JP2000248376A - Surface treated steel sheet for fuel container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treated steel sheet for a fuel container good in the adhesion of a film, spot weldability and corrosion resistance to deteriorat ed gasoline as well. SOLUTION: The surface of a galvanizing film is provided with a composite film of 3 to 15 μm thickness contg. one or more kinds among the groups of the metal powder composed of Ni, Ni alloys, Cr, Cr alloys, Ni stainless steel and Cr stainless steel of 0.5 to 10 μm average particle size by 12 to 30 wt.% in total and one or more kinds among the groups of neutralizers composed of borates, carbonates and alkali pigment by >=12 wt.% in total and also in the range in which the total content with the metal powder is controlled to <=60 wt.%, and the balance substantially any of an epoxy, acrylic urethane, polyester, phoenolic, urea, melamine, unsaturated polyester and alkyd resins and ebonite. The plating film of the galvanizing steel sheet more preferably contains 0.2 to 10 wt.% Co and 0.5 to 5.0% polymeric organic matter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated steel sheet for a fuel container having excellent corrosion resistance and suitable as a material for a fuel container mainly composed of gasoline.

[0002]

2. Description of the Related Art In a fuel container mainly composed of gasoline used for an automobile or the like, it is important to have a corrosion resistance against gasoline on an inner surface of the container and a corrosion resistance on an outer surface of the container. The material is required to have good moldability, weldability, solderability, paintability, and the like. As a material satisfying such requirements, a Pb-Sn alloy-plated steel sheet called a turn sheet has been widely used.

[0003] Fossil fuels or alcohol fuels are oxidized and deteriorated by the influence of the atmosphere and moisture during storage, and may contain organic acids (hereinafter such fuels are referred to as "degraded gasoline"). . It has been found that deteriorated gasoline is more corrosive than gasoline containing no organic acid and the like, and a steel sheet having good corrosion resistance to such deteriorated gasoline has been required. Further, in recent years, the influence of lead on the environment has been considered, and a material containing no lead has been demanded as a material for a fuel container.

Japanese Unexamined Patent Publication No. Hei 8-269733 discloses that a lead-free rust-preventive steel plate for a fuel tank contains 4 Sn.
A Sn-Zn alloy plated steel sheet containing 0 to 99% by weight and the balance being Zn is disclosed. This steel sheet was an alloy-plated steel sheet, and was considered to have a good balance of corrosion resistance on the inner surface of the container, corrosion resistance on the outer surface, weldability, and the like.

[0005] Japanese Patent Application Laid-Open No. 9-156027 discloses a rust-proof steel plate for a fuel tank which does not use lead having excellent corrosion resistance even in an environment in which gasoline is oxidized and degraded.
A hot-dip Al-plated steel sheet containing i, Fe, and the like is disclosed.

Japanese Patent Application Laid-Open No. 10-137681 discloses a steel plate for a fuel tank which has improved corrosion resistance to highly corrosive fuel and has good formability. This was provided with a resin film in which Ni powder and aluminum flakes were dispersed on one surface and a resin film containing silica and wax on the other surface on a Zn-based plating film having a chromate film. It is a steel plate. In this steel sheet, Ni powder and flake-like aluminum flakes
It physically blocks the permeation of organic acids contained in deteriorated gasoline, and suppresses the corrosion of the steel sheet inside the container by the shielding action.

[0007]

In many cases, steel plates for fuel containers are subjected to severe forming during processing. In this case, the plating layer on the surface of the steel plate is damaged by a mold or cracks are formed in the plating layer. May occur. JP-A-8-269733
No., the Sn-Zn alloy plated steel sheet described in
While Zn is present in the plating layer, the corrosion resistance is ensured by the sacrificial corrosion protection effect of Zn. However, since the Sn plating layer is more noble in potential than the iron substrate, the corrosion of the iron substrate occurs after the Zn of the plating layer elutes. Begins. For this reason, the steel plate described in the above-mentioned publication has a problem that the corrosion resistance of the material for a fuel container having a high corrosive property is insufficient when the plating layer is damaged during processing.

The problem that the aluminum-plated steel sheet disclosed in Japanese Patent Application Laid-Open No. 9-156027 is not necessarily good in terms of bondability such as welding and soldering because the melting point is 200 ° C. or more higher than that of zinc. There is.

[0009] In the steel sheet disclosed in Japanese Patent Application Laid-Open No. 10-137681, when severe shaping is performed during processing and peeling of the coating film or falling off of metal powder occurs, the shielding effect of the organic acid is small. And the corrosion resistance may not be sufficient. Further, the electric resistance of the film may be high and the weldability may not be sufficient.

An object of the present invention is to solve these problems, to contain no lead, to have excellent corrosion resistance to degraded gasoline, to have good adhesion of the coating during processing, and to have stable weldability.
Another object of the present invention is to provide a surface-treated steel sheet for a fuel container which is excellent in economic efficiency.

[0011]

Means for Solving the Problems The present inventors have conducted intensive studies on a method of improving the corrosion resistance to deteriorated gasoline, and have obtained the following new findings.

When the stored gasoline is oxidized by reacting with the atmosphere or moisture, an organic acid such as formic acid or acetic acid is generated, resulting in a severe corrosive environment for the container material. However, by providing a coating containing a substance having a neutralizing effect on these organic acids on the surface of the container material and causing a neutralization reaction with the organic acids generated during gasoline deterioration, the hydrogen ion concentration in the fuel is reduced. Thus, corrosion of the container material can be suppressed.

Examples of the neutralizing agent include borates or carbonates which are weaker than these organic acids (hereinafter, also simply referred to as "salts"), or alkaline pigments such as zinc cyanamide, magnesium oxide and potassium oxide. And so on.
Further, these salts or alkaline pigments (hereinafter collectively referred to as "neutralizing agent") are preferably provided on the plating film surface as a composite film using a resin film as a binder.

In order to maintain and improve the weldability of a steel sheet having a resin film, it is preferable that the resin film contains an appropriate amount of metal powder having conductivity and low reactivity to organic acids and moisture. When the metal powder is contained, the adhesiveness of the film at the time of molding can be maintained by setting the average particle size to a specific range. Further, by setting the amount of the composite film to be in a range corresponding to the thickness of 3 to 15 μm, the deteriorated gasoline corrosion resistance and weldability of the inner surface of the container can be exhibited in a comprehensively well-balanced manner.

As the plating film is excellent in economy, Z
An n-based plating film is preferred. In particular, when a plating film containing a relatively small amount of Zn and a high molecular weight organic material represented by dextrin, dextran or the like is used in Zn, not only the excellent corrosion resistance required on the outer surface of the fuel container is ensured, but also the container Corrosion resistance to degraded gasoline on the inner surface can be further improved.

The effects of Co, dextrin and dextran have not been elucidated in detail yet, but the following mechanism of the performance is presumed. The high molecular organic substance added to the plating bath is taken into the plating film when forming the plating film, and at this time, there is an effect of making zinc crystals fine. These finely divided crystals produce fine corrosion products in a corrosive environment. This fine corrosion product has a greater environmental barrier effect than the coarse corrosion product. Further, it is expected that the high-molecular organic matter taken into the plating film is eluted in the corrosive environment, and the corrosion product is miniaturized.

On the other hand, the effect of Co, as an alloy element, is to make the plating film slightly noble, to improve bare corrosion resistance,
In collaboration with high molecular organic substances, the above corrosion products can be refined
It is thought to contribute to stabilization. Further, since the plating film is hardened, the sliding characteristics at the time of press working and the continuous spot welding property of spot welding are improved.

The present invention has been completed based on these findings, and the gist of the present invention is a surface-treated steel sheet for a fuel container described in the following (1) to (3).

(1) Metal powder group consisting of Ni, Ni-based alloy, Cr, Cr-based alloy, Ni-based stainless steel and Cr-based stainless steel having an average particle size of 0.5 to 15 μm on a Zn-based plating film One or two or more of
2 to 30% by weight, and a total of 12% by weight or more of one or more of a neutralizing agent group consisting of a borate, a carbonate and an alkaline pigment having an average particle size of 0.5 to 10 μm, and It is contained in a range where the total amount with the metal powder is 60% by weight or less, and the balance is substantially made of resin.
A surface treated steel sheet for a fuel container, comprising a μm composite coating.

(2) The resin which is a component of the composite film is
Epoxy resin, acrylic resin, urethane resin, polyester resin, phenolic resin, urea resin, melamine resin, unsaturated polyester resin, alkyd resin, ebonite The surface-treated steel sheet for a fuel container according to (1).

(3) The Zn-based plating film contains 0.2% of Co.
The fuel container according to the above (1) or (2), characterized in that the fuel container contains from 10 to 10% by weight, from 0.5 to 5.0% by weight of a polymer organic substance, and the balance substantially consists of Zn. Surface treated steel sheet.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail. In addition, the following percentages of the chemical composition mean% by weight.

Plating base material: The type of plating base material is not particularly limited, but a commonly used cold-rolled steel sheet is preferable.
In many cases, fuel containers have complicated shapes and are subjected to rigorous forming processing.
An ultra-low carbon steel sheet containing i, Nb, B and the like is preferable. However, the present invention is not limited to this, and a hot rolled steel plate or the like may be used depending on the shape of the container.

Plating film: The plating film is Zn plating or Zn-based alloy plating. In the present invention, these are simply referred to as Zn-based plating. As alloying elements to be contained in the Zn-based alloy plating, Co, Al, Al-Si, Ni,
Fe, Cr, Mg, Sn and the like are suitable. Among them, Co
Is preferable to be a Zn-Co alloy plating containing 0.2 to 10%. If the Co content is less than 0.2%, the effect of improving the corrosion resistance by incorporating Co is not sufficient.
Co is expensive, and if its content exceeds 10%, the effect of improving corrosion resistance is saturated. Therefore, when Co is contained, the content is preferably 10% or less. When Al is contained as an alloy element, the Al content is preferably not more than 60%.

[0025] 0.5 to 0.5% of the weight of the plating film
If 5.0% of a high molecular weight organic material is co-deposited in the plating film, the corrosion resistance of the plating film is further improved. If the content of the organic polymer in the plating film is less than 0.5%, the effect of improving the corrosion resistance is not sufficient. If the content of the high molecular organic substance exceeds 5.0%, the effect of improving corrosion resistance is saturated, and more gas is generated at the time of welding, which is not preferable because the weldability of the plated product is impaired.

As the high molecular organic substance, any one of amylopectin, which is a component of starch, and dextrin or dextran obtained by hydrolyzing starch is used.
It is preferable to use species or two or more species. Those having a molecular weight of 10 ³ to 10 ⁹ are preferred. The content of the high molecular organic substance in the plating film can be measured by dissolving the plating film with sulfuric acid or the like, decomposing the high molecular organic substance in the solution into glucose, and then quantifying the amount of glucose by the phenol sulfuric acid method. The molecular weight of the high molecular weight organic substance can be measured by gel permeation chromatography (GPC).

The amount of plating can be arbitrarily determined according to the use environment of the fuel container, etc., but is preferably 10 g / m ² or more per one surface in order to ensure corrosion resistance. More preferably, it is 15 g / m ² or more. Although the upper limit of the amount of plating is not particularly limited, 90 g / m 2 is considered in consideration of damage to the plating film during press molding.
^It is preferably set to ² or less.

Composite film: When the stored fuel reacts with the atmosphere or moisture and is oxidized, organic acids such as formic acid and acetic acid are generated, resulting in a severe corrosive environment for the container material. Therefore, corrosion resistance to deteriorated gasoline is particularly required on the inner surface of the fuel container. By interposing borate, carbonate, or alkaline pigment, which is weaker than these organic acids, as a neutralizing agent on the plating film surface of the steel plate for fuel containers,
These substances cause a neutralization reaction with the organic acid to lower the hydrogen ion concentration in the fuel and suppress the corrosion of the plating film and the steel sheet.

As the borate having such an effect, sodium borate, potassium borate, calcium borate, barium borate, strontium borate and the like can be applied. Further, as the carbonate, formic acid such as sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, barium carbonate, and strontium carbonate, and a salt of an acid which is weaker than acetic acid can be used.

As the alkaline pigment, a pigment which reacts with and neutralizes formic acid and acetic acid can be used, but a lead-containing material is not preferred in view of environmental emission regulations. Therefore, as the alkaline pigment, zinc cyanamide, magnesium oxide, potassium oxide and the like are preferable. These neutralizing agents may be contained alone in the film, or two or more thereof may be mixed and contained.

The content of the neutralizing agent is 12% or more based on the weight of the composite film. If it is less than 12%, the corrosion resistance is not good. It is preferably at least 15%. If the total amount of the neutralizing agent and the metal powder is excessively large, the adhesion of the composite film is impaired. Therefore, the neutralizing agent is contained in a range where the total amount is 60% or less. Preferably, the total amount is 55% or less.

The smaller the average particle size of the neutralizing agent, the higher the cost and the more difficult it is to uniformly disperse it in the coating composition. Therefore, the average particle size is 0.5 μm or more. Preferably it is 3 μm or more. If the average particle size exceeds 10 μm, the neutralizing agent may fall off during molding and the film may peel off, which is not preferable. Therefore, the average particle size is set to 10 μm or less. Preferably it is 8 μm or less.

In order to secure the weldability of the composite coating,
Ni, a Ni-based alloy, Cr, a Cr-based alloy, a Ni-based stainless steel, and a metal powder having an average particle diameter of 0.5 to 15 μm of a total of 12 -30%. These metal powders are rich in conductivity and stable without reacting with moisture or organic acids during coating work or when used as a fuel container, so they do not impair corrosion resistance.

The form of the metal powder is preferably particulate. If the average particle size is too small, the effect of improving the weldability is small and the cost is high. Therefore, the average particle size is 0.5
μm or more. Preferably it is 3 μm or more. The weldability is best when the particle size of the metal powder is slightly larger than the dry film thickness, but if it is too large, it tends to fall off from the composite film during molding and the film may peel off, which is not good . Therefore, the average particle size of the metal powder is set to 15 μm or less. Preferably it is 10 μm or less.

If the content of the metal powder is less than 12%, poor conduction may occur during spot welding, which may cause a problem. In order to avoid this, the content of the metal powder is set to 12% or more in total. It is preferably at least 15%. When the content of the metal powder exceeds 30% in total, the effect of improving spot weldability is saturated, and the metal powder may fall off during molding, and the composite coating may be damaged. In order to prevent this, the content is set to 30% or less. Preferably 25
% Or less.

The remainder of the composite coating consists essentially of resin.
The main role of the resin in this case is to shield the corrosion promoting components contained in the deteriorated gasoline from the plating film surface,
It acts as a binder for holding the metal powder. Therefore, as the kind of the resin, a resin having a property that the resin itself hardly dissolves, swells or permeates the gasoline component is preferable. In particular, a. Excellent acid resistance and solvent resistance, b. Excellent film ductility that affects film adhesion during press molding,
c. A resin having characteristics such as high film hardness is preferable. Further, a thermosetting resin having a high crosslink density of the coating is more suitable than a thermoplastic resin.

As such a resin, an epoxy resin,
Acrylic resins, urethane resins, polyester resins, phenolic resins, urea resins, melamine resins, unsaturated polyester resins, alkyd resins, ebonite and the like are preferred.

The content of the resin is preferably at least 40% based on the weight of the composite film. If it is less than 40%, the binder effect is small and the film adhesion is reduced. It is more preferably at least 50%. The upper limit is preferably set to 76%. If the content exceeds this, the content of salts, zinc cyanamide or metal powder is reduced, and corrosion resistance and weldability may be impaired. It is more preferably at most 70%.

The meaning that the remainder substantially consists of resin is as follows.
In addition to the above, it means that the composite coating may contain 30% or less in total of known coloring pigments, rust preventive pigments, crosslinking agents, and the like. For example, it is common practice to add a crosslinking agent to the main resin to increase the crosslinking density, but in the present invention, these known treatments may be performed.

If the thickness of the composite film is less than 3 μm, the corrosion resistance is not good, so the thickness is 3 μm or more. Preferably it is 5 μm or more. The thickness of the composite film is 1
If the thickness exceeds 5 μm, the spot weldability may be impaired, so the thickness is set to 15 μm or less. Preferably it is 10 μm or less.

The basic constitutional requirements of the surface-treated steel sheet of the present invention are as described above, but a reaction type or coating type chromate-treated film, a zinc phosphate-based or iron phosphate-based film is provided between the plating film and the composite film. Or a known chemical conversion coating such as a so-called non-chromate coating formed of a resin coating containing a silicate or a phosphate compound. The presence of such a treatment film improves the adhesion between the plating film and the composite film, and has the effect of further improving the corrosion resistance of the surface-treated steel sheet.

In the case of processing into a fuel container, severe forming processing is often performed, and it is particularly desirable that the steel plate surface, which is the outer surface of the container, has good lubricity. Therefore, the surface may be provided with a solid lubricating film. As the lubricating film, a film-removable lubricating film that can be removed by alkali degreasing or the like is preferable in order not to impair the subsequent coatability of the outer surface. It is also preferable to apply a rust-preventive oil to the surface or to apply a lubricating oil during molding.

The method for producing the product of the present invention is optional. As a plating method for the base material, any of a hot-dip plating method, an electroplating method, and a vapor deposition plating method may be used. When a high molecular organic substance is contained in the plating film, it is preferable to perform plating by an electroplating method. The electroplating bath at that time includes an acidic bath (eg, a sulfate bath, a chloride bath) and an alkaline bath (eg,
Or an acid bath, particularly a sulfuric acid bath. It is preferable that the plating bath contain a zinc source and a Co source in an amount that achieves a target composition as any one of sulfates, acetates, and carbonates containing these metals.

To make the plating film contain a high molecular organic substance, the electroplating bath contains a water soluble or water dispersible high molecular organic substance. As the high molecular organic substance, it is preferable to use one or more of amylopectin, which is a component of starch, and dextrin or dextran obtained by hydrolyzing starch.

Next, a coating composition containing the resin, the neutralizing agent and the metal powder may be applied to at least one surface of the plating film and dried and baked. These coating operations may be performed using known coating equipment.

[0046]

Example 1 Deep-drawing cold-rolled steel sheet made of ultra-low carbon steel having a thickness of 0.8 mm contains Ni on both sides and the balance substantially consisting of Zn, with the balance being 13%. An electroplated steel sheet provided with Zn-based electroplating having an amount of 30 g / m ² per side was produced. On this electroplated steel sheet, there were prepared a steel sheet test piece having a coating amount of Cr of 60 mg / m ² and subjected to a coating type chromate treatment, and a test piece of an electroplated steel sheet not subjected to a coating type chromate treatment.

A thermosetting urethane-modified epoxy resin having a number average molecular weight of 3 × 10 ⁴ is prepared by adding one kind of a borate, a carbonate and a zinc cyanamide having an average particle diameter of 5 μm as a neutralizing agent. Or two kinds and the average particle size is 10 μm
Was prepared by mixing Ni powder at various ratios.

A dry film thickness of 8 μm was formed on one side of each of the above test pieces.
Was applied and baked at 230 ° C. for 50 seconds to produce a surface-treated steel sheet provided with a composite film. The performance of these surface-treated steel sheets was evaluated by the following method.

Corrosion resistance: A test piece was subjected to deep drawing by the method described later to form a cylinder having a composite coating on the inner surface, and was degreased with an alkali and dried. Then add formic acid to the cylinder
000ppm aqueous solution 10cc and gasoline 20
cc and sealed, and kept at 50 ° C. for 20 days. 2
After 0 day, the degree of turbidity of the liquid inside was measured using a UV-visible spectrophotometer for the transmittance of visible light having a wavelength of 600 nm.
The occurrence of turbidity indicates that the corrosion of the plating film or the steel sheet by the organic acid is progressing. The transmittance was evaluated based on the following criteria, and the corrosion resistance of the test piece was evaluated.

◎ (very good): 90-100% transmittance; ○ (good): 80% or more, less than 90%; Δ (poor): 60% or more, less than 80%; × (extremely poor): Less than 60% transmittance.

Deep drawing conditions: blank diameter: 100 m
m, punch diameter: 50 mm, punch shoulder radius: 5 mm, die hole diameter: 52.5 mm, die shoulder radius: 5 mm, drawing height: 25 mm, lubricating oil used.

Weldability: Surface treated steel sheet 2 provided with composite coating
After laminating the sheets so that the composite film becomes a mating surface, a diameter: 5 mm, a tip shape: using a dome-shaped electrode rod, a pressing force: 300 kgf, a conduction time: 3 Hz / 60.
After performing spot welding under the conditions of Hz, pause time: 2 Hz / 60 Hz, and current of 13 kA, the welded portion was cut, the cut surface was observed using a microscope, and the joining condition was evaluated based on the following criteria.

A: Very good without defects, B: Blow holes with a diameter of less than 0.5 mm are good, B: Blow holes with a diameter of 0.5 mm or more are bad, C: Very poor with unwelded parts.

Adhesion: An adhesive tape was applied to the inner wall surface of the cylinder which was deep drawn by the above method, alkali-degreased and dried, and the adhesive tape was peeled off, and then the composite film or the composite film and the plating film were separated. The adhesion was evaluated by the area ratio. Further, the state of coating damage on the inner and outer surfaces of the cylinder was visually observed.

◎ (extremely good): no peeling, ○ (good): peeling area ratio of 10% or less, Δ (poor): more than 10%, 30% or less, × (extremely poor): more than 30%.

Table 1 shows the composite coating composition of the steel sheet subjected to the test and the results of the performance evaluation.

[0057]

[Table 1]

As can be seen from Table 1, test numbers A5 to A14, A21 to A29 satisfying the conditions specified by the present invention.
All showed good corrosion resistance to deteriorated gasoline, spot weldability, and film adhesion. Those subjected to the chromate treatment had particularly good performance. In contrast,
Test numbers A1 and A2 which did not contain Ni powder and test numbers A3 and A4 whose contents were less than 12% had poor spot weldability. Test numbers A15 to A18
Was not good in corrosion resistance because the content of the neutralizing agent was too small. In Test Nos. A19 and A20, the coating was damaged and peeled off because the total amount of the neutralizing agent and the metal powder was excessive.

Example 2 Zn-55% based on a cold-rolled steel sheet for deep drawing using a 0.8 mm thick ultra-low carbon steel as a base material
Al-plated steel sheet (Amount of coating: 6 on both sides)
0 g / m ² ) and 20 mg / m ^{2 in} metal Cr equivalent.
Was provided with a reactive chromate-treated film having a thickness corresponding to the above.
In order to provide a composite coating for the inner surface of the container, a thermosetting amine-modified epoxy resin having a number average molecular weight of 2.5 × 10 ⁴ was dried at a rate of 60% of the weight of the dried coating by Ni powder (average particle diameter 0.8 μm ) Is 20% based on the film weight after drying,
Sodium carbonate or zinc cyanamide (average particle size is 5 μm in each case) was added to the coating weight after drying by 20%.
% Of the coating composition was applied so as to have a dry film thickness of 2 to 30 μm, and baked at 200 ° C. for 45 seconds. The obtained surface-treated steel sheet was evaluated for corrosion resistance and weldability in the same manner as described in Example 1. Table 2 shows the thickness of the composite coating of the steel sheet subjected to the test and the results of the performance evaluation.

[0060]

[Table 2]

As can be seen from Table 2, when the thickness of the composite film was less than 3 μm, the corrosion resistance to deteriorated gasoline was not sufficient. On the other hand, when the thickness exceeds 15 μm, the weldability is not preferable.

(Example 3) Various zinc-based and aluminum-based plated steel sheets were prepared, degreased by an ordinary method, and then subjected to a coating-type chromate treatment (with an adhesion amount of 50 in terms of metal Cr).
mg / m ² ). Next, as a neutralizing agent, magnesium carbonate having an average particle diameter of 8 μm is 20% by weight of the dried film, Ni powder having an average particle diameter of 11 μm is 20% by weight of the dried film, and the balance is resin, cross-linking agent and An aqueous polyester paint composed of titanium oxide was applied to a dry film thickness of 10 μm and baked at 150 ° C. for 20 minutes. After that, a flaw reaching the base steel plate is applied to the composite coating using a cutter knife, and a salt spray test is performed for 240 hours in accordance with the method specified in JIS-Z2371. However, when the film blister width was less than 4 mm, it was determined that the outer surface of the fuel container had good corrosion resistance. Table 3 shows the results obtained.

[0063]

[Table 3]

As shown in Table 3, the results of the salt spray test were good when a zinc-based plated steel sheet was used. Especially Zn
-The thing using the Co plating steel plate was excellent. In the case of aluminum plating (test number C10) and aluminum alloy plating (test number C11) evaluated for comparison, corrosion resistance was not good.

Example 4 An immersion-type zinc phosphate treatment was applied to both surfaces of an electro-Zn plated steel sheet (coating amount: 50 g / m ² on each of the front and back surfaces), and the adhesion amount was 2 g / m ² each.
Was provided with a zinc phosphate film. The same thermosetting amine-modified epoxy resin as described in Example 2, potassium borate or cyanamide zinc salts having various average particle diameters as a neutralizing agent, and stainless steel having various average particle diameters as metal powder It was mixed and dispersed with steel powder to prepare a coating composition for the inner surface of the container. The coating composition was applied to the above-mentioned immersion-type zinc phosphate-treated electric Zn-plated steel sheet and baked at 240 ° C. for 80 seconds. With respect to the obtained surface-treated steel sheet, film adhesion and weldability were evaluated in the same manner as described in Example 1. Table 4 shows the thickness of the composite coating of the steel sheet subjected to the test and the performance evaluation results.

[0066]

[Table 4]

As shown in Table 4, the neutralizer had an average particle size of 1
In the numbers D1 to D3 exceeding 0 μm and the number D10 in which the average particle size of the metal powder exceeded 15 μm, the neutralizing agent or the metal powder was dropped off during deep drawing and the composite film was damaged.
Good results were obtained in all cases satisfying the condition range defined by the present invention.

Continued on the front page F-term (reference) 4D075 CA13 CA33 DB05 DC13 EB22 EB32 EB33 EB35 EC01 EC10 EC11 4F100 AA02B AA08B AA22 AB03C AB04B AB07 AB13B AB15A AB16B AB18A AB31B AK01A AK01B AK25B BAB AK33BB BAB AK33BB BAK DE01B EH46 EH71A EJ06B EJ69 GB16 JA20B JB02 JB13B JG10 JK06 YY00B 4K044 AA02 BA10 BA21 BB11 BC02 CA11 CA13 CA18 CA22 CA27 CA62

Claims (3)

[Claims] 1. A metal powder group consisting of Ni, Ni-based alloy, Cr, Cr-based alloy, Ni-based stainless steel and Cr-based stainless steel having an average particle size of 0.5 to 15 μm on a Zn-based plating film. One or two or more of
And 30% by weight, and a total of 12% by weight or more of one or more of a neutralizing agent group consisting of a borate, a carbonate and an alkaline pigment having an average particle size of 0.5 to 10 μm; It is contained in a range where the total amount with the metal powder is 60% by weight or less, and the balance is substantially made of resin.
A surface-treated steel sheet for a fuel container, comprising: 2. The resin which is a component of the composite film is an epoxy resin, an acrylic resin, a urethane resin, a polyester resin, a phenol resin, a urea resin, a melamine resin, an unsaturated polyester resin, an alkyd resin, an ebonite. The surface-treated steel sheet for a fuel container according to claim 1, comprising a resin selected from the group consisting of: 3. The Zn-based plating film contains Co in an amount of 0.2 to 1%.
3. The surface-treated steel sheet for a fuel container according to claim 1, wherein the steel sheet contains 0% by weight and 0.5 to 5.0% by weight of a high-molecular organic substance, and the balance substantially consists of Zn. 4. .