U.S. patent application number 13/636858 was filed with the patent office on 2013-05-23 for coated steel sheet, method for producing the same, and resin-coated steel sheet obtained using the same.
This patent application is currently assigned to JFE STEEL CORPORATION. The applicant listed for this patent is Masao Inose, Hiroki Iwasa, Yuka Miyamoto, Norihiko Nakamura, Hisato Noro, Takeshi Suzuki, Yoichi Tobiyama. Invention is credited to Masao Inose, Hiroki Iwasa, Yuka Miyamoto, Norihiko Nakamura, Hisato Noro, Takeshi Suzuki, Yoichi Tobiyama.
Application Number | 20130130055 13/636858 |
Document ID | / |
Family ID | 44673381 |
Filed Date | 2013-05-23 |
United States Patent
Application |
20130130055 |
Kind Code |
A1 |
Miyamoto; Yuka ; et
al. |
May 23, 2013 |
COATED STEEL SHEET, METHOD FOR PRODUCING THE SAME, AND RESIN-COATED
STEEL SHEET OBTAINED USING THE SAME
Abstract
A coated steel sheet includes a corrosion-resistant coating
composed of at least one layer selected from the group consisting
of a Ni layer, a Sn layer, an Fe--Ni alloy layer, an Fe--Sn alloy
layer, and an Fe--Ni--Sn alloy layer disposed on at least one
surface of a steel sheet, and an adhesive coating disposed on the
corrosion-resistant coating, the adhesive coating containing Zr and
further containing at least one metal element selected from the
group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn, in total, at a
ratio by mass of 0.01 to 10 with respect to Zr. The coated steel
sheet has excellent humid resin adhesion and corrosion resistance,
in which streaky surface defects do not occur.
Inventors: |
Miyamoto; Yuka; (Kawasaki,
JP) ; Suzuki; Takeshi; (Chiba, JP) ; Iwasa;
Hiroki; (Kawasaki, JP) ; Nakamura; Norihiko;
(Chiba, JP) ; Inose; Masao; (Kawasaki, JP)
; Noro; Hisato; (Kawasaki, JP) ; Tobiyama;
Yoichi; (Chiba, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Miyamoto; Yuka
Suzuki; Takeshi
Iwasa; Hiroki
Nakamura; Norihiko
Inose; Masao
Noro; Hisato
Tobiyama; Yoichi |
Kawasaki
Chiba
Kawasaki
Chiba
Kawasaki
Kawasaki
Chiba |
|
JP
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
JFE STEEL CORPORATION
TOKYO
JP
|
Family ID: |
44673381 |
Appl. No.: |
13/636858 |
Filed: |
March 24, 2011 |
PCT Filed: |
March 24, 2011 |
PCT NO: |
PCT/JP2011/058154 |
371 Date: |
January 4, 2013 |
Current U.S.
Class: |
428/626 ;
205/104; 205/183; 428/660 |
Current CPC
Class: |
C25D 3/38 20130101; C25D
5/36 20130101; C25D 9/08 20130101; C25D 9/10 20130101; Y10T
428/12806 20150115; C23C 22/50 20130101; C25D 3/22 20130101; C25D
5/12 20130101; C25D 3/02 20130101; C25D 3/20 20130101; C25D 3/30
20130101; C25D 5/505 20130101; C23G 1/081 20130101; C23C 28/021
20130101; C25D 3/54 20130101; Y10T 428/12569 20150115; C25D 3/12
20130101; C25D 5/10 20130101; C21D 8/0278 20130101; C25D 7/00
20130101; C21D 8/0221 20130101; C21D 9/46 20130101; C25D 5/50
20130101; C25F 1/00 20130101 |
Class at
Publication: |
428/626 ;
205/183; 205/104; 428/660 |
International
Class: |
C25D 3/02 20060101
C25D003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 25, 2010 |
JP |
2010-069015 |
Aug 19, 2010 |
JP |
2010-193825 |
Sep 15, 2010 |
JP |
2010-206515 |
Claims
1. A coated steel sheet comprising: a corrosion-resistant coating
composed of at least one layer selected from the group consisting
of a Ni layer, a Sn layer, an Fe--Ni alloy layer, an Fe--Sn alloy
layer, and an Fe--Ni--Sn alloy layer disposed on at least one
surface of a steel sheet; and an adhesive coating disposed on the
corrosion-resistant coating, the adhesive coating containing Zr and
further containing at least one metal element selected from the
group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn, in total, at a
ratio by mass of 0.01 to 10 with respect to Zr.
2. The coated steel sheet according to claim 1 wherein the adhesive
coating further contains P derived from a phosphoric acid and/or C
derived from a phenolic resin, in total, at a ratio by mass of 0.01
to 10 with respect to Zr.
3. The coated steel sheet according to claim 1, wherein the Zr
coating weight of the adhesive coating is 3 to 200 mg/m.sup.2 per
one surface of the steel sheet.
4. A method for producing a coated steel sheet comprising:
depositing a corrosion-resistant coating composed of at least one
layer selected from the group consisting of a Ni layer, a Sn layer,
an Fe--Ni alloy layer, an Fe--Sn alloy layer, and an Fe--Ni--Sn
alloy layer on at least one surface of a steel sheet; and disposing
an adhesive coating by performing cathodic electrolysis with an
electric charge density of 1 to 20 C/dm.sup.2 in an aqueous
solution which includes Zr in an amount of 0.008 to 0.07 mol/l and
further includes at least one metal element selected from the group
consisting of Co, Fe, Ni, V, Cu, Mn, and Zn, in total, at a molar
ratio of 0.01 to 10 with respect to Zr.
5. A method for producing a coated steel sheet comprising:
disposing a corrosion-resistant coating composed of at least one
layer selected from the group consisting of a Ni layer, a Sn layer,
an Fe--Ni alloy layer, an Fe--Sn alloy layer, and an Fe--Ni--Sn
alloy layer on at least one surface of a steel sheet; and disposing
an adhesive coating by performing cathodic electrolysis in an
aqueous solution which includes Zr in an amount of 0.008 to 0.07
mol/l and further includes at least one metal element selected from
the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn, in total, at
a molar ratio of 0.01 to 10 with respect to Zr, under the
electrolysis conditions, using an electric current having a current
density that changes with a cycle of 0.01 to 0.4 seconds between
the current density at which Zr is deposited and the current
density at which Zr is not deposited, and having a period of 0.005
to 0.2 seconds per cycle during which Zr is not deposited, in which
the number of cycles is 10 or more and the total electric charge
density at the current density at which Zr is deposited is 3 to 20
C/dm.sup.2, wherein the upper limit of the current density at which
Zr is not deposited is a value that depends on the composition and
pH of the aqueous solution used in the cathodic electrolysis.
6. The method for producing a coated steel sheet according to claim
5, further comprising using an electric current having a current
density that changes in a binary manner between the current density
at which Zr is deposited and the current density at which Zr is not
deposited.
7. The method for producing a coated steel sheet according to claim
6, wherein the current density at which Zr is not deposited is set
at 0 A/dm.sup.2.
8. The method for producing a coated steel sheet according to claim
4, wherein the aqueous solution further includes a phosphoric acid
and/or a phenolic resin, in total, at a molar ratio of 0.01 to 10
with respect to Zr.
9. A resin-coated steel sheet comprising the coated steel sheet
according to claim 1, the coated steel sheet being coated with a
resin.
10. The method for producing a coated steel sheet according to
claim 5, wherein the aqueous solution further includes a phosphoric
acid and/or a phenolic resin, in total, at a molar ratio of 0.01 to
10 with respect to Zr.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the U.S. National Phase application of
PCT/JP2011/058154, filed Mar. 24, 2011, and claims priority to
Japanese Patent Application Nos. 2010-069015, filed Mar. 25, 2010,
2010-183825, filed Aug. 19, 2010, and 2010-206515, filed Sep. 15,
2010, the disclosures of which are incorporated herein by reference
in their entireties for all purposes.
FIELD OF THE INVENTION
[0002] The present invention relates to a coated steel sheet which
is mainly used for containers, such as cans, after being further
coated with a resin in such a manner that the surface of the coated
steel sheet is laminated with a resin film or the like or a paint
containing a resin is applied onto the surface of the coated steel
sheet, and more particularly, relates to a coated steel sheet which
has excellent adhesion to a resin coated thereon in a
high-temperature, and humid environment (hereinafter, referred to
as "humid resin adhesion"), and which exhibits excellent corrosion
resistance even if the coated resin peels off. The invention also
relates to a method for producing the same, and to a resin-coated
steel sheet obtained by further coating the coated steel sheet with
a resin.
BACKGROUND OF THE INVENTION
[0003] Metal sheets, such as tin-plated steel sheets and
electrolytic chromium coated steel sheets referred to as tin-free
steel sheets, are used for various metal cans, such as beverage
cans, food cans, pail cans, and 18-liter cans. In particular,
tin-free steel sheets are produced by subjecting steel sheets to
electrolysis in a coating bath containing hexavalent Cr, and have
excellent humid resin adhesion to a resin, such as a paint, coated
thereon.
[0004] In recent years, in response to growing environmental
awareness, there has been a worldwide trend toward restricting use
of hexavalent Cr, and there has also been a demand for alternative
materials to tin-free steel sheets produced using a coating bath of
hexavalent Cr.
[0005] On the other hand, various metal cans have been
conventionally manufactured in such a manner that metal sheets,
such as tin-free steel sheets, are painted and then formed into can
bodies. In recent years, in order to reduce waste associated with
manufacturing operations, a method has come to be frequently used
in which a resin-coated metal sheet that is not painted but is
coated with a resin, such as a plastic film, and formed into a can
body. In the resin-coated metal sheet, the resin needs to strongly
adhere to the metal sheet. In particular, resin-coated metal sheets
used for beverage cans or food cans are required to have excellent
humid resin adhesion such that the resin does not peel off even in
a high-temperature and humid environment because the cans may be
subjected to a retort process, in some cases, after contents have
been packed therein, and are also required to have excellent
corrosion resistance such that the cans are prevented from being
corroded and pierced by the contents of the cans or the like even
when the resin partially peels off owing to being scratched or the
like.
[0006] Under these requirements, the present inventors have
recently proposed, in Patent Literature 1, that it is possible to
produce a coated steel sheet having very excellent humid resin
adhesion and excellent corrosion resistance, without using Cr, by
depositing a corrosion-resistant coating composed of at least one
layer selected from the group consisting of a Ni layer, a Sn layer,
an Fe--Ni alloy layer, an Fe--Sn alloy layer, and an Fe--Ni--Sn
alloy layer on at least one surface of steel sheet, and then
depositing an adhesive coating to a resin to be coated thereon by
performing cathodic electrolysis in an aqueous solution which
includes ions containing Ti and further includes ions containing at
least one metal element selected from the group consisting of Co,
Fe, Ni, V, Cu, Mn, and Zn.
PATENT LITERATURE
[0007] [PTL 1] Japanese Unexamined Patent Application Publication
No. 2009-155665
SUMMARY OF THE INVENTION
[0008] In the coated steel sheet produced by the method according
to Patent Literature 1, streaky surface defects may occur in some
cases.
[0009] The present invention provides, without using Cr, a coated
steel sheet which has excellent humid resin adhesion and corrosion
resistance and in which streaky surface defects do not occur, a
method for producing the same, and a resin-coated steel sheet
obtained using the coated steel sheet.
[0010] The present inventors have performed intensive studies and
have found that, when an adhesive coating of Patent Literature 1 is
deposited, it is effective to perform cathodic electrolysis in an
aqueous solution which includes Zr instead of Ti and further
includes at least one metal element selected from the group
consisting of Co, Fe, Ni, V, Cu, Mn, and Zn.
[0011] The present invention has been made based on such a finding.
The present invention provides a coated steel sheet characterized
by including a corrosion-resistant coating composed of at least one
layer selected from the group consisting of a Ni layer, a Sn layer,
an Fe--Ni alloy layer, an Fe--Sn alloy layer, and an Fe--Ni--Sn
alloy layer disposed on at least one surface of steel sheet, and an
adhesive coating disposed on the corrosion-resistant coating, the
adhesive coating containing Zr and further containing at least one
metal element selected from the group consisting of Co, Fe, Ni V,
Cu, Mn, and Zn, in total, at a ratio by mass of 0.01 to 10 with
respect to Zr. In the coated steel sheet of the present invention,
preferably, the adhesive coating further contains P derived from a
phosphoric acid and/or C derived from a phenolic resin, in total,
at a ratio by mass of 0.01 to 10 with respect to Zr. Furthermore,
preferably, the Zr coating weight of the adhesive coating is 3 to
200 mg/m.sup.2 per one surface.
[0012] A coated steel sheet of the present invention can be
produced by depositing a corrosion-resistant coating composed of at
least one layer selected from the group consisting of a Ni layer, a
Sn layer, an Fe--Ni alloy layer, an Fe--Sn alloy layer, and an
Fe--Ni--Sn alloy layer on at least one surface of a steel sheet,
and depositing an adhesive coating by performing cathodic
electrolysis with an electric charge density of 1 to 20 C/dm.sup.2
in an aqueous solution which includes Zr in an amount of 0.008 to
0.07 mol/l (1: liter) and further includes at least one metal
element selected from the group consisting of Co, Fe, Ni, V, Cu,
Mn, and Zn, in total, at a molar ratio of 0.01 to 10 with respect
to Zr.
[0013] Furthermore, a coated steel sheet of the present invention
can be produced by depositing a corrosion-resistant coating
composed of at least one layer selected from the group consisting
of a Ni layer, a Sn layer, an Fe--Ni alloy layer, an Fe--Sn alloy
layer, and an Fe--Ni--Sn alloy layer on at least one surface of a
steel sheet, and then depositing an adhesive coating by performing
cathodic electrolysis in an aqueous solution which includes Zr in
an amount of 0.008 to 0.07 mol/l and further includes at least one
metal element selected from the group consisting of Co, Fe, Ni, V,
Cu, Mn, and Zn, in total, at a molar ratio of 0.01 to 10 with
respect to Zr, under the electrolysis conditions, using an electric
current having a current density that changes with a cycle of 0.01
to 0.4 seconds between the current density at which Zr is deposited
and the current density at which Zr is not deposited, and having a
period of 0.005 to 0.2 seconds per cycle during which Zr is not
deposited, in which the number of cycles is 10 or more and the
total electric charge density at the current density at which Zr is
deposited is 3 to 20 C/dm.sup.2. In this case, the upper limit of
the current density at which Zr is not deposited is a value that
depends on the composition and pH of the aqueous solution used in
the cathodic electrolysis. In this production method, it may be
possible to use an electric current having a current density that
changes in a binary manner between the current density at which Zr
is deposited and the current density at which Zr is not deposited.
In this case, preferably, the current density at which Zr is not
deposited is set at 0 A/dm.sup.2.
[0014] In any of the production methods described above,
preferably, the aqueous solution used in the cathodic electrolysis
further includes a phosphoric acid and/or a phenolic resin, in
total, at a molar ratio of 0.01 to 10 with respect to Zr.
[0015] The present invention also provides a resin-coated steel
sheet in which the coated steel sheet of the present invention
described above is coated with a resin.
[0016] According to the present invention, it has become possible
to produce, without using Cr, a coated steel sheet which has
excellent humid resin adhesion and corrosion resistance and in
which streaky surface defects do not occur. The coated steel sheet
of the present invention can be used without any problem as an
alternative material to replace conventional tin-free steel sheets
and can be used, without being coated with a resin, for containers
which contain oil, organic solvents, paint, or the like.
Furthermore, when the coated steel sheet is coated with a resin to
obtain a resin-coated steel sheet and the resin-coated steel sheet
is formed into cans or can lids, and even when the cans or can lids
are exposed to a retort atmosphere, the resin does not peel off. In
addition, at resin peel-off portions, such as scratches, the amount
of dissolving out of Fe of a base steel sheet is markedly small,
and very good corrosion resistance is exhibited.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a graph showing the relationship between the Zr
coating weight and the current density in an aqueous solution, with
pH4, containing 12.5 g/l of potassium hexafluorozirconate and 5 g/l
of cobalt sulfate heptahydrate.
[0018] FIG. 2(a), FIG. 2(b), and FIG. 2(c) are views illustrating a
180.degree. peeling test.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0019] 1) Coated Steel Sheet
[0020] In a coated steel sheet of an embodiment of the present
invention, a corrosion-resistant coating composed of at least one
layer selected from the group consisting of a Ni layer, a Sn layer,
an Fe--Ni alloy layer, an Fe--Sn alloy layer, and an Fe--Ni--Sn
alloy layer is disposed on at least one surface of steel sheet, and
an adhesive coating containing Zr and further containing at least
one metal element selected from the group consisting of Co, Fe, Ni,
V, Cu, Mn, and Zn is disposed thereon.
[0021] As a base steel sheet, a low-carbon cold-rolled steel sheet
commonly used for cans can be used.
[0022] 1.1) Corrosion-Resistant Coating
[0023] The corrosion-resistant coating disposed on the surface of
the base steel sheet needs to be a coating composed of a single
layer selected from a Ni layer, a Sn layer, an Fe--Ni alloy layer,
an Fe--Sn alloy layer, and an Fe--Ni--Sn alloy layer or a
multi-layer including some of these layers so that it strongly
bonds to the base steel sheet in order to impart excellent
corrosion resistance to the steel sheet even when, after the coated
steel sheet is coated with a resin, the resin partially peels off
owing to being scratched or the like. In the case of a Ni layer,
the Ni coating weight is preferably set at 200 mg/m.sup.2 or more
per one surface of steel sheet. In the case of an Fe--Ni alloy
layer, the Ni coating weight is preferably set at 60 mg/m.sup.2 or
more per one surface of the steel sheet. In the case of a Sn layer
or an Fe--Sn alloy layer, the Sn coating weight is preferably set
at 100 mg/m.sup.2 or more per one surface of the steel sheet. In
the case of an Fe--Ni--Sn alloy layer, preferably, the Ni coating
weight is set at 50 mg/m.sup.2 or more and the Sn coating weight is
set at 100 mg/m.sup.2 or more per one surface of the steel sheet.
The coating weights of Ni and Sn can be determined by surface
analysis using fluorescence X-rays.
[0024] Such a corrosion-resistant coating can be disposed by a
known method appropriate to the metal element to be contained.
[0025] 1.2) Adhesive Coating
[0026] By disposing, on the corrosion-resistant coating, an
adhesive coating containing Zr and further containing at least one
metal element selected from the group consisting of Co, Fe, Ni, V,
Cu, Mn, and Zn, in total, at a ratio by mass of 0.01 to 10, more
preferably 0.01 to 2, with respect to Zr, excellent humid resin
adhesion can be obtained, and prevention of occurrence of streaky
surface defects is ensured. Although the reason for this is not
clear at present, it is believed that by incorporating these metal
elements into the coating containing Zr, a dense coating having
uniformly distributed surface irregularities is formed.
[0027] Preferably, the adhesive coating further contains P derived
from a phosphoric acid and/or C derived from a phenolic resin, in
total, at a ratio by mass of 0.01 to 10 with respect to Zr. The
reason for this is that by incorporating P derived from a
phosphoric acid and/or C derived from a phenolic resin into the
adhesive coating, coatability of the adhesive coating is further
improved and corrosion resistance is improved. Although the reason
for improvement in coatability is not clear at present, it is
believed that hydroxyl groups present in the adhesive coating,
hydroxyl groups of the phenolic resin or hydroxyl groups of the
phosphoric acid, and hydroxyl groups present on the surface of the
corrosion-resistant coating are crosslinked by dehydration
condensation, resulting in covalent bonds between the
corrosion-resistant coating and the adhesive coating through oxygen
atoms.
[0028] In the adhesive coating, the Zr coating weight is preferably
3 to 200 mg/m.sup.2 per one surface of the steel sheet. The reason
for this is that at a Zr coating weight of 3 to 200 mg/m.sup.2,
effects of improving humid resin adhesion and preventing occurrence
of streaky surface defects can be sufficiently obtained, and at a
Zr coating weight exceeding 200 mg/m.sup.2, the effects are
saturated, resulting in an increase in cost. The Zr coating weight
is more preferably 20 to 100 mg/m.sup.2.
[0029] In the adhesive coating, the total coating weight of at
least one metal element selected from the group consisting of Co,
Fe, Ni, V, Cu, Mn, and Zn is preferably 10 to 200 mg/m.sup.2 per
one surface of the steel sheet. When the total coating weight of
these metal elements is 10 mg/m.sup.2 or more and 200 mg/m.sup.2 or
less, it is possible to form a coating having excellent humid resin
adhesion and having no streaky surface defects.
[0030] Preferably, the adhesive coating further includes O. The
reason for this is that by incorporating O, the coating becomes
mainly composed of oxides of Zr, thus being more effective in
improving humid resin adhesion and preventing occurrence of streaky
surface defects.
[0031] Note that the coating weight of Zr and the coating weights
of Co, Fe, Ni, V, Cu, Mn, Zn, and P in the adhesive coating can be
determined by surface analysis using fluorescence X-rays. The C
content in the adhesive coating can be obtained by subtracting the
C content in the steel sheet as a background from the total C
content measured by gas chromatography. Although the O content is
not particularly specified, the presence of O can be confirmed by
surface analysis using XPS (X-ray photoelectron spectrometer).
[0032] The adhesive coating can be disposed by performing cathodic
electrolysis with an electric charge density of 1 to 20 C/dm.sup.2
in an aqueous solution which includes Zr in an amount of 0.008 to
0.07 mol/l, preferably 0.02 to 0.05 mol/l, and further includes at
least one metal element selected from the group consisting of Co,
Fe, Ni, V, Cu, Mn, and Zn, in total, at a molar ratio of 0.01 to
10, preferably 0.01 to 2.5, more preferably 0.01 to 2, with respect
to Zr. When the Zr amount is less than 0.008 mol/l, it is not
possible to disposing a coating having excellent humid resin
adhesion and having no streaky surface defects. On the other hand,
when the Zr amount exceeds 0.07 mol/l, it becomes difficult for Zr
to be present in a stable state in the aqueous solution, and Zr
oxides are formed. When the total amount, in terms of molar ratio,
of at least one metal element selected from the group consisting of
Co, Fe, Ni, V, Cu, Mn, and Zn is less than 0.01, it is difficult to
dispose a coating having excellent humid resin adhesion and having
no streaky surface defects. On the other hand, when the total
amount exceeds 10, the effects are saturated, resulting in an
increase in cost.
[0033] As an aqueous solution containing Zr, an aqueous solution
containing fluorozirconate ions or an aqueous solution containing
fluorozirconate ions and a fluoride salts is preferable. As a
compound that produces fluorozirconate ions, hexafluorozirconic
acid, ammonium hexafluorozirconate, potassium hexafluorozirconate,
or the like can be used. As a fluoride salt, sodium fluoride,
potassium fluoride, silver fluoride, tin fluoride, or the like can
be used. In particular, an aqueous solution containing potassium
hexafluorozirconate or an aqueous solution containing potassium
hexafluorozirconate and sodium fluoride can dispose a homogeneous
coating efficiently, which is preferable.
[0034] Furthermore, as a compound that produces Co, Fe, Ni, V, Cu,
Mn, and Zn, cobalt sulfate, cobalt chloride, iron sulfate, iron
chloride, nickel sulfate, copper sulfate, vanadium oxide sulfate,
zinc sulfate, manganese sulfate, and the like can be used. In this
case, these metal elements are added such that the total amount, in
terms of molar ratio with respect to Zr, is 0.01 to 10, preferably
0.01 to 2.5, and more preferably 0.01 to 2.
[0035] The cathodic electrolysis may be performed with a current
density of 5 to 20 A/dm.sup.2 and at an electrolysis time of 1 to 5
sec. Preferably, the electric charge density is set at 3 to 15
C/dm.sup.2.
[0036] Furthermore, when the cathodic electrolysis is performed,
using an electric current having a current density that cyclically
changes between the current density at which Zr is deposited and
the current density at which Zr is not deposited so that the
coating is grown intermittently, it is possible to obtain excellent
humid resin adhesion compared with the case where electrolysis is
performed continuously at a constant current. For that purpose, it
is necessary to secure a certain Zr coating weight. In order to
secure the Zr coating weight necessary for achieving productivity
(line speed) on a commercial basis, it is preferable to perform
cathodic electrolysis under the electrolysis conditions, using an
electric current having a current density that changes with a cycle
of 0.01 to 0.4 seconds between the current density at which Zr is
deposited and the current density at which Zr is not deposited, and
having a period of 0.005 to 0.2 seconds per cycle during which Zr
is not deposited, in which the number of cycles is 10 or more and
the total electric charge density at the current density at which
Zr is deposited is 3 to 20 C/dm.sup.2. It is believed that, by
performing electrolysis under such conditions, at the current
density at which Zr is not deposited, redissolution of deposited Zr
is promoted rather than it being the case that deposition of Zr
does not occur, and therefore, a denser coating having more
uniformly distributed surface irregularities is formed, and
excellent humid resin adhesion can be obtained.
[0037] The upper limit of the current density at which Zr is not
deposited, i.e., the current density at the boundary between the
case where Zr is not deposited and the case where Zr is deposited,
depends on the composition and pH of the aqueous solution including
Zr and at least one metal element selected from the group
consisting of Co, Fe, Ni, V, Cu, Mn, and Zn. For example, FIG. 1
shows the relationship between the Zr coating weight and the
current density in an aqueous solution, with pH4, containing 12.5
g/l of potassium hexafluorozirconate and 5 g/l of cobalt sulfate
heptahydrate. In this case, it is obvious that deposition of Zr
does not occur at 0.8 A/dm.sup.2 or less. As described above, since
the upper limit of the current density at which Zr is not deposited
depends on the composition and pH of the aqueous solution used in
the cathodic electrolysis, it is necessary to predetermine the
upper limit depending on the aqueous solution to be used.
[0038] As the electric current having a current density that
changes cyclically between the current density at which Zr is
deposited and the current density at which Zr is not deposited, an
alternating current that changes cyclically in a manner similar to
a sine curve, or a pulsed current that changes in a binary manner
between the current density at which Zr is deposited and the
current density at which Zr is not deposited can be used. It is
also possible to use a current obtained by superposing an
alternating current or a pulsed current on a direct current. In the
case where a pulsed current that changes in a binary manner between
the current density at which Zr is deposited and the current
density at which Zr is not deposited is used, more preferably, the
current density at which Zr is not deposited is set at 0 A/dm.sup.2
because it eliminates the need to predetermine the upper limit of
the current density depending on the aqueous solution to be
used.
[0039] In the present invention, preferably, the cathodic
electrolysis is performed in the aqueous solution which further
includes a phosphoric acid and/or a phenolic resin, in total, at a
molar ratio of 0.01 to 10 with respect to Zr. The reason for this
is that, by performing the cathodic electrolysis in the aqueous
solution including phosphoric acid and/or phenolic resin, it is
possible to dispose an adhesive coating containing P derived from a
phosphoric acid and/or C derived from a phenolic resin, resulting
in further improvement in coatability of the adhesive coating and
improvement in corrosion resistance. In this case, as a compound
that produces a phosphoric acid, orthophosphoric acid or a
phosphate compound of the metal element added simultaneously may be
used, or nickel phosphate, iron phosphate, cobalt phosphate,
zirconium phosphate, or the like can be used. As a phenolic resin,
a phenolic resin having a weight-average molecular weight of about
3,000 to 20,000 is preferable, and a phenolic resin having a
weight-average molecular weight of about 5,000 is more preferable.
Furthermore, the phenolic resin may be provided with water
solubility by being amino/alcohol denatured.
[0040] 2) Resin-Coated Steel Sheet (Laminated Steel Sheet)
[0041] A resin-coated steel sheet can be obtained by coating the
coated steel sheet of the present invention with a resin. As
described above, since the coated steel sheet of the present
invention has excellent humid resin adhesion, the resin-coated
steel sheet has excellent corrosion resistance and formability.
[0042] The resin used to coat the coated steel sheet of the present
invention is not particularly limited. For example, any of various
thermoplastic resins and thermosetting resins may be used. Examples
the resin that can be used include olefin resin films, such as
polyethylene, polypropylene, ethylene-propylene copolymers,
ethylene-vinyl acetate copolymers, ethylene-acrylic ester
copolymers, and ionomers; polyester films, such as polybutylene
terephthalate; polyamide films, such as nylon 6, nylon 6,6, nylon
11, and nylon 12; and thermoplastic resin films, such as polyvinyl
chloride films and polyvinylidene chloride films. These films may
be unoriented or biaxially oriented. In the case where an adhesive
is used for lamination, a urethane adhesive, epoxy adhesive,
acid-modified olefin resin adhesive, copolyamide adhesive,
copolyester adhesive, or the like (thickness: 0.1 to 5.0 .mu.m) is
preferable. Furthermore, a thermosetting paint may be applied onto
the coated steel sheet or the film with a thickness in the range of
0.05 to 2 .mu.m and used as an adhesive.
[0043] Furthermore, thermoplastic or thermosetting paints, such as
modified epoxy paints (e.g., phenol epoxy and amino-epoxy paints),
vinyl chloride-vinyl acetate copolymers, saponified vinyl
chloride-vinyl acetate copolymers, vinyl chloride-vinyl
acetate-maleic anhydride copolymers, epoxy-modified-, epoxy
amino-modified, or epoxy phenol-modified vinyl paints, or modified
vinyl paints, acrylic paints, and synthetic rubber paints (e.g.,
styrene-butadiene copolymers), may be used alone or in combination
of two or more.
[0044] The thickness of the resin coating layer is preferably in
the range of 3 to 50 .mu.m, and more preferably 5 to 40 .mu.m. When
the thickness falls below the range described above, corrosion
resistance becomes insufficient. When the thickness exceeds the
range described above, a problem in terms of formability is likely
to occur.
[0045] The resin coating layer can be disposed on the coated steel
sheet by any method. For example, an extrusion coating method, a
cast film heat bonding method, a biaxially oriented film heat
bonding method, or the like can be used. In the extrusion coating
method, the coated steel sheet may be extrusion-coated with a resin
in a molten state, and the resin is heat-bonded to the coated steel
sheet. That is, the resin is melted and kneaded in an extruder and
then extruded into a thin film from a T-die. The extruded molten
resin film, together with the coated steel sheet, is passed between
a pair of lamination rolls, and the thin film and the coated steel
sheet are integrated under pressure in a cooling environment,
followed by quenching. In the case where a multi-layered resin
coating layer is disposed by extrusion coating, it may be possible
to use a method in which a plurality of extruders for corresponding
layers are used, resin flows from the individual extruders are
joined together in a multilayer die, and then extrusion coating is
performed in the same manner as that for a single-layer resin.
Furthermore, it is possible to dispose resin coating layers on both
surfaces of the coated steel sheet by passing the coated steel
sheet perpendicularly between a pair of lamination rolls, and
supplying a molten resin web onto both surfaces.
[0046] The resin-coated steel sheet can be used for three-piece
cans with side seams and seamless cans (two-piece cans). The
resin-coated steel sheet can also be used for lids of stay-on-tab
easy open cans and lids of full open easy open cans.
[0047] Described above are merely examples of embodiments of the
present invention. Various modifications may be made within the
scopes of the present invention.
Example 1
[0048] Corrosion-resistant coatings are disposed on both surfaces
of cold-rolled steel sheet (thickness: 0.2 mm), which is made as
cold-rolled low-carbon steel used to produce a tin-free steel sheet
(TFS), using coating bath a or b shown in Table 1, by one of the
methods A to D described below.
[0049] A: A cold-rolled steel sheet is annealed in an atmosphere of
10 vol % H.sub.2+90 vol % N.sub.2 at about 700.degree. C.,
subjected to temper rolling at an elongation percentage of 1.5%,
degreased by alkali electrolysis, pickled with sulfuric acid, and
then coated with Ni using the coating bath a to thereby dispose
corrosion-resistant coatings made of Ni layers.
[0050] B: A cold-rolled steel sheet is degreased by alkali
electrolysis, coated with Ni using the coating bath a, annealed in
an atmosphere of 10 vol % H.sub.2+90 vol % N.sub.2 at about
700.degree. C. to perform diffusion coating of Ni, and then
subjected to temper rolling at an elongation percentage of 1.5% to
thereby dispose corrosion-resistant coatings made of Fe--Ni alloy
layers.
[0051] C: A cold-rolled steel sheet is degreased by alkali
electrolysis, coated with Ni using the coating bath a, annealed in
an atmosphere of 10 vol % H.sub.2+90 vol % N.sub.2 at about
700.degree. C. to perform diffusion coating of Ni, subjected to
temper rolling at an elongation percentage of 1.5%, followed by
degreasing and acid pickling, coated with Sn using the coating bath
b, and subjected to melting by heating the steel sheet at a
temperature equal to or higher than the melting point of Sn.
Thereby, a corrosion-resistant coating including an Fe--Ni--Sn
alloy layer and a Sn layer thereon is disposed.
[0052] D: A cold-rolled steel sheet is degreased by alkali
electrolysis, annealed under the same conditions as the conditions
A, subjected to temper rolling, coated with Sn using the coating
bath b, and subjected to melting by heating the steel sheet at a
temperature equal to or higher than the melting point of Sn.
Thereby, a corrosion-resistant coating including an Fe--Sn alloy
layer and a Sn layer thereon is disposed.
[0053] In the methods C and D, Sn coating is partially alloyed by
the melting treatment. The net coating weight of remaining Sn which
remains without being alloyed is shown in Tables 3 to 5.
[0054] Then, by performing cathodic electrolysis under the cathodic
electrolysis conditions shown in Tables 2 to 5, followed by drying,
adhesive coatings are formed on the corrosion resistant coatings
disposed on both surfaces of each of the steel sheets. Thereby,
coated steel sheets Nos. 1 to 33 are produced. Note that coated
steel sheet Nos. 1, 16, 19, 22, and 29 are comparative examples, in
which the adhesive coating does not contain any of Co, Fe, Ni, V,
Cu, Mn, and Zn. Nos. 30 and 31 are comparative examples, in which
corrosion-resistant coatings are not disposed. Nos. 32 and 33 are
comparative examples, in which adhesive coatings containing Ti and
further containing V or Mn are disposed on corrosion-resistant
coatings.
[0055] The Zr coating weight and Ti coating weight in each adhesive
coating are determined by X-ray fluorescence analysis in comparison
with a calibration sheet in which the content of each metal is
determined by chemical analysis in advance. Furthermore, regarding
Co, Fe, Ni, V, Cu, Mn, and Zn, the coating weights contained are
determined by a method appropriately selected from X-ray
fluorescence analysis, the same technique as that used for Zr and
Ti, chemical analysis, Auger electron spectroscopy analysis, and
secondary ion mass spectrometry, and the mass ratio of Co, Fe, Ni,
V, Cu, Mn, and Zn to Zr or Ti is evaluated. Furthermore, the
presence of O can be confirmed by XPS surface analysis in each of
Nos. 1 to 33.
[0056] Furthermore, both surfaces of each of the coated steel sheet
Nos. 1 to 33 are laminated with isophthalic acid copolymerized
polyethylene terephthalate films (draw ratio: 3.1.times.3.1,
thickness: 25 copolymerization ratio: 12 mol %, melting point:
224.degree. C.) under the laminating conditions such that the
degree of biaxial orientation (BO value) of the films is 150, i.e.,
with a steel sheet feed rate of 40 m/min, a nip length of rubber
roll of 17 mm, a period of time from pressure bonding to water
cooling of 1 second. Thereby, laminated steel sheet Nos. 1 to 33
are produced. The term "nip length" means the length of a contact
portion of a rubber roll with each steel sheet in the feed
direction. Regarding the resulting laminated steel sheet Nos. 1 to
33, humid resin adhesion, corrosion resistance, and streaky surface
defects are evaluated.
[0057] Humid resin adhesion: Humid resin adhesion is evaluated by a
180.degree. peeling test in a retort atmosphere having a
temperature of 130.degree. C. and a relative humidity of 100%. The
180.degree. peeling test is a film peel test in which a test piece
(size: 30 mm.times.100 mm, the front and rear surfaces being each
n=1, each laminated steel sheet being n=2) obtained by cutting a
portion 3 of a steel sheet 1 so that a film 2 remains as shown in
FIG. 2(a) is used, a weight 4 (100 g) is attached to an end of the
test piece, the test piece is folded 180.degree. over the film 2 as
shown in FIG. 2(b), and the test piece is left to stand for 30
minutes. A peel length 5 shown in FIG. 2(c) is measured and
evaluated. The peel lengths (n=2) of the front and rear surfaces of
each laminated steel sheet are averaged. As the peel length 5
decreases, the test piece is considered to have better humid resin
adhesion. When the peel length 5 is less than 20 mm, the test piece
is evaluated to have excellent humid resin adhesion targeted in the
present invention.
[0058] Corrosion resistance: A laminate surface of each laminated
steel sheet is cut in a crossing manner with a cutter knife such
that the cut depth reaches the base steel sheet, the laminated
steel sheet is immersed in 80 ml of a test liquid prepared by
mixing equivalent amounts of 1.5% by mass NaCl aqueous solution and
1.5% by mass citric acid aqueous solution, and left to stand at
55.degree. C. for 9 days. The corrosion resistance of the cut
portions is evaluated under the following criteria (both surfaces
of each laminated steel sheet are evaluated, that is, evaluation
number n=2), symbol .largecircle. indicating good corrosion
resistance:
.largecircle.: No corrosion in both n=2. x: Corrosion in one or
more of n=2.
[0059] Streaky surface defects: Degree of occurrence of streaky
patterns is visually observed and evaluated as follows:
.largecircle.: No streaky patterns are observed. x: Streaky
patterns are observed.
[0060] The results are shown in Table 6. In all of laminated steel
sheet Nos. 2 to 15, 17, 18, 20, 21, and 23 to 28, which are
examples of the present invention, good humid resin adhesion and
corrosion resistance are exhibited, and no streaky surface defects
are observed. In contrast, in laminated steel sheet Nos. 1, 16, 19,
22, and 29, which are comparative examples, although there is no
problem in corrosion resistance, humid resin adhesion is poor. In
laminated steel sheet Nos. 30 and 31, although there is no problem
in humid resin adhesion, corrosion resistance is poor. In laminated
steel sheet Nos. 32 and 33, although there is no problem in humid
resin adhesion or corrosion resistance, streaky patterns are
observed on the surface.
TABLE-US-00001 TABLE 1 Coating bath Bath composition a (Ni coating
Nickel sulfate: 250 g/l, nickel chloride: 45 g/l, boric acid: bath)
30 g/l b (Sn coating Stunnous sulfate: 55 g/l, phenolsulfonic
acid(65% by mass): bath) 35 g/l, brightener: appropriate amount
TABLE-US-00002 TABLE 2 Coating Cathodic electrolysis treatment Zr
amount Molar ratio Current Electric Coated steel Coating in bath of
metal M density Electrolysis charge density sheet No. method
Treatment bath composition (mol/l) to Zr in bath (A/dm.sup.2) time
(sec) (C/dm.sup.2) 1 A Potassium hexafluorozirconate 12.5 g/l 0.044
0 3 2.0 6.0 2 A Potassium hexafluorozirconate 12.5 g/l + 0.044
0.476 4 1.2 4.8 cobalt chloride hexahydrate 5 g/l 3 A Potassium
hexafluorozirconate 12.5 g/l + 0.044 1.428 5 1.2 6.0 cobalt
chloride hexahydrate 15 g/l 4 A Potassium hexafluorozirconate 6.5
g/l + 0.023 2.746 6 1.2 7.2 cobalt chloride hexahydrate 15 g/l 5 A
Potassium hexafluorozirconate 12.5 g/l + 0.044 0.403 5 1.2 6.0
cobalt sulfate heptahydrate 5 g/l 6 A Potassium hexafluorozirconate
12.5 g/l + 0.044 0.403 6 1.2 7.2 cobalt sulfate heptahydrate 5 g/l
7 A Potassium hexafluorozirconate 12.5 g/l + 0.044 1.355 4 1.2 4.8
iron sulfate heptahydrate 5 g/l + cobalt chloride hexahydrate 10
g/l 8 A Potassium hexafluorozirconate 6.3 g/l + 0.022 0.808 4 1.6
6.4 iron sulfate heptahydrate 5 g/l 9 A Potassium
hexafluorozirconate 12.5 g/l + 0.044 0.407 4 1.2 4.8 iron sulfate
heptahydrate 5 g/l 10 A Potassium hexafluorozirconate 12.5 g/l +
0.044 0.396 6 1.6 9.6 copper sulfate pentahydrate 5 g/l 11 A
Potassium hexafluorozirconate 6.5 g/l + 0.023 1.383 6 1.6 9.6
vanadium chloride 5 g/l 12 A Potassium hexafluorozirconate 12.5 g/l
+ 0.044 0.397 5 1.6 8.0 zinc sulfate heptahydrate 5 g/l 13 A
Potassium hexafluorozirconate 12.5 g/l + 0.044 0.470 6 1.6 9.6
manganese sulfate pentahydrate 5 g/l Corrosion-resistant coating
Adhesive coating Coating weight of Ni Coating Additive Mass Coated
steel and Sn (mg/m.sup.2) weight of element ratio sheet No. Ni Sn
Zr (mg/m.sup.2) M M/Zr Remarks 1 290 0 60 -- 0 Comparative example
2 295 0 20 Co 0.10 Example 3 295 0 60 Co 1.20 Example 4 295 0 100
Co 1.30 Example 5 295 0 60 Co 0.10 Example 6 295 0 100 Co 0.10
Example 7 295 0 20 Fe, Co 1.20 Example 8 295 0 60 Fe 0.11 Example 9
295 0 20 Fe 0.10 Example 10 300 0 20 Cu 0.10 Example 11 295 0 20 V
0.15 Example 12 295 0 60 Zn 0.12 Example 13 300 0 20 Mn 0.10
Example
TABLE-US-00003 TABLE 3 Coating Cathodic electrolysis treatment Zr
amount Molar ratio Current Electric Coated steel Coating in bath of
metal M density Electrolysis charge density sheet No. method
Treatment bath composition (mol/l) to Zr in bath (A/dm.sup.2) time
(sec) (C/dm.sup.2) 14 B Potassium hexafluorozirconate 0.044 0.403 5
1.2 6.0 12.5 g/l + cobalt sulfate heptahydrate 5 g/l 15 B Potassium
hexafluorozirconate 0.044 1.222 3 1.6 4.8 12.5 g/l + iron sulfate
heptahydrate 15 g/l 16 B Potassium hexafluorozirconate 12.5 g/l
0.044 0 3 2.0 6.0 17 C Potassium hexafluorozirconate 0.044 2.419 5
1.2 6.0 12.5 g/l + cobalt sulfate heptahydrate 30 g/l 18 C
Potassium hexafluorozirconate 0.044 1.222 3 1.6 4.8 12.5 g/l + iron
sulfate heptahydrate 15 g/l 19 C Potassium hexafluorozirconate 12.5
g/l 0.044 0 3 2.0 6.0 20 C Potassium hexafluorozirconate 0.044
2.419 9 1.2 10.8 12.5 g/l + cobalt sulfate heptahydrate 30 g/l 21 C
Potassium hexafluorozirconate 0.044 1.222 5 1.2 6.0 12.5 g/l + iron
sulfate heptahydrate 15 g/l 22 C Potassium hexafluorozirconate 12.5
g/l 0.044 0 3 2.0 6.0 Corrosion-resistant coating Ni, Sn, net
coating weight of remaining Sn (mg/m.sup.2) Adhesive coating Net
coating Coating Additive Mass Coated steel weight of weight of
element ratio sheet No. Ni Sn remaining Sn Zr (mg/m.sup.2) M M/Zr
Remarks 14 80 0 0 60 Co 0.10 Example 15 80 0 0 60 Fe 1.00 Example
16 80 0 0 60 -- 0 Comparative example 17 80 150 25 60 Co 3.00
Example 18 80 300 50 60 Fe 1.00 Example 19 80 300 50 60 -- 0
Comparative example 20 80 500 70 60 Co 3.00 Example 21 80 500 70 60
Fe 1.00 Example 22 80 500 70 60 -- 0 Comparative example
TABLE-US-00004 TABLE 4 Coating Cathodic electrolysis treatment Zr
amount Molar ratio Current Electric Coated steel Coating in bath of
metal M density Electrolysis charge density sheet No. method
Treatment bath composition (mol/l) to Zr in bath (A/dm.sup.2) time
(sec) (C/dm.sup.2) 23 D Potassium hexafluorozirconate 0.044 1.209 8
1.2 9.6 12.5 g/l + cobalt sulfate heptahydrate 15 g/l 24 D
Potassium hexafluorozirconate 0.044 1.209 6 2.0 12.0 12.5 g/l +
cobalt sulfate heptahydrate 15 g/l 25 D Potassium
hexafluorozirconate 0.044 1.209 7 1.6 11.2 12.5 g/l + cobalt
sulfate heptahydrate 15 g/l 26 D Potassium hexafluorozirconate
0.044 0.407 5 1.2 6.0 12.5 g/l + iron sulfate heptahydrate 5 g/l 27
D Potassium hexafluorozirconate 0.044 0.861 6 2.0 12.0 12.5 g/l +
nickel sulfate hexahydrate 10 g/l 28 D Potassium
hexafluorozirconate 0.044 0.892 8 1.2 9.6 12.5 g/l + iron chloride,
anhydrous 5 g/l 29 D Potassium hexafluorozirconate 0.044 0 4 1.2
4.8 12.5 g/l 30 None (on Potassium hexafluorozirconate 0.044 1.209
5 1.2 6.0 steel sheet) 12.5 g/l + cobalt sulfate heptahydrate 15
g/l 31 None (on Potassium hexafluorozirconate 0.044 0.407 3 1.6 4.8
steel sheet) 12.5 g/l + iron sulfate heptahydrate 5 g/l
Corrosion-resistant coating Ni, Sn, net coating weight of remaining
Sn (mg/m.sup.2) Adhesive coating Net coating Coating Additive Mass
Coated steel weight of weight of element ratio sheet No. Ni Sn
remaining Sn Zr (mg/m.sup.2) M M/Zr Remarks 23 0 2000 1500 60 Co
1.80 Example 24 0 700 300 100 Co 1.80 Example 25 0 500 70 20 Co
1.80 Example 26 0 500 70 60 Fe 0.80 Example 27 0 500 70 60 Ni 0.05
Example 28 0 1500 900 60 Fe 0.80 Example 29 0 700 300 60 -- 0
Comparative example 30 -- -- -- 60 Co 1.80 Comparative example 31
-- -- -- 60 Fe 0.80 Comparative example
TABLE-US-00005 TABLE 5 Coating Cathodic electrolysis treatment Ti
amount Molar ratio Current Electric Coated steel Coating in bath of
metal M density Electrolysis charge density sheet No. method
Treatment bath composition (mol/l) to Ti in bath (A/dm.sup.2) time
(sec) (C/dm.sup.2) 32 A Potassium fluorotitanate 0.044 0.719 6 2.0
12 10.6 g/l + vanadium chloride 5 g/l 33 A Potassium fluorotitanate
0.044 0.470 6 2.0 12 10.6 g/l + manganese sulfate pentahydrate 5
g/l Corrosion-resistant coating Ni, Sn, net coating weight of
remaining Sn (mg/m.sup.2) Adhesive coating Net coating Coating
Additive Mass Coated steel weight of weight of element ratio sheet
No. Ni Sn remaining Sn Ti (mg/m.sup.2) M M/Ti Remarks 32 295 0 0 20
V 0.15 Comparative example 33 300 0 0 20 Mn 0.10 Comparative
example
TABLE-US-00006 TABLE 6 Humid Streaky Laminated steel resin
adhesion: Corrosion surface sheet No. peel length (mm) resistance
defects Remarks 1 50 .smallcircle. .smallcircle. Comparative
example 2 19 .smallcircle. .smallcircle. Example 3 18 .smallcircle.
.smallcircle. Example 4 18 .smallcircle. .smallcircle. Example 5 19
.smallcircle. .smallcircle. Example 6 19 .smallcircle.
.smallcircle. Example 7 17 .smallcircle. .smallcircle. Example 8 18
.smallcircle. .smallcircle. Example 9 19 .smallcircle.
.smallcircle. Example 10 19 .smallcircle. .smallcircle. Example 11
18 .smallcircle. .smallcircle. Example 12 19 .smallcircle.
.smallcircle. Example 13 19 .smallcircle. .smallcircle. Example 14
17 .smallcircle. .smallcircle. Example 15 19 .smallcircle.
.smallcircle. Example 16 50 .smallcircle. .smallcircle. Comparative
example 17 17 .smallcircle. .smallcircle. Example 18 17
.smallcircle. .smallcircle. Example 19 70 .smallcircle.
.smallcircle. Comparative example 20 18 .smallcircle. .smallcircle.
Example 21 19 .smallcircle. .smallcircle. Example 22 70
.smallcircle. .smallcircle. Comparative example 23 19 .smallcircle.
.smallcircle. Example 24 18 .smallcircle. .smallcircle. Example 25
17 .smallcircle. .smallcircle. Example 26 18 .smallcircle.
.smallcircle. Example 27 18 .smallcircle. .smallcircle. Example 28
18 .smallcircle. .smallcircle. Example 29 70 .smallcircle.
.smallcircle. Comparative example 30 17 x .smallcircle. Comparative
example 31 17 x .smallcircle. Comparative example 32 19
.smallcircle. x Comparative example 33 19 .smallcircle. x
Comparative example
Example 2
[0061] Corrosion-resistant coatings are formed on both surfaces of
each cold-rolled steel sheet (thickness: 0.2 mm), which is made of
cold-rolled low-carbon steel used to produce a tin-free steel sheet
(TFS), using coating bath a or b shown in Table 1, by one of the
methods A to D described above. In the methods C and D, Sn coating
is partially alloyed by the melting treatment. The net amount of
remaining Sn which remains without being alloyed is shown in Tables
7 to 9.
[0062] Then, by performing cathodic electrolysis under the cathodic
electrolysis conditions shown in Tables 7 to 9, followed by drying,
adhesive coatings are disposed on the corrosion resistant coatings
on both surfaces of each of the steel sheets. Thereby, coated steel
sheets Nos. 34 to 49 are produced. In this case, the pH of the
cathodic electrolysis bath is adjusted by an alkali solution, such
as potassium hydroxide, or an acid solution, such as sulfuric acid.
Furthermore, in coated steel sheets Nos. 34 to 45, a pulsed current
is used, and the current density at which Zr is not deposited is
set at 0 A/dm.sup.2. On the other hand, in coated steel sheets Nos.
46 and 47, a pulsed current is used, and on the basis of the
results shown in FIG. 1, an example in which the current density at
which Zr is not deposited is not 0 A/dm.sup.2 (No. 46) and an
example in which the current density at which Zr is not deposited
exceeds the upper limit (No. 47) are taken. Out of these coated
steel sheets, in Nos. 38, 45, and 47, the cathodic electrolysis
conditions are out of the preferred pulsed current conditions. Nos.
48 and 49 are comparative examples, in which cathodic electrolysis
is performed in an aqueous solution containing Ti instead of
Zr.
[0063] The Ni coating weight and Sn coating weight in each
corrosion-resistant coating and the Zr coating weight and Ti
coating weight in each adhesive coating are determined by X-ray
fluorescence analysis in comparison with a calibration sample in
which the content of each metal is determined by chemical analysis
in advance. Furthermore, regarding Co, Fe, V, and Mn, the coating
weights are determined by a method appropriately selected from
X-ray fluorescence analysis, the same technique as that used for Zr
and Ti, chemical analysis, Auger electron spectroscopy analysis,
and secondary ion mass spectrometry. Furthermore, the presence of O
can be confirmed by XPS surface analysis in each of Nos. 34 to
49.
[0064] Both surfaces of each of the coated steel sheets Nos. 34 to
49 are laminated as in Example 1 to produce laminated steel sheet
Nos. 34 to 49. Regarding the resulting laminated steel sheet Nos.
34 to 49, humid resin adhesion, corrosion resistance, and streaky
surface defects are evaluated as in Example 1.
[0065] The results are shown in Table 10. In all of laminated steel
sheet Nos. 34 to 47 using the coated steel sheets which are
examples of the present invention, good humid resin adhesion and
corrosion resistance are exhibited, and no streaky surface defects
are observed. In Nos. 34 to 37, 39 to 44, and 46, in which cathodic
electrolysis is performed under the electrolysis conditions, using
an electric current having a current density that changes with a
cycle of 0.01 to 0.4 seconds and having a period of 0.005 to 0.2
seconds per cycle during which Zr is not deposited, in which the
number of cycles is 10 or more and the total electric charge
density at the current density at which Zr is deposited is 3 to 20
C/dm.sup.2, the peel length of humid resin adhesion is 15 mm or
less, and particularly good humid resin adhesion can be obtained.
In contrast, in laminated steel sheet Nos. 48 and 49, which are
comparative examples, although good humid resin adhesion and
corrosion resistance are exhibited, streaky surface defects are
observed.
TABLE-US-00007 TABLE 7 Cathodic electrolysis Electrolysis
conditions* Period per Coated Treatment bath cycle during Total
electric steel Coating Amount Molar ratio Current which current
Number charge density sheet treatment of Zr of metal M density 2
Cycle density 2 is of cycles at current No. Method Composition and
pH (mol/l) to Zr (A/dm.sup.2) (sec) maintained (sec) (No.) density
1 (C/dm.sup.2) 34 A Potassium hexafluorozirconate 0.044 0.403 0 0.1
0.05 15 3.0 12.5 g/l + cobalt sulfate heptahydrate 5 g/l pH 4 35 A
Potassium hexafluorozirconate 0.044 0.403 0 0.09 0.04 15 4.0 12.5
g/l + cobalt sulfate heptahydrate 5 g/l pH 4 36 A Potassium
hexafluorozirconate 0.044 1.222 0 0.1 0.05 15 3.0 12.5 g/l + iron
sulfate heptahydrate 15 g/l pH 4.2 37 A Potassium
hexafluorozirconate 0.044 0.407 0 0.05 0.03 20 5.0 12.5 g/l + iron
sulfate heptahydrate 5 g/l + cobalt sulfate heptahydrate 4 g/l pH
4.1 38 A Potassium hexafluorozirconate 0.044 0.403 0 0.7 0.40 4 6.0
12.5 g/l + cobalt sulfate heptahydrate 5 g/l pH 4 39 B Potassium
hexafluorozirconate 0.044 0.403 0 0.1 0.05 15 3.0 12.5 g/l + cobalt
sulfate heptahydrate 5 g/l pH 4 40 C Potassium hexafluorozirconate
0.044 0.403 0 0.1 0.05 15 3.0 12.5 g/l + cobalt sulfate
heptahydrate 5 g/l pH 4 Corrosion-resistant coating Ni, Sn, net
coating weight Coated of remaining Sn (mg/m.sup.2) Adhesive coating
steel Net coating Coating Additive Mass sheet weight of weight of
element ratio No. Ni Sn remaining Sn Zr (mg/m.sup.2) M M/Zr Remarks
34 295 0 0 40 Co 1.22 Example 35 295 0 0 60 Co 1.46 Example 36 295
0 0 50 Fe 0.86 Example 37 295 0 0 30 Fe, Co 1.67 Example 38 295 0 0
60 Co 0.10 Example 39 70 0 0 40 Co 1.22 Example 40 70 100 0 40 Co
1.22 Example *Current density 1: current density at which Zr is
deposited, Current density 2: current density at which Zr is not
deposited
TABLE-US-00008 TABLE 8 Cathodic electrolysis Electrolysis
conditions* Period per Coated Treatment bath cycle during Total
electric steel Coating Amount Molar ratio Current which current
Number charge density sheet treatment of Zr of metal M density 2
Cycle density 2 is of cycles at current No. Method Composition and
pH (mol/l) to Zr (A/dm.sup.2) (sec) maintained (sec) (No.) density
1 (C/dm.sup.2) 41 D Potassium hexafluorozirconate 0.044 0.403 0 0.1
0.05 15 3.0 12.5 g/l + cobalt sulfate heptahydrate 5 g/l pH 4 42 D
Potassium hexafluorozirconate 0.044 0.403 0 0.09 0.04 15 4.0 12.5
g/l + cobalt sulfate heptahydrate 5 g/l pH 4 43 D Potassium
hexafluorozirconate 0.044 1.222 0 0.1 0.05 15 3.0 12.5 g/l + iron
sulfate heptahydrate 15 g/l pH 4.2 44 D Potassium
hexafluorozirconate 0.044 0.729 0 0.05 0.03 20 5.0 12.5 g/l + iron
sulfate heptahydrate 5 g/l + cobalt sulfate heptahydrate 4 g/l pH
4.1 45 D Potassium hexafluorozirconate 0.044 0.407 0 0.70 0.40 4
6.0 12.5 g/l + iron sulfate heptahydrate 5 g/l pH 4.2
Corrosion-resistant coating Ni, Sn, net coating weight Coated of
remaining Sn (mg/m.sup.2) Adhesive coating steel Net coating
Coating Additive Mass sheet weight of weight of Zr element ratio
No. Ni Sn remaining Sn (mg/m.sup.2) M M/Zr Remarks 41 0 500 70 40
Co 1.22 Example 42 0 700 300 60 Co 1.46 Example 43 0 500 0 50 Fe
0.86 Example 44 0 500 30 30 Fe, Co 1.67 Example 45 0 500 70 60 Fe
0.80 Example *Current density 1: current density at which Zr is
deposited, Current density 2: current density at which Zr is not
deposited
TABLE-US-00009 TABLE 9 Cathodic electrolysis Electrolysis
conditions* Period per Coated Treatment bath cycle during Total
electric steel Coating Amount Molar ratio Current which current
Number charge density sheet treatment of Zr(Ti) of metal M density
2 Cycle density 2 is of cycles at current No. Method Composition
and pH (mol/l) to Zr (Ti) (A/dm.sup.2) (sec) maintained (sec) (No.)
density 1 (C/dm.sup.2) 46 A Potassium hexafluorozirconate 0.044
0.403 0.5 0.1 0.05 15 3.0 12.5 g/l + cobalt sulfate heptahydrate 5
g/l pH 4 47 A Potassium hexafluorozirconate 0.044 0.403 3.5 0.1
0.05 15 3.0 12.5 g/l + cobalt sulfate heptahydrate 5 g/l pH 4 48 A
Potassium fluorotitanate (0.044) (0.931) 0.sup. 0.9 0.40 4 12.0
10.6 g/l + vanadium chloride 5 g/l pH 3.5 49 A Potassium
fluorotitanate (0.044) (0.531) 0.sup. 0.9 0.40 4 12.0 10.6 g/l +
manganese sulfate pentahydrate 5 g/l pH 3.5 Corrosion-resistant
coating Ni, Sn, net coaring weight Adhesive coating Coated of
remaining Sn (mg/m.sup.2) Coating steel Net coating weight of
Additive Mass sheet weightt of Zr(Ti) element ratio No. Ni Sn
remaining Sn (mg/m.sup.2) M M/Zr(Ti) Remarks 46 295 0 0 40 Co 1.22
Example 47 295 0 0 40 Co 1.22 Example 48 295 0 0 20 V 0.15
Comparative example 49 300 0 0 20 Mn 0.10 Comparative example
*Current density 1: current density at which Zr(Ti) is deposited,
Current density 2: current density at which Zr(Ti) is not
deposited
TABLE-US-00010 TABLE 10 Humid Streaky Laminated steel resin
adhesion: Corrosion surface sheet No. peel length (mm) resistance
defects Remarks 34 15 .smallcircle. .smallcircle. Example 35 14
.smallcircle. .smallcircle. Example 36 14 .smallcircle.
.smallcircle. Example 37 15 .smallcircle. .smallcircle. Example 38
19 .smallcircle. .smallcircle. Example 39 14 .smallcircle.
.smallcircle. Example 40 15 .smallcircle. .smallcircle. Example 41
15 .smallcircle. .smallcircle. Example 42 14 .smallcircle.
.smallcircle. Example 43 14 .smallcircle. .smallcircle. Example 44
15 .smallcircle. .smallcircle. Example 45 18 .smallcircle.
.smallcircle. Example 46 14 .smallcircle. .smallcircle. Example 47
19 .smallcircle. .smallcircle. Example 48 8 .smallcircle. x
Comparative example 49 9 .smallcircle. x Comparative example
Example 3
[0066] Corrosion-resistant coatings are formed on both surfaces of
each cold-rolled steel sheet (thickness: 0.2 mm), which is made of
cold-rolled low-carbon steel used to produce a tin-free steel sheet
(TFS), using coating bath a or b shown in Table 1, by one of the
methods A to D described above. In the methods C and D, Sn coating
is partially alloyed by the heat melting treatment. The net coating
weight of remaining Sn which remains without being alloyed is shown
in Tables 11 and 12.
[0067] Then, by performing cathodic electrolysis under the cathodic
electrolysis conditions shown in Tables 11 and 12, followed by
drying, adhesive coatings are formed on the corrosion resistant
coatings disposed on both surfaces of each of the steel sheets.
Thereby, coated steel sheets Nos. 50 to 60 are produced. In this
case, the pH of the coating bath is adjusted by an alkali solution,
such as potassium hydroxide, or an acid solution, such as sulfuric
acid. Furthermore, in coated steel sheets Nos. 54 to 60, a pulsed
current is used, and the current density at which Zr is not
deposited is set at 0 A/dm.sup.2. Furthermore, as the phenolic
resin in the coating bath, a phenolic resin with a weight-average
molecular weight of 5,000 is used.
[0068] The Ni coating weight and Sn coating weight in each
corrosion-resistant coating and the Zr coating weight in each
adhesive coating are determined by X-ray fluorescence analysis in
comparison with a calibration sample in which the content of each
metal is determined by chemical analysis in advance. Furthermore,
regarding Co and P, the contents are determined by a method
appropriately selected from X-ray fluorescence analysis, the same
technique as that used for Zr, chemical analysis, Auger electron
spectroscopy analysis, and secondary ion mass spectrometry, and the
mass ratio of Co and P to Zr is evaluated. Furthermore, the
presence of O can be confirmed by XPS surface analysis in each of
Nos. 50 to 60. Furthermore, the C content in the adhesive coating
is obtained by subtracting the C content in the steel sheet as a
background from the total C content measured by gas
chromatography.
[0069] Both surfaces of each of the coated steel sheets Nos. 50 to
60 are laminated as in Example 1 to produce laminated steel sheet
Nos. 50 to 60. Regarding the resulting laminated steel sheet Nos.
50 to 60, humid resin adhesion, corrosion resistance, and streaky
surface defects are evaluated as in Example 1.
[0070] The results are shown in Table 13. In all of laminated steel
sheet Nos. 50 to 60 which are examples of the present invention,
good humid resin adhesion and corrosion resistance are exhibited,
and no streaky surface defects are observed. In Nos. 54 to 60, in
which cathodic electrolysis is performed using a pulsed current,
the peel length of humid resin adhesion is 15 mm or less, and
particularly good humid resin adhesion can be obtained. In adhesive
coatings containing Zr, point rust may be observed in portions
other than the cut portion after the corrosion resistance test in
some cases. However, when P derived from a phosphoric acid or C
derived from a phenolic resin is incorporated into coatings as in
the examples of the present invention, no point rust is
observed.
TABLE-US-00011 TABLE 11 Cathodic electrolysis electrolysis
conditions Treatment bath Electric Coating Amount Molar ratio
Current charge Coated steel treatment of Zr of metal M density
Electrolysis density sheet No. Method Composition (mol/l) to Zr
(A/dm.sup.2) time (sec) (C/dm.sup.2) 50 A Potassium
hexafluorozirconate 12.5 g/l + cobalt 0.044 0.403 7 1.5 10.5
sulfate heptahydrate 5 g/l + orthophosphoric acid1 g/l 51 C
Potassium hexafluorozirconate 12.5 g/l + cobalt 0.044 0.403 7 1.5
10.5 sulfate heptahydrate 5 g/l + orthophosphoric acid1 g/l 52 B
Potassium hexafluorozirconate 12.5 g/l + cobalt 0.044 0.403 7 1.5
10.5 sulfate heptahydrate 5 g/l + orthophosphoric acid1 g/l +
phenolic resin0.5 g/l 53 D Potassium hexafluorozirconate 12.5 g/l +
cobalt 0.044 0.403 6 1.5 9.0 sulfate heptahydrate 5 g/l +
orthophosphoric acid1 g/l + phenolic resin0.9 g/l
Corrosion-resistant coating Ni, Sn, net coating weight of remaining
Sn (mg/m.sup.2) Adhesive coating Net coating Coating Additive Mass
Mass Mass Coated steel weight of weight of element ratio ratio
ratio sheet No. Ni Sn remaining Sn Zr (mg/m.sup.2) M M/Zr P/Zr C/Zr
Remarks 50 300 0 0 10 Co 2.00 0.4 -- Example 51 80 150 25 30 Co
2.00 0.1 -- Example 52 70 0 0 30 Co 2.00 0.1 0.1 Example 53 0 500 0
5 Co 2.00 0.7 0.8 Example
TABLE-US-00012 TABLE 12 Cathodic electrolysis Electrolysis
conditioons* Period per Treatment bath cycle during Total electric
Molar which current charge density Coated Coating Amount ratio of
Current density 2 is Number at current steel treatment of Zr metal
M density 2 Cycle maintained of cycles density 1 sheet No. Method
Composition (mol/l) to Zr (A/dm.sup.2) (sec) (sec) (No.)
C/dm.sup.2) 54 A Potassium hexafluorozirconate 0.044 0.403 0 0.1
0.05 15 3.0 12.5 g/l + cobalt sulfate heptahydrate 5 g/l +
orthophosphoric acid1 g/l 55 D Potassium hexafluorozirconate 0.044
0.403 0 0.1 0.05 15 3.0 12.5 g/l + cobalt sulfate heptahydrate 5
g/l + orthophosphoric acid1 g/l 56 A Potassium hexafluorozirconate
0.044 0.403 0 0.1 0.05 25 4.0 12.5 g/l + cobalt sulfate
heptahydrate 5 g/l + orthophosphoric acid1 g/l + phenolic resin0.9
g/l 57 B Potassium hexafluorozirconate 0.044 0.403 0 0.1 0.05 15
3.0 12.5 g/l + cobalt sulfate heptahydrate 5 g/l + orthophosphoric
acid1 g/l + phenolic resin0.9 g/l 58 C Potassium
hexafluorozirconate 0.044 0.403 0 0.1 0.05 15 3.0 12.5 g/l + cobalt
sulfate heptahydrate 5 g/l + orthophosphoric acid g/l + phenolic
resin0.9 g/l 59 D Potassium hexafluorozirconate 0.044 0.403 0 0.1
0.05 25 4.0 12.5 g/l + cobalt sulfate heptahydrate 5 g/l +
orthophosphoric acid1 g/l + phenolic resin0.5 g/l Potassium
hexafluorozirconate 60 D 12.5 g/l + cobalt sulfate 0.044 0.403 0
0.1 0.05 15 3.0 heptahydrate 5 g/l + orthophosphoric acid1 g/l +
phenolic resin0.9 g/l Corrosion-resistant coating Ni, Sn, net
coating weight of remaining Sn (mg/m.sup.2) Adhesive coating net
coating Coating Coated weight of weight of Additive Mass Mass Mass
steel remaining Zr element ratio ratio ratio sheet No. Ni Sn Sn
(mg/m.sup.2) M M/Zr P/Zr C/Zr Remarks 54 300 0 0 30 Co 1.67 0.4 --
Example 55 0 500 0 8 Co 2.00 0.5 -- Example 56 300 0 0 12 Co 2.00
0.3 0.3 Example 57 70 0 0 8 Co 2.00 0.5 0.5 Example 58 70 700 200 8
Co 2.00 0.5 0.5 Example 59 0 500 0 12 Co 2.00 0.3 0.3 Example 60 0
800 200 8 Co 2.00 0.5 0.5 Example *Current density 1: current
density at which Zr is deposited, Current density 2: current
density at which Zr is not deposited
TABLE-US-00013 TABLE 13 Humid Streaky Laminated steel resin
adhesion: Corrosion surface sheet No. peel length (mm) resistance
defects Remarks 50 17 .smallcircle. .smallcircle. Example 51 17
.smallcircle. .smallcircle. Example 52 19 .smallcircle.
.smallcircle. Example 53 17 .smallcircle. .smallcircle. Example 54
12 .smallcircle. .smallcircle. Example 55 13 .smallcircle.
.smallcircle. Example 56 12 .smallcircle. .smallcircle. Example 57
12 .smallcircle. .smallcircle. Example 58 15 .smallcircle.
.smallcircle. Example 59 12 .smallcircle. .smallcircle. Example 60
15 .smallcircle. .smallcircle. Example
[0071] According to the present invention, it is possible to
produce, even without using Cr which is strictly environmentally
regulated, a coated steel sheet which has excellent humid resin
adhesion and corrosion resistance and in which streaky surface
defects do not occur. The coated steel sheet of the present
invention can be used without any problem as an alternative
material to replace conventional tin-free steel sheets and can be
used, without being coated with a resin, for containers which
contain oil, organic solvents, paint, or the like. Furthermore,
when the coated steel sheet is coated with a resin to obtain a
resin-coated steel sheet and the resin-coated steel sheet is formed
into cans or can lids, and even when the cans or can lids are
exposed to a retort atmosphere, the resin does not peel off.
Furthermore, at resin peel-off portions, such as scratches, the
amount of dissolving out of Fe of a base steel sheet is markedly
small, and very good corrosion resistance is exhibited. Therefore,
the present invention can greatly contribute to the industry.
REFERENCE SIGNS LIST
[0072] 1 steel sheet [0073] 2 film [0074] 3 cut portion of steel
sheet [0075] 4 weight [0076] 5 peel length
* * * * *