U.S. patent application number 12/590684 was filed with the patent office on 2011-05-12 for galvanization system and method of galvanizing treatment using thereof.
This patent application is currently assigned to Nihon Hyomen Kagaku Kabushiki Kaisha. Invention is credited to Katsuhiro Koike, Kazuyuki Shinozaki, Yusaku Tazono.
Application Number | 20110108430 12/590684 |
Document ID | / |
Family ID | 43973337 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110108430 |
Kind Code |
A1 |
Shinozaki; Kazuyuki ; et
al. |
May 12, 2011 |
Galvanization system and method of galvanizing treatment using
thereof
Abstract
A galvanization system comprising an alkaline galvanization
bath, a positive electrode, and a negative electrode is provided.
The alkaline galvanization bath comprises galvanizing solution
including about 7 to about 60 g/l of Zn, about 70 to about 200 g/l
of alkali hydroxide and about 0.01 to about 5 g/l of additives. The
positive electrode is insoluble in the galvanizing solution, having
an opposed surface to an object which is supposed to be set in the
alkaline galvanization bath and galvanized. The opposed surface of
the positive electrode is formed in a rectangular pattern having a
side equal to or less than 30 mm or in a circular pattern having a
diameter equal to or less than 30 mm. The galvanization system can
produce a galvanization membrane of excellent appearance.
Inventors: |
Shinozaki; Kazuyuki;
(Chigasaki-shi, JP) ; Tazono; Yusaku;
(Chigasaki-shi, JP) ; Koike; Katsuhiro;
(Chigasaki-shi, JP) |
Assignee: |
Nihon Hyomen Kagaku Kabushiki
Kaisha
Tokyo
JP
|
Family ID: |
43973337 |
Appl. No.: |
12/590684 |
Filed: |
November 12, 2009 |
Current U.S.
Class: |
205/309 ;
204/227; 204/242 |
Current CPC
Class: |
C25D 5/48 20130101; C25D
5/36 20130101; C25D 17/12 20130101; C25D 17/10 20130101; C25D 3/22
20130101 |
Class at
Publication: |
205/309 ;
204/242; 204/227 |
International
Class: |
C25D 3/22 20060101
C25D003/22; C25D 17/02 20060101 C25D017/02 |
Claims
1. A galvanization system comprising: an alkaline galvanization
bath comprising galvanizing solution including about 7 to about 60
g/l of Zn, about 70 to about 200 g/l of alkali hydroxide and about
0.01 to about 5 g/l of additives; a positive electrode which is
insoluble in the galvanizing solution, having an opposed surface to
an object which is supposed to be set in the alkaline galvanization
bath and galvanized; and a negative electrode, wherein the opposed
surface of the positive electrode is formed in a rectangular
pattern having a side equal to or less than 30 mm or in a circular
pattern having a diameter equal to or less than 30 mm.
2. The galvanization system according to claim 1, further
comprising a washing bath that the object is supposed to be set in
before the coating treatment, including about 5 to about 100 g/l of
alkali hydroxide and at least one selected from the group
consisting of (a) about 1 to about 100 g/l of a surface acting
agent, (b) organic acid or salt thereof, (c) phosphorus oxygen acid
and (d) an aliphatic amine compound.
3. The galvanization system according to claim 1, further
comprising an acid bath that the object is supposed to be set in
after the coating treatment.
4. The galvanization system according to claim 1, further
comprising an aftertreatment bath that the object is supposed to be
set in after the coating treatment and treated, wherein the
aftertreatment bath includes acid aqueous solution including at
least one selected from the group consisting of Cr, Co, Zn, Ni and
Ag, and at least one selected from the group consisting of chlorine
ion, sulfate ion and nitrate ion.
5. The galvanization system according to claim 4, wherein the acid
aqueous solution further comprises at least one selected from the
group consisting of silica, organic acid, phosphorus oxygen acid
and fluorine compound.
6. The galvanization system according to claim 4, further
comprising an alkaline treatment part that treats the object with
alkaline aqueous solution including at least one selected from the
group consisting of silica, acrylate resin, wax and silica resin
after the aftertreatment.
7. The galvanization system according to claim 1, wherein the
opposed surface of the positive electrode is formed in a
rectangular pattern having a side over 3 mm and equal to or less
than 25 mm or in a circular pattern having a diameter over 3 mm and
equal to or less than 25 mm.
8. The galvanization system according to claim 1, wherein the
positive electrode is made of Fe, carbon, Ni, Co, stainless steel,
Ti or alloyed metal including at least one selected from the group
consisting thereof.
9. The galvanization system according to claim 1, wherein the
plural positive electrodes are set in parallel.
10. The galvanization system according to claim 1, wherein the
additives comprises: a polymer having a structure of the formula
(I); and ##STR00005## (In the formula (I), R1 and R2 indicate H,
CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7 or C.sub.4H.sub.9, R3
indicates CH.sub.2, C.sub.2H.sub.4 or C.sub.3H.sub.6, n indicates
an integral number equal to or more than 1.) a polymer having a
structure of the formula (II); ##STR00006## (In the formula (II),
R1, R2, R3 and R4 indicate H, CH.sub.3, C.sub.2H.sub.5,
C.sub.3H.sub.7 or
C.sub.4H.sub.9--CH.sub.2--CH(OH)--CH.sub.2CH.sub.2(OCCH.sub.2CH.sub.2)XOH
(X=0 to 6), R5 indicates
--CH.sub.2--CH.sub.2--O--CH.sub.2--CH.sub.2--,
--(CH.sub.2--CH.sub.2--O).sub.2--CH.sub.2--CH.sub.2-- or
--CH.sub.2--CH(OH)--CH.sub.2--O--CH.sub.2--CH(OH)--CH.sub.2--, a
and b indicate 2 to 4, n indicates an integral number equal to or
more than 1, Y indicates S or O.) and further comprises at least
one selected from the group consisting of: a reaction product of
aliphatic amine and epihalohydrin; a reaction product of (a) urea
or thiourea, (b) dialkylaminoethylamine and/or
dialkylaminopropylamine and (c) dichloroalkylether; and
polyethyleneimine compound.
11. The galvanization system according to claim 1, wherein the
additives comprises at least one selected from the group consisting
of: aromatic aldehyde and derivatives thereof;
benzylpyridiniumcarboxylate; surface acting agent; (a) nicotine
acid and (b) halogenated hydrocarbon; and a reaction product of
alkylene oxide, halogen ether and epihalohydrin.
12. A method for galvanizing a surface of an object, using a
galvanization system comprising: an alkaline galvanization bath
comprising galvanizing solution including about 7 to about 60 g/l
of Zn, about 70 to about 200 g/l of alkali hydroxide and about 0.01
to about 5 g/l of additives; a positive electrode which is
insoluble in the galvanizing solution, having an opposed surface to
an object which is supposed to be set in the alkaline galvanization
bath and galvanized; and a negative electrode, wherein the opposed
surface of the positive electrode is formed in a rectangular
pattern having a side equal to or less than 30 mm or in a circular
pattern having a diameter equal to or less than 30 mm.
13. The method according to claim 12, wherein an average current
density of the negative electrode is about 0.4 to about 50
A/dm.sup.2.
14. The method according to claim 12, wherein an average current
density of the opposed surface of the positive electrode is about
0.5 to about 100 A/dm.sup.2.
15. The method according to claim 12, wherein an average
galvanizing rate is equal to or more than about 0.1 .mu.m/min in a
barrel galvanizing and equal to or more than about 0.3 .mu.m/min in
a rack galvanizing.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a galvanization system and
method of galvanizing treatment using thereof.
BACKGROUND OF THE INVENTION
[0002] Auto manufacturers and the like recently request high
corrosion resistance (for example, white rust is not found for 72
hours in a salt spray test) in a coating. In all sorts of coating,
a galvanization is practically the only coating that has an effect
of sacrificial corrosion prevention. Further, the galvanization can
be carried at lower cost than that of other coatings. Accordingly,
it is used the most. The galvanization is classified into two
types, one is a galvanization using galvanizing solution (pH: about
4 to about 6) which is generally called acidic bath and the other
is a galvanization using alkaline bath (pH: over 14). Further, the
alkaline bath is classified into a cyanide bath which includes
cyanogens and a zincate bath which does not include cyanogens. The
acidic bath has features such as giving beautiful lustrous
appearance. The cyanide bath has features such as giving membrane
of good workability. However, tightening of regulations of
industrial wastewater and the like has been promoted in accordance
with a heightening of consciousness to environment of recent years,
and there has been a movement to review the galvanizing solution.
In particular, it is no wonder that the cyanide bath has hazardous
nature because it includes deadly poison of cyanogens. The acidic
bath has problems about, for example, removal performance of heavy
metal, high COD and high BOD caused by a brightening agent, because
it includes ammonia in the galvanizing solution. On the other hand,
the zincate bath gains an edge on these bath in the environmental
terms of an easiness of wasterwater treatment and the like because
it does not include cyanogens and ammonia. Further, the zincate
bath has an advantage of having higher corrosion resistance than
that of other baths on requests of progress of the corrosion
resistance in recent years.
SUMMARY OF THE INVENTION
[0003] However, the zincate bath has a disadvantage that appearance
of membrane produced by the bath tends to be inhomogeneous
specifically by heating after coating treatment.
[0004] An object of the present application is to provide a
galvanization system that can produce a galvanization membrane of
excellent appearance by improving disadvantages of a zincate bath
that does not include toxic materials such as cyanogens and can
reduce the strain on environment with satisfying requests for high
corrosion resistance from auto manufacturers and so on. Another
object of the present invention is to provide a method of
galvanizing treatment using the galvanization system.
[0005] The inventors have extensively investigated to overcome the
above problems and have drawn attention not only to compositions of
galvanizing solution and additives that have been taken into
consideration but to function of positive electrode of counter
electrode. In general, the galvanization is carried in the negative
electrode and the positive electrode is thought to be a supply port
of electricity to the solution or a supply source of
electrocrystallization metal to the galvanizing solution.
Accordingly, even if zinc plate is used for the positive electrode
in the galvanization and copper plate is used for the positive
electrode in a copper plating, the zinc plate and copper plate are
not used in a nickel plating. As mentioned above, the function of
the positive electrode is simply grasped, therefore the positive
electrode has hardly been paid attention to on a solution of the
problem. The inventors also investigated with paying little
attention to the positive electrode at the beginning. However, at
one point, they found that, even if same additives are used,
appearances of membrane produced by using different compositions of
the positive electrode are different from each other, then they
found a clue to solve the problem as a result of further keen
examination.
[0006] In one aspect, the present invention completed as the basis
of the above knowledge is:
[0007] a galvanization system comprising:
[0008] an alkaline galvanization bath comprising galvanizing
solution including about 7 to about 60 g/l of Zn, about 70 to about
200 g/l of alkali hydroxide and about 0.01 to about 5 g/l of
additives;
[0009] a positive electrode which is insoluble in the galvanizing
solution, having an opposed surface to an object which is supposed
to be set in the alkaline galvanization bath and galvanized;
and
[0010] a negative electrode,
[0011] wherein the opposed surface of the positive electrode is
formed in a rectangular pattern having a side equal to or less than
30 mm or in a circular pattern having a diameter equal to or less
than 30 mm.
[0012] In one embodiment, the present invention is:
[0013] the galvanization system further comprising a washing bath
that the object is supposed to be set in before the coating
treatment, including about 5 to about 100 g/l of alkali hydroxide
and at least one selected from the group consisting of (a) about 1
to about 100 g/l of a surface acting agent, (b) organic acid or
salt thereof, (c) phosphorus oxygen acid and (d) an aliphatic amine
compound.
[0014] In preferred embodiment, the present invention is:
[0015] the galvanization system further comprising an acid bath
that the object is supposed to be set in after the coating
treatment.
[0016] In another preferred embodiment, the present invention
is:
[0017] the galvanization system according to claim 1, further
comprising an aftertreatment bath that the object is supposed to be
set in after the coating treatment and treated, wherein the
aftertreatment bath includes acid aqueous solution including at
least one selected from the group consisting of Cr, Co, Zn, Ni and
Ag, and at least one selected from the group consisting of chlorine
ion, sulfate ion and nitrate ion.
[0018] In another preferred embodiment, the present invention
is:
[0019] the galvanization system wherein the acid aqueous solution
further comprises at least one selected from the group consisting
of silica, organic acid, phosphorus oxygen acid and fluorine
compound.
[0020] In another preferred embodiment, the present invention
is:
[0021] the galvanization system further comprising an alkaline
treatment part that treats the object with alkaline aqueous
solution including at least one selected from the group consisting
of Si, acrylate resin, wax and silica resin after the
aftertreatment.
[0022] In another preferred embodiment, the present invention
is:
[0023] the galvanization system wherein the opposed surface of the
positive electrode is formed in a rectangular pattern having a side
over 3 mm and equal to or less than 25 mm or in a circular pattern
having a diameter over 3 mm and equal to or less than 25 mm.
[0024] In another preferred embodiment, the present invention
is:
[0025] the galvanization system wherein the positive electrode is
made of Fe, carbon, Ni, Co, stainless steel, Ti or alloyed metal
including at least one selected from the group consisting
thereof.
[0026] In another preferred embodiment, the present invention
is:
[0027] the galvanization system wherein the plural positive
electrodes are set in parallel.
[0028] In another preferred embodiment, the present invention
is:
[0029] the galvanization system wherein the additives
comprises:
[0030] a polymer having a structure of the formula (I); and
##STR00001##
(In the formula (I), R1 and R2 indicate H, CH.sub.3,
C.sub.2H.sub.5, C.sub.3H.sub.7 or C.sub.4H.sub.9, R3 indicates
CH.sub.2, C.sub.2H.sub.4 or C.sub.3H.sub.6, n indicates an integral
number equal to or more than 1.)
[0031] a polymer having a structure of the formula (II);
##STR00002##
(In the formula (II), R1, R2, R3 and R4 indicate H, CH.sub.3,
C.sub.2H.sub.5, C.sub.3H.sub.7 or
C.sub.4H.sub.2--O--CH.sub.2--CH.sub.2--CH(OH)--CH.sub.2CH.sub.2(OCCH.sub.-
2CH.sub.2)XOH (X=0 to 6), R5 indicates
--CH.sub.2--CH.sub.2--O--CH.sub.2--CH.sub.2--,
--(CH.sub.2--CH.sub.2--O).sub.2--CH.sub.2--CH.sub.2-- or
--CH.sub.2--CH(OH)--CH.sub.2--O--CH.sub.2--CH(OH)--CH.sub.2--, a
and b indicate 2 to 4, n indicates an integral number equal to or
more than 1, Y indicates S or O.)
[0032] and further comprises at least one selected from the group
consisting of:
[0033] a reaction product of aliphatic amine and epihalohydrin;
[0034] a reaction product of (a) urea or thiourea, (b)
dialkylaminoethylamine and or dialkylaminopropylamine and (c)
dichloroalkylether; and
[0035] polyethyleneimine compound.
[0036] In another preferred embodiment, the present invention
is:
[0037] the galvanization system wherein the additives comprises at
least one selected from the group consisting of:
[0038] aromatic aldehyde and derivatives thereof;
[0039] benzylpyridiniumcarboxylate;
[0040] surface acting agent;
[0041] (a) nicotine acid and (b) halogenated hydrocarbon; and
[0042] a reaction product of alkylene oxide, halogen ether and
epihalohydrin.
[0043] In another aspect, the present invention is:
[0044] a method for galvanizing a surface of an object, using a
galvanization system comprising:
[0045] an alkaline galvanization bath comprising galvanizing
solution including about 7 to about 60 g/l of Zn, about 70 to about
200 g/l of alkali hydroxide and about 0.01 to about 5 g/l of
additives;
[0046] a positive electrode which is insoluble in the galvanizing
solution, having an opposed surface to an object which is supposed
to be set in the alkaline galvanization bath and galvanized;
and
[0047] a negative electrode,
[0048] wherein the opposed surface of the positive electrode is
formed in a rectangular pattern having a side equal to or less than
30 mm or in a circular pattern having a diameter equal to or less
than 30 mm.
[0049] In one embodiment, the present invention is:
[0050] the method wherein an average current density of the
negative electrode is about 0.4 to about 50 A/dm.sup.2.
[0051] In preferred embodiment, the present invention is:
[0052] the method according to claim 12, wherein an average current
density of the opposed surface of the positive electrode is about
0.5 to about 100 A/dm.sup.2.
[0053] In another embodiment, the present invention is:
[0054] the method wherein an average galvanizing rate is equal to
or more than about 0.1 .mu.m/min in a barrel galvanizing and equal
to or more than about 0.3 .mu.m/min in a rack galvanizing.
[0055] The present invention can provide a galvanization system and
method of galvanizing treatment using thereof that can produce a
galvanization membrane of excellent appearance.
DESCRIPTION OF THE DRAWINGS
[0056] FIG. 1 is a perspective view of the positive electrode of
the galvanization system.
[0057] FIG. 2 is a side view of the positive electrode opposed to
the barrel in the galvanization system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Galvanization System
[0058] In the preferred embodiment, the galvanization system of the
present invention comprises:
[0059] an alkaline galvanization bath comprising galvanizing
solution including about 7 to about 60 g/l of Zn, about 70 to about
200 g/l of alkali hydroxide and about 0.01 to about 5 g/l of
additives;
[0060] a positive electrode which is insoluble in the galvanizing
solution, having an opposed surface to an object which is supposed
to be set in the alkaline galvanization bath and galvanized;
and
[0061] a negative electrode.
[0062] The positive electrode has at least one opposed surface to
the object. The positive electrode is formed in, for example, a
shape of a rectangular parallelepiped. The opposed surface of the
positive electrode is formed in a rectangular pattern having a side
equal to or less than 30 mm or in a circular pattern having a
diameter equal to or less than 30 mm. Preferably, the opposed
surface of the positive electrode is formed in a rectangular
pattern having a side over 3 mm and equal to or less than 25 mm or
in a circular pattern having a diameter over 3 mm and equal to or
less than 25 mm. If the positive electrode is formed in a spherical
pattern, its projection image has circular form. In this case, the
above specification is applied with respect to its diameter. The
positive electrode is made of, for example, Fe, carbon, Ni, Co,
stainless steel, Ti or alloyed metal including at least one
selected from the group consisting thereof. The plural positive
electrodes may be set in parallel to the object. Thus, a
galvanization membrane of excellent appearance can be efficiently
produced by the setting of the plural positive electrodes in
parallel to the object.
[0063] The above opposed surface of the positive electrode
indicates a surface opposing to the object and crosses nearly
perpendicular to a direction from the positive electrode to the
object.
[0064] As a specific example of the positive electrode, FIG. 1
indicates a perspective view of the positive electrode of the
galvanization system and FIG. 2 indicates a side view of the
positive electrode opposed to the barrel in the galvanization
system. In FIGS. 1 and 2, "Surface A" indicates the opposed surface
to the object, "L" indicates a width of "Surface A", "H" indicates
a height of "Surface A" and "D" indicates a depth of the positive
electrode. "L" is equal to or less than 30 mm in FIGS. 1 and 2.
Though such positive electrodes formed in a shape of a rectangular
parallelepiped are set in a longitudinal direction in FIGS. 1 and
2, that is not limited to such a configuration. That is, the
positive electrodes may be set, for example, in a transverse
direction. In addition, though the positive electrodes are set
separately in FIG. 2, they may be configured to connect with each
other by passing under the object. In the case of setting in a
longitudinal direction as described in FIG. 1, "H" is mostly
determined by a size of a galvanizing bath. For example, in the
case of a rack galvanizing, a length of "H" is preferably equal to
or somewhat less than that of the rack. "D" is generally 10 to 150
mm and practically 20 to 70 mm. If "D" is less than 10 mm, "L" is
equal to or less than 30 mm and it is anticipated that a problem of
strength poverty may occur. Accordingly, it is anticipated that the
positive electrode may transform because of a circulation of the
galvanizing solution and the like, and as a result, an unfavorable
problem of a contact (such as a short circuit) of the positive
electrode and the negative electrode (a barrel in the case of a
rotation plating) may occur. In addition, if "D" is long, a volume
of little relevance to galvanizing will increase and a bath of an
excessive size will be needed. As a result, there will be a lot of
disadvantages such as increases of cost of equipments and
installation space.
[0065] Examples of the alkali hydroxide in the alkaline
galvanization bath may include lithium hydroxide, sodium hydroxide,
potassium hydroxide and the like.
[0066] The additives in the alkaline galvanization bath may
comprise:
[0067] a polymer having a structure of the formula (I); and
##STR00003##
(In the formula (I), R1 and R2 indicate H, CH.sub.3,
C.sub.2H.sub.5, C.sub.3H.sub.7 or C.sub.4H.sub.9, R3 indicates
CH.sub.2, C.sub.2H.sub.4 or C.sub.3H.sub.6, n indicates an integral
number equal to or more than 1.)
[0068] a polymer having a structure of the formula (II);
##STR00004##
(In the formula (II), R1, R2, R3 and R4 indicate H, CH.sub.3,
C.sub.2H.sub.5, C.sub.3H.sub.7 or
C.sub.4H.sub.9--CH.sub.2--CH(OH)--CH.sub.2CH.sub.2(OCCH.sub.2CH.sub.2)XOH
(X=0 to 6), R5 indicates
--CH.sub.2--CH.sub.2--O--CH.sub.2--CH.sub.2--,
--(CH.sub.2--CH.sub.2--O).sub.2--CH.sub.2--CH.sub.2-- or
--CH.sub.2--CH(OH)--CH.sub.2--O--CH.sub.2--CH(OH)--CH.sub.2--, a
and b indicate 2 to 4, n indicates an integral number equal to or
more than 1, Y indicates S or O.)
[0069] and further comprises at least one selected from the group
consisting of:
[0070] a reaction product of aliphatic amine and epihalohydrin;
[0071] a reaction product of (a) urea or thiourea, (b)
dialkylaminoethylamine and/or dialkylaminopropylamine and (c)
dichloroalkylether; and
[0072] polyethyleneimine compound.
[0073] In another example, the additives in the alkaline
galvanization bath may comprise:
[0074] at least one selected from the group consisting of:
[0075] aromatic aldehyde and derivatives thereof;
[0076] benzylpyridiniumcarboxylate;
[0077] surface acting agent;
[0078] (a) nicotine acid and (b) halogenated hydrocarbon; and
[0079] a reaction product of alkylene oxide, halogen ether and
epihalohydrin.
[0080] Examples of the aliphatic amine may include at least one
selected from the group consisting of triethanolamine,
ethylenediamine, pentaethylenehexamine, diaminopropane,
diethylenetriamine, ethylaminoethanol, aminopropylethylenediamine,
bisaminopropylpiperazine, triethylenetetramine,
hexamethylenetetramine, isopropanolamine, aminoalcohol, imidazole,
picoline, piperazine, methylpiperazine, morpholine,
hydroxyethylaminopropylamine, tetramethylpropylenediamine,
dimethylaminopropylamine, dimethylaminoethylamine,
diethylaminoethylamine, dipropylaminoethylamine,
dibuthylaminoethylamine, diethylaminopropylamine,
dipropylaminopropylamine and dibuthylaminopropylamine.
[0081] The dichloroalkylether may be dichloroalkylether of carbon
number 1 to 5, preferably equal to or less than 4, and examples of
the dichloroalkylether may include dichloroethylether,
dichlorobuthylether and dichloropropylether.
[0082] Examples of the surface acting agent may include common
various surface acting agents, aromatic aldehyde such as
anisaldehyde, vanillin, heliotropin, veratraldehyde, benzaldehyde
and hydroxybenzaldehyde as aldehyde, or methyl substitution product
thereof, and formalin.
[0083] The galvanization system may comprise a washing bath that
the object is supposed to be set in before the coating treatment,
including about 5 to about 100 g/l of alkali hydroxide and at least
one selected from the group consisting of (a) about 1 to about 100
g/l of a surface acting agent, (b) organic acid or salt thereof,
(c) phosphorus oxygen acid and (d) an aliphatic amine compound.
[0084] Examples of the phosphorus oxygen acid may include
orthophosphoric acid, condensed phosphoric acid, hypophosphorous
acid, phosphorous acid and salt thereof, and its concentration in
the solution is about 0.5 to about 80 g/l, preferably about 1 to
about 60 g/l. In addition, it is necessary for molar ratio of
phosphorus and trivalent chrome (P/Cr) to be about 0.3 to about 25,
preferably about 1 to about 10. If the P/Cr is less than that, it
is difficult to produce a galvanization membrane of excellent
appearance and required functions may not be provided. If the P/Cr
is more than that, demerits of functional decline and increasing of
cost may occur because of an excess inclusion.
[0085] The galvanization system may comprise an acid bath that the
object is supposed to be set in after the coating treatment and
neutralized.
[0086] The galvanization system may further comprise an
aftertreatment bath that the object is supposed to be set in after
the coating treatment and treated, wherein the aftertreatment bath
includes acid aqueous solution including at least one selected from
the group consisting of Cr, Co, Zn, Ni and Ag, and at least one
selected from the group consisting of chlorine ion, sulfate ion and
nitrate ion.
[0087] The acid aqueous solution further may comprise at least one
selected from the group consisting of silica, organic acid,
phosphorus oxygen acid and fluorine compound.
[0088] The fluorine compound specifically has advantageous effects
on an improvement of excellent appearance of a galvanization
membrane. However, an excess inclusion of the compound causes a
degradation of a corrosion resistance. Accordingly, it is
preferable that a concentration of the fluorine compound is
comparatively small, that is, about 0.1 to 5 g/l, and it is more
preferable that the concentration is about 0.2 to about 3 g/l.
[0089] The galvanization system may further comprise an alkaline
treatment part that treats the object with alkaline aqueous
solution including at least one selected from the group consisting
of silica, acrylate resin, wax and silica resin after the
aftertreatment. By using the alkaline treatment part, a friction
coefficient can be controlled and a corrosion resistance can be
further improved.
[0090] The alkaline treatment part may be an alkaline bath
including alkaline aqueous solution or an alkaline aqueous solution
injecting nozzle that injects alkaline aqueous solution to a
surface of the object.
[0091] (Galvanizing Method Using the Galvanization System)
[0092] In the preferred embodiment, the galvanizing method of the
present invention uses the above galvanization system.
[0093] At first, it is preferable that the object is washed before
galvanizing. It is preferable that the washing is conducted by
setting the object in alkaline or acid aqueous solution, or by
setting the object in alkaline or acid aqueous solution and then
applying electrolysis to the object. The alkaline is given by
various alkali hydroxides and the acid is given by hydrochloric
acid, sulfuric acid and the like. In particular, the washing is
conducted by setting the object in a washing bath including about 5
to about 100 g/l of alkali hydroxide and at least one selected from
the group consisting of (a) about 1 to about 100 g/l of a surface
acting agent, (b) organic acid or salt thereof, (c) phosphorus
oxygen acid and (d) an aliphatic amine compound. In more
particular, the above washing agent preferably includes at least
one selected from the group consisting of anionic system surface
acting agent, nonionic system surface acting agent, organic
carboxylic acid or salt thereof, EDTA salt, NTA salt, phosphoric
acid, pyrophoric acid, phosphorous acid, hypophosphorous acid or
salt thereof, aliphatic amine of carbon number equal to or less
than 12 or reaction product of the aliphatic amine and
epihalohydrin.
[0094] Examples of the surface acting agent may include
commercially available various surface acting agents, in
particular, linear alkylbenzenesulfonate, .alpha.-olefinsulfonate
and polyoxyethylenealkylethersulfate. Examples of counter ions of
salt thereof may include alkali metal such as Na and K, alkali
earth metal such as Mg, alkanolamine such as monoethanolamine,
diethanolamine and triethanolamine. Examples of the more concrete
commercially available linear alkylbenzenesulfonate may include
"LIPON LS-250" (produced by Lion) and "TAYCAPOWER LN2065" (produced
by Tayca). Examples of the more concrete .alpha.-olefinsulfonate
may include "LIPOLAN PB-800" (produced by Lion). Examples of the
more concrete polyoxyethylenealkylethersulfate may include
"TAYCAPOLE NE 1270" and "TAYCAPOLE NE 1230" (produced by Tayca). In
addition, polyoxyalkylenealkylether, alkylpolyglycerylester,
alkylpolyglycerylether, methoxypolyoxyalkylenealkanoate, aliphatic
acid diethanolamide, aliphatic acid monoethanolamide,
alkylpolyglycoside and the like may be exemplified. Examples of the
more concrete commercially available polyoxyalkylenealkylether may
include "LEOCALL SC-90", "LEOX CC-90", "LEOCALL SC-120" and
"LEOCALL TD-150" (produced by Lion), "EMALEX 705", "EMALEX 715" and
"EMALEX 720" (produced by Nihon Emulsion), and "NAROACTY 50",
"NAROACTY 100" and "NAROACTY 160" (produced by Sanyo Chemical
Industries). Examples of the organic acid or salt thereof may
include at least one selected from the group consisting of
monocarboxylic acid such as formic acid, acetic acid and propionic
acid, dicarboxylic acid such as oxalic acid, malonic acid, succinic
acid and adipic acid, tricarboxylic acid such as tricarbamic acid,
hydroxycarboxylic acid such as glycolic acid, lactic acid, malic
acid, tartaric acid and citric acid, aminocarboxylic acid such as
glycine and alanine, and salt thereof. The organic acid is
preferably dicarboxylic acid or tricarboxylic acid.
[0095] Examples of the aliphatic amine may include the above
mentioned types of amine.
[0096] The above washing treatment is conducted at about 5 to about
80.degree. C., preferably about 20 to about 70.degree. C., for
about 1 to about 30 minutes, preferably about 3 to about 20
minutes. In the case of electrolysis, the object is conducted the
electrolytic treatment at about 5 to about 80.degree. C.,
preferably about 20 to about 70.degree. C., for about 1 to 30
minutes, preferably about 3 to about 20 minutes with positive
current, negative current or alternateness thereof.
[0097] The object is set in the alkaline galvanization bath. One
surface (opposed surface) of the positive electrode opposes nearly
perpendicular to the object. Electric current is passed through
between the negative electrode and the positive electrode of the
alkaline galvanization bath by supplying with voltage. The average
current density of the negative electrode is controlled to about
0.4 to about 50 A/dm.sup.2 (about 0.4 to about 7 A/dm.sup.2, more
preferably 0.5 to about 5 A/dm.sup.2 in a barrel galvanizing, about
3 to about 50 A/dm.sup.2, more preferably about 4 to about 30
A/dm.sup.2 in a rack galvanizing). The average current density of
the opposed surface of the positive electrode is controlled to
about 0.5 to about 100 A/dm.sup.2, preferably about 1 to about 80
A/dm.sup.2, more preferably about 6 to about 40 A/dm.sup.2, more
preferably about 9 to about 30 A/dm.sup.2. In the case that the
coating treatment is the barrel galvanizing, the average
galvanizing rate is controlled to equal to or more than about 0.1
.mu.m/min, more preferably equal to or more than about 0.15
.mu.m/min. In the case that the coating treatment is the rack
galvanizing, the average galvanizing rate is controlled to equal to
or more than about 0.3 .mu.m/min, more preferably equal to or more
than about 1 .mu.m/min.
[0098] The temperature of the galvanizing solution is about 15 to
about 65.degree. C., more preferably about 20 to 55.degree. C.
[0099] Conventional galvanization systems have a case containing
rectangular or circular plates, or balls that are made of various
types of metal as positive electrodes. If a plate of width:100
mm-length:200 mm-thickness:40 mm is used, its surface of width:100
mm-length:200 mm is opposed to the object. A size of the case is
determined according to plates or balls contained in the case.
Examples of the metal plates include, for example, plates of
width:100 to 200 mm-length:200 to 1000 mm-thickness:40 to 50 mm.
There are plates that have lager size of the above width and length
because they are determined according to a size of a bath. The
diameters of the circular plate and ball are 50 to 80 mm.
[0100] On the other hand, the galvanization system in the
embodiment of the present invention, as mentioned above, does not
require plating metal supply sources of positive electrode plates,
the system has an insoluble positive electrode and a separate bath
and an opposed surface to the object in each insoluble positive
electrode has one side or a diameter equal to or less than 30 mm.
Thus, by making one side or a diameter of the opposed surface to
the object in the positive electrode equal to or less than 30 mm,
nonuniformity of electric current running through the surface of
the positive electrode can be restrained and electric current of
excellent uniformity can run through the surface. Accordingly,
galvanization membrane produced by the system has excellent
uniformity. Therefore, corrosion resistance of the galvanization
membrane improves.
[0101] Further, in the galvanization system in the embodiment of
the present invention, the coating treatment can be conducted by
lower voltage than that of conventional coating treatments because
the positive electrode is constructed as described above.
Accordingly, electric energy can be saved. In particular, with
respect to conventional zincate bath galvanizations, the coating
treatment is conducted by a voltage of 7 to 8V in a rack
galvanizing and by a voltage of 12 to 13V in a rotation
galvanizing. On the other hand, with respect to the galvanization
system in the embodiment of the present invention, the coating
treatment can be conducted by a voltage of less than 5V in a rack
galvanizing and by a voltage of less than 8V in a barrel
galvanizing, and electric energy can be saved by over about
30%.
[0102] If needed, the object is set in the acid bath and
neutralized after the coating treatment.
[0103] Then, if needed, the object is set in an aftertreatment bath
including acid aqueous solution including at least one selected
from the group consisting of Cr, Co, Zn, Ni and Ag, and at least
one selected from the group consisting of chlorine ion, sulfate ion
and nitrate ion, and the aftertreatment is conducted in order to
keep the excellent appearance of the produced galvanization
membrane. If a concentration of at least one selected from the
group consisting of Cr, Co, Zn, Ni and Ag is low, it is difficult
to get good results. If the concentration is high, the effect
decreases and its cost increases because of excess quantity of the
ingredients. Accordingly, it is preferable to set appropriate
concentrations. For example, the concentration of Cr is preferably
about 0.1 to about 30 g/l, more preferably about 0.2 to about 15
g/l. For more details, it depends on other ingredients. For
example, if organic acid is included, the concentration of Cr is
preferably about 1 to 10 g/l. If organic acid is not included, the
concentration of Cr is preferably about 0.3 to 5 g/l. The
concentration of Co is also preferably about 0.1 to about 15 g/l,
more preferably about 0.3 to about 10 g/l, further preferably about
0.5 to about 5 g/l. In addition, other types of metal ions, for
example, Mg, Ca, Zr, V, Al, Fe and the like can be included. Total
concentration of at least one selected from the group consisting of
chlorine ion, sulfate ion and nitrate ion is preferably about 1 to
about 300 g/l, more preferably about 3 to about 100 g/l. These ions
can be provided by acid such as sulfuric acid and nitric acid, and
by compounds such as chromium sulfate and chromium nitrate.
Carboxylic acid and the like can be used as the organic acid, and
the total concentration is about 1 to about 80 g/l, preferably
about 3 to about 50 g/l. Mole ratio of organic acid and Cr (Organic
acid/Cr) is about 0.1 to 6, preferably about 0.4 to 2.5. If a
volume of the organic acid is little, the solution becomes
unstable, and precipitation is produced or corrosion resistance
deteriorates. If a volume of the organic acid is excess, its cost
and COD in waste effluent increase and strain on environment
increases.
[0104] The aftertreatment is conducted to set the object in the
aftertreatment bath of pH about 1 to about 6.5 at about 10 to about
60.degree. C., preferably about 15 to about 45.degree. C., for
about 1 to about 80 seconds, preferably about 5 to about 60
seconds. If the object is set in the aftertreatment bath once, pH
is preferably about 1 to about 4.5, more preferably about 1.5 to
about 4. If the object is set more than once, the first setting is
as described above, and the settings after the first are conducted
preferably at pH about 3.5 to about 6.5, more preferably at pH
about 4.0 to about 5.5.
[0105] If it is practically necessary to control friction
coefficient and the like and to improve corrosion resistance
further, the object is treated with alkaline aqueous solution
including at least one selected from the group consisting of
silica, acrylate resin, wax and silica resin. The concentration
thereof is about 1 to about 500 g/l, and it is determined according
to required friction coefficient, corrosion resistance and the
like. Examples of usable silica may include normal silica and
colloidal silica, and various types of silica product produced by
Fuso Chemical, Nissan Chemical and the like can be used. The
concentration of silica is about 3 to about 50 g/l, preferably
about 5 to about 20 g/l. If a volume of silica is little, the
effect can be hardly provided. If the volume is much, its cost
increases and the appearance of the produced galvanization membrane
deteriorates. Examples of the acrylate resin may include "ALMATEX"
produced by Mitsui Chemical and "ACRYSET" produced by Nippon
Shokubai. Examples of the silica resin and wax may also include
commercially available products, for example, "SS-N series"
produced by Exousia and polyethylene wax.
EXAMPLES
[0106] Examples of the present invention are described below.
However, they are provided for a better understanding of the
present invention, and do not intend to limitations of the present
invention.
Example 1
[0107] As a pretreatment, a bolt was set in a solution including 10
g/l of UPON LS-250, 5 g/l of sodium phosphate, 30 g/l of potassium
hydrate, 5 g/l of EDTA 4 Na and 1 g/l of sodium tartrate at
60.degree. C. for 20 minutes. Then the bolt was electrolyzed at 0.7
A/dm.sup.2 of current density of the negative electrode for 5
minutes in a solution including 5 g/l of diethanolamine. Then the
bolt was set in a solution including 150 g/l of hydrochloric acid
at 25.degree. C. for 10 minutes, and electrolyzed at 1.5 A/dm.sup.2
of current density of the negative electrode in a solution
including 5 g/l of triethanolamine at 50.degree. C. Washing before
galvanizing was completed by the above treatments.
[0108] After the washing, a rotation galvanizing was conducted to
the bolt with a positive electrode as described in FIG. 1. One side
(L) of the positive electrode opposing to a barrel was 4 mm. Plural
positive electrodes were used and the average current density at a
surface of the positive electrode opposing to the object was 10
A/dm.sup.2.
[0109] A zincate bath including 11 g/l of Zn, 110 g/l of sodium
hydrate, 2 g/l of the polymer of the above formula (I) and 0.4 g/l
of vanillin was used as the galvanizing solution, a galvanizing was
conducted in the galvanizing solution at 45.degree. C. at 13V for
15 minutes, then metallized membrane of about 7 .mu.m thick was
produced. After the galvanizing, a dehydrogenation treatment was
conducted to the bolt at 200.degree. C. for 4 hours. Then the bolt
was set in a solution at pH 2.0 including 1 g/l of trivalent
chrome, 20 g/l of colloidal silica, 4 g/l of sulfate ion, 10 g/l of
nitrate ion and 0.8 g/l of Co at 25.degree. C. for 45 seconds with
stirring and was dried, then Example 1 was produced.
[0110] In the polymer of the formula (I) in this example, R1, R2
and R3 indicate CH.sub.3, and n indicates 10.
Example 2
[0111] As a pretreatment, a bolt was set in a solution including 8
g/l of LEOX CC-90, 7 g/l of LIPON LS-200, 5 g/l of sodium
pyrophosphate, 40 g/l of sodium hydrate, 3 g/l of EDTA 4 Na, 1 g/l
of monoethanolamine and 21 g/l of sodium gluconate at 60.degree. C.
for 20 minutes. Then the bolt was electrolyzed at 1 A/dm.sup.2 of
current density of the negative electrode for 5 minutes in a
solution including 7 g/l of diethanolamine. Then the bolt was set
in a solution including 180 g/l of hydrochloric acid at 25.degree.
C. for 7 minutes, and electrolyzed at 1 A/dm.sup.2 of current
density of the negative electrode in a solution including 8 g/l of
triethanolamine at 50.degree. C. Washing before galvanizing was
completed by the above treatments. After the washing, a rotation
galvanizing was conducted to the bolt with a rod-like iron positive
electrode bending at lower 1/4 thereof along the barrel as
described in FIG. 1. One side (L) of the positive electrode
opposing to a barrel was 8 mm. Plural positive electrodes were used
and the average current density at a surface of the positive
electrode opposing to the object was 8 A/dm.sup.2.
[0112] A zincate bath including 35 g/l of Zn, 160 g/l of sodium
hydrate, 1.5 g/l of the polymer of the above formula (I) as
described in Example 1, 0.3 g/l of a polymer of the formula (II),
0.3 g/l of benzylpyridiniumcarboxylate and 0.5 g/l of ethylvanillin
was used as the galvanizing solution, and a galvanizing was
conducted in the galvanizing solution at 35.degree. C. at 7V for 20
minutes. After the galvanizing, a dehydrogenation treatment was
conducted to the bolt at 200.degree. C. for 4 hours. Then the bolt
was set in a solution at pH 1.8 including 6 g/l of trivalent
chrome, 10 g/l of malonic acid, 20 g/l of colloidal silica, 4 g/l
of sulfate ion, 10 g/l of nitrate ion and 0.8 g/l of Co at
50.degree. C. for 50 seconds with stirring and was dried, then
Example 2 was produced.
[0113] In the polymer of the formula (II) in this example, R1, R2,
R3 and R4 indicate CH.sub.3, R5 indicates
--CH.sub.2--CH.sub.2--O--CH.sub.2--CH.sub.2, n indicates 6, a
indicates 3, b indicates 3 and Y indicates O.
Example 3
[0114] After washing as described in Example 2, a galvanizing was
conducted to the bolt in a zincate bath having galvanizing solution
including 20 g/l of Zn, 130 g/l of sodium hydrate, 0.5 g/l of the
polymer of the above formula (I) as described in Example 1, 0.7 g/l
of a reaction product of dimethylaminoethyl amine and
dichloroethylether at a rate of about 1.5 to about 1, 0.2 g/l of
benzylpyridiniumcarboxylate and 0.3 g/l of ethylvanillin. Rod-like
iron positive electrodes were used and one side (L) of the positive
electrode opposing to a barrel was 5 mm. The average current
density at a surface of the positive electrode opposing to the
object was 5 A/dm.sup.2. The galvanizing was conducted in the
galvanizing solution at 35.degree. C. at 8V for 15 minutes. After
the galvanizing, a dehydrogenation treatment was conducted to the
bolt at 200.degree. C. for 4 hours. Then the bolt was set in a
solution at pH 2.4 including 1.8 g/l of trivalent chrome, 0.2 g/l
of sulfuric acid, 1.5 g/l of phosphoric acid, 4 g/l of sodium
hyposulfite, 6.5 g/l of sodium nitrate and 1.2 g/l of Co at
35.degree. C. for 40 seconds with stirring. Then the bolt was set
in a solution at pH 5.0 including 5 g/l of trivalent chrome, 4 g/l
of Zn, 1.5 g/l of Co, 5 g/l of sodium phosphate and 2 g/l of oxalic
acid at 40.degree. C. for 10 seconds, and was dried, then Example 3
was produced.
Example 4
[0115] After washing as described in Example 2, a galvanizing was
conducted to the bolt in a zincate bath having galvanizing solution
including 20 g/l of Zn, 130 g/l of sodium hydrate, 1.0 g/l of the
polymer of the above formula (I) as described in Example 1, 0.2 g/l
of the polymer of the above formula (II) as described in Example 2,
0.3 g/l of a reaction product of dimethylaminoethyl amine and
dichloroethylether at a rate of about 1.4 to about 1, 0.2 g/l of
benzylpyridiniumcarboxylate and 0.3 g/l of vanillin. Rod-like iron
positive electrodes were used and one side (L) of the positive
electrode opposing to a barrel was 4 mm. The average current
density at a surface of the positive electrode opposing to the
object was 6.0 A/dm.sup.2. The galvanizing was conducted in the
galvanizing solution at 35.degree. C. at 2.0 A/dm.sup.2 of the
average current density at a surface of the negative electrode for
15 minutes. After the galvanizing, a dehydrogenation treatment was
conducted to the bolt at 200.degree. C. for 4 hours. Then the bolt
was set in a solution at pH 2.0 including 6 g/l of trivalent
chrome, 10 g/l of malonic acid, 20 g/l of colloidal silica, 4 g/l
of sulfate ion, 10 g/l of nitrate ion and 0.8 g/l of Co at
25.degree. C. for 45 seconds with stirring and was dried. Then the
bolt was set in alkaline solution including 5 g/l of acrylate
resin, 2 g/l of colloidal silica and 0.3 g/l of polyethylene wax at
25.degree. C. for 8 seconds, and was dried, then Example 4 was
produced.
Example 5
[0116] After washing as described in Example 1, a galvanizing was
conducted to the bolt in a zincate bath having galvanizing solution
including 11 g/l of Zn, 110 g/l of sodium hydrate, 2 g/l of the
polymer of the above formula (I) as described in Example 1 and 0.4
g/l of vanillin. Rod-like iron positive electrodes were used and
one side (L) of the positive electrode opposing to a barrel was 25
mm. Plural positive electrodes were used and the average current
density at a surface of the positive electrode opposing to the
object was 10 A/dm.sup.2. The galvanizing was conducted in the
galvanizing solution at 45.degree. C. at 13V for 15 minutes. By the
above treatment, metallized membrane of about 7 .mu.m thick was
produced. After the galvanizing, a dehydrogenation treatment was
conducted to the bolt at 200.degree. C. for 4 hours. Then the bolt
was set in a solution at pH 2.0 including 1 g/l of trivalent
chrome, 20 g/l of colloidal silica, 4 g/l of sulfate ion, 10 g/l of
nitrate ion and 0.8 g/l of Co at 25.degree. C. for 45 seconds with
stirring, and was dried, then Example 5 was produced.
Example 6
[0117] After washing as described in Example 1, a galvanizing was
conducted to the bolt in a zincate bath having galvanizing solution
including 40 g/l of Zn, 160 g/l of sodium hydrate, 2.5 g/l of the
polymer of the above formula (I) as described in Example 1, 0.3 g/l
of the polymer of the above formula (II) as described in Example 2,
0.3 g/l of benzylpyridiniumcarboxylate and 0.5 g/l of
ethylvanillin. As the galvanizing, a rotation galvanizing was
conducted to the bolt with a rod-like iron positive electrode
bending at lower 1/4 thereof along the barrel as described in FIG.
1. One side (L) of the positive electrode opposing to a barrel was
15 mm. Plural positive electrodes were used and the average current
density at a surface of the positive electrode opposing to the
object was 12 A/dm.sup.2.
[0118] The galvanizing was conducted in the galvanizing solution at
40.degree. C. at 7V for 20 minutes. After the galvanizing, a
dehydrogenation treatment was conducted to the bolt at 200.degree.
C. for 4 hours. Then the bolt was set in a solution at pH 1.8
including 6 g/l of trivalent chrome, 10 g/l of malonic acid, 20 g/l
of colloidal silica, 4 g/l of sulfate ion, 10 g/l of nitrate ion
and 0.8 g/l of Co at 50.degree. C. for 50 seconds with stirring,
and was dried, then Example 6 was produced.
Example 7
[0119] After washing as described in Example 2, a galvanizing was
conducted to the bolt in a zincate bath having galvanizing solution
including 20 g/l of Zn, 145 g/l of sodium hydrate, 2 g/l of the
polymer of the above formula (I) as described in Example 1 and 0.4
g/l of vanillin. Plural Rod-like iron positive electrodes were used
and one side (L) of the positive electrode opposing to a barrel was
20 mm. The average current density at a surface of the positive
electrode opposing to the object was 10 A/dm.sup.2. The galvanizing
was conducted in the galvanizing solution at 45.degree. C. at 13V
for 15 minutes. By the above treatment, metallized membrane of
about 7 .mu.m thick was produced. After the galvanizing, a
dehydrogenation treatment was conducted to the bolt at 200.degree.
C. for 4 hours. Then the bolt was set in a solution at pH 2.0
including 1 g/l of trivalent chrome, 20 g/l of colloidal silica, 4
g/l of sulfate ion, 10 g/l of nitrate ion and 0.8 g/l of Co at
25.degree. C. for 45 seconds with stirring, and was dried, then
Example 7 was produced.
Example 8
[0120] After washing as described in Example 2, a galvanizing was
conducted to the bolt in a zincate bath having galvanizing solution
including 25 g/l of Zn, 135 g/l of sodium hydrate, 1.0 g/l of the
polymer of the above formula (I) as described in Example 1, 0.2 g/l
of the polymer of the above formula (II) as described in Example 2,
0.3 g/l of a reaction product of dimethylaminoethyl amine and
dichloroethylether at a rate of about 1.4 to about 1, 0.2 g/l of
benzylpyridiniumcarboxylate and 0.3 g/l of vanillin. Rod-like iron
positive electrodes were used and one side (L) of the positive
electrode opposing to a barrel was 22 mm. The average current
density at a surface of the positive electrode opposing to the
object was 10 A/dm.sup.2. The galvanizing was conducted in the
galvanizing solution at 30.degree. C. at 2.0 A/dm.sup.2 of the
average current density at a surface of the negative electrode for
15 minutes. After the galvanizing, a dehydrogenation treatment was
conducted to the bolt at 200.degree. C. for 4 hours. Then the bolt
was set in a solution at pH 2.0 including 6 g/l of trivalent
chrome, 10 g/l of malonic acid, 20 g/l of colloidal silica, 4 g/l
of sulfate ion, 10 g/l of nitrate ion and 0.8 g/l of Co at
25.degree. C. for 45 seconds with stirring and was dried. Then the
bolt was set in alkaline solution including 5 g/l of acrylate
resin, 2 g/l of colloidal silica and 0.3 g/l of polyethylene wax at
25.degree. C. for 8 seconds, and was dried, then Example 8 was
produced.
Comparative Example 1
[0121] As a positive electrode, zinc plates (width: about 200
mm-length: about 1000 mm-thickness: about 35 mm, length of the
shortest side in a surface of the positive electrode opposing to
the object: about 200 mm) that used in common galvanizing treatment
were used. As for the rest, same treatments as described in Example
3 were conducted.
Comparative Example 2
[0122] As a positive electrode, iron plates having a size being the
same as that of the zinc plates of Comparative example 1 were used.
As for the rest, same treatments as described in Example 3 were
conducted.
Comparative Example 3
[0123] As a positive electrode, a zinc ball (diameter: about 50 mm)
set in an iron case (width: about 200 mm-length: about 1000
mm-thickness: about 75 mm) was used. As for the rest, same
treatments as described in Example 2 were conducted.
[0124] Appearance evaluation tests and corrosion resistance
evaluation tests with salt spray according to JIS Z2371 were
conducted to Examples and Comparative examples. Results are shown
in Table 1.
TABLE-US-00001 TABLE 1 Appearance evaluation Corrosion resistance
evaluation Example 1 uniform/excellent white rust was not found for
120 hours. red rust was not found for 240 hours. Example 2
uniform/excellent white rust was not found for 120 hours. red rust
was not found for 240 hours. Example 3 uniform/excellent white rust
was not found for 120 hours. red rust was not found for 240 hours.
Example 4 uniform/excellent white rust was not found for 120 hours.
red rust was not found for 240 hours. Example 5 uniform/excellent
white rust was not found for 120 hours. red rust was not found for
240 hours. Example 6 uniform/excellent white rust was not found for
120 hours. red rust was not found for 240 hours. Example 7
uniform/excellent white rust was not found for 120 hours. red rust
was not found for 240 hours. Example 8 uniform/excellent white rust
was not found for 120 hours. red rust was not found for 240 hours.
Comparative ununiform white rust was found in 48 hours. example 1
red rust was found in 144 hours. Comparative ununiform white rust
was found in 48 hours. example 2 red rust was found in 144 hours.
Comparative ununiform white rust was found in 48 hours. example 3
red rust was found in 144 hours.
* * * * *