WO2011033775A1 - Surface-treated steel sheet used to manufacture pipe and having corrosion-resistant properties against fuel vapors, and pipe and fuel supply pipe that use same - Google Patents

Abstract

Provided are: a surface-treated steel sheet used to manufacture a pipe; a pipe; and a fuel supply pipe. The surface-treated steel sheet, the pipe, and the fuel supply pipe have corrosion-resistant properties against fuel vapors, such as those of gasoline, light oil, bioethanol, and biodiesel fuel. A surface-treated steel sheet used to manufacture a pipe, the surface-treated steel sheet being provided on the surface thereof with a layer which contains Zn, Co, and Mo and having corrosion-resistant properties against fuel vapors. A pipe constructed from a steel sheet, provided on the inner surface thereof with a layer which contains Zn, Co, and Mo, and having corrosion-resistant properties against fuel vapors. A fuel supply pipe (20) constructed from a steel sheet and adapted to supply fuel to a fuel tank (23), the fuel supply pipe (20) being provided with a large-diameter pipe section (21) through which the fuel passes and also with a small-diameter pipe section (22) which allows ventilation between the upper portion and the lower portion of the large-diameter pipe section. The inner surface of the small-diameter pipe section is provided with a layer having a plating thickness in the range of 1.0 - 8.0 µm and containing Zn, Co, and Mo.

Description

Surface-treated steel sheet for pipe production having corrosion resistance against fuel vapor, pipe using the steel sheet, and oil supply pipe

The present invention relates to a surface-treated steel sheet having corrosion resistance against fuel vapor, a pipe using the steel sheet, and a fuel supply pipe.

In recent years, in order to reduce greenhouse gases, there has been an active movement to use so-called bioethanol-mixed gasoline in which bioethanol, which is carbon neutral, is mixed with gasoline. However, when ethanol is added to gasoline, it becomes easier for the gasoline to absorb moisture, and water may be mixed into the fuel tank.
Furthermore, if the ethanol mixed gasoline is left standing for a long time, the gasoline deteriorates and an organic acid is formed in the gasoline.
In this way, when moisture absorption and gasoline deterioration occur, ethanol can be mixed into both water and gasoline, so water and organic acids are contained inside the gasoline. The mixture may evaporate.
In that case, the inner surface of the pipe, which normally contacts only non-corrosive gasoline vapor, is exposed to a strong corrosive environment.
Therefore, pipes placed under an atmosphere of bioethanol mixed gasoline are also required to have corrosion resistance assuming a corrosive environment.
As a countermeasure to these corrosive environments, for example, Patent Document 1 discloses that the deposition amount is Cr on a Sn—Zn alloy plated surface having a plating deposition amount of 10 to 70 g / m ² and Sn-1 to 50% Zn. A steel plate treated with a chromate film made of chromic acid, silica, inorganic phosphoric acid or organic phosphoric acid of 100 mg / m ² or less in terms of conversion, or further treated with a resin chromate film containing an organic resin, and a pair of flanges A fuel container for automobiles having excellent corrosion resistance is described in which the flange portion of the vertical molded body is continuously seam welded.

JP 2000-17450 A

However, the material used for the automobile fuel container described in Patent Document 1 is a corrosion resistance of a portion such as a fuel tank that is immersed in an automobile fuel such as gasoline and directly contacts the automobile fuel, and is not corrosion resistant to steam. .
For example, pipes connected to fuel tanks, such as fuel pipes, are overwhelming in the case of being exposed to highly volatile automotive fuel vapors rather than being directly exposed to automotive fuel. Too many.
In addition, the depletion of fossil fuels has become serious internationally, and the spread of bioethanol and biodiesel fuels has become widespread.
Thus, in addition to gasoline, which is a conventional automobile fuel, a material having sufficient characteristics for both bioethanol and biodiesel fuel and its vapor has been demanded.
Accordingly, an object of the present invention is to solve the above-described conventional problems, and is a surface treatment for producing pipes having sufficient corrosion resistance against fuel vapor such as fuel, particularly gasoline, light oil, bioethanol, or biodiesel fuel. It is to provide a steel plate.
Another object of the present invention is to provide a pipe and an oil supply pipe using the surface-treated steel sheet.

(1) The surface-treated steel sheet for pipe production according to the present invention is characterized in that a layer containing Zn, Co, and Mo is provided on at least one surface of the steel sheet and has corrosion resistance against fuel vapor.
(2) The surface-treated steel sheet for pipe production according to the present invention is characterized in that, in (1), a Ni layer is formed between the steel sheet and the layer containing Zn, Co, and Mo. .
(3) The surface-treated steel sheet for pipe production according to the present invention is characterized in that, in the above (1), an Fe—Ni diffusion layer is provided under a layer containing Zn, Co, and Mo.
(4) The surface-treated steel sheet for manufacturing a pipe of the present invention is the above-described (1), wherein an Fe—Ni diffusion layer and a softened Ni layer are sequentially provided below the layer containing Zn, Co, and Mo. It is characterized by being.
(5) In the surface-treated steel sheet for producing a pipe of the present invention, in any of the above (1) to (4), the thickness of the layer containing Zn, Co, and Mo is 1.0 to 8.0 μm. It is characterized by being.
(6) The surface-treated steel sheet for producing pipes of the present invention is characterized in that, in any one of (1) to (5), the fuel contains gasoline, light oil, bioethanol, or biodiesel fuel.
(7) The pipe of the present invention is characterized in that a layer containing Zn, Co, and Mo is provided on the inner surface of a pipe made of a steel plate and has corrosion resistance against fuel vapor.
(8) The pipe of the present invention is characterized in that, in the above (7), a Ni layer is formed between the layer containing Zn, Co, and Mo and the steel sheet.
(9) The pipe of the present invention is characterized in that, in the above (7), an Fe—Ni diffusion layer is provided under a layer containing Zn, Co, and Mo.
(10) In the pipe of the present invention, in the above (7), an Fe—Ni diffusion layer and a softened Ni layer are sequentially provided below the layer containing Zn, Co, and Mo. Features.
(11) The pipe of the present invention is characterized in that in any one of the above (7) to (10), the thickness of the layer containing Zn, Co, and Mo is 1.0 to 8.0 μm. To do.
(12) The pipe of the present invention is characterized in that, in any one of the above (7) to (11), the fuel contains gasoline, light oil, bioethanol, or biodiesel fuel.
(13) The oil supply pipe of the present invention is an oil supply pipe made of a steel plate for supplying fuel to a fuel tank,
A large-diameter pipe section through which fuel passes;
A small-diameter pipe portion that ventilates the upper and lower portions of the large-diameter pipe portion,
A layer containing 1.0 to 8.0 μm of Zn, Co, and Mo is formed at least on the inner surface of the large-diameter pipe portion, and has corrosion resistance against fuel vapor.
(14) The oil supply pipe of the present invention is characterized in that, in (13), a Ni layer is formed between the steel sheet and the layer containing Zn, Co, and Mo.
(15) In the oil supply pipe of the present invention, the Fe—Ni diffusion layer and the softened Ni layer are sequentially provided below the layer containing Zn, Co, and Mo in (13). It is characterized by.
(16) The oil supply pipe of the present invention is characterized in that, in any one of the above (13) to (15), the thickness of the layer containing Zn, Co, and Mo is 1.0 to 8.0 μm. And
(17) The oil supply pipe of the present invention is characterized in that, in any of the above (13) to (16), the fuel includes gasoline, light oil, bioethanol, or biodiesel fuel.

The surface-treated steel sheet for pipe production according to the present invention, the pipe using the surface-treated steel sheet, and the oil supply pipe, even when exposed to fuel vapor such as gasoline, light oil, bioethanol, or biodiesel fuel, which are automobile fuels, are generated. Rust can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing which shows the structure of the surface treatment steel plate of Embodiment 1 of this invention, (a) forms the layer containing Zn, Co, and Mo on both surfaces of the steel plate used as a board | substrate, (b ) Is a method in which a Ni layer is first formed on both surfaces of a steel plate to be a substrate, and a layer containing Zn, Co, and Mo is formed thereon. It is a schematic explanatory drawing which shows the structure of the surface treatment steel plate of Embodiment 2 of this invention, (a) is the layer which contains Zn, Co, and Mo on both surfaces of the steel plate used as a board | substrate, and Fe-Ni diffused layer under it (B) forms a layer containing Zn, Co, and Mo, a Fe—Ni diffusion layer, and a softened Ni layer between them on both surfaces of a steel plate to be a substrate. It is a thing. It is a schematic explanatory drawing which shows the method of the corrosion resistance test with respect to the bioethanol mixing gasoline of the surface treatment steel plate of this invention. It is a schematic explanatory drawing which shows the method of the corrosion resistance test with respect to the bioethanol mixing gasoline of the surface treatment steel plate of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing of the oil supply pipe using the surface treatment steel plate of this invention, (a) has the large diameter pipe part which a fuel passes, and the thin diameter pipe part which ventilates the upper part and lower part of a large diameter pipe part An oil supply pipe is shown, (b) shows the oil supply pipe in which the large diameter pipe part and thin diameter pipe part which a fuel passes are formed independently.

Hereinafter, embodiments of the present invention will be described in detail.
<Steel plate>
A low carbon aluminum killed hot-rolled coil is usually used as an original plate of a surface-treated steel sheet for pipe production.
In addition, a coil produced from non-aged continuous cast steel by adding niobium or titanium to the ultra low carbon steel having a carbon content of 0.003% by weight or less, and further adding niobium or titanium thereto is also used.

<Pretreatment for surface treatment>
As a pretreatment for the surface treatment, the scale (oxide film) on the surface of the cold-rolled steel sheet is removed by electrolysis or degreasing in an alkaline solution usually containing caustic soda as a main ingredient. After removal, the product is rolled to the product thickness in a cold rolling process.

<Annealing>
The rolling oil adhered by rolling is electrolytically cleaned and then annealed. The annealing may be either continuous annealing or box annealing and is not particularly particular. After annealing, the shape is corrected.

<Ni plating>
Although it is preferable to first apply Ni plating on the steel plate after annealing, it is not essential.
In general, a nickel sulfate bath called a watt bath is mainly used as the Ni plating bath, but a sulfamic acid bath, a borofluoride bath, a chloride bath, and the like can also be used. When plating using these baths, the thickness of the Ni plating is in the range of 3.0 μm or less. The reason will be described in the column of the evaluation method below.
In order to obtain the plating thickness, when a typical Watt bath is used, the bath composition is nickel sulfate 200 to 350 g / L, nickel chloride 20 to 50 g / L, boric acid 20 to 50 g / L, pH 3.6 to It is obtained under electrolytic conditions of 4.6, bath temperature of 50 to 65 ° C., current density of 5 to 50 A / dm ² and Coulomb number of about 900 c / dm ² or less. The boric acid added as a stabilizer may be citric acid.
Here, as the Ni plating formed in the Watt bath, a matte Ni plating in which no organic compound is added other than the pit inhibitor, and an organic compound called a leveling agent that smoothes the crystallized crystal plane of the plating layer is added. In addition to bright Ni plating, there is also bright Ni plating to which an organic compound containing a sulfur component is added in order to produce a gloss by refining the Ni plating crystal structure in addition to the leveling agent, but all can be used in the present invention. .

<Formation of Fe-Ni diffusion layer>
Next, when forming a diffusion layer, a heat treatment for forming an Fe—Ni diffusion layer is performed after Ni plating.
The purpose of this heat treatment is to soften and recrystallize the fine crystal state of the Ni plating as it is, to improve the adhesion between the steel substrate and the plating layer, and to form pipes on the pipe by the Fe-Ni diffusion layer formed by the heat treatment. It is to improve the film workability (followability) with respect to bending and spooling.
As a method for forming the Fe—Ni diffusion layer, there are a method of using a continuous annealing furnace and a method of thermal diffusion using a box-type annealing furnace. The heat diffusion temperature is in the range of 400 to 800 ° C. and the diffusion time is in the range of 60 seconds to 12 hours. Usually, the heat diffusion is performed for 12 hours or more.
The gas atmosphere at the time of diffusion is a non-oxidizing or reducing protective gas atmosphere.
Furthermore, in the present invention, as a heat treatment method by box-type annealing, heat treatment by a protective gas composed of 75% hydrogen-25% nitrogen generated by an ammonia crack method called hydrogen-enriched annealing with good heat transfer is suitably applied. The This method is advantageous in that the uniformity of the temperature distribution in the steel strip in the longitudinal direction and the width direction of the steel strip is good, so that the variation in the steel strip of the Fe—Ni diffusion layer and between the steel strips is small.
In the diffusion treatment, if the heat treatment is continued even after the iron reaches the outermost surface, the ratio of the iron exposed to the outermost layer increases.
The heat treatment conditions were variously changed for each plating thickness, and the thicknesses of the softened Ni layer and Fe—Ni diffusion layer were calculated from the results obtained by the glow discharge emission analysis, that is, GDS analysis (GDLS-5017 manufactured by Shimadzu). A number of experiments were performed to create a number of samples with varying thicknesses of the softened Ni layer and Fe—Ni diffusion layer.
GDS analysis is a measurement method for obtaining an analysis chart in the depth direction. In the present invention, Ni and Fe are considered to exist until their respective strengths become 1/10 of the respective maximum strength values.
The thickness of the softened Ni layer can be expressed by the GDS measurement time from the surface layer, that is, the GDS measurement time 0 to the Fe strength becoming 1/10 of the maximum strength value.
The thickness of the Fe—Ni diffusion layer can be expressed by the GDS measurement time from when the strength of Fe becomes 1/10 of the maximum strength value to when the strength of Ni becomes 1/10 of the maximum strength value.
For the Ni plating layer before the heat treatment, the thickness of the Ni plating layer is expressed by the GDS measurement time from the surface layer, that is, the measurement time 0 to the Ni intensity becomes 1/10 of the maximum strength value. The thickness of the plating layer is actually measured with fluorescent X-rays.
The ratio between the GDS measurement time of the Ni plating layer, the GDS measurement time of the softened Ni layer, and the GDS measurement time of the Fe—Ni diffusion layer was calculated. From the thickness, the thickness of the softened Ni layer and the thickness of the Fe—Ni diffusion layer are calculated.

<Formation of a layer containing Zn, Co, and Mo>
Next, a layer containing Zn, Co, and Mo is formed on the Ni plating, Fe—Ni diffusion layer, or softened Ni layer by plating. When Ni plating is not performed in the previous step, a layer containing Zn, Co, and Mo is directly formed on the steel plate after annealing by plating.
The plating thickness of the layer containing Zn, Co, and Mo is preferably in the range of 1.0 to 8.0 μm.
In order to obtain the plating thickness of the layer containing Zn, Co, and Mo, zinc sulfate 180 to 280 g / L, cobalt sulfate 10 to 70 g / L, ammonium molybdate 0.01 to 0.4 g / L, ammonium sulfate 10 It is obtained in a bath composition of ˜40 g / L, sodium sulfate 20˜50 g / L, pH 2.7˜3.7, bath temperature 30˜50 ° C., under electrolysis conditions of current density 5˜50 A / dm 2.
The component ratio of the plated Zn, Co, and Mo-containing layer is preferably Co: 0.1 to 5%, Mo: 0.001 to 1%, and the balance: Zn. Such a component ratio of the alloy plating can be realized by adjusting the bath composition, pH, bath temperature, current density, and the like within a suitable range.
FIG. 1 shows a schematic configuration of a steel plate provided with a layer containing Zn, Co, and Mo thus formed.
FIG. 1 (a) shows a case where layers containing Zn, Co, and Mo are formed on both surfaces of a steel plate to be a substrate, and FIG. 1 (b) shows that Ni plating is first applied to both surfaces of a steel plate to be a substrate. And a layer containing Zn, Co, and Mo is formed thereon.
FIG. 2 (a) shows a structure in which a layer containing Zn, Co, and Mo is formed on both surfaces of a steel plate to be a substrate and an Fe—Ni diffusion layer is formed thereunder, and FIG. 2 (b) is a substrate. A layer containing Zn, Co, and Mo, a Fe—Ni diffusion layer, and a softened Ni layer are formed between both surfaces of the steel plate.

<Evaluation method>
An evaluation test piece was produced from a steel sheet provided with a layer containing Zn, Co, and Mo of each plating thickness, and the corrosion resistance was investigated by immersing the specimen in bioethanol mixed gasoline. Corrosion resistance was confirmed by the presence or absence of rusting.
A corrosive solution simulating bioethanol-mixed gasoline was used as a test.
As the corrosive liquid, 100 ppm formic acid and 200 ppm acetic acid were added to regular gasoline specified in JIS K2202, and 10% bioethanol specified in JASO M361 was added to purify a simulated deteriorated gasoline.
For the purpose of further enhancing the corrosiveness, corrosive water was prepared by adding 1000 ppm formic acid, 2000 ppm acetic acid, and 1000 ppm chlorine to pure water, and 10 wt% was added to the above deteriorated gasoline to obtain a corrosive liquid.
The corrosive liquid is in a state where the upper layer is divided into degraded gasoline and the lower layer is divided into two layers of corrosive water.
It arrange | positioned in an airtight container so that an evaluation test piece may be immersed in this corrosive solution half, and time-lapsed in a 45 degreeC thermostat.
As a result, as shown in FIGS.
From the top, the evaluation test piece is a gas phase part 11 in contact with fuel vapor (gas phase) of deteriorated gasoline, a liquid phase part 12 in contact with deteriorated gasoline (liquid phase), and an aqueous phase in contact with corrosive water (water phase). It will be separated into part 13.
And the corrosion resistance with respect to the fuel vapor | steam of an evaluation test piece was evaluated by investigating the corrosion of the gaseous-phase part 11 of an evaluation test piece.
Moreover, the evaluation method shown in FIG. 4 used what bent 90 degree | times by making a plating surface into an inner surface (recessed part). The radius of the trough was 1.0 mm. The rusting of the processed valley was evaluated.
From many experimental results, it was found that rusting in the gas phase portion is suppressed by setting the plating thickness of the layer containing Zn, Co, and Mo to be in the range of 1.0 to 8.0 μm.
Further, by forming a Ni layer, a Fe—Ni diffusion layer, or a softened Ni layer under the layer containing Zn, Co, and Mo, rusting in the gas phase portion may be further suppressed. I understood.
That is, from the experimental results, when the plating thickness of the layer containing Zn, Co, and Mo was less than 1.0 μm, sufficient corrosion resistance in the gas phase portion could not be obtained.
Moreover, when the plating thickness of the layer containing Zn, Co, and Mo exceeds 8.0 μm, the surface may be scraped during processing of a pipe tube or the like and wear powder may be generated, which is not preferable.
Furthermore, by forming a Ni layer, Fe—Ni diffusion layer or softened Ni layer below the layer containing Zn, Co, and Mo, rusting in the gas phase is further suppressed. When the thickness of the layer or the softened Ni layer exceeds 3.0 μm, the total thickness of the layer containing Zn, Co and Mo and the Ni layer or the softened Ni layer increases, The surface may be scraped during processing, and wear powder may be generated, which is not preferable.

<Pipe processing>
Using a steel plate provided with a layer containing Zn, Co, and Mo (and Ni layer, Fe-Ni diffusion layer or softened Ni layer), the shape is corrected by a leveler, and a slitter is used to obtain a predetermined outer diameter. After slitting, the pipe is manufactured into a pipe shape by a molding machine, and pipes are manufactured by seam welding the end faces in the longitudinal direction by high frequency induction welding.
As the pipe, there are an oil supply pipe for introducing fuel into the tank, a pipe for introducing fuel from the tank to the engine, and a pipe for venting.
As shown in FIG. 5A, the fuel supply pipe 20 is attached to the fuel tank 23 so as to extend obliquely upward from the upper part of the fuel tank 23.
Further, a small-diameter pipe portion 22 that branches from the middle of the large-diameter pipe portion 21 through which the fuel passes and is connected to the upper and lower portions of the large-diameter pipe portion 21 is connected to the fuel supply pipe 20.
The large diameter pipe part 21 is manufactured using the steel plate of the present invention. In addition, you may manufacture a thin diameter pipe part using the steel plate of this invention.
In addition, the oil supply pipe 20 prescribed | regulated by this invention is not restricted to a shape as shown to Fig.5 (a), For example, as shown in FIG.5 (b), with the large diameter pipe part 21 which a fuel passes, Even if the small-diameter pipe portion 22 is attached to the fuel tank 23 in an independent shape, the corrosion resistance against the fuel vapor is still particularly required, and thus those of these forms are also included.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Example 1>
A cold-rolled and annealed low carbon aluminum killed steel plate having a thickness of 0.70 mm was used as a plating base plate.
The components of the steel plate that is the plating original plate are as follows.
C: 0.045%, Mn: 0.23%, Si: 0.02%, P: 0.012%, S: 0.009%, Al: 0.063%, N: 0.0036%, balance : Fe and inevitable impurities. The steel sheet was subjected to alkaline electrolytic degreasing and pickling with sulfuric acid soaking, to obtain a surface-treated steel sheet provided with a layer containing Zn, Co, and Mo having a thickness of 1 μm.
The composition ratio of the formed layer containing Zn, Co, and Mo was Co: 0.3%, Mo: 0.01%, and the balance: Zn (% is mass). The thickness and composition ratio of the layer containing Zn, Co, and Mo were measured by fluorescent X-ray analysis (ZSX 100e, manufactured by Rigaku).

<Examples 2 to 18>
After the steel plate of Example 1 was subjected to alkaline electrolytic degreasing and sulfuric acid immersion pickling,
The surface-treated steel sheets of Examples 2 to 18 in Table 1 were obtained by changing the thicknesses of the layers containing Zn, Co, and Mo.
In Examples 2 to 18, the values of the thickness of the steel plates plated with Ni were listed. Those not plated with Ni were described as having a thickness of zero.
For Ni plating, the plating thickness was changed under the conditions of Watt bath matte plating.
Other conditions were the same as in Example 1. The Ni plating thickness was measured by fluorescent X-ray analysis (ZSX 100e, manufactured by Rigaku).

<Example 19>
After the steel plate of Example 1 was subjected to alkaline electrolytic degreasing and pickling with sulfuric acid immersion, nickel plating with a plating thickness of 2 μm was obtained under the condition of Watt bath matte plating, to obtain a nickel plated steel plate, Thermal diffusion treatment was performed under conditions of 1 min to form a 1.23 μm thick Fe—Ni diffusion layer on the surface of the steel plate.
Thereafter, a layer containing Zn, Co, and Mo having a thickness of 1 μm was provided thereon by plating to obtain a surface-treated steel sheet of Example 19 in Table 2.
The composition ratio of the formed plating layer containing Zn, Co, and Mo was the same as that in Example 1.

<Examples 20 to 32>
Steel sheets of Examples 20 to 32 in Table 2 were obtained by changing the thickness of the layer containing Zn, Co, and Mo.
In Examples 20 to 32, the value of the thickness of a softened Ni layer formed between the layer containing Zn, Co, and Mo and the Fe—Ni diffusion layer is described. Those that did not form the softened Ni layer were described as having a thickness of zero.
For Ni plating, the plating thickness was changed under the conditions of Watt bath matte plating. The Ni plating thickness was measured by fluorescent X-ray analysis (ZSX 100e, manufactured by Rigaku).
Conditions other than the thickness of the layer containing Zn, Co, and Mo, the Ni plating thickness, and the thermal diffusion treatment described in Table 2 were the same as in Example 19.

<Comparative example>
The surface-treated steel sheets of Comparative Examples 1 to 5 in Table 1 were obtained by changing the thickness of the layer containing Zn, Co, and Mo and the thickness of the Ni layer.
(Insert 0018 of C036)
Further, the thickness of the layer containing Zn, Co, and Mo, the thickness of the Ni layer, and the thermal diffusion treatment were changed as shown in Table 2, and the other conditions were the same as in Example 19, and the comparative example in Table 2 was used. 6 to 11 surface-treated steel sheets were obtained.

<Evaluation>
Next, an evaluation test piece was prepared from each of the plated steel sheets of Examples and Comparative Examples, and after aging for 500 hours in a 45 ° C. constant temperature bath, the appearance of the gas phase portion of each evaluation test piece was observed, and rust was observed. The occurrence was investigated. The results are shown in “Results of occurrence of red rust in gas phase” in Tables 1 and 2.

As apparent from Tables 1 and 2, the surface-treated steel sheets of Examples 1 to 32 of the present invention were excellent as a pipe material having no rust and corrosion resistance against fuel vapor.
Since the above corrosive liquid generates steam that is more corrosive than gasoline, light oil, bioethanol, or biodiesel fuel, if there is no rust in this corrosive liquid test, gasoline, light oil, bioethanol, or biodiesel It is considered that there is no rust on the fuel.
On the other hand, the surface-treated steel sheets of Comparative Examples 1 to 11 have red rust and are not practical as a material for producing pipes having corrosion resistance against fuel vapor.

The surface-treated steel sheet for pipe production according to the present invention can suppress rusting upon exposure to fuel vapor such as gasoline, light oil, bioethanol, or biodiesel fuel.
Moreover, the pipe and the oil supply pipe using the surface-treated steel sheet for manufacturing the oil supply pipe of the present invention are excellent in corrosion resistance against fuel vapor, and are highly industrially applicable.

11: Gas phase part 12: Liquid phase part 13: Water phase part 20: Oil supply pipe 21: Large diameter pipe part 22: Small diameter pipe part 23: Fuel tank

Claims (17)

A surface-treated steel sheet for pipe production, characterized in that a layer containing Zn, Co, and Mo is provided on at least one surface of the steel sheet and has corrosion resistance against fuel vapor. The surface-treated steel sheet for pipe production according to claim 1, wherein a Ni layer is formed between the layer containing Zn, Co, and Mo and the steel sheet. 2. The surface-treated steel sheet for pipe production according to claim 1, wherein an Fe—Ni diffusion layer is provided under the layer containing Zn, Co, and Mo. The surface treatment for manufacturing a pipe according to claim 1, wherein an Fe-Ni diffusion layer and a softened Ni layer are sequentially provided under the Zn, Co, and Mo-containing layer. steel sheet. The surface-treated steel sheet for pipe production according to any one of claims 1 to 4, wherein the layer containing Zn, Co, and Mo has a thickness of 1.0 to 8.0 µm. The surface-treated steel sheet for pipe production according to any one of claims 1 to 5, wherein the fuel includes gasoline, light oil, bioethanol, or biodiesel fuel. A pipe characterized in that a layer containing Zn, Co, and Mo is provided on the inner surface of a pipe made of a steel plate and has corrosion resistance against fuel vapor. The pipe according to claim 7, wherein a Ni layer is formed between the layer containing Zn, Co, and Mo and the steel plate. The pipe according to claim 7, wherein a Fe-Ni diffusion layer is provided under the layer containing Zn, Co, and Mo. 8. The pipe according to claim 7, wherein an Fe—Ni diffusion layer and a softened Ni layer are sequentially provided below the layer containing Zn, Co, and Mo. 11. The pipe according to claim 7, wherein the thickness of the layer containing Zn, Co, and Mo is 1.0 to 8.0 μm. The pipe according to any one of claims 7 to 11, wherein the fuel includes gasoline, light oil, bioethanol, or biodiesel fuel. An oil supply pipe made of a steel plate for supplying fuel to a fuel tank,
A large-diameter pipe section through which fuel passes;
A small-diameter pipe portion that ventilates the upper and lower portions of the large-diameter pipe portion,
A fuel supply pipe characterized in that a layer containing 1.0 to 8.0 μm of Zn, Co, and Mo is formed on at least the inner surface of the large-diameter pipe portion, and has corrosion resistance against fuel vapor. The oil supply pipe according to claim 13, wherein a Ni layer is formed between the Zn, Co, and Mo-containing layer and the steel plate. The oil supply pipe according to claim 13, wherein an Fe-Ni diffusion layer and a softened Ni layer are sequentially provided under the Zn, Co, and Mo-containing layer. The oil supply pipe according to any one of claims 13 to 15, wherein a film thickness of the layer containing Zn, Co, and Mo is 1.0 to 8.0 µm. The oil supply pipe according to any one of claims 13 to 16, wherein the fuel includes gasoline, light oil, bioethanol, or biodiesel fuel.

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