JPH11269663A - Surface treated steel sheet for fuel vessel excellent in corrosion resistance and workability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treated steel sheet for a fuel vessel excellent in corrosion resistance to automotive fuel and outer face corrosive environments as a fuel tank and the peripheral parts thereof and excellent in workability. SOLUTION: At least one side of the surface of a steel sheet is provided with a galvanizing layer of 5 to 80 g/m<2> coating weight as a primary plating layer, and the surface of the primary plating layer is provided with a secondary plating layer of 100 to 1000 mg/m<2> metal Cr and 2 to 30 mg/m<2> Cr hydrated oxide as the content of Cr. The galvanizing layer is composed of Zn, Zn-Fe alloy plating or Zn-Ni alloy plating. Or, only one side is provided with the primary plating layer and secondary plating layer, and the other side is provided with the galvanizing.

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 workability.
The present invention relates to a container for containing and holding so-called automotive fuel such as gasoline, alcohol, or gasoline to which alcohol is added, that is, a fuel tank, and a surface-treated steel sheet having excellent corrosion resistance and workability to automotive fuel and an external corrosion environment as its peripheral parts. .

[0002]

2. Description of the Related Art Conventionally, a steel sheet used for a gasoline tank is Pb-S containing 3 to 20% of Sn in the steel sheet.
A turn-plated steel sheet plated with an n alloy is generally used.
Such a turn-plated steel sheet has good corrosion resistance to gasoline fuel, and is hardly corroded by inevitably contained moisture and sulfur. On the other hand, as in the case where a steel plate is formed into a shape of a fuel tank, it can withstand severe press work and has good weldability.

[0003] However, turn-plated steel sheets are extremely corrosive fuels such as alcohol fuels and mixed fuels of alcohol and gasoline, or fuels containing organic acids such as formic acid and acetic acid generated by fuel deterioration. Therefore, the corrosion resistance is not always sufficient. Further, in recent years, with the regulation of the environment, particularly the regulation of the amount of Pb elution from end-of-life vehicles, a steel sheet containing no Pb has been required.

On the other hand, Japanese Patent Application Laid-Open No. 58-45396 discloses a steel sheet having excellent corrosion resistance to fuels having extremely severe corrosivity, such as alcohol fuel and a fuel mixture of alcohol and gasoline. 0 thickness on the surface.
It is disclosed that Ni alloy plating containing 5 to 50% of Zn of 5 to 20 μm is applied. Also, Japanese Unexamined Patent Publication No.
Japanese Patent No. 21295 discloses a steel plate for a fuel container, which is obtained by subjecting a steel plate surface to Zn-Ni alloy electroplating containing 5 to 30% of Ni and further applying a Sn plating layer thereon.

[0005] However, these techniques have the disadvantage that when pinholes are present in the plating layer, the corrosion resistance is reduced, and that film defects such as pinholes become cracks during forming and processing, thereby lowering the corrosion resistance of the plating layer. doing. It is technically and economically difficult to eliminate such film defects.

[0006] Japanese Patent Application Laid-Open No. 62-27587 discloses that the surface of a steel sheet is firstly plated with Zn or Zn-Ni alloy.
There has been proposed a steel sheet having a plating layer and a surface plating of Ni provided on the first plating layer. Although the steel sheet has excellent corrosion resistance to alcohol fuels and mixed fuels of alcohol and gasoline, since the surface plating metal is Ni alone, the sliding resistance during press forming is large, and when the press shape is severe, It has been found that press cracking occurs even when a steel sheet having high formability is used as the base steel sheet. Further, it was difficult to prevent press cracking even when Co was contained in the surface plating metal in an amount of 5% or less. In addition, Ni is a relatively expensive metal for industrial use.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, the present invention provides a steel sheet having excellent corrosion resistance to the corrosive environment on the inner and outer surfaces of a fuel tank and having excellent corrosion resistance and workability as a steel sheet capable of withstanding severe press formability. It is an object of the present invention to provide a surface-treated steel sheet for a fuel container.

[0008]

The present inventor has studied various means for imparting workability that is excellent in corrosion resistance to gasoline and alcohol, and a mixed fuel of alcohol and gasoline, and can withstand severe press molding. Finally, if the surface of the steel plate is plated with Zn or a Zn alloy, and a film made of metal Cr and Cr hydrated oxide is plated as a surface layer plating, the corrosion resistance is greatly improved, and the press formability is remarkably improved. I found that it could be improved. Such a superposition effect of plating of Zn or a Zn alloy and a film made of metal Cr and Cr hydrated oxide has not been known so far and is a new finding.

That is, the gist of the first invention of the present invention is that at least one surface of the steel sheet has a Zn plating layer having a basis weight of 5 to 80 g / m ² as a first plating layer.
Corrosion resistance and workability, characterized in that a second plating layer comprising 100 to 1000 mg / m ² of metallic Cr and ^{2 to} 30 mg / m ² of Cr hydrated oxide as a Cr content is further provided on the plating layer. Excellent surface treatment steel plate for fuel containers,
It is in.

The gist of the second invention of the present invention is that
In the first aspect, the Zn plating layer as the first plating layer is a Zn—Fe alloy plating layer having a basis weight of 5 to 80 g / m ² and containing 25% by weight or less of Fe, wherein corrosion resistance and workability are provided. Excellent surface treatment steel sheet for fuel containers.

The gist of the third invention of the present invention is that
In the first invention, the Zn plating layer as the first plating layer comprises a Zn—Ni alloy plating layer having a basis weight of 5 to 80 g / m ² and containing 25% by weight or less of Ni, wherein corrosion resistance and workability are provided. Excellent surface treatment steel sheet for fuel containers.

The gist of the fourth invention of the present invention is as follows.
In the first invention, the second invention or the third invention, there is provided a surface-treated steel sheet for a fuel container excellent in corrosion resistance and workability, characterized in that the steel sheet has a first plating layer and a second plating layer on both sides.

The gist of the fifth invention of the present invention is as follows.
In the first invention, the second invention or the third invention, there is provided a surface-treated steel sheet for a fuel container excellent in corrosion resistance and workability, characterized in that the steel sheet has the first plating layer and the second plating layer on only one side of the steel sheet. .

The gist of the sixth invention of the present invention is as follows.
In the fifth invention, the surface of the steel sheet having no first plating layer and the second plating layer has a basis weight of 5 to 80 g / m ² .
A surface-treated steel sheet for a fuel container having excellent corrosion resistance and workability, characterized by having an n-plated layer.

The gist of the present invention is as follows.
In the sixth invention, the Zn plating layer on the steel sheet surface on the side not having the first plating layer and the second plating layer has a basis weight of 5-8.
Zn-Fe that at 0 g / m ² containing Fe than 25 wt%
A surface-treated steel sheet for a fuel container having excellent corrosion resistance and workability, comprising an alloy plating layer.

The gist of the present invention is as follows.
In the sixth invention, the Zn plating layer on the steel sheet surface having no first plating layer and the second plating layer has a basis weight of 5-6.
Zn-Ni containing 0 g / m ² and 25% by weight or less of Ni
A surface-treated steel sheet for a fuel container having excellent corrosion resistance and workability, comprising an alloy plating layer.

The gist of the ninth invention of the present invention is as follows.
The first invention, the second invention, the third invention, the fourth invention, the fifth invention,
The surface-treated steel sheet for a fuel container according to the sixth, seventh or eighth invention, wherein the steel sheet contains 0.0003% to 0.0040% of B by weight. ,It is in.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
In the present invention,% means% by weight unless otherwise specified. For the Zn plating as the first plating layer,
Zn or Zn alloy having a basis weight of 5 to 80 g / m ² is plated. Even if it has the second plating layer of the present invention, if the basis weight of the first plating layer is less than 5 g / m ² , the anticorrosion effect is insufficient, and if it exceeds 80 g / m ² , the press formability decreases. More preferably, the basis weight is 10 to 60 g / m ² . In the present invention, Zn plating may be Zn alone or a Zn alloy containing 75% or more of Zn. If the Zn content is less than 75%, the rust preventive performance is reduced. In the case of Zn alloy plating, if a Zn—Fe alloy containing 25% or less of Fe or a Zn—Ni alloy containing 25% or less of Ni is used as the first plating layer, press formability is further improved. In addition, the corrosion resistance of the outer surface of the fuel tank is further improved.

In the case of Zn-Fe alloy plating, when the Fe concentration exceeds 25%, not only does the plating adhesion decrease, but also the workability tends to decrease. The Fe concentration is more preferably 5 to 14%.

In the case of Zn-Ni alloy plating, if the Ni concentration exceeds 25%, the anticorrosion effect and the workability tend to be rather lowered, so the upper limit is set to 25%. The Ni concentration is more preferably 7-14%.

In the Zn plating according to the present invention,
In order to improve corrosion resistance, plating adhesion, moldability, etc.,
Al, Pb, Sb, C, Si, P, Fe,
Sn, Mg, Mn, Ni, Cr, Co, Cu, Ca, L
One, two or more of i, Ti, B, and rare earth elements can be contained in a total amount of 25% or less. Needless to say, the Zn-Fe alloy plating contains Fe,
Zn-Ni alloy plating contains Ni. Alternatively, there is no problem even with Zn plating in which the above elements are mixed as impurities. Elements such as S and As;
Plating in which compounds such as oxides, carbides, and sulfides are dispersed can also be used.

On the first plating layer, 100 to 1000
mg / m ² of metallic Cr and ^{2 to 30} mg as Cr amount
/ M ² Cr hydrated oxide to form a second plating layer. If the amount of metallic Cr is less than 100 mg / m ² , the corrosion resistance after processing is insufficient. Further, as the amount of metallic Cr increases, the corrosion resistance improves, but is 1000 mg / m 2.
^If it exceeds ² , cracks occur in the metallic Cr during processing, and the corrosion resistance tends to be rather reduced. Therefore, the range of 100 to 1000 mg / m ² is suitable for the amount of metallic Cr. Metal Cr content is more preferably 200 to 500 mg
/ M ² . The amount of the hydrated Cr oxide is 2 as the amount of Cr.
A range of ３０30 mg / m ² is suitable. If the amount is less than 2 mg / m ^2, it is not preferable because the corrosion resistance is reduced and the adhesion of the paint applied to the outer surface of the fuel tank is reduced. On the other hand, if the amount exceeds 30 mg / m ² , metal Cr and Cr hydrated oxide are apt to peel off during processing, which is not preferable. The amount of the hydrated Cr oxide is more preferably 5 to 20 mg / m ² as the amount of Cr.

The first plating layer and the second plating layer need to be applied on at least one side of the steel sheet, but may be applied on both sides of the steel sheet surface, or may be applied only on one side. When both surfaces of a steel plate are in contact with fuel, such as a component mounted in a fuel tank, it is necessary to have a first plating layer and a second plating layer on both surfaces of the steel plate. On the other hand, when only one side of the steel plate comes into contact with the fuel as in the case of the fuel tank body, at least one side of the steel plate has the first
It is only necessary to have the plating layer and the second plating layer, and the other surface corresponding to the outer surface of the fuel tank does not necessarily need to have the first plating layer and the second plating layer. Of course, the first plating layer and the second plating layer may be provided on the other surface side, and it is easier to make the same plating on both surfaces in manufacturing. In this case, the plating type, the plating composition and the coating amount on both sides may be the same, and even if the plating type, the plating composition and the coating amount on both sides are different in consideration of the difference in characteristics required for each surface and the cost. It does not depart from the invention at all.

When the first plating layer and the second plating layer are provided only on one side for the purpose of cost reduction or the like, a Zn plating layer is provided on the other side to ensure corrosion resistance on the other side. Is preferred. In this case, the basis weight is 5 to 8
0 g / m ² is suitable. If the basis weight is less than 5 g / m ² , the anticorrosion effect is insufficient, and if it exceeds 80 g / m ² , the effect is saturated, so the upper limit is 80 g / m ² from the viewpoint of economy.
And More preferably, the basis weight is 20 to 60 g / m ^2.
It is. In the present invention, the Zn plating on the other side is Zn
It may be a single substance or a Zn alloy containing 75% or more of Zn. If the Zn content is less than 75%, the rust preventive performance is reduced. Among Zn alloy plating, Fe
Zn-Fe alloy containing 5% or less, or 25% Ni
%, The Zn-Ni alloy containing not more than 1.0% further improves the press formability, and further improves the coating corrosion resistance on the outer surface of the fuel tank.

In the case of Zn-Fe alloy plating, when the Fe concentration exceeds 25%, not only the plating adhesion is reduced but also the workability tends to be lowered. The Fe concentration is more preferably 5 to 14%.

In the case of Zn-Ni alloy plating, if the Ni concentration exceeds 25%, the anticorrosion effect and the workability tend to be rather lowered, so the upper limit is set to 25%. The Ni concentration is more preferably 7-14%.

In the Zn plating on the other side, corrosion resistance,
Al, Pb, Sb, C, Si, P, Fe, Sn, M
g, Mn, Ni, Cr, Co, Cu, Ca, Li, T
One, two or more of i, B and rare earth elements can be contained. Needless to say, the Zn-Fe alloy plating contains Fe, and the Zn-Ni alloy plating contains Ni. Alternatively, there is no problem even with Zn plating in which the above elements are mixed as impurities. Further, plating may be performed in which elements such as S and As, and compounds such as oxides, carbides, and sulfides are dispersed.

When the first plating layer and the second plating layer are provided only on one side, the plating on the other side may have the same plating composition and basis weight as the first plating layer, and are required for each side. Considering the differences in characteristics and costs,
The plating composition and the basis weight may be different from those of the plating layer.

In the present invention, the plating method is not particularly limited, and a conventional plating method can be applied. For example, for the first plating layer, an electroplating method, a hot-dip plating method, an alloyed hot-dip galvanizing method, a vapor deposition plating method, or the like can be used. For the second plating layer, an electroplating method or the like can be used. For example, using a chromic acid bath of 100 g / l or less containing an appropriate amount of sulfuric acid or fluorine compound, a one-step electrolytic chromic acid treatment for simultaneously forming a film composed of a metal Cr layer and a Cr hydrated oxide layer, or a high concentration And a two-step electrolytic chromic acid treatment in which a Cr hydrated oxide layer is formed using a low-concentration chromic acid bath. When the first plating layer and the second plating layer are provided only on one side, the plating on the other side can be performed by an electroplating method, a hot-dip plating method, a galvannealing method, an evaporation plating method, or the like. In this case, if the first plating layer is applied to both sides of the steel sheet and then the second plating layer is applied only to one side, the steel plate can be manufactured more easily and at lower cost.

In the present invention, B can be contained in the steel sheet in an amount of 0.0003 to 0.0040% as an alloying element, which is intended to prevent liquid metal embrittlement during welding. When the content of B is less than 0.0003%, the effect of addition is not sufficient. When the content of B exceeds 0.0040%, the effect is no longer saturated and the workability is reduced. When B is added, the range is 0.0003 to 0.0040%. More preferably, the addition amount of B is 0.0005 to 0.0025%. The components of the steel sheet of the present invention are not particularly limited, and an appropriate component can be selected according to the required strength, workability, formability, and the like.

In the Zn plating, Zn-Fe alloy plating or Zn-Ni alloy plating of the steel sheet of the present invention, Al, Pb, Sb, C, Si, P, Fe, S
n, Mg, Mn, Ni, Cr, Co, Cu, Ca, L
Even plating containing or mixing one or more of i, Ti, and rare earth elements does not cause any trouble. Further, the metal Cr as the second plating layer: 100 to 50
0 mg / m ² and Cr hydrated oxide: ^{2 to 30} mg / m
² , S, F, Cl, Al, Pb,
Sb, C, Si, P, Fe, Sn, Mg, Mn, Cr,
Even plating containing or mixing one or more of Co, Cu, Ca, Li, Ti and rare earth elements does not cause any trouble.

Further, the effect of the steel sheet applied to the present invention is sufficiently exhibited regardless of whether it is a cold-rolled steel sheet or a hot-rolled steel sheet manufactured by an ordinary process. Does not change significantly.

It goes without saying that various treatments can be added to the steel sheet of the present invention.
Chromate treatment, phosphate treatment, treatment for improving phosphate treatment, lubricity improvement treatment, weldability improvement treatment,
Even if a resin coating process or the like is performed, the process does not depart from the scope of the present invention, and various processes can be performed according to additionally required characteristics.

The steel sheet of the present invention has a tensile strength of 3
From ordinary steel of less than 00 N / mm ² or steel sheet for ultra deep drawing, high strength steel of 300 N / mm ² or more (300, 34
0, 400, 440 N / mm ² class).

[0035]

EXAMPLES The plating shown in Table 1 was applied to a cold rolled steel sheet of JIS G3141 SPCE. In Table 1, No.
In each of the steel sheets 3, 7, and 10, a steel sheet containing B at the content shown in Table 1 was used as a cold-rolled steel sheet. After each steel sheet was degreased, it was first plated with Zn or a Zn alloy by the method shown in Table 1, and then 100 to 10
200 mg / m ² of 2 to 30 as a metallic Cr and Cr content
A coating layer composed of mg / m ² of Cr hydrated oxide was formed. Here, the plate thickness was 0.8 mm. In Table 1, No.
Nos. 1 to 12 are examples of the present invention. 13 to 17 are comparative examples.

The plating bath composition and plating conditions for forming the second plating layer were as follows. Metal Cr content and Cr
The amount of hydrated oxide was controlled by changing the electrolysis time. CrO ₃ : 75 g / l NaF: 4 g / l H ₂ SO ₄ : 0.4 g / l Bath temperature: 50 ° C Cathode current density: 40 A / dm ² Cr hydrated oxidation on Zn plating or Zn alloy plating Since it is difficult to measure the physical quantity, the following method was used instead. That is, after subjecting a cold-rolled steel sheet to electrolytic chromic acid treatment under the same conditions, the total amount of Cr is measured by a fluorescent X-ray method, and the test piece is immersed in a strong alkaline aqueous solution at a temperature of 95 ° C. to dissolve the Cr hydrated oxide. After that, the test piece was taken out and washed with water, the Cr content was measured again by the X-ray fluorescence method, and the difference from the initial total Cr content was defined as the Cr content in the Cr hydrated oxide. The amount of metallic Cr was the remaining amount of Cr. However, the Cr content in the steel sheet was corrected as a background.

Test pieces were taken from each steel sheet and evaluated for workability and corrosion resistance after working. Workability is determined by the critical drawing ratio in the cylindrical deep drawing test (= maximum blank diameter drawn without cracking ず
(Punch diameter). The larger the value of the limit aperture ratio, the more
It shows that workability is good.

The corrosion resistance after processing was tested in the following manner. First, a circular test piece was prepared by setting the top surface in Table 1 to the inner surface, with a draw ratio of 2.0, an inner diameter of 50 mm, and a depth of 35 mm.
After being molded into a cylindrical shape having a diameter of 1 mm, the concave portion was filled with a corrosion test solution, the container was sealed, and kept at 30 ° C. for 2 months. The following two kinds of corrosion test solutions were used. In addition, the comparative example No. 13-15
Was poor in formability and could not be formed at a draw ratio of 2.0, so the draw ratio was 1.8. Corrosion test solution 1 Gasoline: balance Water: 1.0% by volume Formic acid: 0.1 g / l Corrosion test solution 2 Gasoline: Balance ethanol: 30% by volume Formic acid: 0.1 g / l Water: 1.0% by volume NaCl : 0.05 g / l The corrosion resistance after processing was evaluated by visually observing the corrosion test solution and the state of corrosion of the bottom and wall of the inner surface of the recess after the corrosion test was completed, and evaluated by the following five-step evaluation. . ◎: No abnormality at all, or extremely slight corrosion ○: Slight corrosion △: Partial corrosion ×: Corrosion over the entire surface or local corrosion ××: Significant overall corrosion or significant local corrosion

The results of each evaluation are shown in Table 1. First
As is clear from the table, No. 1 of the present invention example. 1-12
Has excellent workability and corrosion resistance, and the corrosion resistance is comparative example No. It is much better than the Pb-11% Sn alloy plated steel sheet shown in FIG. On the other hand, Comparative Example N
o. In the case of 13 to 16, the corrosion resistance was poor or the workability of the steel sheet was insufficient.

[0040]

[Table 1]

[0041]

As described above, the present invention makes it possible to provide a surface-treated steel sheet for a fuel container having excellent workability, formability and corrosion resistance, and contributes to industrial development. However, it is extremely large.

Claims (9)

[Claims] 1. A steel sheet having a Zn plating layer having a basis weight of 5 to 80 g / m ² as a first plating layer on at least one side of the surface of a steel sheet, and further having a Zn plating layer of 100 to 1000 mg / m ² on the first plating layer.
2~30mg as metallic Cr and Cr of m ² / m ²
A surface treated steel sheet for a fuel container having excellent corrosion resistance and workability, characterized by having a second plating layer composed of Cr hydrated oxide. 2. A Zn plating layer as a first plating layer,
Basis weight 5 to 80 g / m corrosion resistance according to claim ^{1, 2} in the Fe, characterized in that it consists of Zn-Fe alloy plating layer containing 25% by weight or less, excellent formability fuel container for surface treated steel sheet. 3. A Zn plating layer as a first plating layer,
Basis weight 5 to 80 g / m corrosion resistance according to claim ^{1, 2} in the Ni, characterized in that it consists of Zn-Ni alloy plating layer containing 25% by weight or less, excellent formability fuel container for surface treated steel sheet. 4. The surface-treated steel sheet for a fuel container according to claim 1, which has a first plating layer and a second plating layer on both sides of the steel sheet, and has excellent corrosion resistance and workability. 5. The surface-treated steel sheet for a fuel container having excellent corrosion resistance and workability according to claim 1, wherein the first and second plating layers are provided only on one side of the steel sheet. 6. The corrosion resistance according to claim 5, wherein a Zn plating layer having a basis weight of 5 to 80 g / m ² is provided on the surface of the steel sheet on a side not having the first plating layer and the second plating layer. Surface-treated steel sheet for fuel containers with excellent workability. 7. The Zn plating layer on the surface of the steel sheet having no first plating layer and the second plating layer has a basis weight of 5 to 80 g.
/ M corrosion resistance according ^to claim ^{6, 2} at the Fe, characterized in that it consists of Zn-Fe alloy plating layer containing 25% by weight or less, excellent formability fuel container for surface treated steel sheet. 8. The Zn plating layer on the surface of the steel sheet having no first plating layer and the second plating layer has a basis weight of 5 to 80 g.
/ M corrosion resistance according ^to claim ^{6, 2} in the Ni, characterized in that it consists of Zn-Ni alloy plating layer containing 25% by weight or less, excellent formability fuel container for surface treated steel sheet. 9. The steel sheet according to claim 1, wherein B is 0.0003% by weight.
Claims 1, 2, 3, 4, 5, containing 0.0040%.
The surface-treated steel sheet for a fuel container according to 6, 7, or 8, which is excellent in corrosion resistance and workability.