U.S. patent application number 15/030228 was filed with the patent office on 2016-08-18 for chemical conversion treatment solution and chemically converted steel sheet.
The applicant listed for this patent is NISSHIN STEEL CO., LTD.. Invention is credited to Yoshiharu IWAMIZU, Masanori MATSUNO, Atsuo SHIMIZU, Masaya YAMAMOTO.
Application Number | 20160237572 15/030228 |
Document ID | / |
Family ID | 53057103 |
Filed Date | 2016-08-18 |
United States Patent
Application |
20160237572 |
Kind Code |
A1 |
IWAMIZU; Yoshiharu ; et
al. |
August 18, 2016 |
CHEMICAL CONVERSION TREATMENT SOLUTION AND CHEMICALLY CONVERTED
STEEL SHEET
Abstract
A chemically converted steel sheet having a chemically converted
coating film is made by coating a Zn-based plated steel sheet with
a chemical conversion treatment solution and drying the same. The
chemically converted coating film is constituted by a first
chemically converted layer including V, Mo, and P, and a second
chemically converted layer provided on said layer and including a
group 4A metal oxygen acid salt, and the ratio of pentavalent V to
all the Vs in the chemically converted coating film is 0.7 or
greater. The chemical conversion treatment solution includes
specific proportions of V, Mo, an amine, the group 4A metal oxygen
acid salt, and P, and substantially does not include hydrophilic
resins, fluorine, or silicon.
Inventors: |
IWAMIZU; Yoshiharu; (Chiba,
JP) ; SHIMIZU; Atsuo; (Osaka, JP) ; MATSUNO;
Masanori; (Osaka, JP) ; YAMAMOTO; Masaya;
(Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NISSHIN STEEL CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
53057103 |
Appl. No.: |
15/030228 |
Filed: |
November 14, 2014 |
PCT Filed: |
November 14, 2014 |
PCT NO: |
PCT/JP2014/005750 |
371 Date: |
April 18, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 2/06 20130101; C23C
2222/20 20130101; C23C 22/60 20130101 |
International
Class: |
C23C 22/60 20060101
C23C022/60 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 14, 2013 |
JP |
2013-235543 |
Nov 14, 2014 |
JP |
2014-231275 |
Claims
1. A chemical treatment solution for coating a zinc-based plated
steel sheet having a zinc-based plating layer containing 0.1 to
22.0 mass % of aluminum, the chemical treatment solution
comprising: a water-soluble molybdate; a vanadium salt; an amine; a
group 4A metal oxoate; and a phosphate compound, wherein: a molar
ratio of molybdenum to vanadium in the chemical treatment solution
is 0.4 to 5.5, a molar ratio of the amine to the vanadium in the
chemical treatment solution is 0.3 or more, a content of a
hydrophilic resin in the chemical treatment solution is at most 100
mass % based on a total amount of the vanadium and the molybdenum
in the chemical treatment solution, a total content of fluorine
derived from a fluorine ion or a fluorometal ion in the chemical
treatment solution is at most 30 mass % based on the total amount
of the vanadium and the molybdenum in the chemical treatment
solution, and a content of silicon derived from a silanol group in
the chemical treatment solution is at most 50 mass % based on the
total amount of the vanadium and the molybdenum in the chemical
treatment solution.
2. The chemical treatment solution according to claim 1, wherein
the amine has a molecular weight of 80 or less.
3. A chemically treated steel sheet comprising: a zinc-based plated
steel sheet having a zinc-based plating layer containing 0.1 to
22.0 mass % of aluminum, and a chemical conversion film disposed on
the zinc-based plating layer, wherein: the chemical conversion film
includes a first chemical conversion layer disposed on a surface of
the zinc-based plating layer and containing vanadium, molybdenum
and phosphorus, and a second chemical conversion layer disposed on
the first chemical conversion layer and containing a group 4A metal
oxoate, and a percentage of pentavalent vanadium based on
mixed-valent vanadium in the chemical conversion film is 0.7 or
more.
4. The chemically treated steel sheet according to claim 3,
wherein: the group 4A metal oxoate is a zirconium oxoate, and the
chemical conversion film contains 1 to 60 parts by mass of
molybdenum, 2 to 20 parts by mass of vanadium, and 10 to 50 parts
by mass of phosphorus, based on 100 parts by mass of zirconium.
5. The chemically treated steel sheet according to claim 3, wherein
the zinc-based plated steel sheet is a hot-dip aluminum- and
magnesium-containing zinc plated steel sheet having a hot-dip
aluminum- and magnesium-containing zinc plating layer containing
0.1 to 22.0 mass % of aluminum and 1.5 to 10.0 mass % of
magnesium.
6. The chemically treated steel sheet according to claim 4, wherein
the zinc-based plated steel sheet is a hot-dip aluminum- and
magnesium-containing zinc plated steel sheet having a hot-dip
aluminum- and magnesium-containing zinc plating layer containing
0.1 to 22.0 mass % of aluminum and 1.5 to 10.0 mass % of magnesium.
Description
TECHNICAL FIELD
[0001] The present invention relates to a chemically treated steel
sheet, and a chemical treatment solution for a zinc-based plated
steel sheet.
BACKGROUND ART
[0002] Zinc-based plated steel sheets have been used in wide
applications such as automobiles, building materials, and home
electric appliances. Typically, the surface of a plated steel sheet
is subjected to a chromium-free chemical treatment for imparting
corrosion resistance without oiling. The chromium-free chemical
treatment is roughly divided into organic treatments and inorganic
treatments. The organic treatments allow a thick film containing an
organic resin to be formed, whereas the inorganic treatments allow
a thin film (film thickness: 1 .mu.m or less) to be formed for
obtaining spot weldability. The organic treatments can impart
relatively high corrosion resistance compared to the inorganic
treatments. Some of the inorganic treatments also exhibit high
corrosion resistance in the same degree as the organic treatments
by using a zinc-based plated steel sheet containing aluminum and
magnesium in its plating layer as an original sheet for chemical
treatment.
[0003] As the inorganic treatment, for example, titanium-based,
zirconium-based, molybdenum-based, and their complex-based
inorganic treatments have been developed depending on the
difference in corrosion inhibitors. Further, in order to enhance
corrosion resistance, inorganic treatments to which a silane
coupling agent, silica sol, an organic acid, or the like is further
added have also been developed (see, e.g., PTLs 1 to 3).
[0004] PTL 1 discloses a chemically treated steel sheet obtained by
forming a chromium-free chemical conversion film containing a valve
metal and a soluble fluoride of the valve metal on the surface of a
zinc-based plated steel sheet. PTL 2 discloses a chemically treated
steel sheet obtained by forming a chromium-free chemical conversion
film containing: a zirconium compound, a vanadyl compound (salt of
VO.sup.2+), and the like; an organic acid; a silica compound; a
fluoride; a lubricant; or the like on the surface of a
Magnesium-Aluminum-Silicon-containing zinc-based plated steel
sheet. PTL 3 discloses a chemically treated steel sheet obtained by
forming a chromium-free chemical conversion film containing a basic
zirconium compound, a vanadyl compound, a phosphate compound, a
cobalt compound, an organic acid, or the like on the surface of a
zinc-based plated steel sheet.
[0005] As disclosed in PTLs 1 to 3, chromium-free chemical
treatments in which corrosion inhibitors are complexed, and an
organic acid, a fluoride, a silane coupling agent, or the like is
added for the enhancement of the functionality of the chromium-free
chemical conversion film, and which can impart more excellent
corrosion resistance of the film than that of the film obtained by
the conventional chromate treatments. However, when the chemically
treated steel sheet obtained by forming the chromium-free chemical
conversion film on the surface of the zinc-based plated steel sheet
is stored for a long period of time under high temperature and
humid environment, the chemically treated steel sheet sometimes has
a blacked surface of a plating layer due to oxidization. The
blackening of the surface of the plating layer not only lowers the
design but also cause adverse influences such as lowering of spot
weldability. This phenomenon is remarkably apparent particularly in
the zinc-based plated steel sheet containing aluminum and magnesium
in its plating layer.
[0006] As a means for suppressing the blackening of the zinc-based
plated steel sheet, PTL 4 proposes an organic chemical treatment in
which a hexavalent molybdenum oxoate and an amine coexist.
According to the technique of PTL 4, an amine forms a complex with
molybdenum oxo-acid to suppress the reaction of the molybdenum
oxoate with a zinc alloy plating layer, and thus a pentavalent or
hexavalent molybdenum complex oxoate (so-called "molybdenum blue")
is formed in the chemical conversion film. The pentavalent
molybdenum oxoate in the chemical conversion film becomes the
hexavalent molybdenum oxoate through the reaction with oxygen which
permeates the film. In this manner, the pentavalent molybdenum
oxoate in the chemical conversion film traps oxygen which permeates
the film, so that the oxidation of the surface of the plating layer
is suppressed, and as a result the blackening is also
suppressed.
CITATION LIST
Patent Literature
PTL 1
Japanese Patent Application Laid-Open No. 2002-194558
PTL 2
Japanese Patent Application Laid-Open No. 2003-055777
PTL 3
WO2007/123276
PTL 4
Japanese Patent Application Laid-Open No. 2005-146340
SUMMARY OF INVENTION
Technical Problem
[0007] In order to impart high corrosion resistance to a chemically
treated steel sheet, it is necessary to dry a chemical treatment
solution applied to the surface of the steel sheet sufficiently to
form an insoluble film. When the drying temperature is low and
drying is insufficient, corrosion resistance is remarkably lowered.
Therefore, when the chemically treated steel sheet is produced in a
continuous line, it is necessary to dry the chemical treatment
solution at a high temperature of a steel sheet temperature of
about 50 to 200.degree. C., from the viewpoint of both achieving
sufficient drying and productivity.
[0008] Recently, CO.sub.2 elimination as a countermeasure for
global warming and power saving as a countermeasure for power
shortage have been required. In particular, in order to cope with
Scope 3, products have been required, which contribute to CO.sub.2
elimination even in the stage in which raw materials for the
products are produced. Accordingly, also in the chromium-free
chemical treatment, it has been required to lower the drying
temperature and reduce the drying time.
[0009] The present invention has been achieved in light of the
above-mentioned respects, and an object of the present invention is
to provide a chemically treated steel sheet which is excellent in
corrosion resistance and blackening resistance obtained by
employing a zinc-based plated steel sheet as an original sheet, and
which is capable of being produced even when an applied chemical
treatment solution is dried at a low temperature and for a short
period of time.
[0010] Another object of the present invention is to provide a
chemical treatment solution capable of forming a chemical
conversion film that enhances corrosion resistance and blackening
resistance even when being dried at a low temperature and for a
short period of time.
Solution to Problem
[0011] The present inventors have studied the chromium-free
chemical treatment for the zinc-based plated steel sheet in terms
of the relationship between treatment conditions (such as the
composition of the chemical conversion film and drying temperature)
and various quality properties. As a result, the present inventors
have found it important to form an insoluble complex film with
small residual amount of a soluble salt and a solvent, for the
enhancement of corrosion resistance. That is, it has been found
that, when excessive amounts of a fluoride, an organic acid, and an
amine with a high-boiling point remain in the chemical conversion
film, corrosion resistance is remarkably lowered. Particularly, it
has been found that, the composition of the chemical treatment
solution is quite important, because when the chemical treatment
solution is dried at a low temperature and for a short period of
time, a complex salt is less likely to be formed, and a fluoride,
an organic acid, and an amine with a high-boiling point tend to
remain.
[0012] As a result of intensive study in consideration of those
respects, the present inventors have found that the above-described
problems can be solved by forming a chemical conversion film using
a chemical treatment solution containing a water-soluble molybdate,
a vanadium salt, an amine having a low boiling point, a group 4A
metal oxoate and a phosphate, and have studied further to complete
the present invention.
[0013] That is, the present invention relates to the following
chemical treatment solution:
[1] A chemical treatment solution for coating a zinc-based plated
steel sheet having a zinc-based plating layer containing 0.1 to
22.0 mass % of aluminum, the chemical treatment solution containing
a water-soluble molybdate, a vanadium salt, an amine, a group 4A
metal oxoate and a phosphate compound, in which a molar ratio of
molybdenum to vanadium in the chemical treatment solution is 0.4 to
5.5, a molar ratio of the amine to the vanadium in the chemical
treatment solution is 0.3 or more, a content of a hydrophilic resin
in the chemical treatment solution is at most 100 mass % based on a
total amount of the vanadium and the molybdenum in the chemical
treatment solution, a total content of fluorine derived from a
fluorine ion or a fluorometal ion in the chemical treatment
solution is at most 30 mass % based on the total amount of the
vanadium and the molybdenum in the chemical treatment solution, and
a content of silicon derived from a silanol group in the chemical
treatment solution is at most 50 mass % based on the total amount
of the vanadium and the molybdenum in the chemical treatment
solution. [2] The chemical treatment solution according to [1], in
which the amine has a molecular weight of 80 or less.
[0014] Further, the present invention relates to the following
chemically treated steel sheet:
[3] A chemically treated steel sheet including a zinc-based plated
steel sheet having a zinc-based plating layer containing 0.1 to
22.0 mass % of aluminum, and a chemical conversion film disposed on
the zinc-based plating layer, in which the chemical conversion film
includes a first chemical conversion layer disposed on a surface of
the zinc-based plating layer and containing vanadium, molybdenum
and phosphorus, and a second chemical conversion layer disposed on
the first chemical conversion layer and containing a group 4A metal
oxoate, and a percentage of pentavalent vanadium based on
mixed-valent vanadium in the chemical conversion film is 0.7 or
more. [4] The chemically treated steel sheet according to [3], in
which the group 4A metal oxoate is a zirconium oxoate, and the
chemical conversion film contains 1 to 60 parts by mass of
molybdenum, 2 to 20 parts by mass of vanadium, and 10 to 50 parts
by mass of phosphorus, based on 100 parts by mass of zirconium. [5]
The chemically treated steel sheet according to [3] or [4], in
which the zinc-based plated steel sheet is a hot-dip aluminum- and
magnesium-containing zinc plated steel sheet having a hot-dip
aluminum- and magnesium-containing zinc plating layer containing
0.1 to 22.0 mass % of aluminum and 1.5 to 10.0 mass % of
magnesium.
Advantageous Effects of Invention
[0015] According to the present invention, it is possible to
produce a chemically treated steel sheet excellent in corrosion
resistance and blackening resistance even when a chemical treatment
solution applied to the surface of a zinc-based plated steel sheet
is dried at a low temperature and for a short period of time.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a TEM image of a cross-section of a test specimen
of one example of a chemically treated steel sheet according to the
present invention produced at a drying temperature of 80.degree.
C.;
[0017] FIG. 2 is a diagram showing an element distribution of the
test specimen from the surface thereof toward the depth direction;
and
[0018] FIG. 3 is a diagram showing the intensity profile of
chemical binding energy corresponding to 2p orbit of vanadium in an
interface between a chemical conversion film and plating layer
interface of a test specimen of the other example of the chemically
treated steel sheet according to the present invention.
DESCRIPTION OF EMBODIMENTS
[0019] A chemically treated steel sheet of the present invention
includes a zinc-based plated steel sheet (original sheet for
chemical treatment) and a chemical conversion film formed on a
surface of the zinc-based plated steel sheet. Hereinafter, each
constituent element will be described.
[0020] [Zinc-Based Plated Steel Sheet]
[0021] As the original sheet for chemical treatment, a zinc-based
plated steel sheet excellent in corrosion resistance and design is
used. As used herein, the term "zinc-based plated steel sheet"
means a plated steel sheet having a zinc-based plating layer
containing 0.1 to 22.0 mass % of aluminum and 50 mass % or more of
zinc. Examples of the zinc-based plated steel sheet include hot-dip
zinc plated steel sheet (GI), alloyed hot-dip zinc plated steel
sheet (GA), hot-dip zinc-aluminum plated steel sheet, and hot-dip
zinc-aluminum-magnesium plated steel sheet. The plating layers of
the hot-dip zinc plated steel sheet (GI) and alloyed hot-dip zinc
plated steel sheet (GA) also contain 0.1 mass % or more of aluminum
for preventing oxidation. The zinc-based plated steel sheet may be
produced by a hot-dip plating process, an electroplating process, a
vapor-deposition plating process, or the like.
[0022] For example, the hot-dip zinc-aluminum-magnesium plated
steel sheet can be produced by the hot-dip plating process using an
alloy plating bath containing 1.0 to 22.0 mass % of aluminum and
1.5 to 10.0 mass % of magnesium, with the residual part being
substantially zinc. In order to enhance the adherence between a
steel substrate and a plating layer, silicon which suppresses the
growth of an aluminum-iron alloy layer in the interface between the
steel substrate and the plating layer may be added to the plating
bath in a range of 0.005 to 2.0 mass %. Further, in order to
suppress the generation and the growth of Zn.sub.11Mg.sub.2 phase
which causes adverse influence on its outer appearance and
corrosion resistance, titanium, boron, a titanium-boron alloy, a
titanium-containing compound or a boron-containing compound may be
added to the plating bath. The addition amounts of these compounds
are preferably set such that titanium is within a range of 0.001 to
0.1 mass % and boron is within a range of 0.0005 to 0.045 mass
%.
[0023] The type of the steel substrate of the zinc-based plated
steel sheet is not particularly limited. Examples of the steel
substrate include common steel, low alloy steel, and stainless
steel.
[0024] [Chemical Conversion Film]
[0025] A chemical conversion film is formed on the surface of the
zinc-based plated steel sheet. The chemical conversion film
enhances the corrosion resistance and blackening resistance of the
zinc-based plated steel sheet. The chemical conversion film
includes a first chemical conversion layer (reaction layer)
positioned on the surface of the zinc-based plated steel sheet and
principally composed of vanadium, molybdenum and phosphorus, and a
second chemical conversion layer positioned on the first chemical
conversion layer and principally composed of a group 4A metal
oxoate.
[0026] As used herein, the term "corrosion resistance" includes one
or both of flat part corrosion resistance and worked part corrosion
resistance. "Worked part corrosion resistance" is corrosion
resistance of a part subjected to working (working part) such as
bending work in which a chemically treated steel sheet is deformed,
and "flat part corrosion resistance" is corrosion resistance of a
part other than the working part in the chemically treated steel
sheet.
[0027] [Chemical Treatment Solution]
[0028] The chemical conversion film is formed by applying and
drying an alkaline chemical treatment solution containing 1) a
water-soluble molybdate, 2) a vanadium salt, 3) an amine having a
low boiling point, 4) a group 4A metal oxoate, and 5) a phosphate.
By adjusting the pH of the chemical treatment solution to be
alkaline, it is possible to form the first chemical conversion
layer (reaction layer) without using fluorine or the like even on
an aluminum part of the surface of the plating layer having less
reactivity. By using the chemical treatment solution of such a
composition, it becomes possible to form a chemical conversion film
which may enhance the corrosion resistance and blackening
resistance of the zinc-based plated steel sheet, even when the
chemical treatment solution is dried at a low temperature and for a
short period of time. Note that vanadium derived from the vanadium
salt, molybdenum derived from the water-soluble molybdate and
phosphorus derived from the phosphate are localized in the first
chemical conversion layer. Further, the group 4A metal oxoate is
localized in the second chemical conversion layer. Hereinafter,
each element contained in the chemical treatment solution will be
described.
[0029] 1) Molybdate
[0030] A molybdate stabilizes the valence of vanadium in the
chemical treatment solution, and enhances the blacking resistance
and corrosion resistance of the chemically treated steel sheet. It
is deduced that a molybdenum acid ion (hereinafter, also referred
to as Mo acid ion) forms a complex with a pentavalent vanadium ion
(hereinafter, also referred to as pentavalent V ion) in the
alkaline chemical treatment solution to thereby stabilize the
valence of vanadium so as to be pentavalent.
[0031] The molar ratio of molybdenum to vanadium in the chemical
treatment solution, i.e., the molar ratio of a molybdenum element
derived from a molybdate to a vanadium element derived from a
vanadium salt (Mo/V) in the chemical treatment solution is within a
range of 0.4 to 5.5. When the molar ratio of the molybdenum element
to the vanadium element is less than 0.4, there is a concern that
the valence of vanadium cannot be kept to be pentavalent. When the
molar ratio of the molybdenum element to the vanadium element is
more than 5.5, a Mo acid ion is more likely to form a condensed
acid, and the Mo acid ion that forms a complex with the pentavalent
V ion becomes insufficient, so that there is a concern that the
valence of V may not be stable.
[0032] Further, when a chemical conversion film is formed using a
chemical treatment solution in which a molybdate and an amine
coexist, a pentavalent or hexavalent molybdenum complex oxoate is
formed in the chemical conversion film.
[0033] When a chemical conversion film is formed, in an alkaline
condition, using the chemical treatment solution in which a
vanadium salt, a molybdate and an amine coexist, molybdenum
preferentially reacts with the surface of the plating layer
together with the vanadium salt and phosphorus to form a first
chemical conversion layer (reaction layer) on the surface of the
plating layer. In this manner, the molybdate forms a uniform
reaction layer on the surface of the plating layer together with
vanadium acid and the phosphorus, and thus blackening resistance is
enhanced. Further, due to the coexistence of the molybdate and the
amine, a pentavalent or hexavalent molybdenum complex oxoate is
formed in the chemical conversion film, which pentavalent
molybdenum oxoate is oxidized to thereby form an oxidized film; the
oxidized film also contributes to the enhancement of corrosion
resistance. In addition, when the above-described lattice defect
occurs, the plating layer is considered to exhibit a gray outer
appearance with metal luster being suppressed further due to more
absorption of light of a wavelength in visible region.
[0034] The type of the molybdate is not particularly limited as
long as the molybdate can perform the above-mentioned functions.
Examples of the molybdate include molybdenum acid, ammonium
molybdate, and a molybdenum acid alkali metal salt. Among those,
molybdenum acid or ammonium molybdate is particularly preferred
from the viewpoint of corrosion resistance. The amount of
molybdenum contained in the chemical conversion film is preferably
within a range of 1 to 60 parts by mass based on 100 parts by mass
of a group 4A metal (e.g., zirconium). When the amount of
molybdenum is less than 1 part by mass, there is a concern that the
blackening resistance cannot be sufficiently enhanced. When the
amount of molybdenum is more than 60 parts by mass, the amount of a
molybdate unreacted with the surface of the plating layer becomes
excessive, so that there is a concern that working part corrosion
resistance may be lowered.
[0035] 2) Vanadium Salt
[0036] A vanadium salt contributes not only to the enhancement of
corrosion resistance but also to the enhancement of blackening
resistance. When a chemical conversion film is formed, in an
alkaline condition, using a chemical treatment solution in which a
vanadium salt, a molybdate and an amine coexist, vanadium
preferentially reacts with the surface of the plating layer
together with molybdenum acid and phosphorus to form a first
chemical conversion layer (reaction layer) on the surface of the
plating layer. In this manner, vanadium forms a uniform reaction
layer on the surface of the plating layer together with molybdenum
acid and a group 4A metal, and thus corrosion resistance and
blackening resistance are enhanced.
[0037] The type of the vanadium salt is not particularly limited as
long as the vanadium salt can perform the above-mentioned
functions. Examples of the vanadium salt include ammonium
metavanadate, sodium metavanadate, potassium metavanadate, and a
vanadate obtained by dissolving vanadium pentoxide with an amine.
In all of these vanadium salts, the valence of vanadium is
pentavalent (hereinafter, vanadium having a valence of 5 is also
referred to as "pentavalent V"). Among those, ammonium
metavanadate, or a vanadate obtained by dissolving vanadium
pentoxide with an amine is particularly preferred from the
viewpoint of corrosion resistance.
[0038] Generally, the pentavalent V ion in the chemical treatment
solution has low stability of valence. Accordingly, if the
pentavalent V ion in the chemical treatment solution is left alone,
the concentration of the pentavalent V ion fails to reach a
concentration at which the above-mentioned reaction layer is
formed. Thus, as described above, the coexistence with the
molybdate in an alkaline condition increases the concentration of
the pentavalent V ion in the chemical treatment solution. Further,
it is considered that the pentavalent V ion does not have higher
solubility in the chemical treatment solution than a divalent to
tetravalent vanadium ion chelated through reduction by an organic
acid or the like, and thus is more likely to preferentially
precipitate on the surface of the plating layer to generate a
reaction.
[0039] The content of the vanadium salt in the chemically treatment
solution is preferably 8 g/L or less in terms of vanadium atom.
When this content is more than 8 g/L, the stability of the chemical
treatment solution is lowered, so that there is a possibility of
the formation of a precipitate when the chemical treatment solution
is stored at room temperature for about a month. In this
connection, in a case where the chemical treatment solution is used
immediately after the production thereof, the above-mentioned
problem of stability does not occur even when the above-mentioned
content is more than 8 g/L.
[0040] The amount of vanadium contained in the chemical treatment
solution is preferably within a range of 2 to 20 parts by mass
based on 100 parts by mass of a group 4A metal (e.g., zirconium).
When the amount of vanadium is less than 2 parts by mass, there is
a concern that the corrosion resistance and blackening resistance
cannot be enhanced sufficiently. When the amount of vanadium is
more than 20 parts by mass, there is a concern that the amount of
pentavalent vanadium unreacted with the surface of the plating
layer may become excessive, causing the corrosion resistance to be
lowered.
[0041] The percentage of pentavalent vanadium based on mixed-valent
vanadium in the chemical conversion film is 0.7 or more. When the
percentage of pentavalent vanadium based on mixed-valent vanadium
is less than 0.7, there is a concern that the blackening resistance
cannot be enhanced sufficiently.
[0042] 3) Amine
[0043] An amine dissolves a salt containing pentavalent vanadium
(hereafter, also referred to as "pentavalent vanadium salt") in the
chemical treatment solution while keeping the valence of vanadium
to be pentavalent (tetravalent when an organic acid is used), and
also forms a pentavalent or hexavalent molybdenum complex oxoate
from a molybdate. The amine is preferably an amine having a low
boiling point. The amine having a low boiling point is an amine
having a molecular weight of 80 or less. The amine having a
molecular weight of 80 or less generally has a low boiling point,
and hardly remains in a chemical conversion film even when the
chemical treatment solution is dried at a low temperature and for a
short period of time, so that the amine can contribute to the
enhancement of the corrosion resistance. Examples of the amine
having a low boiling point include ammonia (used as aqueous
ammonia), ethanolamine, 1-amino-2-propanol, and ethylenediamine.
When an excessive amount of amine remains in the chemical
conversion film after being dried, the corrosion resistance of a
chemically treated steel sheet is undesirably lowered due to
elution of an amine. Therefore, the amount of the amine remaining
in the chemical conversion film is preferably 10 mass % or less in
terms of nitrogen from the viewpoint of preventing the lowering of
the corrosion resistance of the chemically treated steel sheet. By
using an amine having a molecular weight of 80 or less, the amount
of the remaining amine can be 10 mass % or less in terms of
nitrogen.
[0044] By dissolving a pentavalent vanadium salt in a liquid amine
or an aqueous amine solution, the pentavalent vanadium salt having
low water-solubility can be blended into a chemical treatment
solution while keeping the valence of vanadium to be pentavalent.
When dissolving the pentavalent vanadium salt in a liquid amine,
the addition of the resultant solution to the aqueous solution
containing a molybdate enables a chemical treatment solution to be
prepared. In addition, when dissolving the pentavalent vanadium
salt in an aqueous amine solution, a pentavalent vanadium salt may
be added after the molybdate and the amine to thereby directly
prepare a chemical treatment solution, or a pentavalent vanadium
salt may be dissolved in the aqueous amine solution, and then the
resultant solution may be added to the aqueous solution containing
a molybdate to prepared a chemical treatment solution. Typically,
an aqueous solution containing tetravalent vanadium (V.sup.4+) is
blue, whereas an aqueous solution containing pentavalent vanadium
(V.sup.5+) is yellow, and thus it is possible to presume the
valence of vanadium from the color of the chemical treatment
solution.
[0045] As described above, when using a vanadate as a vanadium
salt, vanadium pentoxide is dissolved in an amine to prepare a
vanadate. At that time, heat is generated in dissolving pentavalent
vanadium in an amine. There is a concern that the pentavalent
vanadium may be reduced to tetravalent vanadium in a high
temperature environment of 40.degree. C. or higher. Thus, in order
to dissolve the pentavalent vanadium salt in an amine while keeping
the valence of vanadium to be pentavalent, it is necessary to
maintain an environmental temperature of the pentavalent vanadium
less than 40.degree. C. The method in which the environmental
temperature is maintained less than 40.degree. C. is not
particularly limited. For example, the addition of vanadium
pentoxide to the amine solution (dilution of amine and vanadium
pentoxide) can maintain the environmental temperature less than
40.degree. C.
[0046] The molar ratio of the amine to vanadium in the chemical
treatment solution is 0.3 or more. When this molar ratio is less
than 0.3, there is a concern that the valence of vanadium cannot be
kept to be pentavalent. The molar ratio of the amine to vanadium is
preferably 10 or less from the viewpoints of not allowing the
effect of maintaining the valence of vanadium to reach a plateau,
and of suppressing the cost of amine.
[0047] 4) Group 4A Metal Oxoate
[0048] A group 4A metal oxoate forms a dense chemical conversion
film to enhance corrosion resistance. That is, while it is
difficult to form a dense chemical conversion film with a chemical
treatment solution containing only a molybdate and a vanadium salt,
it is possible to form a chemical conversion film having a high
barrier property by cross-linking molybdenum and vanadium with the
further addition of the group 4A metal oxoate.
[0049] The type of the group 4A metal oxoate is not particularly
limited. Examples of the group 4A metal oxoate include titanium,
zirconium, and hafnium. Examples of the type of oxoate include
hydracid salt, ammonium salt, alkaline metal salt, and alkaline
earth metal salt. Among those, a group 4A metal oxoate ammonium
salt is preferred, and ammonium zirconium carbonate is particularly
preferred, from the viewpoint of corrosion resistance.
[0050] 5) Phosphate
[0051] The chemical treatment solution further contains a
phosphate. The phosphate functions with the group 4A metal oxoate
to thereby form a dense chemical conversion film, thus enhancing
corrosion resistance. The type of the phosphate is not particularly
limited as long as the phosphate can perform the above-mentioned
functions. Examples of the phosphate include an alkali metal
phosphate, and an ammonium phosphate. In particular, diammonium
hydrogen phosphate or ammonium dihydrogen phosphate, which can
sufficiently enhance corrosion resistance, is preferred, even when
being dried at a low temperature and for a short period of time.
The amount of phosphorus in the chemical conversion film is
preferably in a range of 10 to 50 parts by mass based on 100 parts
by mass of the group 4A metal (e.g., zirconium). When the amount of
phosphorus is less than 10 parts by mass, a crack which constitutes
a defect is more likely to occur in the chemical conversion film,
so that there is a concern that the corrosion resistance may be
lowered. When the amount of phosphorus is more than 50 parts by
mass, an unreacted phosphate remains in the chemical conversion
film, so that there is a concern that the corrosion resistance may
be lowered.
[0052] Noted that, when specific component used in the conventional
chromium-free chemical treatment is added to the above-mentioned
chemical treatment solution, the expected characteristics of the
chemically treated steel sheet may be insufficient. For example, a
certain type of organic resin, silane coupling agent, or organic
acid is added, a pentavalent V ion is more likely to be reduced to
a tetravalent vanadium ion, so that blackening resistance may be
lowered. Further, a functional group having a polarity is adsorbed
to the plating surface, and thus the formation of a reaction layer
at that portion is inhibited, so that there is a concern that
corrosion resistance may be lowered. This phenomenon may be also
observed when a film-forming aid (solvent such as butyl cellosolve)
for forming a film from an aqueous organic resin at a low
temperature is added. Thus, it is preferable for the chemical
treatment solution of the present invention not to contain the
organic acid, organic resin, silane coupling agent, and
film-forming aid.
[0053] The above-mentioned specific component is not substantially
contained in the chemical treatment solution. That is, the chemical
treatment solution may be substantially composed of the
above-mentioned component. As used herein, the term "not
substantially contained" means that "may be contained in such a
range that the above-described effects of the present invention are
achieved," and also means that "preferably not contained at all
from the viewpoint of remarkably achieving the above-described
effects of the present invention." Examples of the specific
component include a hydrophilic resin, fluorine derived from a
fluorine ion or a fluorometal ion, and silicon derived from a
silanol group.
[0054] The hydrophilic resin is a resin dissolved or dispersed
evenly in an aqueous medium, and contains a hydrophilic functional
group in an amount enough to allow the resin to be dissolved or
dispersed evenly in the aqueous medium. The hydrophilic resin may
also be referred to as an aqueous resin. Either one type of the
hydrophilic resin or two or more types thereof may be employed.
Examples of the hydrophilic resin include a resin which is
dissolved or evenly dispersed in an aqueous medium to increase the
viscosity of the aqueous medium; more specific examples thereof
include acrylic resin, a polyolefin, epoxy resin, and polyurethane,
which have the hydrophilic functional group as necessary due to
modification. Examples of the hydrophilic functional group include
a hydroxyl group, a carboxyl group, and an amino group. Either one
type of the hydrophilic functional group or two or more types
thereof may be employed, as well.
[0055] Incidentally, on the surface of the zinc-based plated steel
sheet, there exists a polar group which typically exists on the
surface of a metal, such as a hydroxyl group. The above-mentioned
reaction layer is considered to be formed through a specific
interaction of the polar group with component which constitutes the
reaction layer, such as molybdenum and vanadium in the chemical
treatment solution.
[0056] Accordingly, it is considered that, when there exists a
large amount of the hydrophilic resin in the chemical treatment
solution, the hydrophilic functional group undergoes an interaction
such as hydrogen bonding or dehydration condensation with the polar
group on the surface of the zinc-based plated steel sheet, so that
the polar group to interact with a component in the reaction layer
becomes insufficient relative to the component in the reaction
layer, and as a result the formation of the reaction layer is
inhibited, causing the expected characteristics of the chemically
treated steel sheet to be insufficient.
[0057] For the above-mentioned reasons, the acceptable content of
the hydrophilic resin in the chemical treatment solution is at most
100 mass % (i.e., 100 mass % or less) based on the total amount of
vanadium and molybdenum in the chemical treatment solution. When
the content of the hydrophilic resin is more than 100 mass %, the
formation of the reaction layer is inhibited, so that the expected
functions such as corrosion resistance and blackening resistance in
the chemically treated steel sheet may be insufficient. From the
viewpoint of sufficiently exhibiting expected functions in the
chemically treated steel sheet, the content of the hydrophilic
resin is preferably as small as possible; for example, the content
thereof is preferably 50 mass % or less, more preferably 20 mass %
or less, and most preferably 0 mass %.
[0058] The fluorine derived from a fluorine ion or a fluorometal
ion may exhibit etching actions on the surface of the zinc-based
plated steel sheet to form a layer of a fluoride. Examples of the
fluorine include F.sup.- and MF.sub.6.sup.2-. As used herein, "M"
denotes a tetravalent metal element, for example, zirconium,
titanium, or silicon. Examples of the above-mentioned component
which serves as an origin of the fluorine include potassium
fluoride (KF), ammonium titanium fluoride
((NH.sub.4).sub.2TiF.sub.6), and hydrofluosilicic acid
(H.sub.2SiF.sub.6). Either one type of the fluorine or two or more
types thereof may be employed.
[0059] It is considered that, when there exists a large amount of
the fluorine in the chemical treatment solution, the surface of the
zinc-based plated steel sheet is dissolved by the etching action of
the fluorine, and the fluorine in the chemical treatment solution
is concentrated on the dissolved portion, with a fluoride thin
layer being formed on the surface of the zinc-based plated steel
sheet, so that the polar group, which is exposed to the surface of
the zinc-based plated steel sheet, to interact with the component
in the reaction layer becomes insufficient relative to the
component in the reaction layer, resulting in the inhibition of the
formation of the reaction layer, causing the expected
characteristics of the chemically treated steel sheet to be
insufficient. Examples of the component that occurs due to the
dissolution of the surface of the zinc-based plated steel sheet
include Zn.sup.2+, Al.sup.3+, and Mg.sup.2+, and examples of the
fluoride include ZnF.sub.2, AlF.sub.3, and MgF.sub.2. It is noted
that the fluoride can be confirmed on the chemically treated steel
sheet by X-ray photoelectron spectroscopy (XPS).
[0060] For the above-mentioned reasons, the total content of the
fluorine derived from a fluorine ion or a fluorometal ion in the
chemical treatment solution is at most 30 mass % (i.e., 30 mass %
or less) based on the total amount of vanadium and molybdenum in
the chemical treatment solution. When the content of the fluorine
is more than 30 mass %, the formation of the reaction layer may be
inhibited, so that the expected functions such as corrosion
resistance and blackening resistance in the chemically treated
steel sheet may be insufficient. From the viewpoint of sufficiently
exhibiting expected functions in the chemically treated steel
sheet, the content of the fluorine is preferably as small as
possible; for example, the content thereof is preferably 10 mass %
or less, more preferably 5 mass % or less, and most preferably 0
mass %.
[0061] The silicon derived from a silanol group has a hydroxyl
group. Accordingly, it is considered that, when the chemical
treatment solution contains the silicon, the existence of the
silicon derived from a silanol group inhibits the formation of the
reaction layer, for the similar reason to those for the hydrophilic
resin. That is, it is considered that, when there exists a large
amount of the silicon in the chemical treatment solution, the
hydrophilic group in the silanol group undergoes an interaction
such as hydrogen bonding or dehydration condensation with the polar
group on the surface of the zinc-based plated steel sheet, so that
the polar group to interact with a component in the reaction layer
becomes insufficient relative to the component in the reaction
layer, and as a result the formation of the reaction layer is
inhibited, causing the expected characteristics of the chemically
treated steel sheet to be insufficient. Examples of the component
which serves as an origin of the silicon include a silane coupling
agent; more specific examples thereof include
3-aminopropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane,
and vinylethoxysilane.
[0062] For the above-mentioned reasons, the content of the silicon
derived from a silanol group in the chemical treatment solution is
at most 50 mass % (i.e., 50 mass % or less) based on the total
amount of vanadium and molybdenum in the chemical treatment
solution. When the content of the silicon is more than 50 mass %,
the formation of the reaction layer may be inhibited, so that the
expected functions such as corrosion resistance and blackening
resistance in the chemically treated steel sheet may be
insufficient. From the viewpoint of sufficiently exhibiting
expected functions in the chemically treated steel sheet, the
content of the silicon is preferably as small as possible; for
example, the content thereof is preferably 20 mass % or less, more
preferably 10 mass % or less, and most preferably 0 mass %.
[0063] The existence and the content of the hydrophilic resin,
fluorine, or silicon in the chemical treatment solution can be
determined using known analyzers such as infrared spectroscopy (IR)
spectrometer, nuclear magnetic resonance (NMR) spectrometer,
inductively coupled plasma (ICP) emission analyzer, and fluorescent
X-ray analyzer.
[0064] The method of identifying the structure of a chemical
conversion film is not particularly limited. For example, it is
possible to confirm that a chemical conversion film includes the
first chemical conversion layer and the second chemical conversion
layer, by observing the cross-section of a chemically treated steel
sheet using a transmission electron microscope (TEM). Further,
energy dispersive X-ray measurement (EDS) can be used to identify a
component contained in each chemical conversion layer. Furthermore,
glow discharge optical emission spectrometry (GDS) can be used to
identify the distribution of each component. Moreover, X-ray
photoelectron spectroscopy (XPS) can be used to identify the
percentage of pentavalent vanadium based on the mixed-valent
vanadium in the chemical conversion film.
[0065] [Method of Formation of Chemical Conversion Film]
[0066] As described above, a chemical conversion film is formed by
applying a chemical treatment solution containing the
above-mentioned each component to the surface of a zinc-based
plated steel sheet, and drying the same.
[0067] The application method of the chemical treatment solution is
not particularly limited. Examples of the application method of the
chemical treatment solution include roll coating method, spin
coating method, and spray coating method. The deposition amount of
the chemical treatment solution is preferably within a range of 50
to 1,000 mg/m.sup.2. When the deposition amount is less than 50
mg/m.sup.2, corrosion resistance cannot be sufficiently enhanced.
When the deposition amount is more than 1,000 mg/m.sup.2, corrosion
resistance undesirably becomes excessive. Furthermore, taking
account of spot weldability, the deposition amount of the chemical
conversion film is more preferably within a range of 50 to 500
mg/m.sup.2.
[0068] The drying temperature of the chemical treatment solution (a
temperature of the sheet) may be an ordinary temperature, but is
preferably 30.degree. C. or higher. The chemical treatment solution
of the present invention can enhance corrosion resistance and
blackening resistance even when being dried at a low temperature
and for a long period of time. When the drying temperature exceeds
120.degree. C., a crack undesirably occurs due to the volume
shrinkage of the chemical conversion film as a result of, for
example, rapid decomposition of ammonia components, so that there
is a concern that the corrosion resistance of the chemically
treated steel sheet may be lowered. Therefore, the drying
temperature of the chemical treatment solution is within a range of
preferably 30 to 120.degree. C., and more preferably 35 to
85.degree. C.
[0069] As described above, the chemical treatment solution
according to the present invention contains the above-mentioned
water-soluble molybdate, vanadium salt, amine, group 4A metal
oxoate, and phosphate compound, and the molybdate and amine are
contained at the above-mentioned specific ratio to the vanadium
salt. In addition, the chemical treatment solution of the present
invention neither contains the above-mentioned hydrophilic resin,
nor fluorine derived from a fluorine ion or a fluorometal ion, nor
silicon derived from a silanol group, or alternatively only
contains these elements up to the above-mentioned specific
acceptable amount. Since such a chemical treatment solution is used
for production, the chemically treated steel sheet of the present
invention includes a zinc-based plated steel sheet, vanadium,
molybdenum, phosphorus, and a group 4A metal oxoate, and including
a two-layer structure of the first chemical conversion layer and
the second chemical conversion layer. Therefore, the chemically
treated steel sheet of the present invention is excellent in
corrosion resistance and blackening resistance even when the
chemical treatment solution is dried at a low temperature and for a
short period of time.
[0070] Hereinafter, the present invention will be explained in
detail with reference to Examples, which however shall not be
construed as limiting the scope of the invention thereto.
EXAMPLES
Production of Zinc-Based Plated Steel Sheet
[0071] A steel strip of ultra-low carbon titanium-added steel
having a sheet thickness of 0.5 mm was used as the substrate steel
to produce a hot-dip zinc alloy plated steel sheet having a
zinc-based layer containing 6 mass % of aluminum, 3 mass % of
magnesium, 0.020 mass % of silicon, 0.020 mass % of titanium, and
0.0005 mass % of boron (plating deposition amount of 90 g/m.sup.2
per side), in a continuous hot-dip zinc plating production line,
and the produced zinc alloy plated steel sheet was used as the
original sheet for chemical treatment.
Example 1
[0072] A water-soluble molybdenum salt, a vanadium salt, an amine,
a group 4A metal oxoate, and a phosphate, which are shown in Table
1, were dissolved in water to prepare chemical treatment solutions
1 to 50. The name and symbol of each compound added to the chemical
treatment solution are shown in Table 1. The composition and color
of each chemical treatment solution are shown in Tables 2-1, 2-2,
3-1, 3-2, 4-1 and 4-2. Note that the dissolution of the vanadium
salt was performed in an aqueous solution having a liquid
temperature of 40.degree. C. or lower containing an amine for
preventing vanadium from being reduced.
TABLE-US-00001 TABLE 1 Type Symbol Compound Name Chemical Formula
Molecular Weight Molybdate M1 Ammonium Molybdate
(NH.sub.4).sub.6Mo.sub.7O.sub.24.cndot.4H.sub.2O -- Vanadium Salt
V1 Vanadium Pentoxide V.sub.2O.sub.5 -- V2 Ammonium Metavanadate
NH.sub.4VO.sub.3 -- V3 Sodium Metavanadate NaVO.sub.3 -- Amine EA
Ethanolamine C.sub.2H.sub.7NO 61 DEA Diethanolamine
C.sub.4H.sub.11NO.sub.2 105 IPA 1-Amino-2-Propanol C.sub.3H.sub.9NO
75 TMAH Tetramethylammonium hydroxide
(CH.sub.3).sub.4N.sup.+OH.sup.- 91 EDTA Ethylenediaminetetraacetic
Acid (HOOCCH.sub.2).sub.2NCH.sub.2CH.sub.2N(CH.sub.2COOH).sub.2 292
EN Ethylenediamine NH.sub.2CH.sub.2CH.sub.2NH.sub.2 60 NH Aqueous
Ammonia NH.sub.4OH 35 Group 4A Oxoate A1 Ammonium Zirconium
Carbonate (NH.sub.4).sub.2Zr(OH).sub.2(CO.sub.3).sub.2 -- Phosphate
P1 Diammonium Hydrogen Phosphate (NH.sub.4).sub.2HPO.sub.4 -- P2
Ammonium Dihydrogen Phosphate NH.sub.4H.sub.2PO.sub.4 -- P3
Triammonium Phosphate (NH.sub.4).sub.3PO.sub.4 -- P4 Phosphorous
Acid H.sub.3PO.sub.3 -- P5 1-Hydroxyethane-1,1-Diphosphonic Acid
C.sub.2H.sub.8O.sub.7P.sub.2 -- Fluorine Compound F1 Potassium
Fluoride KF -- F2 Ammonium Titanium Fluoride
(NH.sub.4).sub.2TiF.sub.6 -- F3 Hydrofluosilicic Acid
H.sub.2SiF.sub.6 -- Silicon Compound S1
3-Aminopropyltrimethoxysilane
H.sub.2NC.sub.3H.sub.6Si(OCH.sub.3).sub.3 -- S2
3-Glycidoxypropyltriethoxysilane
(H.sub.2CCHO)CH.sub.2OC.sub.3H.sub.6Si(OC.sub.2H.sub.5).sub.3 -- S3
Vinylethoxysilane H.sub.2C.dbd.CHSi(OC.sub.2H.sub.5).sub.3 --
TABLE-US-00002 TABLE 2-1 Chemical Molybdate Vanadium Salt Treatment
Mo V Amine Solution Conc. Conc. Conc. Category No. Compound (g/L)
Compound (g/L) Compound (g/L) Ex. 1 M1 0.075 V1 0.10 EA 0.036 Comp.
Ex. 2 M1 0.019 V1 0.10 IPA 0.044 Ex. 3 M1 0.075 V2 0.01 EN 0.035
Ex. 4 M1 0.075 V2 0.10 NH 0.021 Comp. Ex. 5 M1 5.00 V3 0.10 EA
0.036 Ex. 6 M1 1.51 V3 2.00 IPA 0.883 Ex. 7 M1 0.075 V1 0.10 EN
0.036 Comp. Ex. 8 M1 0.075 V2 0.10 NH 0.007 Ex. 9 M1 24.0 V3 8.00
EN 15.1 Comp. Ex. 10 M1 1.51 V1 8.00 NH 8.79 Comp. Ex. 11 M1 0.015
V3 8.00 EA 15.3 Ex. 12 M1 0.075 V3 0.02 NH 0.027 Ex. 13 M1 24.0 V2
8.00 EA 15.3 Ex. 14 M1 45.2 V3 8.00 IPA 18.8 Comp. Ex. 15 M1 90.4
V1 8.00 EN 15.1 Ex. 16 M1 24.0 V2 10.00 EA 19.2 Ex. 17 M1 24.0 V2
8.00 IPA 18.8 Comp. Ex. 18 M1 24.0 V3 8.00 EN 1.89 Ex. 19 M1 22.6
V3 8.00 DEA 39.6 Ex. 20 M1 0.753 V3 0.80 EA 3.07
TABLE-US-00003 TABLE 2-2 Group 4A Chemical Metal Oxoate Phosphate
Treatment Zr P Color of Solution Conc. Conc. Mo/V Amine/V Treatment
Category No. Compound (g/L) Compound (g/L) (Molar Ratio) (Molar
Ratio) Solution Ex. 1 A1 5.0 P1 0.25 0.40 0.30 Yellow Comp. Ex. 2
A1 5.0 P2 0.25 0.10 0.30 Yellowish Green Ex. 3 A1 5.0 P4 0.25 4.00
3.00 Yellow Ex. 4 A1 5.0 P5 0.05 0.40 0.30 Yellow Comp. Ex. 5 A1
5.0 P3 0.25 26.55 0.30 Yellowish Green Ex. 6 A1 5.0 P3 0.25 0.40
0.30 Yellow Ex. 7 A1 5.0 P4 6.00 0.40 0.30 Yellow Comp. Ex. 8 A1
5.0 P2 0.25 0.40 0.10 Yellowish Green Ex. 9 A1 40.0 P1 20.0 1.59
1.60 Yellow Comp. Ex. 10 A1 40.0 P3 20.0 0.10 1.60 Yellowish Green
Comp. Ex. 11 A1 40.0 P2 20.0 0.00 1.60 Yellowish Green Ex. 12 A1
40.0 P5 20.0 1.59 1.60 Yellow Ex. 13 A1 40.0 P4 2.00 1.59 1.60
Yellow Ex. 14 A1 40.0 P3 20.0 3.00 1.60 Yellow Comp. Ex. 15 A1 40.0
P2 20.0 6.00 1.60 Yellowish Green Ex. 16 A1 40.0 P1 20.0 1.27 1.60
Yellow Ex. 17 A1 40.0 P5 60.0 1.59 1.60 Yellow Comp. Ex. 18 A1 40.0
P3 20.0 1.59 0.20 Yellowish Green Ex. 19 A1 40.0 P1 20.0 1.50 2.40
Yellow Ex. 20 A1 40.0 P4 20.0 0.50 3.20 Yellow
TABLE-US-00004 TABLE 3-1 Vanadium Chemical Molybdate Salt Treatment
Mo V Amine Cate- Solution Com- Conc. Com- Conc. Com- Conc. gory No.
pound (g/L) pound (g/L) pound (g/L) Ex. 21 M1 24.0 V2 8.00 NH 8.79
Ex. 22 M1 24.0 V2 8.00 EN 15.1 Ex. 23 M1 24.0 V3 8.00 TMAH 22.9 Ex.
24 M1 14.1 V2 5.00 NH 11.0 Ex. 25 M1 1.98 V3 0.30 EA 1.15 Ex. 26 M1
0.075 V1 0.10 EN 0.036 Ex. 27 M1 24.0 V3 8.00 EDTA 73.4 Ex. 28 M1
25.4 V2 3.00 NH 1.65 Ex. 29 M1 0.942 V2 1.00 NH 1.10 Ex. 30 M1 6.59
V1 1.00 IPA 5.89 Ex. 31 M1 3.50 V2 2.00 NH 2.20 Ex. 32 M1 0.075 V1
0.10 EDTA 0.172 Ex. 33 M1 1.41 V3 0.50 IPA 1.77 Ex. 34 M1 0.075 V2
0.10 NH 0.021 Ex. 35 M1 3.77 V3 0.80 IPA 3.77 Ex. 36 M1 24.0 V2
8.00 NH 8.79 Ex. 37 M1 3.50 V1 2.00 IPA 4.71 Ex. 38 M1 0.075 V3
0.10 EA 0.036 Ex. 39 M1 3.11 V3 0.30 IPA 1.06 Ex. 40 M1 7.53 V2
8.00 EN 22.6
TABLE-US-00005 TABLE 3-2 Group 4A Chemical Metal Oxoate Phosphate
Treatment Zr P Color of Solution Conc. Conc. Mo/V Amine/V Treatment
Category No. Compound (g/L) Compound (g/L) (Molar Ratio) (Molar
Ratio) Solution Ex. 21 A1 40.0 P2 0.50 1.59 1.60 Yellow Ex. 22 A1
5.0 P4 0.25 1.59 1.60 Yellow Ex. 23 A1 40.0 P1 20.0 1.59 1.60
Yellow Ex. 24 A1 33.5 P5 0.60 1.50 3.20 Yellow Ex. 25 A1 5.0 P3
0.25 3.50 3.20 Yellow Ex. 26 A1 14.0 P4 6.00 0.40 0.30 Yellow Ex.
27 A1 40.0 P1 20.0 1.59 1.60 Yellow Ex. 28 A1 27.0 P2 0.50 4.50
0.80 Yellow Ex. 29 A1 46.5 P2 0.50 0.50 1.60 Yellow Ex. 30 A1 5.0
P2 0.25 3.50 4.00 Yellow Ex. 31 A1 7.5 P2 0.50 0.93 1.60 Yellow Ex.
32 A1 5.0 P1 0.25 0.40 0.30 Yellow Ex. 33 A1 40.0 P3 0.50 1.50 2.40
Yellow Ex. 34 A1 40.0 P2 0.50 0.40 0.30 Yellow Ex. 35 A1 5.0 P3
0.25 2.50 3.20 Yellow Ex. 36 A1 33.5 P2 0.50 1.59 16.0 Yellow Ex.
37 A1 14.0 P2 0.50 0.93 1.60 Yellow Ex. 38 A1 33.5 P3 0.50 0.40
0.30 Yellow Ex. 39 A1 40.0 P4 20.0 5.50 2.40 Yellow Ex. 40 A1 20.5
P4 0.50 0.50 2.40 Yellow
TABLE-US-00006 TABLE 4-1 Vanadium Chemical Molybdate Salt Treatment
Mo V Amine Cate- Solution Com- Conc. Com- Conc. Com- Conc. gory No.
pound (g/L) pound (g/L) pound (g/L) Ex. 41 M1 24.0 V3 8.00 EN 15.1
Ex. 42 M1 0.075 V3 0.10 NH 0.021 Ex. 43 M1 0.471 V1 0.50 DEA 4.12
Ex. 44 M1 24.0 V2 8.00 NH 8.79 Ex. 45 M1 23.5 V2 5.00 IPA 29.4 Ex.
46 M1 24.0 V2 8.00 NH 8.79 Ex. 47 M1 0.075 V3 0.10 IPA 0.044 Ex. 48
M1 0.075 V2 0.10 IPA 0.044 Ex. 49 M1 0.075 V1 0.10 TMAH 0.054 Ex.
50 M1 14.1 V1 3.00 EN 5.75
TABLE-US-00007 TABLE 4-2 Group 4A Chemical Metal Oxoate Phosphate
Treatment Zr P Color of Solution Conc. Conc. Mo/V Amine/V Treatment
Category No. Compound (g/L) Compound (g/L) (Molar Ratio) (Molar
Ratio) Solution Ex. 41 A1 40.0 P5 20.0 1.59 1.60 Yellow Ex. 42 A1
40.0 P2 20.0 0.40 0.30 Yellow Ex. 43 A1 5.0 P1 0.25 0.50 4.00
Yellow Ex. 44 A1 46.5 P2 0.50 1.59 1.60 Yellow Ex. 45 A1 27.0 P1
7.50 2.50 4.00 Yellow Ex. 46 A1 5.0 P5 0.25 1.59 1.60 Yellow Ex. 47
A1 40.0 P3 20.0 0.40 0.30 Yellow Ex. 48 A1 27.0 P5 7.50 0.40 0.30
Yellow Ex. 49 A1 5.0 P1 0.25 0.40 0.30 Yellow Ex. 50 A1 7.5 P4 6.00
2.50 1.60 Yellow
[0073] The surface of the original sheet for chemical treatment was
degreased, and dried. Then, each of chemical treatment solutions
Nos. 1 to 18 shown in Table 2-1 was applied to the surface of the
original sheet for chemical treatment, and immediately thereafter
heated and dried at a low temperature (a temperature of the steel
strip of 40 or 80.degree. C.) using an automatic discharge type
electric hot air oven to form a chemical conversion film. Thus,
chemically treated steel sheets Nos. 1 to 36 having the chemical
conversion film were produced. Note that the deposition amount of
the chemical conversion film in all the chemically treated steel
sheets was set at 200 mg/m.sup.2.
[0074] [Evaluation of Chemically Treated Steel Sheet]
[0075] For a test specimen cut out from each chemically treated
steel sheet, the structure of the chemical conversion film was
identified; the percentage of pentavalent vanadium based on
mixed-valent vanadium in the film was determined; the film
deposition amount was measured; and the test specimen was subjected
to corrosion resistance test and blackening resistance test.
[0076] (1) Identification of Structure of Chemical Conversion
Film
[0077] The structure of the chemical conversion film was identified
using the above-mentioned TEM, EDS, and XPS.
[0078] For example, FIG. 1 is a TEM image of the cross-section of a
test specimen of chemically treated steel sheet No. 17. As
illustrated in FIG. 1, the chemical conversion film of chemically
treated steel sheet has a two-layer structure including the first
chemical conversion layer and the second chemical conversion
layer.
[0079] FIG. 2 shows an element distribution of the test specimen of
chemically treated steel sheet No. 17, from the surface thereof
toward the depth direction, measured using GDS. The abscissa in
FIG. 2 indicates a measuring time (corresponding to the depth from
the surface), and the ordinate indicates the relative intensity. As
shown in FIG. 2, in the chemical conversion film of chemically
treated steel sheet No. 17, the first chemical conversion layer
contains large amounts of molybdenum, vanadium, and phosphorus, and
the second conversion layer contains zirconium.
[0080] Although not specifically illustrated, it was also
confirmed, in other chemically treated steel sheet categorized in
Examples, that the chemical conversion film has the two-layer
structure in the same manner as chemically treated steel sheet No.
17, and contains vanadium, molybdenum, and phosphorus in the first
chemical conversion layer and a group 4A metal oxoate in the second
chemical conversion layer. The two-layer structure in the chemical
conversion film was not confirmed in chemically treated steel
sheets categorized in Comparative Examples.
[0081] (2) Measurement of Deposition Amount of Chemical Conversion
Film
[0082] For the confirmation of the deposition amount, zirconium in
the film was measured using a fluorescent X-ray apparatus, and the
measurement was used as an index the deposition amount.
[0083] (3) Measurement of Percentage of Pentavalent Vanadium Based
on Mixed-Valent Vanadium in Chemical Conversion Film
[0084] The percentage of pentavalent vanadium based on mixed-valent
vanadium (V.sup.5+/V) in the chemical conversion film was
determined by analyzing the chemical binding state of vanadium in
the chemical conversion film using X-ray Photoelectron Spectroscopy
(XPS). Two points of the surface layer of the chemical conversion
film and the interface between the chemical conversion film and the
plating layer were taken as points for analysis for each site of 10
locations randomly selected from the above-mentioned test specimen.
The analysis of the interface between the chemical conversion film
and the plating layer was performed after the chemical conversion
film was sputtered using an argon beam from the surface layer. The
depth at which the chemical conversion film was sputtered was
determined by measuring the thickness of the chemical conversion
film from the results of observation of the film cross-section
using TEM. The percentage of pentavalent vanadium based on
mixed-valent vanadium was determined from the percentage of a peak
area of about 516.5 eV derived from V.sup.5+ (S.sub.V5) based on
the total sum of the peak area derived from V.sup.5+ and a peak
area of 514 eV derived from V.sup.4+
(S.sub.V4)(S.sub.V5/(S.sub.V4+S.sub.V5). The average value of the
percentages at 10 measuring locations in each test specimen was
employed as the percentage of pentavalent vanadium based on
mixed-valent vanadium (V.sup.5+/V) in the chemically treated steel
sheet.
[0085] For example, FIG. 3 is an intensity profile of chemical
binding energy corresponding to 2p orbit of vanadium in a
film/plating layer interface in one location of 10 measuring
locations at which a test specimen of chemically treated steel
sheet No. 12 produced by drying chemical treatment solution No. 4
at a drying temperature of 80.degree. C. was measured. The abscissa
in FIG. 3 indicates binding energy, and the ordinate indicates
relative intensity for a short period of time (per second).
Further, solid line Mv in FIG. 3 is an intensity profile of
chemical binding energy actually measured in the measuring point.
Dotted line P.sub.V5 indicates a peak derived from pentavalent
vanadium, dotted line P.sub.V4 indicates a peak derived from
tetravalent vanadium, and solid line B indicates a baseline.
[0086] It could be confirmed, from FIG. 3, that the percentage of
V.sup.5+ in the chemical conversion film was 0.7 or more in the
above-mentioned test specimen. It was confirmed that the percentage
of V.sup.5+ in the chemical conversion film was 0.7 or more also in
other chemically treated steel sheets, although not particularly
illustrated.
[0087] (4) Flat Part Corrosion Resistance Test
[0088] The edge surface of the test specimen of each chemically
treated steel sheet was sealed and subjected to a salt spray test
for 120 hours in accordance with JIS Z2371, and thereafter white
rust generated on a surface of the test specimen was observed. Each
chemically treated steel sheet was evaluated as follows: when the
percentage of an area where white rust was generated was 5% or
less, the evaluation was "A"; when the percentage was more than 5%
to 10% or less, the evaluation was "B"; when the percentage was
more than 10% to less than 30%, the evaluation was "C"; and when
the percentage was 30% or more, the evaluation was "D."
[0089] (5) Worked Part Corrosion Resistance Test
[0090] A bead drawing test (bead height: 4 mm, pressure: 1.0 kN)
was performed for a test specimen of 30 mm.times.250 mm of each
chemically treated steel sheet, and the edge surface of the test
specimen was sealed and subjected to a salt spray test for 24 hours
in accordance with JIS Z2371; thereafter white rust generated on a
sliding surface was observed. Each chemically treated steel sheet
was evaluated as follows: when the percentage of an area where
white rust was generated was 5% or less, the evaluation was "A";
when the percentage was more than 5% to 10% or less, the evaluation
was "B"; when the percentage was more than 10% to less than 30%,
the evaluation was "C"; and when the percentage was 30% or more,
the evaluation was "D."
[0091] (6) Blackening Resistance Test
[0092] A test specimen of each chemically treated steel sheet was
left to stand for a predetermined time in a humid atmosphere
(temperature 60.degree. C., humidity 90% RH), and thereafter the
brightnesses of the test specimen before and after the test were
compared. The brightness (L value) of the test specimen was
measured using a spectroscopic color-difference meter (TC-1800;
Tokyo Denshoku Co., Ltd.). Each chemically treated steel sheet was
evaluated as follows: when brightness difference .DELTA.L was 3.0
or less, the evaluation was "A"; when the brightness difference
.DELTA.L was more than 3.0 to 6.0 or less, the evaluation was "B";
when the brightness difference .DELTA.L was more than 6.0 to less
than 10.0, the evaluation was "C"; and when the brightness
difference .DELTA.L was 10.0 or more, the evaluation was "D."
[0093] (7) Evaluation Results
[0094] The chemical treatment solutions used, the ratio of each
element in the chemical conversion film, the results of the
corrosion resistance test, and the results of the blackening
resistance test for each chemically treated steel sheet are shown
in Tables 5-1, 5-2, 6-1, and 6-2. Note that, in the following
tables, the ratio of each element in the chemical conversion film
is represented as parts by mass of each element based on 100 parts
by mass of zirconium.
TABLE-US-00008 TABLE 5-1 Ratio of Each Element in Chemical
Chemically Treated Chemical Film Drying Conversion Film Steel Sheet
Treatment Solution Deposition Amount Temperature (Parts by Mass)
Category No. No. (mg/m.sup.2) (.degree. C.) Mo V P Ex. 1 1 200 40
1.5 2.0 5.0 Comp. Ex. 2 2 200 40 0.4 2.0 5.0 Ex. 3 3 200 40 1.5 0.2
5.0 Ex. 4 4 200 40 1.5 2.0 1.0 Comp. Ex. 5 5 200 40 100.0 2.0 5.0
Ex. 6 6 200 40 30.1 40.0 5.0 Ex. 7 7 200 40 1.5 2.0 120.0 Comp. Ex.
8 8 200 40 1.5 2.0 5.0 Ex. 9 1 200 80 1.5 2.0 5.0 Comp. Ex. 10 2
200 80 0.4 2.0 5.0 Ex. 11 3 200 80 1.5 0.2 5.0 Ex. 12 4 200 80 1.5
2.0 1.0 Comp. Ex. 13 5 200 80 100.0 2.0 5.0 Ex. 14 6 200 80 30.1
40.0 5.0 Ex. 15 7 200 80 1.5 2.0 120.0 Comp. Ex. 16 8 200 80 1.5
2.0 5.0
TABLE-US-00009 TABLE 5-2 Chemically Treated Chemical Evaluation
Results Steel Sheet Treatment Solution V.sup.5+ Corrosion
Resistance Blackening Category No. No. Percentage Flat Part Worked
Part Resistance Ex. 1 1 0.92 A A A Comp. Ex. 2 2 0.40 D D D Ex. 3 3
0.88 B B B Ex. 4 4 0.79 B B A Comp. Ex. 5 5 0.45 C D D Ex. 6 6 0.95
A B A Ex. 7 7 0.75 B B A Comp. Ex. 8 8 0.40 C C D Ex. 9 1 0.95 A A
A Comp. Ex. 10 2 0.41 D D D Ex. 11 3 0.91 B B B Ex. 12 4 0.81 B B A
Comp. Ex. 13 5 0.46 C D D Ex. 14 6 0.98 A B A Ex. 15 7 0.77 B B A
Comp. Ex. 16 8 0.41 C C D
TABLE-US-00010 TABLE 6-1 Ratio of Each Element in Chemically
Chemically Treated Chemical Film Drying Treated Film Steel Sheet
Treatment Solution Deposition Amount Temperature (Parts by Mass)
Category No. No. (mg/m.sup.2) (.degree. C.) Mo V P Ex. 17 9 200 40
60.0 20.0 50.0 Comp. Ex. 18 10 200 40 3.8 20.0 50.0 Comp. Ex. 19 11
200 40 0.0 20.0 50.0 Ex. 20 12 200 40 0.2 0.1 50.0 Ex. 21 13 200 40
60.0 20.0 5.0 Ex. 22 14 200 40 113.0 20.0 50.0 Comp. Ex. 23 15 200
40 226.0 20.0 50.0 Ex. 24 16 200 40 60.0 25.0 50.0 Ex. 25 17 200 40
60.0 20.0 150.0 Comp. Ex. 26 18 200 40 60.0 20.0 50.0 Ex. 27 9 200
80 60.0 20.0 50.0 Comp. Ex. 28 10 200 80 3.8 20.0 50.0 Comp. Ex. 29
11 200 80 0.0 20.0 50.0 Ex. 30 12 200 80 0.2 0.1 50.0 Ex. 31 13 200
80 60.0 20.0 5.0 Ex. 32 14 200 80 113.0 20.0 50.0 Comp. Ex. 33 15
200 80 226.0 20.0 50.0 Ex. 34 16 200 80 60.0 25.0 50.0 Ex. 35 17
200 80 60.0 20.0 150.0 Comp. Ex. 36 18 200 80 60.0 20.0 50.0
TABLE-US-00011 TABLE 6-2 Evaluation Results Chemically Treated
Chemical Corrosion Steel Sheet Treatment Solution V.sup.5+
Resistance Blackening Category No. No. Percentage Flat Part Worked
Part Resistance Ex. 17 9 0.92 A A A Comp. Ex. 18 10 0.43 C C D
Comp. Ex. 19 11 0.35 C C D Ex. 20 12 0.95 B B B Ex. 21 13 0.92 B B
A Ex. 22 14 0.86 A B A Comp. Ex. 23 15 0.25 C D D Ex. 24 16 0.85 A
B A Ex. 25 17 0.90 B B A Comp. Ex. 26 18 0.32 C C D Ex. 27 9 0.95 A
A A Comp. Ex. 28 10 0.44 C C D Comp. Ex. 29 11 0.36 C C D Ex. 30 12
0.98 B B B Ex. 31 13 0.95 B B A Ex. 32 14 0.89 B D B Comp. Ex. 33
15 0.26 C D D Ex. 34 16 0.88 A B A Ex. 35 17 0.93 B B A Comp. Ex.
36 18 0.33 C C D
[0095] As is obvious from Tables 5-1, 5-2, 6-1, and 6-2, chemically
treated steel sheets each having a chemical conversion film in
which the percentage of pentavalent vanadium based on mixed-valent
vanadium in the chemical conversion film is 0.7 or more, and which
includes a first chemical conversion layer containing vanadium,
molybdenum and phosphorus, and a second chemical conversion layer
disposed on the first chemical conversion layer and containing a
group 4A metal oxoate, the chemical conversion film being disposed
on the surface of a zinc-based plated steel sheet having a
zinc-based plating layer containing 0.1 to 22.0 mass % of aluminum
have favorable corrosion resistance and blackening resistance. The
chemical conversion film is obtained by applying a chemical
treatment solution which contains a water-soluble molybdate, a
vanadium salt, an amine, a group 4A metal oxoate, and a phosphate,
in which the molar ratio of molybdenum to vanadium is 0.4 to 5.5,
and the molar ratio of an amine to vanadium is 0.3 or more to the
zinc-based plated steel sheet, followed by drying. The favorable
corrosion resistance and blackening resistance of the chemically
treated steel sheets are obtained even when the chemical treatment
solution applied to the plated steel sheet is dried at a relatively
low drying temperature of 40.degree. C. or 80.degree. C.
[0096] In addition, as is obvious from Tables 5-1, 5-2, 6-1, and
6-2, when the percentage of pentavalent vanadium in the chemical
conversion film is 0.7 or less, corrosion resistance and blackening
resistance are inferior.
Example 2
[0097] Next, chemically treated steel sheets Nos. 37 to 100 were
produced in the same manner as chemical treated steel sheet No. 1
except that the type and the deposition amount of the chemical
treatment solutions were changed as shown in the following tables,
and were evaluated in the same manner as chemically treated steel
sheets Nos. 1 to 36. The results are shown in the following Tables
7-1, 7-2, 8-1, 8-2, 9-1, 9-2, 10-1, and 10-2.
TABLE-US-00012 TABLE 7-1 Ratio of Each Element Chemically Treated
Chemical Film Drying in Chemically Treated Film Steel Sheet
Treatment Solution Deposition Amount Temperature (Parts by Mass)
Category No. No. (mg/m.sup.2) (.degree. C.) Mo V P Ex. 37 19 200 40
56.5 20.0 50.0 Ex. 38 20 500 40 1.9 2.0 50.0 Ex. 39 21 500 40 60.0
20.0 1.3 Ex. 40 22 100 40 480.0 160.0 5.0 Ex. 41 23 300 40 60.0
20.0 50.0 Ex. 42 24 1000 40 42.2 14.9 1.8 Ex. 43 25 500 40 39.6 6.0
5.0 Ex. 44 26 400 40 0.5 0.7 42.9 Ex. 45 27 250 40 60.0 20.0 50.0
Ex. 46 28 100 40 94.2 11.1 1.9 Ex. 47 29 150 40 2.0 2.2 1.1 Ex. 48
30 50 40 131.8 20.0 5.0 Ex. 49 31 100 40 46.7 26.7 6.7 Ex. 50 32
400 40 1.5 2.0 5.0 Ex. 51 33 250 40 3.5 1.3 1.3 Ex. 52 34 10000 40
0.2 0.3 1.3
TABLE-US-00013 TABLE 7-2 Chemically Treated Chemical Evaluation
Results Steel Sheet Treatment Solution V5+ Corrosion Resistance
Blackening Category No. No. Percentage Flat Part Worked Part
Resistance Ex. 37 19 0.87 B B A Ex. 38 20 0.93 A A A Ex. 39 21 0.96
B B A Ex. 40 22 0.92 B B A Ex. 41 23 0.91 B B A Ex. 42 24 0.89 A B
A Ex. 43 25 0.85 B A A Ex. 44 26 0.93 B B B Ex. 45 27 0.76 B B A
Ex. 46 28 0.79 B B A Ex. 47 29 0.91 B A A Ex. 48 30 0.86 A B A Ex.
49 31 0.98 B A A Ex. 50 32 0.86 B B A Ex. 51 33 0.70 A B A Ex. 52
34 0.95 B A B
TABLE-US-00014 TABLE 8-1 Ratio of Each Element Chemically Treated
Chemical Film Drying in Chemically Treated Film Steel Sheet
Treatment Solution Deposition Amount Temperature (Parts by Mass)
Category No. No. (mg/m.sup.2) (.degree. C.) Mo V P Ex. 53 35 1000
40 75.3 16.0 5.0 Ex. 54 36 300 40 71.6 23.9 1.5 Ex. 55 37 300 40
25.0 14.3 3.6 Ex. 56 38 150 40 0.2 0.3 1.5 Ex. 57 39 1000 40 7.8
0.8 50.0 Ex. 58 40 500 40 36.7 39.0 2.4 Ex. 59 41 100 40 60.0 20.0
50.0 Ex. 60 42 300 40 0.2 0.3 50.0 Ex. 61 43 150 40 9.4 10.0 5.0
Ex. 62 44 50 40 51.6 17.2 1.1 Ex. 63 45 200 40 87.2 18.5 27.8 Ex.
64 46 300 40 480.0 160.0 5.0 Ex. 65 47 50 40 0.2 0.3 50.0 Ex. 66 48
200 40 0.3 0.4 27.8 Ex. 67 49 250 40 1.5 2.0 5.0 Ex. 68 50 50 40
188.3 40.0 80.0
TABLE-US-00015 TABLE 8-2 Chemically Treated Chemical Evaluation
Results Steel Sheet Treatment Solution V5+ Corrosion Resistance
Blackening Category No. No. Percentage Flat Part Worked Part
Resistance Ex. 53 35 0.83 A B A Ex. 54 36 0.79 A B A Ex. 55 37 0.75
B A A Ex. 56 38 0.78 A A B Ex. 57 39 0.71 B A B Ex. 58 40 0.93 A B
A Ex. 59 41 0.85 A A A Ex. 60 42 0.98 B A B Ex. 61 43 0.85 B B A
Ex. 62 44 0.79 A B A Ex. 63 45 0.99 A A A Ex. 64 46 0.97 B B A Ex.
65 47 0.90 B A B Ex. 66 48 0.73 B A B Ex. 67 49 0.86 B B A Ex. 68
50 0.71 B B A
TABLE-US-00016 TABLE 9-1 Ratio of Each Element Chemically Treated
Chemical Film Drying in Chemically Treated Film Steel Sheet
Treatment Solution Deposition Amount Temperature (Parts by Mass)
Category No. No. (mg/m.sup.2) (.degree. C.) Mo V P Ex. 69 19 200 80
56.5 20.0 50.0 Ex. 70 20 500 80 1.9 2.0 50.0 Ex. 71 21 500 80 60.0
20.0 1.3 Ex. 72 22 100 80 480.0 160.0 5.0 Ex. 73 23 300 80 60.0
20.0 50.0 Ex. 74 24 1000 80 42.2 14.9 1.8 Ex. 75 25 500 80 39.6 6.0
5.0 Ex. 76 26 400 80 0.5 0.7 42.9 Ex. 77 27 250 80 60.0 20.0 50.0
Ex. 78 28 100 80 94.2 11.1 1.9 Ex. 79 29 150 80 2.0 2.2 1.1 Ex. 80
30 50 80 131.8 20.0 5.0 Ex. 81 31 100 80 46.7 26.7 6.7 Ex. 82 32
400 80 1.5 2.0 5.0 Ex. 83 33 250 80 3.5 1.3 1.3 Ex. 84 34 10000 80
0.2 0.3 1.3
TABLE-US-00017 TABLE 9-2 Chemically Treated Chemical Evaluation
Results Steel Sheet Treatment Solution V5+ Corrosion Resistance
Blackening Category No. No. Percentage Flat Part Worked Part
Resistance Ex. 69 19 0.87 B B A Ex. 70 20 0.93 A A A Ex. 71 21 0.73
B B A Ex. 72 22 0.86 B B A Ex. 73 23 0.73 B B A Ex. 74 24 0.73 A B
A Ex. 75 25 0.89 B A A Ex. 76 26 0.72 B B B Ex. 77 27 0.75 B B A
Ex. 78 28 0.81 B B A Ex. 79 29 0.75 B A A Ex. 80 30 0.84 A B A Ex.
81 31 0.77 B A A Ex. 82 32 0.81 B B A Ex. 83 33 0.92 A B A Ex. 84
34 0.72 B A B
TABLE-US-00018 TABLE 10-1 Ratio of Each Element Chemically Treated
Chemical Film Drying in Chemically Treated Film Steel Sheet
Treatment Solution Deposition Amount Temperature (Parts by Mass)
Category No. No. (mg/m.sup.2) (.degree. C.) Mo V P Ex. 85 35 1000
80 75.3 16.0 5.0 Ex. 86 36 300 80 71.6 23.9 1.5 Ex. 87 37 300 80
25.0 14.3 3.6 Ex. 88 38 150 80 0.2 0.3 1.5 Ex. 89 39 1000 80 7.8
0.8 50.0 Ex. 90 40 500 80 36.7 39.0 2.4 Ex. 91 41 100 80 60.0 20.0
50.0 Ex. 92 42 300 80 0.2 0.3 50.0 Ex. 93 43 150 80 9.4 10.0 5.0
Ex. 94 44 50 80 51.6 17.2 1.1 Ex. 95 45 200 80 87.2 18.5 27.8 Ex.
96 46 300 80 480.0 160.0 5.0 Ex. 97 47 50 80 0.2 0.3 50.0 Ex. 98 48
200 80 0.3 0.4 27.8 Ex. 99 49 250 80 1.5 2.0 5.0 Ex. 100 50 50 80
188.3 40.0 80.0
TABLE-US-00019 TABLE 10-2 Chemically Treated Chemical Evaluation
Results Steel Sheet Treatment Solution V5+ Corrosion Resistance
Blackening Category No. No. Percentage Flat Part Worked Part
Resistance Ex. 85 35 0.90 A B A Ex. 86 36 0.71 A B A Ex. 87 37 0.89
B A A Ex. 88 38 0.97 A A B Ex. 89 39 0.82 B A B Ex. 90 40 0.77 A B
A Ex. 91 41 0.90 A A A Ex. 92 42 0.86 B A B Ex. 93 43 0.70 B B A
Ex. 94 44 0.98 A B A Ex. 95 45 0.98 A A A Ex. 96 46 0.79 B B A Ex.
97 47 0.95 B A B Ex. 98 48 0.81 B A B Ex. 99 49 0.90 B B A Ex. 100
50 0.79 B B A
[0098] As is obvious from Tables 7-1, 7-2, 8-1, 8-2, 9-1, 9-2,
10-1, and 10-2, chemically treated steel sheets each having a
chemical conversion film in which the percentage of pentavalent
vanadium based on mixed-valent vanadium in the chemical conversion
film is 0.7 or more, and which includes a first chemical conversion
layer containing vanadium, molybdenum and phosphorus, and a second
chemical conversion layer disposed on the first chemical conversion
layer and containing a group 4A metal oxoate, the chemical
conversion film being disposed on the surface of a zinc-based
plated steel sheet having a zinc-based plating layer containing 0.1
to 22.0 mass % of aluminum have favorable corrosion resistance and
blackening resistance in a wide range of the deposition amount of
the chemical conversion film. The chemical conversion film is
obtained by applying a chemical treatment solution which contains a
water-soluble molybdate, a vanadium salt, an amine, a group 4A
metal oxoate, and a phosphate, in which the molar ratio of
molybdenum to vanadium is 0.4 to 5.5, and the molar ratio of an
amine to vanadium is 0.3 or more to the zinc-based plated steel
sheet, followed by drying. The favorable corrosion resistance and
blackening resistance of the chemically treated steel sheets are
obtained, regardless of the deposition amount of the chemical
conversion film, even when the chemical treatment solution applied
to the plated steel sheet is dried at a relatively low drying
temperature of 40 or 80.degree. C.
[0099] Next, chemically treated steel sheets Nos. 101 to 106 which
were comparative materials were prepared in the same manner as
chemical treated steel sheet No. 1 except that the chemical
treatment solutions were respectively changed to prior arts A to C,
and were evaluated in the same manner as Example 1 according to the
above-mentioned evaluation criteria. The results are shown in the
following Tables 11-1 and 11-2.
[0100] [Prior Art A]
[0101] Commercially available partially reduced chromate treatment
solution (ZM-3387; Nihon Parkerizing Co., Ltd.) was applied to the
surface of an original sheet for chemical treatment, and
immediately thereafter heated and dried at a low temperature (a
temperature of the steel strip of 40 or 80.degree. C.) using an
automatic discharge type electric hot air oven to form a chemical
conversion film. Note that the chrome deposition amount of the
chemical conversion film was 200 mg/m.sup.2.
[0102] [Prior Art B]
[0103] A blue transparent chemical treatment solution to which
ammonium zirconium carbonate, vanadyl tartrate, phosphoric acid and
citric acid were added was applied to the surface of an original
sheet for chemical treatment, and immediately thereafter heated and
dried at a low temperature (a temperature of the steel strip of 40
or 80.degree. C.) using an automatic discharge type electric hot
air oven to form a chemical conversion film. The vanadyl tartrate
was prepared by reducing vanadium pentoxide in an aqueous tartaric
acid solution. Note that the zirconium deposition amount and the
vanadium deposition amount of the chemical conversion film were
both 200 mg/m.sup.2.
[0104] [Prior Art C]
[0105] A colorless transparent chemical treatment solution to which
titanium hydrofluoric acid and phosphoric acid were added was
applied to the surface of an original sheet for chemical treatment,
and immediately thereafter heated and dried at a low temperature (a
temperature of the steel strip of 40 or 80.degree. C.) using an
automatic discharge type electric hot air oven to form a chemical
conversion film. Note that the titanium deposition amount of the
chemical conversion film was 200 mg/m.sup.2.
TABLE-US-00020 TABLE 11-1 Ratio of Each Element Chemically Treated
Chemical Film Drying in Chemically Treated Film Steel Sheet
Treatment Solution Deposition Amount Temperature (Parts by Mass)
Category No. No. (mg/m.sup.2) (.degree. C.) Mo V P Comp. Ex. 101
Prior Art A 200 40 -- -- -- Comp. Ex. 102 Prior Art A 200 80 -- --
-- Comp. Ex. 103 Prior Art B 200 40 -- -- -- Comp. Ex. 104 Prior
Art B 200 80 -- -- -- Comp. Ex. 105 Prior Art C 200 40 -- -- --
Comp. Ex. 106 Prior Art C 200 80 -- -- --
TABLE-US-00021 TABLE 11-2 Chemically Treated Chemical Evaluation
Results Steel Sheet Treatment Solution V5+ Corrosion Resistance
Blackening Category No. No. Percentage Flat Part Worked Part
Resistance Comp. Ex. 101 Prior Art A -- C D A Comp. Ex. 102 Prior
Art A -- C D A Comp. Ex. 103 Prior Art B -- D D D Comp. Ex. 104
Prior Art B -- C D D Comp. Ex. 105 Prior Art C -- D D D Comp. Ex.
106 Prior Art C -- C D D
[0106] The chemically treated steel sheets Nos. 101 and 102
obtained by using the commercially available chromate treatment
solution were inferior in flat part corrosion resistance and worked
part corrosion resistance, since the chemical treatment solution
was dried at a low temperature. Further, the chemically treated
steel sheets Nos. 103 to 106 obtained by using the chemical
treatment solution in which vanadium was reduced with the addition
of an organic acid or the chemical treatment solution containing a
fluoride were each markedly inferior in flat part corrosion
resistance, worked part corrosion resistance and blackening
resistance, since the chemical treatment solutions were dried at a
low temperature.
[0107] As described above, it can be found, from the comparison
between the test results of prior arts shown in Tables 11-1, 11-2
and Examples shown in Tables 5-1, 5-2, 6-1, 6-2, 7-1, 7-2, 8-1,
8-2, 9-1, 9-2, 10-1, 10-2, that the chemically treated steel sheet
according to the present invention has favorable corrosion
resistance and blackening resistance compared to that of the prior
arts. Further, it can be found that the chemically treated steel
sheet is obtained by the production of a chemical conversion film
made from the chemical treatment solution according to the present
invention. Furthermore, it can be found that the favorable
corrosion resistance and blackening resistance are also obtained by
drying the chemical treatment solution at a low temperature.
Example 3
[0108] A chemically treated steel sheet produced according to the
following procedure was provided. For an original sheet for
chemical treatment, a steel strip of ultra-low carbon
titanium-added steel having a sheet thickness of 0.5 mm was used as
the substrate steel to produce a hot-dip zinc plated steel sheet of
having a zinc-based layer containing 0.018 mass % of aluminum
(plating deposition amount of 90 g/m.sup.2 per side), in a
continuous hot-dip zinc plating production line, and the produced
plated steel sheet was used as the original sheet for chemical
treatment.
[0109] The surface of the original sheet for chemical treatment was
degreased, and dried. Then, each of chemical treatment solutions
Nos. 19 to 50 shown in Tables 2-1, 2-2, 3-1, 3-2, 4-1, and 4-2 was
applied to the surface of the original sheet for chemical
treatment, and immediately thereafter heated and dried at a low
temperature (a temperature of the steel strip of 40 or 80.degree.
C.) using an automatic discharge type electric hot air oven to form
a chemical conversion film. Thus, chemically treated steel sheets
Nos. 107 to 170 were produced.
[0110] For a test specimen cut out from each chemically treated
steel sheet, the structure of the chemical conversion film was
identified; the percentage of pentavalent vanadium based on
mixed-valent vanadium in the film was determined; the film
deposition amount was measured; and the test specimen was subjected
to corrosion resistance test and blackening resistance test. The
chemical treatment solutions used, the ratio of each element in the
chemical conversion film, the results of the corrosion resistance
test, and the results of the blackening resistance test for each
chemically treated steel sheet are shown in Tables 12-1, 12-2,
13-1, 13-2, 14-1, 14-2, 15-1, and 15-2. Note that the ratio of each
element in the chemical conversion film is represented as parts by
mass of each element based on 100 parts by mass of zirconium.
TABLE-US-00022 TABLE 12-1 Ratio of Each Element Chemically Treated
Chemical Film Drying in Chemically Treated Film Steel Sheet
Treatment Solution Deposition Amount Temperature (Parts by Mass)
Category No. No. (mg/m.sup.2) (.degree. C.) Mo V P Ex. 107 19 200
40 56.5 20.0 50.0 Ex. 108 20 500 40 1.9 2.0 50.0 Ex. 109 21 500 40
60.0 20.0 1.3 Ex. 110 22 100 40 480.0 160.0 5.0 Ex. 111 23 300 40
60.0 20.0 50.0 Ex. 112 24 1000 40 42.2 14.9 1.8 Ex. 113 25 500 40
39.6 6.0 5.0 Ex. 114 26 400 40 0.5 0.7 42.9 Ex. 115 27 250 40 60.0
20.0 50.0 Ex. 116 28 100 40 94.2 11.1 1.9 Ex. 117 29 150 40 2.0 2.2
1.1 Ex. 118 30 50 40 131.8 20.0 5.0 Ex. 119 31 100 40 46.7 26.7 6.7
Ex. 120 32 400 40 1.5 2.0 5.0 Ex. 121 33 250 40 3.5 1.3 1.3 Ex. 122
34 10000 40 0.2 0.3 1.3
TABLE-US-00023 TABLE 12-2 Chemically Treated Chemical Evaluation
Results Steel Sheet Treatment Solution V5+ Corrosion Resistance
Blackening Category No. No. Percentage Flat Part Worked Part
Resistance Ex. 107 19 0.91 B B A Ex. 108 20 0.78 A A A Ex. 109 21
0.87 B B A Ex. 110 22 0.82 B B A Ex. 111 23 0.88 B B A Ex. 112 24
0.77 B B A Ex. 113 25 0.73 B B A Ex. 114 26 0.99 B B B Ex. 115 27
0.73 B B A Ex. 116 28 0.79 B B A Ex. 117 29 0.89 B B A Ex. 118 30
0.91 A B A Ex. 119 31 0.87 B B A Ex. 120 32 0.89 B B A Ex. 121 33
0.74 B B A Ex. 122 34 0.86 B B B
TABLE-US-00024 TABLE 13-1 Ratio of Each Element Chemically Treated
Chemical Film Drying in Chemically Treated Film Steel Sheet
Treatment Solution Deposition Amount Temperature (Parts by Mass)
Category No. No. (mg/m.sup.2) (.degree. C.) Mo V P Ex. 123 35 1000
40 75.3 16.0 5.0 Ex. 124 36 300 40 71.6 23.9 1.5 Ex. 125 37 300 40
25.0 14.3 3.6 Ex. 126 38 150 40 0.2 0.3 1.5 Ex. 127 39 1000 40 7.8
0.8 50.0 Ex. 128 40 500 40 36.7 39.0 2.4 Ex. 129 41 100 40 60.0
20.0 50.0 Ex. 130 42 300 40 0.2 0.3 50.0 Ex. 131 43 150 40 9.4 10.0
5.0 Ex. 132 44 50 40 51.6 17.2 1.1 Ex. 133 45 200 40 87.2 18.5 27.8
Ex. 134 46 300 40 480.0 160.0 5.0 Ex. 135 47 50 40 0.2 0.3 50.0 Ex.
136 48 200 40 0.3 0.4 27.8 Ex. 137 49 250 40 1.5 2.0 5.0 Ex. 138 50
50 40 188.3 40.0 80.0
TABLE-US-00025 TABLE 13-2 Chemically Treated Chemical Evaluation
Results Steel Sheet Treatment Solution V5+ Corrosion Resistance
Blackening Category No. No. Percentage Flat Part Worked Part
Resistance Ex. 123 35 0.90 A B A Ex. 124 36 0.82 B B A Ex. 125 37
0.82 B B A Ex. 126 38 0.87 A A B Ex. 127 39 0.90 B B B Ex. 128 40
0.77 B B A Ex. 129 41 0.77 A A A Ex. 130 42 0.77 B B B Ex. 131 43
0.85 B B A Ex. 132 44 0.80 B B A Ex. 133 45 0.77 A A A Ex. 134 46
0.79 B B A Ex. 135 47 0.80 B B B Ex. 136 48 0.74 B B B Ex. 137 49
0.81 B B A Ex. 138 50 0.93 A A A
TABLE-US-00026 TABLE 14-1 Ratio of Each Element Chemically Treated
Chemical Film Drying in Chemically Treated Film Steel Sheet
Treatment Solution Deposition Amount Temperature (Parts by Mass)
Category No. No. (mg/m.sup.2) (.degree. C.) Mo V P Ex. 139 19 200
80 56.5 20.0 50.0 Ex. 140 20 500 80 1.9 2.0 50.0 Ex. 141 21 500 80
60.0 20.0 1.3 Ex. 142 22 100 80 480.0 160.0 5.0 Ex. 143 23 300 80
60.0 20.0 50.0 Ex. 144 24 1000 80 42.2 14.9 1.8 Ex. 145 25 500 80
39.6 6.0 5.0 Ex. 146 26 400 80 0.5 0.7 42.9 Ex. 147 27 250 80 60.0
20.0 50.0 Ex. 148 28 100 80 94.2 11.1 1.9 Ex. 149 29 150 80 2.0 2.2
1.1 Ex. 150 30 50 80 131.8 20.0 5.0 Ex. 151 31 100 80 46.7 26.7 6.7
Ex. 152 32 400 80 1.5 2.0 5.0 Ex. 153 33 250 80 3.5 1.3 1.3 Ex. 154
34 10000 80 0.2 0.3 1.3
TABLE-US-00027 TABLE 14-2 Evaluation Results Chemically Chemical
Corrosion Treated Treatment V.sup.5+ Resistance Cate- Steel Sheet
Solution Per- Flat Worked Blackening gory No. No. centage Part Part
Resistance Ex. 139 19 0.73 B B A Ex. 140 20 0.78 A A A Ex. 141 21
0.78 B B A Ex. 142 22 0.78 B B A Ex. 143 23 0.86 B B A Ex. 144 24
0.74 B B A Ex. 145 25 0.90 B B A Ex. 146 26 0.85 B B B Ex. 147 27
0.87 B B A Ex. 148 28 0.91 B B A Ex. 149 29 0.95 B B A Ex. 150 30
0.79 A B A Ex. 151 31 0.91 B B A Ex. 152 32 0.78 B B A Ex. 153 33
0.94 B B A Ex. 154 34 0.94 B B B
TABLE-US-00028 TABLE 15-1 Chemi- Ratio of cally Each Element
Treated Chemical Film Drying in Chemically Steel Treatment
Deposition Temper- Treated Film Cate- Sheet Solution Amount ature
(Parts by Mass) gory No. No. (mg/m.sup.2) (.degree. C.) Mo V P Ex.
155 35 1000 80 75.3 16.0 5.0 Ex. 156 36 300 80 71.6 23.9 1.5 Ex.
157 37 300 80 25.0 14.3 3.6 Ex. 158 38 150 80 0.2 0.3 1.5 Ex. 159
39 1000 80 7.8 0.8 50.0 Ex. 160 40 500 80 36.7 39.0 2.4 Ex. 161 41
100 80 60.0 20.0 50.0 Ex. 162 42 300 80 0.2 0.3 50.0 Ex. 163 43 150
80 9.4 10.0 5.0 Ex. 164 44 50 80 51.6 17.2 1.1 Ex. 165 45 200 80
87.2 18.5 27.8 Ex. 166 46 300 80 480.0 160.0 5.0 Ex. 167 47 50 80
0.2 0.3 50.0 Ex. 168 48 200 80 0.3 0.4 27.8 Ex. 169 49 250 80 1.5
2.0 5.0 Ex. 170 50 50 80 188.3 40.0 80.0
TABLE-US-00029 TABLE 15-2 Evaluation Results Chemically Chemical
Corrosion Treated Treatment V.sup.5+ Resistance Cate- Steel Sheet
Solution Per- Flat Worked Blackening gory No. No. centage Part Part
Resistance Ex. 155 35 0.91 A B A Ex. 156 36 0.82 B B A Ex. 157 37
0.82 B B A Ex. 158 38 0.86 A A B Ex. 159 39 0.84 B B B Ex. 160 40
0.87 B B A Ex. 161 41 0.78 A A A Ex. 162 42 0.84 B B B Ex. 163 43
0.96 B B A Ex. 164 44 0.82 B B A Ex. 165 45 0.82 A A A Ex. 166 46
0.74 B B A Ex. 167 47 0.68 B B B Ex. 168 48 0.83 B B B Ex. 169 49
0.87 B B A Ex. 170 50 0.78 A A A
[0111] As is obvious from Tables 12-1, 12-2, 13-1, 13-2, 14-1,
14-2, 15-1, and 15-2, it can be found that all chemically treated
steel sheets each having a chemical conversion film in which the
percentage of pentavalent vanadium based on mixed-valent vanadium
in the chemical conversion film is 0.7 or more, and which includes
a first chemical conversion layer containing vanadium, molybdenum
and phosphorus, and a second chemical conversion layer disposed on
the first chemical conversion layer and containing a group 4A metal
oxoate, the chemical conversion film being disposed on the surface
of a zinc-based plated steel sheet having a zinc-based plating
layer containing 0.1 to 22.0 mass % of aluminum have favorable
corrosion resistance and blackening resistance. The chemical
conversion film is obtained by applying a chemical treatment
solution which contains a water-soluble molybdate, a vanadium salt,
an amine, a group 4A metal oxoate, and a phosphate, in which the
molar ratio of molybdenum to vanadium is 0.4 to 5.5, and the molar
ratio of an amine to vanadium is 0.3 or more to the zinc-based
plated steel sheet, followed by drying. The favorable corrosion
resistance and blackening resistance of the chemically treated
steel sheets are obtained in a wide range of the deposition amount
of the chemical conversion film, even when the chemical treatment
solution is dried at a relatively low drying temperature.
[0112] It can be found, from the above-mentioned results, that the
chemically treated steel sheet of the present invention is
excellent in worked part corrosion resistance and blackening
resistance even when the chemical treatment solution is dried at a
low temperature and for a short period of time.
Example 4
Preparation of Chemical Treatment Solution No. 51
[0113] Ammonium molybdate, vanadium pentoxide, ethanolamine,
ammonium zirconium carbonate (AZC), diammonium hydrogen phosphate,
which are shown in Table 1, and water were mixed such that the
concentrations are as shown in Tables 16-1 and 16-2 to obtain
chemical treatment solution No. 51. The composition and color of
each chemical treatment solution are shown in Tables 16-1 and 16-2.
In Table 16-2, "Mo/V" indicates the molar ratio of a molybdenum
element to a vanadium element, and "amine/V" indicates the molar
ratio of an amine to a vanadium element.
[0114] [Preparation of Chemical Treatment Solutions Nos. 52 to
57]
[0115] Chemical treatment solutions Nos. 52 to 57 were each
obtained in the same manner as chemical treatment solution No. 51
except that molybdenum concentration, the type of the vanadium salt
and vanadium concentration, the type and concentration of the
amine, zirconium concentration, and the type of the phosphate and
phosphate concentration were changed as shown in Tables 16-1 and
16-2.
TABLE-US-00030 TABLE 16-1 Chemical M1 Vanadium Salt Treatment Mo V
Amine Solution Conc. Conc. Com- Conc. No. (g/L) Compound (g/L)
pound (g/L) Category 51 0.075 V1 0.10 EA 0.036 Ex. 52 0.075 V2 0.10
NH 0.021 53 24.0 V2 8.00 EA 15.3 54 1.98 V3 0.30 EA 1.15 55 3.11 V3
0.30 IPA 1.06 56 24.0 V2 8.00 NH 8.79 57 14.1 V2 0.30 EN 5.75
TABLE-US-00031 TABLE 16-2 Chemical AZC Phosphate Amine/ Treatment
Zr P Mo/V V Color of Solution Conc. Com- Conc. (Molar (Molar
Treatment Cate- No. (g/L) pound (g/L) Ratio) Ratio) Solution gory
51 5.0 P1 0.25 0.40 0.30 Yellow Ex. 52 5.0 P5 0.05 0.40 0.30 Yellow
53 40.0 P4 2.00 1.59 1.60 Yellow 54 5.0 P3 0.25 3.50 3.20 Yellow 55
40.0 P4 20.0 5.50 2.40 Yellow 56 46.5 P2 0.50 1.59 1.60 Yellow 57
7.5 P4 6.00 2.50 1.60 Yellow
[0116] [Preparation of Chemical Treatment Solutions Nos. 58 to
64]
[0117] Chemical treatment solutions Nos. 58 to 64 were each
obtained in the same manner as chemical treatment solutions Nos. 1
to 57 except that an organic resin as a hydrophilic resin is
further mixed such that the organic resin has a concentration as
shown in Tables 17-1 and 17-2. In Table 17-2, "AR" indicates
denotes an acrylic resin, "PO" denotes a polyolefin, "ER" denotes
an epoxy resin, and "PU" denotes polyurethane. In addition, the
amount of an organic resin in Table 17-2 is the amount (mass %) of
an organic resin based on the total amount of vanadium and
molybdenum in the chemical treatment solution.
[0118] It is noted that "Voncoat 40-418EF" manufactured by DIC
Corporation (the "Voncoat" is a registered trademark of this
company) was used as "acrylic resin"; "Zaikthene" A type-AC
manufactured by Sumitomo Seika Chemicals Co., Ltd. ("Zaikthene" is
a registered trademark of this company) was used as "polyolefin";
"Adeka Resin EM-0434AN" manufactured by Adeka Corporation ("Adeka
Resin" is a registered trademark of this company) was used as
"epoxy resin"; and "Adeka Bontighter HUX-232" manufactured by Adeka
Corporation ("Adeka Bontighter" is a registered trademark of this
company) was used as "polyurethane."
[0119] [Preparation of Chemical Treatment Solutions Nos. 65 and
66]
[0120] Chemical treatment solutions Nos. 65 and 66 were each
obtained in the same manner as chemical treatment solution No. 51
except that molybdenum concentration, the type of the vanadium salt
and vanadium concentration, the type and concentration of the
amine, zirconium concentration, the type of the phosphate and
phosphate concentration, and the type and concentration of the
organic resin were changed as shown in Tables 17-1 and 17-2.
TABLE-US-00032 TABLE 17-1 Chemical M1 Vanadium Salt AZC Treatment
Mo V Amine Zr Solution Conc. Com- Conc. Com- Conc. Conc. Cate- No.
(g/L) pound (g/L) pound (g/L) (g/L) gory 58 0.075 V1 0.10 EA 0.036
5.0 Comp. Ex. 59 0.075 V2 0.10 NH 0.021 5.0 Comp. Ex. 60 24.0 V2
8.00 EA 15.3 40.0 Ex. 61 1.98 V3 0.30 EA 1.15 5.0 Comp. Ex. 62 3.11
V3 0.30 IPA 1.06 40.0 Ex. 63 24.0 V2 8.00 NH 8.79 46.5 Ex. 64 14.1
V2 0.30 EN 5.75 7.5 Comp. Ex. 65 1.00 V1 0.30 IPA 2.00 1.0 Comp.
Ex. 66 1.00 V1 0.30 IPA 2.00 1.0 Comp. Ex.
TABLE-US-00033 TABLE 17-2 Phosphate Chemical P Organic Resin Color
of Treatment Solution Conc. Conc. Amount Mo/V Amine/V Treatment No.
Compound (g/L) Compound (g/L) (mass %) (Molar Ratio) (Molar Ratio)
Solution Category 58 P1 0.25 AR 50.0 28500 0.40 0.30 Yellow Comp.
Ex. 59 P5 0.05 PO 80.0 45600 0.40 0.30 Yellow Comp. Ex. 60 P4 2.00
ER 20.0 63.0 1.59 1.60 Yellow Ex. 61 P3 0.25 AR 5.00 220 3.50 3.20
Yellow Comp. Ex. 62 P4 20.0 PO 0.50 15.0 5.50 2.40 Yellow Ex. 63 P2
0.50 ER 20.0 63.0 1.59 1.60 Yellow Ex. 64 P4 6.00 PU 200 1170 2.50
1.60 Yellow Comp. Ex. 65 -- -- PU 200 13300 0.53 2.72 Yellow Comp.
Ex. 66 P1 1.00 PU 200 13300 0.53 2.72 Yellow Comp. Ex.
[0121] [Preparation of Chemical Treatment Solutions Nos. 67 to
73]
[0122] Chemical treatment solutions Nos. 67 to 73 were each
obtained in the same manner as chemical treatment solutions Nos. 51
to 57 except that a fluorine compound that produces a fluorine ion
or a fluorometal ion in water is further mixed such that the
fluorine compound has a concentration as shown in Tables 18-1 and
18-2. The amount of a fluorine compound in Table 18-2 is the amount
(mass %) of a fluorine element based on the total amount of
vanadium and molybdenum in the chemical treatment solution. The
fluorine element is derived from a fluorine ion or a fluorometal
ion in the chemical treatment solution.
TABLE-US-00034 TABLE 18-1 Chemical M1 Vanadium Salt AZC Treatment
Mo V Amine Zr Solution Conc. Com- Conc. Com- Conc. Conc. Cate- No.
(g/L) pound (g/L) pound (g/L) (g/L) gory 67 0.075 V1 0.10 EA 0.036
5.0 Comp. Ex. 68 0.075 V2 0.10 NH 0.021 5.0 Comp. Ex. 69 24.0 V2
8.00 EA 15.3 40.0 Ex. 70 1.98 V3 0.30 EA 1.15 5.0 Ex. 71 3.11 V3
0.30 IPA 1.06 40.0 Comp. Ex. 72 24.0 V2 8.00 NH 8.79 46.5 Comp. Ex.
73 14.1 V2 0.30 EN 5.75 7.5 Comp. Ex.
TABLE-US-00035 TABLE 18-2 Phosphate Chemical P Fluorine Compound
Color of Treatment Solution Conc. Conc. Amount Mo/V Amine/V
Treatment No. Compound (g/L) Compound (g/L) (mass %) (Molar Ratio)
(Molar Ratio) Solution Category 67 P1 0.25 F1 2.00 373 0.40 0.30
Yellow Comp. Ex. 68 P5 0.05 F2 1.00 570 0.40 0.30 Yellow Comp. Ex.
69 P4 2.00 F3 0.50 2.00 1.59 1.60 Yellow Ex. 70 P3 0.25 F1 0.50
22.0 3.50 3.20 Yellow Ex. 71 P4 20.0 F2 10.0 293 5.50 2.40 Yellow
Comp. Ex. 72 P2 0.50 F3 50.0 156 1.59 1.60 Yellow Comp. Ex. 73 P4
6.00 F1 20.0 117 2.50 1.60 Yellow Comp. Ex.
[0123] [Preparation of Chemical Treatment Solutions Nos. 74 to
80]
[0124] Chemical treatment solutions Nos. 74 to 80 were each
obtained in the same manner as chemical treatment solutions Nos. 51
to 57 except that a silicon compound that produces a silanol group
in water is further mixed such that the silicon compound has a
concentration as shown in Tables 19-1 and 19-2. The amount of a
silicon compound in Table 19-2 is the amount (mass %) of a silicon
element based on the total amount of vanadium and molybdenum in the
chemical treatment solution. The silicon element is derived from a
silanol group in the chemical treatment solution.
TABLE-US-00036 TABLE 19-1 Chemical M1 Vanadium Salt AZC Treatment
Mo V Amine Zr Solution Conc. Com- Conc. Com- Conc. Conc. Cate- No.
(g/L) pound (g/L) pound (g/L) (g/L) gory 74 0.075 V1 0.10 EA 0.036
5.00 Comp. Ex. 75 0.075 V2 0.10 NH 0.021 5.00 Comp. Ex. 76 24.0 V2
8.00 EA 15.327 40.0 Ex. 77 1.98 V3 0.30 EA 1.150 5.00 Comp. Ex. 78
3.11 V3 0.30 IPA 1.060 40.0 Comp. Ex. 79 24.0 V2 8.00 NH 8.794 46.5
Ex. 80 14.1 V2 0.30 EN 5.748 7.50 Comp. Ex.
TABLE-US-00037 TABLE 19-2 Phosphate Chemical P Silicon Compound
Color of Treatment Solution Conc. Conc. Amount Mo/V Amine/V
Treatment No. Compound (g/L) Compound (g/L) (mass %) (Molar Ratio)
(Molar Ratio) Solution Category 74 P1 0.25 S1 2.00 179 0.40 0.30
Yellow Comp. Ex. 75 P5 0.05 S2 5.00 2850 0.40 0.30 Yellow Comp. Ex.
76 P4 2.00 S3 0.20 1.00 1.59 1.60 Yellow Ex. 77 P3 0.25 S1 5.00 220
3.50 3.20 Yellow Comp. Ex. 78 P4 20.0 S2 8.00 235 5.50 2.40 Yellow
Comp. Ex. 79 P2 0.50 S3 10.0 31.0 1.59 1.60 Yellow Ex. 80 P4 6.00
S1 20.0 117 2.50 1.60 Yellow Comp. Ex.
[0125] Note that, in order to prevent vanadium from being reduced
in the preparation of the chemical treatment solution, a vanadium
salt was added to and dissolved in an aqueous solution having a
liquid temperature of 40.degree. C. or lower containing an amine.
It is considered that, since the color of each chemical treatment
solution is yellow, the valence of vanadium contained in each
chemical treatment solution is pentavalent (V.sup.5+).
[0126] [Production of Chemically Treated Steel Sheets Nos. 171 to
200]
[0127] The surface of the original sheet for chemical treatment was
degreased, and dried. Then, chemical treatment solution No. 51
shown in Tables 16-1 and 16-2 was applied to the surface of the
original sheet for chemical treatment in the amount of the
deposition amount of chemical conversion film shown in Table 20-1,
and immediately thereafter heated and dried at a drying temperature
of (a temperature of the steel strip of) 40.degree. C. for 2
seconds using an automatic discharge type electric hot air oven to
form a chemical conversion film. Thus, chemically treated steel
sheet No. 171 was produced.
[0128] Further, chemical treatment solutions Nos. 52 to 80 were
used in place of chemical treatment solution No. 51 to respectively
produce chemically treated steel sheets Nos. 172 to 200 in the same
manner as chemically treated steel sheets No. 51, except that the
chemical treatment solutions were applied to the original sheet for
chemical treatment in the deposition amounts shown in Table 20-1 or
21-1, and heated and dried at a drying temperature shown in Table
20-1 or 21-1. Note that the drying time is 6 seconds when the
drying temperature is 80.degree. C.
[0129] [Measurement and Evaluation of Chemically Treated Steel
Sheets]
[0130] For a test specimen cut out from each chemically treated
steel sheet, the structure of the chemical conversion film was
identified, and the test specimen was subjected to corrosion
resistance test and blackening resistance test in the same manner
as Example 1.
[0131] As a result, it was confirmed, in chemically treated steel
sheets categorized in Examples, that the two-layer structure (i.e.,
first and second chemical conversion layers) similar to chemically
treated steel sheet No. 17, for example, contains vanadium,
molybdenum and phosphorus in the first chemical conversion layer
and a group 4A metal oxoate in the second chemical conversion
layer. However, the two-layer structure in the chemical conversion
film was not confirmed in chemically treated steel sheets
categorized in Comparative Examples.
[0132] The type of chemical treatment solutions, deposition amount,
drying temperature, the content of molybdenum, vanadium and
phosphorus in the chemical conversion film, the percentage of
pentavalent vanadium, and various evaluation results are each shown
in Tables 20-1, 20-2, 21-1, and 21-2. Note that each content ratio
of molybdenum, vanadium and phosphorus indicates parts by mass of
each element based on 100 parts by mass of a zirconium element.
TABLE-US-00038 TABLE 20-1 Ratio of Each Element Chemical Chemical
Depo- Drying in Chemically Treatment Treatment sition Tem- Treated
Film Solution Solution Amount perature (Parts by Mass) Cate- No.
No. (mg/m.sup.2) (.degree. C.) Mo V P gory 171 51 200 40 1.5 2.0
5.0 Ex. 172 52 200 80 1.5 2.0 1.0 Ex. 173 53 200 40 60.0 20.0 5.0
Ex. 174 54 500 40 39.6 6.0 5.0 Ex. 175 55 1000 40 7.8 0.8 50.0 Ex.
176 56 50 40 51.6 17.2 1.1 Ex. 177 57 50 80 188.3 40.0 80.0 Ex. 178
58 200 40 1.5 2.0 5.0 Comp. Ex. 179 59 200 80 1.5 2.0 1.0 Comp. Ex.
180 60 200 40 60.0 20.0 5.0 Ex. 181 61 500 40 39.6 6.0 5.0 Comp.
Ex. 182 62 1000 40 7.8 0.8 50.0 Ex. 183 63 300 40 480.0 160.0 5.0
Ex. 184 64 50 80 188.3 40.0 80.0 Comp. Ex. 185 65 200 80 100.0 50.0
0.0 Comp. Ex. 186 66 200 80 100.0 50.0 100.0 Comp. Ex.
TABLE-US-00039 TABLE 20-2 Evaluation Results Chemical Chemical
Worked Black- Treatment Treatment Flat Part Part ening Solution
Solution V.sup.5+/ Corrosion Corrosion Resis- Cate- No. No. V
Resistance Resistance tance gory 171 51 0.92 A A A Ex. 172 52 0.81
B B A Ex. 173 53 0.92 B B A Ex. 174 54 0.85 A A A Ex. 175 55 0.71 A
A A Ex. 176 56 0.79 A A A Ex. 177 57 0.79 B B A Ex. 178 58 0.85 D D
C Comp. Ex. 179 59 0.71 D D D Comp. Ex. 180 60 0.93 B B A Ex. 181
61 0.63 D D C Comp. Ex. 182 62 0.82 A A A Ex. 183 63 0.95 A A A Ex.
184 64 0.75 D D D Comp. Ex. 185 65 0.72 D D D Comp. Ex. 186 66 0.78
C D D Comp. Ex.
TABLE-US-00040 TABLE 21-1 Chemi- Ratio of cally Each Element
Treated Chemical Depo- Drying in Chemically Steel Treatment sition
Tem- Treated Film Sheet Solution Amount perature (Parts by Mass)
Cate- No. No. (mg/m.sup.2) (.degree. C.) Mo V P gory 187 67 200 40
1.5 2.0 5.0 Comp. Ex. 188 68 200 80 1.5 2.0 1.0 Comp. Ex. 189 69
200 40 60.0 20.0 5.0 Ex. 190 70 500 40 39.6 6.0 5.0 Ex. 191 71 1000
40 7.8 0.8 50.0 Comp. Ex. 192 72 300 40 480.0 160.0 5.0 Comp. Ex.
193 73 50 80 188.3 40.0 80.0 Comp. Ex. 194 74 200 40 1.5 2.0 5.0
Comp. Ex. 195 75 200 80 1.5 2.0 1.0 Comp. Ex. 196 76 200 40 60.0
20.0 5.0 Ex. 197 77 500 40 39.6 6.0 5.0 Comp. Ex. 198 78 1000 40
7.8 0.8 50.0 Comp. Ex. 199 79 300 40 480.0 160.0 5.0 Ex. 200 80 50
80 188.3 40.0 80.0 Comp. Ex.
TABLE-US-00041 TABLE 21-2 Chemi- Evaluation Results cally Chemical
Worked Black- Treated Treatment Flat Part Part ening Steel Solution
V.sup.5+/ Corrosion Corrosion Resis- Cate- Sheet No. No. V
Resistance Resistance tance gory 187 67 0.85 D D D Comp. Ex. 188 68
0.81 D D D Comp. Ex. 189 69 0.92 B B A Ex. 190 70 0.90 A A A Ex.
191 71 0.68 D D D Comp. Ex. 192 72 0.75 D D D Comp. Ex. 193 73 0.74
D D D Comp. Ex. 194 74 0.81 C D D Comp. Ex. 195 75 0.79 D D D Comp.
Ex. 196 76 0.95 B B A Ex. 197 77 0.84 C D D Comp. Ex. 198 78 0.76 C
D D Comp. Ex. 199 79 0.93 A A A Ex. 200 80 0.78 C D D Comp. Ex.
[0133] As is obvious from Tables 16-1, 16-2 and 20-1, 20-2, in
chemically treated steel sheets Nos. 171 to 177 obtained using,
respectively, chemical treatment solutions Nos. 51 to 57, all of
flat part corrosion resistance, worked part corrosion resistance
and blackening resistance were sufficiently favorable.
[0134] However, as is obvious from Tables 17-1, 17-2 and 20-1,
20-2, in chemically treated steel sheets Nos. 178 to 184 obtained
using, respectively, chemical treatment solutions Nos. 58 to 64
having the same compositions as those of chemical treatment
solutions Nos. 51 to 57 except containing a hydrophilic resin, at
least one of flat part corrosion resistance, worked part corrosion
resistance and blackening resistance were insufficient at times.
Specifically, in chemically treated steel sheets Nos. 180, 182 and
183 using, respectively, chemical treatment solutions Nos. 60, 62
and 63 having a relatively low concentration of a hydrophilic
resin, all of flat part corrosion resistance, worked part corrosion
resistance and blackening resistance were sufficiently favorable.
In contrast, in chemically treated steel sheets Nos. 178, 179, 181
and 184 obtained using, respectively, chemical treatment solutions
Nos. 58, 59, 61 and 64 having a relatively high concentration of a
hydrophilic resin, all of flat part corrosion resistance, worked
part corrosion resistance and blackening resistance were
insufficient. This is considered to be because the content of a
hydrophilic resin at a relatively high concentration in a chemical
treatment solution inhibits the formation of the two-layer
structure in the chemical conversion film.
[0135] Also in chemically treated steel sheets Nos. 185 and 186,
all of flat part corrosion resistance, worked part corrosion
resistance and blackening resistance were insufficient. This is
considered as follows: chemical treatment solutions Nos. 65 and 66
contain a hydrophilic resin at a high concentration regardless of
the presence/absence of phosphorus even though "Mo/V" and "amine/V"
in chemical treatment solutions Nos. 65 and 66 are the same, and
thus the formation of the two-layer structure in the chemical
conversion film is inhibited for the same reason as described
above.
[0136] Further, as is obvious from Tables 18-1, 18-2 and 21-1,
21-2, in chemically treated steel sheets Nos. 187 to 193 obtained
using, respectively, chemical treatment solutions Nos. 67 to 73
having the same compositions as those of chemical treatment
solutions Nos. 51 to 57 except containing fluorine as a fluorine
ion or a fluorometal ion, at least one of flat part corrosion
resistance, worked part corrosion resistance and blackening
resistance were insufficient at times. Specifically, in chemically
treated steel sheets Nos. 189 and 190 using, respectively, chemical
treatment solutions Nos. 69 and 70 having a relatively low
concentration of fluorine, all of flat part corrosion resistance,
worked part corrosion resistance and blackening resistance were
sufficiently favorable. In contrast, in chemically treated steel
sheets Nos. 187, 188, and 191 to 193 obtained using, respectively,
chemical treatment solutions Nos. 67, 68, and 71 to 73 having a
relatively high concentration of fluorine, all of flat part
corrosion resistance, worked part corrosion resistance and
blackening resistance were insufficient. This is considered to be
because the content of the fluorine at a relatively high
concentration in a chemical treatment solution inhibits the
formation of the two-layer structure in the chemical conversion
film.
[0137] Further, as is obvious from Tables 19-1, 19-2 and 21-1,
21-2, in chemically treated steel sheets Nos. 194 to 200 obtained
using, respectively, chemical treatment solutions Nos. 74 to 80
having the same compositions as those of chemical treatment
solutions Nos. 51 to 57 except containing silicon derived from a
silanol group, at least one of flat part corrosion resistance,
worked part corrosion resistance and blackening resistance were
insufficient at times. Specifically, in chemically treated steel
sheets Nos. 196 and 199 using, respectively, chemical treatment
solutions Nos. 76 and 79 having a relatively low concentration of
silicon, all of flat part corrosion resistance, worked part
corrosion resistance and blackening resistance were sufficiently
favorable. In contrast, in chemically treated steel sheets Nos.
194, 195, 197, 198, and 200 obtained using, respectively, chemical
treatment solutions Nos. 74, 75, 77, 78, and 80 having a relatively
high concentration of silicon, all of flat part corrosion
resistance, worked part corrosion resistance and blackening
resistance were insufficient. This is considered to be because the
content of the silicon at a relatively high concentration in a
chemical treatment solution inhibits the formation of the two-layer
structure in the chemical conversion film.
[0138] As described above, it can be found that a chemically
treated steel sheet excellent in worked part corrosion resistance
and blackening resistance can be obtained by applying, to a
zinc-based plated steel sheet having a zinc-based plating layer
containing 0.1 to 22.0 mass % of aluminum, a chemical treatment
solution containing a water-soluble molybdate, a vanadium salt, an
amine, a group 4A metal oxoate and a phosphate compound, in which a
molar ratio of molybdenum to vanadium is 0.4 to 5.5, and a molar
ratio of the amine to the vanadium is 0.3 or more; and the content
of the hydrophilic resin is at most 100 mass %, the fluorine
concentration is at most 30 mass %, or the silicon concentration is
at most 50 mass %, based on the total amount of the vanadium and
the molybdenum, even when the chemical treatment solution is dried
at a low temperature and for a short period of time.
[0139] This application claims the priority of Japanese Patent
Applications No. 2013-235543 filed on Nov. 14, 2013, and Japanese
Patent Applications No. 2014-231275 filed on Nov. 14, 2014, the
entire contents of which including the specification and drawings
are incorporated herein by reference.
INDUSTRIAL APPLICABILITY
[0140] The chemically treated steel sheet of the present invention
is excellent in corrosion resistance and blackening resistance, and
is therefore useful for wide applications such as automobiles,
building materials, and home electric appliances, for example.
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