JPH11151778A - High corrosion resistant steel plate for fuel tank - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To have excellent corrosion resistance to alcohol itself or gasoline mixed with alcohol and formic acid, and to have excellent corrosion resistance to the atmospheric environment in which snow-melted salt or sea salt particles fly, and excellent press working. Of fuel tank steel with high resistance and resistance weldability. SOLUTION: Zn or Z is formed as a lowermost layer on both surfaces of a steel sheet.
It has a metal plating layer containing n as a main component, has a chromate layer on both upper layers, and further contains an amine-modified epoxy resin, a flaky Ni powder, and a lubricant on the upper layer on one surface. Having a metal powder-containing lubricating organic resin layer to be,
And at least one resin having at least one functional group selected from a hydroxyl group, an isocyanate group, a carboxyl group, a glycidyl group and an amino group in the upper layer of the other surface, a lubricant, and silica as main components. A steel plate for a fuel tank with high corrosion resistance, comprising a lubricating organic resin layer.

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 tank, and more particularly to a steel plate having excellent corrosion resistance to alcohol itself or gasoline in which alcohol and formic acid are mixed (hereinafter referred to as "inner corrosion resistance"). The present invention relates to a steel plate for a fuel tank having excellent corrosion resistance to the air environment in which sea salt particles fly (hereinafter referred to as “outside corrosion resistance”), and having excellent press workability and resistance weldability.

[0002]

2. Description of the Related Art Conventionally, gasoline has been mainly used as a fuel for automobiles. However, in recent years, studies have been made on alcohol or a mixture of alcohol and gasoline from the viewpoints of air environment protection and price. I have.

Therefore, the corrosion resistance (internal corrosion resistance) to alcohol alone or to gasoline mixed with alcohol, particularly gasoline mixed with highly corrosive alcohol and formic acid.
Proposals to achieve both corrosion resistance to the outside environment (external corrosion resistance) are disclosed in Japanese Patent Publication No. 2-19881 and Japanese Patent Publication No. 2-1.
No. 8982 and Japanese Patent Publication No. 3-25349.

That is, Japanese Patent Publication No. Hei 2-18981 discloses that
A steel plate having a metal plating layer containing a Pb / Sn alloy or Sn as a main component and an organic resin film containing a metal powder as an upper layer is disclosed in JP-B-2-18982 and JP-B-3-25349.
No., Zn or a metal plating layer containing Zn as a main component,
A steel sheet having an organic resin film containing a metal powder as an upper layer is described.

[0005]

The metal powder-containing organic resin films described in the above three publications have a phenoxy resin that accounts for 40 to 90% of the organic resin.
Although the phenoxy resin itself is excellent in acid resistance and solvent resistance, it has a low affinity for metal powder, so that the metal powder is peeled off during press working, and the inner surface corrosion resistance of the damaged portion deteriorates. Also, the parts that are not damaged,
The fuel easily stays between the resin and the metal powder, and the inner surface corrosion resistance deteriorates. Corrosion resistance is also deteriorated on the outer surface side of the fuel tank due to insufficient affinity between the phenoxy resin and the metal powder.

Further, in any of the steel sheets, since the resin film contains a hardening agent as an essential component, when the degree of hardening is high, it is difficult to thermally decompose, it is difficult to remove the film during the nugget formation process, and the resistance weldability is reduced. I do. In other words, even if the energization point is secured by the metal powder, the base material around the remaining film causes poor welding, so that sufficient wrap between nuggets cannot be obtained and fuel leakage occurs. In some cases, sufficient welding strength cannot be obtained and peeling occurs. In addition, when the curing degree is low and an unreacted curing agent is contained, corrosion factors (acids, chloride ions, etc.) are likely to enter due to the low cohesive strength and hydrophilicity of the portion, and the corrosion resistance is reduced.

[0007] As described above, various performance defects remain, and they have not yet been put to practical use. Thus, the present invention overcomes these shortcomings of current fuel tank materials,
In particular, it has excellent internal corrosion resistance against gasoline mixed with methanol itself or formic acid generated by the oxidation of methanol, and has excellent external corrosion resistance against the atmospheric environment in which snow-melting salt or sea salt particles fly, and excellent press working in the fuel tank manufacturing process. An object of the present invention is to provide a steel plate for a fuel tank exhibiting resistance and resistance weldability.

[0008]

Means for Solving the Problems The present inventors mainly have an affinity between an organic resin and a metal powder, an acid resistance of the organic resin itself,
As a result of intensive studies on resistance weldability and lubricity,
On one side, a resin layer containing an amine-modified epoxy resin, a lubricant, a Ni powder of a specific shape, and silica as necessary, and on the other side, a hydroxyl group, an isocyanate group, a carboxyl group, a glycidyl group and an amino group. By using at least one kind of resin having at least one kind of functional group selected from a group, a resin layer mainly composed of silica and a lubricant, it is possible to solve the above problem at once by a completely new finding. Thus, the present invention has been completed.

That is, the present invention provides a steel plate having Zn or a metal plating layer containing Zn as a main component as a lowermost layer on both surfaces of the steel sheet, a chromate layer on both upper layers, and an upper layer on one of the surfaces. Has an amine-modified epoxy resin, flaky Ni powder, and a metal powder-containing lubricating organic resin layer containing a lubricant as a main component, and a hydroxyl group, an isocyanate group, a carboxyl group, and a glycidyl group as an upper layer on the other surface. And at least one resin having at least one functional group selected from amino groups and amino groups, a lubricant, and a lubricating organic resin layer containing silica as a main component. It is a steel plate.

Further, the metal powder-containing lubricating organic resin layer is composed of 20 to 400 parts by weight of flaky Ni powder and 0.1 to 0.1 parts by weight of a lubricant based on 100 parts by weight of the amine-modified epoxy resin.
5 parts by weight. Further, the present invention provides a steel plate having Zn or a metal plating layer containing Zn as a main component on both surfaces of the steel plate, a chromate layer on both of them, and an amine-modified epoxy on one of the surfaces. Resin, flaky Ni powder, a lubricant, and a metal powder-containing lubricating organic resin layer containing silica as a main component, and a hydroxyl group, an isocyanate group, a carboxyl group, a glycidyl group and an upper layer on the other surface. A steel plate for a highly corrosion-resistant fuel tank, comprising: a lubricating organic resin layer containing at least one resin having at least one functional group selected from amino groups, a lubricant, and silica as main components. It is.

Further, the metal powder-containing lubricating organic resin layer is composed of 20 to 400 parts by weight of flaky Ni powder and 0.1 to 100 parts by weight of a lubricant based on 100 parts by weight of the amine-modified epoxy resin.
5 parts by weight, silica is 40 parts by weight or less, and the amine-modified epoxy resin is 0.3 equivalent to 1 equivalent of epoxy group.
A composite resin obtained by adding an amine compound having a weight average molecular weight of 5,000 to 50,000, and the flaky Ni powder having an average major axis of 8 to 25 μm.
m, average minor axis is 1 to 12 μm, and average thickness is 0.5 to 5.
0 μm, wherein the lubricant is a polyolefin wax and / or polytetrafluoroethylene, has an average particle size of 1 to 10 μm, and a softening point of 70 to 150 ° C.

Further, the lubricating organic resin layer contains 1 to 40 parts by weight of a lubricant based on 100 parts by weight of the resin;
Silica is 5 to 80 parts by weight, the lubricant in the lubricating organic resin layer is a polyolefin wax and / or polytetrafluoroethylene, the softening point of the lubricant is 70 to 150 ° C, and the average particle size is And the glass transition temperature (Tg) of the lubricating organic resin layer is from 0 to 90 μm.
It is a steel plate for fuel tanks with high corrosion resistance of ℃.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below.
The steel sheet of the present invention is formed of a coating layer composed of three layers on both sides. Lowermost layer (first layer) and upper layer (second layer) of steel sheet
Is the same on both sides, and the third coating layer on the surface of the steel plate is different between one surface used on the inner surface side of the fuel tank and the other surface used on the outer surface side.

(Metal Plating Layer) The steel sheet for a highly corrosion resistant fuel tank of the present invention has a metal plating layer containing Zn or Zn as a main component as the lowermost layer (first layer) on the surface of the steel sheet. Since the metal plating layer is a metal layer showing a lower potential than the iron base material in alcohol and alcohol mixed fuel, red rust and perforation are suppressed by the sacrificial corrosion prevention effect of Zn even in the pressed part where the plating layer is damaged. And has the effect of improving corrosion resistance.

In particular, Zn-Ni alloy plating, Zn-Co
Alloy plating, Zn-Fe alloy plating, Zn-Al alloy plating, Zn-Ni-Cr alloy plating, Zn-Ni-Co
The metal plating layer mainly composed of Zn, such as alloy plating,
Since the corrosion resistance of the plating layer itself is high while maintaining the sacrificial anticorrosion performance, it is possible to further improve the perforation resistance. These plating layers are formed by a known electroplating method or hot-dip plating method.

The basis weight of such Zn or a metal plating layer containing Zn as a main component is preferably from 10 to ²⁰⁰ g / m ² . More preferably, it is 20 to 100 g / m ² . When the basis weight of plating is less than 10 g / m ² , the effect of hiding the steel sheet surface becomes insufficient, and the corrosion resistance required for the lower layer becomes insufficient.
If it exceeds 200 g / m ² , the corrosion resistance required for the lower layer is saturated. The basis weight of the plating layer may be the same for the side used for the inner surface and the side used for the outer surface of the fuel tank, but the plating thickness on the outer surface may be larger than the inner surface for reasons of improving the outer corrosion resistance.

(Chromate layer) Next, a chromate layer is formed on both front and back surfaces as a second layer (upper layer of metal plating). The chromate layer is formed to improve the adhesion between Zn or a metal plating layer containing Zn as a main component and the uppermost resin layer. The chromate layer is a coating composed of trivalent chromium and hexavalent chromium containing chromium hydrated oxide as a main component.

The amount of the chromate layer deposited is preferably from 5 to 200 mg / m ² per one surface in terms of chromium metal. More preferably, it is 10 to 100 mg / m ² . 5 mg / m ²
If it is less than 30, the adhesion to the upper organic film is insufficient, so that the film on the sliding portion is peeled off during press working, and in some cases, the plating layer is peeled off. Further, since the amount of adhesion is small, the hexavalent chromium component to be used for self-healing is insufficient, and the corrosion resistance of the processed portion on the inner and outer surfaces is insufficient due to the peeling of the plating layer. If it exceeds 200 mg / m ² ,
The chromate layer itself becomes very brittle, the chromate layer peels off at the processed part, and the accompanying organic film peels off. For this reason, the corrosion resistance of the processed portions on the inner and outer surfaces is insufficient. The attachment amount of the chromate layer may be the same or different between the side used for the inner surface and the side used for the outer surface of the fuel tank.

As the uppermost layer (third layer), one surface is coated with a flaky Ni powder, an amine-modified epoxy, a lubricant, and if necessary, a lubricating organic resin containing a metal powder containing silica as a main component. Is coated with a lubricating organic resin comprising a resin, silica and a lubricant. The metal powder-containing lubricating organic resin layer has excellent weldability, gasoline resistance, lubricity, etc., and is preferably used as the inner surface of the fuel tank (that is, the side in contact with gasoline). The lubricating organic resin layer has corrosion resistance, lubricity Therefore, it is preferable to use it as the outer surface side of the fuel tank.

(Metal Powder-Containing Lubricating Organic Resin Layer) The metal powder-containing lubricating organic resin layer is a metal having excellent corrosion resistance to alcohol, especially methanol itself, or gasoline mixed with formic acid formed by oxidization of methanol. It is composed of a powder, a resin and a lubricant component, and serves as an anticorrosion layer for preventing direct contact between the metal plating layer and the chromate layer and the alcohol fuel.

(Amine-Modified Epoxy Resin) Needless to say, the resin component used in the present invention has excellent corrosion resistance to gasoline and alcohol-based fuels, and has excellent coating adhesion to a chromate layer and press workability. It exhibits excellent characteristics. That is, by using the amine-modified epoxy resin, excellent press workability, corrosion resistance to alcohol-based fuel, and coating film adhesion to the chromate layer are ensured.

The amine-modified epoxy resin is obtained by modifying an epoxy resin with an amine compound, and is preferably one obtained by modifying the terminal of an epoxy resin with an amine compound.
More preferably, both terminals are modified with an amine compound. Here, examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, cycloaliphatic epoxy resin, hydantoin type epoxy resin, novolak type epoxy resin, and glycidyl ester type epoxy resin. The epoxy equivalent of these epoxy resins is preferably from 180 to 5,000. Specific examples are Epicoat 1010, 1009, 1007, 100
4, 1001 (both manufactured by Yuka Shell Epoxy Co., Ltd.)
And the like. These may be used alone or in combination of two or more. Further, a reaction product obtained by reacting a bisphenol type epoxy resin such as a bisphenol A type epoxy resin or a bisphenol F type epoxy resin with bisphenol A or bisphenol F may be used. Among these, bisphenol A type epoxy resin, bisphenol F type epoxy resin and bisphenol type epoxy resin and bisphenol A or bisphenol A from the wide range of manufacturing conditions for stably obtaining paint stability, press workability, and inner surface corrosion resistance What reacted with bisphenol F is preferable.

The amine compound is n-propylamine, i
so- propylamine, n- butylamine, sec- butylamine, tert- butylamine, diethylamine, ethylenediamine, diethylenetriamine, triethylenediamine, tetramethyl ethylenediamine, propylenediamine, N- methylpiperidin Bae Rajin, ethanolamine,
Diethanolamine, N-methylethanolamine, i
Examples thereof include so-propanolamine, diisopropanolamine, n-propanolamine, ethylethanolamine, and 3-methanolpiperidine. Of these, alkanolamine and dialkanolamine are particularly preferred.

The number of moles of the amine compound added to one equivalent of the epoxy group of the epoxy resin is preferably from 0.3 to 1.0 mol, more preferably from 0.5 to 0.8 mol. If the number of moles of the amine compound is less than 0.3, the degree of amine modification is insufficient,
The affinity between the metal powder and the epoxy resin is reduced, and the metal powder is detached from the film during press working. If the degree is severe, peeling of the plating layer occurs, resulting in poor press workability. For the same reason, the corrosive liquid tends to stay between the resin and the metal powder in the film, and it is difficult to obtain sufficient hydrophobicity, so that formic acid aqueous solution is easily introduced into the film.
Insufficient internal corrosion resistance to highly corrosive methanol fuel. When the number of moles of the amine compound exceeds 1.0 mole, the excess is not economical without being added to the epoxy group,
Excess amine increases water absorption and lowers inner corrosion resistance.

The weight average molecular weight of the amine-modified epoxy resin is preferably 5,000 to 50,000, more preferably 10,000 to 40,000. When the molecular weight is less than 5,000, the molecular weight of the resin is too low, so that the intermolecular distance is insufficient and the toughness of the film is reduced. For this reason, the film is shaved during the press working, and the press workability is reduced. Molecular weight 5
If it is more than 0000, the amount of amine added to the epoxy group is small, so that the affinity between the resin and the metal powder is insufficient, the metal powder is detached from the film at the time of press working, and the inner surface has corrosion resistance. Run out.

(Scaly Ni Powder) The purpose of the addition of the scaly Ni powder is to improve resistance weldability and corrosion resistance. That organic resin film has a generally high electrical insulating properties, and since the thickness of the resin film is about 0.5~9μm position, can not be expected at all the exposed convex portions of the steel sheet, it is difficult to resistance welding . Therefore, the present invention disperses a required amount of metal powder in the organic resin film on the inner surface side of the gasoline tank, and enhances the conductivity of the film. Ni is most useful for resistance weldability because it has excellent corrosion resistance to methanol and high specific resistance. By making the shape of Ni scaly, intrusion of gasoline, alcohol, formic acid and the like is prevented, and the corrosion resistance is improved. Conventionally, Al has been used to improve resistance weldability and the like.
l has a lower specific resistance and melting point than Ni and is not optimal for welding. In particular, it is preferable to add only flaky Ni powder.

The size of the flaky Ni powder is such that the average major axis is 8 to
25 μm, average minor axis is 1 to 12 μm, average thickness is 0.5
５5.0 μm. More preferably, the average major axis is 10
-20 μm, average minor axis 5-10 μm, average thickness 0.
It is 8 to 3 μm. If at least one of the average major axis and the average minor axis is smaller than the above range, the shielding properties against gasoline, alcohol, formic acid and the like will be low, and the internal corrosion resistance will be reduced. On the other hand, if at least one of the average major axis and the average minor axis is larger than the above range, the strength of the coating decreases, powdering occurs, and the inner surface corrosion resistance of the pressed portion decreases. When the average thickness is less than 0.5 μm, the inner surface corrosion resistance is reduced,
When the average thickness exceeds 5 μm, Ni exposed on the coating film surface
Since the proportion of the powder increases, press formability decreases.

The amount of the flaky NI powder to be added is 20 to 400 parts by weight, preferably 30 to 100 parts by weight, based on 100 parts by weight of the amine-modified epoxy resin. If the amount is less than 20 parts by weight, the number of current-carrying points is insufficient, and the resistance weldability is reduced. If the amount exceeds 400 parts by weight, the film itself becomes brittle, and the powdering resistance and the inner surface corrosion resistance decrease. Preferably, the flaky Ni powder is surface-treated with a silane coupling agent.
When surface treatment is performed with a silane coupling agent, affinity and reactivity with the amine-modified epoxy resin are increased, and the bond between the two is strengthened. Therefore, penetration of alcohol, formic acid, and the like is prevented, and corrosion resistance is improved. Further, the powdering property at the time of press working is also improved. Examples of the silane coupling agent include epoxy silane, vinyl silane, mercapto silane, amino silane, and the like. Of these, epoxysilane and aminosilane are preferred. As aminosilane coupling agents, N-β (aminoethyl) -γ
-Aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane and the like are preferred. As the epoxysilane coupling agent, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and the like are preferable.

(Lubricant) A lubricant is added to impart self-lubricating property to the organic resin film on the inner surface. In the present invention,
By projecting the lubricant onto the surface of the organic film, friction between the steel plate and the mold during press working is reduced, and damage to the resin film is prevented. As such a lubricant, polyethylene-based,
Polyolefin waxes such as polypropylene and polybutene and polytetrafluoroethylene are preferred. These may be used alone or in combination of two or more. These are preferred because they have excellent lubricity and excellent chemical resistance to gasoline, alcohol, formic acid, lubricating oil and the like.

The average particle size of the lubricant is preferably from 1 to 10 μm, more preferably from 2 to 8 μm. Average particle size is 1
When it is less than μm, the amount of the lubricant projecting from the organic film is small and the press workability is reduced. If it exceeds 10 μm, it is easy to detach from the film during press working. The softening point of the lubricant is preferably from 70 to 150C. Those having different softening points may be mixed. When the softening point is less than 70 ° C., under severe pressing conditions involving heat generation, the elastic modulus of the lubricant is significantly reduced, and press workability is poor. When the softening point is higher than 150 ° C., the softening of the lubricant is insufficient, and the press workability is poor. The amount of the lubricant is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the amine-modified epoxy resin. It is more preferably 0.1 to 4 parts by weight. If the amount is less than 0.1 part by weight, the lubricating property is insufficient, and the film is damaged during the press working, so that the corrosion resistance is reduced. If the amount exceeds 5 parts by weight, desorption of the lubricant is likely to occur during press working, and the corrosion resistance deteriorates.

(Silica) It is not always necessary to add silica, but if it is added, the silanol groups on the silica surface react with the chromate layer and other components in the organic film, and the like, so that the adhesion of the film is improved. And good corrosion resistance. Silica is colloidal silica (for example, Snowtex-O or Snowtex-N manufactured by Nissan Chemical Industries, Ltd.),
Organo-silica sol (eg, Nissan Chemical Co., Ltd. ethyl cellosolve silica sol), silica powder (eg, Aerosil Co., Ltd. gas-phase silica powder), and organic silicate (eg, ethyl silicate, etc.) that becomes silica by condensation by itself (Used in combination with an acid catalyst). The particle size of the silica powder is preferably from 5 to 70 nm in order to uniformly disperse the silica.

The amount of silica added is 40 parts by weight or less, and more preferably 5 parts by weight, based on 100 parts by weight of the amine-modified epoxy resin.
-20 parts by weight are preferred. If the amount exceeds 40 parts by weight, the press workability of the film is reduced, and the film is easily cracked, resulting in poor corrosion resistance. Further, as other additives, additives such as a pigment, a thixotropic agent, a dispersant, a thixotropic agent and a precipitation inhibitor can be added to the film.
The average thickness of the metal powder-containing lubricating resin is 0.5 to 9 after drying.
μm is preferred. If it is less than 0.5 μm, the internal corrosion resistance is insufficient. If it exceeds 9 μm, the corrosion resistance is saturated, and the press workability and the resistance weldability are reduced.

An example of a method for forming this film will be described. The amine-modified epoxy resin is prepared by dissolving the epoxy resin in various organic solvents (such as hydrocarbons, esters, ketones, alcohols, and ethers), and then adding an amine compound.
It is obtained by reacting at room temperature to 100 ° C for 4 to 5 hours. Next, a metal powder, a lubricant, silica, and other additives are added to the obtained amine-modified epoxy resin solution, and these are dispersed with a sand mill, an attritor, or the like to prepare a metal powder-containing lubricating organic resin paint. The coating is applied by a known method such as a roll coater or a bar coater,
Dry at 00 ° C.

(Lubricating Organic Resin Layer) Next, the lubricating organic resin layer will be described. (Organic resin) The lubricating organic resin layer is a lubricating resin layer in which silica is composited. The organic resin used here may be at least one resin having at least one functional group selected from a hydroxyl group, an isocyanate group, a carboxyl group, a glycidyl group and an amino group. Specific examples include an epoxy resin, an alkyd resin, an acrylic resin, a urethane resin, a polyvinyl butyral resin, a phenol resin, and a melamine resin. Among them, polyvinyl butyral resin is preferable from the viewpoint of corrosion resistance and the like.

(Lubricant) A lubricant is added for imparting self-lubricating property to the organic resin film on the outer surface. In the present invention,
By projecting the lubricant onto the surface of the organic film, friction between the steel plate and the mold during press working is reduced, and damage to the resin film is prevented. As the lubricant, those described above for the metal powder-containing lubricating organic resin layer can be used, and the preferable range of the melting point of the lubricant is also as described above.

The average particle size of the lubricant is preferably from 1 to 7 μm, more preferably from 2 to 6 μm. Average particle size is 1
When it is less than μm, the amount of the lubricant projecting from the organic film is small and the press workability is reduced. When it exceeds 7 μm, it is easy to detach from the film during press working. The reason why the particle size of the lubricant in the lubricating organic resin layer used on the outer surface is smaller than the particle size of the lubricant in the lubricating organic resin layer containing the metal powder used on the inner surface is that the outer film has a smaller particle size than the inner film. Because it is thin.
The amount of the lubricant added is at least one resin having at least one functional group selected from a hydroxyl group, an isocyanate group, a carboxyl group, a glycidyl group and an amino group.
1 to 40 parts by weight, and more preferably 5-2 to 100 parts by weight
0 parts by weight is preferred. If the amount is less than 1 part by weight, the lubricity is insufficient, and the film is damaged at the time of press working, so that the corrosion resistance is reduced. If the amount exceeds 40 parts by weight, desorption of the lubricant is likely to occur during press working, and the corrosion resistance deteriorates. Since no metal powder is added to the outer coating, a larger amount of lubricant can be added than the inner coating. In addition, during press working, the outer surface side is more likely to be damaged, so it is preferable to add more lubricant than the inner surface side.

(Silica) The addition of silica causes the silanol groups on the silica surface to react with the above-mentioned resin or chromate layer to form an inorganic-organic composite film having high corrosion resistance.
This is because the adhesion of the organic resin film on the outer surface of the tank is improved, and the corrosion resistance is improved. As the silica, those described above can be used. The addition amount of silica is preferably from 5 to 80 parts by weight based on 100 parts by weight of at least one resin having at least one kind of functional group selected from a hydroxyl group, an isocyanate group, a carboxyl group, a glycidyl group and an amino group. And more preferably 20 to 60 parts by weight. If the amount is less than 5 parts by weight, the corrosion resistance is not improved. If the amount is more than 80 parts by weight, the film becomes brittle, and the mold is seized at the time of molding to deteriorate the press workability. In addition, since silica has poor thermal decomposability, resistance weldability decreases. Since no metal powder is added to the coating used on the outer surface, the amount of silica added can be increased compared to the inner surface, and the outer surface has excellent corrosion resistance.

The glass transition temperature (Tg) of the above lubricating organic resin is preferably from 0 to 90 ° C., more preferably from 0 to 85 ° C. Outside this range, the press workability is poor, and the corrosion resistance of the pressed portion is also poor. Organic coatings that require press workability are generally required to have a high Tg (for example, 90 ° C. or higher), but the coating of the present invention has a structure in which a lubricant is projected from the coating. There is no need to increase the Tg of the coating so much. Further, as other additives, additives such as a pigment, a thixotropic agent, a dispersant, a thixotropic agent, a suspending agent and an organic solvent can be added to the film. The thickness of the lubricating organic resin film after drying is preferably 0.5 μm to 1.5 μm.
If the film thickness is less than 0.5 μm, the irregularities on the surface of the steel sheet cannot be filled, and the corrosion resistance decreases. If it exceeds 1.5 μm, the corrosion resistance is improved, but the resistance weldability is significantly reduced. In addition, the wettability with the metal brazing is remarkably poor, and the brazing property is also remarkably reduced.

When the steel sheet for a high corrosion resistant fuel tank of the present invention is pressed, there is no problem even if the lubricating oil is not applied and the lubricating oil is applied according to the difficulty of the press. From the viewpoint of prevention, application of lubricating oil is effective. An example of a method for forming this film will be described. After dissolving the organic resin in the organic solvent, silica is added and the mixture is heated at 50 to 150 ° C. for 30 minutes.
Allow to react for minutes to 6 hours. A lubricant and other additives are added to this solution to obtain a paint. The paint is applied by a known method such as a roll coater or a bar coater, and dried at 150 to 300 ° C.

(Embodiment) The embodiment will be specifically described below. After electrolytic degreasing and electrolytic pickling of a cold-rolled steel plate (SPCC) having a thickness of 0.8 mm, both surfaces were subjected to galvannealing (10% by weight of Fe in the plating) (the adhesion amount was 45 g / m ^{2 on} both surfaces). ). A chromate treatment solution was applied to both sides of the plated steel sheet and dried to obtain a chromate layer (the amount of adhesion was 40 mg / m ^{2 on} both sides in terms of metallic chromium). The coating was roll-coated on both sides and baked. As a comparative material, a resin paint described in JP-B-3-25349 was also applied and baked. The method for preparing the paint and the method for evaluating the film properties are shown below. Tables 1 and 2 show the composition of the resin layer and the evaluation results.

(Preparation method of various paints) (1) Preparation method of amine-modified epoxy resin solution (1) and lubricating resin paint containing metal powder To 2000 g of bisphenol A epoxy resin (epoxy equivalent = 2000), 1000 g of toluene was added. After the replacement with nitrogen, the temperature was raised to 80 ° C. to obtain a uniform solution. Next, 52.5 g of diethanolamine was added dropwise to this solution over 30 minutes, and the mixture was reacted for 1 hour to obtain an amine-modified epoxy solution (1).
I got (Weight average molecular weight of amine-modified epoxy resin 1
3000, amine addition amount 0.5 mol) Metal powder, lubricant, silica, organic bentonite (Benton 34, precipitation inhibitor), cyclohexane ( (For dilution adjustment) was added to prepare a metal powder lubricating resin paint.

(2) Amine-modified epoxy resin solution (2)
And a method for preparing a metal powder-containing lubricating resin coating material 680 g of propylene glycol monomethyl ether acetate was added to and dissolved in 1,000 g of a bisphenol A type epoxy resin (epoxy equivalent = 3000). Then, 25 g of bisphenol F and 1 g of lithium chloride were added, and
The mixture was reacted at 0 ° C. for 1 hour to obtain a homogeneous solution. This solution 1167
7.5 g of N-methylethanolamine was added dropwise to the resulting mixture over 2 hours, and the mixture was further reacted at 70 ° C. for 3 hours to obtain an amine-modified epoxy resin solution (2). (Weight average molecular weight of the amine-modified epoxy resin: 20,000, amine addition: 0.6
Mol) The thus obtained amine-modified epoxy resin solution was mixed with a metal powder, a lubricant, silica, an organic bentonite (Benton 34, an antisedimentation agent) and cyclohexane (for dilution adjustment) shown in Table 1 to be described later. A powder lubricating resin coating was prepared.

(3) Preparation of Lubricant Organic Resin Coating (1) Various silicas shown in Table 1 were added to 200 g of a 30% solids cellosolve solution of polyvinyl butyral resin (average degree of polymerization = 300). Then, 30 g of an orthophosphoric acid aqueous solution was gradually added dropwise, and then the mixture was heated to 90 ° C.
The reaction was performed under reflux for 4 hours. Next, various lubricants shown in Table 1 were added to prepare a lubricating organic resin paint (1).

(4) Preparation of paint of comparative example In the same manner as in the above (1) to (3), but using a resin of the type shown in Table 1 in an amount shown in Table 1. For Comparative Example 9, the following paint was used.

(Comparative Example 9) As the outermost organic resin film, one having the following composition was used for the inner surface (12 μm) and the outer surface (12 μm).
μm). The organic resin film is composed of 45% by weight of Al powder (flake, 3 μm in thickness), a rubber-modified epoxy resin and a phenoxy resin (30% by weight, 7% by weight, respectively).
0% by weight) and 1% by weight of a nonionic fluorinated surfactant. Here, the rubber-modified epoxy resin is a butadiene acrylonitrile copolymer rubber 2
It is a mixture of 5% by weight and 75% by weight of a novolak type epoxy resin.

(Evaluation Method of Film Properties) The press-workability, resistance weldability, outer surface corrosion resistance, and inner surface corrosion resistance of the prototype coated steel sheet were evaluated.

(1) Method of evaluating press formability (a) Evaluation of lubricity by cylindrical molding test Press conditions: 1 g / m ^{2 of} rust preventive oil Z5 manufactured by Idemitsu Oil Co., Ltd.
Oiling and evaluation ・ Punch diameter and shape ・ ・ ・ 33mmφ flat bottom cylinder ・ Clearance ・ ・ ・ 1mm ・ Planck size ・ ・ ・ variable changes ・ Wrinkle holding load ・ ・ ・ 2t ・ Drawing speed ・ ・ ・ 60mm / sec Under the above conditions By setting the outer surface of the steel sheet to the die side and the inner surface to the punch side, forming a cylinder, and determining the limiting drawing ratio of each sample (the maximum value among the die diameter / punch diameter of the sample that has been drawn out), The lubricity was evaluated using this value. A larger value indicates better press workability. (B) Evaluation of powdering resistance of the film by a cylindrical molding test Press condition: 1 g / m ^{2 of} rust preventive oil Z5 manufactured by Idemitsu Oil Co., Ltd.
・ Punch diameter and shape ・ ・ ・ 33mmφ flat bottom cylinder ・ Clearance ・ ・ ・ 1mm ・ Planck size ・ ・ ・ 66mm ・ Wrinkle holding load ・ ・ ・ 4t ・ Drawing speed ・ ・ ・ 60mm / sec Outer side of steel plate Was set on the die side and the inner side was set on the punch side, and the degree of powdering of the coating on the inner side after cup molding was visually observed and evaluated. The evaluation criteria were as follows: ◎ indicates the level without powdering in the peeling test with cellophane tape, ○ indicates the level with slight powdering in peeling with cellophane tape, but not visually observable, △ indicates the level with slight powdering, and indicates the very amount of powdering. Was evaluated as x when there was a large amount.

(2) Resistance weldability evaluation method Seam welding conditions: Electrode: chrome-copper alloy, trapezoidal electrode (tip R: 15
mmφ) ・ Welding method ・ ・ ・ Double head, lap seam welding ・ Pressure ・ ・ ・ 400kg ・ Electrification time ・ ・ ・ 2 cycles on, 1 cycle off
(2/50 second energization, 1/50 second non-energization) ・ Cooling ・ ・ ・ Internal and external water cooling ・ Welding speed ・ ・ ・ 2.5m / min ・ Welding current ・ ・ ・ Various changes Welding was performed to determine the range of an appropriate welding current (kA) from the presence or absence of breakage of the base material and the degree of nugget wrap in a T-peel tensile test, and seam weldability was evaluated.

(3) Evaluation method of outer surface corrosion resistance A top coat paint Emaron manufactured by Dainippon Paint Co., Ltd. was applied to the outer surface so as to have a dry film thickness of 10 μm, and was then dried in a furnace at 120 ° C. for 20 minutes.
After baking for minutes, JASO (salt spray 2 hours, 60 hours)
℃, 20-30RH% drying 4 hours ・ 50 ℃, 98RH%
2 hours) 300 cycles for the flat part and 1 for the others
It was subjected to a CCT test of 00 cycles, and evaluated by the residual plate amount (mm) of the flat portion, the cross cut portion of the flat portion, and the side wall portion of the pressed product formed under the conditions (1) and (b). The thickness before the test was 1.0 mm.

(4) Evaluation Method for Inner Surface Corrosion Resistance The flat surface and the inner surface of a flat-bottomed cylindrical cup molded under the conditions of 1 (b) were evaluated. 20 mm x 1 when evaluating a flat part
Prepare a test piece of 00mm and use unleaded gasoline / 500pp
The test piece was immersed in a fuel of an aqueous solution of formic acid = 1/1 (weight) by 80 mm and subjected to a one month immersion test at room temperature.
The degree of rusting was evaluated in terms of area ratio (%). When evaluating the inner surface of the flat-bottomed cylindrical cup, it was molded into a test piece having a diameter of 33 mm and a height of 30 mm. The above-mentioned fuel was charged at 80% of the inner volume of the cup, immersed for one month at room temperature, and then the inner surface of the cup was released. The degree of rust was evaluated in terms of area ratio (%). Since the fuel is separated from the formic acid aqueous solution in the lower layer and the unleaded gasoline in the upper layer from the order of the specific gravity, the rust generation area ratio at each site was evaluated.

[0051]

[Table 1]

[0052]

[Table 2]

HCA: average major axis 13 μm, average minor axis 5 μm
m, scaly Ni powder having an average thickness of 1 μm (HCA-1 manufactured by Novamet) HCA ^* : HCA surface-treated with γ-glycidoxypropyltrimethoxysilane F95: average major axis 20 μm, average minor axis 7 μm, average 1 μm thick flaky Ni powder (Ni-Fla made by Fukuda Metal Foil Powder)
ke95) PE: polyethylene wax average particle size 1 μm, softening point 120 ° C. PTFE: polytetrafluoroethylene wax average particle size 2 μm, softening point 125 ° C. S: organosilica sol average primary particle size 10 nm PE: polyethylene wax average particle size 5 μm, softening Point 120 ° C. S: Colloidal silica (Snowtex O manufactured by Nissan Chemical Industries) Average primary particle size 10 to 20 nm Epoxy ^* : Weight average molecular weight 13,000, epoxy equivalent 2000, no modification of amine compound

[0054]

[0055]

[0056]

The steel sheet of the present invention has a different organic coating composition on the front and back, and has a resin layer containing an amine-modified epoxy resin, a lubricant, a Ni powder of a specific shape, and silica as required on one surface. The other surface has at least one functional group selected from a hydroxyl group, an isocyanate group, a carboxyl group, a glycidyl group and an amino group.
By using a resin layer containing various kinds of resins, silica and a lubricant as main components, it has excellent inner surface corrosion resistance, outer surface corrosion resistance, press workability, and resistance weldability. Therefore, the steel sheet of the present invention is particularly useful as a steel sheet for alcohol and alcohol-mixed gasoline tanks.

[Brief description of the drawings]

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

[Explanation of symbols]

 Reference Signs List 1 steel plate 2 metal plating layer 3 chromate layer 4 metal powder-containing lubricating organic resin layer 5 lubricating organic resin layer

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B05D 7/24 303 B05D 7/24 303B C23C 28/00 C23C 28/00 C (72) Inventor Sachiko Suzuki 1 Kawasakicho, Chuo-ku, Chiba-shi, Chiba Address: Kawasaki Steel Engineering Co., Ltd. (72) Kazuo Mochizuki Inventor Kazuo Mochizuki 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Co., Ltd.Technical Research Laboratory (72) Inventor: Hiroto Tanabe 8-15 Machi (72) Inventor Osamu Ogawa 690-109 Kamiatsuzaki, Kuroiso City, Tochigi Prefecture

Claims (7)

[Claims] (1) Zn or Z as a lowermost layer on both surfaces of a steel sheet.
It has a metal plating layer containing n as a main component, has a chromate layer on both upper layers, and further contains an amine-modified epoxy resin, a flaky Ni powder, and a lubricant on the upper layer on one side. And at least one functional group having at least one functional group selected from a hydroxyl group, an isocyanate group, a carboxyl group, a glycidyl group and an amino group in the upper layer on the other surface. A highly corrosion-resistant steel plate for a fuel tank, comprising a lubricating organic resin layer containing a resin, a lubricant, and silica as main components. 2. The method according to claim 1, wherein the metal powder-containing lubricating organic resin layer is in the form of scaly N based on 100 parts by weight of the amine-modified epoxy resin.
The highly corrosion-resistant steel plate for a fuel tank according to claim 1, wherein the i-powder is 20 to 400 parts by weight and the lubricant is 0.1 to 5 parts by weight. 3. A steel sheet having Zn or Z as a lowermost layer on both surfaces of a steel sheet.
It has a metal plating layer containing n as a main component, has a chromate layer on both upper layers, and further has an amine-modified epoxy resin on one surface thereof, a flaky Ni powder, a lubricant, and silica. At least one functional group selected from a hydroxyl group, an isocyanate group, a carboxyl group, a glycidyl group and an amino group in the upper layer of the other surface. A steel plate for a high corrosion resistant fuel tank, comprising a lubricating organic resin layer containing one kind of resin, a lubricant, and silica as main components. 4. The method according to claim 1, wherein said metal powder-containing lubricating organic resin layer is in the form of scaly N based on 100 parts by weight of the amine-modified epoxy resin.
The steel plate for a highly corrosion-resistant fuel tank according to claim 3, wherein i-powder is 20 to 400 parts by weight, lubricant is 0.1 to 5 parts by weight, and silica is 40 parts by weight or less. 5. The amine-modified epoxy resin is a composite resin obtained by adding 0.3 to 1.0 mol of an amine compound to 1 equivalent of an epoxy group, and has a weight average molecular weight of 5,000 to 50,000. The scale-like Ni powder has an average major axis of 8 to 25 μm, an average minor axis of 1 to 12 μm, and an average thickness of 0.5 to 5.0 μm, and the lubricant is a polyolefin wax and / or polytetrafluoroethylene. With an average particle size of 1 to 10 μm
m and a softening point of 70 to 150 ° C.
The steel plate for a highly corrosion-resistant fuel tank according to any one of the above. 6. The method according to claim 1, wherein the lubricating organic resin layer is formed of the resin 100.
The high corrosion resistant fuel tank steel plate according to any one of claims 1 to 5, wherein the lubricant is 1 to 40 parts by weight and the silica is 5 to 80 parts by weight based on parts by weight. 7. The lubricant in the lubricating organic resin layer is a polyolefin wax and / or polytetrafluoroethylene, wherein the lubricant has a softening point of 70 to 150 ° C. and an average particle size of 1 to 7 μm. The glass transition temperature (Tg) of the lubricating organic resin layer is from 0 to 9;
The steel plate for a highly corrosion-resistant fuel tank according to any one of claims 1 to 6, wherein the temperature is 0 ° C.