U.S. patent application number 10/275660 was filed with the patent office on 2003-11-13 for metal surface treatment agent.
Invention is credited to Sako, Ryousuke, Ueno, Keiichi.
Application Number | 20030209293 10/275660 |
Document ID | / |
Family ID | 29424226 |
Filed Date | 2003-11-13 |
United States Patent
Application |
20030209293 |
Kind Code |
A1 |
Sako, Ryousuke ; et
al. |
November 13, 2003 |
Metal surface treatment agent
Abstract
The present invention relates to a metal surface treatment agent
that characteristically contains (A) at least 1 vanadium compound
and (B) at least one metal compound containing at least 1 metal
selected from the group consisting of zirconium, titanium,
molybdenum, tungsten, manganese, and cerium. The present invention
also relates to a metal surface treatment method using the
foregoing treatment agent and the corresponding surface-treated
metals. The present invention provides a metal surface treatment
agent that does not contain chromium and that can be used to impart
an excellent corrosion resistance and alkali resistance to metals.
The present invention provides a metal surface treatment method
that uses the foregoing treatment agent and also provides the
corresponding surface-treated metals.
Inventors: |
Sako, Ryousuke; (Kanagawa
Pref, JP) ; Ueno, Keiichi; (Hiratsuka-shi, Kanagawa
Pref, JP) |
Correspondence
Address: |
HENKEL CORPORATION
2500 RENAISSANCE BLVD
STE 200
GULPH MILLS
PA
19406
US
|
Family ID: |
29424226 |
Appl. No.: |
10/275660 |
Filed: |
April 7, 2003 |
PCT Filed: |
May 11, 2001 |
PCT NO: |
PCT/US01/15468 |
Current U.S.
Class: |
148/273 |
Current CPC
Class: |
C23C 22/34 20130101;
C23C 22/44 20130101; C23C 22/40 20130101 |
Class at
Publication: |
148/273 |
International
Class: |
C23C 022/40 |
Foreign Application Data
Date |
Code |
Application Number |
May 11, 2000 |
JP |
2000-137985 |
May 1, 2001 |
JP |
2001-137985 |
Claims
What is claimed:
1. A metal surface treatment agent comprising: (A) at least 1
vanadium compound; and (B) at least one metal compound containing
at least 1 metal selected from the group consisting of zirconium,
titanium, molybdenum, tungsten, manganese, and cerium.
2. The metal surface treatment agent of claim 1, wherein the ratio
in the vanadium compound (A) of vanadium ions in the pentavalent
oxidation state to the total vanadium V.sup.5+/V is in the range of
0 to 0.6.
3. The metal surface treatment agent of claim 1 or 2, further
comprising (C) an organic compound that contains at least 1
functional group selected from the group consisting of hydroxyl
groups, carbonyl groups, carboxyl groups, primary to tertiary amino
groups, amide groups, phosphoric acid groups, and phosphonic acid
groups, wherein the organic compound (C) is present in an amount of
0.05 to 10 mass parts per 1 mass part pentavalent oxidation state
vanadium in the vanadium compound.
4. The metal surface treatment agent of any of claims 1 to 3,
further comprising (D) at least 1 etchant selected from the group
consisting of inorganic acids, organic acids, and fluorine
compounds, wherein the etchant (D) is present in an amount of 1 to
100 g/l.
5. The metal surface treatment agent of any of claims 1 to 4,
wherein the vanadium compound (A) is present in an amount of 1 to
100 g/l as vanadium and the metal compound (B) is present in an
amount of 1 to 100 g/l as metal.
6. The metal surface treatment agent of any of claims 1 to 5,
wherein the vanadium compound (A)/metal compound (B) mass ratio is
1/9 to 9/1 calculated on the metal.
7. The metal surface treatment agent of any claims 1-6, further
comprising (E) a water-dispersible or water-soluble organic
polymer.
8. A method for treating a metal surface comprising: treating the
metal surface with a metal surface treatment agent according to any
of claims 1 to 7; and drying by heating so the temperature of the
metal reaches 50 to 250.degree. C.
9. A surface-treated metal that bears a coating formed using the
surface treatment method of claim 8.
10. A surface-treated metal that bears a coating formed using the
surface treatment agent of any of claims 1 to 7.
11. A surface-treated metal of claim 10 further comprising an
organic polymer coating, wherein the organic polymer coating
comprises a water-dispersible or water-soluble organic polymer
having a glass transition temperature of 0 to 120.degree. C.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a metal surface treatment agent
and method that can be used to form a chromium-free coating on the
surface of metal sheet coil and metal formed articles and that
impart to such surfaces an excellent corrosion resistance and
excellent alkali resistance. The invention also relates to the
corresponding surface-treated metals.
[0003] More particularly, this invention relates to a metal surface
treatment agent and method that can be used to form a chromium-free
coating that imparts an excellent corrosion resistance and
excellent alkali resistance to formed articles, castings, and sheet
coil (for example, automotive body elements and other automotive
parts, construction materials, parts for household electrical
appliances) of zinciferous-plated steel sheet, steel sheet, or
aluminiferous metal. The invention additionally relates to the
corresponding surface-treated metals.
[0004] 2. Background Art
[0005] Metals such as zinciferous-plated steel sheet, steel sheet,
and aluminiferous metals are susceptible to oxidation and corrosion
by atmospheric oxygen, moisture, and the ions present in moisture.
One known method for inhibiting this corrosion comprises forming a
chromate coating on the metal surface by bringing the metal into
contact with a chromium-containing treatment bath, for example, a
chromic acid chromate or phosphoric acid chromate bath.
[0006] While the coatings generated by these chromate treatments do
tend to exhibit excellent corrosion resistance and excellent paint
adherence, the treatment baths used in these treatments typically
contain toxic hexavalent chromium, which can impose substantial
time, labor, and cost burdens on wastewater treatment. Moreover,
hexavalent chromium is also present in the coatings produced by
these treatments, which has led based on environmental and safety
considerations to an ever increasing tendency to avoid the use of
these coatings.
[0007] Methods that employ non-chromate (chromium-free) treatments
baths are known. For example, Japanese Laid Open (Kokai or
Unexamined) Patent Application Number Hei 7-278410 (278,410/1995)
teaches a polymer composition and a method for treating metal
surfaces wherein the polymer composition contains an acidic
compound and a phenolic resin-type polymer with a specific
structure. An agent and method for treating metal surfaces are also
disclosed in Japanese Laid Open (Kokai or Unexamined) Patent
Application Number Hei 8-73775 (73,775/1996). This agent and method
provide an excellent fingerprint resistance. The agent contains at
least 2 silane coupling agents having reactive functional groups
with specific structures; these reactive functional groups are
different from each other but are capable of reacting with one
other. Japanese Laid Open (Kokai or Unexamined) Patent Application
Number Hei 9-241576 (241,576/1997) discloses a method and agent for
treating metal surfaces wherein the agent contains a silane
coupling agent with a specific structure and a phenolic resin-type
polymer with a specific structure. Japanese Laid Open (Kokai or
Unexamined) Patent Application Number Hei 10-1789 (1,789/1998)
teaches an agent and method for treating metal surfaces and metal
surfaces thereby treated. This agent contains a specific polyvalent
anion and an organic polymer, such as an epoxy resin, acrylic
resin, or urethane resin, that contains at least 1 nitrogen atom.
Japanese Laid Open (Kokai or Unexamined) Patent Application Number
Hei 10-60233 (60,233/1998) teaches a treatment method that uses two
rust preventives (1) and (2) and metals thereby treated. Rust
preventive (1) contains a bisphenol A epoxy resin with a specific
structure, while rust preventive (2) contains phenolic resin and a
specific non-phenolic resin (e.g., polyester) in quantities that
provide a solids ratio of 4:1 to 1:4 upon mixing.
[0008] None of the metal surface treatments taught in these laid
open patent applications uses chromium, and, while they do offer
the advantage of a treatment bath free of hexavalent chromium, in
each case they produce coatings that exhibit a corrosion resistance
inferior to the corrosion resistance from chromate treatment. The
coatings produced by these chromium-free treatments also suffer
from an unacceptable fingerprint resistance and lubricity.
[0009] Japanese Laid Open (Kokai or Unexamined) Patent Application
Number Hei 10-1789 teaches vanadic acid among the therein specified
polyvalent anions. However, vanadic acid, which is an oxyacid of
pentavalent vanadium, has a poor resistance to water and alkali. As
a result, when the treated metal is rinsed, and particularly when
it is rinsed with alkali, the vanadic acid is eluted from the
coating, which results in a major reduction in corrosion
resistance. This laid open patent application also teaches the
post-treatment execution of a water rinse and drying. Thus, while
the problem of a chromium-containing wastewater is not present, the
organics create the problem of a COD-containing wastewater.
[0010] Inventions that use vanadium compounds as rust preventives
are also known. Japanese Laid Open (Kokai or Unexamined) Patent
Application Number Hei 1-9229 (9,229/1990) teaches an antirust
paint that contains a film-forming resin, a phosphate ion source
that releases phosphate ion in an ambient containing water and
oxygen, and a vanadate ion source that releases vanadate ion in an
ambient containing water and oxygen. Japanese Granted Patent
2,795,710 teaches an antirust composition in which specific
compounds are blended in specific proportions; the specific
compounds include (A) a vanadate ion source that releases vanadate
ion in specific concentrations in a water-based dispersion and (B)
an organophosphonic acid capable of dissolution in specific
concentrations in a water-based dispersion. The vanadate ion source
is added to function as the antirusting pigment of these antirust
paints, and when baked at high temperatures (600.degree. C. and
above) is converted to a pigment with an average particle size of
several .mu.m. The particles of this pigment do manifest an
anticorrosion activity when present in paint films having a certain
film thickness (several times the particle size of the pigment),
but exhibit no anticorrosion activity at all in the thin films (no
greater than several .mu.m) encountered in the field of metal
treatment. Another problem with these treatment agents is that
settling occurs due to aggregation of the particles therein when
the treatment agent is allowed to stand.
[0011] Thus, no extant non-chromate metal surface treatment agent
has the ability to form a coating that can simultaneously impart an
excellent corrosion resistance, an excellent alkali resistance, and
an excellent fingerprint resistance to metal surfaces.
SUMMARY OF THE INVENTION
[0012] The present invention remedies the herein above described
problems associated with the prior art. An object of the present
invention is to provide a metal surface treatment agent that does
not contain chromium and that can impart an excellent corrosion
resistance and excellent alkali resistance to metals. Additional
objects of the present invention are to provide a metal surface
treatment method that uses this agent and metals whose surface has
been treated using the inventive agent and method.
[0013] The present inventors have discovered that highly
corrosion-resistant, highly alkali-resistant coatings can be
obtained by treating metal surfaces with a surface treatment agent
whose essential components are a vanadium compound and a particular
type of metal compound. This invention was achieved based on this
discovery.
[0014] In specific terms, this invention relates to a metal surface
treatment agent that characteristically contains: (A) at least 1
vanadium compound and (B) a metal compound or compounds containing
at least 1 metal selected from the group consisting of zirconium,
titanium, molybdenum, tungsten, manganese, and cerium.
[0015] In an embodiment preferred in order to obtain a better
stability by the vanadium compound in the treatment agent and an
improved corrosion resistance and alkali resistance by the produced
film, the ratio in vanadium compound (A) of vanadium ion in the
trivalent and tetravalent oxidation states to the total vanadium
(V.sup.3++V.sup.4+)/V is in the range of 0.1 to 1.0.
[0016] In another preferred embodiment, the inventive metal surface
treatment agent additionally contains (C) an organic compound that
contains at least 1 functional group selected from the group
consisting of hydroxyl groups, carbonyl groups, carboxyl groups,
primary to tertiary amino groups, amide groups, phosphoric acid
groups, and phosphonic acid groups. The purpose of this embodiment
is to reduce the pentavalent vanadium compound, when used, to the
tetravalent or trivalent oxidation state and/or to improve the
stability of the vanadium compound in the inventive treatment
bath.
[0017] In another embodiment preferred in order to improve the
adherence of the obtained coating, the inventive metal surface
treatment agent additionally contains (D) at least 1 etchant
selected from the group consisting of inorganic acids, organic
acids, and fluorine compounds.
[0018] The invention additionally relates to a method for treating
metal surfaces comprising treating a metal surface with any of the
inventive metal surface treatment agents described above, and
drying by heating so the temperature of the metal reaches 50 to
250.degree. C.
[0019] The invention further relates to surface-treated metals that
bear a coating produced using the aforementioned inventive surface
treatment method.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0020] The vanadium compound present in the metal surface treatment
agent of the present invention comprises at least 1 selection from
vanadium compounds in which the vanadium has a pentavalent,
tetravalent, or trivalent oxidation state. Examples of suitable
vanadium compounds include, but are not necessarily limited to,
pentavalent vanadium compounds such as vanadium pentoxide
(V.sub.2O.sub.5), metavanadic acid (HVO.sub.3), ammonium
metavanadate, sodium metavanadate, and vanadium oxytrichloride
(VOCl.sub.3), and trivalent and tetravalent vanadium compounds such
as vanadium trioxide (V.sub.2O.sub.3), vanadium dioxide (VO.sub.2),
vanadium oxysulfate (VOSO.sub.4), vanadium oxyacetylacetonate
(VO(OC(CH.sub.3).dbd.CHCOCH.sub.3).sub.2), vanadium acetylacetonate
(V(OC(CH.sub.3).dbd.CHCOCH.sub.3).sub.3), vanadium trichloride
(VCl.sub.3), and phosphovanadomolybdic acid
{H.sub.15--X(PV.sub.12--xMoxO-
.sub.40).multidot.nH.sub.2O(6<.times.<12, n<30)}.
[0021] Preferably, the treatment agent of the present invention
contains a trivalent or tetravalent vanadium compound as the
vanadium compound (A). More preferably, the ratio of vanadium ions
in the trivalent and tetravalent oxidation states to the total
vanadium (V.sup.3++V.sup.4+)/V (V.sup.3+ refers to the mass of the
vanadium in the trivalent oxidation state, V.sup.4+ refers to the
mass of the vanadium in the tetravalent oxidation state, and V
refers to the total mass of the vanadium) is in the range of 0.1 to
1.0, even more preferably in the range of 0.2 to 1.0, and most
preferably in the range of 0.4 to 1.0. When this ratio is below
0.1, the stability of the vanadium in the treatment agent can be
poor and the ultimately formed coating may have reduced corrosion
resistance and alkali resistance.
[0022] Preferably, the ratio of vanadium ions in the pentavalent
oxidation state (V.sup.5+) to the total vanadium is in the range of
0 to 0.9, even more preferably in the range of 0 to 0.8, and most
preferably in the range of 0 to 0.6.
[0023] One process for introducing a trivalent or tetravalent
vanadium compound into the treatment agent of the present invention
comprises using at least one of the trivalent or tetravalent
vanadium compounds described above. Another suitable process
comprises effecting a preliminary reduction of a pentavalent
vanadium compound to a trivalent or tetravalent vanadium compound
using a reducing agent. The reducing agent used for this purpose
may be inorganic or organic but preferably is organic. The use of
the above-described compound (C) is particularly preferred.
[0024] The component (B) present in the inventive metal surface
treatment agent of the present invention comprises a metal compound
or compounds containing at least 1 metal selected from the group
consisting of zirconium, titanium, molybdenum, tungsten, manganese,
and cerium. Component (B) can preferably be an oxide or hydroxide
of the specified metals, a complex of these metals, or the salt of
an inorganic or organic acid. Suitable examples of metal compound
(B) include, but are not necessarily limited to, zirconyl nitrate
ZrO(NO.sub.3).sub.2, zirconyl acetate, zirconyl sulfate, ammonium
zirconyl carbonate (NH.sub.4).sub.2(Zr(CO.sub.3).sub.2(OH).sub.2),
dizirconium acetate, titanyl sulfate TiOSO.sub.4, titanium lactate,
diisopropoxytitanium bisacetylacetone
(C.sub.5H.sub.7O.sub.2).sub.2Ti(OCH(CH.sub.3).sub.2).sub- .2, the
reaction product of lactic acid and titanium alkoxide, molybdic
acid H.sub.2MoO.sub.4, ammonium molybdate, sodium molybdate,
molybdic acid compounds such as ammonium molybdophosphate
(NH.sub.4).sub.3(PO.sub.- 4Mo.sub.12O.sub.36).multidot.3H.sub.2O
and sodium molybdophosphate
Na.sub.3(PO.sub.4.multidot.12MoO.sub.3).multidot.nH.sub.2O,
metatungstic acid H.sub.6(H.sub.2W.sub.12O.sub.40), ammonium
metatungstate (NH.sub.4).sub.6(H.sub.2W.sub.12O.sub.40), sodium
metatungstate, paratungstic acid
H.sub.10(W.sub.12O.sub.46H.sub.10), ammonium paratungstate, sodium
paratungstate, permanganic acid HMnO.sub.4, potassium permanganate,
sodium permanganate, manganese dihydrogen phosphate
Mn(H.sub.2PO.sub.4).sub.2, manganese nitrate Mn(NO.sub.3).sub.2,
manganese sulfate, manganese fluoride, manganese carbonate
MnCO.sub.3, manganese acetate, cerium acetate
Ce(CH.sub.3CO.sub.2).sub.3, cerium nitrate, and cerium
chloride.
[0025] The organic compound (C) present on an optional basis in the
metal surface treatment agent of the present invention comprises an
organic compound that contains at least 1 functional group selected
from the group consisting of hydroxyl groups, carbonyl groups,
carboxyl groups, primary to tertiary amino groups, amide groups,
phosphoric acid groups, and phosphonic acid groups.
[0026] Suitable examples of organic compound (C) include, but are
not necessarily limited to, alcohols such as methanol, ethanol,
isopropanol, and ethylene glycol; carbonyl compounds such as
formaldehyde, acetaldehyde, furfural, acetylacetone, ethyl
acetoacetate, dipivaloylmethane, and 3-methylpentanedione; organic
acids such as formic acid, acetic acid, propionic acid, tartaric
acid, ascorbic acid, gluconic acid, citric acid, and malic acid;
amine compounds such as triethylamine, triethanolamine,
ethylenediamine, pyridine, imidazole, pyrrole, morpholine, and
piperazine; acid amide compounds such as formamide, acetamide,
propionamide, and N-methylpropionamide; amino acids such as
glycine, alanine, proline, and glutamic acid; organophosphoric
acids such as aminotri(methylenephosphonic acid),
1-hydroxyethylidene-1,1'-diphospho- nic acid,
ethylenediaminetetra(methylenephosphonic acid), and phytic acid;
monosaccharides such as glucose, mannose, and galactose;
oligosaccharides such as maltose and sucrose; natural
polysaccharides such as starch and cellulose; aromatic compounds
such as tannic acid, humic acid, ligninsulfonic acid, and
polyphenols; and synthetic polymers such as polyvinyl alcohol,
polyethylene glycol, polyacrylic acid, polyacrylamide,
polyethyleneimine, and water-soluble nylon.
[0027] The use of the organic compound (C) is preferred for the
purposes of reducing pentavalent vanadium compound, when used, to
the tetravalent or trivalent vanadium compound and/or improving the
stability of the vanadium compound in the treatment bath of the
present invention.
[0028] The organic compound (C) can be preliminarily mixed with the
vanadium compound with heating (for example, at 40 to 100.degree.
C. for 5 to 120 minutes) to give a mixture in which the reduction
and stabilization reactions have been thoroughly developed and the
resulting mixture can then be blended into the surface treatment
agent. Alternatively, the surface treatment agent in the form of a
simple mixture can be coated on the metal surface and reduction can
be developed during the ensuing thermal drying step.
[0029] The etchant (D) present on an optional basis in the metal
surface treatment agent of the present invention comprises at least
1 compound selected from inorganic acids, organic acids, and
fluorine compounds.
[0030] The optional etchant (D) is used to etch the basis metal
during application of the treatment agent or during the thermal
drying step. Suitable examples of etchant (D) include, but are not
necessarily limited to, inorganic acids such as phosphoric acid,
nitric acid, and sulfuric acid; organic acids such as formic acid
and acetic acid; and fluorine compounds such as hydrofluoric acid,
fluoboric acid HBF.sub.4, fluosilicic acid H.sub.2SiF.sub.6,
fluozirconic acid H.sub.2ZrF.sub.6, fluotitanic acid
H.sub.2TiF.sub.6, stannous fluoride SnF.sub.2, stannic fluoride
SnF.sub.4, ferrous fluoride, and ferric fluoride. Use of the
etchant (D) is preferred for the purpose of improving the adherence
of the ultimately obtained coating.
[0031] The content of the constituent component in the treatment
agent of the present invention is preferably as follows: for the
vanadium compound (A), preferably 1 to 100 g/L as vanadium and more
preferably 2 to 70 g/L as vanadium; for the metal compound (B),
preferably 1 to 100 g/L as the metal and more preferably 2 to 70
g/L as the metal. The vanadium compound (A)/metal compound (B) mass
ratio is preferably 1/9 to 9/1 calculated on the metal and is more
preferably 2/8 to 8/2 calculated on the metal.
[0032] The organic compound (C) is preferably added at from 0.05 to
10 mass parts and more preferably at from 0.1 to 5 mass parts, in
each case per 1 mass part pentavalent oxidation state vanadium in
the vanadium compound. An addition in excess of that required for
reduction is preferred in order to stabilize the reduced material
in the treatment bath.
[0033] The etchant (D) is present preferably at 1 to 100 g/L and
more preferably at 2 to 70 g/L.
[0034] The treatment agent of the present invention may also
contain, to help improve the adherence and corrosion resistance of
the coating, a metal sol such as a water-dispersible silica sol
and/or alumina sol or zirconia sol; a silane coupling agent such as
an aminosilane, epoxysilane, or mercaptosilane; and/or a
water-soluble or water-dispersible resin such as polyacrylic acid,
polyacrylamide, or polyvinyl alcohol. When such a component is
added, it is preferably added at from 5 to 40 mass % of the total
nonvolatile component and more preferably at from 10 to 30 mass %
of the total nonvolatile component.
[0035] For the purposes of this invention, the total nonvolatile
component is the component remaining after the surface treatment
agent has been dried by heating for 2 hours at 110.degree. C.
[0036] The solvent used in the surface treatment agent of the
present invention preferably comprises mainly water, but may on an
optional basis also contain a water-soluble organic solvent, e.g.,
an alcohol, ketone, or glycol ether, in order to help improve the
drying characteristics of the coating.
[0037] The surface treatment agent of the present invention may
also contain, within a range that does not impair the essential
features of the present invention or the properties of the coating
of the present invention, additives such as surfactant, defoamer,
leveling agent, germicide/bactericide, and colorant.
[0038] The surface treatment method of the present invention will
now be disscussed.
[0039] The nature of the pretreatment for the surface treatment of
the present invention is not particularly critical. As a general
matter, surface treatment in accordance with the present invention
will be preceded by cleaning with an alkaline or acidic degreaser,
or hot water, or solvent, in order to remove any oils and
contaminants present on the substrate. This can be followed on an
optional basis by surface conditioning with acid or alkali. In a
preferred embodiment, cleaning of the substrate surface is followed
by rinsing with water so as to remove as much cleaning agent as
possible from the substrate surface.
[0040] The treatment method of the present invention comprises
application of the inventive surface treatment agent to the metal
surface followed by drying by heating to 50 to 250.degree. C.;
however, the techniques used for application and drying are not
particularly critical.
[0041] The following application techniques will typically be used:
roll coating, in which the treatment agent is applied to the
substrate surface by transfer from a roll; broadcasting of the
treatment agent over the substrate surface using, for example, a
shower ring, followed by roll squeegee; dipping the substrate in a
treatment bath; or spraying the treatment agent on the substrate.
While the temperature of the treatment bath again is not
specifically restricted, the treatment temperature is preferably
from 0 to 60.degree. C. and is more preferably from 5 to 40.degree.
C. given that the solvent for the treatment agent of the present
invention comprises mainly water.
[0042] The drying process does not necessarily require heating, and
physical removal, for example, by air drying or air blowing, can be
pursued. However, drying by the application of heat is preferred in
order to improve the film-forming performance and increase the
adherence. The temperature in such cases is preferably 50 to
250.degree. C. and more preferably 60 to 220.degree. C.
[0043] Coating deposition is preferably from 0.005 to 1.5 .mu.m as
the dry film thickness and more preferably from 0.01 to 1.0 .mu.m
as the dry film thickness. Acceptable corrosion resistance and
overcoat adherence are not obtained at less than 0.005 .mu.m, while
deposition in excess of 1.5 .mu.m runs the risk of producing cracks
in the coating and a decline in adherence by the coating
itself.
[0044] The formation of an organic polymer coating in a dry film
thickness of 0.3 to 3.0 .mu.m on the coating formed from the
surface treatment agent of the present invention, in addition to
boosting the corrosion resistance and alkali resistance of the
metal workpiece, can impart thereto fingerprint resistance, solvent
resistance, and surface lubricity.
[0045] A preferred method for establishing this organic polymer
coating comprises application of an overcoating agent (Z) whose
main component is water-soluble or water-dispersible organic
polymer, followed by drying by heating at an attained substrate
temperature of 50 to 250.degree. C. The water-soluble or
water-dispersible organic polymer used in the overcoating agent (Z)
can be, for example, polymer as afforded by the polymerization of
addition-polymerizable unsaturated monomer, such as acrylic resins
and polyolefin resins, as well as polymer as afforded by a
condensation reaction, such as epoxy resins, urethane resins,
polyester resins, polyamide resins, and phenolic resins. The
glass-transition temperature of the subject organic polymer is
preferably from 0 to 120.degree. C. and more preferably is from 10
to 100.degree. C. A glass-transition temperature below 0.degree. C.
may result in a coating with poor strength and hardness, while a
glass-transition temperature in excess of 120.degree. C. may result
in poor film-formability and poor adherence.
[0046] In addition to containing at least 1 selection from the
foregoing organic polymers, the overcoating agent may preferably
contain water-dispersible silica in order to improve the toughness
and fingerprint resistance of the coating. The addition of a
water-borne wax may also be preferred in order to improve the
lubricity. The preferred contents of the foregoing components are
as follows: for the organic polymer, 50 to 100 mass parts
nonvolatile component per 100 mass parts total nonvolatiles in the
overcoating agent; for the water-dispersible silica, 0 to 40 mass
parts nonvolatile component per 100 mass parts total nonvolatiles
in the overcoating agent; and for the water-borne wax, 0 to 30 mass
parts nonvolatile component per 100 mass parts total nonvolatiles
in the ovecoating agent. A crosslinker capable of crosslinking the
organic polymer may also be present.
[0047] In one embodiment of the invention, one or more
water-soluble or water-dispersible organic polymers of the type
described herein above may be incorporated directly into the metal
surface treatment agent as an additional component (E).
[0048] When coated on a metal substrate and dried thereon by
heating, the surface treatment agent of the present invention
reacts with the surface of the metal substrate and forms a fine,
dense, and passive coating.
[0049] The manifestation of excellent corrosion resistance by the
coating produced by the surface treatment agent of the present
invention, without wishing to be bound to any particular theory, is
believed to be due to a delocalization of the corrosion electrons
(potential leveling) and a barrier effect by the coating that
checks the permeation of oxygen, moisture, and ions. With respect
to the vanadium compound (A) of the present invention, it is
believed that a pentavalent vanadium compound occurs with the
generation of an oxygen-bonded polyvalent anion and is unable to
generate an entirely acceptable performance due to its poor water
resistance and alkali resistance. However, a coating having
improved water resistance and alkali resistance can be formed using
a treatment agent of the present invention that contains reduced
tetravalent and/or trivalent vanadium compounds. The organic
compound (C) is believed both to reduce the pentavalent vanadium
compound and at the same time to chelate and stabilize the
trivalent and/or tetravalent vanadium afforded by reduction in and
present in the aqueous solution.
[0050] The use of an organic polymer-based overcoating on the
inventive film can provide an additional and substantial boost in
corrosion resistance due to a synergetic interaction with the
barrier activity of the overcoating.
EXAMPLES
[0051] The present invention is explained in greater detail
hereinbelow by working and comparative examples. The working
examples that follow are intended only as individual examples and
should not be construed as limiting the present invention. The
procedures used to evaluate the treated sheet samples prepared in
the working and comparative examples are also explained below.
[0052] 1. Substrates
[0053] A: electrogalvanized steel sheet (sheet thickness=0.8
mm)
[0054] B: hot-dip galvanized steel sheet (sheet thickness=0.8
mm)
[0055] C: 55% Al/Zn-plated steel sheet (sheet thickness=0.5 mm)
[0056] 2. Inventive treatment baths
[0057] (1) Treatment bath components
[0058] The vanadium compounds (A) used in the treatment baths were
as follows.
[0059] A1: ammonium metavanadate
[0060] A2: vanadium pentoxide
[0061] A3: vanadium trioxide
[0062] A4: vanadium oxyacetylacetonate
[0063] The metal compounds (B) used in the treatment baths were as
follows.
[0064] B1: ammonium molybdate
[0065] B2: ammonium metatungstate
[0066] B3: ammonium zirconium carbonate
[0067] B4: fluotitanic acid
[0068] B5: manganese carbonate
[0069] The organic compounds (C) used in the treatment baths were
as follows.
[0070] C1: L-ascorbic acid
[0071] C2: D-glucose
[0072] C3: glyoxal
[0073] The etchants (D) used in the treatment baths were as
follows.
[0074] D1: HF
[0075] D2: H.sub.2ZrF.sub.6
[0076] D3: CH.sub.3COOH
[0077] D4: H.sub.2SiF.sub.6
[0078] (2) Preparation of the treatment baths
[0079] Examples 1 through 7: The vanadium compound (A), metal
compound (B), etchant (D), and deionized water were mixed and
heated at 50.degree. C. for 1 hour.
[0080] Examples 8 through 11: The vanadium compound (A) was first
mixed into the 5% aqueous solution of the organic compound (C)
followed by heating for 30 minutes at 80 to 100.degree. C. After
subsequently cooling to room temperature, the metal compound (B)
and then the etchant (D) were added. The bath was finally brought
to its prescribed concentration by the addition of deionized
water.
[0081] 3. Overcoating baths
[0082] The overcoating agents (Z) and treatment methods therewith
are described below.
[0083] Z1: a water-borne treatment bath containing 10% nonvolatile
fraction comprising 100 mass parts as solids of a water-borne
polyurethane (SUPERFLEX 100 from Dai-ichi Kogyo Seiyaku Co., Ltd.),
20 mass parts as silica of a water-borne silica (SNOWTEX C from
Nissan Chemical Industries, Ltd.), and 10 mass parts as solids of a
water-borne wax (CHEMIPEARL W900 from Mitsui Chemicals, Inc.).
[0084] Z2: a water-borne treatment bath containing 20% nonvolatile
fraction comprising 10 mass parts as silica of a water-dispersible
silica and 100 mass parts as solids of an ammonia-neutralized
water-borne polymer (ethylene-acrylic acid copolymer with
ethylene/acrylic acid=80/20 and average molecular
weight=approximately 20,000).
[0085] 4. Treatment sequence
[0086] (1) Degreasing
[0087] The substrate was degreased with an alkaline degreaser
(PALKLIN 364S from Nihon Parkerizing Co., Ltd., 20 g/L bath,
60.degree. C., 10-second spray, spray pressure=50 kPa) and was then
rinsed with water by spraying for 10 seconds.
[0088] (2) Coating with the treatment bath of the present invention
and drying
[0089] I: the treatment bath was applied with a #3 bar coater
followed by drying at a sheet temperature of 80.degree. C. using a
convection oven.
[0090] II the treatment bath was applied with a #3 bar coater
followed by drying at a sheet temperature of 120.degree. C. using a
convection oven.
[0091] (3) Coating with the overcoating treatment bath and
drying
[0092] An overcoating bath as described above was bar-coated to a
dry-film thickness of about 1 .mu.m on the coating already formed
using the treatment bath and method of the present invention. This
was followed by drying by heating at a sheet temperature of
100.degree. C.
[0093] 5. Evaluation procedures
[0094] (1) Corrosion resistance
[0095] The corrosion resistance was determined by salt-spray
testing based on JIS Z-2371. After salt-spray exposure for 72 hours
or 120 hours, the area of white rust production was scored on the
following scale.
[0096] Evaluation scale:
[0097] area of white rust development
[0098] ++: less than 10%
[0099] +: less than 30% but at least 10%
[0100] .DELTA.: less than 60% but at least 30%
[0101] x: at least 60%
[0102] (2) Alkali resistance
[0103] A bath was prepared containing 20 g/L of the alkaline
degreaser PALKLIN 364S from Nihon Parkerizing Co., Ltd. The
resulting aqueous degreaser solution was adjusted to 60.degree. C.
and then sprayed for 30 seconds on the already treated sheet. This
was followed by rinsing with water and drying at 80.degree. C. The
sheet was subsequently evaluated for corrosion resistance using the
conditions and methodology described in (1) above.
[0104] (3) Fingerprint resistance
[0105] A finger was pressed onto the surface of the treated sheet
followed by evaluation by visual inspection of the status of the
residual fingerprint trace.
[0106] Evaluation scale:
[0107] ++: residual fingerprint trace entirely absent
[0108] +: very faint residual fingerprint trace
[0109] .DELTA.: residual fingerprint trace present
[0110] x: distinct residual fingerprint trace present
[0111] (4) Solvent resistance
[0112] An ethanol-soaked gauze was wrapped around a silicone rubber
cube (1 cm) and this was rubbed back-and-forth 10 times on the test
surface under 50,000 kPa.
[0113] Evaluation scale:
[0114] ++: coating exfoliation almost entirely absent
[0115] +: slight exfoliation of the coating occurred
[0116] .DELTA.: moderate exfoliation of the coating occurred
[0117] x: the coating was entirely exfoliated with exposure of the
substrate
[0118] The treatment bath compositions and treatment methods used
in the working and comparative examples are reported in Tables 1
and 2, while the evaluation results for the treated sheets are
reported in Tables 3 and 4. The results reported in Table 3 confirm
an excellent corrosion resistance and alkali resistance for
coatings produced from inventive treatment agents (Examples 1
through 11) containing the herein specified vanadium compound (A)
and metal compound (B). In contrast, a poor corrosion resistance
and poor alkali resistance were obtained in Comparative Examples 1
through 3, which either did not contain the vanadium compound (A)
or did not contain the metal compound (B).
[0119] Examples 12 through 22 concerned the additional execution of
a resin overcoating (Z1 or Z2) on the films produced in Examples 1
through 11. Examples 12 through 22 all gave an excellent corrosion
resistance and alkali resistance as well as an excellent
fingerprint resistance and solvent resistance. In contrast to this,
a poor corrosion resistance and poor alkali resistance were
obtained in Comparative Examples 4 through 6, which either did not
contain the vanadium compound (A) or did not contain the metal
compound (B).
1TABLE 1 working and treatment bath composition in g/L comparative
vanadium (V.sup.3+ + V.sup.4+)/ metal compound etchant treatment
examples substrate (A)* total V (B)* (D) method Example 1 A A1 (7)
0.72 B1 (5) -- I A3 (18) B4 (10) Example 2 A A1 (7) 0.72 B1 (5) D2
(2) I A3 (18) B4 (10) Example 3 A A4 (3) 1.0 B4 (2) D2 (2) I
Example 4 B A2 (7.2) 0.28 B3 (10) D1 (10) II A3 (2.8) A1 (3) 0.5 B2
(2) D2 (10) II Example 5 B A3 (1) B5 (5) A4 (2) Example 6 C A3 (5)
1.0 B4 (10) D4 (1) I A4 (10) Example 7 A A1 (7) 0 B1 (5) D1 (2) I
B4 (10) Comparative A -- -- B1 (5) D1 (2) I Example 1 B4 (10)
Comparative B A2 (7.2) 0.28 -- -- II Example 2 A3 (2.8) *as the
metal
[0120]
2TABLE 2 working and treatment bath composition in g/L comparative
vanadium metal compound organic compound etchant treatment examples
substrate (A)* (B)* (C) (D) method Example 8 A A1 (12) B1 (5) C1
(5) D1 (2) I B4 (5) Example 9 B A (7.5) B2 (5) C2 (7.5) D3 (5) II
Example 10 A A1 (15) B3 (15) C3 (15) D2 (5) II Example 11 C A1 (10)
B4 (6) C1 (1) D4 (10) I A2 (20) B5 (4) Comparative A At (12) -- C1
(5) D1 (2) I Example 3 *as the metal
[0121] Example 12: Treatment with overcoating agent Z1 was carried
out on film formed in accordance with Example 1.
[0122] Example 13: Treatment with overcoating agent Z1 was carried
out on film formed in accordance with Example 2.
[0123] Example 14: Treatment with overcoating agent Z1 was carried
out on film formed in accordance with Example 3.
[0124] Example 15: Treatment with overcoating agent Z2 was carried
out on film formed in accordance with Example 4.
[0125] Example 16: Treatment with overcoating agent Z1 was carried
out on film formed in accordance with Example 5.
[0126] Example 17: Treatment with overcoating agent Z2 was carried
out on film formed in accordance with Example 6.
[0127] Example 18: Treatment with overcoating agent Z1 was carried
out on film formed in accordance with Example 7.
[0128] Example 19: Treatment with overcoating agent Z2 was carried
out on film formed in accordance with Example 8.
[0129] Example 20: Treatment with overcoating agent Z1 was carried
out on film formed in accordance with Example 9.
[0130] Example 21: Treatment with overcoating agent Z2 was carried
out on film formed in accordance with Example 10.
[0131] Example 22: Treatment with overcoating agent Z2 was carried
out on film formed in accordance with Example 11.
[0132] Comparative Example 4: Treatment with overcoating agent Z1
was carried out on film formed in accordance with Comparative
Example 1.
[0133] Comparative Example 5: Treatment with overcoating agent Z1
was carried out on film formed in accordance with Comparative
Example 2.
[0134] Comparative Example 6: Treatment with overcoating agent Z2
was carried out on film formed in accordance with Comparative
Example 3.
3TABLE 3 working and comparative corrosion resistance alkali
resistance examples after SST for 48 hours after SST for 48 hours
Example 1 + + Example 2 ++ ++ Example 3 + + Example 4 ++ + Example
5 ++ ++ Example 6 ++ ++ Example 7 + .DELTA. Example 8 ++ ++ Example
9 ++ ++ Example 10 ++ ++ Example 11 ++ ++ Comparative Example 1
.DELTA. x Comparative Example 2 .DELTA. x Comparative Example 3
.DELTA. x
[0135]
4TABLE 4 alkali corrosion resistance working and resistance after
SST comparative after SST for 120 for 120 fingerprint solvent
examples hours hours resistance resistance Example 12 +/++ +/++ + +
Example 13 ++ ++ ++ ++ Example 14 ++ + + ++ Example 15 ++ ++ ++ ++
Example 16 ++ ++ ++ ++ Example 17 ++ ++ ++ ++ Example 18 +
+/.DELTA. ++ ++ Example 19 ++ ++ ++ ++ Example 20 ++ ++ ++ ++
Example 21 ++ ++ ++ ++ Example 22 ++ ++ ++ ++ Comparative .DELTA. x
+ .DELTA. Example 4 Comparative .DELTA. x + .DELTA. Example 5
Comparative .DELTA. x + .DELTA. Example 6
Advantageous Effects of the Invention
[0136] The treatment agent of the present invention is a
non-chromate treatment agent that is free of toxic chromium
compounds. The film or coating formed from the inventive surface
treatment agent exhibits a corrosion resistance that is as good as
or better than the corrosion resistance of prior-art chromate
coatings. As a consequence of these features, the inventive surface
treatment agent, surface treatment method, and surface-treated
metals will have a very high commercial and industrial utilization
value.
[0137] While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
Moreover, the terms "a" and "an", as used herein, mean one of more
unless clearly indicated to the contrary, and the term "as the
metal" means calculated based on the amount of the metal in a
compound.
* * * * *