Technical Field
[0001] The present invention relates to an acidic zinc plating bath, for example, for zinc
electroplating suited for bright zinc plating of metal parts.
Background Art
[0002] With regards to various metal parts such as processed goods or molded or formed products,
for example, pins, bolts, and nuts, zinc plating has been widely used in order to
enhance their corrosion resistance and fine appearance.
[0003] Zinc plating includes hot dip galvanizing, zinc electroplating, and the like. When
various metal parts are plated through zinc electroplating, a plating bath is used.
In this case, a cyan bath or zincate bath is used as an alkali bath, while a sulfate
bath or chloride bath is used as an acidic bath (refer to, for example, Patent Documents
1 to 5)
[0004] The acidic bath is popularly used as a plating bath of industrial products such as
bolts and nuts because it has a good current efficiency and is therefore suited for
processing large quantities. A chloride bath features high productivity and high plating
adherence to castings so that it is used popularly. A chloride bath includes an ammonium
bath, and a potassium bath, and an eclectic bath using both. Recently, the ammonium
bath and the potassium bath however cannot be used freely because of strict regulations
on nitrogen-containing effluent and regulations on effluent containing boron derived
from boric acid added as a buffer, respectively. The potassium bath uses no ammonium
but compared with the ammonium bath or eclectic bath, abnormal depositions called
"burnt deposits" appear at a high current portion so that it is inferior in productivity.
Therefore, an eclectic bath has been popular.
[0005] In a bright zinc plating using an acidic plating bath, addition of an organic compound
called "brightener" is inevitable in order to give brightness to plating. A naphthol
anionic surfactant has conventionally been used as a brightener component (refer to,
for example, Patent Document 6).
[0006] Since the temperature of the acidic bath increases when a current is supplied thereto
and due to an influence of the surfactant contained therein, the bath becomes turbid,
which leads to loss of brightness, the bath has conventionally been used often at
a temperature as low as from about 20 to 25°C. It therefore needs cooling, which is
a factor of a cost increase. In contrast,in recent years, using it at a temperature
as high as from 30 to 50°C has been increasing, partly because plating at high temperatures
improves a current efficiency.
Prior Art Documents
Patent Documents
[0008] However, the conventional high-temperature acidic zinc plating baths have been inferior
in stability of the bath. Variation in pH has occurred or turbitidy or precipitate
have appeared when using them at a temperature as high as from about 30 to 50°C. This
means that in order to use them at a temperature as high as from 30 to 50°C, it is
necessary to prevent turbitidy which will otherwise occur due to the influence of
a surfactant contained in a brightener. In addition, decomposition products or precipitates
have been observed in the plating solution.
[0009] When plating is conducted continuously, a decrease in cloud point has been observed
after predetermined energization. This means that it is difficult to keep the initial
plating performance of a high-temperature bath and the plating bath has a problem
in long-term stability. In order to raise the cloud point and thereby improve the
solubility/dispersibility of the plating bath, an amount of the anionic surfactant
can be increased but an excess amount becomes a cause for deteriorating the plating
performance.
[0010] An object of the present invention is to provide an acidic zinc plating bath having
improved long-term stability even at a temperature as high as about 30 to 50°C.
Summary of the Invention
[0011] The present inventors have found that the above-described object can be achieved
by using a cumylphenol anionic surfactant for a brightener. In short, the present
invention provides the following acidic zinc plating bath.
[0012] [1] An acidic zinc plating bath including a conductive salt, a metallic zinc, and
a brightener and containing, as a component of the brightener, at least one kind of
cumylphenol anionic surfactant.
[0013] [2] The acidic zinc plating bath as described above in [1], containing, as an acidic
bath component thereof, zinc chloride and at least one compound selected from the
group consisting of ammonium chloride, potassium chloride, and sodium chloride.
[0014] [3] The acidic zinc plating bath as described above in [1] or [2], wherein the cumylphenol
anionic surfactant is an alkylene oxide adduct of a sulfate.
[0015] [4] The acidic zinc plating bath as described above in [3], wherein the alkylene
oxide adduct of a sulfate has from 1 to 30 moles ethylene oxide as alkylene oxide.
[0016] [5] The acidic zinc plating bath as described above in [3], wherein the alkylene
oxide adduct of a sulfate is polyoxyethylene para-cumylphenyl ether sulfate.
[0017] A cumylphenol anionic surfactant has good dispersibility and is effective for increasing
a cloud point so that the cloud point of a plating solution stably changes upon using
and the plating solution is free from turbidity and precipitation. In short, it improves
the long-term stability upon using a bath. In addition, using a cumylphenol anionic
surfactant as a brightener enables to keep the brightness of plating upon using (from
room temperature to 70°C). The plating bath containing it can therefore be used stably
at a high temperature at which the conventional bath is inferior in stability.
Brief Description of the Drawings
[0018]
Fig. 1 is a schematic view showing the results of a hull cell test of a plating bath
of Example 1 which is an eclectic bath (NH4Cl-K).
Fig. 2 is a schematic view showing the results of a hull cell test of a plating bath
of Comparative Example 4 which is a β-naphthol eclectic bath (NH4Cl-K).
FIG. 3 is a schematic view showing the results of a hull cell test of a β-naphthol
eclectic bath (NH4Cl-K).
FIG. 4 is a schematic view showing the results of a hull cell test of a β-naphthol
eclectic bath (NH4Cl-Na).
FIG. 5 is a schematic view showing the results of a hull cell test of a potassium
chloride bath and a sodium chloride bath.
FIG. 6 is a schematic view showing the results of a hull cell test of a potassium
chloride bath and a sodium chloride bath, each containing boric acid.
FIG. 7 is a schematic view showing the results of a hull cell test of an ammonium
chloride bath.
Mode for Carrying out the Invention
[0019] The embodiments of the present invention will next be described referring to some
drawings. It should however be noted that the present invention is not limited to
or by the following embodiments and it can be changed, modified, or improved without
departing from the scope of the present invention.
[0020] The acidic zinc plating bath of the present invention includes a conductive salt,
a metallic zinc, and a brightener and it contains, as a component of the brightener,
at least one kind of cumylphenol anionic surfactant. The cumylphenol anionic surfactant
is preferably an alkylene oxide adduct of a sulfate, with a 1-30 moles ethylene oxide
adduct of a sulfate being especially preferred. As an example of the alkylene oxide
adduct of a cumylphenol sulfate, polyoxyethylene para-cumylphenyl ether sulfate (the
following formula (1)) will next be given.
[0021]

[0022] In the above formula, EO represents ethylene oxide and n stands for the number of
moles of EO, preferably from 1 to 30, more preferably from 5 to 15, most preferably
7. It is contained in the acidic zinc plating solution in an amount of preferably
from 1 to 3 g/L, more preferably 2 g/L. The sulfate is preferably potassium salt,
but sodium salt and amine salt are also usable.
[0023] When cumylphenol selected as the anionic surfactant is incorporated in an acidic
zinc plating bath, it enables stable change of the cloud point of the plating solution
upon plating and is therefore effective for preventing generation of turbidity or
precipitate of the plating solution. As an anionic surfactant, components other than
cumylphenol one can be contained in the bath. For example, addition of a cumylphenol
anionic surfactant to a bath containing, for example, a β-naphthol anionic surfactant
is also effective for increasing the cloud point. This means that the effect of increasing
the cloud point can be attained not only by replacement of the β-naphthol anionic
surfactant, which is a conventionally used surfactant added to a zinc chloride plating
bath, with the cumylphenol anionic surfactant but also by addition of the cumylphenol
anionic surfactant to the β-naphthol-added plating bath and use them in combination.
Addition of the cumylphenol anionic surfactant increases the cloud point, widens the
area of a bright plated surface (hull cell), and stabilizes the plating bath.
[0024] As the brightener, a brightener base and a brightener are used. The brightener base
contains an anionic surfactant (containing from 10 to 15 mass%), a nonionic surfactant,
an aromatic carboxylate, and an organic amine salt. The brightener contains an anionic
surfactant (containing from 10 to 15 mass%), a nonionic surfactant, an aromatic carboxylate,
an organic amine salt, and an aromatic aldehyde. The brightener base and the brightener
are supplied to a plating bath so that the bath contains the following components
at the following concentrations, respectively: an anionic surfactant (from 1 to 5
g/L), a nonionic surfactant (from 1 to 5 g/L), an organic amine (from 0.5 to 5 g/L),
an aromatic carboxylate (from 1 to 2 g/L), and an aromatic aldehyde (from 0.01 to
0.1 g/L).
[0025] The brightener base and the brightener containing, as the anionic surfactant, the
above alkylene oxide adduct of a cumylphenol sulfate can help the aromatic aldehyde,
which is a component of the brightener to give brightness, to improve the brightness.
The alkylene oxide adduct of a cumylphenol sulfate undergoes less deterioration in
performance when current is applied for plating so that it is anti-aging. In addition,
it can increase the cloud point and thereby decrease turbidity and precipitation of
the plating solution.
[0026] An increase in the cloud point leads to an increase in solubility/dispersibility
of the surfactant so that it is suited for use at high temperatures. It is desired
to set the cloud point high because electrical decomposition products appear in the
Zn plating bath upon plating, which decreases the cloud point. Among the components
of the brightener of acidic Zn plating for use at high temperatures (from 30 to 70°C),
the anionic surfactant plays an important role. The cumylphenol anionic surfactant
is superior in the performance of dissolving/dispersing the other components and this
increases the cloud point.
[0027] Adding the anionic surfactant has improved brightness and it has a higher cloud point
with an increase in the amount of the anionic surfactant. The cloud point cannot be
maintained when an amount of the anionic surfactant is small. On the other hand, excessive
addition causes stain and foaming as well as deterioration in throwing power and plating
appearance, which results in deterioration in plating performance. The amount of the
anionic surfactant is preferably from 1 to 5 g/L with respect to the plating appearance.
[0028] Adding the nonionic surfactant has improved uniform electrodeposition and improved
brightness at a low current portion. Examples of the nonionic surfactant include polyoxyethylene
oxide.
[0029] The acidic zinc plating bath containing the aromatic carboxylate can have improved
brightness at a low current portion. Examples of the aromatic carboxylate include
benzoates, salicylates, cinnamates, and m. P-chlorobenzoates and soluble salts thereof.
[0030] Adding the organic amine salt causes less burnt deposits at a high current portion.
Examples of the organic amine salt include polyethyleneimine, modified polyethyleneimine,
and polyalkylene polyamine.
[0031] Adding the aromatic aldehyde can have improve brightness. Examples of the aromatic
aldehyde include benzaldehyde and benzylidene acetone.
[0032] The acidic zinc plating bath of the present invention is an acidic zinc electroplating
bath and it includes various acidic baths containing a conductive salt. That is, the
various acidic baths have improved long-term stability by containing a cumylphenol
anionic surfactant. As the acidic zinc plating bath, a chloride bath containing zinc
chloride is preferred. Examples of the chloride bath include ammonium chloride bath,
potassium chloride bath, and sodium chloride bath, and eclectic baths thereof. It
can be used for any of them. This means that it can be used for a chloride bath containing
at least any of ammonium chloride, potassium chloride, and sodium chloride. In particular,
an eclectic bath containing zinc chloride, ammonium chloride, and potassium chloride
is particularly preferred. Although a sodium salt is conventionally unsatisfactory
in long-term stability because it decreases the cloud point more than a potassium
salt, the sodium chloride bath containing the cumylphenol anionic surfactant has an
improved cloud point and can be used stably. The acidic zinc plating has the following
characteristics: it does not use cyan, has a good current efficiency and has therefore
a high plating rate, and can be used for direct plating to cast or heat-treated products.
[0033] As a zinc ion supply source, one or more zinc salts selected from zinc chloride,
zinc sulfate, zinc sulfite, zinc borofluoride, zinc sulfamate, and zinc methanesulfonate
can be used. As the zinc ion supply source, zinc chloride is preferred. Alternatively,
the zinc ion is supplied by electrodissolution of a metallic zinc of a polar plate.
[0034] The acidic zinc plating bath of the present invention can contain, in addition to
the above components, minor components ordinarily added to a plating solution such
as anti-foaming agent. The pH range of the plating solution is preferably from 5 to
7, more preferably from 5.8 to 6.3. The plating solution is therefore acidic.
[0035] No particular limitation is imposed on the composition of the acidic zinc plating
bath of the present invention but the following is an example of a preferable composition
of the plating solution.
Zinc chloride: from 30 to 60 g/L (range of use: from 10 to 120 g/L)
Ammonium chloride: from 50 to 200 g/L (range of use: from 0 to 300 g/L)
Potassium chloride: from 0 to 150 g/L (range of use: from 0 to 300 g/L)
Nonionic surfactant: from 1 to 5 g/L Polyethyleneimine: from 0.5 to 5 g/L
Benzylidene acetone: from 0.01 to 0.1 g/L
Sodium benzoate: from 1 to 5 g/L
pH: from 5.8 to 6.3
[0036] In the present invention, when the content of zinc chloride is outside the above
range, it is impossible to carry out desired bright zinc plating efficiently. It is
preferably from 30 to 60 g/L. Contents of ammonium chloride exceeding 300 g/L lead
to a high nitrogen concentration. It is preferably from 50 to 150 g/L. Potassium chloride
is contained in order to maintain the conductivity of the plating bath and decrease
a nitrogen concentration. Potassium chloride is contained in an amount of preferably
from 50 to 150 g/L. In order to maintain the conductivity of the plating bath, it
is replenished with ammonium chloride or potassium chloride to give a chloride ion
amount of from 120 to 180 g/L.
[0037] In the present invention, an ordinarily used surfactant such as nonionic surfactant
may be added as needed. Components of the plating bath are added in predetermined
amounts and constitute an aqueous solution thereof. The pH of the solution is adjusted,
for example, with hydrochloric acid to usually from 5.8 to 6.3. The acidic zinc plating
bath of the present invention may contain from 1 to 50 g/L of boric acid.
[0038] Bright zinc plating of metal parts with the plating bath thus adjusted may be performed
in a conventional manner and no particular limitation is imposed in the present invention.
In the present invention, however, due to a reduction in nitrogen concentration, improvement
in the working environment and simplification of effluent treatment can be realized.
[0039] A current density can be set at from 0.3 to 5.0 A/dm
2 on average, which is almost equal to that in the conventional zinc chloride plating
bath. Thus, the plating bath of the present invention is comparable to the conventional
one also in the plating efficiency. As described above, use of a cumylphenol anionic
surfactant as a brightener leads to improvement in the long-term stability of a plating
solution when it is used at a temperature of from room temperature to 70°C.
Examples
[0040] The present invention will hereinafter be described more specifically based on Examples.
It should however be noted that the present invention is not limited to or by them.
1-1. Eclectic bath (NH4Cl-K)
[0041] As a solution with a basic composition to be used for a plating solution, a basic
solution A shown in Table 1 was prepared. The basic solution A was a mixture of 40
g/L of zinc chloride, 150 g/L of potassium chloride, and 50 g/L of ammonium chloride
and had a pH of 6.0.
[0042]
[Table 1]
Basic solution |
A |
B |
C |
E |
D |
F |
G |
Bath |
Eclectic bath (NH4Cl-K) |
Eclectic bath (NH4Cl-Na) |
Potassium chloride bath |
Potassium chloride bath (containing boric acid) |
Sodium chloride bath |
Sodium chloride bath (containing boric acid) |
Ammonium chloride bath |
Zinc chloride |
40 g/L |
40 g/L |
60 g/L |
60 g/L |
60 g/L |
60 g/L |
40 g/L |
Potassium chloride |
150 g/L |
- |
265 g/L |
250 g/L |
- |
- |
- |
Sodium chloride |
- |
150 g/L |
- |
- |
265 g/L |
250 g/L |
- |
Ammonium chloride |
50 g/L |
50g/L |
- |
- |
- |
- |
200 g/L |
Boric acid |
- |
- |
- |
25 g/L |
- |
25 g/L |
- |
Hull cell test |
pH |
6.0 |
6.0 |
6.0 |
6.0 |
6.0 |
6.0 |
6.0 |
Bath temperature |
40°C |
40°C |
40°C |
40°C |
40°C |
40°C |
40°C |
Current density (average) |
2 A/dm2 |
2 A/dm2 |
2 A/dm2 |
2 A/dm2 |
2 A/dm2 |
2 A/dm2 |
2 A/dm2 |
(Example 1)
[0043] Next, to the basic solution A of Table 1 was added an anionic surfactant listed in
Table 2. For example, in Example 1, the basic composition A composed of 40 g/L of
zinc chloride, 150 g/L of potassium chloride, and 50 g/L of ammonium chloride was
mixed with 1 g/L of a 7 mole EO polyoxyethylene para-cumylphenyl ether sulfate, specifically
potassium salt. Further, it was mixed with a nonionic surfactant, 2 g/L of an aromatic
carboxylate, 1 g/L of an organic amine salt, and 0.05 g/L of an aromatic aldehyde.
Similarly, respective mixtures with 2 g/L and 3 g/L of a 7 mole EO polyoxyethylene
para-cumylphenyl ether sulfate, specifically potassium salt were prepared. The following
is the potassium polyoxyethylene para-cumylphenyl ether sulfate (represented by the
following formula (1)).
[0044]

(Examples 2 to 4)
[0045] In a similar manner to Example 1, plating baths having the composition as shown in
Table 2 were prepared.
(Comparative Example 1)
[0046] As shown in Table 2, a plating bath was prepared by mixing a naphthol anionic surfactant
with the basic solution A. In Comparative Example 1, the anionic surfactant is the
following potassium polyoxyethylene β-naphthyl ether sulfate (m=3, n=12) (represented
by the following formula (2)). In the formula, EO represents ethylene oxide and PO
represents propylene oxide.
[0047]

(Comparative Example 2)
[0048] As shown in Table 2, a plating bath was prepared by mixing a naphthol anionic surfactant
with the basic solution A. In Comparative Example 2, the anionic surfactant is the
following sodium polyoxyethylene β-naphthyl ether sulfate (n=12) (represented by the
following formula (3)).
[0049]

(Comparative Example 3)
[0050] As shown in Table 2, a plating bath was prepared by mixing a naphthol anionic surfactant
with the basic solution A. In Comparative Example 2, the anionic surfactant is the
following potassium polyoxyethylene oxypropylene naphthyl sulfonate (m=3, n=13) (represented
by the following formula (4)).
[0051]

(Comparative Examples 4 to 5)
[0052] As shown in Table 2, a plating bath using a β-naphthol anionic surfactant was prepared.
In Comparative Examples 4 and 5, the basic solutions were obtained by adding a base
agent A (MZ-996A in Comparative Example 4 and ZB-627A in Comparative Example 5) and
a brightener GC as needed (refer to the amount listed in Table 2), respectively. The
base agent A and the brightener GC contain an anionic surfactant, a nonionic surfactant,
an aromatic carboxylate, an organic amine, and an aromatic aldehyde.
(Cloud point)
[0053] The cloud point was measured in the following manner. First, 100 ml of a sample solution
(plating solution) was weighed in a 100-ml heat-resistant glass beaker. Then, the
sample solution was heated with an electric heater or the like and then stirred so
as to give a uniform solution temperature. The temperature at which, when a thermometer
was stood at the center of the 100-ml beaker, the thermometer disappeared due to turbidity
was recorded.
[0054]
[Table 2]
|
Plating bath |
Cloud point |
|
Amount of brightener |
Anionic surfactant |
Salt used |
|
Amount |
Example 1 |
Basic solution A |
|
K salt
7 moles of EO |
Polyoxyethylene para-cumylphenyl ether sulfate |
1 g/L |
|
65°C |
2 g/L |
Recommended |
80°C |
3 g/L |
|
95°C |
Example 2 |
Basic solution A |
|
K salt
5 moles of EO |
Polyoxyethylene para-cumylphenyl ether sulfate |
1 g/L |
|
65°C |
2 g/L |
Recommended |
80°C |
3 g/L |
|
95°C |
Example 3 |
Basic solution A |
|
K salt
13 moles of EO |
Polyoxyethylene para-cumylphenyl ether sulfate |
1 g/L |
|
65°C |
2 g/L |
Recommended |
80°C |
3 g/L |
|
95°C |
Example 4 |
Basic solution A |
|
K salt
15 moles of EO |
Polyoxyethylene para-cumylphenyl ether sulfate |
1 g/L |
|
70°C |
2 g/L |
Recommended |
85°C |
3 g/L |
|
98°C |
Comp. Ex. 1 |
Basic solution A |
|
K salt
13 moles of EO |
Polyoxyethylene naphthyl ether sulfate |
1 g/L |
|
50°C |
2 g/L |
Normal |
55°C |
3 g/L |
|
60°C |
Comp. Ex. 2 |
Basic solution A |
|
Na salt
13 moles of EO & 3 moles of PO |
Polyoxyethylene oxypropylene naphthyl sulfate |
1 g/L |
|
55°C |
2 g/L |
Normal |
65°C |
3 g/L |
|
70°C |
Comp. Ex. 3 |
Basic solution A |
|
K salt
13 moles of EO & 3 moles of PO |
Polyoxyethylene oxypropylene naphthyl sulfonate |
1 g/L |
|
65°C |
2 g/L |
Normal |
70°C |
3 g/L |
|
75°C |
Comp. Ex. 4 |
Basic solution A Plating bath for high bath temperature METASU MZ-996A/GC |
MZ-996A: 20 mL/L GC:0.5 mL/L |
|
β-Naphthol |
|
72°C |
Comp. Ex. 5 |
Basic solution A General bath METASU ZB-627A/GC |
ZB-627A: 30 mL/L GC:1 mL/L |
|
β-Naphthol |
|
50°C |
Example 5 |
Basic solution A Plating bath for high bath temperature METASU MZ-996A/GC |
MZ-996A: 20 ML/L GC:0.5 mL/L |
K salt
7 moles of EO |
Polyoxyethylene para-cumylphenyl ether sulfate |
2 g/L |
75°C |
Example 6 |
Basic solution A General bath METASU ZB-627A/G |
ZB-627A: 30 mL/L G:1 mL/L |
K salt
7 moles of EO |
Polyoxyethylene para-cumylphenyl ether sulfate |
2 g/L |
70°C |
* METASU MZ-996A/GC: product of Yuken Industry
* METASU ZB-627AIGC: product of Yuken Industry |
[0055] As shown in Table 2, Examples using a cumylphenol surfactant have a higher cloud
point than that of Comparative Examples. A new solution of Comparative Example 4 had
a cloud point of 72°C, but it was not suited for long-term use because it decrease
due to aging of the solution as a result of current application. The term "recommended"
or "normal" amount in the table means the most suited amount. Since an increase in
the amount of the anionic surfactant leads to deterioration in throwing power, the
"normal" amount is used as the most appropriate amount in Comparative Examples and
the "recommended" amount is used as the most appropriate amount in Examples.
[0056] Each of a new solution and an old solution of Example 1 and Comparative Example 4
was studied for cloud point, turbidity, and stability. The term "old solution" means
a plating solution supplied with a current continuously for plating (120 AH/L). This
corresponds to an amount of current supplied to a common plating line per month.
[0057]
[Table 3]
|
Example 1 |
Comp. Ex. 4 |
Cloud point |
New solution |
80°C |
72°C |
Old solution |
85°C |
70°C |
Turbidity |
Good |
Fair |
Stability |
Good |
Fair |
[0058] As shown in Table 3, Example 1 has a higher cloud point and has improved turbidity
and stability irrespective of the new solution or old solution, compared with that
of Comparative Example 4. Incidentally, having no turbidity/precipitate and showing
no change was rated "good, while having slight turbidity/precipitate was rated "fair".
(Hull cell test)
[0059] In addition, a hull cell test was performed to observe the condition of a plating
bath. The hull cell test was performed for a new solution and an old solution of each
of Example 1 and Comparative Example 4 by supplying a current of 1A to the plating
bath for 10 minutes while adjusting the temperature of the bath to 40°C.
[0060] The results of the hull cell test of Example 1 are shown schematically in FIG. 1,
while those of Comparative Example 4 are shown schematically in FIG. 2. As illustrated
in FIG. 1, slight cloudiness is observed at a low current portion in both the new
solution and the old solution in Example 1. In Comparative Example 4, on the other
hand, widespread cloudiness is observed at a low current portion as illustrated in
FIG. 2. In addition, in Comparative Example 4, burnt deposits are observed at a high
current portion.
(Trivalent Cr chemical conversion treatment)
[0061] Test pieces which had been zinc plated with Example 1 and Comparative Example 4 were
subjected to trivalent Cr chemical conversion treatment, respectively.
(1) YFA treatment:
[0062] Trivalent Cr chemical conversion treatment was performed using a trivalent Cr chemical
conversion agent produced by Yuken Industry. The treatment was performed for 40 seconds
in a plating bath of 40°C and pH 2.0 by using 100 ml/L of YFA-M and 10 ml/L of YFA-HR.
(2) YFB treatment:
[0063] Trivalent Cr chemical conversion treatment was performed using a black trivalent
Cr conversion agent produced by Yuken Industry. The treatment was performed for 60
seconds in a plating bath of 40°C and pH 2.5 by using 60 ml/L of YFB-A3, 100 ml/L
of YFB-B3, and 60 ml/L of YFB-C3. As finishing treatment, the treatment was conducted
for 3 seconds in a plating bath of 40°C by using 200 ml/L of CR-U and 10 ml/L of CR-I.
[0064] A hull cell test (at a plating bath temperature of 40°C for 10 minutes at 1A) of
the test pieces of Example 1 and Comparative Example 4 which had been subjected to
each of YFA treatment and YFB treatment was performed and their appearance was studied.
Even after the YFA treatment or YFB treatment, the test piece of Example 1 showed
an appearance as good as that of Comparative Example 4, a conventional product.
1-2. Eclectic bath (NH4Cl-K, containing a surfactant other than cumylphenol one)
(Examples 5 to 6)
[0065] To the base solution A was added a plating bath applicable to high temperature (METASU
MZ-996A/GC: product of Yuken Industry). The resulting mixture was mixed with 2 g/L
of a 7 mole EO polyoxyethylene para-cumylphenyl ether sulfate, specifically potassium
salt as an anionic surfactant (Example 5). Separately, to the base solution A was
added a general bath (METASU ZB-627A/G: product of Yuken Industry). The resulting
mixture was mixed with 2 g/L of a 7 mole EO polyoxyethylene para-cumylphenyl ether
sulfate, specifically potassium salt as an anionic surfactant (Example 6).
[0066] As shown in Table 2, Example 5 and Example 6 using a cumylphenol surfactant have
a higher cloud point than that of Comparative Example 4 and Comparative Example 5,
respectively. This means that addition of a cumylphenol surfactant to a β-naphthol
type eclectic bath (ammonium/potassium bath) increases a cloud point. FIG. 3 shows
the results of the hull cell test. The results of the hull cell test have revealed
that Examples 5 and 6 containing a cumylphenol anionic surfactant provide a wider
bright surface and therefore show better results than those of Comparative Examples
4 and 5, respectively.
2-1. Eclectic bath (NH4Cl-Na)
(Example 7)
[0067] Next, a plating bath was prepared by mixing the basic solution B of Table 1 with
1 to 3 g/L of a 7 mole EO adduct of potassium polyoxyethylene para-cumylphenyl ether
sulfate as an anionic surfactant as shown in Table 4.
(Comparative Examples 6 to 8)
[0068] For comparison, plating baths were prepared by mixing the basic solution B of Table
1 with, as an anionic surfactant, from 1 to 3 g/L of the polyoxyethylene naphthyl
ether sulfate (Comparative Example 6), the polyoxyethylene oxypropylene naphthyl sulfate
(Comparative Example 7), and the polyoxyethylene oxypropylene naphthyl sulfonate (Comparative
Example 8), respectively, as shown in Table 4.
(Comparative Examples 9 and 10)
[0069] Further, as shown in Table 4, plating baths containing a β-naphthol anionic surfactant
were prepared. More specifically, the plating baths of Comparative Examples 9 and
10 were prepared by adding, to the basic solution B, a base agent A (MZ-996A in Comparative
Example 9 and ZB-627A in Comparative Example 10) and a brightener (GC in Comparative
Example 9 and G in Comparative Example 10) as needed (refer to Table 4 for the amount).
[0070] A decrease in the cloud point was observed in the plating bath containing sodium
chloride, compared with the plating bath containing potassium chloride, due to a difference
in solubility between K and N. As shown in Table 4, addition of a cumylphenol surfactant
however increases the cloud point even in the eclectic bath containing both ammonium
and sodium.
2-2. Eclectic bath (NH4Cl-Na, containing a surfactant other than a cumylphenol surfactant)
(Examples 8 and 9)
[0071] As shown in Table 4, to the basic solution B was added a plating bath for high bath
temperature (METASU MZ-996A/GC, product of Yuken Industry). The resulting mixture
was mixed with, as an anionic surfactant, 2 g/L of a 7 mole EO polyoxyethylene para-cumylphenyl
ether sulfate, specifically potassium salt (Example 8). Separately, to the basic solution
B was added a general bath (METASU ZB-627A/G: product of Yuken Industry). The resulting
mixture was mixed with, as an anionic surfactant, 2 g/L of a 7 mole EO polyoxyethylene
para-cumylphenyl ether sulfate, specifically potassium salt(Example 9).
[0072]
[Table 4]
|
Plating bath |
Cloud point |
|
Amount of
brightener |
Anionic surfactant |
Salt used |
|
Amount |
Examples 7 |
Basic solution. B |
|
K salt
7 moles of EO |
Polyoxyethylene para-cumylphenyl ether sulfate |
1 g/L |
|
60°C |
2 g/L |
Normal |
73°C |
3 g/L |
|
77°C |
Comp.Ex. 6 |
Basic solution B |
|
K shalt
13 moles of EO |
Polyoxyethylene naphthyl ether
sulfate |
1 g/L |
|
43°C |
2 g/L |
Normal |
45°C |
3 g/L |
|
48°C |
Comp. Ex. 7 |
Basic solution B |
|
Na salt
13 moles of EO & 3 moles of PO |
Polyoxyethylene oxypropylene naphthyl
sulfate |
1 g/L |
|
50°C |
2 g/L |
Normal |
52°C |
3 g/L |
|
55°C |
Comp. Ex. 8 |
Basic solution B |
|
K salt
13 moles of EO & 3 moles of PO |
Polyoxyethylene oxypropylene naphthyl
sulfonate |
1 g/L |
|
62°C |
2 g/L |
Normal |
65°C |
3 g/L |
|
66°C |
Comp. Ex. 9 |
Basic solution B
Plating bath for high bath temperature
METASU MZ-996A/GC |
MZ-996A: 20 mUL GC:0.5 mL/L |
|
|
|
63°C |
Comp. Ex. 10 |
Basic solution B
General bath
METASU ZB-627A/G |
ZB-627A: 30 mUL GC:1 mL/L |
|
|
|
43°C |
Example 8 |
Basic solution B
Plating bath for high bath temperature
METASU MZ-996A/GC |
MZ-996A: 20 mUL GC:0.5 mL/L |
K salt
7 moles of EO |
Polyoxyethylene para-cumylphenyl ether
sulfate |
2 g/L |
70°C |
Example 9 |
Basic solution B
General bath
METASU ZB-627A/G |
ZB-627A: 30 mUL GC:1 mL/L |
K salt
7 moles of EO |
Polyoxyethylene para-cumylphenyl ether
sulfate |
2 g/L |
65°C |
* METASU MZ-996A/GC: product of Yuken Industry
* METASU ZB-627A/GC: product of Yuken Industry |
[0073] As shown in Table 4, Examples 8 and 9 using a cumylphenol surfactant have a higher
cloud point than Comparative Examples. This means that addition of a cumylphenol surfactant
to a β-naphthol eclectic bath (containing both ammonium and sodium) increases the
cloud point. The results of the hull cell test are shown in FIG. 4. Comparative Examples
9 and 10 using the conventional brightener have a low cloud point. In particular,
a burnt deposit is wider at a high current portion in Comparative Example 10, while
Examples 8 and 9 show equal or better results compared with Comparative Examples.
3. Potassium chloride bath
(Example 10 and Comparative Example 11)
[0074] As shown in Table 5, to the basic solution C was added a plating bath for high bath
temperature (METASU FZ-300M/GR: product of Yuken Industry) (Comparative Example 11).
The resulting mixture was mixed with 2 g/L of a 7 mole EO polyoxyethylene para-cumylphenyl
ether sulfate, specifically potassium salt as an anionic surfactant (Example 10).
[0075]
[Table 5]
|
Plating bath |
Cloud point |
|
Amount of brightener |
Anionic surfactant |
Salt used |
|
Amount |
Comp. Ex. 11 |
Potassium plating bath (boric acid-free)
Base solution C
METASU FZ-300M/GR |
FZ-300M: 50 mL/L GR: 1.0 ml/L |
|
|
|
64°C |
Example 10 |
Potassium plating bath (boric acid-free)
Base solution C
METASUFZ-300M/GR |
FZ-300M: 50 mL/L GR: 1.0 ml/L |
K salt
7 moles of EO |
Polyoxyethylene paracumylphenyl ether sulfate |
2 g/L |
80°C |
Comp. Ex.12 |
Sodium plating bath
Basic solution D
METASU FZ-300M/GR |
FZ-300M: 50 mL/L GR: 1.0 ml/L |
|
|
|
58°C |
Example 11 |
Sodium plating bath
Basic solution D
METASU FZ-300M/GR |
FZ-300M: 50 mL/L GR: 1.0 ml/L |
K salt
7 moles of EO |
Polyoxyethylene paracumylphenyl ether sulfate |
2 g/L |
75°C |
Comp. Ex.13 |
Potassium plating bath (containing boric acid)
Basic solution E
METASU ZB-612A/GR |
ZB-612A: 30 mL/L GR: 1.0 ml/L |
|
|
|
40°C |
Example 12 |
Potassium plating bath (containing boric acid)
Basic solution E
METASU ZB-612A/GR |
ZB-612A: 30 mL/L GR: 1.0 ml/L |
K salt
7 moles of EO |
Polyoxyethylene paracumylphenyl ether sulfate |
2 g/L |
70°C |
Comp. Ex. 14 |
Plating bath
Basic solution F
METASU ZB-612A/GR |
ZB-612A: 30 mL/L GR: 1.0 ml/L |
|
|
|
30°C |
Example 13 |
Plating bath
Basic solution F
METASU ZB-612A/GR |
ZB-612A: 30 mL/L GR: 1.0 ml/L |
K salt
7 moles of EO |
Polyoxyethylene paracumylphenyl ether sulfate |
2 g/L |
60°C |
* METASU FZ-300M/GR: product of Yuken Industry
* METASU ZB-612A/GR: product of Yuken Industry |
[0076] Addition of a cumylphenol surfactant increased the cloud point of even a potassium
chloride bath. The results of the hull cell test are shown in FIG. 5. The results
of the hull cell test have revealed that Example 10 provides a wider bright surface
and thus shows better results than those of Comparative Example.
4. Sodium chloride bath
(Example 11 and Comparative Example 12)
[0077] As shown in Table 5, to the basic solution D was added a plating bath for high bath
temperature (METASU FZ-300M/GR: product of Yuken Industry) (Comparative Example 12).
The resulting mixture was mixed with, as an anionic surfactant, 2 g/L of a 7 mole
EO polyoxyethylene para-cumylphenyl ether sulfate, specifically potassium salt (Example
11).
[0078] Addition of a cumylphenol surfactant increased the cloud point of even a sodium chloride
bath. As shown in FIG. 5, the results of the hull cell test have revealed that Example
11 provides a wider bright surface and thus shows better results than those of Comparative
Example.
5. Potassium chloride bath (containing boric acid)
(Example 12 and Comparative Example 13)
[0079] As shown in Table 5, to the basic solution E was added a plating bath for high bath
temperature (METASU ZB-612A/GR: product of Yuken Industry) (Comparative Example 13).
The resulting mixture was mixed with, as an anionic surfactant, 2 g/L of a 7 mole
EO polyoxyethylene para-cumylphenyl ether sulfate, specifically potassium salt (Example
12). The plating baths of Example 12 and Comparative Example 13 each contains boric
acid.
[0080] Addition of a cumylphenol surfactant increased the cloud point of even a boric-acid
containing potassium chloride bath. The results of the hull cell test are shown in
FIG. 6. As a result of the hull cell test, the plating bath of Example 12 has comparable
results to that of Comparative Example.
6. Sodium chloride bath (containing boric acid)
(Example 13 and Comparative Example 14)
[0081] As shown in Table 5, to the basic solution F was added a plating bath for high bath
temperature (METASU ZB-612A/GR: product of Yuken Industry) (Comparative Example 14).
The resulting mixture was mixed with, as an anionic surfactant, 2 g/L of a 7 mole
EO polyoxyethylene para-cumylphenyl ether sulfate, specifically potassium salt (Example
13). Example 13 and Comparative Example 14 each contains boric acid.
[0082] Addition of a cumylphenol surfactant increased the cloud point of even a boric-acid
containing sodium chloride bath. As shown in FIG. 6, when the hull cell test was performed,
the plating bath of Example 13 has comparable results to that of Comparative Example.
7-1. Ammonium chloride bath
(Example 14 and Comparative Examples 15 to 18)
[0083] As shown in Table 6, the basic solution G was mixed with, as an anionic surfactant,
from 1 to 3 g/L of a 7 mole EO polyoxyethylene para-cumylphenyl ether sulfate, specifically
potassium salt (Example 14). The basic solution G was mixed with, as an anionic surfactant,
from 1 to 3 g/L of the polyoxyethylene naphthyl ether sulfate (Comparative Example
15). Further, the basic solution G was mixed with METASU MZ-996A/GC (Comparative Example
16), METASU ZB-627A/G (Comparative Example 17), and a brightener component (Comparative
Example 18), respectively.
[0084]
[Table 6]
|
Plating bath |
Cloud point |
|
Amount of brightener |
Anionic surfactant |
Salt used |
|
Amount |
Example 14 |
Basic solution G |
|
K salt
7 moles of EO |
Polyoxyethylene para-cumylphenyl ether sulfate |
1 g/L |
|
65°C |
2 g/L |
Normal |
75°C |
3 g/L |
|
80°C |
Comp. Ex. 15 |
Basic solution G |
|
K salt
13 moles of EO |
Polyoxyethylene naphthyl ether sulfate |
1 g/L |
|
43°C |
2 g/L |
Normal |
47°C |
3 g/L |
|
50°C |
Comp. Ex. 16 |
Basic solution G Plating bath for high bath temperature METASU MZ-996A/GC |
MZ-996A: 20 mUL GC:0.5 mL/L |
|
|
|
65°C |
Comp. Ex. 17 |
Basic solution G General bath METASU ZB-627A/G |
B-627A: 30 mL G: 1 mL/L |
|
|
|
45°C |
Comp. Ex. 18 |
Basic solution G Brightener component added |
Predetermined amount |
|
|
|
40°C |
Example 15 |
Basic solution G Plating bath for high bath temperature METASU 996A/GC |
MZ-996A: 20 mUL GC:0.5 mL/L |
K salt
7 moles of EO |
Polyoxyethylene para-cumylphenyl ether sulfate |
2 g/L |
72°C |
Example 16 |
Basic solution G General bath METASU ZB-627A/G |
B-627A: 30 mL G:1 mL/L |
K salt
7 moles of EO |
Polyoxyethylene para-cumylphenyl ether sulfate |
2 g/L |
70°C |
* METASU MZ-996A/GC: product of Yuken Industry
* METASU ZB-627A/GC: product of Yuken Industry |
[0085] Addition of a cumylphenol surfactant increased the cloud point of even an ammonium
chloride bath.
7-2. Ammonium chloride bath (containing a surfactant other than cumylphenol one)
(Examples 15 and 16)
[0086] As shown in Table 6, to the basic solution G was added a plating bath for high bath
temperature (METASU MZ-996A/GC; product of Yuken Industry). The resulting mixture
was mixed with, as an anionic surfactant, 2 g/L of a 7 mole EO polyoxyethylene para-cumylphenyl
ether sulfate, specifically potassium salt (Example 15). Separately, to the basic
solution G was added a general bath (METASU ZB-627A/G; product of Yuken Industry).
The resulting mixture was mixed with, as an anionic surfactant, 2 g/L of a 7 mole
EO polyoxyethylene para-cumylphenyl ether sulfate, specifically potassium salt (Example
16).
[0087] As shown in Table 6, Examples 15 and 16 using a cumylphenol surfactant have a higher
cloud point than that of Comparative Examples. The results of the hull cell test are
shown in FIG. 7. The hull cell test has revealed that Examples 15 and 16 provide a
wider bright surface and thus show better results than those of Comparative Examples.
[0088] Using a cumylphenol surfactant has higher solubility/dispersibility of the components
compared with a conventional product so that it is improved in the turbidity and precipitation
of the plating solution. Also addition of a cumylphenol surfactant to a conventional
product containing a β-naphthol surfactant has also succeeded in improvement in turbidity
and precipitate of the plating solution. A high temperature bath is commonly used
at from 30 to 50°C, but addition of a cumylphenol surfactant increases the cloud point,
which enables good plating treatment even in a high temperature bath. In addition,
this increases the solubility of a brightener component so that a bright appearance
can be obtained. Even in a chemical conversion treatment, the bright appearance can
be maintained.
[0089] As described above, it is possible to resolve the conventional problem and provide
a plating bath which can be used stably because there is less change in the brightener
due to high temperature treatment, that is, current supply for plating. This means
that an acidic zinc plating bath containing a cumylphenol surfactant can keep a high
cloud point and keep its performance even against aging due to current supply.
Industrial Applicability
[0090] The acidic zinc plating bath of the present invention can be used as an acidic bath
for zinc plating of bolts, nuts, and the like.
Description of Reference Numerals
[0091] 1: Plated surface, 2: Cloudiness, 3: Burnt deposit, 4: Severe burnt deposit, 5: Bright
surface, 6: Solution level