JPH10291278A - Highly corrosion-resistant steel sheet for fuel container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raiser rapidly corrosion resistance to oxidation degradated gasoline or the like by a method wherein metal plating layer having Zn or that as a main constituent, a chromate layer thereon, and further a carboxylic modified epoxy resin layer containing scaled Al powder and globular Ni powder are laminated on at least one side surface. SOLUTION: As the lowest layer of a surface of a steel sheet, a metal plating layer 2 having Zn, or Zn alloyed with Ni Fe, etc., as a main constituent is formed. Its coating built-up is, for example, 10-99 g/m<2> . Then, as the second layer, a chromate layer 3 is formed to raise adhesion of the metal plating layer 2 to the uppermost layer of a resin layer 4. Further, as the third layer, the carboxylic modified epoxy resin layer 4 containing scaled Al powder and globular Ni powder. Thereby, excellent corrosion resistance to not only oxidation degradated gasoline, but also alcohol containing C1 ion and sulfate ion and alcohol mixed gasoline in which such the alcohol is mixed, can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel plate for a fuel container having excellent corrosion resistance, and more particularly to an oxidatively deteriorated gasoline and alcohol containing an organic acid and a peroxide, and Cl ions mixed into these by dew condensation or the like. The present invention relates to a steel plate for a fuel container having excellent corrosion resistance to water containing sulfate ions and the like.

[0002]

2. Description of the Related Art Conventionally, gasoline has been mainly used as fuel for automobiles. On the other hand, recently, studies have been made on alcohol or a mixture of alcohol and gasoline from the viewpoints of air environment conservation and price. By the way, as a container material for these automobile fuels, for example, a Pb-Sn alloy-plated steel sheet as disclosed in JP-B-57-61833 or JP-B-53-61833 has been used.
A steel sheet obtained by subjecting a Zn-plated steel sheet to a thick chromate treatment as shown in JP-A-19981 has been exclusively used.

[0003]

However, these Pb-
The Sn alloy plated steel sheet has the following problems. Pb
-The dissolution rate is high because the Sn alloy produces alcohol and a compound. When poor gasoline is used, the corrosion resistance to organic acids and peroxides formed in the gasoline due to oxidative deterioration is poor, so that the plating layer easily disappears and the ability to protect the steel sheet is reduced. Pb is contained and eluted in shredder dust from end-of-life vehicles, polluting the environment. On the other hand, a steel sheet obtained by treating a Zn-plated steel sheet with a thick chromate layer has the following problems. Since the chromate layer has low corrosion resistance to water or alcohol containing Cl ions, sulfate ions, and the like, corrosion products due to corrosion of Zn are generated, and the fuel filter for an automobile is easily clogged. Because the plating layer disappears in a relatively short time,
Poor ability to protect the steel sheet, and easy to produce holes.

[0004] By improving these disadvantages, it is possible to achieve both corrosion resistance (internal corrosion resistance) against alcohol alone or alcohol-mixed gasoline, particularly gasoline mixed with highly corrosive alcohol and formic acid, and corrosion resistance to the outside environment (external corrosion resistance). Proposals for this are disclosed in Japanese Patent Publication No. 2-18981, Japanese Patent Publication No. 2-18982, and Japanese Patent Publication No. 3-25349. In other words, Tokuhei 2-18981
Japanese Patent Publication No. 2-18982 and Japanese Patent Publication No. 3-25349 disclose a Pb-plated Sn alloy or a metal plating layer containing Sn as a main component, and a steel sheet having an organic resin film containing a metal powder as an upper layer. The publication describes a steel sheet having Zn or a metal plating layer containing Zn as a main component, and an organic resin film containing a metal powder as an upper layer.

However, in the organic resin films containing the metal powders described in the above three publications, 40 to 90% by weight of the organic resin is occupied by the phenoxy resin. The phenoxy resin itself is excellent in acid resistance and solvent resistance, but has a low affinity for metal powder, so it has sufficient corrosion resistance to oxidatively deteriorated gasoline and water or alcohol containing Cl ions and sulfate ions. There was a problem of not having it.

[0006] Under the circumstances described above, there has been a strong demand for the appearance of a steel plate for a fuel container which has good corrosion resistance even in a severe corrosive environment and has no environmental health problems.
Therefore, the present invention solves the problems of the conventional steel plates for fuel containers, and provides a fuel that has dramatically improved corrosion resistance to gasoline that has been oxidized and deteriorated and water or alcohol containing Cl ions, sulfate ions, and the like. An object of the present invention is to provide a steel sheet for containers.

[0007]

In order to develop a steel sheet having sufficient corrosion resistance to oxidized and degraded gasoline and water or alcohol containing Cl ions, sulfate ions, etc., the present inventors have mainly used organic resin metals. Affinity with powder,
We have studied and studied from the viewpoint of the acid resistance of the organic resin itself. As a result, a completely new finding was obtained that an epoxy resin modified with a carboxylic acid satisfies the desired properties and exhibits excellent performance. The present invention has been completed based on such findings, and the gist configuration thereof is as follows.

(1) At least one surface of a steel plate has Zn or a metal plating layer containing Zn as a main component as a lowermost layer,
A high corrosion resistance characterized by having a chromate layer on the metal plating layer and a resin layer of a carboxylic acid-modified epoxy resin containing flaky Al powder and spherical Ni powder on the chromate layer. Steel plates for fuel containers.

(2) The adhesion amount of the metal plating layer is 10 to 90 g /
m2, and the adhesion amount of the chromate layer is 10 to ² in terms of Cr.
00 mg / m ² , the amount of the resin layer attached is 3 to 15 g / m ² , and the resin layer contains 5 to 30% by weight of each of flaky Al powder and spherical Ni powder. Characterized by the above
The highly corrosion-resistant steel plate for a fuel container according to (1).

(3) The metal plating layer mainly composed of Zn is made of Ni,
Wherein the alloy plating layer contains one or more of Fe, Cr, Co, Al and Mg.
The steel plate for a highly corrosion-resistant fuel container according to (1) or (2).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. First, the steel plate for a fuel container according to the present invention has Zn or a metal plating layer containing Zn as a main component as the lowermost layer on the surface of the steel plate as illustrated in FIG. When this metal plating layer is used on the inner surface of a fuel container, it has a sufficiently low potential with respect to the steel sheet in oxidized and deteriorated gasoline and water or alcohol containing Cl ions, sulfate ions and the like. For this reason, even in a small exposed portion of the steel sheet caused by the working, there is an effect of sacrificial corrosion prevention of the steel sheet, suppressing perforation-like corrosion of the steel sheet, and improving perforation resistance. In particular, Ni, Fe, Cr,
The alloy plating layer composed mainly of Zn alloyed with Co, Al, Mg, etc. has a high corrosion resistance of the plating layer itself while maintaining the sacrificial corrosion protection property, so that the further improvement of the hole resistance is further improved. It is possible. As the metal plating layer, a known alloy plating such as Zn, Zn-Ni, Zn-Fe, Zn-Cr, Zn-Co, or Zn-Ni-Co formed by an electroplating method is preferable. In the hot-dip galvanizing method, hot-dip galvanizing (GI), Zn-Fe-Al (alloyed hot-dip galvanizing), Zn-Al (Zn-5 wt% Al, Zn-55 wt%
Known plating such as Al) and Zn-Mg-Al is suitable. Further, even when this steel sheet is used on the outer surface, the steel sheet also has sacrificial corrosion resistance to the steel sheet under an environment where drying and wetting of an aqueous solution containing Cl ions as a corrosion promoting factor are repeated, and the metal plating layer It forms a stable Zn corrosion product by itself and has a low corrosion rate, so that it has high corrosion resistance. Further, by disposing a chemical conversion film of a phosphate treatment film or a chromate layer film and a coating resin film on the metal plating layer, higher corrosion resistance can be obtained. The adhesion amount of the metal plating layer is 10 g / m ² as a lower limit at which a sufficient effect on corrosion resistance can be obtained.
The above is necessary, while 90 g / m ² or less is required as an upper limit for obtaining sufficient weldability.

Next, a chromate layer is formed as a second layer (upper layer of the metal plating layer). The chromate layer is formed for the purpose of obtaining good adhesion between Zn or a metal plating layer containing Zn as a main component and the uppermost resin layer. The chromate layer is a film composed of trivalent chromium and hexavalent chromium containing chromium hydrated oxide as a main component, and contains silica sol in a ratio of SiO ₂ / Cr = 0 to 6 with respect to the Cr equivalent weight. In such a case, the corrosion resistance is further improved. The chromate layer is obtained by drying at a temperature of 80 to 150 DEG C. immediately after coating. In order to obtain good adhesion, the amount of chromate layer
10 mg / m ² or more is required in conversion. This chromate layer itself contributes to corrosion resistance.However, if an excessively thick film is formed to increase the corrosion resistance, cohesive failure occurs inside the chromate layer due to deformation during processing, and the organic resin film peels off. 200
It is desirable that the concentration be not more than mg / m ² .

Further, as a third layer (upper layer of the chromate layer), a carboxylic acid-modified epoxy resin layer containing scale-like Al powder and spherical Ni powder is formed. As the resin, a high corrosion resistance can be obtained by an epoxy resin whose terminal is modified with a carboxylic acid. It is considered that the remarkable improvement in the corrosion resistance is due to the remarkable improvement in the acid resistance of the epoxy resin due to the carboxylic acid modification. The experiment that served as the basis is described. That is, a 5 μm thick carboxylic acid-modified epoxy resin, 5 μm
Two types of steel sheets each having a thick epoxy resin coated on the top surface of the Zn-Ni plating layer were placed in an aqueous solution having a formic acid concentration of 1000 ppm.
Immersion at 30 ℃ for 30 days.
Observed at 00x. As a result, no change was observed on the surface of the resin coated with the carboxylic acid-modified epoxy resin as compared with that before the test. On the other hand, in the case of the epoxy resin coating, the resin film was broken in some places and corrosion products were observed. It is considered that the reason why the resin film was broken was that the acid resistance of the resin film was deteriorated and the film strength was reduced.
In addition to the above epoxy resin, amine-modified epoxy resin, rubber-modified epoxy resin, etc. were subjected to the same test,
Corrosion products penetrating the resin film were observed as in the case of this epoxy resin, and it was revealed that corrosion resistance was poor.

The carboxylic acid-modified epoxy resin mentioned here is a dicarboxylic acid such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid. An epoxy resin in which phthalic acid, phthalic acid, terephthalic acid, etc. are reacted with an epoxy resin and bonded to each other. In the case of a bisphenol A type, it is formed by a reaction schematically shown in FIG. Refers to a structure. In this case, as the epoxy resin, bisphenol A type
(Referred to as BA type) resin, brominated BA resin, bisphenol F diglycidyl ether, novolak glycidyl ether, hexahydrophthalic acid glycidyl ester, dimer acid glycidyl ester, triglycidyl isocyanate, tetraglycidyl diaminodiphenylmethane,
Epoxidized polybutadiene, epoxidized soybean oil, 3, 4
Epoxy resins such as epoxy-6 methylcyclohexylmethyl carboxylate and 3,4 epoxy-cyclohexylmethyl carboxylate are used.

In such a carboxylic acid-modified epoxy resin, flaky Al powder and spherical Ni powder are each used as a metal powder.
By containing up to 30% by weight, it is possible to further improve the corrosion resistance. Al powder is a metal effective for forming a passivation film and imparting corrosion resistance.Since the stability of the passivation film in acid is high, it has high corrosion resistance in environments containing peroxides and organic acids. to enable. This Al powder shows remarkably high corrosion resistance especially in combination with a carboxylic acid-modified epoxy resin. It is presumed that the reason is that the carboxyl group has good adhesion to Al, and this acts as an obstacle to the transfer of water, alcohol and gasoline to the Al powder surface. When the content of Al in the resin is 5% by weight or more, a remarkable effect of improving the corrosion resistance appears, but when it exceeds 30% by weight, the weldability deteriorates. Therefore, it is preferable that the content be 5 to 30% by weight. .
Further, the shape of the Al powder is preferably scaly from the viewpoint of improving corrosion resistance due to shielding properties.

[0016] Ni powder itself has high corrosion resistance itself, and at the time of rolling of the roll during welding, makes the current between the steel plate and the roll good, and widens the proper welding current range.
Improves continuous weldability. The content of Ni powder in the resin is
When the content is more than 5% by weight, these remarkable effects appear. However, when the content exceeds 30% by weight, not only does the electrical conductivity not improve, but also the adhesion of the resin to the steel plate is impaired. desirable. Further, the shape of the Ni powder is preferably spherical from the viewpoint of securing a current path by rolling down the electrode during welding. The weldability can be further improved by adjusting the particle size of the Ni powder so that the average particle size is in the range of 50 to 90% of the resin film thickness.

The amount of the resin layer containing the metal powder described above is preferably in the range of 3 to 15 g / m ² . The amount of adhesion is
If it is less than 3 g / m ² , the effect of improving the corrosion resistance will be insufficient, while if it exceeds 15 g / m ² , the weldability will deteriorate. As a method of forming a resin layer on a steel sheet having a chromate layer, for example, a carboxylic acid-modified epoxy resin having a molecular weight of 1,000 to 20,000 and a scale-like Al based on the total weight of the resin layer are used.
A liquid resin paint containing 20% of powder and 20% of granular Ni powder and having an adjusted viscosity by adding an organic solvent for easy application is applied using a roll coater, a flow coater or the like. After that, the maximum temperature is 100 ~ 250 ℃, the holding time is 10
Drying may be performed in a range of 120 seconds, water-cooled, air-cooled, and wound.

[0018]

The present invention will be specifically described below with reference to examples. A cold-rolled steel sheet (SPCE) having a thickness of 0.8 mm was used as an original sheet to obtain a steel sheet for a high corrosion-resistant fuel container according to the present invention and various comparative materials as shown in Tables 1 and 2.

[0019]

[Table 1]

[0020]

[Table 2]

The abbreviations of the plated steel sheets used are shown below. GA: Alloyed hot-dip galvanized steel sheet (Fe content: 8 to 12% by weight) GI: Hot-dip galvanized steel sheet (zero spangle material) GL: Zn-55% by weight Al steel sheet Zn: Electro-galvanized steel sheet Zn-Ni: Electric Zn -Ni alloy plated steel sheet (Ni content 12% by weight) A chromate layer treatment solution was roll-coated on each of these plated steel sheets and dried at 120 ° C. Subsequently, a resin coating containing scale-like Al powder and spherical Ni powder diluted with a solvent was roll-coated and dried at 150 ° C. In this way, one-sided coating (Nos. 1 to 5, 13 to 18, 25, 27, 28, 30, 3
1) and both sides applied (No. 6-12, 19-24, 26, 2
9, 32-35). As comparative materials, those prepared by applying a resin film described in Japanese Patent Publication No. 3-25349 on various plated steel sheets (Nos. 3, 15, 29), Pb-Sn alloy plated steel sheets, and hot-dip Al-coated steel sheets were also manufactured. .

The obtained test steel sheet was subjected to a corrosion resistance test and a seam welding test by the following methods. (A) Seam weldability evaluation method Welding conditions・ Electrode: chrome-copper alloy, trapezoidal electrode (tip R: 15mmφ) ・ Welding method: lap seam welding ・ Pressure: 500 kg ・ Electrification cycle: 2 cycles on-1 cycle off・ Welding speed: 3m / min ・ Welding current: Welding by changing the current in 0.5 kA steps in the range of 1 to 20 kA Welding under the above conditions to make a sample The difference between the current value and the upper limit current value at which blowholes did not occur in the welded portion was calculated to determine an appropriate current range. (B) Corrosion resistance test method A test piece punched into 35 mmφ was used.
The test surface was placed on the bottom of the ml container with the evaluation surface facing upward, 30 ml of the test solution was injected, the solution was kept at 60 ° C. for 2 weeks, and the weight loss of the metal plating layer was measured by X-ray fluorescence. The organic coated test piece was measured after rubbing off the organic film with a solvent. As the test liquid, a mixed solution of gasoline and methanol to which peroxide was added and a mixed solution of methanol and water to which formic acid, acetic acid, and sodium chloride were added were used as shown below. Gasoline + methanol mixed solution -Commercial regular gasoline: 45% by weight-Reagent primary methanol: 45% by weight-Reagent primary lauroyl peroxide: 15% by weight mixed solution of methanol + water -Reagent primary methanol: 50% by weight・ Water (containing 100 mg / l each of formic acid, acetic acid and sodium chloride)… 50% by weight

The test results of the obtained seam weldability and corrosion resistance are shown in Tables 1 and 2. The steel sheet of the present invention has a low metal elution amount and excellent corrosion resistance to any of a gasoline + methanol mixed solution containing peroxide and a methanol + water mixed solution containing formic acid, acetic acid and sodium chloride. You can see that it is doing. Also, it can be seen that the appropriate current range in seam welding is 1.5 to 4.0 kA, which is a practically wide range.

[0024]

As described above, according to the present invention,
It is possible to provide a fuel container steel sheet having excellent corrosion resistance to not only oxidized and deteriorated gasoline, but also alcohol containing Cl ions and sulfate ions, alcohol-mixed gasoline obtained by mixing such alcohols, and the like. Moreover, according to the present invention, a steel plate for a fuel container excellent in seam weldability can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a steel plate for a highly corrosion-resistant fuel container according to the present invention.

FIG. 2 is a diagram showing an example of the structure of a carboxylic acid-modified epoxy resin used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel plate 2 Metal plating layer 3 Chromate layer 4 Resin layer

Claims (3)

[Claims] At least one surface of a steel sheet has, as a lowermost layer, a metal plating layer containing Zn or Zn as a main component, a chromate layer above the metal plating layer, and an upper layer of the chromate layer. A highly corrosion-resistant steel plate for a fuel container, comprising a resin layer comprising a carboxylic acid-modified epoxy resin containing flaky Al powder and spherical Ni powder. 2. The coating weight of the metal plating layer is 10 to 90 g / m.
² , and the adhesion amount of the chromate layer is 10 to 20 in terms of Cr.
A 0 mg / m ^2, the adhesion amount of the resin layer is 3 ~15g / m ^2, each scaly Al powder and the spherical Ni powder in the resin layer
2. The composition according to claim 1, wherein the content is 5 to 30% by weight.
2. The steel sheet for a highly corrosion-resistant fuel container according to claim 1. 3. The method according to claim 1, wherein the metal plating layer containing Zn as a main component comprises Ni,
The steel plate for a highly corrosion-resistant fuel container according to claim 1 or 2, wherein the steel plate is an alloy plating layer containing at least one of Fe, Cr, Co, Al and Mg.