an electroplating composition comprising an electrolyte
composition and an organic composition, wherein the electroplating
composition is particularly beneficial for depositing zinc-nickel
alloys with a consistent nickel concentration across a broad range
of current densities.
BACKGROUND
[0003] Electrodeposition of zinc and nickel metal onto a substrate,
particularly a metal substrate, and very particularly a ferrous
substrate, is a common practice for imparting protective and
decorative properties to the substrate. For example, ferrous
articles are often zinc or nickel electroplated to provide
corrosion resistance to the substrate. As the need for improved
corrosion protection has increased over time, interest in
zinc-nickel alloys has also increased, particularly as
electroplated zinc-nickel alloy coatings have been shown to provide
increased corrosion protection in comparison to electroplated
coatings composed of zinc alone.
[0004] Electroplating baths used in zinc-nickel alloy
electroplating generally can be divided into two separate
categories: alkaline electrolyte baths and acidic electrolyte
baths. Both types of baths, heretofore, have been known to suffer
from multiple disadvantages.
[0005] When using an alkaline zinc-nickel alloy electroplating
bath, a common problem encountered is maintaining a functional
level of metal ions in the bath. To overcome this problem, alkaline
zinc-nickel alloy electroplating baths generally require the use of
strong chelating agents to solubilize the metal ions and keep them
in solution. A chelator is generally recognized in the art as a
compound, often an organic compound, capable of forming two or more
coordination bonds with a central metal ion. Chelators can be
capable of coordinating metals in general, or may be more specific
for metal of certain valences (e.g., divalent cation chelators).
Examples of common chelating agents include: hydroxycarboxylic acid
salts, such as citrates, tartrates, gluconates, and glycollates;
amino alcohols, such as monoethanolamine, diethanolamine, and
triethanolamine; polyamines, such as ethylenediamine; amino
carboxylic acid salts, such as ethylenediamine tetraacetates and
nitrilotriacetates; polyhydroxyalcohols, such as sorbitol; and
thioureas.
[0006] The use of chelators presents a disadvantage in that plating
efficiency and plating rate can both be reduced as a result of the
metal ion complexation caused by the chelator. Furthermore, the
presence of the metal ion complexes with the chelators makes the
plating process environmentally unfavorable as the removal of the
complexed metal ions from wastewater streams is difficult and
costly. Accordingly, avoidance of chelators in general is
preferred.
[0007] Acidic zinc-nickel alloy electroplating baths also present
wastewater treatment problems. The high concentration of ammonium
ions commonly found in acidic zinc-nickel alloy electroplating
compositions tends to make metal ion removal more difficult, and
accordingly more costly. Further, environmental discharge limits
may be applicable to solutions including ammonium ions.
[0008] Apart from the waste treatment issues, the inherent physical
properties of coatings applied by acidic zinc-nickel alloy
electroplating have also been shown to be troublesome for various
reasons. The zinc-nickel alloy deposits can lack ductility, can be
brittle, and can be highly stressed. Each of these can cause the
electroplated zinc-nickel alloy layer to flake and peel from the
substrate, especially in regions of high current density.
[0009] Another limitation seen with previous zinc-nickel alloy
electroplating systems is a lack of alloy composition uniformity in
deposition layers applied with such systems. The concentration of
nickel in the zinc-nickel alloy tends to increase, often
significantly, as the current density of the plated article is
decreased. This can lead to disadvantages related to coating
performance, as well as coating aesthetics.
[0010] The disadvantages described above can be overcome according
certain embodiments of the present invention, which provides an
aqueous acidic zinc-nickel alloy electroplating composition, as
well as a method of preparing zinc-nickel alloy coatings.
SUMMARY OF THE INVENTION
[0011] The present invention provides an aqueous zinc-nickel alloy
electroplating composition. The composition is particularly useful
for depositing a layer of a zinc-nickel alloy on a substrate,
wherein the zinc-nickel alloy layer has an average nickel
concentration that is within a desired range when the zinc-nickel
layer is applied using a broad range of current densities. In
addition to a consistent average nickel concentration, the
zinc-nickel alloy layer deposited according to certain embodiments
of the invention is bright, lustrous, and ductile. Further, these
properties, as well as other properties generally desirable in an
electroplated coating, are achieved when the deposition is carried
out using a broad range of current densities.
[0012] In one aspect, the invention is directed to an acidic,
aqueous zinc-nickel alloy electroplating composition comprising an
electrolyte composition and an organic composition. In one
particular embodiment of the invention, the electrolyte composition
comprises a zinc ion source, a nickel ion source, a pH buffering
agent, and at least one additional inorganic salt. The organic
composition, according to this embodiment of the invention,
comprises a nickel brightener (preferentially a Class I nickel
brightener and a Class II nickel brightener), an aromatic
carboxylic acid, an aldehyde or ketone compound (preferably an
aromatic aldehyde or ketone compound), and a surfactant
(preferentially selected from non-ionic surfactants and anionic
surfactants). In one preferred embodiment, the zinc-nickel alloy
electroplating composition is free from chelating agents and is
further free from agents producing free ammonium ions in
solution.
[0013] In one particular embodiment, the electrolyte composition
portion of the electroplating composition comprises zinc chloride,
nickel chloride hexahydrate, potassium chloride, boric acid, and
sodium acetate. The electroplating composition is particularly
useful in that the electrolyte composition can be standardized to
specific requirements, and the organic composition can be varied to
provide desired properties.
[0014] According to another aspect, the invention provides a method
for depositing a zinc-nickel alloy on a substrate. In one
embodiment, the method comprises immersing the substrate in an
aqueous electroplating composition and applying an electrical
current to the immersed substrate for a time sufficient to deposit
a layer of a zinc-nickel alloy on the substrate. In one preferred
embodiment, the aqueous electroplating composition comprises an
electrolyte composition comprising a zinc ion source, a nickel ion
source, a pH buffering agent, and at least one additional inorganic
salt, and the organic composition comprises a Class I nickel
brightener, a Class II nickel brightener, an aromatic carboxylic
acid, an aldehyde or ketone compound, and a non-ionic or anionic
surfactant.
[0015] The method of the invention is particularly beneficial in
that it provides the ability to deposit a zinc-nickel alloy layer
with an average nickel concentration that is consistent when the
zinc-nickel layer is deposited using current densities varying over
a broad range. In one specific embodiment, the average nickel
concentration of the zinc-nickel alloy layer is in the range of
about 6% to about 15%, based on the overall weight of the
zinc-nickel layer. Preferentially, the average nickel concentration
is within this range when the deposition layer is applied using a
current density that is between about 0.5 Amperes/ft.sup.2 (ASF)
and about 120 ASF.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present inventions now will be described more fully
hereinafter with reference to specific embodiments of the
invention. Indeed, the invention may be embodied in many different
forms and should not be construed as limited to the embodiments set
forth herein; rather, these embodiments are provided so that this
disclosure will satisfy applicable legal requirements. As used in
the specification, and in the appended claims, the singular forms
"a", "an", "the", include plural referents unless the context
clearly dictates otherwise.
[0017] The present invention provides an electroplating composition
useful in an electroplating method for depositing a zinc-nickel
alloy layer on a substrate. The electroplating composition of the
present invention is particularly useful in that it is highly
versatile. For example, the electroplating composition can be
varied to provide preferred physical and chemical characteristics,
including corrosion protection for the underlying substrate and
pleasing aesthetics. The electroplating composition is further
versatile in that excellent deposition layers with favorable
properties can be achieved with a single composition while using a
broad range of electroplating current densities during deposition
of the layer. In particular, it is possible to deposit a
zinc-nickel alloy layer having a preferred average nickel
concentration, even when the layer is deposited using a broad range
of current densities. It is further possible, according to certain
embodiments of the invention, to deposit a zinc-nickel alloy layer
that is bright, lustrous, and exhibits high ductility.
[0018] Various embodiments of the invention are described in terms
of being "substantially free" of certain compounds, elements, ions,
or other like components. Accordingly, as used in describing the
invention, "substantially free" is intended to mean that the
compound, element, ion, or other like component is present, at
most, in only trace amounts (i.e., a concentration so minute that
the presence of the compound, element, ion, or other like component
will have no adverse affect on the desired properties of the
coating). Preferably, "substantially free" indicates the specified
compound, element, ion, or other like component is completely
absent or is not present in any amount measurable by techniques
generally used in the art.
[0019] The electroplating composition of the invention is
particularly distinguished from other acidic, aqueous systems in
that the composition is substantially free from chelators and is
likewise substantially free from agents producing free ammonium
ions in aqueous solution. As noted above, previously known
electroplating systems in the industry are plagued by the use of
chelators, which keep complexed metal ions in solution. Many such
systems further include ammonia or ammonium ion producing
compounds, which are also undesirable. The presence of such agents
leads to serious and costly treatment requirements. According to
the unique composition described herein, it is possible to provide
an effective electroplating composition that is substantially free
of chelators and ammonium ions, as well as the problems associated
therewith. The electroplating composition of the invention is
substantially free of chelators and agents capable of producing
free ammonium ions in aqueous solution. Accordingly, the
composition contains, at most, only trace amounts of chelators or
ammonium ions in such a minute concentration that the presence of
the chelators or ammonium ions will have no affect on the
electroplating and will have no adverse health or environmental
impact. Most preferably, the electroplating composition contains no
chelators or ammonium ions.
[0020] The electroplating composition of the invention comprises an
electrolyte composition and an organic composition. Accordingly, it
is possible to prepare a number of electroplating compositions
useful for depositing a zinc-nickel alloy layer with specifically
defined properties. Such can be accomplished by varying one or both
of the electrolyte composition and the organic composition. For
example, according to one embodiment of the invention, a basic (or
standard) electrolyte composition is prepared, and the overall
electroplating composition is varied by selectively changing only
the components of the organic composition.
[0021] The various components of the electrolyte composition and
the organic composition are described more completely below both in
terms of types, classes, and specific examples of the components of
the composition and also amounts and concentrations of the
components. Concentrations provided for the individual components
of the electrolyte composition and the organic composition are
provided on a basis of the overall volume of the electroplating
composition of the invention. Accordingly, while concentrations are
provided for each component individually, the concentrations ranges
provided should not be viewed as limited to the electrolyte
composition specifically or the organic composition specifically.
Rather, concentrations provided relate to the overall
electroplating composition, including the electrolyte composition
components and the organic composition components.
[0022] The concentrations provided herein refer to the
concentrations of the overall composition at the time of use. As
further described herein, the electrolyte composition or the
organic composition may be provided in a form wherein the
concentration of one or more components is outside the ranges
provided herein for the individual components of the electroplating
composition. The ability to provide the various components of the
inventive composition in concentrations different than disclosed
herein should not be viewed, however, as differentiating from the
claimed invention. Rather, the concentrations provided herein
describe the concentrations of the various components at the time
of use of the electroplating composition, and any composition
prepared or provided such that the concentrations of the various
components would be within the ranges provided herein at the time
of use of the electroplating composition would be encompassed by
the present invention.
[0023] The electrolyte composition comprises a zinc ion source and
a nickel ion source. As used herein, the term zinc ion source means
any material capable of providing free zinc cations when in an
aqueous solution. Similarly, the term nickel ion source means any
material capable of providing free nickel cations when in solution.
The zinc ion source and the nickel ion source preferably include
salts of the metals; however, the zinc ion source and the nickel
ion source are not limited to such salts. Rather, the sources can
be any material providing at least some free zinc ions and nickel
ions, such as elemental zinc and elemental nickel. The zinc and
nickel sources can further include other metal alloys, zinc- or
nickel-containing compounds, and the like.
[0024] In one preferred embodiment, the zinc ions and the nickel
ions are supplied in the form of soluble zinc and nickel salts.
Particularly, the zinc ion source and the nickel ion source can be
inorganic salts of the metals. Such inorganic salts include, for
example, halides, and also include carbon, nitrogen, or sulfur
containing salts, such as carbonates, nitrates, and sulfates, as
well as hydrates thereof. In one particular embodiment, the zinc
ion source is selected from the group consisting of zinc chloride,
zinc sulfate, zinc acetate, zinc carbonate, and zinc sulfamate. In
another particular embodiment, the nickel ion source is selected
from the group consisting of nickel chloride, nickel sulfate,
nickel acetate, nickel carbonate, and nickel sulfamate. In one
particularly preferred embodiment, the zinc ion source and the
nickel ion source are selected from the chloride and sulfate salts
of zinc and nickel.
[0025] The zinc ion source and the nickel ion source should each be
present in an amount useful for achieving and maintaining a
functional concentration of zinc ions and nickel ions (i.e., a
concentration sufficient for deposition of a zinc-nickel alloy
layer on a substrate during electroplating). Preferably, the
electrolyte composition includes zinc ions in an amount of about 15
g/L to about 120 g/L, based upon the overall volume of the
electroplating composition of the invention. In further
embodiments, the zinc ions are present in an amount of about 25 g/L
to about 100 g/L, about 30 g/L to about 80 g/L, or about 40 g/L to
about 60 g/L.
[0026] To achieve and maintain a functional concentration of nickel
ions in the electrolyte composition, it is preferable that the
nickel ions be present in an amount of about 10 g/L to about 100
g/L, based on the overall volume of the electroplating composition.
In further embodiments, the nickel ion source is present in an
amount of about 15 g/L to about 80 g/L, about 20 g/L to about 60
g/L, or about 30 g/L to about 40 g/L.
[0027] The electrolyte composition according to the invention
further comprises a pH buffering agent. Any pH buffering agent
commonly recognized as useful in electroplating compositions,
particularly zinc and nickel electroplating compositions, can be
used according to the invention. For example, carboxylic acids and
borates are particularly useful. The pH buffering agent used in the
invention is limited only in that it should not be capable of also
acting as a complexing agent (i.e., a chelator), and it should not
be capable of providing free ammonium ions in aqueous solution. In
one preferred embodiment, the pH buffering agent includes boric
acid. In another preferred embodiment, the pH buffering agent
includes sodium acetate. Further, non-limiting examples of
non-complexing buffers useful according to the present invention
include phosphoric acid, sodium or potassium dihydrogen phosphate,
benzoates, and hydroxybenzoates.
[0028] In one embodiment of the invention, multiple buffer agents
are provided. Including multiple buffer agents can be particularly
useful, particularly in a complex system, for maintaining a
specified pH. Preferentially, the electrolyte composition of the
invention has a pH indicating a composition that is at least
slightly acidic. The electrolyte composition preferably has a pH
that is less than about 7. In certain embodiments, the electrolyte
composition has a pH of about 2 to about 7, about 4 to about 6.5,
or about 5 to about 6.
[0029] In order to maintain a desired pH, it is preferable that the
buffering agent used in the electrolyte composition is particularly
suited to resisting shifts in pH outside the preferred ranges
described above. Accordingly, it is preferable that the buffering
agent used in the electrolyte composition has a pKa value of about
4 to about 6.5. In further embodiments, the buffering agent has a
pKa of about 4.5 to about 6 or a pKa of about 5 to about 6.
[0030] The amount of buffering agent included in the electrolyte
composition can vary depending upon the desired pH of the
composition, the known pKa value of the buffering agent, and other
electroplating process parameters as would be recognized by one of
skill in the art. In one particular embodiment of the invention,
boric acid and sodium acetate are included in the electrolyte
composition as pH buffering agents. According to one embodiment,
boric acid is provided in a concentration of about 20 g/L to about
50 g/L, about 25 g/L to about 45 g/L, or about 30 g/L to about 40
g/L, based on the overall volume of the electroplating composition.
Further according to one embodiment, sodium acetate is provided in
a concentration of about 20 g/L to about 60 g/L, about 25 g/L to
about 55 g/L, or about 30 g/L to about 50 g/L.
[0031] According to another particular embodiment of the invention,
the electrolyte composition further comprises at least one
additional inorganic salt. As noted above, the zinc ion source and
the nickel ion source can include inorganic salts. Preferably, at
least one additional inorganic salt is included in addition to any
inorganic salts included as a zinc ion source or a nickel ion
source. Such language referring to at least one additional
inorganic salt is meant only to distinguish the additional
inorganic salt from the zinc salt or nickel salt possibly used as
the zinc or nickel ion source, and is not intended to limit the
zinc and nickel ion sources to inorganic salts.
[0032] The additional inorganic salts are particularly included in
the electrolyte composition for the function of increasing the
conductivity of the overall electroplating composition. Any
inorganic salt commonly recognized as useful for increasing
conductivity in an electroplating solution can be used according to
the invention. Preferentially, the additional inorganic salts are
compatible with other salt components of the electrolyte
composition. For example, in one embodiment of the invention, the
zinc ion source is zinc chloride and the nickel ion source is
nickel chloride hexahydrate. In this embodiment of the invention,
it is useful for the additional inorganic salt provided for
increasing conductivity of the composition to include a chloride
salt, such as sodium chloride or potassium chloride. Further
inorganic salts particularly useful include sodium sulfate,
potassium sulfate, sodium acetate, methansulfonic acid, and
sulfamic acid.
[0033] The amount of additional inorganic salts added to the
electrolyte composition to increase the conductivity of the
composition can vary depending upon the zinc ion source and the
nickel ion source used in the composition and can also be affected
by further electroplating process parameters. In one embodiment,
the additional inorganic salt is provided at a concentration of
about 50 g/L to about 500 g/L, based on the overall volume of the
electroplating composition. In further embodiments, the additional
inorganic salt is provided at a concentration of about 75 g/L to
about 450 g/L, about 100 g/L to about 400 g/L, about 125 g/L to
about 375 g/L, or about 150 g/L to about 350 g/L.
[0034] The electroplating composition of the invention also
comprises an organic composition. The inventive composition is
particularly useful in that it can be widely varied to provide
specific beneficial properties to the coating deposited on the
substrate using the composition. Particularly, a single electrolyte
composition can be prepared, for example as a stock solution, and
the organic composition added to the electrolyte composition can
have a variable makeup.
[0035] Multiple different types of organic compounds can be used in
the organic composition. For example, the organic composition can
include compounds commonly used in zinc electroplating systems,
such as aromatic carboxylic acids, anionic surfactants, non-ionic
surfactants, hydrotropes, and carbonyl compounds, such as ketones
and aldehydes. The organic composition can also include compounds
commonly used in nickel electroplating systems, particularly
compounds generally known as brighteners.
[0036] Generally, the organic composition of the invention can
include compounds commonly classified in the field of
electroplating according to a specific function provided by the
compounds. For example, the organic composition can include
compounds classified as Class I nickel brighteners, Class II nickel
brighteners, top brighteners, auxiliary brighteners, carriers,
ductilizers, leveling agents, grain refiners, anti-corrosives,
hardeners, and other classes of additives recognizable as useful to
one of skill in the art. Such additives are described and
exemplified in various texts. See, for example, F. A. Lowenheim,
Modern Electroplating (1974), 3.sup.rd ed., New York: John Wiley
& Sons, Inc., and J. K. Dennis & T. E. Such, Nickel and
Chromium Plating (1972), London: Butterworths & Co., both of
which are incorporated herein by reference.
[0037] According to one particular embodiment of the invention, the
organic composition comprises a Class I nickel brightener, a Class
II nickel brightener, an aromatic carboxylic acid, an aldehyde or
ketone compound, and a surfactant selected from non-ionic and
anionic surfactants.
[0038] Class I nickel brighteners are typically understood to be
aromatic or unsaturated organic compounds that include sulfur, such
as sulfinic acids, sulfonic acids, sulfonamides, sulfonimides,
sulfimides, and salts thereof. Any compounds generally understood
to be Class I nickel brighteners can be used in the organic
composition of the invention. In particular, such brighteners can
include alkyl naphthalenes, benzene sulfonic acids, benzene
disulfonic acids, benzene trisulfonic acids, naphthalene disulfonic
acids, naphthalene trisulfonic acids, benzene sulfonamides,
naphthalene sulfonamides, benzene sulfonimides, naphthalene
sulfonimides, vinyl sulfonamides, allyl sulfonamides, salts
thereof, and combinations thereof.
[0039] Class I nickel brighteners, as used according to the
invention, can be incorporated into the organic composition singly
or in suitable combinations. Generally, compounds identified as
Class I nickel brighteners are useful for providing the following
functions: [0040] provide semi-lustrous deposits or produce grain
refinement; [0041] act as ductilizing agents, particularly when
used in combination with other types of organic compounds, such as
Class II brighteners; [0042] control internal stress of deposits,
generally by making the stress desirably compressive; [0043]
introduce controlled sulfur content into the electroplated layer to
desirably affect chemical reactivity, thereby providing increased
anti-corrosive action; and [0044] minimize pitting.
[0045] Specific, non-limiting examples of Class I nickel
brighteners useful in the organic composition of the invention
include: saccharin (and salts thereof, such as sodium saccharin);
bis-benzenesulfonylimide; carboxyethyl isothiuronium betaine;
2-thiohydantoin; trisodium 1,3,6-naphthalene trisulfonic acid;
trisodium 1,3,7-naphthalene trisulfonic acid; benzene sulfinic
acid; sodium styrene sulfonate; p-toluene sulfinic acid; p-toluene
sulfonic acid; ditolylsulfimide; sodium salt of di-o-tolyl
disulfimide; sodium salt of dibenzene disulfimide;
pyridine-3-sulfonic acid; p-vinylbenzene sulfonic acid; sodium
allyl sulfonate; sodium vinyl sulfonate; sodium propargyl
sulfonate; sodium benzene monosulfonate; dibenzene sulfonimide;
sodium benzene monosulfinate; sodium-3-chloro-2-butene-1-sulfonate;
sodium .beta.-styrene sulfonate; monoallyl sulfamide; diallyl
sulfamide; sodium propyne sulfonate; sodium allyl sulfonate; and
allyl sulfonamide.
[0046] The concentration of the Class I nickel brightener included
in the electroplating composition can vary depending upon the
particular compound used, as well as the specific desired
properties to be provided the zinc-nickel alloy for deposition.
According to one embodiment of the invention, the Class I nickel
brightener is present at a concentration of about 0.1 g/L to about
5 g/L. In further embodiments, the Class I nickel brightener is
present at a concentration of about 0.2 g/L to about 4 g/L, about
0.3 g/L to about 3.5 g/L, or about 0.4 g/L to about 3 g/L.
[0047] Class II nickel brighteners are generally understood to be
unsaturated, organic materials which produce leveling and increase
the luster of an electroplated deposit when used in conjunction
with a Class I nickel brightener. Typically, Class II nickel
brighteners can be used singly or in combination and include
derivatives of acetylenic or ethylenic alcohols or amines (and
reaction products thereof with epoxides), N-heterocyclics (such as
pyridine-based compounds), ethoxylated and propoxylated acetylenic
alcohols, coumarins, and compounds containing a carbonitrile
(C.ident.N) group.
[0048] Specific, non-limiting examples of Class II nickel
brighteners useful in the organic composition of the invention
include: dipropoxylated 2-butyne-1,4-diol;
1,4-di-(.beta.-hydroxyethoxy)-2-butyne;
1,4-di-(.beta.-hydroxy-.gamma.-chloropropoxy)-2-butyne;
1,4-di-(.beta.-.gamma.-epoxypropoxy)-2-butyne;
1,4-di-(2'-hydroxy-4'-oxa-6'-heptenoxy)-2-butyne;
N-1,2-dichloropropenyl pyridinium chloride; 2,4,6-trimethyl
N-propargyl pyridinium bromide; N-allyl quinaldinium bromide;
N-allyl quinolinium bromide; 2-butyne-1,4-diol; propargyl alcohol;
N,N-diethyl-2-propyne-amine; dimethyldiallylammonium chloride;
pyridinium-propyl-sulfobetaine; 2-methyl-3-butyn-2-ol;
thiodiproprionitrile; hydroxyethyl propynyl ether;
.beta.-hydroxypropyl propynyl ether; bis-(.beta.-hydroxypropyl
ether)-2-butyn-1,4-diol; .gamma.-propynoxy propyl sulfonic acid;
.gamma.-propynoxy-.beta.-hydroxypropyl sulfonic acid;
1-(.gamma.-sulfopropoxy)-2-butyn-4-ol; and
1,4-di-(.beta.-hydroxy-.gamma.-sulfonic propoxy)-2-butyne.
Particularly useful Class II nickel brighteners in the organic
composition of the invention include propargyl alcohol,
2-butyne-1,4-diol, N,N-diethyl-2-propyne-amine,
dimethyldiallylammonium chloride, pyridinium-propyl-sulfobetaine,
and derivatives thereof.
[0049] The concentration of the Class II nickel brightener included
in the electroplating composition can vary depending upon the
particular compound used, as well as the specific desired
properties to be provided the zinc-nickel alloy for deposition.
According to one embodiment of the invention, the Class II nickel
brightener is present at a concentration of about 0.05 g/L to about
3 g/L. In further embodiments, the Class II nickel brightener may
be present at a concentration of about 0.1 g/L to about 2.5 g/L,
about 0.15 g/L to about 2 g/L, or about 0.2 g/L to about 1.8 g/L,
based on the overall volume of the electroplating composition.
[0050] Aromatic carboxylic acids are commonly used in zinc
electroplating baths as basic brighteners. Accordingly, any
aromatic carboxylic acid (or combination thereof) generally
recognized by one of skill in the art as useful in a zinc
electroplating bath can be used in the aromatic composition of the
present invention. As used herein, the term aromatic carboxylic
acid is also intended to refer to salts and derivatives of aromatic
carboxylic acids. Non-limiting examples of aromatic carboxylic
acids useful in the organic composition of the invention include
benzoic acid, sodium benzoate, salicylic acid, sodium salicylate,
niacin, niacinamide, cinnamic acid, phenyl propiolic acid, benzoyl
acetic acid, o-coumaric acid, and benzoyl acetic acid ethyl ester.
Particularly preferred organic carboxylic acids useful in the
organic composition of the invention include sodium benzoate,
salicylic acid, niacin, and niacinamide.
[0051] The concentration of the aromatic carboxylic acid included
in the electroplating composition can vary depending upon the
particular compound used, as well as the specific desired
properties to be provided the zinc-nickel alloy for deposition.
According to one embodiment of the invention, the aromatic
carboxylic acid is present at a concentration of about 0.01 g/L to
about 3 g/L. According to further embodiments, the aromatic
carboxylic acid is present at a concentration of about 0.02 g/L to
about 2.5 g/L, about 0.05 g/L to about 2 g/L, or about 0.1 g/L to
about 1.5 g/L, based on the overall volume of the electroplating
composition.
[0052] The organic composition of the invention further includes a
carbonyl compound. As used herein, a carbonyl compound is intended
to refer to compounds wherein the primary functional group is a
carbonyl group. In particular, the carbonyl compounds of the
invention are aldehydes and ketones, with particular preference
being given to aromatic aldehyde compounds and aromatic ketone
compounds. Such aldehyde compounds and ketone compounds are
typically used as top brighteners in zinc electroplating systems to
improve the specular gloss of the zinc layer deposited on a
substrate.
[0053] The aldehyde or ketone compound of the organic composition
can comprise a single aldehyde component or a single ketone
component, or two or more of such compounds. Accordingly, the
organic composition can include an aldehyde compound and one or
more ketone compounds, or the composition can include a ketone
compound and one or more aldehyde compounds. Preferably, the
organic composition of the invention includes at least two
compounds selected from the group of aldehyde compounds and ketone
compounds.
[0054] The organic composition of the invention can include any
aromatic aldehyde or ketone typically recognized as useful as a
zinc brightener, such as aryl aldehydes, aryl ketones,
ring-halogenated aryl aldehydes and ketones, heterocyclic aldehydes
and ketones, aryl olefinic aldehydes and ketones, aryl olefinic
lactone, and carbocyclic olefinic aldehydes and ketones.
Non-limiting examples of aldehyde compounds and ketone compounds
useful in the organic composition of the invention include:
o-anisic aldehyde; p-anisic aldehyde; o-chlorobenzaldehyde;
p-chlorobenzaldehyde; cinnaldehyde; piperonal, benzylidene acetone;
2,4-dichlorobenzaldehyde; 2,6-dichlorobenzaldehyde;
2-hydroxy-1-naphthaldehyde; furfuryl acetone; thiophene aldehyde;
benzal acetone; and .beta.-ionone. In particular, the aldehyde and
ketone compounds useful in the organic composition include
benzylidene acetone, p-anisic aldehyde, o-chlorobenzaldehyde,
dichlorobenzaldehyde, cinnaldehyde, and piperonal.
[0055] The concentration of the aldehyde compound or ketone
compound included in the electroplating composition can vary
depending upon the particular compound used, as well as the
specific desired properties to be provided the zinc-nickel alloy
for deposition. According to one embodiment of the invention, the
total concentration of aldehyde compounds, ketone compound, or
combinations thereof, present in the composition is about 1 mg/L to
about 100 mg/L. In further embodiments, the total concentration is
about 2 mg/L to about 75 mg/L, about 2.5 mg/L to about 50 mg/L, or
about 3 mg/L to about 40 mg/L, based on the overall volume of the
electroplating composition.
[0056] The organic composition of the invention further comprises
one or more surfactant selected from the group of non-ionic
surfactants and anionic surfactants. Such surfactants are generally
useful as brighteners or grain refining agents in zinc
electroplating systems. The non-ionic or anionic surfactant used in
the organic composition can be present singly or as a combination
of surfactants. For example, the composition can include multiple
non-ionic surfactants, multiple anionic surfactants, or one or more
non-ionic surfactants in combination with one or more anionic
surfactants. In one preferred embodiment of the invention, the
organic composition includes at least one non-ionic surfactant and
at least one anionic surfactant. Examples of non-ionic and anionic
surfactants useful according to various embodiments of the
invention are described in Lange, Robert K., Surfactants: A
Practical Handbook, Hanser Gardner Publications (1999), which is
incorporated herein by reference in its entirety.
[0057] Types of non-ionic surfactants useful in the organic
composition of the invention include the following: homopolymers of
ethylene oxide (such as polyethylene glycols); homopolymers of
propylene oxide (such as polypropylene glycols); propylene
oxide-ethylene oxide block copolymers (such as ethylene
glycol-propylene glycol block copolymers); ethylene oxide
condensation products of naphthol and long chain fatty alcohols,
long chain fatty amines, long chain fatty acids, and long chain
alkyl phenol (wherein the long chain fatty group has 6-30 carbon
atoms); alkoxylated alkyl phenols; alkyl naphthols; aliphatic
monohydric alcohols; and aliphatic polyhydric alcohols; oxo alcohol
ethoxylates; alkylphenol ethoxylates; fatty alcohol ethoxylates;
and .beta.-naphthol ethoxylates.
[0058] Specific, non-limiting examples of non-ionic surfactants
useful in the organic composition of the invention include the
following: nonylphenol (such as the nonylphenol ethoxylate IGEPAL
CO-730.RTM. available from Stepan Company, and the sodium
nonylphenol ethoxylate sulfate WITCOLATE.TM. D51-53 available from
Akzo Nobel) and various polyethylene glycol (PEG) surfactants, such
as Carbowax 3350, which is a PEG polymer having an average
molecular weight of about 3,350. Additional non-limiting examples
of non-ionic surfactants useful in the invention include ethylene
oxide/propylene oxide copolymers with molecular weights between
about 2,000 and about 8,000, such as GENAPOL.RTM. PF20 and
GENAPOL.RTM. PF40 (available from Clariant Corporation).
[0059] Various types of anionic surfactants useful in the organic
composition of the invention include the following: sodium
di-alkylsulfosuccinates, sulfonated or sulfated alkylalkoxylates,
alkylphenol sulfonates or sulfates, and naphthalenesulfonic acids
or condensation products. Specific, non-limiting, examples of
anionic surfactants useful in the organic composition of the
invention include sodium diisobutyl sulfosuccinate and sodium
dihexyl sulfosuccinate (such as GEMTEX.RTM. 445 and GEMTEX.RTM.
680, available from Finetex, Inc.), and the sulfated polyalkoxy
naphthyl ether salt Nape 14-90, which is available from Raschig
Corporation.
[0060] The concentration of the surfactants included in the
electroplating composition can vary depending upon the particular
compound used, as well as the specific desired properties to be
imparted to the zinc-nickel alloy for deposition. According to one
embodiment of the invention, the surfactants selected from the
group of non-ionic and anionic surfactants are present at a total
concentration of about 0.05 g/L to about 10 g/L. In further
embodiments, the surfactants are present at a total concentration
of about 0.1 g/L to about 8 g/L, about 0.15 g/L to about 6 g/L, or
about 0.2 g/L to about 5 g/L, based on the overall volume of the
electroplating composition.
[0061] In certain embodiments, the organic composition of the
invention may further comprise one or more compounds recognized as
hydrotropes. A hydrotrope is generally understood to be a chemical
capable of increasing the aqueous solubility of various slightly
soluble organic chemicals. Hydrotropes are particularly useful for
increasing the solubility of surfactants, especially non-ionic
surfactants. Hydrotropes may be classified as non-surfactant
molecules, such as cumene sulfonates, xylene sulfonates, glycol
ether sulfates, and ureas, or as surfactant molecules, such as
C.sub.8-C.sub.10 fatty alcohol sulfates, 2-ethylhexylsulfate, and
2-ethylhexyl-iminodipropionate. While conventional hydrotropes act
mainly as solubilizers, surfactant-type hydrotropes are able to
form micelles and have good wetting power. Both non-surfactant and
surfactant-type hydrotropes may be used according to the invention.
In one specific embodiment, the organic composition includes sodium
cumene sulfate. Further salts of hydrotrope compounds may also be
used in the invention.
[0062] The concentration of the hydrotrope compounds included in
the electroplating composition can vary depending upon the
particular compound used, as well as the specific desired
properties to be imparted to the zinc-nickel alloy for deposition.
According to one embodiment of the invention, the one or more
hydrotrope compounds are present at a total concentration of about
0.1 g/L to about 1 g/L. In further embodiments, the surfactants are
present at a total concentration of about 0.1 g/L to about 0.8 g/L,
about 0.2 g/L to about 0.7 g/L, or about 0.3 g/L to about 0.5 g/L,
based on the overall volume of the electroplating composition.
[0063] As previously noted, the electroplating composition of the
invention is particularly beneficial in that it is easily
modifiable for particular uses. The electrolyte composition and the
organic composition, particularly the organic composition, can be
specifically modified to suit particular needs and plating
parameters for use in an electroplating method.
[0064] The electroplating composition can be prepared batchwise,
wherein all components of the electrolyte composition and all
components of the organic composition are added at once, thereby
forming the electroplating composition. Alternately, the
electrolyte composition and the organic composition can be prepared
separately and appropriates volumes of the two compositions
combined to form the electroplating composition. In one particular
embodiment, the electrolyte composition is prepared separately as a
stock solution or standard solution. As desired to form an
electroplating composition, an appropriate volume of the stock
electrolyte composition can be taken for use in preparing the
electroplating composition. Such preparation can encompass adding
an appropriate volume of a ready prepared organic composition or
separately adding the desired components of the organic composition
to the separate volume of the electrolyte composition.
[0065] In one embodiment, the electrolyte composition comprises
nickel chloride, zinc chloride, potassium chloride, hydroboric
acid, and sodium acetate. Such an embodiment is particularly useful
as a stock composition, as described herein, wherein defined
amounts of the stock composition can be combined with a
predetermined organic composition to prepare the electroplating
composition of the invention. Of course, it is understood that
other electrolyte compositions could be similarly prepared and
combined with components of the organic composition to prepare an
electroplating composition according to the invention.
[0066] Various different organic compositions could be prepared
according to the invention. In one embodiment, an organic
composition comprises sodium saccharin, bis-benzenesulfonylimide,
sodium benzoate, Nape 14-90, Carbowax 3350,
dimethyldiallyl-ammonium chloride, and benzylidene acetone. Such a
composition could particularly be combined with a predetermined
amount of an electrolyte composition according to the
invention.
[0067] In another embodiment, an organic composition according to
the invention comprises sodium saccharine, bis-benzenesufonylimide,
sodium benzoate, Nape 14-90, Carbowax 3350,
dimethyldiallyl-ammonium chloride, and benzylidene acetone. Such a
composition could likewise be combined with a predetermined amount
of an electrolyte composition according to the invention.
[0068] In still another embodiment, an organic composition
according to the invention comprises sodium saccharin,
bis-benzenesulfonylimide, sodium benzoate, Nape 14-90, Carbowax
3350, dimethyldiallyl-ammonium chloride, benzylidene acetone,
chlorobenzaldehyde, and sodium cumene sulfonate. Such a composition
could likewise be combined with a predetermined amount of an
electrolyte composition according to the invention.
[0069] In yet another embodiment, an organic composition according
to the invention comprises sodium saccharin,
bis-benzenesulfonylimide, sodium benzoate, Nape 14-90, Carbowax
3350, dimethyldiallyl-ammonium chloride, 2-thiohydantoin,
benzylidene acetone, o-chlorobenzaldehyde, and sodium cumene
sulfonate. Again, such a composition could be combined with a
predetermined amount of an electrolyte composition according to the
invention.
[0070] Moreover, in another embodiment, an organic composition
according to the invention comprises sodium saccharin,
bis-benzenesulfonylimide, sodium benzoate, Nape 14-90, Carbowax
3350, dimethyldiallyl-ammonium chloride, Carboxyethyl isothiuronium
betaine, benzylidene acetone, o-chlorobenzaldehyde, and sodium
cumene sulfonate. As before, such a composition could be combined
with a predetermined amount of an electrolyte composition according
to the invention.
[0071] The present invention further encompasses a method for
depositing a zinc-nickel alloy on a substrate by incorporating the
electroplating composition as described herein in an electroplating
process. In one embodiment, the method comprises immersing the
substrate in an electroplating composition according to the above
description and applying an electrical current to the immersed
substrate for a time sufficient to deposit a layer of zinc-nickel
alloy on the substrate.
[0072] The method of the invention is particularly useful in that
it provides a zinc-nickel alloy layer deposition with a desirable
nickel concentration, as well as pleasing aesthetic performance,
over a broad range of current densities. Uniform alloy composition
independent of current density is highly desirable in the field of
zinc-nickel alloy electroplating. In previously known zinc-nickel
deposition methods, the nickel content in the deposited alloy
increases significantly as the current density applied to the
substrate decreases. This is problematic in multiple aspects. A
zinc-nickel alloy layer deposited on a substrate can exhibit
multiple unfavorable characteristics when the weight percentage of
nickel present in the zinc-nickel alloy layer, based on the overall
weight of the zinc-nickel alloy layer, is greater than about 16%.
In particular, deposited zinc-nickel alloy layers having an average
nickel concentration greater than about 16% can exhibit unfavorable
properties, such as brittleness and difficulty in accepting
subsequent coatings, such as chrome conversion coatings.
Furthermore, when the average nickel concentration in the overall
deposited zinc-nickel alloy exceeds about 20%, the deposited alloy
becomes black in appearance, which is generally undesirable
(particularly when a bright, shiny finish is required).
[0073] Preferably, the zinc-nickel alloy deposited on the substrate
according to the method of the present invention has a weight
percent of nickel that is in the range of about 5% to about 15%,
based on the overall weight of the deposited zinc-nickel alloy.
According to further embodiments, the nickel content of the
deposited zinc-nickel alloy is about 6% to about 14%, about 7% to
about 13%, or about 8% to about 12%. A deposited zinc-nickel alloy
layer applied according to certain embodiments of the invention
having a nickel content within these ranges can generally be
expected to be bright, lustrous, and ductile, all of which are
highly desired properties in zinc-nickel alloy electroplated
substrates.
[0074] The electroplating method of the invention is particularly
useful in that the method can employ current densities across a
broad range without adversely affecting the physical or aesthetic
properties of the zinc-nickel alloy layer deposited on the
substrate. It is therefore possible to deposit a zinc-nickel alloy
layer on a substrate such that the average nickel concentration of
the overall layer is within a desired range even when the alloy
layer is deposited using a variety of current densities. In
particular embodiments, the desired average nickel concentration
can be achieved across a current density range of about 0.5 ASF to
about 120 ASF, about 2 ASF to about 50 ASF, or about 5 ASF to about
40 ASF.
[0075] It is understood that a zinc-nickel alloy layer deposited on
a substrate surface will generally have a specific nickel
concentration (in terms of the weight of nickel based on the
overall weight of the deposited alloy layer), as well as a specific
zinc-concentration, that varies somewhat from one discrete point to
another discrete point across the overall deposition layer. Average
nickel concentration could be experimentally determined by taking
specific measurements of nickel concentration at a number of points
(preferably a statistically significant number of points) across
the overall deposition layer and taking an average of the specific
measured nickel concentrations. Generally, it is expected that the
average nickel concentration for the overall zinc-nickel alloy
layer deposited on the substrate would not differ significantly
from the specific nickel concentration at any discrete point across
the deposition layer. Accordingly, as used herein, "average nickel
concentration" refers to the average nickel concentration across
the overall zinc-nickel deposition layer.
[0076] The nickel concentration can be measured using various known
methods. For example, alloy composition can be evaluated using an
X-ray fluorescence spectrophotometer, such as the Fischerscope XDAL
spectrophotometer available from Fischer Scientific. X-ray
fluorescence spectrophotometers use a spectroscopic technique that
is commonly used with solids, in which X-rays are used to excite a
sample and generate secondary X-rays as fluorescence, which are
sample dependant and element specific. Accordingly, specific
components of a coating, such as nickel in a zinc-nickel coating
layer, and can be easily quantified and analyzed upon calibration
with sample standards and use of applicable computer software.
X-ray fluorescence is commonly used in many different types of
analytical laboratories and some industrial inspection systems, and
X-ray fluorescence spectrometers provide a number of distinct
advantages including easy sample preparation and nondestructive
rapid multi-element analysis.
[0077] As noted above, currently known zinc-nickel alloy deposition
methods undesirably allow for changes in the percentage of nickel
in the overall deposition layer as a function of the current
density. For example, at one current density, a known deposition
method may form a zinc-nickel alloy layer having a specific average
nickel concentration, but at a lower current density the same
deposition method may form a zinc-nickel alloy layer having a much
greater average nickel concentration. Preferred embodiments of the
present invention do not suffer from such a limitation.
Accordingly, the consistent nickel concentration achieved according
to the present invention can be characterized in terms of a maximum
deviation between the highest average nickel concentration achieved
at a given current density within a range of densities and the
lowest average nickel concentration achieved at a given current
density within the same range of densities.
[0078] The present invention is particularly useful in that,
according to certain embodiments, a zinc-nickel layer can be
deposited with an average nickel concentration that is
substantially unchanged by differences in current density. In other
words, if all other deposition conditions remain unchanged, the
average nickel concentration of a zinc-nickel layer applied at one
specific current density would not be substantially changed if the
zinc-nickel layer was applied at a higher or lower current density.
Therefore, according to the present invention, it is possible to
apply a zinc-nickel layer to a substrate surface such that the
average nickel concentration of the applied layer is substantially
unchanged even when the current density is varied across a range of
densities.
[0079] The effect of current density on the average nickel
concentration of a deposited zinc-nickel layer can be easily
tested. In one testing method, a defined number of identical
substrates (for example, a steel plate of defined dimensions) can
successively have a zinc-nickel deposition layer applied thereto
wherein all deposition conditions are constantly maintained and
only current density is changed for each successive substrate. The
effect of current density can be determined by measuring the
average nickel concentration in the deposition layer for each
substrate and calculating the difference between the highest
average nickel concentration and the lowest average nickel
concentration for the various substrates. The effect of current
density on the average nickel concentration in a zinc-nickel
deposition layer is further illustrated in the Examples provided
below.
[0080] As used in relation to the present invention, the average
nickel concentration in a deposited zinc-nickel layer is
"substantially unchanged" when the difference between the highest
average nickel concentration and the lowest average nickel
concentration, as determined according to the above method, is less
than about 3 percentage points. In other words, the average nickel
concentration is "substantially unchanged" when the highest average
nickel concentration achieved at one current density within a
defined range of densities and the lowest average nickel
concentration achieved at a different current density within the
same range of densities (all other deposition conditions remaining
constant) differs by less than about 3 percentage points. In
further embodiments, "substantially unchanged" can refer to
differences between a highest average nickel concentration and a
lowest average nickel concentration that is even smaller. For
example, the average nickel concentration can be "substantially
unchanged" when the difference is less than about 2.5 percentage
points, less than about 2 percentage points, or less than about 1.5
percentage points.
[0081] In light of the above, it is possible to characterize the
present invention in terms of an average nickel concentration range
across a current density range. Such a characterization provides a
maximum variation in the average nickel concentration of a
zinc-nickel deposition layer if the layer was deposited using two
or more different current densities while keeping all other
deposition conditions constant.
[0082] In one embodiment, the invention provides a method for
depositing a zinc-nickel layer on a substrate such that the average
nickel concentration in the deposited layer varies by less than
about 3 percentage points when the current density during the
deposition is in the range of about 2 ASF to about 50 ASF.
According to further embodiments, the average nickel concentration
in the deposited varies by less than about 2.5 percentage points,
less than about 2 percentage points, or less than about 1.5
percentage points. According to another embodiment, the invention
provides a method for depositing a zinc-nickel layer such that the
average nickel concentration in the deposited layer varies by less
than about 2.5 percentage points, preferably less than about 2
percentage points and more preferably less than about 1.5
percentage points, when the current density during the deposition
is in the range of about 5 ASF to about 40 ASF.
[0083] In yet further embodiments, the invention provides
deposition methods wherein the average nickel concentration remains
substantially unchanged across a broader current density range. For
example, in one embodiment, invention provides a method for
depositing a zinc-nickel layer on a substrate such that the average
nickel concentration in the deposited layer varies by less than
about 3 percentage points, preferably less than about 2.5
percentage points and more preferably less than about 2 percentage
points, when the current density during the deposition is in the
range of about 0.5 ASF to about 120 ASF.
[0084] The method of the invention is further beneficial in that
the concentration of zinc ions and nickel ions in the
electroplating composition during the electroplating method can be
maintained by using zinc and nickel metal anodes (or zinc-nickel
alloy anodes) that oxidize during the electroplating method. The
metal anodes oxidize and partially dissolve during the
electroplating process, thereby supplying additional zinc ions and
nickel ions to the electroplating composition. Further, if
necessary, the concentration of zinc ions and nickel ions in the
electroplating composition can be adjusted during the
electroplating method by addition of further amounts of the zinc
ion source and the nickel ion source, as described above.
[0085] The pH of the electroplating composition, as noted
previously, is controlled through incorporation of appropriate pH
buffering agents in the electrolyte composition. Such buffering
agents are preferably suitable for maintaining the preferred pH
throughout the electroplating method. The temperature of the
electroplating composition is preferably controlled throughout the
electroplating method to be within a range of about 85.degree. F.
(29.4.degree. C.) to about 120.degree. F. (48.9.degree. C.), more
preferably in the range of about 90.degree. F. (32.2.degree. C.) to
about 110.degree. F. (49.3.degree. C.), most preferably about
95.degree. F. (35.degree. C.) to about 105.degree. F. (40.6.degree.
C.).
EXAMPLES
[0086] Various zinc-nickel alloy electroplating compositions were
evaluated to determine the effect of various organic compositions
in combination with a standard electrolyte composition according to
the invention to deposit a zinc-nickel alloy layer on a substrate.
The various compositions were evaluated in terms of the physical
appearance of the zinc-nickel alloy layer deposited on the
substrate and the average concentration of nickel in the deposited
layer when the deposition is performed at various specific current
densities.
[0087] Electroplating was conducted in a standard
thermostat-controlled 267 ml Hull cell with zinc and nickel anodes.
The zinc anodes were pretreated in a solution for 24 hours prior to
use, the solution containing 55 g/L nickel chloride and 255 g/L
ammonium chloride. The pretreatment step is useful in that the zinc
anodes will spontaneously form a nickel coating in the plating
bath. Pre-forming the coating prior to use of the anode in the
electroplating bath is beneficial in that it provides an improved
appearance of the deposition layer applied to the substrate. Steel
panels were used as the cathodes for the cell. The steel panels
were treated in 50% hydrochloric acid prior to electroplating
evaluations.
[0088] During electroplating, cell current was applied at a range
of 1-2 Amperes for a time of 5 minutes, and cell temperature was
100.degree. F., +/-5.degree. F. (37.8.degree. C., +/-2.8.degree.
C.). Cell pH was adjusted to a range of 5.5 to 5.7 using an acid or
base, such as hydrochloric acid or sodium or potassium
hydroxide.
[0089] The various electroplating compositions used in the
evaluation are provided in Table 2 below. For each electroplating
composition, the zinc-nickel alloy layer applied to the substrate
was evaluated for appearance and was also evaluated for alloy
composition using a Fischerscope XDAL X-ray fluorescence
spectrophotometer at 5, 10, 20, and 40 Amperes/ft.sup.2 (ASF).
[0090] The electrolyte composition used in each electroplating
composition evaluated was constant and is provided below in Table
1. Concentration is provided in relation to the total volume of the
overall composition. TABLE-US-00001 TABLE 1 Electrolyte Component
Concentration (g/L) NiCl.sub.2.6H.sub.2O 140 ZnCl.sub.2 115 KCl 245
H.sub.3BO.sub.3 40 CH.sub.3CO.sub.2Na 40
[0091] Only the electrolyte composition was present in the
electroplating composition evaluated in Example 1. In Examples
2-18, however, varying organic compositions were also included in
the electroplating composition for evaluation. The evaluations of
the coatings applied using the various electroplating compositions
are provided below. TABLE-US-00002 TABLE 2 Alloy Composition % Ni
Ex. Appearance 40 20 10 5 No. Electroplating Composition 40 ASF 20
ASF 10 ASF 5 ASF ASF ASF ASF ASF 1 250 ml electrolyte composition
Cloudy Cloudy Black Black 9.8 10.8 13.5 17.6 grey grey 2 250 ml
electrolyte composition Cloudy Cloudy Cloudy Dark 8.3 8.9 10.3 13.8
2.0 g/L sodium saccharin grey grey grey silver 20 mg/L benzylidene
acetone 0.5 ml New Era Wetter* 3 250 ml electrolyte composition
Hazy Hazy Hazy Black 10.6 13.0 13.8 15.4 2.0 g/L sodium saccharin
grey grey grey 0.2 g/L IGEPAL CO-730 20 mg/L benzylidene acetone
0.5 ml New Era Wetter* 4 250 ml electrolyte composition Slightly
Slightly Slightly Bright 9.7 12.6 14.7 16.7 2.0 g/L sodium
saccharin hazy hazy hazy 0.2 g/L sodium benzoate 40 mg/L benzyl
niacin 50 mg/L benzylidene acetone 5 250 ml electrolyte composition
Cloudy Cloudy Cloudy Bright 10.3 11.8 13.6 16.0 2.0 g/L sodium
saccharin white white white 1 g/L niacin 1 g/L salicylic acid 6 250
ml electrolyte composition Cloudy Slightly Slightly Bright 5.7 8.2
11.6 15.0 1.6 g/L sodium saccharin white hazy hazy 0.2 g/L sodium
benzoate 50 mg/L benzylidene acetone 7 250 ml electrolyte
composition Cloudy Bright Slightly Bright 10.1 11.5 14.0 13.8 1.6
g/L sodium saccharin white hazy 0.2 g/L sodium salicylate 0.1 g/L
sodium benzoate 4 mg/L benzylidene acetone 8 250 ml electrolyte
composition Cloudy Cloudy Cloudy Cloudy 5.7 8.2 10.0 13.6 2.0 g/L
sodium saccharin white white white white 1 g/L niacin 1 g/L
salicylic acid 0.2 g/L Witcolate D51-53 9 250 ml electrolyte
composition Slightly Bright Bright Bright 11.3 11.9 12.3 14.0 0.2
g/L sodium benzoate hazy 0.62 g/L Nape 14-90 4 mg/L benzylidene
acetone 10 250 ml electrolyte composition Cloudy Cloudy Slightly
Black 13.3 15.5 17.4 23.9 0.13 g/L dimethyldiallyl- grey grey hazy
ammonium chloride 11 250 ml electrolyte composition Cloudy Cloudy
Bright Black 11.1 12.6 14.1 14.9 0.2 g/L bis- white white
benzenesulfonylimide 0.13 g/L dimethyldiallyl- ammonium chloride 12
250 ml electrolyte composition Cloudy Cloudy Slightly Slightly 10.5
12.1 13.2 17.1 0.1 g/L salicylic acid white white hazy black 0.2
g/L bis- benzenesulfonylimide 0.13 g/L dimethyldiallyl- ammonium
chloride 13 250 ml electrolyte composition Slightly Slightly Bright
Bright 10.4 11.1 12.9 12.1 0.62 g/L Nape 14-90 hazy hazy 0.2 g/L
Carbowax 3350 0.26 g/L dimethyldiallyl- ammonium chloride 4 mg/L
benzylidene acetone 14 250 ml electrolyte composition Cloudy Cloudy
Cloudy Cloudy 3.6 4.8 5.7 8.6 1.6 g/L sodium saccharin white white
white white 0.1 g/l sodium benzoate 0.4 g/L Carbowax 3350 8 mg/L
benzylidene acetone 0.5 ml New Era Wetter* 15 250 ml electrolyte
composition Bright Bright Bright Hazy 5.9 6.4 7.1 8.7 2.0 g/L
sodium saccharin 1.3 g/L dimethyldiallyl- ammonium chloride 0.2 g/L
Witcolate D51-53 20 mg/L benzylidene acetone 0.5 ml New Era Wetter*
16 250 ml electrolyte composition Cloudy Cloudy Slightly Bright
10.3 10.0 9.4 11.1 1.6 g/L sodium saccharin white white dull 0.6
g/L bis- benzenesulfonylimide 0.2 g/L sodium benzoate 0.3 g/L Nape
14-90 0.2 g/L Carbowax 3350 0.26 g/L dimethyldiallyl- ammonium
chloride 4 mg/L benzylidene acetone 17 250 ml electrolyte
composition Slightly Slightly Slightly Slightly 11.1 10.5 10.1 9.8
1.6 g/L sodium saccharine dull dull dull dull 0.6 g/L
bis-benzenesufonylimide 0.2 g/L sodium benzoate 0.62 g/L Nape 14-90
0.2 g/L Carbowax 3350 0.26 g/L dimethyldiallyl- ammonium chloride 2
mg/L benzylidene acetone 18 250 ml electrolyte composition Bright
Bright Bright Bright 8.8 10.5 10.8 10.1 1.6 g/L sodium saccharin
0.6 g/L bis- benzenesulfonylimide 0.2 g/L sodium benzoate 0.62 g/L
Nape 14-90 0.2 g/L Carbowax 3350 0.26 g/L dimethyldiallyl- ammonium
chloride 3.8 mg/L benzylidene acetone 6.1 mg/L o-chlorobenzaldehyde
0.4 g/L sodium cumene sulfonate 19 250 ml electrolyte composition
Bright Bright Bright Bright 10.4 9.2 8.9 10.4 1.6 g/L sodium
saccharin 0.6 g/L bis- benzenesulfonylimide 0.2 g/L sodium benzoate
0.62 g/L Nape 14-90 0.2 g/L Carbowax 3350 0.26 g/L dimethyldiallyl-
ammonium chloride 0.08 g/L 2-thiohydantoin 3.8 mg/L benzylidene
acetone 6.1 mg/L o-chlorobenzaldehyde 0.4 g/L sodium cumene
sulfonate 20 250 ml electrolyte composition Bright Bright Bright
Bright 9.5 8.5 9.7 8.5 1.6 g/L sodium saccharin 0.6 g/L bis-
benzenesulfonylimide 0.2 g/L sodium benzoate 0.62 g/L Nape 14-90
0.2 g/L Carbowax 3350 0.26 g/L dimethyldiallyl- ammonium chloride
0.08 g/L Carboxyethyl isothiuronium betaine 3.8 mg/L benzylidene
acetone 6.1 mg/L o-chlorobenzaldehyde 0.4 g/L sodium cumene
sulfonate *New Era Wetter is a surface tension reducing agent
available commercially from Pavco, Inc.
[0092] As can be seen from Table 2 above, preferred embodiments
according to the invention are particularly useful for deposition
of a zinc-nickel alloy with a consistent percentage nickel in a
preferred range, even across a broad current density. Preferred
embodiments are shown in Examples 16-20. As can be seen in these
examples, the concentration of nickel in the deposited zinc-nickel
alloy varies across the four current densities tested by less than
2 percentage points (e.g., in Example 17, the highest nickel
concentration was 11.1%, while the lowest nickel percentage was
9.8%--a difference of only 1.3 percentage points). A particularly
preferred composition according to the invention is provided in
Example 18. Examples 1-15 are provided as comparative formulations
that are less effective at providing high quality deposition
coatings, such as seen with the compositions according to the
invention. Example 1, particularly, is provided as a baseline
comparative of results achieved using an electrolyte composition
alone.
[0093] Many modifications and other embodiments of the inventions
set forth herein will come to mind to one skilled in the art to
which these inventions pertain having the benefit of the teachings
presented in the foregoing descriptions. Therefore, it is to be
understood that the inventions are not to be limited to the
specific embodiments disclosed and that modifications and other
embodiments are intended to be included within the scope of the
appended claims. Although specific terms are employed herein, they
are used in a generic and descriptive sense only and not for
purposes of limitation.
* * * * *