JPS6322637A - High corrosion resistance surface-treated steel plate - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a highly corrosion-resistant surface-treated steel sheet suitable for use in automobile bodies and the like.

[Prior Art] In recent years, steel plates used for automobile bodies are required to have excellent corrosion resistance, and there is a growing tendency to use surface-treated steel plates with high corrosion resistance in place of the conventionally used cold LTI plates.

The first example of such surface-treated steel sheets is galvanized steel sheets, but with this type of steel sheet, it is necessary to increase the amount of zinc deposited in order to improve corrosion resistance, and along with this, workability and weldability are reduced. There is a problem of deterioration. In order to improve such problems, Ni, Fe, Mn, Mo,
Zinc alloy plated steel sheets and multilayer plated steel sheets to which one or more elements such as Go, AJI, Cr, etc. are added have been researched and developed, and these steel sheets have poor weldability compared to the above-mentioned galvanized steel sheets.

Corrosion resistance can be improved without deteriorating workability. However, when steel plates are applied to the bag structure and bent parts (hemming parts) of automobile body panels, the surfaces must have a high degree of corrosion resistance, so zinc alloy plated steel plates and multilayered steel plates such as those mentioned above are required. A problem with plated steel sheets is that their corrosion resistance is still insufficient. As a steel plate with a high degree of corrosion resistance, rust-preventive coated steel plates with zinc-rich coatings, such as those seen in Japanese Patent Publication No. 45-242'30 and Japanese Patent Publication No. 47-6882, have been researched and developed. The thing is known by the name of Synchrometal. However, even with this anti-corrosion coated steel sheet, the coating may peel off in the processed parts such as press forming, and the corrosion resistance may deteriorate. is still far from being fully satisfactory.

For this reason, the present inventors have developed a thin film (less than divisor) that does not use metal powder such as Zn powder at all, from the viewpoint that there is a limit to the performance improvement of anti-rust coated steel sheets with zinc-rich coating films. We developed a new steel plate with a protective film of 1988-224174, 60-50179, 60-50180 and 60-5018.
It was proposed as No. 1. This steel sheet is based on a zinc or zinc alloy plated steel sheet, and is coated with a chromate film and an organic composite silicate film as the top layer, and has excellent workability and corrosion resistance.

Furthermore, in some parts of the inner surface of the automobile body (trunk lid, hood, etc.), a top coat is applied to the cationic electrodeposition coating.
There are cases where more than one coat of paint is applied, and there are concerns about the adhesion of the steel sheet proposed above in the case of such multi-layer coatings, so we improved the above-mentioned steel sheet and improved the adhesion of the multi-layer coating. JP-A-60-17 published a method for producing excellent rust-proof steel sheets for multi-layer coating.
It was proposed as No. 4879.

This invention sufficiently crosslinks the organic polymer film by baking at a high temperature of 250 to 350" O to ensure excellent paint adhesion for multilayer coating. In this case, the alkali generated at the interface during cationic electrodeposition causes the film to swell softly, resulting in poor paint adhesion, which is improved by crosslinking by high-temperature baking.

[Problems to be Solved by the Invention] However, subsequent research by the present inventors revealed that the above-mentioned steel plate has excellent paint adhesion (multilayer paint adhesion of two or more coats) by baking at a high temperature of 250°C or higher. ), but it is assumed that the electrodeposited coating is difficult to form. If there is a problem with the so-called naked corrosion resistance (corrosion resistance without painting) and the surface treatment film is damaged, 1. For example, if the steel is subjected to cross-cutting, deep drawing, drawbead processing, etc. that reach the iron base,
It has been found that the bare corrosion resistance tends to be slightly inferior to that of the steel plates disclosed in JP-A-58-224174 and the like mentioned above.

Highly corrosion-resistant surface-treated steel sheets for automobiles have excellent workability and weldability, as well as: 1) Corrosion resistance in areas where electrodeposited coatings are difficult to form, such as the bag structure and hemming areas, that is, a high degree of bare corrosion resistance.

2) Paintability for multi-layer coatings of 2 coats or more (cationic electrolyte + top coat) such as trunk lids and hood inner surfaces (
paint adhesion, paint corrosion resistance).

In recent years, there has been a growing demand for anti-corrosion properties for automobile bodies, and the above-mentioned steel sheets cannot be said to have sufficient properties.

The present invention was developed in view of these conventional problems, and provides excellent workability and weldability, as well as excellent bare corrosion resistance, paint damage resistance against multilayer coating, and paint corrosion resistance.

The present invention aims to provide a highly corrosion-resistant surface-treated steel sheet with high corrosion resistance.

[Means for solving the problem] Therefore, the basic features of the present invention are as follows.

(1) A chromate film is formed on the surface of a galvanized or zinc alloy plated steel sheet, and on the top of the chromate film, at least one basic nitrogen atom and at least two primary hydroxyl groups are formed at the end of the epoxy resin. A highly corrosion-resistant surface-treated steel sheet comprising a resin composition film containing a polyisocyanate compound added to a base resin.

(2) A chromate film is formed on the surface of a galvanized or zinc alloy plated steel sheet, and on the top of the chromate film, at least one basic nitrogen atom and at least two primary hydroxyl groups are formed at the end of the epoxy resin. A polyisocyanate compound and a base resin/
A highly corrosion-resistant surface-treated steel sheet comprising a resin composition film containing silica in a weight ratio of 8371 to 30/70.

(3) A chromate film is formed on the surface of a galvanized or zinc alloy plated steel sheet, and on the top of the chromate film there is at least one basic nitrogen atom and at least two primary hydroxyl groups at the end of the epoxy resin. A polyisocyanate compound, silica with a base resin/silica weight ratio of 9S71-30/To, and a base resin/insoluble chromium compound weight ratio of 997
A highly corrosion-resistant surface-treated steel sheet comprising a resin composition film containing an insoluble chromium compound in a ratio of 1 to 80/40.

The present invention will be explained in detail below.

The present invention uses a zinc-plated or zinc alloy-plated steel sheet as a starting material, and has a chromate film on its surface and a basic epoxy resin film on its surface.

The starting materials, zinc-coated steel sheets, include galvanized steel sheets, zinc-iron alloy-plated steel sheets, zinc-nickel alloy-plated steel sheets, zinc-manganese alloy-plated steel sheets, zinc-aluminum alloy-plated steel sheets, and zinc-cobalt-chromium alloy-plated steel sheets. , furthermore, the plating components of these arbitrary steel plates include Ni,
FeJn, No, G.

, An, Cr, etc. can be used, and even if it is a composite plated steel sheet with two or more layers of the same or different types of plating as described above. For example, Fe-Z with different Fe contents
It is possible to form a plating film in which two or more layers of n-alloy plating are applied.

Among these, zinc-nickel alloy plated steel sheets and zinc-manganese alloy plated steel sheets are particularly preferred from the viewpoint of corrosion resistance. When these steel sheets are used, the zinc-nickel alloy plated steel sheets have a nickel content in the plating film of 5 to 5. 20
The wt1 zinc-manganese alloy steel plate preferably has a manganese content in the range of 30 to 85 wtX.

As a plating method for these galvanized steel sheets, any practicable method among electrolytic method, melting method, vapor phase method, etc. can be adopted. However, the rust-proof steel sheets that are the object of the present invention are mainly used for automobile bodies, and in such applications, it is important not to damage the material of the cold-rolled steel sheets to be plated. Therefore, it can be said that electroplating, which does not generate heat, is advantageous.

A chromate film is formed on the surface of the plated steel plate as a raw material by chromium treatment.

This chromate film has a chromium adhesion M(dry) of I~looomx/rn', preferably 10-2
It is appropriate to set it to about 00 mg/rn' (the above is converted into metal chromium). If the amount of chromium deposit exceeds 1000g/m', workability and weldability deteriorate, and IIIg/rn
If the chromate film is less than 1, it is undesirable because it has a tendency to run unevenly, and it is preferable for the chromate film to contain hexavalent Cr. CrG+ has a repairing effect and suppresses corrosion when the steel plate is scratched. have the effect of

The chromate treatment for such a base film may be performed by any known method such as reaction type, coating type, electrolytic type, etc.

The main component of the coating type chromate treatment solution is a partially reduced chromic acid solution, and if necessary, an organic resin such as a wood-dispersible or water-soluble acrylic resin and/or a particle size range is added to this.
It contains several hundred pounds of silica (colloidal silica, fumed silica). In this case Cr'◆/C
The ratio of r”÷ is 1/1 to 1/3. The pH is 1.5 to 4.0.
(more preferably 2 to 3), Cr”/
The ratio of Cr'+ is adjusted to a specified ratio using a general organic reducing agent (e.g. sugars, alcohols, etc.) or an inorganic reducing agent.
make a clause Further, as the coating type chromate treatment, any method such as a roll coater method, a dipping method, a spray method, etc. may be used. In the coating type chromate treatment, a film is obtained by drying without washing with water after the chromate treatment. The reason for drying without rinsing in this way is 1. Normal washing with water removes Cr'', and Cr'÷/Cr''
The basic epoxy resin film formed on the top of the CrG+
It is possible to suppress excessive outflow of , effectively maintain the passivation effect over a long period of time, and obtain high corrosion resistance.

On the other hand, in electrolytic chromate treatment, cathodic electrolysis is performed in a bath containing chromic anhydride and one or more of 7 ions such as sulfuric acid, phosphoric acid fluoride, or halogen oxygen acid, followed by washing and drying. Comparing the two chromate coatings formed by 0 or more treatment methods, the coated chromate has superior corrosion resistance compared to the electrolytic chromate because it contains more hexavalent chromium in the coating. When heat treated as described below, the film becomes dense and strong, resulting in better corrosion resistance than electrolytic chromate. On the other hand, electrolytic chromate has the advantage of having a high degree of completeness of the film regardless of the presence or absence of heat treatment.
It has the advantage of being easy to control the amount of film deposited. In consideration of corrosion resistance, coating type chromate is the most desirable.Also, rust-proof steel sheets for automobiles are often single-sided treated steel plates, and from this point of view, coating type and electrolytic type are preferable.

A basic epoxy resin film is formed on the chromate film.

This resin film is formed by adding at least one basic nitrogen atom and at least two or more primary hydroxyl groups to the end of an epoxy resin as a base resin.

This film is made by heating and curing a resin composition containing a polyisocyanate compound.

The epoxy resin is preferably one based on a condensate obtained by condensing bisphenol A and shrimp chlorohydrin. Examples of the epoxy resin include epoxidized oil,
There are epoxy resins such as polybutadiene that consist only of aliphatic structures or alicyclic structures, but in order to obtain excellent corrosion resistance, it is preferable to use epoxy resins mainly composed of the above condensates. For example, Epicor) 828,100+, 1004.100? , 1009
．． 1010 (1% deviation also manufactured by Shell Chemical Co., Ltd.), etc. can be used. This epoxy resin desirably has a number average molecular weight of 1,500 or more especially when curing at low temperatures is required. Note that the above Epicoat can be used alone or in a mixture of different types. To introduce basic nitrogen atoms and primary hydroxyl groups into epoxy resin 1
For example, a method can be adopted in which alkanolamine and/or alkylalkanolamine is added to the oxirane group of the epoxy resin. Examples of these amines include monoethanolamine, jetanolamine, dimethylaminoethanol, motuprobanolamine, dibrobanolamine, and jetanolamine, and these amines are used alone or in combination.

Alternatively, the epoxy resin may be partially modified with other compounds; however, in this case, it is necessary to contain an average of 2 moles or more of primary hydroxyl groups in each molecule of the epoxy resin. .

Methods for partial modification of epoxy resins include: (1) Esterification with monocarboxylic acids (monocarboxylic acids include saturated or unsaturated fatty acids such as coconut oil fatty acids, soybean oil fatty acids, castor oil supplements, acetic acid, propionic acid) (2) Modification with aliphatic or aromatic amines (aliphatic or aromatic amines include monomethylamine, dimethylamine, Aliphatic amines such as monoethylamine, diethylamine, isopropylamine, aromatic amines such as aniline, etc.) (3) Modification with oxyacids (oxyacids include lactic acid, γ-oxydipropionic acid, etc.).

Note that there is also a modification method using dicarboxylic acids (e.g. adipic acid, sepatic acid, etc.), but this method does not increase the molecular weight of the epoxy resin more than necessary, and furthermore, it is difficult to control the molecular weight distribution at a constant level in terms of reaction control. This method is inappropriate for obtaining the coating of the present invention because it is difficult and no improvement in corrosion resistance is observed.

The curing method for forming the film of the present invention is preferably based on a urethanization reaction between isocyanate and hydroxyl groups in the base resin, but the resin composition before film formation can be stably stored. In order to achieve this, it is necessary to protect the curing agent incyanate. As a method for protecting the incyanate compound, a protection method in which the protecting group is removed during heating and the incyanate group is regenerated can be adopted.

Isocyanate groups include aliphatic and alicyclic groups (including heterocycles) having at least two isocyanate groups in one molecule.
Alternatively, it is an aromatic incyanate compound, or a compound obtained by partially reacting these compounds with a polyhydric alcohol. For example, (1) @- or p-phenylene diisocyanate, 2,4- or 2,8-tolylene diisocyanate, or p-xylylene diisocyanate, hexamethylene diisocyanate, dimer ugly diisocyanate, inphorone diisocyanate, (2) the above (1) alone or in combination with polyhydric alcohols (dihydric alcohols such as ethylene glycol and propylene glycol, trihydric alcohols such as glycerin and trimethylolpropane, tetrahydric alcohols such as pentaerythritol, sorbitol, dipentaerythritol) A compound in which at least two incyanates remain in one molecule, which is a reaction product with a hexahydric alcohol (such as hexahydric alcohol).

and so on.

Further, as this protective agent (blow-removal agent), for example, 1 is used.

(1) Aliphatic monoalcohols such as methanol, ethanol, propatool, butanol, octyl alcohol, etc. (2) Monoethers of ethylene glycol and/or diethylene glycol, such as methyl, ethyl,
Propyl (r+-, 1SO), butyl (n-, :go,
sec), (3) aromatic alcohols such as phenol and cresol, (4) oximes such as acetoxime and methyl ethyl ketone oxime, and reacting one or more of these with the incyanate compound. In this way, an isocyanate compound that is stably protected at least at room temperature is obtained.

Such an incyanate compound is preferably blended as a curing agent at a ratio of 5 to 80 parts, preferably 10 to 50 parts, per 100 parts of the base resin (solid content). However, if more than 80 parts of this is added, the adhesion will deteriorate.In addition, when electrodeposition coating or spray painting is performed on surface-treated steel sheets for automobiles, unreacted isocyanate compounds may be present in the coating film. From this viewpoint, the incyanate compound is preferably blended in an amount of 80 parts or less.

Further, as a crosslinking agent, alkyl etherification is obtained by reacting a monohydric alcohol having 1 to 5 carbon atoms with part or all of a methylol compound obtained by reacting formaldehyde with one or more selected from melamine, urea, and benzoguanamine. Amino resins may be used in combination with isocyanate compounds.

Although the resin is sufficiently crosslinked with the above-mentioned crosslinking agent, in order to further increase the low-temperature crosslinkability, it is desirable to use a known curing accelerating catalyst. Examples of this curing accelerating catalyst include N-ethylmorpholine. , dibutyltin laurate, cobalt naphthenate, stannous chloride, zinc naphthenate, and bismuth nitrate. Further, with the aim of slightly improving physical properties such as adhesion, known resins such as acrylic, alkyd, and polyester can also be used in combination with the above resin composition.

The film-forming composition of the present invention can be used as a water-dispersed or water-soluble composition by neutralizing the base of the epoxy resin, which is the basic resin, with a low-molecular acid, but it can be used by drying at a low temperature of 250°C or less. In particular, when it is used as a coating material for H steel plates, which requires extremely low temperature drying of 170°C or lower, it is best to use it as a composition dissolved in an organic solvent without performing such a neutralization operation. More desirable.

That is, in a water-dispersed or water-soluble composition, the acidic compound required for water solubilization forms a salt in the film,
Corrosion resistance and adhesion tend to be somewhat poor because moisture is easily absorbed into and under the film in a humid environment, and a sufficiently strong film cannot be obtained under low-temperature drying conditions.

As the type of organic solvent, one type of organic solvent or a mixed solvent of two or more types commonly used in the paint industry can be used.
For that purpose, it is preferable to avoid high-boiling alcoholic solvents, such as ethylene or diethylene glycol, monoalkyl ethers,
Examples include alcohols having a primary hydroxyl group of 05 or more. Such solvents inhibit the curing reaction of the film. Recommended solvents include hydrocarbon, ketone, ester, and ether solvents, and alcohols with a low molecular weight of 04 or less, or alcohols with secondary or tertiary hydroxyl groups are also suitable. The purpose of providing the resin composition film as described above in the invention is as follows. In other words, in order to obtain a high degree of corrosion resistance and adhesion of two or more coats of multilayer coatings, we adopted an epoxy resin as the base and expected to obtain high adhesion to the substrate and cationic electrodeposition as well as high corrosion resistance. , ■ In addition, by making the polarity of the resin basic, deterioration of the resin structure due to alkali generated at the interface during cationic electrodeposition is eliminated, and ■ By using incyanate as a curing agent, it is possible to achieve sufficient m-density by low-temperature curing. The objective is to obtain a highly cross-linked density film.

To explain this in detail, first, by using an epoxy resin made from a condensation reaction of bisphenol A and epichlorohydrin as the base resin, it has superior properties compared to cationic electrodeposition paints commonly used for rust prevention of automobile bodies. Adhesion can be expected. In addition, by introducing basic nitrogen atoms and primary hydroxyl groups into the resin structure, (1) it prevents the film from being destroyed by the alkali generated during cationic electrodeposition, and stabilizes the adhesion with the base chromate and cationic electrodeposited coating. The (2)-class water ugliness group and the selected organic solvent composition are combined with the crosslinking agent (
Enhances low-temperature reactivity with isocyanates).

(3) Furthermore, by introducing 2 moles or more of hydroxyl groups into one epoxy molecule, a film with a sufficiently dense crosslinked structure can be obtained. If the amount is less than 2 moles, sufficient crosslinking cannot be obtained.

In addition, known chromium-based, non-chromium-based antirust pigments, extender pigment 1 color pigments, and the like can be blended into the resin composition film.

The above resin composition film is prepared by applying the composition to a predetermined thickness by a method such as roll squeezing, roll coater 1 or air knife, and then applying the film at a plate temperature of 80 to 250°C (preferably 1
0 to 200℃)
The steel sheet of the present invention has the great feature that it can be obtained by such low-temperature baking.

If the baking temperature is lower than 80°C, crosslinking of the film will not proceed and sufficient corrosion resistance will not be obtained.On the other hand, if the baking temperature is higher than 250°C,
Corrosion resistance deteriorates like No. 9. This is because when baking at a high temperature exceeding 250°C, the chromate film is destroyed due to cracking in the chromate film due to chromate progression.
It is also presumed that this is due to the fact that the reduction of cr'0 progresses and the passivation effect of CrG+ is reduced.

In the present invention, silica can be contained in the resin composition film to improve the anticorrosion effect. Silica has a base resin/silica weight ratio of 89/l to 30/70, preferably 90/l.
/10 to 50150. The mechanism by which silica improves corrosion resistance is not necessarily clear, but Zn2+ eluted in a corrosive environment reacts with silica, producing stable corrosion products and inhibiting pitting corrosion. It is estimated that the effect of improving corrosion resistance can be obtained.

Here, the blending amount of silica is basic resin/silica: 99/l
If the ratio is below 30/70, no improvement in corrosion resistance can be expected due to the combination, and on the other hand, if the ratio exceeds 30/70, the adhesion of multilayer coatings of 2 or more coats will decrease.

The silica used in the present invention includes water-dispersible silica called colloidal silica and fumed silica, and hydrophobic silica. Among these silicas, water-dispersible silica can also be expected to have the effect of improving corrosion resistance, but as described in t&, hydrophobic silica significantly improves corrosion resistance. As for the particle size of silica.

1 ■Roux 5 and 0 layers are appropriate.'1. Especially 5 coffee~
100 mp is preferred.

Water-dispersible silica, known as colloidal silica (silica gel) or fumed silica, has its surface covered with hydroxyl groups (silanol groups (5i-OH)).
This silanol group, which exhibits wood-philic properties, is highly reactive and therefore reacts with various organic compounds, making it possible to organicize the silica surface.

Hydrophobic silica is obtained by subjecting some or most of the silanol groups on the surface of such water-dispersible silica to a substitution reaction with a methyl group, an alkyl group, etc. to make the silica surface hydrophobic.

There are many different methods for producing hydrophobic silica, and typical examples include reactions with organic solvents such as alcohols, ketones, and esters, silanes, silazane, and polysiloxanes. Examples include a reaction pressurization method in an organic solvent and a catalyst heating method.

Silica has an excellent anti-corrosion effect, and hydrophobic silica is particularly effective in improving corrosion resistance. has been shown to be added. However, water-dispersible silica has poor compatibility with solvents due to its strong hydrophilicity, and its strong hydrophilicity also causes water to easily penetrate, which causes a decrease in corrosion resistance, especially in a humid environment. It is estimated that it is likely to cause initial rust.

Therefore, when manufacturing the steel sheet of the present invention, it is preferable to blend silica with a hydrophobic surface (hydrophobic silica) into the basic resin to increase the compatibility with the basic epoxy resin and obtain high corrosion resistance.

Examples of such hydrophobic silica include ■ methyl alcohol, ethyl alcohol, n-propyl alcohol,
Organic solvent-dispersed colloidal silica dispersed in a solvent such as isopropyl alcohol, n-butyl alcohol, ethyl cellosolve, or ethylene glycol (for example, oscAL 1132.1232.1332.
1432.1532.1622.1722.1724, etc.), (2) Silica whose surface has been made hydrophobic with an organic solvent or a reactive silane compound, i.e., hydrophobic ultrafine particle silica (for example, R974, R811, R812 manufactured by Nippon Aerosil Co., Ltd.)
, R805, TaO2, R202, RY200. RX2
00 etc.).

The hydrophobic silica described above is stably dispersed in the basic epoxy resin.

In the present invention, an insoluble chromium compound can be further included in the resin composition film together with the silica, thereby further improving corrosion resistance. In a corrosive environment, C, l+ is removed from insoluble chromium compounds in the film.
It is eluted in large amounts, and this exerts an immobilization effect over a long period of time, improving corrosion resistance.

This insoluble chromium compound is blended in a weight ratio of base resin/insoluble chromium compound in the range of 99/1 to 80/40. If the blending amount of the insoluble chromium compound is base resin/insoluble chromium compound: 9B/1 or less, no improvement in corrosion resistance can be expected from the blending, while if it exceeds 80740, the water absorption effect of the insoluble chromium compound will result in two parts being mixed. The adhesion and corrosion resistance of multilayer coatings of 5 or more layers will deteriorate.

As these chromium compounds, powders of strontium chromate, lead chromate, zinc chromate, barium chromate, calcium chromate, and potassium zinc chromate can be used, and one or more of these powders can be used as a substrate. Disperse in resin.

Chromium compounds other than these may have poor compatibility with the base resin, or may have an anticorrosion effect but are soluble Cr.
Since it contains a large amount of needles, it has problems such as poor adhesion of two coats of paint, and is not suitable for the purpose of the present invention.

Note that the present invention does not preclude the use of other additives, antirust pigments, etc. in addition to the above additive components, silica and insoluble chromium compounds.

The resin composition film as described above is coated on the chromate film.
．． 1~3.5g/m2, preferably 063~2.0g/m2
If the coating weight is less than 0.1 g/m, sufficient corrosion resistance will not be obtained, while if it exceeds 3.5 g/m, weldability (especially Continuous multi-point weldability) decreases, and 0.1 to 3.5 g
/m'' range is suitable as a highly corrosion-resistant surface-treated steel sheet for automobiles.

Furthermore, although cationic electrodeposition coating is applied to automobile bodies,
Wet electrical resistance of chromate film + resin composition film is 20
There is a problem that a cationic electrodeposited coating film cannot be formed well if Ω/C exceeds 2. Therefore, in the steel sheet of the present invention, which is mainly used for automobile bodies, the wet resistance of the chromate film + resin composition film is set to 200 Ω/C. It is preferable to form both films so that the thickness is suppressed to 0.7 cm or less.

The present invention includes a steel plate having the above-described film structure on both sides or one side.

Examples of the embodiments of the steel sheet of the present invention include the following.

(1) One side...Plated film - Chromate film - Resin composition film One side...Fe side (2) One side... Plated film - Chromate film - Resin composition film One side... Plated film (3) Both sides ... Plating film - Chromate film - Resin composition film [Example] Table 1-a, Table 1-
An adhesion test and a corrosion resistance test were conducted on the materials of the present invention having different adhesive components and coating amounts as shown in Table b and Table 1-a. Similar tests were also conducted on steel plates shown in Tables 2-a and 2-b as comparative materials.

The plating components of each steel plate are as follows. For each steel plate in the table with a chromate film and a basic epoxy resin film, the plated steel plate is degreased with alkaline, washed with water, dried, and then coated with a coating-type chromate treatment solution. An electrolytic chromate film was formed by coating with a roll coater or by dipping in an electrolytic chromate treatment bath, and after drying, a basic epoxy resin layer was coated as a second layer with a roll coater. After further drying, it was heat-treated and air-cooled.

Ni-Zn alloy electroplating/ski content 12 XF
e-Zn alloy electroplating @@F+! Content 25tMn
-Zn alloy electroplating: n-containing m80% Zn-Al
Alloy TL air plating...A1 content 5z Details of the coating type chromate treatment, electrolytic chromate treatment, and basic epoxy resin armpit are as follows.

・Coating type chromate treatment conditions Cr” / Cr” = 2 / 3, p) l =
A chromate treatment solution having a solid content of 2.5 (pH adjusted with KOH) of 20 g/liter was applied at room temperature using a roll coater and then dried.

φ electrolytic chromate treatment conditions Crux: 50g/1. H2SO4: 0
．． 5g/l.

A current density of 4.9 A/dm' with a bath temperature of 50°C.
, cathodic electrolysis treatment was performed for an electrolysis time of 2.0 seconds, followed by washing and drying.

φ Resin Composition The base resin and curing agent prepared as follows were mixed in the proportions shown in Table 3 to prepare a resin composition.

0 Base Resin CI) Epicoat to04 (manufactured by Shell Chemical Co., Ltd., exo resin bimolecular weight approximately 1800) 18
00g, pelargonic acid (reagent) 57g, xylene 80g
was added, and the reaction was allowed to proceed at 170° C. until the acid value of the reactant became approximately O. Thereafter, xylene was removed under reduced pressure to obtain a reaction intermediate [A].

(11) Epicor 1009 (epoxy resin manufactured by Shell Chemical Co., Ltd.: molecular weight 3750) 1880 g (0
, 5 mol) Tomethyl-isobutyl ketone/xylene=
After adding 1000 g of a mixed solvent of 1/1 (weight ratio), the mixture was stirred and heated using Wl to uniformly dissolve the mixture at the boiling point of the solvent. Thereafter, the di(n) was cooled to 70°C and fractionated into a liquid dropping device.
−Proper Tools) Amine? Og was added dropwise over a period of 30 minutes. During this time, the reaction temperature was maintained at 70° C. After the completion of 0 dropwise addition, the reaction temperature was maintained at 120° C. for 2 hours to complete the reaction. The obtained reaction product is referred to as resin A. The active ingredient of resin A is 66
%.

(m) Into the same reactor as in (II) above, 1650 g of the reaction intermediate [A] obtained in CI) and *L/71000
g was weighed out, heated to 100° C., and 85 g of jetanolamine and 30 g of heptanoethanolamine, which had been separated into a liquid dropping device, were added dropwise over 30 minutes.

Thereafter, the temperature was maintained at 120°C for 2 hours to complete the reaction. The obtained reaction product is referred to as resin B. The active ingredient of Resin B was 63%.

O curing agent (I) 250 parts of 4,4-diphenylmethane diisocyanate and 50 parts of diisobutyl ketone were placed in a reaction vessel equipped with a thermometer, a stirring device, and a reflux condenser, and after uniformly stirring and mixing, ethylene glycol 7/ 184 parts of ethyl ether was added and reacted at 90° C. for 2 hours and then at 110”C for 3 hours to obtain a completely urethanized curing agent a. The active ingredient of curing agent a was 89%.

(IT) Take 222 parts of isophorone diisocyanate in a reaction vessel equipped with a thermometer, stirrer, and reflux cooling base with a dropping funnel, and add 10 parts of methyl isobutyl ketone to it.
After adding 0 parts and uniformly dissolving, 88 parts of a 50% solution of trimethylolpropane in methyl isobutyl ketone was added dropwise from the dropping funnel into the stirring isoanate solution maintained at 70'C over a period of 1 hour. did. After this, the temperature was maintained at 70"C for another hour, and then at 90°C for 1 hour. Then, 230 parts of n-butyl alcohol was added.
A blocked isocyanate was obtained by reacting at 30°C for 3 hours. This curing agent is referred to as a curing agent. The active ingredient of the curing agent was 7θ%.

In addition, the adhesion test was performed by electrocoating the sample material after phosphoric acid treatment with cationic electrodeposition paint U-50 manufactured by Nippon Paint Co., Ltd. to a film thickness of 20 g, and then using Amirac No. 0 manufactured by Kansai Paint Co., Ltd.
30g of 02 was spray-painted to give a 2-coat coating. Regarding 3-coat painting, after electrodeposition coating, 4 degrees of 5-93 sealer manufactured by Nippon Paint Co., Ltd. and 40 layers of Amirac #8o5 white manufactured by Kansai Paint Co., Ltd. were applied. In the adhesion test, primary adhesion and secondary adhesion were tested. 1st order'! ;? 7
In the test, 100 goblets were carved at 1m intervals on the coating surface of each sample material.

The secondary adhesion test was performed by pasting and peeling adhesive tape on these goblets.
After being immersed in warm water (pure water) for 120 hours, it was taken out, and within 30 minutes thereafter, grooves were cut at 1 mm intervals in the same manner as above, and a ta-adhesive tape was attached to and peeled off from the grooves.

In addition, the corrosion resistance test was conducted as a cycle test with the above as one cycle.
Evaluation was performed using the prescribed cycles shown in Table and Table 2. In addition, the flat sample was tested by making a cross cut at the bottom.

Of the corrosion resistance tests, the corrosion resistance after processing was
Shape Tip angle 80' tip RO
, 5 Bead height 5m sample size 25m x 300m
A sample material processed by a drawbead test at a drawing speed of 200 mm/sin and a pushing force of 500 kg was tested at 75 and 100 cycles.

In addition, regarding the wearability after coating, a cross cut was made after electrodeposition coating, a test was conducted for 100 cycles, the maximum blistering width was measured, and half of the value was used for evaluation. The evaluation criteria for each test result are as follows.

(1) Corrosion resistance of unpainted flat plate, corrosion resistance after processing O: No red rust o+: Red rust less than 5z 0: /l 51 or more and less than 10% o-: /
/ 10χ //2oz//Δ: // 20$
tt5Q% tr×: //'5Q // (2) Erosion resistance after painting O: Blister width less than 0.5ffi-0+:
n 0.5ymm or more L, Omwr ttO
: // 1. Ott 2
．． Q fat layer /10-: /l 2
．． 0 /I 3.0Maro Seal l/to: tt 3. Qtt
5.0 humiliation l/X: /
/ 5. Ott (3) 2-coat and 3-coat adhesion 0: Peeling surface a OX O+: tt Less than 5$ QHz
z5$ or more 10 X ttO-: //
IOX /l 20X //Δ: //
2Q% // 5Q% //X:
tt 5Q%tt (01) The sum of the solid content of cationic base resin and additive is 1
00 parts (Book 2) See Table 3 (t3) See Table 4 (04) The sum of the solid content of the cationic base resin and additive H is 1
00 parts, refer to Table 5 for the amount of solids added (t5) Table 1 (wood l) Mixed part by solid content ratio 5 As can be seen from the examples above, the steel sheet of the present invention has the highest As the upper layer, a film with high crosslinking density and high alkali resistance is obtained using a basic epoxy resin as the base resin, and since the resin is low-temperature curable, it causes deterioration of the chromate film and reduction of Cr. Good corrosion resistance of the chromate film itself can be ensured without any damage.

Regarding corrosion resistance after painting, steel sheets coated with conventional organic composite silicate that are baked at low temperatures (150°C) tend to cause alkali blisters due to the poor alkali resistance of the film, and steel sheets coated with conventional organic composite silicate (260°C) tend to cause alkali blisters.
), the corrosion resistance of the chromate deteriorates, so corrosion from the cut portion progresses from the lateral direction, and blisters are likely to occur.In contrast, in the example of the present invention, the alkali resistance of the film is improved, and Since the chromate film maintains good corrosion resistance, good corrosion resistance after painting is obtained. In addition,
The width of the blisters on Synchro Metal is due to the occurrence of red rust.

Regarding corrosion resistance after processing, conventional organic composite silicates of the low-temperature baking type (150°C) do not have sufficient crosslinking of the film and also have poor alkali resistance, so if the film is partially damaged during processing, phosphate The coating deteriorates due to alkaline degreasing during treatment, resulting in poor corrosion resistance. Furthermore, even high-temperature types have poor corrosion resistance due to deterioration of the corrosion resistance of chromate and damage to the film. On the other hand, in the examples of the present invention, the strength and alkali resistance of the film are improved, and the corrosion resistance of chromate is maintained, so that the film exhibits good corrosion resistance even after processing.

[Effects of the Invention] According to the present invention described above, a high degree of paint adhesion and corrosion resistance can be obtained by forming a resin film that is wl-tight, strong, and has excellent alkali resistance on the uppermost layer. # Since the steel sheet of the present invention can be baked at a low temperature (260°C or less) due to the nature of the resin composition film, the deterioration of the chromate film and the reduction of Cr" due to high temperature baking as in conventional steel sheets are avoided. The chromate film itself maintains good corrosion resistance.In addition, since the steel sheet of the present invention can be manufactured by low-temperature baking, it is possible to improve productivity and reduce energy consumption.
By setting the baking temperature to 150°C or less, preferably 150°C or less, it is possible to manufacture highly corrosion-resistant surface-treated steel sheets made from so-called BH steel sheets that have bake hardenability.

Procedural amendments 3rd to 13th, 1988 (Special, +T office number exists r+
1. Display of the incident 1986 Patent Jaw 212620
No. 2. Name of the invention: Highly Corrosion-Resistant Surface Treated Steel Sheet Kansai Paint Co., Ltd. 4. Amendment by Agent Contents A: The "Scope of Claims" of the present application is corrected as follows.

From line 3 to line 4 on page 8 of the present specification, [base resin/...
......30/70'' is corrected to read ``Base resin: silica weight ratio is 99; 1-3o:roJ.

3. On page 8 of the same book, lines 7 to 188, divide the value by 1. O On page 9 of the same book, line 4, ``zinc-plated steel r1.'' is corrected to ``zinc-based plated steel sheet.''

From line 10 to line 111 of page 11 of the same book, it says, ``In this case......l/3.J'', ``In this case Cr'': Cr'' ratio is 1: Correct it to 1~1:3°.

Otsu 1st medicine 11th member 12th line “Cr” / Cr” J
Correct the statement to "Crs+:Cr@+".

From page 11, line 20 of the same book to page 12, line 1 of Z.
Cr3+/Cr6+"Cr": Cr
'“” I corrected it.

From line 13 to line 144 on page 23 of the g1 letter, "Base resin/silica...50150" is replaced with "Base resin; weight ratio of silica is 99; 1 to 30. ;
"Preferably 90:10 to 50:50."

2 From page 23, line 20 of the same book to page 24, line 1, “
Base resin/silica: 99/IJ is corrected to "Base resin silica = 99: IJ.

10. The 2nd line of page 24 of the same book says r30/70J.
Correct it to 30 near 0 J.

11. Delete S, page 26, line 19 to page 28, line 3.

"In the 121st edition, page 28, lines 4 to 5, the phrase ``In addition to silica and insoluble chromium compounds,'' is corrected to ``In addition to silica.''

/3. The word "have" at the end of the third line on page 29 of the same book is deleted.

From line 16 to line 177 on page 9 of the same edition of the llA circular, the phrase [table t-a, table g 1-b, and table t-c] has been changed to ``table 1-a and table t-b.'' I am corrected.

I, page 29, line 20 of the same book says, ``Table 2-a and 2-
"Table b" should be corrected to "Table 2."

/&, rCra+/Cr6+= on page 0, line 19 of the same circular
2/3, J and l"Cr":Cr"=2:3.
Correct it with J.

/7th Prescription Medicines Page 38, Table 1-a, in the column of resin coating, "Additive I" is corrected to "Additive."

/1. The table (page 46, 1-1) of the same book is revised as shown in the attached sheet.

Correct.

Co/, delete Table 2-b, page 42 of the Ministry of the Ministry of Foreign Affairs.

, 22 Ibid., 43rd member, line 1, ``Additive I'' is corrected to ``Additive.''

3. Delete lines 5 to 7 on page 46 of the same book.

, ``Silica'' in Table 4 on page 45 of the 2nd Circular is corrected to ``Additive.''

Table 5 on page 46 of the same book is deleted.

Claims (3)

[Claims] (1) A chromate film is formed on the surface of a galvanized or zinc alloy plated steel sheet, and on the top of the chromate film, at least one basic nitrogen atom and at least two primary hydroxyl groups are formed at the end of the epoxy resin. A highly corrosion-resistant surface-treated steel sheet comprising a resin composition film containing a polyisocyanate compound added to a base resin. (2) A chromate film is formed on the surface of a galvanized or zinc alloy plated steel sheet, and on the top of the chromate film, at least one basic nitrogen atom and at least two primary hydroxyl groups are formed at the end of the epoxy resin. A highly corrosion-resistant surface treatment comprising a resin composition film containing a polyisocyanate compound and silica with a base resin/silica weight ratio of 99/1 to 30/70 on a base resin. steel plate. (3) A chromate film is formed on the surface of a zinc-plated or zinc alloy-plated steel sheet, and on the top of the chromate film, at least one basic nitrogen atom and at least two primary hydroxyl groups are formed at the end of the epoxy resin. A polyisocyanate compound, silica with a base resin/silica weight ratio of 99/1 to 30/70, and a base resin/insoluble chromium compound weight ratio of 99/70 are added to the base resin.
A highly corrosion-resistant surface-treated steel sheet comprising a resin composition film containing an insoluble chromium compound in a ratio of 1 to 60/40.