U.S. patent application number 16/771066 was filed with the patent office on 2021-07-01 for trivalent chromium plating solution and trivalent chromium plating method using same.
This patent application is currently assigned to JCU CORPORATION. The applicant listed for this patent is JCU CORPORATION. Invention is credited to Masao HORI, Yuto MORIKAWA, Madoka NAKAGAMI.
Application Number | 20210198797 16/771066 |
Document ID | / |
Family ID | 1000005477029 |
Filed Date | 2021-07-01 |
United States Patent
Application |
20210198797 |
Kind Code |
A1 |
MORIKAWA; Yuto ; et
al. |
July 1, 2021 |
TRIVALENT CHROMIUM PLATING SOLUTION AND TRIVALENT CHROMIUM PLATING
METHOD USING SAME
Abstract
A trivalent chromium plating solution that does not cause the
problems including the occurrence of deposition failure of the
plating and color unevenness, such as a brown stripe pattern, in
the plating even though a metal impurity is incorporated into the
plating solution, and a trivalent chromium plating method are
provided by a trivalent chromium plating solution containing a
trivalent chromium compound, a chloride as a conductive salt, a pH
buffering agent, and a complexing agent, further containing an
unsaturated sulfonic acid compound represented by the following
general formula (1) (wherein in the formula (1), R.sub.1 represents
a hydrocarbon group having a number of carbon atoms of from 1 to
10, hydrogen, or a halogen; R.sub.2 represents nothing or a
hydrocarbon group having a number of carbon atoms of from 1 to 10;
and X represents hydrogen or an alkali metal), and a trivalent
chromium plating method using the same.
R.sub.1--CH.dbd.CH--R.sub.2--SO.sub.3X (1)
Inventors: |
MORIKAWA; Yuto;
(Kawasaki-shi, JP) ; HORI; Masao; (Wixom, MI)
; NAKAGAMI; Madoka; (Kawasaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JCU CORPORATION |
Taito-ku |
|
JP |
|
|
Assignee: |
JCU CORPORATION
Taito-ku
JP
|
Family ID: |
1000005477029 |
Appl. No.: |
16/771066 |
Filed: |
December 13, 2018 |
PCT Filed: |
December 13, 2018 |
PCT NO: |
PCT/JP2018/045799 |
371 Date: |
June 9, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 3/06 20130101 |
International
Class: |
C25D 3/06 20060101
C25D003/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2017 |
JP |
2017-239216 |
Jun 26, 2018 |
JP |
2018-121196 |
Claims
1. A trivalent chromium plating solution, comprising: a trivalent
chromium compound, a chloride as a conductive salt, a pH buffering
agent, a complexing agent, and an unsaturated sulfonic acid
compound of formula (1): R.sub.1--CH.dbd.CH--R.sub.2--SO.sub.3X (1)
wherein R.sub.1 represents a hydrocarbon group having a number of
carbon atoms of from 1 to 10, hydrogen, or a halogen; R.sub.2
represents nothing or a hydrocarbon group having a number of carbon
atoms of from 1 to 10; and X represents hydrogen or an alkali
metal.
2. The trivalent chromium plating solution according to claim 1,
wherein the unsaturated sulfonic acid compound is at least one
selected from the group consisting of sodium vinylsulfonate, sodium
allylsulfonate, sodium p-styrenesulfonate, and sodium
.beta.-styrenesulfonate.
3. The trivalent chromium plating solution according to claim 1,
wherein the chloride is at least one selected from the group
consisting of potassium chloride, ammonium chloride, and sodium
chloride.
4. The trivalent chromium plating solution according to claim 1,
further comprising: a metal impurity.
5. The trivalent chromium plating solution according to claim 1,
further comprising: nickel.
6. The trivalent chromium plating solution according to claim 1,
wherein the trivalent chromium plating solution comprises
substantially no iron and/or cobalt.
7. A trivalent chromium plating method, comprising: electroplating
an article with the trivalent chromium plating solution according
to claim 1.
8. A method for enhancing resistance of a trivalent chromium
plating solution against metal impurities contained in the
trivalent chromium plating solution, the method comprising: adding
an unsaturated sulfonic acid compound in the trivalent chromium
plating solution, wherein the trivalent chromium plating solution
comprises a trivalent chromium compound, a chloride as a conductive
salt, a pH buffering agent, and a complexing agent, and the
unsaturated sulfonic acid compound is a compound of formula (1):
R.sub.1--CH.dbd.CH--R.sub.2--SO.sub.3X (1) wherein R.sub.1
represents a hydrocarbon group having a number of carbon atoms of
from 1 to 10, hydrogen, or a halogen; R.sub.2 represents nothing or
a hydrocarbon group having a number of carbon atoms of from 1 to
10; and X represents hydrogen or an alkali metal.
9. A method for preventing burnt deposit in a high current density
in plating with a trivalent chromium plating solution, the method
comprising: adding an unsaturated sulfonic acid and nickel in the
trivalent chromium plating solution, wherein the trivalent chromium
plating solution comprises a trivalent chromium compound, a
chloride as a conductive salt, a pH buffering agent, and a
complexing agent, and the unsaturated sulfonic acid compound is a
compound of formula (1): R.sub.1--CH.dbd.CH--R.sub.2--SO.sub.3X (1)
wherein R.sub.1 represents a hydrocarbon group having a number of
carbon atoms of from 1 to 10, hydrogen, or a halogen; R.sub.2
represents nothing or a hydrocarbon group having a number of carbon
atoms of from 1 to 10; and X represents hydrogen or an alkali
metal.
10. A chromium-plated product comprising: an article, electroplated
with the trivalent chromium plating solution according to claim
1.
11. The chromium-plated product according to claim 10, wherein the
chromium plating comprises substantially no iron and/or cobalt.
Description
TECHNICAL FIELD
[0001] The present invention relates to a trivalent chromium
plating solution and a trivalent chromium plating method using the
same.
BACKGROUND ART
[0002] Chromium plating is used as a coating film for decoration
owing to the silvery white color thereof. Hexavalent chromium has
been used for the chromium plating, but the use of hexavalent
chromium is restricted in recent years due to the environmental
implications thereof, and the technology is shifted to the use of
trivalent chromium.
[0003] Many reports have been made for the technique using
trivalent chromium by various manufacturers (see, for example, PTL
1).
[0004] However, the trivalent chromium plating solution has
problems including the occurrence of deposition failure of the
plating and color unevenness, such as a brown stripe pattern, in
the plating caused by the incorporation of metal impurities derived
from the first plating and the chemicals and the like associated
with the plating.
CITATION LIST
Patent Literature
[0005] PTL 1: JP-A-2009-74170
SUMMARY OF INVENTION
Technical Problem
[0006] An object of the present invention is to provide a trivalent
chromium plating solution that does not cause the problems
including the occurrence of deposition failure of the plating and
color unevenness, such as a brown stripe pattern, in the plating
even though metal impurities are incorporated into the plating
solution.
Solution to Problem
[0007] As a result of the earnest investigations by the present
inventors, it has been found that the problems including the
occurrence of deposition failure of the plating and color
unevenness, such as a brown stripe pattern, in the plating can be
prevented from occurring even through metal impurities are
incorporated into the plating solution, by using an unsaturated
sulfonic acid compound having a particular structure contained in a
trivalent chromium plating solution containing a chloride as a
conductive salt, and thus the present invention has been completed.
Furthermore, it has also been found that not only the
aforementioned problems, but also burnt deposit in a high current
density in plating can be prevented from occurring, by positively
using nickel as a metal impurity contained in the trivalent
chromium plating solution, and thus the present invention has been
completed.
[0008] Accordingly, the present invention relates to a trivalent
chromium plating solution containing a trivalent chromium compound,
a chloride as a conductive salt, a pH buffering agent, and a
complexing agent, further containing an unsaturated sulfonic acid
compound represented by the following general formula (1):
R.sub.1--CH.dbd.CH--R.sub.2--SO.sub.3X (1)
wherein in the formula (1), R.sub.1 represents a hydrocarbon group
having a number of carbon atoms of from 1 to 10, hydrogen, or a
halogen; R.sub.2 represents nothing or a hydrocarbon group having a
number of carbon atoms of from 1 to 10; and X represents hydrogen
or an alkali metal.
[0009] The present invention also relates to a trivalent chromium
plating method including electroplating an article to be plated
with the trivalent chromium plating solution.
[0010] The present invention further relates to a method for
enhancing resistance of a trivalent chromium plating solution
containing a trivalent chromium compound, a chloride as a
conductive salt, a pH buffering agent, and a complexing agent,
against metal impurities contained, including using an unsaturated
sulfonic acid compound represented by the following general formula
(1):
R.sub.1--CH.dbd.CH--R.sub.2--SO.sub.3X (1)
wherein in the formula (1), R.sub.1 represents a hydrocarbon group
having a number of carbon atoms of from 1 to 10, hydrogen, or a
halogen; R.sub.2 represents nothing or a hydrocarbon group having a
number of carbon atoms of from 1 to 10; and X represents hydrogen
or an alkali metal, further contained in the trivalent chromium
plating solution.
[0011] The present invention still further relates to a method for
preventing burnt deposit in a high current density in plating with
a trivalent chromium plating solution containing a trivalent
chromium compound, a chloride as a conductive salt, a pH buffering
agent, and a complexing agent, including using an unsaturated
sulfonic acid compound represented by the following general formula
(1), and nickel:
R.sub.1--CH.dbd.CH--R.sub.2--SO.sub.3X (1)
wherein in the formula (1), R.sub.1 represents a hydrocarbon group
having a number of carbon atoms of from 1 to 10, hydrogen, or a
halogen; R.sub.2 represents nothing or a hydrocarbon group having a
number of carbon atoms of from 1 to 10; and X represents hydrogen
or an alkali metal, further contained in the trivalent chromium
plating solution.
[0012] The present invention still more further relates to a
chromium-plated product including an article to be plated,
electroplated with the trivalent chromium plating solution.
Advantageous Effects of Invention
[0013] The trivalent chromium plating solution of the present
invention is an excellent one that does not cause the problems
including the occurrence of deposition failure of the plating and
color unevenness, such as a brown stripe pattern, in the plating
even through metal impurities are incorporated into the plating
solution.
[0014] Furthermore, not only the aforementioned problems, but also
burnt deposit in a high current density in plating can be prevented
from occurring by positively using nickel as a metal impurity
contained in the trivalent chromium plating solution of the present
invention.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 is an illustration showing the position where the
throwing distance is measured in the Hull cell test of Example
1.
[0016] FIG. 2 is an image showing the Hull cell appearance of the
nickel-plated brass plate (with burnt deposit) after plating with
the plating solution having no nickel added in Example 4.
[0017] FIG. 3 is an image showing the Hull cell appearance of the
nickel-plated brass plate (without burnt deposit) after plating
with the plating solution having 10 ppm of nickel added in Example
4.
DESCRIPTION OF EMBODIMENTS
[0018] The trivalent chromium plating solution of the present
invention (which may be hereinafter referred to as a "plating
solution of the present invention") is a trivalent chromium plating
solution that contains a trivalent chromium compound, a chloride as
a conductive salt, a pH buffering agent, and a complexing agent,
and further contains an unsaturated sulfonic acid compound
represented by the following general formula (1).
R.sub.1--CH.dbd.CH--R.sub.2--SO.sub.3X (1)
[0019] In the formula (1), R.sub.1 represents a hydrocarbon group
having a number of carbon atoms of from 1 to 10, hydrogen, or a
halogen; R.sub.2 represents nothing or a hydrocarbon group having a
number of carbon atoms of from 1 to 10; and X represents hydrogen
or an alkali metal, and it is preferred that R.sub.1 represents a
hydrocarbon group having a number of carbon atoms of from 1 to 6 or
hydrogen; R.sub.2 represents nothing or a hydrocarbon group having
a number of carbon atoms of from 1 to 6; and X represents hydrogen,
sodium, or potassium. Specific examples of the unsaturated sulfonic
acid compound represented by the formula (1) include sodium
vinylsulfonate, sodium allylsulfonate, sodium p-styrenesulfonate,
and sodium .beta.-styrenesulfonate. The unsaturated sulfonic acid
compound may be used alone or as a combination of two or more kinds
thereof. The content of the unsaturated sulfonic acid compound in
the plating solution of the present invention is not particularly
limited, and for example, is from 0.01 to 20 g/L, and preferably
from 0.1 to 5 g/L.
[0020] The trivalent chromium compound used in the plating solution
of the present invention is not particularly limited, examples of
which include basic chromium sulfate, chromium sulfate, chromium
chloride, chromium sulfamate, and chromium acetate, and basic
chromium sulfate, chromium sulfate, and chromium chloride are
preferred. The trivalent chromium compound may be used alone or as
a combination of two or more kinds thereof. The content of the
trivalent chromium compound in the plating solution of the present
invention is not particularly limited, and for example, is from 1
to 20 g/L, and preferably from 5 to 15 g/L, in terms of metallic
chromium.
[0021] The conductive salt used in the plating solution of the
present invention is a chloride. The kind of the chloride is not
particularly limited, examples of which include potassium chloride,
ammonium chloride, and sodium chloride. The chloride may be used
alone or as a combination of two or more kinds thereof. The content
of the chloride in the plating solution of the present invention is
not particularly limited, and for example, is from 150 to 400 g/L,
and preferably from 200 to 350 g/L.
[0022] The pH buffering agent used in the plating solution of the
present invention is not particularly limited, examples of which
include boric acid, sodium borate, potassium borate, phosphoric
acid, and dipotassium hydrogen phosphate, and boric acid and sodium
borate are preferred. The pH buffering agent may be used alone or
as a combination of two or more kinds thereof. The content of the
pH buffering agent in the plating solution of the present invention
is not particularly limited, and for example, is from 10 to 150
g/L, and preferably from 50 to 100 g/L.
[0023] The complexing agent used in the plating solution of the
present invention is not particularly limited, examples of which
include formic acid, ammonium formate, potassium formate, citric
acid, and triammonium citrate. Among these, ammonium formate and
triammonium citrate are preferred. The complexing agent may be used
alone or as a combination of two or more kinds thereof. The content
of the complexing agent in the plating solution of the present
invention is not particularly limited, and for example, is from 0.3
to 2 times by mol, and preferably from 0.8 to 1.5 times by mol, the
metallic chromium concentration.
[0024] The plating solution of the present invention may further
contain ammonium bromide, potassium bromide, and the like.
[0025] The pH of the plating solution of the present invention is
not particularly limited, as far as the solution is acidic, and for
example, is preferably from 2 to 4, and more preferably from 2.5 to
3.5.
[0026] The preparation method of the plating solution of the
present invention is not particularly limited, and for example, the
solution can be prepared by adding and mixing the trivalent
chromium compound, the chloride salt, the pH buffering agent, the
complexing agent, and the unsaturated sulfonic acid compound with
water at from 40 to 50.degree. C., adding and mixing the other
components therewith depending on necessity, and controlling the pH
thereof.
[0027] The plating solution of the present invention does not cause
the problems including the occurrence of deposition failure of the
plating and color unevenness, such as a brown stripe pattern, in
the plating even though metal impurities are contained therein
(i.e., has resistance against metal impurities). In particular, the
plating solution of the present invention does not cause the
problems even though a large amount of metal impurities are
contained in a concentration of approximately several hundred ppm
during the long-term use or suddenly. The metal impurities herein
are metals derived from the first plating and the chemicals and the
like associated with the plating. Specific examples of the metals
include nickel, zinc, copper, and hexavalent chromium, and
preferably include nickel and copper, which are frequently used as
the first plating.
[0028] In the case where the plating solution of the present
invention positively uses nickel as a metal impurity contained
therein, burnt deposit in a high current density in plating can be
prevented from occurring. The high current density herein means
portions where the current is concentrated, such as a corner part
and an apex part of an article. Nickel that can be used in the
plating solution of the present invention is not particularly
limited, and examples thereof include a nickel salt, such as nickel
chloride and nickel sulfate. The content of nickel in the plating
solution of the present invention is not particularly limited, and
for example, is from 10 to 500 ppm, preferably from 15 to 200 ppm,
and more preferably from 20 to 100 ppm.
[0029] Nickel can prevent burnt deposit in a high current density
from occurring also in plating with a trivalent chromium plating
solution containing a trivalent chromium compound, a chloride as a
conductive salt, a pH buffering agent, and a complexing agent,
obtained by excluding the unsaturated sulfonic acid compound
represented by the general formula (1) from the plating solution of
the present invention, at the same concentration. The kinds and the
concentrations of the trivalent chromium compound, the chloride,
the pH buffering agent, and the complexing agent may be the same as
in the plating solution of the present invention.
[0030] An ordinary trivalent chromium plating solution contains
iron or cobalt for the enhancement of the throwing power for a low
current density, but the plating solution of the present invention
can have enhanced throwing power without the addition of iron
and/or cobalt. A plating solution containing iron or cobalt has a
tendency that the corrosion resistance of the plating film is
decreased due to codeposition of iron or cobalt therein.
Accordingly, it is preferred that the plating solution of the
present invention contains substantially no iron and/or cobalt. The
plating solution of the present invention that contains
substantially no iron and/or cobalt means that the content of iron
and/or cobalt is 2 ppm or less, preferably 1 ppm or less, and more
preferably 0.5 ppm or less. The amount of iron and/or cobalt can be
analyzed by the ICP-MS method, the atomic absorption spectrometry,
or the like.
[0031] Chromium plating can be formed on an article to be plated by
electroplating the article to be plated with the plating solution
of the present invention in the same manner as for the ordinary
chromium plating solution.
[0032] The condition of the electroplating is not particularly
limited, and for example, the electroplating may be performed at a
bath temperature of from 25 to 45.degree. C., with carbon or
iridium oxide as an anode, at a cathode current density of from 4
to 20 A/dm.sup.2, for a period of from 1 to 15 minutes.
[0033] Examples of the article to be plated capable of being
electroplated include a metal, such as iron, stainless steel, and
brass, and a resin, such as ABS and PC/ABS. The article to be
plated may be subjected to a treatment, such as copper plating and
nickel plating, in advance before the treatment with the plating
solution of the present invention.
[0034] The chromium plating thus obtained becomes chromium plating
having an appearance, throwing power, and a deposition rate that
are equivalent to the use of hexavalent chromium. The unsaturated
sulfonic acid compound represented by the formula (1) can suppress
the color tone of the resulting chromium plating from becoming
dark, as compared to other unsaturated sulfonic acid compounds.
Accordingly, the chromium-plated product is favorably applied to
automobile exterior components, such as a door handle and an
emblem, and components of an accessory, a faucet, a tool, and the
like.
[0035] In the case where the plating solution of the present
invention contains substantially no iron and/or cobalt, the
resulting chromium-plated product also contains substantially no
iron and/or cobalt. The chromium-plated product of the present
invention that contains substantially no iron and/or cobalt means
that the content of iron and/or chromium in the chromium plating is
less than 0.5% by atom, and preferably 0.3% by atom or less. The
amount of iron and/or cobalt can be analyzed by EDS, XPS, or the
like.
EXAMPLES
[0036] The present invention will be described in detail with
reference to examples and comparative examples below, but the
present invention is not limited to the examples.
Example 1
Chromium Plating
[0037] The compounds shown in the following basic formulation and
Table 1 each were dissolved in water to prepare a trivalent
chromium plating solution. The trivalent chromium plating solution
was subjected to the Hull cell test using a brass plate having
nickel plating formed thereon. The condition of the Hull cell test
was a current of 5 A and a plating time of 3 minutes. After
plating, the distance of the deposition of the plating film from
the left end of the brass plate was measured as shown in FIG. 1,
and the throwing power decreasing rate was calculated in the manner
described later. The color tone and the appearance were evaluated
in the manners described later. The color tone after plating was
evaluated in terms of the L* value with a color-difference meter
(produced by Konica Minolta, Inc.). The results are shown in Table
1.
<Basic Formulation 1>
TABLE-US-00001 [0038] Basic chromium sulfate 64 g/L Ammonium
formate 16 g/L Potassium chloride 165 g/L Ammonium chloride 100 g/L
Ammonium bromide 6 g/L Boric acid 67 g/L
<Basic Formulation 2>
TABLE-US-00002 [0039] Basic chromium sulfate 64 g/L Ammonium
formate 16 g/L Sodium chloride 75 g/L Potassium chloride 165 g/L
Ammonium chloride 100 g/L Ammonium bromide 6 g/L Boric acid 67
g/L
<Basic Formulation 3>
TABLE-US-00003 [0040] Basic chromium sulfate 64 g/L Ammonium
tartarate 30 g/L Potassium sulfate 150 g/L Ammonium sulfate 20 g/L
Boric acid 80 g/L
TABLE-US-00004 TABLE 1 Throwing power Basic Addition Evaluation of
Evaluation of decreasing rate formulation Compound concentration L*
color tone appearance (%) Example 1 Na vinylsulfonate 25% aqueous
solution 1 mL/L 79.54 good good 0.70 product 1 Na vinylsulfonate
25% aqueous solution 5 mL/L 79.52 good good 1.41 1 Na
allylsulfonate 36% aqueous solution 0.5 mL/L 78.39 good good not
decreased 1 Na p-styrenesulfonate 1.5 g/L 79.23 good good not
decreased 2 Na .beta.-styrenesulfonate 1.0 g/L 79.61 good good 0.70
2 Na vinylsulfonate 25% aqueous solution 1 mL/L 79.48 good good not
decreased Comparative 1 not added -- 78.63 good good 0 (standard)
product 1 Na 2-propine-1-sulfonate 20% aqueous 0.1 mL/L 73.69 poor
good 11.27 solution 1 thiodiglycolic acid 1.0 g/L 76.77 poor good
5.63 1 thiourea 30 mg/L 75.70 poor good 7.75 1 1-allyl-2-thiourea
50 mg/L 75.60 poor good 1.41 1 Na 3-mercapto-1-propanesulfonate 50
mg/L 77.22 poor good 2.11 1 Na 2-hydroxyethanesulfonate 20% 20 mL/L
79.04 good good 1.41 aqueous solution 1 Na saccharate dihydrate 50
mg/L 77.66 poor good 1.41 2 not added -- 78.87 good good 0
(standard) 3 not added -- 79.68 good good 0 (standard) 3 Na
allylsulfonate 36% aqueous solution 1.5 mL/L 80.38 good good not
decreased 3 Na vinylsulfonate 25% aqueous solution 1.0 mL/L 73.47
poor good not decreased
<Calculation Method of Throwing Power Decreasing Rate>
[0041] (decreasing rate (%))=((standard value-test
value))/(standard value).times.100
[0042] In the expression, the standard value is a value of throwing
power with no compound added, and the test value is the measured
value in the test under the condition. The values of the standard
value are 71 mm for the basic formulation 1, 73 mm for the basic
formulation 2, and 74 mm for the basic formulation 3.
<Evaluation of Color Tone>
(Evaluation) (Content)
[0043] good: L* of 78 or more
[0044] poor: L* of less than 78
<Evaluation of Appearance>
[0045] good: uniform appearance and no uneven pattern
[0046] poor: uneven appearance or uneven pattern
[0047] It was found from the results that the unsaturated sulfonic
acid compound contained in the plating solution of the present
invention was not a substance that the use thereof deteriorated the
color tone, the appearance, and the throwing power of the chromium
plating.
[0048] The contents of iron and cobalt in the trivalent chromium
plating solutions each were less than 0.5 ppm, as measured by the
ICP-MS method. The contents of iron and cobalt in the resulting
chromium plating each were less than 0.3% by atom, as measured by
the EDS elemental analysis.
Example 2
Chromium Plating in Presence of Impurity
[0049] A trivalent chromium plating solution was prepared in the
same manner as in Example 1 except that a Watts solution was added
in an amount that provided 100 ppm of nickel as a metal impurity.
The trivalent chromium plating solution was subjected to the same
test as in Example 1. The results are shown in Table 2.
TABLE-US-00005 TABLE 2 Throwing power Basic Addition Evaluation of
Evaluation of decreasing rate formulation Compound concentration L*
color tone appearance (%) Note Example 1 Na vinylsulfonate 25% 1
mL/L 78.97 good good 4.93 -- product aqueous solution 1 Na
vinylsulfonate 25% 5 mL/L 79.83 good good 4.23 -- aqueous solution
1 Na allylsulfonate 36% 0.5 mL/L 78.04 good good 1.41 -- aqueous
solution 1 Na p-styrenesulfonate 1.5 g/L 79.01 good good 3.52 -- 2
Na .beta.-styrenesulfonate 1.0 g/L 79.22 good good 2.82 -- 2 Na
vinylsulfonate 25% 1 mL/L 78.99 good good 4.23 -- aqueous solution
Comparative 1 not added -- 77.81 poor poor 6.34 brown stripe
product pattern 1 Na 2-propine-1-sulfonate 0.1 mL/L * poor poor --
mostly 20% aqueous solution deposition failure 1 thiodiglycolic
acid 1.0 g/L 76.48 poor good 7.75 -- 1 thiourea 30 mg/L 75.3 poor
good 11.27 -- 1 1-allyl-2-thiourea 50 mg/L 76.08 poor good 4.23 --
1 Na 3-mercapto-1- 50 mg/L 77.54 poor good 5.63 -- propanesulfonate
1 Na 2-hydroxyethanesulfonate 20 mL/L 78.53 poor poor 7.75 -- 20%
aqueous solution 1 Na saccharate dihydrate 50 mg/L 73.67 poor poor
9.86 brown stripe pattern 2 not added -- 77.59 poor poor 6.85 brown
stripe pattern 3 not added -- * * * 50% or more mostly deposition
failure 3 Na allylsulfonate 36% 1.5 mL/L * * * 50% or more mostly
aqueous solution deposition failure 3 Na vinylsulfonate 25% 1.0
mL/L * * * 50% or more mostly aqueous solution deposition failure *
unmeasurable or unevaluable
[0050] It was found that the plating capability of the trivalent
chromium plating solution of the present invention (i.e., the
example product), which was a chloride bath and contained the
unsaturated sulfonic acid compound having the particular structure,
was not influenced by 100 ppm of nickel contained as a metal
impurity in the plating solution. It was also found that
irrespective of the same trivalent chromium plating solution, the
sulfuric acid bath (i.e., the comparative product having the basic
formulation 3) had no resistance against metal impurities even
though the unsaturated sulfonic acid compound having the particular
structure was contained. It was further found that irrespective of
the chloride bath, in the case where the particular structure was
not used, the plating capability was influenced by 100 ppm of
nickel contained as a metal impurity in the plating solution.
[0051] The contents of iron and cobalt in the trivalent chromium
plating solutions each were less than 0.5 ppm, as measured by the
ICP-MS method. The contents of iron and cobalt in the resulting
chromium plating each were less than 0.3% by atom, as measured by
the EDS elemental analysis.
Example 3
Chromium Plating in Presence of Impurity
[0052] A trivalent chromium plating solution containing the
compounds shown in the basic formulation 1 used in Example 1 and
the Table 3 below, and a copper chloride aqueous solution in an
amount that provided 20 ppm of copper as a metal impurity was
prepared. The trivalent chromium plating solution was subjected to
the same test as in Example 1. The results are shown in Table 3.
For comparison, a trivalent chromium plating solution containing no
unsaturated sulfonic acid compound having the particular structure
was subjected to the same test. The results are also shown in Table
3.
TABLE-US-00006 TABLE 3 Throwing power Basic Addition Evaluation of
Evaluation of decreasing rate formulation Compound concentration L*
color tone appearance (%) Note Example 1 Na vinylsulfonate 25% 2
mL/L 79.39 good good 0.47 -- product aqueous solution Comparative 1
not added -- 79.14 good poor 2.82 white pattern product
[0053] It was found that the plating capability of the trivalent
chromium plating solution of the present invention (i.e., the
example product) was not influenced by 20 ppm of copper contained
as a metal impurity in the plating solution.
[0054] The contents of iron and cobalt in the trivalent chromium
plating solutions each were less than 0.5 ppm, as measured by the
ICP-MS method. The contents of iron and cobalt in the resulting
chromium plating each were less than 0.3% by atom, as measured by
the EDS elemental analysis.
Example 4
Chromium Plating
[0055] The compounds shown in the following basic formulation 4, a
sodium vinylsulfonate 25% aqueous solution, and nickel (added in
the form of nickel chloride) were dissolved in water in the
concentrations shown in Table 4 to prepare a trivalent chromium
plating solution. The trivalent chromium plating solution was
subjected to the Hull cell test using a brass plate having nickel
plating formed thereon. The condition of the Hull cell test was a
current of 5 A and a plating time of 3 minutes. The trivalent
chromium plating solution was subjected to the same test as in
Example 1. The presence of burnt deposit in a high current density
(which was the left end portion in FIG. 1) was visually evaluated.
The results are shown in Table 4. For showing an example of the
presence of burnt deposit, the brass plate after plating with a
plating solution containing no nickel (with burnt deposit) is shown
in FIG. 2, and the appearance of the brass plate after plating with
a plating solution containing 10 ppm of nickel (without burnt
deposit) is shown in FIG. 3.
<Basic Formulation 4>
TABLE-US-00007 [0056] Basic chromium sulfate 64 g/L Ammonium
formate 16 g/L Sodium chloride 70 g/L Potassium chloride 140 g/L
Ammonium chloride 85 g/L Ammonium bromide 6 g/L Boric acid 67
g/L
TABLE-US-00008 TABLE 4 Basic Na vinylsulfonate 25% Evaluation of
Evaluation of Burnt deposit in high formulation aqueous solution
Nickel L* color tone appearance current density Example 4 3 mL/L 10
ppm 79.57 good good none product 4 3 mL/L 30 ppm 80.42 good good
none 4 3 mL/L 50 ppm 80.28 good good none 4 5 mL/L 300 ppm 79.91
good good none 4 5 mL/L 500 ppm 79.57 good good none Comparative 4
3 mL/L 0 ppm 80.27 good good found product
[0057] It was found that burnt deposit in a high current density in
plating was prevented from occurring, by positively using nickel as
a metal impurity contained in the trivalent chromium plating
solution of the present invention (i.e., the example product).
[0058] The contents of iron and cobalt in the trivalent chromium
plating solutions each were less than 0.5 ppm, as measured by the
ICP-MS method. The contents of iron and cobalt in the resulting
chromium plating each were less than 0.3% by atom, as measured by
the EDS elemental analysis.
Reference Example 1
Chromium Plating
[0059] To a plating solution having the basic formulation 4, a
sodium vinylsulfonate 25% aqueous solution was not added, but
nickel was added in an amount of 0, 10, 30, or 50 ppm, so as to
prepare a trivalent chromium plating solution. The trivalent
chromium plating solution was subjected to the Hull cell test using
a brass plate having nickel plating formed thereon. The condition
of the Hull cell test was a current of 5 A and a plating time of 3
minutes. The trivalent chromium plating solution was subjected to
the same test as in Example 1 and the same evaluation of the
presence of burnt deposit in a high current density as in Example
4.
[0060] It was found that by positively using nickel as a metal
impurity contained in the trivalent chromium plating solution of
the present invention, the color tone and the appearance of the
resulting plating were equivalent to the case where plating was
formed with the solutions having a sodium vinylsulfonate 25%
aqueous solution added thereto in Examples 1 to 3, and burnt
deposit in a high current density in plating was prevented from
occurring. In the case where nickel was not added, burnt deposit in
a high current density in plating occurred.
INDUSTRIAL APPLICABILITY
[0061] The trivalent chromium plating solution of the present
invention can be applied to various purposes as similar to plating
with hexavalent chromium.
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