U.S. patent number 3,849,176 [Application Number 05/235,864] was granted by the patent office on 1974-11-19 for surface-treated steel plates high in anticorrosiveness.
This patent grant is currently assigned to Nippon Steel Corporation. Invention is credited to Hidejiro Asano, Yashichi Ouyagi.
United States Patent |
3,849,176 |
Asano , et al. |
November 19, 1974 |
SURFACE-TREATED STEEL PLATES HIGH IN ANTICORROSIVENESS
Abstract
A surface-treated steel plate high in anti-corrosiveness which
plate has been produced by coating a steel plate with an aqueous
solution containing the nitrate or acetate of Ni as the principal
component in conjunction with such metals as Cr, Mn, Zn and Al as
selective components, followed by heating to produce a
thermodecomposing reaction so as to cause a strong film containing
metallic nickel and at least one metallic oxide to form on the
surface of the steel plate. The thus-produced surface-treated steel
plate is especially adapted for making cans.
Inventors: |
Asano; Hidejiro (Kitakyushu,
JA), Ouyagi; Yashichi (Kitakyushu, JA) |
Assignee: |
Nippon Steel Corporation
(Tokyo, JA)
|
Family
ID: |
27287880 |
Appl.
No.: |
05/235,864 |
Filed: |
March 17, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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32439 |
Apr 27, 1970 |
3677797 |
|
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|
Foreign Application Priority Data
|
|
|
|
|
Apr 28, 1969 [JA] |
|
|
44-32874 |
|
Current U.S.
Class: |
428/626; 428/472;
428/500; 428/639; 428/679; 428/681; 428/684; 428/926 |
Current CPC
Class: |
C23C
18/02 (20130101); C23C 8/10 (20130101); B05D
7/16 (20130101); B05D 2504/00 (20130101); Y10T
428/12951 (20150115); Y10T 428/31855 (20150401); B05D
2350/63 (20130101); Y10T 428/12972 (20150115); Y10T
428/12569 (20150115); Y10T 428/12937 (20150115); Y10S
428/926 (20130101); Y10T 428/1266 (20150115) |
Current International
Class: |
C23C
18/00 (20060101); C23C 18/02 (20060101); B05D
7/14 (20060101); C23C 8/10 (20060101); B44d
001/16 () |
Field of
Search: |
;117/71M,127,130,75
;29/196.6,195M,195L ;148/6.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Weiffenbach; Cameron K.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
Parent Case Text
This is a division of application Ser. No. 32,439, filed Apr. 27,
1970, now U.S. Pat. No. 3,677,797.
Claims
What is claimed is:
1. An iron or steel product having, on the surface thereof, a film
of a thickness of less than 1.mu. consisting essentially of nickel
and at least one oxide selected from the group consisting of oxides
of Cr, Mn and Zn with a coating of an organic resin paint on the
surface of said film.
2. An iron or steel product according to claim 1 wherein the
organic resin paint is an epoxy resin paint.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of making surface-treated steel
plates by thermodecomposing plating.
2. Description of the Prior Art
As is well known, tin-plated steel plates are primarily used for
producing cans. However, tin has certain drawbacks in that it is
expensive, it is not endurable at high temperatures, it is weak
against corrosion in the atmosphere and further it turns black,
depending on the contents of the can. Furthermore, tin is in such
short availability in the world, that its supply is unstable. As a
result of making researches on surface-treated steel plates, the
present inventors have discovered that in order to produce
surface-treated steel plates which are devoid of the above defects,
it is necessary to form a film on the surface of the steel plate,
which film is more stable than the steel plate to be plated. The
film formed herein is based on a technical idea different from that
of plating, such as tin-plating to electrochemically protect the
steel plate in a corrosive liquid.
Further, when using metal-plated surface-treated steel plates,
including tin-plated steel plates, as the material for making cans,
it is usual to coat the metal-plating layer with well known
lacquers of various kinds such as an epoxy resin series paint to
prevent the metal-plating layer from being corroded and the metal
ions from being formed by such contents in the can as, for example,
a beverage, liquor, oil or fat.
Therefore, a metal-plated surface-treated steel plate should
satisfy certain conditions. It should not only be high in
antirusting properties in the atmosphere, but also, when coated
with a lacquer and dipped in the above described corrosive liquid,
the lacquer coating film should not peel off, and, moreover, it
should not interfere with the can-manufacturing operations; for
instance, it should be easy to solder and mold.
To exemplify the peeling-off of such lacquer film, the case of an
Al- or Zn-plated steel plate coated with a lacquer will be
explained. When dipping said steel sheet in the above described
corrosive liquid, the corrosion of the Al- or Zn-plating layer by
said corrosive liquid proceeds faster than the corrosion of the
iron base material on account of an anodic protective action of Al
or Zn on the steel sheet, resulting in the peeling-off of the
lacquer film.
As opposed to the case of an Al- or Zn-plated steel plate, there
occurs no peeling-off of a lacquer from the surface of a Cr- or
Ni-plated steel plate when dipped in a corrosive liquid because Cr
or Ni is inherently high in antirusting properties and is more
stable than the iron base; consequently the lacquer adheres firmly
to the surface of the Cr- or Ni-plated steel plate. However,
because the plating layer is thick, this plating method is not
economical.
SUMMARY OF THE INVENTION
On the basis of such knowledge, as is described above, the present
inventors have developed a novel process for obtaining a
surface-treated steel plate high in anticorrosion by forming, on a
steel plate, a film more stable than the iron base.
An object of the present invention is to provide surface-treated
steel plates which are so high in anti-corrosiveness that they can
sufficiently serve in place of tin-plated steel plates. The
surface-treated steel plates are novel and economical and can be
used as a material for manufacturing tin-free cans. These plates
may also be used as materials for automobiles, various
constructions and toys.
In order to attain the object of the present invention, the
following methods are provided, which are characterized by the
following features: that is, a method for obtaining surface-treated
steel plates having excellent anticorrosiveness, wherein an aqueous
solution of nitrate and/or acetate of Ni is applied on the surface
of the steel plates, previously subjected to a surface-cleaning
treatment, and the surface treated steel plates are then heated in
a nonoxidative gas atmosphere, so as to cause a thermodecomposing
reaction, to thereby form a film containing metallic nickel on the
surface of the steel plate; a method for forming a further improved
film, that is, a method for obtaining surface-treated steel plates
having excellent anticorrosiveness wherein an aqueous solution of
nitrate and/or acetate of Ni with the addition of one or more
nitrates and acetates of Cr, Mn and Zn is applied on the surface of
steel plates, previously subjected to a surface-cleaning treatment,
and then heated in a nonoxidative gas atmosphere, so as to cause a
thermodecomposing reaction, to thereby form a film containing
metallic nickel and one or more of oxides of Cr, Mn and Zn on the
surface of the steel plates; and further a method for forming a
more excellent film, that is, a method for obtaining
surface-treated steel plates having particularly excellent
anticorrosiveness, wherein an aqueous solution of a nitrate and/or
acetate of Ni with the addition of one or more of nitrates and
acetate of Cr, Mn and Zn and with a further addition of a nitrate
and/or acetate of Al is applied on the surface of a steel plate,
previously subjected to a surface-cleaning treatment, and then
heating the thus-treated steel plates in a nonoxidative gas
atmosphere, so as to cause a thermodecomposing reaction, to thereby
form a film containing metallic nickel and one or more of oxides of
Cr, Mn, Zn and Al on the surface of the steel plates.
The present invention is particularly economical because it is
possible to utilize a heating cycle of annealing conditions for the
thermodecomposing reaction, and the method of the present invention
is therefore very high in practical value.
Moreover, the thus obtained treated film is not only excellent in
anticorrosive activity but is also very excellent in its paint
adhesiveness and mechanical workability. Therefore, the present
invention is particularly adapted as a method of making steel
plates for making cans.
The method of the present invention shall be detailed in the
following.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The essence of the present method is to form a very thin film of
metallic nickel on the surface of a steel plate by applying an
aqueous solution, for example, of nickel nitrate to coat the said
surface of the steel plate and then heating it in a reductive or
inert non-oxidative atmosphere so as to cause a thermodecomposing
reaction of the treating solution and the reduction (complete or
partial) of nickel nitrate to metallic nickel.
Nickel nitrate or nickel acetate, which is an essential component
of the treating aqueous solution of the present invention, may be
used individually or in admixture. However, Ni compounds
(particularly oxides) other than the aforementioned compounds
should be avoided, since they involve difficulties in forming films
of satisfactory anticorrosiveness, paint adhesiveness and
workability.
In the following, for the convenience of the explanation, the
aqueous solution containing a Ni-salt prepared as described above
shall be called a treating solution.
It is difficult to uniformly apply some of the treating solutions
of the present invention to coat steel plates. However, in such
case, an improvement can be obtained by adding a proper amount of a
surface active agent, such as a nonionic active agent. The
deposited amount of the treating solution differs remarkably,
depending on the method of coating the surface of the steel plates,
for example, by blowing a spray of the treating solution on the
surface of the steel plates, applying the treating solution with a
roller, or dipping the steel plate in the solution. The
concentration of the treating solution is difficult to uniformly
define but, if the effective quantitative range is to be defined in
relation to the viscosity of the solution or the uniformity of the
decomposing reaction, Ni ions are to be contained in an amount of
0.5 to 100 g./l. or preferably 1 to 20 g./l., the later described
Cr.sup.+.sup.+.sup.+ ions are present in amounts less than 20 g./l.
or preferably 10 g./l., Al ions are present in amounts less than 20
g./l. or preferably less than 10 g./l., Zn ions are present in
amounts less than 40 g./l. or preferably less than 10 g./l. and Mn
ions are present in amounts less than 20 g./l. or preferably less
than 10 g./l.
Further, in order to improve the characteristics of the treated
film, a nitrate or acetate of Mg, Ca or K may be added in an amount
of about 1 g./l.
It is wise to prevent, as much as possible, the pH of the treating
solution of the present invention from becoming excessively acidic
to avoid an exchanging reaction with Fe. Therefore, in industrial
practice, it is desirable to make the pH of the treating solution 3
to 4.
In regard to films which are heavily colored in their appearance
after being heat-treated, there is observed a tendency of these
films to reduce the adhesiveness of the lacquer and also to reduce
the adhesion of the film itself to the base. Therefore, it is
desirable to control the deposited amount of the film so that the
appearance after heat-treatment may have a transparency to such a
degree as to not substantially impair the luster of the cold-rolled
steel plate or to control the deposited film so that it has a light
tone to such a degree as to be barely recognizable with the naked
eye (that is, the metal thickness may be less than 1 .mu. or, if
possible, about 0.1 .mu. or less).
Now, in the method of the present invention, the above described
treating solution is applied and is then quickly heated to cause a
thermodecomposing reaction at a temperature of 200 to 750.degree.C.
in a furnace of a nonoxidative gas atmosphere such that it has, for
example, a H.sub.2 content of 2 to 20% and wherein the remaining
component is essentially N.sub.2 (as DX or NX gas) used as a
brightly annealing gas to form a strong metallic nickel film. When
the content of H.sub.2 in the gas atmosphere is less than 2%, the
Ni salt is so hard to reduce that there is formed an undesirable
film because the film containing metallic nickel becomes lusterless
and blackish. On the other hand, when the content of H.sub.2 is
more than 20%, there is a great economic loss. In addition, such a
high content of H.sub.2 is not desirable, particularly in the
method wherein salts of Al, Cr, Mn and Zn are added to a salt of
Ni, because the reduction of salts of these metals proceeds too far
with the result that such a metallic nickel-plated film containing
oxides of these metals, as is intended in the present invention,
can not be obtained.
The above described nonoxidative gas many contain a slight amount
of carbon dioxide, carbon monoxide or water. However, the heating
atmosphere must not be oxidative (i.e. contain oxygen) to such a
degree as to have an adverse influence on the reduction of the salt
of nickel to metallic nickel; otherwise the salt of nickel applied
to the surface of a steel plate may not be reduced to metallic
nickel to the required amount during the annealing time and may
remain as nickel oxide on the surface of the steel plate. The
latter effect would not be in keeping with the object of the
present invention.
When the heating temperature is less than 200.degree.C., no
effective thermodecomposition takes place. On the contrary, when it
is more than 750.degree.C., there are produced undesirable results,
such that all the metallic nickel produced by the
thermodecomposition, will alloy with the iron base to form a hard
film which is not only low in adhesiveness but also low in the
anticorrosiveness, and further even impair the mechanical
properties of the steel plate itself.
In the foregoing, an example of applying a treating solution
composed of only a Ni-salt has been explained. The surface film
obtained by this method is thought to be a two-layer film high in
anticorrosiveness, consisting of an Fe-Ni alloy in the lower layer
and metallic nickel in the upper layer. As a result of making
further investigations, however, the present inventors have
succeeded in developing an improved method of forming, on the
surface of a steel plate, a film which is more excellent than the
above described film. This film is thought to be formed of two
layers, wherein the lower layer is made of an Fe-Ni alloy and the
upper layer is a mixture mainly composed of oxides of Cr, Mn and Zn
and metallic nickel.
The improved method involves applying to the steel sheet, an
aqueous solution (which shall be called a treating solution with
additive for the convenience of the explanation hereinafter)
obtained by adding one or more of nitrates and acetates of Cr, Mn
and Zn to a nitrate and/or acetate of Ni and heating the
thus-coated steel sheet in a nonoxidative gas atmosphere furnace to
form a film consisting of one or more of oxides of Cr, Mn and Zn,
and metallic nickel. The above-mentioned treating solution with
additive may be prepared by adding one or more members consisting
of carbonates, oxalates and hydroxides of Cr, Mn and Zn to an
aqueous solution of Ni nitrate and/or acetate.
In the foregoing, there have been shown examples of dissolving a
nitrate or acetate of Ni and carbonates, oxalates, hydroxides and
oxides of Cr, Mn and Zn in an aqueous solution of nitric acid
and/or acetic acid. However, the present invention is not limited
to them except for the Ni salts. Any salts of Cr, Mn and Zn may be
used, if they leave no anion in an aqueous solution of nitric acid
or acetic acid when dissolved in such solution.
As to the method of applying said treating solution with additive,
any of the methods adopted when applying the above-mentioned
treating solution may be used, such as the spraying method, the
roller-coating method and the dipping method. If necessary, also a
surface active agent may be further added.
Also, the heating can be carried out under exactly the same
conditions and in the same manner, that is, in a temperature range
of 200 to 750.degree.C. in a furnace of a nonoxidative gas
atmosphere in which, for example, the H.sub.2 content is 2 to 20%
and the rest is mostly N.sub.2. However, the thus obtained film is
higher in anticorrosiveness than in the case of the above mentioned
treating solution composed of the Ni salt only.
As a result of making further investigations, the present inventors
have discovered that when an Al salt is further added to the
above-mentioned treating solution with additive, a film having more
excellent anticorrosiveness and workability can be obtained.
For example, when a treating solution prepared by adding an Al salt
to the above-mentioned treating solution with additive (which
contains one or more salts of Cr, Mn and Zn in addition to Ni) is
subjected to the thermodecomposition in a temperature range of from
200 to 750.degree.C. in a furnace of a nonoxidative gas atmosphere
and a H.sub.2 content is 2 to 20%, there can be formed on the
surface of a steel plate a very thin film. This film has proven to
be all the more improved in anticorrosiveness and workability, as
illustrated in the following examples.
As will be understood from the foregoing, the present invention
provides for a method of inexpensively producing a steel plate
having a strong inactive film on the surface thereof, which surface
is just like that of stainless steel. The thus-produced steel
sheets are particularly suitable as a material for manufacturing
cans therefrom because they are high in anticorrosiveness and
excellent in paint adhesiveness.
The specific examples of the present invention shall be detailed
below.
EXAMPLE 1
A cold-rolled steel plate of a thickness of 0.26mm., which had been
cold-worked by a well known method, that is, by using a continous
strip rolling apparatus, but had not yet been annealed, was
subjected to a well known pretreatment, for example, such surface
adjustments as alkali-defatting and sulfuric acid-pickling, was
dipped in an aqueous solution of nickel nitrate or nickel acetate
so that the nickel salt might be deposited on the surface, and was
immediately thereupon heated at a temperature of 600.degree.C. in
an annealing gas atmosphere of a H.sub.2 content of 6% and the rest
being N.sub.2, so as to effect a strain-removing annealing, and at
the same time to form a nickel film, and was then rolled for
refining at reduction rate of 1%. A comparison of the performances
of this steel was made, as mentioned below, in respect to the
antirusting properties, corrosion resistance below the coating film
and paint adhesiveness. The samples Nos. 1, 2 and 3 in the
below-mentioned performance test comparison table are steel plates
having a film composed of metallic nickel, all prepared by the
above-mentioned method. On the other hand, a referential sample No.
13 in the same table was prepared by subjecting a steel to a
cold-rolling with the above-mentioned continuous strip rolling
apparatus, thereupon to alkali-defatting and pickling and then to
an annealing in the above-mentioned gas atmosphere (this
referential steel shall be called a nontreated steel plate
hereinafter for the convenience of the explanation).
In the rusting test, by an indoor exposure, the non-treated steel
plate rusted within one month, while samples Nos. 1, 2 and 3 did
not rust in 3 to 5 months in the same indoor exposure. Further, in
the corrosion test, in which samples were dipped in a carbonic acid
beverage after being coated with an epoxy resin series paint,
samples Nos. 1, 2 and 3 showed results much superior to the
nontreated sample in anticorrosiveness, but somewhat inferior in
paint adhesiveness.
__________________________________________________________________________
Performance test comparison table
__________________________________________________________________________
Performance tests Sample Treating solution composition Treating
process 1) Antirusting 2) Corrosion 3) Paint ad- No. property
resistance hesiveness the coating
__________________________________________________________________________
film 1 Nickel nitrate (60 g./l.) .degree. Dip-coating 5.0 3 4 2
Nickel acetate (30 g./l.) .degree. Heating atmos- 4.0 3 4 phere
H.sub.2 : 6% 3 Nickel nitrate (10 g./l.)+ N.sub.2 : rest 2.5 2 4
nickel acetate (10 g./l.) .degree. Heating temper- ature:
600.degree.C. 4 Nickel nitrate (20 g./l.)+ .degree. Roller-coating
7.0 4 5 chromium acetate (10 g./l.) .degree. Heating atmos- 5
Nickel acetate (20 g./l.)+ phere manganese nitrate (10 g./l.)
H.sub.2 : 10% 6.0 3 4 N.sub. 2 : rest 6 Nickel nitrate (20 g./l.)+
.degree. Heating temper- 4.5 3 4 zinc nitrate (10 g./l.) ature:
600.degree.C. 7 Nickel acetate (20 g./l.)+ - chromium acetate (5
g./l.)+ 9.5 5 5 manganese nitrate (5 g./l.) 8 Nickel nitrate (20
g./l.)+ manganese nitrate (5 g./l.)+ 8.5 4 3 zinc nitrate (5 g./l.)
9 Nickel nitrate (20 g./l.)+ .degree. Dip-coating 11.5 5 5 aluminum
nitrate (5 g./l.)+ chromium acetate (5 g./l.) .degree. Heating
atmos- phere 10 Nickel nitrate (20 g./l.)+ H.sub.2 : 6% aluminum
nitrate (5 g./l.)+ N.sub.2 : rest 10.0 5 5 zinc nitrate (5 g./l.)
.degree. Heating temper- ature: 250.degree.C. 11 Nickel acetate (20
g./l.)+ aluminum nitrate (5 g./l.)+ 9.0 5 5 zinc nitrate (5 g./l.)
12 Nickel acetate (10 g./l.)+ aluminum nitrate (5 g./l.)+ chromium
nitrate (5 g./l.)+ 12.5 5 5 manganese nitrate (5 g./l.) 13
(nontreated steel plate) 0.5 1 5
__________________________________________________________________________
EXAMPLE 2
The same cold-rolled steel plate as in Example 1 was defatted with
an alkali and pickled with sulfuric acid, was then coated with a
treating solution prepared by adding one or more of chromium
acetate, manganese nitrate and zinc nitrate into an aqueous
solution of nickel acetate or nickel nitrate by using a roller and
was then immediately heated at a temperature of 600.degree.C. in a
brightly annealing gas atmosphere of a H.sub.2 content of 10%, the
rest being N.sub.2, to form a film. The samples Nos. 4 to 8 in the
above-mentioned performance test comparison table were steel plates
prepared by the above-mentioned process. It is apparent that the
films obtained by applying a treating solution containing one or
more salts of Cr, Mn and Zn in addition to a Ni salt shown
properties which are performances more excellent than that of the
film prepared in Example 1. That is, they showed no rusting in 4 to
10 months in the rusting test by indoor exposure and were very high
in their corrosion resistance below the coating film when placed in
a carbonic acid beverage, after being coated with a lacquer.
EXAMPLE 3
A cold-rolled steel plate of a thickness of 0.26mm. which had been
cold-worked by a well known method, for example, by using a
continuous strip rolling apparatus, thereafter alkali-defatted,
sulfuric acid-pickled and then annealed in a reductive atmosphere
was once more subjected to an alkali-defatting and sulfuric
acid-pickling surface treatment, and was then dip-coated with a
treating solution prepared by adding one or more of chromium
acetate, manganese nitrate and zinc nitrate into an aqueous
solution of a mixture of nickel nitrate and aluminum nitrate and
was then immediately heated at a temperature of 250.degree.C. in a
heated gas atmosphere of a H.sub.2 content of 6%, the rest being
N.sub.2, to form a film.
The samples Nos. 9 to 12 in the above-mentioned performance test
comparison table which correspond to this example, did not rust in
9 to 13 months in a rusting test by indoor exposure, were not
corroded at all below the lacquer-coated film, when placed in a
carbonic acid beverage, after being coated with a lacquer and were
high also in paint adhesiveness.
In all the Examples 1, 2 and 3, the heating time was very short,
amounting to several seconds, though there was a slight difference
according to the temperature in the range of 200 to
750.degree.C.
The numerals in the above-mentioned performance test comparison
table are defined as follows:
1. Antirusting property
The period until a rust recognizable by observation with the naked
eye was generated on the surface of the steel plate by the indoor
exposure test was represented by the number of months.
2. Corrosion resistance below the coating film
The steel plate was coated with an epoxy resin series lacquer, and
then scratched, so that the scratch mark had a width of 0.1mm. and
was dipped for one month in a cola series carbonic acid beverage,
kept at such fixed temperature as 38.degree.C. in the example, and
then the degree of corrosion below the coating film in the
scratched part was observed. The numerals in the table were
defined, as follows, by dividing the evaluations into five
grades:
5--When no coating film peeling was recognized at all.
4--When a coating film peeling of about 0.1 to 0.2mm. was
recognized.
3--When a coating film peeling of about 0.2 to 0.4mm. was
recognized.
2--When a coating film peeling of about 0.4 to 0.8mm. was
recognized.
1--When a coating film peeling of about 0.8 to 2.0mm. was
recognized.
3. Paint adhesiveness
A lacquer was applied and was then bonded with a binder; then the
tensile strength was measured and was evaluated by making the
maximum value 5 and the minimum value 1 as the scale of lacquer
adhesiveness.
* * * * *