Note: Descriptions are shown in the official language in which they were submitted.
CA 02470445 2004-06-08
1
DESCRIPTION
METHOD OF SURFACE TREATING METAL AND METAL SURFACE TREATED
THEREBY
FIELD OF THE INVENTION
The present invention relates to a method of metal
surface treatment and surface treated metal thereby.
BACKGROUND TECHNOLOGY
Generally, the surface of a metal is provided with
surface treatmentfor thepurposeofenhancing characteristics
such as corrosion resistance and the like. As one species
of such the surface treatment, there is known surface treatment
with a chemical conversion treatment agent containing a
zirconium compound. Such a method of surface treatment is
performed by an electroless reaction, and an insoluble
zirconium salt and a salt of the component: metal of the article
to be treated,consisting ofhydroxides/fluoridesofzirconium
and fluorides of metal of an article to be treated, are deposited
on the metal surface bymeans of a reaction in which the component
metal of the article to be treated is eluted by the treatment
solution, the production of fluorides based on a reaction of
the eluted metal ions with fluorine ions, the formation of
hydrogen through the reduction of hydrogen ions and the
increase in a pH in the vicinity of the surface of an article
to be treated resulting from the substitution of a fluorine
ion for a hydroxide ion associated with the hydrolysis of
zirconium complex ions.
In such an electroless reaction using a zirconium-based
chemical conversion treatment agent, s_Lnce it is extremely
difficult to cause a homogeneous reaction to occur over the
entire said surface, it is difficult to form an adequately
dense and uniform coat and the resulting coat becomes one
containing a high proportion of oxides and fluorides due to
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etching of substrates, and therefore the corrosion resistance
is deteriorated. And, in the electroless reaction, since an
anodic reaction and a cathodic reaction are simultaneously
occurred on the same surface, reactivity is reduced when the
chemical conversion Boat is being formed. Therefore, only
a rough and thin chemical conversion coat composed of a
substrate metal or an alkali metal can be attained and it is
difficult to attain a uniform and dense protection coat.
consequently, it was difficult that a chemical
conversion coat obtained by using the electroless treatment
with a zirconium-based chemical conversion treatment agent
provide a sufficient rust prevention property particularly
for an article to be treated such as an iron-based substrate
and a zinc-based substrate, having low reactivity with the
chemical conversion treatment agent. And, also in surface
treatment ofan aluminum-basedsubstrateand a magnesium-based
substrate, it is required to attain a higher level of corrosion
resistance by forming a chemical conversion coat having better
characteristics. Thus, a method of metal surface treatment,
which can form a more uniform and denser chemical conversion
coat, is desired.
Moreover, as a method of metal surface treatment, there
is disclosed a method of surface treatment based on an
electrolysis reaction (cf. for example, Japanese Kokai
Publication 2000-234200 and Japanese Kokai Publication
2002-194589). However, these methods concern a treatment
method of phosphate compounds and titanium-based compounds,
but are not methods for forming a uniform and dense zirconium
chemical conversion coat. Particularly, in a method of
chemical conversion treatment in which phosphate compounds
are used, there is a problem of placing a burden on the
environment due to issues of the eutrophication.
Additionally, in this method, sludge is formed through a
reaction with metal ions in a phosphate treatment bath.
Further, in chemical conversion treatment using a
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titanium-based compound, a high degree of corrosion resistance
cannot be attained.
Further, in International Publication WO 02/103080,
there is disclosed a composition for surface treatment, which
contains a compound (A) including at least one species of Ti,
Zr, Hf and Si, and a fluorine-containing compound (B) as a
source of HF, and in which a ratio of the total' molar weight
A of metal elements of Ti, Zr, Hf and Si in the compound (A)
to the molar weight B in converting the total fluorine atoms
in the fluorine-containing compound (B) to HF, I~=A/B, is within
a range from 0 . 06 to 0. 18, and amethodofmetal surface treatment,
in which a metal surface is contacted with the above-mentioned
composition.
However, in this method, when the chemical conversion
treatment is conducted by the electrolysis treatment using
a composition for surface treatment, which is formed by
dissolving compounds containing fluorine and zirconium, it
is difficult to attain an effect of protecting a cathode in
applying an electrolysis voltage to a substrate to be treated
and a chemical conversion coat, containing a relatively large
amount of fluorides and alkali metal compound, is formed since
a large amount of and excessive fluorine and alkali metals
are present in the solution. Therefore, the corrosion
resistance becomes unsatisfactory. Further, a corrosion
problem of facilities arises due to a large amount of fluorine.
SI7N~1ARY OF THE INVENTION
In view of the above-mentioned state of the art, it is
an object of the present invention to provide a method of metal
surface treatment and a surface treated metal thereby, which
has excellent corrosion resistance and can form a coat having
high corrosion resistance on metal substrates such as iron,
zinc, aluminum and magnesium.
The present invention concerns a method of metal surface
treatment comprising
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the step of forming a chemical conversion coat on the
surface of ametal article to be treatedby a chemical conversion
treatment reaction by a chemical conversion treatment agent
containing a zirconium-containing compound and a
fluorine-containing compound,
wherein said chemical conversion treatment reaction is
conducted through catholic electrolysis treatment.
Preferably, the catholic electrolysis treatment is
conducted in conditions that the concentration of the
zirconium-containing compound in the chemical conversion
treatment agent is adjusted to 10 to 100000 ppmon the zirconium
metal equivalent basis, a ratio of weight as the total zirconium
metal to weight of the total fluorine (amount of
zirconium/amount of fluorine is adjusted to within 0.2 to
1.0 and a pH of the chemical conversion treatment agent is
adjusted to within 1 to 6.
Preferably, the catholic electrolysis treatment is
conducted in conditions of voltage of 0.1 to 40 V and current
density of 0.1 to 30 A/dm2.
Preferably, the metal article to be treated is at least
one species selected from the group consisting of an
aluminum-based substrate, a zinc-based substrate, an
iron-based substrate, and a magnesium-based substrate.
The present invention also concerns a surface treated
metal having a chemical conversion coat attained by the method
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described
in detail.
The method of metal surface treatment of the present
invention is a method in which a chemical conversion coat is
formed by treating the metal surface with a chemical conversion
treatment agent containing a zirconium-containing compound
and a fluorine-containing compound by a catholic electrolysis
CA 02470445 2004-06-08
technique. When the chemical conversion treatment reaction
is conducted through cathodic electrolysis treatment, coats
to be obtained will be dense and excellent in uniformity
compared with a chemical conversion coat obtained by using
5 electroless treatment. Therefore, there is formed the
chemicalconversion coat having high corrosion resistance even
when an amount of a coat formed is identical to that of the
chemical conversion coat obtained by using the electroless
treatment.
IO When an electrolytic reaction is conducted using the
chemical conversion treatment agent containing a
zirconium-containing compound and a fluorine-containing
compound, it is possible to attain a corrosion resistant
chemicalconversion coat having extremely excellentcorrosion
resistance and to attain better corrosion resistance than a
chemicalconversion coat obtained by the electrolytic reaction
of a titanic chemical conversion treatment agent or aphosphate
salt chemical conversion treatment agent. Accordingly, this
method is expected to be applied to a wide range of uses and
preferred.
When it is done to form a chemical conversion coat on
an aluminum-based substrate by electroless treatment using
the chemical conversion treatment agent containing a
zirconium-containing compound and a fluorine-containing
compound, etching of a substrate as expressed by the following
reaction equations (1) and (2) occurs at first, and
subsequently hydrolysis of fluorozirconium as mainly
expressed by the following reaction equations ( 3 ) to ( 5 ) occurs .
Thereby, a zirconium chemical conversion coat is formed.
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6
A1(OH)3 + 3H+ ---~- Also + 3Hz0 (1 )
2A1 + 6H~ --~- 2AI~+ + 3H~ (2) ,
2A13+ -~- ZrF~2- + 3H20 ---~- Zr0(OH)2 ~, + 2A1F3 + 4H+ (3)
4l3A13'" + ZrFs2 + H20 ~"' ZrOF2 ~r + 4l3A1F3 + 2H+ (4)
2Al(OH)3 + ZrF~z --~- (A1020H)2ZrF2 ~ --f- 2F + 2HF (5)
That is, when a coat is formed by the electroless
treatment, since a chemical conversion coat is formed through
the occurrence of reactions shown by the above-mentioned
reaction equations (1) to (5), azirconiumchemicalconversion
coat, which contains relatively much fluorine and has the low
corrosion resistance, is formed. On the other hand, when the
cathodic electrolysis treatment is conducted using the
chemical conversion treatment agent containing a
zirconium-containing compound and a fluorine-containing
compound, a reaction of generating hydrogen primarily occurs
on the metal surface and a cathodic corrosion prevention is
applied to a substrate metal. Therefore, the metal surface
is not subj ected to etching and fluoride of the component metal
of the article to be treated is not generated. Accordingly,
deposition of a coat containing relatively stable zirconium
oxide occurs owing to the hydrolysis of the zirconium complex
ion at the vicinity of metal surface, thus a dense and stable
protection coat having a low fluorine content is formed. In
addition, when the chemical conversion coat is formed on an
iron-based substrate or a zinc-based substrate by the cathodic
electrolysis treatment using the above-mentioned chemical
conversion treatment agent, a coat, in which the amount of
CA 02470445 2004-06-08
a
fluorine is reduced, can be formed and so it is assumed that
the corrosion resistance can be enhanced.
In addition, when an aluminum-based substrate is surface
treated, generally, aluminum ions are accumulated in an
equilibrium bath composition. With respect to such a case,
in the electroless treatment, a provision for supply water
and waste water is required because the accumulation of
aluminum of 500 ppm or more inhibits chemical conversion
reactivity. On the other hand, in the cathodic electrolysis
treatment, since a coat is formed in a state that an amount
of etching of aluminum ions is relatively less (an efficiency
of conversion to a coat is high) and there is less effect on
accumulated aluminum ions, needless supply water and waste
water become unnecessary.
The above-mentioned zirconium-containing compound is
not particularly limited as long as it is a compound containing
zirconium and for example, fluorozirconicacidorlithiumsalt,
sodium salt, potassium salt, or ammonium salt thereof,
zirconium fluoride and zirconium oxide can be given. These
compounds may be used alone or in combination of two or more
species.
The above-mentioned fluorine-containing compound is
not particularly limited as long as it is a compound containing
fluorine and for example, the above-mentioned zirconium
fluoride, hydrofluoric acid, ammonium fluoride, ammonium
hydrogenfluoride, sodium fluoride and sodium
hydrogenfluoride can be given. These compounds may be used
alone or in combination of two or more species.
In method of metal surface treatment of the present
invention, the above-mentioned cathod.i.c electrolysis
treatment is preferably conducted in conditions that the
concentration of the zirconium-containing compound in the
chemical conversion treatment agent is adjusted to 10 ppm as
the lower limit and to 100000 ppm as the upper limit on the
zirconium metal equivalent basis, a ratio of weight as the
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s
total zirconium metal to weight of the total fluorine (amount
of zirconium/amount of fluorine) is adjusted to 0.2 as the
lower limit and to 1 . 0 as the upper limit and a pH of the chemical
conversion treatment agent is adjusted to 1 as the lower limit
and to 6 as the upper limit. By conducting the cathodic
electrolysis treatment in conditions adjusted like this, the
corrosion resistance can be enhanced because~a chemical
conversion coat having relatively less fluorine content can
be formed.
In the above-mentioned cathodic electrolysistreatment,
as a method of adjusting the above-mentioned concentration
of the zirconium-containing compound and the above-mentioned
amount of zirconium/amount of fluorine within the
above-mentioned specified ranges, there can be given, for
example, a method of adjusting the concentration of total
zirconium and the concentration of total fluorine in the
chemical conversion treatment agent by replenishing the
above-mentioned zirconium-containing compound and the
fluorine-containing compound in the treatment bath while
measuring the concentration of total zirconium and the
concentration of total fluorine using an atomic absorption
analyzer and using an ion chromatograph, respectively. As
a method of adjusting the pH within the above-mentioned
specified range, there can be given, for example, a method
of adjusting the pH by replenishing nitric acid or ammonium
hydroxide in the treatment bath while measuring the pH using
a pH meter.
In the cathodic electrolysis treatment in the present
invention, with respect to the chemical conversion treatment
agent in the treatment bath, the above concentration of the
zirconium-containing compound is preferably adjusted to
within a range from 10 ppm as the lower limit to 100000 ppm
as the upper limit on the zirconium metal equivalent basis.
When the concentration is less than 10 ppm, the corrosion
resistance may not be achieved since the zirconium compound
CA 02470445 2004-06-08
is not adequately deposited on the metal surface. When it
is more than 100000 ppm, it maybe economically disadvantageous
sincefurtherimprovementisnot recognized. More preferably,
the above-mentioned lower limit is 30 ppm and the
above-mentioned upper limit is 5000 ppm.
In the cathodic electrolysis treatment in the present
invention, with respect to the chemical conversion treatment
agent in the treatment bath, a ratio of weight as the total
zirconium metal (the weight of total zirconium as zirconium
metal contained in the chemical conversion treatment agent)
to weight of the total fluorine (the weight of total fluorine
containedin the chemical conversion treatment agent) (amount
of zirconium/amount of fluorine) is preferably adjusted to
fall within a range from 0.2 as the lower_ limit to 1.0 as the
upper limit. When the ratio is less than 0.2, the formation
of the chemical conversion coat by the cathodic electrolysis
treatment may be counteracted since the amount of fluorine
becomes excessive. Further the corrosion resistance may be
deteriorated since a chemical conversion coat having
relatively much fluorine content . When it is more than 1 . 0,
precipitation of metal salt may be occurred since the amount
of the totalfluorine becomesinsufficient. More preferably,
the above-mentioned lower limit is 0 . 25 and the above-mentioned
upper limit is 0.8.
In the cathodic electrolysis treatment in the present
invention, with respect to the chemical conversion treatment
agent in the treatment bath, the pH is preferably adjusted
to within a range from 1 as the lower limit to 6 as the upper
limit. When the pH is less than 1, the zirconium compound
becomes difficult to deposit, and therefore a sufficient amount
of the coat cannot be obtained and the corrosion resistance
maybe deteriorated. When it is more than 6, it is not preferred
since a sufficient amount of the coat cannot be obtained. More
preferably, the above-mentioned lower limit is 2 and the
above-mentioned upper limit is 5.
CA 02470445 2004-06-08
In addition to the above-mentioned ingredients, the
above-mentioned chemical conversion treatment agent may
contain metal ions such as titanium, manganese, silicon, zinc,
cerium, iron, molybdenum, vanadium, trivalent chromium,
5 magnesium and the like; another rust prevention materials such
as a tannic acid, imidazoles, triazines, triazoles, guanines,
hydrazines, biguanide, a phenolic resin,, a silane coupling
agent, colloidal silica, amines and phosphoric acid: a
surfactant; chelator; and the resins.
10 In the method of metal surface treatment of the present
invention, the above-mentioned catholic electrolysis
treatment conducts electrolysis treatment: by using an article
to be treated as a cathode.
With respect to the above-mentioned catholic
electrolysis treatment, its voltage is preferably within a
range from 0.1 V as the lower limit to 40 V as the upper limit.
When the voltage is less than 0.1 V, the amount of the coat
is insufficient; therefore the corrosion resistance may be
deteriorated. When it is more than 40 V, effect from increase
in the amount of the coat becomes saturated and energy
disadvantage may occur. More preferably,theabove-mentioned
lower limit is 1 V and the above-mentioned upper limit is 30
V.
With respect to the above-mentioned catholic
electrolysis treatment, its current density is preferably
within a range from 0.1 A/dm2 as the lower limit to 30 A/dm2
as the upper limit. When the current density is less than
0.1 A/dm2, the amount of the coat is insufficient; therefore
the corrosion resistance may be deteriorated. When it is more
than 30 A/dm2, effect from increase in the amount of the coat
becomes saturated and energy disadvantage may occur. More
preferably, the above-mentioned lower limit is 0.2 A/dm2 and
the above-mentioned upper limit is 10 A/dm2.
A treatment time of the above catholic electrolysis
treatment is preferably 3 seconds as the lower limit and 180
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seconds as the upper limit. When the treatment time is less
than 3 seconds, the amount of the coat is insufficient;
therefore the corrosion resistance may be deteriorated. When
it is more than 180 seconds, effect from increase in the amount
of the coat becomes saturated and energy disadvantage may
occur.
A treatment temperature of the above cathodic
electrolysis treatment is preferably 10°C as the lower limit
and 70°C as the upper limit. When the treatment temperature
is less than 10°C, the amount of the coat is insufficient;
therefore thecorrosion resistance may be deteriorated. When
it is more than 70°C, effect from increase in the amount of
the coat becomes saturated and energy disadvantage may occur.
In addition, the lower limit of the treatment temperature is
not particularly controlled and the cathodic electrolysis
treatment can be conducted at room temperature.
Material of an electrode used as a counter electrode
in the above cathodic electrolysis treatment is not
particularly limited as long as the electrode does not dissolve
in the above chemical conversion treatment agent and for
example, stainless steel, titanium plated with platinum,
titanium plated with niobium, carbon, iron, nickel, and zinc
can be given.
As an article to be treated to which the method of metal
surface treatment of the present invention can be applied,
there can be given an iron-based substrate, an aluminum-based
substrate, a zinc-based substrate and a magnesium-based
substrate. Iron, aluminum, zinc and magnesium-based
substrates refer to an iron-based substrate in which a
substrate consists of iron and/or its alloy, an aluminum-based
substrate in which a substrate consists of aluminum and/or
its alloy, a zinc-based substrate in which a substrate consists
of zinc and/or its alloy, and a magnesium-based substrate in
which a substrate consists of magnesium and/or its alloy,
respectively. Particularly, the method of metal surface
CA 02470445 2004-06-08
12
treatment of the present invention can also form a chemical
conversion coat having sufficient corrosion resistance on an
iron-based substrate and a zinc-based substrate, for which
conventionally, phosphatesalt chemical conversion treatment
agents have been usually used because sufficient corrosion
resistance could not be attained through zirconium chemical
conversion treatment agents. Therefore, it can also be
applied to the purpose of dephosphorylation. By applying the
method of metal surface treatment of the present invention
to the chemical conversion treatment of an article to be treated,
consisting of a plurality of substrates of an iron-based
substrate, an aluminum-based substrate, a zinc-based
substrate and a magnesium-based substrate, the excellent
corrosion resistance can be provided for each article to be
treated.
The above-mentioned iron-based substrate is not
particularly limited and, for example, a cold-rolled steel
sheet and a hot-rolled steel sheet can be given. The
above-mentioned aluminum-based substrateis not particularly
limited and, for example, 5000 series aluminum alloys and 6000
series aluminum alloys can be given.
The above-mentioned zinc-based substrate is not
particularly limited and, for example, steel sheets, which
are plated with zinc or a zinc-based alloy through
electroplating, hot dipping and vacuum evaporation coating,
such as a galvanized steel sheet, a steel sheet plated with
a zinc-nickel alloy, a steel sheet plated with a zinc-iron
alloy, a steel sheet plated with a zinc-chromium alloy, a steel
sheet plated with a zinc-aluminum alloy, a steel sheet plated
with a zinc-titanium alloy, a steel sheet plated with a
zinc-magnesium alloy and a steel sheet plated with a
zinc-manganese alloy can be given.
The above-mentioned magnesium-based substrate is not
particularly limited and, for example, magnesium metal and
magnesium alloys prepared by rolling, die casting or a
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thixomolding process can be given. The above-mentioned
magnesium alloy is not particularly limited and, for example,
AZ 31, AZ 91, AZ 91D, AM 60, AM 50 and AZ 31B can be given.
By using the above-mentionedmethodaf metal surface treatment,
iron, aluminum, zinc and magnesium-based substrates can be
simultaneously chemical conversion treated.
An amount of zirconium in the chemical conversion coat
formed by the above°mentionedmethodofmet.al surfacetreatment
is preferably within a range from 10 mg/m2 as the lower limit
to 300 mg/m2 as the upper limit. Thereby, the excellent
corrosion resistance can be provided. When this amount is
less than lOmg/m2, the corrosion resistance maybe insufficient.
When it is more than 300 mg/m2, it may be economically
disadvantageous since further improvement in the corrosion
resistance is not recognized. More preferably, the
above-mentioned lower limit is 20 mg/m2 and the above-mentioned
upper limit is 150 mg/m2.
The surface of the above-mentioned metal substrate is
preferably degreased, rinsedwithwaterafterbeingdegreased,
acid cleaned and rinsed with water after acid cleaning before
the catholic electrolysis treatment is conducted using the
chemical conversion treatment agent.
The degreasing is performed to remove an oil matter or
a stain adhering to the surface of the substrate and immersion
treatment is conducted usually at 30 to 55°C for about several
minutes using a degreasing agent such as phosphate-free and
nitrogen-free cleaning liquid for degreasing. It is also
possible to perform pre-degreasing before degreasing as
desired.
Theabove-mentioned rinsing with water after degreasing
is performed by spraying once or more with a large amount of
water for rinsing in order to rinse a degreasing agent after
degreasing.
As the above-mentioned acid cleaning, immersion
treatment is conducted usually at 30 to 60°C for about several
CA 02470445 2004-06-08
14
minutes using, for example, an acid cleaning agent such as
sulfuric acid containing an oxidizer or an mixed acid cleaning
solution of sulfuric acid and nitric acid. The
above-mentioned rinsing after acid cleaning can be conducted
using the conventional method publicly known. Rinsing with
water may be performed after the cathodic electrolysis
treatment.
The present invention also concerns a surface treated
metal having the chemical conversion coat attained by the
above-mentioned method of metal surface treatment. The
surface treated metal of the present invention exhibits the
high corrosion resistance when corrosion resistant primer
coating compositionsuch ascation electrocoating compostion,
powder coating composition and thermosetting
resin-containing coating composition is applied on the
above-mentioned chemicalconversion coat. Coating,which can
be applied to the surface treated metal of the present invention,
is not particularly limited and the cation electrodeposition
coating, the powder coating and roller coating can be conducted.
The above-mentioned canon electrodeposition coating is not
particularly limited and the conventional cation
electrocoating composition publicly known, consisting of
aminated epoxy resin,aminated acrylic resin,sulfonated epoxy
resin and the like, can be applied.
Since the method of metal surface treatment of the
present invention is a method in which the chemical conversion
coat is formed by treating the surface of metal with a chemical
conversion treatment agent containing a zirconium-containing
compound and a fluorine-containing compound by the cathodic
electrolysis technique, treated material having the high
corrosion resistance can be attained. And, since the method
of metal surface treatment of the present invention can provide
the excellent corrosion resistance for all substrates of iron,
zinc, aluminum and magnesium-based substrates and does not
contain hexavalent chromium, it is also preferred in terms
CA 02470445 2004-06-08
of the environmental protection.
Particularly, when the cathodic electrolysis treatment
is conducted in conditions that the concentration of the
zirconium-containing compound in the chemical conversion
5 treatment agent is adjusted to 20 to 100000 ppm an the zirconium
metal equivalent basis, a ratio of weight as the total zirconium
metal to weight of the total fluorine (amount of
zirconium/amount of fluorine) is adjusted to within 0.2 to
1.0 and a pH of the chemical conversion treatment agent is
10 adjusted to within 1 to 6, a chemical conversion coat having
relatively less fluorine content is formed, and therefore the
corrosion resistance can be more enhanced.
Since the chemical conversion treatment agent used in
the present invention can provide the excellent corrosion
15 resistance even when it does not contain phosphate ions, the
method of metal surface treatment of the present invention
will not cause environmental issues of the eutrophication or
the like and can also suppress the amount of sludge.
Since the method of metal surface treatment of the
present invention is constituted as de;~cribed above, the
corrosion resistance can be more enhanced than the case where
the electroless treatment is conducted, or the electrolysis
treatment is conducted using a titanic treatment agent or a
phosphate treatment agent. Since this method can provide the
excellent corrosion resistance for all material such as an
iron-based substrate, an aluminum-based substrate, a
zinc-based substrate and a magnesium-based substrate, it can
also be suitably used to articles to be treated, which consists
of a plurality of substrates of an iron-based substrate, an
aluminum-based substrate, a zinc-based substrate and a
magnesium-based substrate, such as bodies and parts of
automobiles . And, the method of the present invention is also
a method which places a less burden on t=he environment and
suppresses the formation of sludge.
CA 02470445 2004-06-08
is
The method of metal surface treatment of the present
invention can be favorably applied to an article to be treated
such as an iron-based substrate, a zinc--based substrate, an
aluminum-based substrate and a magnesium-based substrate.
EXAMPLES
Hereinafter, the present inventic>n will be described
in more detail by way of examples, but the present invention
is not limited to these examples. In addition, "part(s)"
refers to "weight part ( s ) " and "~" means "weight o" in Examples,
unless otherwise specified.
Examples 1 to 13 and Comparative Examples 1 to 7
Preparation of chemical conversion treatment agent
Chemical conversion treatment agents shown in Tables
1 and 2 were prepared by mixing fluorozirconic acid, ammonium
fluorozirconate, fluorotitanic acid and hydrofluoric acid as
a zirconium-containing compound and a fluorine-containing
compound, phytic acid, aluminum nitrate, phosphoric acid,
water-soluble phenol and tannic acid, and adding ion-exchanged
water to the mixture.
Preparation of test sheet
Test sheets having a size of 70 mm x 150 mm x 0.8 mm
(A1100 manufactured by Nippon Testpanel Co., Ltd.) were
degreased by immersing at 70°C for 30 seconds using a 3 o aqueous
solution of an alkaline degreasing agent (SURFCLEANER 322N8
manufactured by NIPPON PAINT Co., Ltd.). After rinsing by
spraying with running water for 30 seconds, the test sheets
were acid-cleaned by immersing at 70°C for 30 seconds using
a 25% aqueous solution of an acid cleaning agent (NP Conditioner
2000 manufactured byNIPPON PAINT Co., Ltd. ) . The test sheets
were rinsed by spraying with running water for 30 seconds,
and then treated in the prepared chemical conversion treatment
agent under conditions shown in Tables 1 and 2 with the counter
CA 02470445 2004-06-08
17
electrode as the SUS 304 anode by a cathodic electrolysis
technique. In addition, the amount of zirconium (mg/m2) in
the coat and the weight ratio of fluorine to zirconium (F/Zr)
in the coat were analyzed by using "XRF-1700" (X-ray
fluorescence spectrometer manufactured by Shimadzu Corp.).
In addition, in cathodic electrolysis treatment,
treatments conditions were adjusted according to~the following
manners in such a way that the concentration of zirconium metal,
a weight ratio of zirconium to fluorine anal a pH, in the chemical
1D conversion treatment agent in the treatment bath, became values
as shown in Tables Z and 2.
The concentration of total zirconium in the chemical
conversion treatment agent in the treatment bath was adjusted
while being measured using NOVA A330 (an atomic absorption
analyzer manufactured by Rigaku Corporation) and the
concentration of total fluorine in the chemical conversion
treatment agent in a treatment bath was adjusted while being
measured using DX-120 (an ion chromatograph manufactured by
Nippon D~ionex K. K. ) , by replenishing ammonium fluorozirconate
and hydrofluoric acid in a treatment bath respectively. The
pH of the chemical conversion treatment agent in a treatment
bath was adjusted by replenishing nitr_~c acid or ammonium
hydroxide in the treatment bath while being measured using
D-24 (a pH meter manufactured by HORIBA, Ltd.).
Evaluation of physical properties of test sheet
With respect to the above-mentioned test sheets,
corrosion resistance was evaluated by an evaluation method
described below.
<Corrosion resistance
According to JIS Z 2371, the salt spray tests using 5 0
salt water (2000 hours) were conducted and the rust-formation
rates of the treated sheets were checked after that test . Rust
area on the surfaces of the treated sheets was evaluated
visually according to the following criteria.
CA 02470445 2004-06-08
18
10: no white color rust
9: area with white colo r rust formed is less than
100
8: likewise, less than 200
7: likewise, less than 300
6: likewise, less than 400
5: likewise, less than 500
4: likewise, less than 600
3: likewise, less than 70%
2: likewise, less than 800
1: likewise, less than 900
CA 02470445 2004-06-08
19
Table 1
o I I I I O i I I ~
~ ~ O ~ O
O O ch1 ~ O OD
1 0 0 I 1 1 ! ! ~ ~ n N
t7 C
C 1 I 1 ~ 1 I I ~ t~
I C O ~ ~ M N ~.yQ
i O 1 I I ~ I i o O ~ 1nN ~
c o o ~ "' I i '''o '''
O i i I I I I M ~ e~
I c7 ~ C ~. ~ p
,y
I I I ~ 1 1 1 O O O ~ ~ ca,Op
I Q a ofm osI np~ Ci
.-.
O "' M 10O O O O N f~
I o I 1 1 ~ I t ! ~,ju~M ~ ~op c0
_
Q
I ~ I I I o i i I ~ ~ O ~ m ~
c ~ a
~s
1 I I I o t I o ~ O ~ ~ ~ a
M ~ M 1 ~ ~ O
. ~ ~ ~ w
I o I I I 1 I O 1 i,~ M , c0
. O j I ~ ~,
5
C O
I Q 1 I i 1 I ~ M o aD
o ~ "~o
O
CO O In If7
I I r M ~ c n
I d 1 a a r , ; a
o I I I I ~ I I I "~O o u'
c o riusc~ q c c
;
.~ ~E
c
o e ~ c ~ ~E
y 'c _ ~ m
'u r ~ ~ E ~ w E
m , ~ > ~
. ..~
Y
' ; m W y COD ~ 7
X . ~ ~ l0
O
?~ x a a .w : ~ v ~
s
fo t 5 o ~ m m
~ .'; '~ o
.
_ ' .
. x o x o o E N
'
~ ; ; ' n v U v ',?3 N,o
3
' u'W a ~ s c o ~
F-
o era + o ~
.
eo~ ~ o m a ; _ u v
v . a
~ ~ ~ E '~ ~ c v ~ v 'H~ ~'~
E 'N c
O ~ ~ 10 W V ~ L
~ . a
~ y o O V _
~ ~ A
o O O O . ~ N
~
U U
E~ ~ s ~ W c aE d ~
a
. I Z E e
u. a lia ._~ c 3 a a E= a a n
'N a E-t- W 3
1n
0
i-~ C C N
C
N a a~ 'G
y O
U
E E ~
~ U
d
i ~ M
O C L
+~ ~ I t
V O
N U
1...
* -(minus) indicates cathodic electrolysis treatment.
Weight ratio of F/Zr indicates measurements by X-ray
fluorescence spectrometer.
CA 02470445 2004-06-08
Table 2
N
N
C N
O
O p Y
o N I t -
n s ~ .~1 I I 1 1 N ~ Y ~
~ U C
M 4 V
'
z ,
d
P. O i17
!L I I ' re~ '' o i ch
~
~tD 1 1 0 0 l OE- I ~"t c ~
.? ~
v
~ 1 I i I I . I 1 0 ~ ~ M ~ O 1 Y
~
r et' O N
Uv I o 1 1 1 p I I I M ~ aoI 1 ~ o N
ch p i I I I ' I I p N i I ~ N
O O O ~ N ~ O
N I I I I I I l ~ ~ ~ I I N
~ p M o
- ~ I I I I T- I I I M ~ opoI I ~ ~ M
. d o d
+a
.-. c
E ~
~ _ ~ ~ N
E
C R ~ c c E
v ~
a c '
+
'N'~ ~ 3 ~ j E it
p , ~ v
_ ~ ~ aR
'
~ ii+' +
~ U ~'
are~ I~w ~ ~ a U o t
,, ~ . 00
U ~ W ~. ~
C ~ ~ ~ ~ ~ ~ V G R
. ,.-~ ... ~ C
~ ~ .
_ N
a ~ r '
3 ~ t~o
N '''~ ''' ; v s
O v no~ N ~ .~ C G ~p la.!-
if
~ ' ~ "
3 "Lo ~ v 3 c c _~ o
' ~ ~~
C ~ V ~ o W ~ N p v
~ ' ~ 'C ~ ~~V INN ~ ~ =
C ~ V r ~NN
V E I t E . O W . U 7~T t
q p Ip ~9 0
a.
c c c ,*' t ~ ~ v o o c
._ ~
E , '~ ~nat . ' a ~ ~ o
c '
o E ~ ~,E a ~ ~ ~ E m o~ E w ~
~
~
s
s Z c
1~a ~.n.a 3 a W --a t.-H ur a ~ ~y
.N cn
0
n a ~
o m
+.
E E:~ +:
c a
m ~ ~
m ~ W
~ a L
o ....
F- !-
* -(minus) indicates cathodic electrolysis treatment.
Weight ratio of F/Zr indicates measurements by X-ray
5 fluorescence spectrometer.
CA 02470445 2004-06-08
21
Tables 1 and 2 show that the test sheets obtained by
using the electroless treatment (Comparative Examples 1 to
5) were inferior to the test sheets obtained by using the
cathodic electrolysis treatment (Examples) in the corrosion
resistance. Thereby, it was apparent that the corrosion
resistance can be improved by conducting the cathodic
electrolysis treatment to form a coat. And, the test sheet
using fluorotitanic acid (Comparative Example 6) was inferior
to the test sheet using a chemical conversion treatment agent
containing zirconium in the corrosion resistance.
Examples 14 to 21 and Comparative Examples 8 to 11
Preparation of chemical conversion treatment agent
Chemical conversion treatment agents shown in Table 3
were prepared by mixing fluorozirconic acid as a
zirconium-containing compound and a fluorine-containing
compound, and nitrate salt as another metal-containing
compound, and adding ion-exchanged water to the mixture.
Preparation of test sheet
SPCC-SD of 70 mm x 150 mm x 0 . 8 mm (manufactured by Nippon
Testpanel Co., Ltd.), galvanized steel sheet of 70 mm x 150
mm x 0.8 mm (GA steel sheet, manufactured by Nippon Testpanel
Co . , Ltd. ) and 5182 series aluminum of 70 mm x 150 mm x 0 . 8
mm (manufactured by Nippon Testpanel Co . , Ltd. ) were degreased
by spraying at 40°C for 2 minutes using a 2 o aqueous solution
of an alkaline degreasing agent (SURFCLEANER 53 manufactured
by NIPPON PAINT Co., Ltd. ) . After rinsing by spraying with
running water for 30 seconds, these metal sheets were treated
in the prepared chemical conversion treatment agent under
conditions shown in Table 3 with the counter electrode as the
SUS 304 anode by a cathodic electrolysis technique. Next,
the metal sheets were rinsed by spraying with running water
for 30 seconds, and then rinsed by spraying with pure water
CA 02470445 2004-06-08
22
for 30 seconds . Then, electrocoating was applied to the metal
sheets in such a way that a dried film thickness was 20 ~.m
using "POWERNICS 110" (a cation electrocoating paint
manufactured by NIPPON PAINT Co . , Ltd. ) and after rinsing with
water, the metal sheets were heated and baked at 170°C for
20 minutes to prepare test sheets.
The concentration of total zirconium in~the chemical
conversion treatment agent in the treatment bath was adjusted
while being measured using NOVA A330 (a.n atomic absorption
analyzer manufactured by Rigaku Corporation) and the
concentration of total fluorine in the chemical conversion
treatment agent in the treatment bath was adjusted while being
measured using DX-120 (an ion chromatograph manufactured by
Nippon Dionex K. K. ) , by replenishing ammonium fluorozirconate
and hydrofluoric acid in the treatment bath respectively so
as to become values as shown in Table 3 . The pH of the chemical
conversion treatment agent in the treatment bath was adjusted
by replenishing nitric acid or ammonium hydroxide in the
treatment bath while being measured using D-24 (a pH meter
manufactured by HORIBA, Ltd. ) so as to become values as shown
in Table 3.
Comparative Example 12
Preparation of test sheet
SPCC-SD of 70 mm x 150 mm x 0 . 8 mm was degreased by spraying
at 40°C for 2 minutes using a 2% aqueous solution of an alkaline
degreasing agent (SURFCLEANER 53 manufactured by NIPPON PAINT
Co., Ltd. ) . After rinsing by spraying with running water for
seconds, the metal sheet was surface treated at room
30 temperature for 30 seconds using "SURFFII~'E 5N-8M" (a surface
conditioner manufactured by NIPPON PAINT Co., Ltd. ) . Then,
the metal sheet was treated in "SURFDINE SD-6350" (a chemical
conversion treatment agent based on zinc phosphate
manufactured by NIPPON PAINT Co . , Ltd. ) under conditions shown
in Table 3 with the counter electrode as the SUS 304 anode
CA 02470445 2004-06-08
23
by a cathodic electrolysis technique . Next, the metal sheet
was rinsed by spraying with running water for 30 seconds, and
then rinsed by spraying with pure water for 30 seconds . Then,
electrocoating was applied to the metal sheet in such a way
that a dried film thickness was 20 ~.m using °°POWERNICS 110"
(an electrocoating paint manufactured by NIPPON PAINT Co.,
Ltd. ) and after rinsing with water, the metal sheet was heated
and baked at 170°C for 20 minutes to prepare a test sheet.
Comparative Example 13
A test sheet was prepared by following the same procedure
as in Comparative Example 12 except for using electroless
treatment in place of cathodic electrolysis treatment.
Evaluation of physical properties of test sheet
<Secondary adhesion test (SDT)>
With respect to the above-mentioned test sheets,
secondary adhesion was evaluated by an evaluation method
described below.
Two parallel lines, which have depi~h reaching the base
material, were cut in a longitudinal direction on the test
sheets and then the test sheets were immersed at 50°C for 480
hours in a S% aqueous solution of NaCl. After immersion, cut
portions were peeled off with an adhesive tape and peeling
of a coating was observed. Results of ob:>ervations are shown
in Table 3.
o: width of peeling is narrow than 3 mm
x: width of peeling is 3 mm or wider
<sludge>
After the cold-rolled steel sheet (SPCC-SD), the
galvanized steel sheet and the 5182 series aluminum were
treated in conditions of their areas of 1 m2 per liter of the
chemical conversion treatment agent, haze in the chemical
conversion treatment agents was visually observed.
Image
CA 02470445 2004-06-08
Table 3
ose9-os I I ii I I 1 O x
3Naa~ans
~N O I I O x
osae-as i I I
3Nio~ans
-
I I ( ( ~ x O
,y,T~ O T I ~,;~ cfl m
C C
_o m
i I N x O
T(sO O, I i i ~,.j! tp ~
p
B C O
j a Q p I 1 I ~ $ I I N ~ x O
~o~ c <
o
0 0
a o ~ ~" MI I ~ o x O
0o I I I .;.
~.~
c c
N O_ C> O ~ o O O
O I L O O
N O 1'~I pjV t~
' p O
C O
I I O OO ~ O O
~
O r. I M V t ~ ~
p
O G
o~a o ~ o o I ' o o ' ~ ,NaO O
N ~ O 0 M O t0I ~ C)
c o
ooa o w o 0 0 '-o o~.,~~ ~ ~ O
v ~ ~"' 0 't~'~I
0 0 I ci
0 0
i~a a o N ~ ~ O O
.
t I ~ c ~ ~ a
r '~
c o
V o m m p wn u~ N ~r
s 4 s o p~ o ~ 0 0
' o ~' o o c ~'~''', , r o
O Ci
O O I ~ ~ mN G O O O
, I ~
G O O O O
V ' ~ O O
' I '
'
o r I 1 ~;~rc~ ~ ti
.
co 0
. B U S .m G 1+'CW
it C .Z t0 ~ O O
m
N ~ N p ~ O B N
v v C C
.
B C C
. 3 O E
.
. LL ' .~ _m O N
ate.m LE0-a U
'~ ~ l
N '-y ~ c o i.
v ~
a '' ~ 3 m ~-' O O i '
m ~ o N o
o v
eo c r m E . o
N
V :~3_ ~ ~ r VN H
n y E n ~
E
a. ~ ~7 ~ c0 v0dT 7~ O
E C _~ x 'Q H
_ ~'Eoar cm "'o o' ~ ~ m
E
'~ ~ c ' Q.~. = ~ ' f-
m g O .
V
~
o . o v ,~ ~
~ e y m
~ o
u ~r ~ i~ r~ Q.F t=ui t~
. +' E ; - -n
'' ~
i
a
N
.iA
C1d G7 1
.,r ~ O
d r ~
~ V
t N la 10
41 C 11
E N ~ ~ ~
V O
U
* -(minus) indicates cathodic electrolysis treatment.
Weight ratio of F/Zr indicates measurements by X-ray
5 fluorescence spectrometer.
CA 02470445 2004-06-08
26
Table 3 shows that the test sheets obtained by using
the electroless treatment (Comparative Examples 8 to 13) had
lower adhesion (wider peeling width) than the test sheets
obtained by using the cathodic electrolysis treatment
(Examples 14 to 21). Thereby, it became apparent that the
adhesion can be improved by conducting the cathodic
electrolysis treatment to form a coat. And, in Examples 14
to 18, the formation of sludge was suppressed compared with
the cases where the electrolysis treatment was conducted
(Comparative Example 12) and the electroless treatment was
conducted (Comparative Example 13) using a zinc phosphate
treatment agent, respectively.
Examples 22 to 23
Preparation of chemical conversion treatment accent
Chemical conversion treatment agents shown in Table 4
were prepared by mixing fluorozirconic acid and ammonium
fluorozirconate as a zirconium-containing compound and a
fluorine-containing compound, and
y-aminopropyltriethoxysilane, and addingion-exchanged water
to the mixture.
Preparation of test sheet
Magnesium alloy AZ91D of 70 mm x 150 mm x 2 . 0 mm obtained
by a thixomolding process was degreased by spraying at 50°C
for 2 minutes using a 1~ aqueous solution of an alkaline
degreasing agent (SURF MAGDINE SF120 CLEANER manufactured by
NIPPON PAINT Co., Ltd.). After rinsing by spraying with
running water for 30 seconds, the metal sheet was acid-cleaned
by spraying at 50°C for 2 minutes using a 1% aqueous solution
of an acid cleaning agent (SURF MAGDINE SF400 manufactured
by NIPPON PAINT Co., Ltd. ) . After rinsing by spraying with
running water for 30 seconds, the metal sheet was acid-cleaned
by spraying at 60°C for 5 minutes using a 10 o aqueous solution
CA 02470445 2004-06-08
27
of a desmutting treatment agent (SURF I~IAGDINE SF300
manufactured by NIPPON PAINT Co., Ltd.). After rinsing by
spraying with running water for 30 seconds, the metal sheet
was treated in the prepared chemical conversion treatment agent
under conditions shown in Table 4 with the counter electrode
as the SUS 304 anode by a catholic electrolysis technique.
Next, the metal sheets were rinsed by s~>raying' with running
water for 30 seconds, and then rinsed by spraying with pure
water for 30 seconds.
The concentration of total zirconium in the chemical
conversion treatment agent in the treatment bath was adjusted
while being measured using NOVA A330 (an atomic absorption
analyzer manufactured by Rigaku Corporation) and the
concentration of total fluorine in the chemical conversion
treatment agent in the treatment bath was adjusted while being
measured using DX-120 (an ion chromatograph manufactured by
Nippon Dionex K. K. ) , by replenishing ammonium fluorozirconate
and hydrofluoric acid in the treatment bath respectively so
as to become values as shown in Table 4 . The pH of the chemical
conversion treatment agent in the treatment bath was adjusted
by replenishing nitric acid or ammonium hydroxide in the
treatment bath while being measured using D-24 (a pH meter
manufactured by HORIBA, Ltd. ) so as to become values as shown
in Table 4.
Comparative Example 14
A test sheet was prepared by following the same procedure
as in Example 22 except that immersion treatment was conducted
at 50°C for 2 minutes using a 5% aqueous solution of a
commercially available manganese phosph;~te treatment agent
(SF572 manufactured by NIPPON PAINT Co., Ltd.) in place of
chemical conversion treatment based on catholic electrolysis
treatment.
Comparative Example 15
CA 02470445 2004-06-08
28
A test sheet was prepared by following the same procedure
as in Example 22 except that immersion treatment was conducted
at 50°C for 2 minutes using a 5o aqueous solution of a
commercially available zirconium phosphate treatment agent
(ALSURF 440 manufactured by NIPPON PAINT Co . , Ltd. ) in place
of chemical conversion treatment based on cathodic
electrolysis treatment. '
With respect to the test sheets obtained in Examples
22 and 23 and Comparative Examples 14 and 15, corrosion
resistance was evaluated in a manner as described below.
The corrosion resistance was evaluated by following the
same procedure as in the evaluation in Example 1 except that
48 hours was used as an evaluation time of the corrosion
resistance in place of 2000 hours.
CA 02470445 2004-06-08
29
Table 4
0
d
r ~ ~ N I I r N
~ O
X
J
Q
o.
E .
Q N
U ~
_
r ,~ O ~ I I o N
,
T
N
d
Lt7 0~0 D 11'1 p p O r
G1 M
G1 ~ ~ i'rj M j r O
M
H
_u
Q
E
N
X
W
N r h 0 ti's p ~ N r p
p
N ~ Q cr'j t~ j ,-: G7 r
c'
3 ~ c ao
~ a ~
+ .~d N '~'~L
10
V
~ c c
>~ _
'n a
N L U .~ +~ G t
O
R L N ~ c c a o0
iI-
a o 4. y, ,r o oN o
E o o ~ - ,~ u~
4i V ~ :~ Q. ~ ~ N N H
r~ .~ 'N v
-N
\
.i .N .~ ~ ~ l N a
= Q 0
o o *' '~ L ....a a L
c' L a ,,,,
~ ~ ~ ~
'w~
~
L 3 ~ = m E ~ d o ci
~
a ~ Q ~ ~ a t- i- u~ u.t ti c~
Iv w -v
N
c
O U
ii
+~
~ ~
V +a 4 N ~
~ !
+r
~d
E . .~c ~v
m
V O
U e+.yE... I~ t
m U
H
* -(minus) indicates cathodic electrolysis treatment.
CA 02470445 2004-06-08
Table 4 shows that the test sheets obtained in Examples
22 and 23 were superior to those obtained in Comparative
Examples 14 and 15 in corrosion resistance.
5
