JP2002275641A - Surface treated steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a chromium-free steel sheet which is a surface treated steel sheet used for a food can, a beverage can, an 18L can, a pale can, or the like, and has excellent adhesion for a coating material, corrosion resistance after coating and rust resistance in particular. SOLUTION: The surface of the steel sheet or the surface of a prescribed Fe-Ni alloy layer formed on the steel sheet is provided with a composite film containing tannate and Si whose coating weight is 0.05 to 250 mg/m<2> , and having a thickness of 5 to 8,000 Å.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a food can, a beverage can,
The present invention relates to a surface-treated steel sheet used for 18L cans, pail cans, etc., and particularly to a chrome free steel sheet for cans having excellent paint adhesion, corrosion resistance after painting, and rust resistance.

[0002]

BACKGROUND ART Tin-plated (tin-plated steel) and tin-free steel (TFS) have been conventionally used as surface-treated steel sheets for cans.
Is widely used. In general, tin-plated steel sheets are subjected to a chemical conversion treatment by applying tin plating to a tinplate original sheet and then immersing in a dichromic acid solution or electrolyzing in this solution. The chromium oxide film formed on the layer has a function of preventing the growth of Sn oxide and improving the adhesion to paint and the rust resistance. In addition, TFS is a surface-treated steel sheet on which chromium metal and chromium hydrated oxide are precipitated.
Since it is possible to satisfy the required performance of cans, such as rust resistance and corrosion resistance after painting, in a well-balanced manner, beverage cans, 18L
Used in a wide range of applications such as cans.

[0003] However, due to recent environmental problems, movements to regulate chromium are progressing in various fields, and the demand for chromium-free surface-treated steel sheets for cans is increasing day by day.

[0004] As a technique for making chromium-free surface-treated steel sheets for cans, tin-plated steel sheets include, for example,
No. 55-24516 discloses that a tin-plated steel sheet is subjected to DC electrolysis in a phosphoric acid-based solution as
There is a disclosure of a surface treatment method for a tin-plated steel sheet having a conversion coating containing no Cr, and Japanese Patent Publication No. 1-32308 discloses that a chemical conversion coating contains P or P and Al to contain Cr. There is disclosed an electroplating tinplate for a seamless can in which a chemical conversion coating is applied to the surface of a tin plating layer. further,
As a surface treatment agent, Japanese Patent Publication No. 58-41352 discloses a liquid system containing a phosphate ion, a tin ion, and a chlorate as a treatment agent after DI processing of a drawn ironing tin (DI can) of a tin-plated steel sheet. Have been.

[0005] However, when the performances such as paint adhesion and rust resistance are comprehensively observed, any of the chemical conversion coatings described in the above-mentioned publications and the chemical conversion coatings manufactured by using the surface treatment agents are as follows.
It cannot be said that the above performance is sufficiently obtained as compared with a chemical conversion film formed by a conventional dichromic acid solution.

[0006] On the other hand, there is no document or the like relating to chrome-free technology that can substitute for TFS.

The requirements for surface-treated steel sheets for cans include:
In addition to the above-mentioned chromium-free, cost reduction as a material for cans can be mentioned. Particularly in tin-plated steel sheets, since tin is an expensive metal, reduction in the amount of tin plating has been promoted. Tin-free steel is often used as a material for cans as a steel plate that does not use tin. However, it is not preferable to use tin-free steel as a material for cans because of the requirement for chromium-free. Therefore, it is strongly desired to develop a new surface-treated steel sheet that does not contain both tin and chromium components.

By the way, a tin-plated steel sheet can exhibit excellent corrosion resistance by sacrificial corrosion protection of tin.
The FS utilizes the fact that the hydrogen overvoltage of the metal chromium layer is large, thereby suppressing the elution of iron and improving the corrosion resistance.

Therefore, when developing a surface-treated steel sheet that does not contain tin and chromium as a substitute for a tin-plated steel sheet or TFS, the above-mentioned anti-corrosion function is imparted to the upper coating of the cold-rolled steel sheet, It is useful to balance performance such as corrosion resistance and paint adhesion.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a film formed on the surface of a steel sheet, which has an effect of improving the film characteristics, but which is not desirable due to environmental problems, An object of the present invention is to provide a low-cost surface-treated steel sheet which does not contain Sn and has excellent paint adhesion, post-paint corrosion resistance and rust resistance.

[0011]

The present invention will be described below in more detail. It is extremely difficult to form a conversion coating containing no Cr on cold-rolled steel sheets to satisfy all of the main properties of steel sheets for cans: paint adhesion, corrosion resistance after coating, and rust resistance. Few examples have been used.

Accordingly, the present inventors have conducted intensive research on a new coating on a cold-rolled steel sheet as a chromium-free technique that can substitute for TFS. The cold-rolled steel sheet is immersed or sprayed in a chemical conversion treatment solution containing a tannic acid for forming a silane coupling agent that contributes to improving paint adhesion, or sprayed,
By forming a composite film on the cold-rolled steel sheet, it has been found that all of paint adhesion, post-paint corrosion resistance and rust resistance can be satisfied at a high level in a well-balanced manner.

Further, by forming an Fe-Ni alloy layer on the surface of the steel sheet and forming the composite coating on the Fe-Ni alloy layer, all of the above-mentioned performances can be satisfied at a higher level in a well-balanced manner. I found that I can do it.

That is, the composite film is formed by etching the surface of the steel plate or the surface of the Fe—Ni alloy layer with phosphoric acid, and then forming a stable passive state formed by tannic acid causing a chelate reaction with iron on the surface of the steel plate. A composite film of a film and a silane film formed by reacting the silane coupling agent with the surface of the passivation film or the surface of the steel sheet, and by the silane film, to improve the adhesion with the paint; The rust resistance is improved by suppressing the barrier effect and the cathodic reaction by the oligomer film formed by the self-condensation reaction, and the synergistic effect of both the passive film and the silane film provides the above performance. They found that everything could be satisfied at a higher level in a well-balanced manner.

Further, in the case of a steel sheet having an Fe-Ni alloy layer, tannic acid reacts with both Fe and Ni,
A stable composite passive film composed of iron tannate and nickel tannate is formed.The composite film composed of the stable film and the silane film forms a dense film and has a high hydrogen overvoltage like a chromium layer in TFS. It was found that the film was a film, and as a result, elution of Fe was suppressed, and the paint adhesion, post-coating corrosion resistance and rust resistance were dramatically improved.

The surface-treated steel sheet of the present invention has a thickness of preferably 10 to 5000 ° and Ni / (Ni + F) on the surface of the steel sheet or on the Fe—Ni alloy layer formed on the surface of the steel sheet.
e) On the Fe-Ni alloy layer having a mass ratio of 0.02 to 0.90,
The thickness is 5 to 8000 mm, the tannate and the amount of adhesion are 0.
It is characterized in that it is a composite film containing Si in the range of 05 to 250 mg / m ² .

The term "composite film" as used herein means a tannate formed by the reaction of the steel sheet surface with tannic acid and a hybrid layer of silane formed by the reaction of the steel sheet surface with the silane coupling agent; It is formed of a laminate in which a silane film formed by a reaction between the passive film and the silane coupling agent is present on the passive film composed of the tannate. That is, the composite film is the composite layer and / or the laminate. Further, it is preferable that the composite film is formed by a chemical conversion treatment solution containing tannic acid and a silane coupling agent.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The reason why the surface-treated steel sheet of the present invention is limited to the above configuration will be described in detail below.

(1) The thickness of the composite film should be 5 to 8000 mm. If the thickness of the composite film is less than 5 mm, sufficient corrosion resistance and rust resistance after painting cannot be obtained. 8000Å
This is because, when it exceeds, film defects increase and sufficient paint adhesion cannot be obtained. The thickness of the composite film is μ-
It can be measured by analyzing the depth direction of C by AES (micro Auger electron spectroscopy).

(2) The composite film contains a tannate and Si having an adhesion amount of 0.05 to 250 mg / m ^{2. The} composite film has a tannate and an adhesion amount of 0.05 to 250 mg / m ^2.
/ M ² . That is, if the amount of Si contained in the composite film is more than 250 mg / m ² , water is adsorbed to unreacted silanol groups,
This is because the paint adhesion (secondary adhesion) is not sufficiently obtained, and the coating film is peeled off.
If it is less than m ² , the effect of improving paint adhesion and corrosion resistance (rust resistance) will not be recognized. The Si is preferably Si derived from a silane coupling agent.
The amount of Si attached can be measured by surface analysis using fluorescent X-rays.

The composite coating may be formed directly on the surface of the cold-rolled steel sheet as described above. However, if it is necessary to satisfy the above performance at a higher level in a well-balanced manner, It is preferably formed on the Fe-Ni alloy layer formed on the surface. Further, the Fe-Ni alloy layer includes
The thickness is 10-5000mm and the mass ratio of Ni / (Ni + Fe) is 0.02
Preferably it is ~ 0.90.

(3) A composite film is formed on the surface of the steel sheet and has a thickness of 10 to 5000 ° and a mass ratio of Ni / (Ni + Fe) of 0.02.
Forming on the surface of Fe-Ni alloy layer having a thickness of ~ 0.90 The composite film is preferably formed on the surface of the Fe-Ni alloy layer formed on the steel sheet surface. This is because tannic acid reacts with the surface of the material to be treated and forms a composite film composed of iron tannate and nickel tannate as a tannate generated.This composite film has a large hydrogen overpotential and a large hydrogen overvoltage. This is because it has a function of suppressing elution.

When forming an Fe—Ni alloy layer on the surface of a steel sheet,
It is preferable that the thickness of the Fe—Ni alloy layer be 10 to 5000 °. When the thickness is less than 10 mm, the effect of suppressing Fe elution is small, and when the thickness exceeds 5000 mm, the effect of suppressing Fe elution is sufficient, but the Fe-Ni alloy layer is hard. This is because it has the property of being brittle, so that cracks easily enter the Fe—Ni alloy layer, and iron elution from such cracks easily occurs. The thickness of the Fe-Ni alloy layer was determined by Ni-AES (micro Auger electron spectroscopy).
Can be measured by depth analysis.

The composition of the Fe—Ni alloy layer is Ni
/(Ni+Fe)=0.02 to 0.90. When the mass ratio is less than 0.02, the effect of alloying due to the inclusion of Ni in the Fe-Ni alloy layer is not remarkable, and the effect of suppressing Fe elution becomes insufficient.In addition, a chelate reaction with tannic acid This is because the proportion of nickel tannate generated by the above-mentioned process also decreases, and the effect of improving corrosion resistance decreases. On the other hand, if the mass ratio exceeds 0.90, the immersion potential of the Fe—Ni alloy layer becomes close to noble Ni, and the effect of suppressing the elution of base Fe cannot be sufficiently obtained. In addition, Ni
/ (Ni + Fe) mass ratio is obtained by analyzing the depth direction of Fe and Ni by μ-AES, integrating the peak value and the multiplier of the relative sensitivity coefficient with respect to the depth, and calculating the integrated value of Ni / (integration of Ni Value + integrated value of Fe).

From the above, according to the present invention, the thickness of Ni / (Ni) is preferably 10 to 5000 ° on the surface of the steel sheet or on the surface of the Fe—Ni alloy layer formed on the steel sheet.
+ Fe) on the surface of the Fe-Ni alloy layer having a mass ratio of 0.02 to 0.90, a thickness of 5 to 8000 mm, a tannate,
By having a composite film containing Si of 0.05 to 250 mg / m ² , preferably a composite film formed by a chemical conversion treatment solution containing tannic acid and a silane coupling agent, particularly, paint adhesion, corrosion resistance after coating and The company succeeded in developing a surface-treated steel sheet having excellent properties in all rust resistance properties.

Next, an example of a specific method for producing a surface-treated steel sheet according to the present invention will be described. After electrolytic degreasing of steel sheet,
After performing a 1% skin pass, electrolytic degreasing and pickling are performed, and a chemical conversion treatment is performed under the conditions described below, whereby a surface-treated steel sheet can be manufactured. When forming a Fe-Ni alloy layer on a steel sheet, the steel sheet is electrolytically degreased, then Ni-plated or Fe-Ni alloy-plated, and subsequently 10% H
_After performing a heat treatment in a gas atmosphere of ₂ + 90% N ₂ to form a Fe—Ni alloy layer, further performing a 1% skin pass, performing electrolytic degreasing and pickling, and then performing a chemical conversion treatment under the conditions described below. , A surface-treated steel sheet can be manufactured.

As a method of forming the Fe—Ni alloy layer,
Industrially, for example, any of the following methods (a) to (c) may be employed. (a) A method of applying Ni plating on the steel sheet surface and then heat-treating it in a non-oxidizing atmosphere to diffuse all the Ni plating into the steel. (b) Applying a Fe-Ni alloy plating on the steel sheet surface, Method to diffuse part or all of Fe-Ni alloy plating by heat treatment in neutral atmosphere (c) Method of applying Fe-Ni alloy plating to steel sheet surface

In the present invention, the above methods may be used alone or in combination of two or more, and further, various compositions,
For example, the Fe—Ni alloy layer can be formed so as to have a gradient composition in which the composition ratio of Fe and Ni gradually changes in the depth direction.

The chemical conversion treatment liquid preferably contains phosphate ions, tannic acid and a silane coupling agent, and more specifically, phosphoric acid or sodium phosphate, aluminum phosphate, potassium phosphate and the like. A mixture of pure metal and a metal salt or monohydrogen phosphate, tannic acid, and a silane coupling agent may be used. Further, in order to form a stable passive film by a chelating reaction of tannic acid, it is preferable to mix an etching agent containing chlorate ions or the like in the chemical conversion treatment liquid.

The concentration of phosphate ions in the chemical conversion treatment solution is 0.
It is preferably from 2 to 20.0 g / l. The concentration is 0.2 g / l
If the amount is less than the above, the etching action is insufficient and the formation of the composite film becomes non-uniform, and if the above concentration exceeds 20.0 g / l, the stability of the chemical conversion treatment solution decreases.

The concentration of tannic acid in the chemical conversion treatment solution is 0.5
It is preferably from 10 to 10 g / l. If the concentration is less than 0.5 g / l, a sufficient reaction with the material to be treated does not take place, and there is a possibility that a stable tannate may not be obtained. This is because the treatment liquid tends to be unstable and the surface of the material to be treated tends to be blackened.

The concentration of the silane coupling agent in the chemical conversion treatment liquid is preferably 0.05 to 10.0 mass%. If the concentration is less than 0.05 mass%, the effect of improving the paint adhesion is reduced, and if the concentration exceeds 10.0 mass%, water is adsorbed to unreacted silanol groups, so that the paint adhesion (2 This is because there is a possibility that sufficient secondary adhesion may not be obtained.

Examples of the silane coupling agent include 3-methacryloxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2- (amino Ethyl) 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-mercaptopropyl Trimethoxysilane, 3-chloropropyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, and the like can be used. Particularly, in the general chemical formula of the silane coupling agent, X in X-Si- _OR2or3 2- with epoxy group
(3,4-epoxycyclohexyl) ethyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane can be uniformly dissolved in a phosphoric acid-based chemical conversion treatment solution, and the effect of improving paint adhesion and corrosion resistance is increased. It is suitable.

The pH of the chemical conversion solution can be adjusted to 1.5 by using sodium hydroxide or potassium hydroxide.
It is preferably in the range of 5.5 to 5.5. If the pH is adjusted to the range of 1.5 to 5.5, the silane coupling agent can be uniformly dissolved in the chemical conversion treatment solution, and excellent paint adhesion can be obtained, and when the pH is outside the above range. This is because the silane coupling agent cannot be uniformly dissolved in the chemical conversion treatment liquid, and the effect of improving the paint adhesion may not be sufficiently obtained.

The chemical conversion treatment conditions are as follows: a temperature of 40 to 60 ° C. The treatment (immersion) time is preferably set to 1 to 30 seconds. The steel sheet after the immersion treatment is preferably dried with warm air at 50 to 130 ° C. That is, when the drying temperature is lower than 50 ° C., the dehydration condensation reaction between the —OH group on the surface of the material to be processed and the silanol group generated from the silane coupling agent does not occur, so that a composite film containing silane is not formed properly. Because there is a possibility that
Further, if the drying temperature is higher than 130 ° C., no problem occurs with respect to the paint adhesion, but the discoloration of the steel sheet becomes easier. Roll squeezing may be performed after immersion in the chemical conversion treatment solution in order to control the amount of the composite film attached.

The above is merely an example of the embodiment of the present invention, and various changes can be made within the scope of the claims.

[0037]

Next, an embodiment of the present invention will be described in detail below.・ Examples 1 to 25 After a T4 original plate having a thickness of 0.22 mm was electrolytically degreased, Examples 1 to 23 were performed.
For Ni, Ni plating and annealing at 700 ° C. in a mixed gas atmosphere of 10% H _{2 and} 90% N ₂ were performed to diffuse and infiltrate Ni in the Ni plating into the steel sheet. For No. 25, after performing temper rolling at a rolling reduction of 1.5% without performing Ni plating and diffusion treatment, degreasing and pickling were performed, and then a composite film was formed under the chemical conversion film forming conditions shown in Table 1. .

Comparative Examples 1 to 4 For comparison, surface-treated steel sheets having chemical conversion film conditions outside the proper range were also manufactured.

[0039]

[Table 1]

(Evaluation of Performance) Examples 1 to 25 and Comparative Examples 1 to 4
Each of the surface-treated steel sheets was evaluated for paint adhesion, rust resistance, and corrosion resistance after painting.

(1) Paint Adhesion Paint adhesion was evaluated by the following test method. An epoxyphenol-based paint having an adhesion amount of 50 mg / dm ² was applied to the surface of each of the surface-treated steel sheets, and baked at 210 ° C. for 10 minutes. Next, after laminating the two coated and baked steel sheets so that the coated surfaces face each other with the nylon adhesive film interposed therebetween, the pressure was 2.94 × 10 ⁵ Pa,
Temperature 190 ° C. Bonding under crimping conditions of crimping time 30 seconds,
Thereafter, this was divided into test pieces having a width of 5 mm, and the test pieces were subjected to strength measurement using a tensile tester, and the primary paint adhesion was evaluated from the measurement results. Another test piece is 55 ℃
Was immersed in a 1.5% by mass of NaCl + 1.5% by mass citric acid solution for 7 days, and then the secondary paint adhesion was evaluated from the results of strength measurements similarly performed using a tensile tester. Table 2 shows the evaluation results. In Table 2, "◎" indicates that the measured strength per 5 mm width of the test piece was 68.8 [N] or more, and 49.0 [N] or more
When the value is less than 8.6 (N), it is `` ○ '', 29.4 (N) or more, 49.0 (N)
Less than “△” and less than 29.4 [N] “×”
As shown.

(2) Rust resistance Each of the surface-treated steel sheets was subjected to a high humidity state at a temperature of 50 ° C. and a relative humidity of 98%, and a dry state at a temperature of 25 ° C. and a relative humidity of 60%.
It was exposed to an environment that alternated every minute, and the number of days until rust was generated on the surface was examined, thereby evaluating rust resistance. Table 2 shows the evaluation results. In Table 2, "○" indicates that no rust was observed for 30 days or more,
"△", if it is recognized for 15 days or more and less than 30 days,
The case where the generation of rust was observed in less than 15 days is indicated by "x".

(3) Corrosion resistance after coating An epoxyphenol-based paint having an adhesion amount of 50 mg / dm ² was applied to the surface of each surface-treated steel sheet, and baked at 210 ° C. for 10 minutes. Seal the end face and the back face, put a cross cut on the painted face, immerse in a 1.5% NaCl + 1.5% by mass citric acid solution at 55 ° C for 4 days, wash with water, dry, peel off the tape, The peel width was measured, and the corrosion resistance after coating was evaluated accordingly. Table 2 shows the evaluation results. In Table 2, when the peel width is 0.1 mm or less, “○”, when the peel width is more than 0.1 mm and less than 0.2 mm, “△”, and 0.2 m
The case of m or more is indicated as “×”.

[0044]

[Table 2]

As is clear from the results in Table 2, Example 1
Nos. 25 to 25 were all excellent in paint adhesion, rust resistance and corrosion resistance after coating. On the other hand, Comparative Examples 1 to 4 in which the conditions of the chemical conversion film were out of the appropriate range were poor in any of the paint adhesion, rust resistance, and corrosion resistance after painting, indicating that they were not at a practical level.

[0046]

Industrial Applicability The present invention provides a chemical conversion coating formed on a steel sheet, preferably a steel sheet having an Fe-Ni alloy layer, which has an effect of improving the film properties, but is not desirable due to environmental problems. In particular, it is possible to provide a surface-treated steel sheet having excellent paint adhesion, rust resistance, and corrosion resistance after painting without containing Cr or expensive Sn. Further, the surface-treated steel sheet of the present invention also has an effect of reducing costs as compared with conventional tin-plated steel sheets and TFS.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Chiaki Kato 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term in the Technical Research Laboratory, Kawasaki Steel Co., Ltd. 4K026 AA02 AA11 AA22 BA03 BB06 BB08 CA13 CA23 DA03 EA01 EA06 EA17

Claims (4)

[Claims] Claims: 1. A steel sheet having a thickness of 5 to 8000 mm, a tannate and an adhesion amount of at least 0.05 to at least one surface of a steel sheet.
A surface-treated steel sheet having a composite film containing 250 mg / m ² of Si. 2. The surface-treated steel sheet according to claim 1, wherein the composite film is formed by a chemical conversion treatment solution containing tannic acid and a silane coupling agent. 3. The method according to claim 1, wherein the steel sheet has a Fe—
The surface-treated steel sheet according to claim 1, further comprising a Ni alloy layer. 4. The Fe—Ni alloy layer has a thickness of 10 to 5000 °.
The surface-treated steel sheet according to claim 3, wherein the mass ratio of Ni / (Ni + Fe) is 0.02 to 0.90.