JP2006016676A - Surface-treated steel plate, surface treatment chemical, and surface treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-treated steel plate having a film layer capable of reducing the environmental load and having excellent rust-prevention, a surface treatment chemical to form the film layer, and a surface treatment method of the surface-treated steel plate with the film layer formed thereon. <P>SOLUTION: In the surface-treated steel plate, a film layer containing at least one kind of salt consisting of (1) anions having stronger basicity than zincate ions or (2) anions of the molecular weights of ≥ 1,000, (3) metal cations having weaker acidity than zinc ions with dissociated anions of hydroxides having stronger basicity than zincate ions, and more basic than zinc ions, or (4) cations having primary amino group with the molecular weight of ≥ 1,000 is formed on the surface of a galvanized steel plate. Deposition of the film layer of the surface-treated steel plate is ≥ 0.1/n mmol/m<SP>2</SP>in terms of anion or cation where (n) denotes the charge of the cations to constitute the salt. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface-treated steel sheet having a coating layer with excellent corrosion resistance formed on the surface, a surface-treating agent that can be used when forming the film layer, and a surface treatment method for the surface-treated steel sheet.

  Since zinc has a sacrificial anticorrosive effect on iron, it is possible to improve the corrosion resistance of steel products by applying zinc-based plating to the steel material surface. This sacrificial anticorrosive effect is known as an important factor that determines the corrosion resistance of steel products. On the other hand, when the zinc-based plated steel sheet with the zinc-based plating applied to the steel sheet surface is oxidized with time in addition to sacrificial dissolution, white rust is generated on the plated surface. Since the appearance of white rusted products deteriorates and the product value decreases, it is desired to suppress the occurrence of white rust.

  Conventionally, chromate treatment has been widely used as a surface treatment to suppress white rust, and the chromate film formed on the steel sheet surface by chromate treatment contains hexavalent chromium. Since hexavalent chromium has a higher potential than oxygen in the hexavalent / trivalent oxidation-reduction reaction, trivalent chromium is generated in preference to the oxygen reduction reaction in the cathodic reaction in a corrosive environment. It is known that the anticorrosion film formed by the trivalent chromium produced in this way has a dense structure and exhibits a strong rust prevention ability.

  However, since hexavalent chromium is a harmful substance harmful to the human body, problems with environmental load have been pointed out. Therefore, establishment of chromium-free surface treatment technology that does not contain chromium is required.

Several chromium-free surface treatment techniques have been studied so far, for example, a technique using an oxide film formation type corrosion inhibition mechanism, a technique using an adsorption film formation type corrosion inhibition mechanism, or a precipitation formation type corrosion. Examples include a technique using a suppression mechanism.
The technique using the oxide film formation type corrosion inhibition mechanism is a film processing technique using a higher-order oxidation state of a transition element such as vanadic acid, tungstic acid, or molybdic acid. A surface treatment technique using a high-order oxidation state is disclosed.
Moreover, the technique using the adsorption film formation type corrosion inhibition mechanism forms an anticorrosion film having a strong chemical adsorption force by donating electrons to the vacant d orbital of the transition metal in a corrosive environment with a water-soluble inhibitor. It is a film processing technology.
On the other hand, the technique using the precipitation formation type corrosion inhibition mechanism is a technique for inhibiting corrosion by forming a hardly soluble salt that causes polarization or slight corrosion on the plating surface in a corrosive environment. For example, zinc phosphate treatment, which is a known technique, is a method of forming a film using this mechanism, and phosphate ions can be used as precipitation-type inhibitors. In addition, Patent Document 2, Patent Document 3, and Patent Document 4 disclose surface treatment techniques using this mechanism.
JP 2001-170557 A Japanese Patent Laid-Open No. 9-57188 Japanese Patent Laid-Open No. 10-147890 JP 2001-26886 A

  However, the technique using the oxide film formation type corrosion inhibiting mechanism disclosed in Patent Document 1 has a problem that it cannot solve the problem with respect to the environmental load because it uses a component having a strong oxidizing power.

  In addition, Zn, Al, Mg, etc., which are plating components of zinc-based plated steel sheets, have no d-orbital space, so only an adsorption force of the level of physical adsorption can be obtained, and technology using an adsorption film formation type corrosion inhibition mechanism is sufficient. There is a problem that the corrosion suppression of the adsorbing film forming type cannot be expressed.

  In addition, in the technology using the precipitation formation type corrosion inhibition mechanism disclosed in Patent Literature 2, Patent Literature 3, and Patent Literature 4, the glassy coating obtained by these technologies is in the process of coating formation. Since the sol (Si—OH) is changed to the gel (Si—O—Si), there is a problem that it is difficult to exhibit sufficient rust prevention performance.

  Therefore, the present invention is capable of reducing the environmental burden, and is a surface-treated steel sheet on which a film layer having good rust prevention properties is formed, and a surface treatment capable of forming the film layer. It is an object of the present invention to provide a drug and a surface treatment method for a surface-treated steel sheet on which the coating layer is formed.

The inventors of the present invention have focused on a precipitation-type corrosion inhibition mechanism that has a high possibility of utilizing harmless substances, and studied a precipitation-type inhibitor effective for rust prevention in a neutral salt damage environment. This research has been made with particular attention to the fact that zinc is an amphoteric metal (a metal that dissolves as an anion in an alkaline aqueous solution while dissolving as an anion in an acidic aqueous solution).
Zn ²⁺ + 2H ₂ O⇔Zn (OH) ₂ + 2H ⁺ (Formula 1)
Zn (OH) ₂ ⇔ HZnO ₂ ⁻ + H ⁺ (Formula 2)
Zn ²⁺ + 2H ₂ O⇔HZnO ₂ ⁻ + 3H ⁺ (formula 3)
Formula 1 is a formula that expresses the base dissociation equilibrium of zinc hydroxide in a form in which zinc ions become proton donors (Bronsted acids). Further, Formula 2 is a formula that expresses the acid dissociation equilibrium of zinc hydroxide in a form in which the zincate ion HZnO ₂ ⁻ becomes a proton acceptor (Bronsted base). On the other hand, Expression 3 is an expression obtained by “Expression 1 + Expression 2”.

  Inhibitors effective in rust prevention are corrosion resistant precipitates before the base material is corroded to produce corrosion products (eg, zinc oxide or zinc basic salts such as zinc hydroxide in Formula 1 above). It is desirable to have a property of forming a film (for example, a precipitated film containing a hardly soluble salt). Such properties can be considered by Bronsted's acid / base theory. Therefore, the present inventors can determine the presence or absence of the rust preventive effect of the inhibitor based on the strength and weakness relationship between the cation and anion constituting the salt as the inhibitor and the zinc ion and the zincate ion as an acid / base. I made a temporary construction that I could do. And as a result of advancing research on the rust prevention properties of inhibitors based on this hypothesis, the following knowledge has been obtained.

First, it was found that an anionic species (hereinafter referred to as “strongly basic anionic species”) having a stronger basicity than a zincate ion has an antirust effect. Such an anion has the property of forming a precipitate film with a hardly soluble salt in preference to the basic salt, which is a corrosion product, with zinc ions generated in a corrosive environment. It is thought that it is expressed.
Secondly, it has been found that the strongly basic anionic species exhibits rust prevention properties by forming a salt composed of the anionic species and a cationic species that is weaker acidic than the zinc ion. This is thought to be because the strongly basic anion species that formed a salt with a cation that is more acidic than zinc ions loses its reactivity with zinc.
Third, a cation species having a property that is weaker than zinc ion as a cation, such as magnesium ion and calcium ion, and a property that is more basic than zincate ion as an acid dissociation anion of hydroxide ( Hereinafter, it has been found that a salt composed of “amphoteric cation species”) and the above strongly basic anion species is particularly effective as a precipitation-type inhibitor. The salt constituted in this way is considered to be because the anionic component has a property of forming a precipitate film as a zinc salt while the cation component also has a property of forming a precipitate film as a basic salt.
Fourth, in addition to the salt composed of the above strongly basic anion species and amphoteric cation species, a salt composed of a polymer anion species having a molecular weight of 1000 or more and an amphoteric cation species, strongly basic anion species And a salt composed of a polymeric cation species having a molecular weight of 1000 or more, and a salt composed of a polymer anion species having a molecular weight of 1000 or more and a polymer cation species having a molecular weight of 1000 or more. It was found that sex was expressed.

The present invention has been made based on the above findings.
The present invention will be described below.

1st this invention is a membrane | film | coat layer containing at least 1 or more types of salt comprised from the anion which satisfy | fills the conditions which satisfy | fill the conditions of (1) or (2), and the conditions of (3) or (4). Is a surface-treated steel sheet provided on the surface of a galvanized steel sheet, and when the charge of the cation constituting the salt is n, the salt contains 0.1 / n mmol / m ² or more in terms of cation. It is a surface-treated steel sheet characterized by being made.
(1) Anion having basicity stronger than that of zincate ion (2) Anion having a molecular weight of 1000 or more (3) It has weaker acidity than zinc ion as a cation, and the acid dissociation anion of hydroxide is stronger than zincate ion Metal cation having basicity and being baser than zinc in the electrochemical series (4) Cation having a primary amino group having a molecular weight of 1000 or more

  According to the first aspect of the present invention, it is possible to provide a surface-treated steel sheet on which a coating layer having a good antirust property can be formed and the environmental load can be reduced.

  In the first aspect of the present invention, the cation constituting the salt is preferably at least one selected from magnesium ion, calcium ion, strontium ion, or polyethyleneimine.

  Furthermore, in the first aspect of the present invention, the anion constituting the salt is preferably at least one selected from silicate ions, phosphate ions, or polyacrylic acid.

  By forming a salt using the cation and / or anion selected in this way, a surface-treated steel sheet having a coating layer that can improve versatility as an industrial material can be provided.

  In addition, in the first aspect of the present invention, the salt preferably contains silicate ions as anions and polyethyleneimine as cations.

  By adopting such a configuration, it is possible to efficiently exhibit rust prevention, substance permeation suppression function and adhesion, and it is possible to express good rust prevention performance with a small amount of adhesion. Furthermore, it is possible to provide a surface-treated steel sheet in which a coating layer excellent in balance with other performances required for the surface-treated steel sheet such as weldability is formed.

  The second present invention is a surface treatment agent comprising a silicate-based aqueous solution containing polyethyleneimine, wherein the ratio X / Y between the Si equivalent molar concentration X of silicate and the imino group equivalent molar concentration Y of polyethyleneimine is 0. It is a surface treatment agent characterized by being not less than 5 and less than 1.0.

  According to the second aspect of the present invention, it is possible to provide a low environmental load type surface treatment agent capable of forming a coating layer having a good antirust property on the surface of a zinc-based plated steel sheet.

  In the second aspect of the present invention, the ratio X / Y of the Si equivalent molar concentration X of silicate to the imino group equivalent molar concentration Y of polyethyleneimine in the surface treatment agent further containing a fluoro compound and a silane coupling agent 0.5 to less than 1.0, the ratio Z / X of the molar concentration Z of the fluoro compound to the molar concentration X in terms of Si is 0.1 or less, and 1 mol% of the imino group in the polyethyleneimine It is preferable that 50 mol% or less is previously treated with a silane coupling agent.

  By adopting such a configuration as the second aspect of the present invention, the surface of the zinc-based plated steel sheet can efficiently exhibit rust prevention, substance permeation suppression function and adhesion, and is good with a small amount of adhesion. A low environmental load surface treatment that can exhibit excellent anti-corrosion performance and can form a film layer with excellent balance with other properties required for surface-treated steel sheets such as weldability. Can provide drugs.

  3rd this invention is a surface treatment steel plate characterized by the surface of the zinc-plated steel plate being processed by the surface treatment chemical | medical agent concerning 2nd this invention.

  According to the third aspect of the present invention, it is possible to reduce the environmental load on the surface of the zinc-based plated steel sheet, and to exhibit good rust prevention, substance permeation suppression function and adhesion with a small amount of adhesion. It is possible to easily provide a surface-treated steel sheet in which a film layer excellent in balance with other performances required for the surface-treated steel sheet such as weldability is formed.

  4th this invention applies the surface treatment chemical | medical agent concerning 2nd this invention to the surface of a zinc-plated steel plate, It dries without washing with water the zinc-plated steel plate coated with the surface treatment agent, This is a surface treatment method for a surface-treated steel sheet.

  According to 4th this invention, the surface treatment method of the surface treatment steel plate which can reduce environmental impact can be provided.

  According to the present invention, it is possible to reduce the environmental load, and the surface-treated steel sheet on which a coating layer having good rust prevention properties is formed, and the surface treatment capable of forming the coating layer. It is possible to provide a surface treatment method for a surface-treated steel sheet on which a drug and the coating layer are formed.

Hereinafter, the present invention will be described in more detail while describing embodiments of the present invention.
1. 1. Surface-treated steel sheet 1-1. Zinc-based plated steel sheet As the zinc-based plated steel sheet on which the coating layer is provided in the present invention, a pure zinc-plated steel sheet and a zinc alloy-plated steel sheet can be applied. In the case of zinc alloy plating, for example, even when alloy elements such as aluminum, magnesium, nickel, iron, and silicon are contained, zinc alloy plating in which the mass of metallic zinc occupies about 40% or more in the plating film A steel plate can be suitably used. Specific steel sheets to which the present invention can be applied include electrogalvanized steel sheets, hot dip galvanized steel sheets, alloyed hot dip galvanized steel sheets, 5% aluminum-zinc alloy hot dip steel sheets, 3-12% aluminum-2 ~ Examples thereof include 4% magnesium-zinc alloy hot-dip steel sheet, 55% aluminum-zinc alloy hot-dip steel sheet, 10% nickel-zinc alloy electroplated steel sheet, and the like. A practical plating adhesion amount that can be adhered to a steel sheet in a continuous plating line is generally considered to be about 10 to 300 g / m ^{2 in} terms of the adhesion amount per one side, but plating that can exhibit the effects of the present invention. The adhesion amount is not limited to the above adhesion amount.

1-2. Film layer 1-2-1. Salt (precipitation inhibitor)
The salt used in the present invention (hereinafter sometimes referred to as “precipitation inhibitor”) needs to be present as a poorly soluble salt in the coating layer. Since the salt in the coating layer is solid, the anion and cation constituting the salt may not exist in a so-called ionic state. However, since all the salts in the coating layer are ion-binding substances derived from ions, the atomic group on the side attracting electrons is described as an “anion component” and the electrons are separated. The atomic group on the other side is described as “cationic component”.

a) Anion component The anion species constituting the precipitation-type inhibitor in the present invention is “(1) an anion having a stronger basicity than a zincate ion” or “(2) a polymer having a molecular weight of 1000 or more. It is necessary to be an anion.

a-1) Anion component satisfying requirement (1) According to the definition of Bronsted,
A ⁻ + H ⁺ ⇔HA (Formula 4)
, The anion A ⁻ is a base that accepts the proton H ⁺ , and the strength as a base is generally indicated by the base dissociation constant K _b (Equation 5).
[HA] / {[A ⁻ ] [H ⁺ ]} = K _b (Formula 5)

On the other hand, an acid-dissociating anion of an amphoteric hydroxide such as the zincate ion HZnO ₂ ^— (hereinafter referred to as “H _n-1 MO _n ⁻ ”) is a solid hydroxide as a free acid. Does not exert mass action (Formula 2). Therefore, the present inventors considered a base dissociation equilibrium (Equation 6) in consideration of both the base dissociation cation and the acid dissociation anion under a dilute condition where the hydroxide does not reach a saturation concentration, and the equilibrium constant K of the equilibrium is considered. _b ′ (formula 7) is proposed as an indicator of anions that can form the coating layer in the present invention.
H _n-1 MO _n ⁻ + (n + 1) H ⁺ Ｍ M ^{n +} + nH ₂ O (Formula 6)
{[M ^{n +} ] ^{1 / n + 1} [H ₂ O] ^{n / n + 1} } / {[H _n-1 MO _n ⁻ ] ^{1 / n + 1} [H ⁺ ]}
= (K _spb / K _spa · K _w ⁿ ) ^{1 / n + 1} = K _b ′ (Expression 7)
However, K _spa = [H _n-1 MO _n ⁻ ] [H ⁺ ], K _spb = [M ^{n +} ] [OH ⁻ ] ⁿ ,
K _w = [H ⁺ ] [OH ⁻ ] = 10 ⁻¹⁴
And

Solubility product of the amorphous hydroxide _zinc, K ^{spa = 10 -15.4 _{and,, K spb = 10 -15.74 (}} M.Pourvaix, Atras of Electrochemical Equilibria in Aqueous Solutions, Pergamon, 1966, No. 411 pages) in Therefore, the value of pK _b ′ (= −log K _b ′) of the zincate ion HZnO ₂ ^— is −9.2. Therefore, an anionic species having a pK _b ′ value of less than −9.2 exhibits stronger basicity than a zincate ion, and thus the anionic species is effective as an anionic component constituting the precipitation-type inhibitor.

Specific examples of the anionic component exhibiting such properties include PO ₄ ³⁻ , or B (OH) ₃ , Si (OH) ₄ , Ti (OH) ₄ , Zr (OH) ₄ , Cr (OH) ₃ , and And acid dissociation anions of hydroxides such as Mn (OH) ₄ .

a-2) Anion component satisfying requirement (2) In addition to the anion component satisfying the above requirement (1), the anion constituting the salt in the coating layer in the present invention is a polymer anion having a molecular weight of 1000 or more. Can do. Specific examples of such anions include polyacrylic acid or carbonate anions associated with polyacrylic acid copolymer resins, acrylic resins, urethane resins, and the like. The molecular weight of the polymer anion is preferably 1000 or more from the viewpoint that rust prevention can be exhibited. Moreover, when using polyacrylic acid, it is preferable that the said molecular weight is 25000 or less from a viewpoint that the coating on a steel plate can be performed easily. By using such a polymer anion, the rust prevention property is improved even if a part of the functional group in the same molecule of the polymer is dissolved. It is thought that this is because the functional group in the portion maintains close contact with the surface of the plated steel sheet to develop water resistance.

  As described above, when a polymer anion is used as an anion constituting a salt in the film, the water adhesion resistance is improved by treating 1 to 50 mol% of the functional group in the polymer anion with a silane coupling agent. It is preferably used as an improved polymeric anion. The functional group to be treated with the silane coupling agent is preferably 1 to 50 mol%, more preferably 5 to 10 mol from the viewpoint of improving the water resistance of the polymer anion and maintaining rust prevention. %.

  Among the anion components satisfying the above requirement (1) or (2), the anion constituting the salt in the coating layer in the present invention is a silica from the viewpoint of the effect of reducing environmental burden and high versatility as an industrial material. Acid ions, phosphate ions, and / or polyacrylate ions are preferable, and silicate ions are more preferable.

b) Cationic component The cation species constituting the precipitation-type inhibitor in the present invention has “(3) acidity weaker than zinc ion as cation and acid dissociation anion of hydroxide stronger basic than zincate ion” In addition, it is necessary to be “a metal cation that is more base than zinc in the electrochemical series” or “(4) a cation having a primary amino group with a molecular weight of 1000 or more”.

b-1) Cationic component satisfying requirement (3) According to the definition of Bronsted,
M ^{n +} + nH ₂ O Ｍ M (OH) _n + nH ⁺ (Formula 8)
The cation M ^{n +} is an acid that donates a proton H ⁺ . Therefore, the present inventors propose an acid dissociation constant K _a (Equation 9) as an index representing the strength of metal ions as an acid.
{[M (OH) _n ] ^{1 / n} [H ⁺ ]} / {[M ^{n +} ] ^{1 / n} [H ₂ O]}
^{_{= K w / K spb 1 /}} n = K a ( Equation 9)
_Here, K w ^{= 10 -14,} and, from the solubility product _K spb ^{= 10 -15.74} zinc hydroxide, the value of the _{pK a} (= _-logK a) zinc ions ^{Zn 2+} becomes 6.13. Thus, the cation is a weak acid than zinc ions as the metal ions, the value of the pK _a may if it exceeds 6.13. Moreover, as shown in a-1), in order to be stronger basic than the zincate ion as the acid dissociation anion of the hydroxide, the value of pK _b ′ should be less than −9.2. That is, the cation component satisfying the requirement (3) is a cation having a pK _a value exceeding 6.13 and a pK _b ′ value being less than −9.2.
Specific examples of metal cations that exhibit such properties and are more base than zinc in the electrochemical series include metal ions such as Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , V ²⁺ , Mn ²⁺ , and the like. Can be mentioned. These cationic components are preferable because they do not deprive the reactivity of the anionic components satisfying the above requirements and have a rust preventive effect.

b-2) Cationic component satisfying the requirement (4) In addition to the cationic component satisfying the above requirement (3), the cation constituting the salt in the coating layer in the present invention is a polymer cation having a molecular weight of 1000 or more. Can do. Specific examples of such cations include polyethyleneimine. Polyethyleneimine is an aqueous polymer in which an imino group as a functional group exists as a cation in water. The molecular weight of the polymer cation is preferably 1000 or more from the viewpoint that rust prevention can be exhibited. The use of such a polymer cation improves rust prevention even if a part of the functional group in the same molecule of the polymer is dissolved. It is thought that this is because the functional group in the portion maintains close contact with the surface of the plated steel sheet to develop water resistance.

  Thus, when using a polymer cation as a cation component constituting a salt in the film, water-resistant adhesion is obtained by treating 1 to 50 mol% of the functional group in the polymer cation with a silane coupling agent. It is preferably used as a polymer cation having improved The functional group to be treated with the silane coupling agent is preferably 1 to 50 mol%, more preferably 5 to 10 mol from the viewpoint of improving the water resistance of the polymer cation and maintaining the antirust property. %.

  Among the cation components satisfying the above requirement (3) or (4), the cation constituting the salt in the coating layer in the present invention is magnesium from the viewpoint of the effect of reducing the environmental load and high versatility as an industrial material. Ion, calcium ion, strontium ion, and / or polyethyleneimine are preferable, and polyethyleneimine is more preferable.

c) Combination of anion and cation By allowing a salt composed of an anion satisfying the requirement of a) and a cation satisfying the requirement of b) to be present in the coating layer, it becomes possible to develop rust prevention properties. Become. Here, the form of the salt present in the coating layer is not limited to a simple salt composed of a pair of anions and cations, for example, between the same type of molecules and / or between different types of molecules via a polyvalent metal cation. In such a form, an intermolecular bond may be formed (ionomer). In addition, even in the case of an anion and / or cation that does not satisfy the above requirements in the surface treatment agent for treating the surface of a zinc-based plated steel sheet, for example, it is crosslinked and polymerized in the process of forming a coating layer on the steel sheet surface. Like the anion and / or cation, a salt composed of the anion and / or cation that satisfies the above requirements may be present in the formed film layer.

d) Combined use with other types of inhibitors By using a transition metal in a higher-order oxidation number state classified as an oxide film-forming inhibitor in combination with the precipitation-type inhibitor, it is possible to improve rust prevention. Specific examples of such oxide film-forming inhibitors include vanadate, molybdate, tungstenate and the like. However, as described above, the use of these substances having a strong oxidizing power is disadvantageous to the problem with respect to the environmental load, and therefore the amount of use should be minimized.

e) Adhesion amount of the film layer The adhesion amount of the film layer in the present invention is 0 in terms of salt when the charge of the cation constituting the salt satisfying the above requirement is n, from the viewpoint of expressing rust prevention. 1 / n (mmol / m ² ) or more. On the other hand, from the viewpoints of the weldability, appearance, manufacturing cost, and the like of the steel sheet, the coating amount of the coating layer is preferably 10 / n (mmol / m ² ) or less in terms of the salt. In addition, it is preferable that it is 100-5000 (mg / m < ² >) as the adhesion amount of the film layer in total which added the binder component and lubricating component mentioned later.

1-2-2. Binder component The coating layer in the present invention preferably contains a binder component. By containing a binder component, the adhesion strength when fixing a salt that satisfies the above requirements in the coating layer, the denseness of the coating layer required to obtain a barrier rust-preventing effect that suppresses substance permeation, Fingerprint resistance, top coat adhesion, and the like can be improved.
Specific examples of the technology that can be used as the binder component include silicate-based, titanate-based, zirconate-based salts, or glassy films obtained by the sol-gel method of alkoxides, or glassy forms thus obtained. Films that combine organic components with the film to improve film properties, topcoat adhesion, and fingerprint resistance, or acrylic, urethane, or epoxy resin films represented by water-based paints, etc. Known techniques can be mentioned.

a) Application of Sol-Gel Method Among the above-mentioned known techniques, the binder component is a glassy film obtained by the sol-gel method, particularly from the viewpoint of rust prevention, adhesion, substance permeation suppression, and water resistance. A film in which an organic component is combined (hereinafter referred to as “organic film”) is preferable. By making an organic film in which an organic component is combined with a glassy film, it becomes possible to reduce the stress of the glassy film, and to make the film capable of reducing the internal stress and peeling of the film. Can do. The above substances exemplified as the components of the glassy film combined with the organic component are all strong bases as the acid dissociation anion of the hydroxide, so these substances are in the film layer having excellent rust prevention properties. It can also be utilized as an anion constituting the precipitation type inhibitor.
Here, the sol refers to a state in which a salt or alkoxide is hydrolyzed to take in water as a solvent to form a network, while the gel refers to a state in which the network is polymerized by dehydration condensation.

  Further, in the vicinity of the interface between the coating layer according to the present invention and the surface of the zinc-based plated steel sheet, the organic film and zinc ions supplied in the form of acid dissociation anions of hydroxide from the surface of the plated steel sheet are hardly soluble. An adhesion layer consisting of a salt form is formed. Therefore, the organic film has good adhesion.

  Furthermore, the organic film is excellent in substance permeation suppression and water resistance. In the film formation process from the sol to the gel, the gel part eliminates moisture in the film and causes covalent polymerisation, while the sol part takes in moisture in the film to form a network. It is thought that this is because the behavior is different from that of bulk water.

b) Application of precipitation-type inhibitor Except when the anionic component and / or cation component of the precipitation-type inhibitor are selected from aqueous polymers, the precipitation-type inhibitor is often a solid that is hardly soluble in water. When using a sparingly soluble salt in the wet process of the manufacturing method described later, the salt particle size is 1/10 or less of the designed film thickness of the coating layer and then mixed with the binder component. It is preferable to make it. The amount of the salt to be mixed with the binder component is that the binder component and the rust preventive component are mutually filled, thereby effectively improving the denseness, rust preventive property, adhesion, and fingerprint resistance of the film. From the viewpoint, the volume ratio of the salt to the binder component is preferably 3: 7 or more and 7: 3 or less.

1-2-3. Particularly preferred system The coating layer according to the present invention is not particularly limited as long as it satisfies the above requirements, but as a particularly preferred system, for example, polyethyleneimine is applied to a silicate glassy film by a sol-gel method. A complex system can be mentioned. Since this system satisfies both the requirements as a precipitation-type inhibitor and the requirements as a binder component, it is possible to exhibit good rust prevention, substance permeation suppression function and adhesion with a small amount of adhesion, and Further, it is possible to form a coating layer excellent in balance with other properties required for the surface-treated steel sheet such as weldability. In addition, it is preferable that the molecular weight of the polyethyleneimine compounded with the said system is 1000 or more from a viewpoint of expressing favorable rust prevention property.

1-2-4. Lubricating Component The coating layer according to the present invention may be in a form applicable to plastic processing without oil application by including various kinds of self-lubricating solid lubricants. Specific examples of such a solid lubricant include olefin resin wax fine particles such as polyethylene or polypropylene, or fine metal particles such as graphite fine particles or zinc stearate.
When a lubricating component is added to the coating layer, the addition amount is preferably about 1 to 20% in terms of the weight ratio of the entire coating layer from the viewpoint of lubricity and corrosion resistance of the coating layer. More preferably, it is 5 to 15%.

2. Surface treatment agent Dissolves in water or an organic solvent the coating layer component provided on the surface of the zinc-based plated steel sheet, or the component that generates the coating layer component by the reaction in the coating / drying process of the manufacturing process of the surface-treated steel sheet described later. Alternatively, the dispersed liquid can be used as the surface treatment agent according to the present invention. The surface treatment agent of the present invention is not particularly limited as long as it satisfies such a requirement, but specific examples of particularly preferable agents include a surface treatment comprising a silicate aqueous solution containing polyethyleneimine and a fluoro compound. Drugs (hereinafter referred to as “complex agents”) can be mentioned.
From the viewpoint of effectively preventing film peeling of the film layer formed by applying the composite agent and maintaining the antirust property of the film layer, Si equivalent molar concentration X of silicate in the composite agent And X / Y of polyethyleneimine to molar concentration Y in terms of imino group is 0.5 or more and less than 1.0.
Further, from the viewpoint of improving the water-resistant adhesion of the coating layer formed of the composite material to the surface of the zinc-plated steel sheet and maintaining the corrosion resistance of the coating layer, imino in the polyethyleneimine contained in the composite agent 1 mol% or more and 50 mol% or less of the group is previously treated with a silane coupling agent and then contained in the silicate aqueous solution. Preferably, they are 1 mol% or more and 10 mol% or less. Here, specific examples of the silane coupling agent for treating the imino group of polyethyleneimine include triethoxy-glycidoxysilane.
In addition, from the viewpoint of strengthening the coating layer by promoting the hydrolysis-dehydration condensation reaction in the coating layer formed by applying the composite agent, and maintaining the corrosion resistance of the coating layer, The ratio Z / X of the molar concentration Z of the compound to the Si equivalent molar concentration X of the silicate is 0.1 or less. Specific examples of the fluoro compound contained in the composite material include various fluoro compounds such as fluorosilicic acid, fluorotitanic acid, and fluorozirconic acid.

3. Surface treatment method of surface-treated steel sheet The coating layer according to the present invention is a wet process in which a liquid (surface treatment agent) such as a solution or dispersion containing the above-mentioned film layer component is applied to the surface of a zinc-based plated steel sheet and dried. It is preferable to form by. By forming by such a method, it is possible to perform continuous coil treatment, continuously performing surface treatment on the steel sheet surface while paying off the steel sheet coil, and winding the treated steel sheet around the coil again, The productivity of the surface treatment can be improved. Here, the surface treatment in the continuous coil treatment includes a surface treatment chemical application step and a steel plate drying step. Specific examples of the method of applying the chemical to the steel sheet surface include a roll coating method and a spray coating method, while the drying method of the steel plate includes a method of drying with an oven or a dryer. .
In addition, it is preferable to perform the surface treatment method of the surface-treated steel sheet of the present invention using equipment in which chemical coating equipment and drying equipment are attached to the exit side of the continuous plating line. By performing surface treatment using such equipment, it becomes possible to continuously perform plating, chemical application, and drying, thereby improving the productivity of the surface treatment.

  The film layer and the surface treatment agent according to the present invention will be described more specifically with reference to examples.

(Example group 1)
1-1. Test method 1) Preparation of surface treatment chemicals Commercially available reagents or synthetically obtained salts are pulverized with a jet mill, and the pulverized salt and acrylic resin emulsion (binder component) are mixed and mixed with a homomixer. Smelted. Then, the salt and the acrylic resin emulsion are kneaded so that the content of the salt (valence n) is 0.2 / n (mol / L), and the total nonvolatile component is 200 (g / L). ) Surface treatment agent was prepared. The acrylic resin emulsion used in this example group was Aromatex E264 (manufactured by Mitsui Chemicals).

2) Preparation of steel plate sample An electrogalvanized steel plate (plating adhesion amount 20 g / m ² ) produced in a continuous plating line was washed with an alkaline degreasing solution, and then washed with water and dried to obtain a surface-treated substrate. . Then, by applying the drug prepared in 1) above to the surface-treated substrate by bar coating, and adjusting the substrate so that the maximum temperature of the substrate is 100 ° C. and drying it, The surface treatment substrate was subjected to surface treatment.
By such surface treatment, a surface-treated steel sheet sample provided with a 1 / n (mmol / m ² ) film layer in terms of the above-mentioned salt (valence n) was produced on the surface-treated substrate. In addition, the adhesion amount of the whole membrane | film | coat layer in the said sample was 1 (g / m < ² >).

3) Evaluation method of rust prevention property The end and back surfaces of the steel sheet sample cut so that the rust prevention evaluation surface had a size of 150 mm x 70 mm was masked with a polyester tape to obtain a test piece. And the salt spray test (SST) prescribed | regulated to JISZ2371 was done with respect to the test piece which has this rust prevention evaluation surface. In this example group, SST was performed for 24 hours, and the antirust property was evaluated by visually observing the appearance of white rust on the test piece surface after SST. The evaluation criteria for rust prevention were as follows.
○ (effective): The occurrence of white rust is clearly less than that of the blank. △ (No effect): The occurrence of white rust is equivalent to that of the blank. × (There is an adverse effect): The occurrence of white rust is clearly higher than that of the blank. Means a film layer non-formation surface.
The appearance of the sample corresponding to the evaluations ◯, Δ, and × is shown in FIG.

1-2. Test results A list of test results is shown in Tables 1 and 2 together with the salts used in the preparation of the drug, and the anion components and cation components constituting the salts.
In Tables 1 and 2, the basicity index pK _b ′ of the anion component, the acidity index pK _a as the base dissociation cation of the hydroxide relating to the cation component, and the hydroxide acid dissociation relating to the cation component For the basicity index pK _b ′ as an anion and the redox equilibrium potential E / V in the equilibrium state of the metal-aluminum compound, literature values (M. Pourvaix, Atras of Electrochemical Equilibria in Aqueous Solutions, Pergamon, 1966, No. 1) 411), and values other than E / V are the values calculated by using Equation 5, Equation 7, and Equation 9 above.
In addition, when the valence n of the cation component constituting the salt and the anion component or cation component are polymers, the molecular weight Mw is also shown.

表１及び表２のアニオン成分及びカチオン成分欄における、○×表記の基準を、以下にまとめて示す。
アニオン成分のｐＫ_ｂ’：−９．２未満（○） −９．２以上（×）
高分子の分子量Ｍｗ ：１０００以上（○） １０００未満（×）
カチオン成分のｐＫ_ａ：６．１３を超える（○） ６．１３以下（×）
カチオン成分のｐＫ_ｂ’：−９．２未満（○） −９．２以上（×）
カチオン成分のＥ／Ｖ：−０．８１未満（○） −０．８１以上（×）

The reference | standard of (circle) x description in the anion component and the cation component column of Table 1 and Table 2 is shown collectively below.
PK _b ′ of anionic component: less than −9.2 (◯) −9.2 or more (×)
Molecular weight Mw of polymer: 1000 or more (◯) Less than 1000 (×)
The cationic component _pK a: more than 6.13 (○) 6.13 or less (×)
PK _b ′ of cationic component: less than −9.2 (◯) −9.2 or more (×)
E / V of cationic component: less than −0.81 (◯) −0.81 or more (×)

From Tables 1 and 2, the salt in the coating layer has the following two conditions: (A) An anion whose pK _b ′ is less than −9.2 because it has a stronger basicity than the zincate ion, or a molecular weight of 1000 or more containing anion is (B) exceeds the pK _a is 6.13 because it has a weaker acid than the zinc ion as the cation, and, pK for acid dissociation anion of hydroxide has strong basicity than zincate ions _b 'is less than -9.2, and is a metal cation lower than zinc in the electrochemical series, so that E / V is less than -0.81, or a molecular weight of 1000 or more and a primary grade. It was confirmed that rust preventive properties were exhibited only when the polymer cation containing polyethyleneimine, which is a polymer cation having an amino group, was simultaneously satisfied.
In addition, when the anion component does not satisfy the above condition (A) and when the cation component is a noble metal ion than zinc, white rust is clearly generated more than the blank, and the corrosion resistance is deteriorated. Confirmed to do.

(Example group 2)
2-1. Test method 1) Preparation of surface treatment chemicals The types of industrial materials used for the preparation of surface treatment chemicals in this example group are shown in the order of “substance name: trade name (company name)” below. In addition, after each substance name, the abbreviation used in the following is added in parentheses.
Lithium silicate aqueous solution (LS): Lithium silicate 35, 45, 75 (manufactured by Nissan Chemical Industries)
Tetramethoxysilane (TMS): KBM04 (manufactured by Shin-Etsu Chemical)
・ Sodium silicate (NS): Sodium silicate solution (manufactured by Nippon Chemical Industry Co., Ltd.)
Potassium silicate (KS): Potassium silicate solution (manufactured by Nippon Chemical Industry)
・ Colloidal silica (SN): Snowtex N (manufactured by Nissan Chemical Industries)
・ Polyethyleneimine (PEI): Epomin (made by Nippon Shokubai)
Silane coupling agent (SC): Sila Ace S510 (manufactured by Chisso)
Fluorotitanic acid (H ₂ TiF ₆ ): Fluorotitanic acid (Gemco)
・ Acrylic resin emulsion (AE): Almatex E264 (Mitsui Chemicals)
-Urethane resin emulsion (UE): Olester UD600 (Mitsui Chemicals)
The raw material type and the addition amount of the surface treatment chemical according to this example group are the chemical number, the ratio of the molar concentration of the fluoro compound contained in the chemical to the Si equivalent molar concentration of the silicate (F / Si), and the silane cup. Table 3 (drug Nos. 1 to 7), Table 4 (drugs No. 8 to 14), and Table 5 (drugs No. 15 to 17) together with the ratio of the imino group of polyethyleneimine treated with the ring agent Shown in

表３、表４、及び、表５において、アニオン成分の添加量及びカチオン成分におけるＰＥＩの添加量は、それぞれ、Ｓｉ換算モル濃度及びポリエチレンイミンのイミノ基換算モル濃度を表している。なお、表３、表４、及び、表５において、原料の種類は全て省略表記で記載した。
薬剤を調合するにあたり、薬剤濃度はイオン交換水で調整し、薬剤Ｎｏ．２以外はトータルの不揮発成分として２００（ｇ／Ｌ）の表面処理薬剤を調合した。一方、ゾル−ゲル法によるシリケート系ガラス状皮膜とする際に加水分解を必要とする薬剤Ｎｏ．２については、トータルの不揮発成分として１００（ｇ／Ｌ）の表面処理薬剤を調合した。

In Table 3, Table 4, and Table 5, the addition amount of the anion component and the addition amount of PEI in the cation component represent the Si equivalent molar concentration and the imino group equivalent molar concentration of polyethyleneimine, respectively. In Table 3, Table 4, and Table 5, all types of raw materials are described in abbreviated notation.
In preparing the drug, the drug concentration is adjusted with ion-exchanged water. Except 2, 200 (g / L) of the surface treatment chemical was prepared as a total nonvolatile component. On the other hand, when a silicate glassy film by the sol-gel method is used, a drug No. which requires hydrolysis is used. For No. 2, 100 (g / L) of the surface treatment chemical was prepared as a total nonvolatile component.

The drug was prepared according to the following procedure.
i) Add a predetermined amount of polyethyleneimine emulsion to ion-exchanged water and stir ii) Add a silane coupling agent dropwise to the liquid i) under stirring and stir and cure for about 1 hour iii) Silicate A predetermined amount of a systemic agent is dropped into the above liquid ii) with stirring and mixed. Iv) A predetermined amount of fluorotitanic acid aqueous solution (H ₂ TiF ₆ ) is dropped into the above iii) liquid under stirring and mixed here. In the case of preparing a medicine that does not use polyethyleneimine as a raw material, the preparation of the medicine was performed by omitting the procedure i). In addition, a drug No. that requires hydrolysis. In the preparation of 2, the stirring and curing time in the above procedure iii) was set to 2 days and nights.

2) Adjustment of steel plate sample Table 6 shows the types of zinc-based plated steel plates used in this example group, the plate thickness (mm), the coating weight per side (g / m ² ), and the production category. Here, the line material means a steel plate produced by a continuous plating line, and the lab material means a steel plate produced in a laboratory.

表６に示す各鋼板をアルカリ性脱脂液により洗浄した後、水洗及び乾燥処理を施し、表面処理基材とした。そして、本実施例群にかかる薬剤をバーコーティングにて表面処理基材に塗布し、熱風オーブンで基材の最高到達温度が１００℃となるように調節して乾燥させることにより、表面処理基材に表面処理を施した。
作製した表面処理鋼板サンプルの基材、薬剤番号、皮膜付着量（ｇ／ｍ^２）、及び、カチオン量換算の塩の付着量（ｍｍｏｌ／ｍ^２）をあわせて、表７、表８に示す。

Each steel plate shown in Table 6 was washed with an alkaline degreasing solution, then washed with water and dried to obtain a surface-treated substrate. And the chemical | medical agent concerning a present Example group is apply | coated to a surface treatment base material by bar coating, and the surface treatment base material is adjusted and dried so that the maximum reached temperature of a base material may be 100 degreeC with a hot air oven. A surface treatment was applied.
Table 7 and Table 8 show the base material, drug number, coating amount (g / m ² ), and amount of cation converted salt (mmol / m ² ) of the prepared surface-treated steel sheet sample. .

3) Evaluation method of rust prevention property The end and back surfaces of the steel plate sample cut so that the evaluation surface of rust prevention property was 150 mm x 70 mm was masked with a polyester tape to obtain a test piece. And the salt spray test (SST) prescribed | regulated to JISZ2371 was done with respect to the test piece which has this rust prevention evaluation surface. In this example group, the test piece was observed every 24 hours, and “time when the area ratio of white rust in the rust prevention evaluation surface exceeded 5% −24” was defined as the white rust occurrence time, according to the following criteria: The rust resistance was evaluated.
White rust occurrence time> 24: Pass (○)
White rust occurrence time = 0: Fail (x)

2-2. Test results Tables 7 and 8 show the results of the SST rusting time (h) in each surface-treated steel sheet sample.

From the results of this example group shown in Table 7, a coating layer was provided using a surface treatment agent (drug No. 2-7, 9-10, and 14-17) containing silicate and polyethyleneimine (PEI). Steel systems (Examples Nos. 2-1-4 to 21, Nos. 2-1-25 to 30 and Nos. 2-1-40 to 51) subjected to chromate treatment. It was confirmed that the rust prevention performance equivalent to that of Group No. 2-1-52) was exhibited. In addition, Example group No. 2-1-19, the amount of deposition of salt is 0.09 mmol / ^{m 2,} for not less than 0.1 / n mmol / ^{m 2,} corrosion resistance was not expressed.

  In addition, a drug no. From the results of Example group 2-1 to 1-3 using No. 1, even when a film layer was provided with a chemical agent composed of a silicate-based aqueous solution, rust preventive properties were not exhibited. Therefore, it was confirmed that a polymer component needs to be contained in the silicate aqueous solution in order to develop rust prevention. On the other hand, the drug No. containing no silicate component. From the results of Example group 2-1-22 to 24 using No. 8, it was confirmed that the rust preventive property was not exhibited only by the polymer component.

  Furthermore, the drug No. containing a polymer other than the cationic water-soluble polymer. From the results of Example groups 2-1 to 31-36 using 11 and 12, even when the polymer was contained in a silicate-based aqueous solution, rust preventive properties were not exhibited. Therefore, it was confirmed that a cationic water-soluble polymer (for example, polyethyleneimine or the like) needs to be contained in the silicate aqueous solution in order to develop the antirust property.

  In addition, the chemical No. 1 containing silica instead of silicate. From the results of Example group 2-1 to 37 to 39 using No. 13, it was confirmed that silicate, not silica, had a rust preventive effect.

  On the other hand, from the results of this example group shown in Table 8, by providing a coating layer using a low environmental load type surface treatment agent according to the present invention, various zinc-based plated steel sheets have the same degree as chromate treatment. It was confirmed that the rust prevention property was developed.

It is a figure which shows the example of white rust generation | occurrence | production evaluation after a salt spray test.

Claims (8)

A coating layer containing at least one salt composed of an anion satisfying the condition of (1) or (2) and a cation satisfying the condition of (3) or (4) is a surface of the galvanized steel sheet. A surface-treated steel sheet provided in
A surface-treated steel sheet, characterized in that when the charge of the cation constituting the salt is n, the salt is contained in an amount of 0.1 / n mmol / m ² or more in terms of the cation.
(1) Anion having a stronger basicity than zincate ion (2) Anion having a molecular weight of 1000 or more (3) It has a weaker acidity than zinc ion as a cation and an acid dissociation anion of hydroxide is stronger than zincate ion Metal cation having basicity and being baser than zinc in the electrochemical series (4) Cation having a primary amino group having a molecular weight of 1000 or more The surface-treated steel sheet according to claim 1, wherein the cation constituting the salt is at least one selected from magnesium ion, calcium ion, strontium ion, or polyethyleneimine. . The surface according to claim 1 or 2, wherein the anion constituting the salt is at least one kind selected from silicate ions, phosphate ions, or polyacrylic acid. Treated steel sheet. The surface-treated steel sheet according to any one of claims 1 to 3, wherein the salt contains a silicate ion as the anion and a polyethyleneimine as the cation. A surface treatment agent comprising a silicate-based aqueous solution containing polyethyleneimine,
A surface treatment agent, wherein the ratio X / Y between the Si equivalent molar concentration X of the silicate and the imino group equivalent molar concentration Y of the polyethyleneimine is 0.5 or more and less than 1.0. The surface treatment agent according to claim 5, further comprising a fluoro compound and a silane coupling agent,
The ratio X / Y between the Si equivalent molar concentration X of the silicate and the imino group equivalent molar concentration Y of the polyethyleneimine is 0.5 or more and less than 1.0,
The ratio Z / X of the molar concentration Z of the fluoro compound to the molar concentration X in terms of Si is 0.1 or less,
The surface treatment agent, wherein 1 mol% or more and 50 mol% or less of imino groups in the polyethyleneimine is previously treated with the silane coupling agent. A surface-treated steel sheet, characterized in that the surface of the zinc-based plated steel sheet is treated with the surface treatment agent according to claim 5 or 6. A surface-treated steel sheet, wherein the surface-treated chemical according to claim 5 or 6 is applied to a surface of a zinc-based plated steel sheet, and the zinc-based plated steel sheet coated with the surface-treated chemical is dried without washing. Surface treatment method.

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