JP2005335371A - Surface treated steel sheet for fuel container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treated steel sheet not containing lead and hexavalent chromium and improved in resistance to deteriorated gasoline, weldability and press working property and suitable for a fuel container such as a gasoline tank of a car or the like. <P>SOLUTION: A silicon-based coating film with an Si deposition of 10-300 mg/m<SP>2</SP>is formed as a first layer on both side faces of a zinc plated steel sheet. An epoxy resin layer of a film thickness of 0.6-2.0 μm containing 5-60 pts. mass of a metal powder selected from a Ni powder and a ferrosilicon powder with an average particle diameter of 0.1-6.0 μm to 100 pts. mass of a resin is formed on the above coating film on the inner surface of the container. This second layer may further contain one of or both silica and wax. On the outer surface of the container, a layer with a film thickness of 0.3-2.0 μm containing 1-40 pts. mass of the wax and 5-80 pts. mass of silica in 100 pts. mass of an epoxy type resin having a functional group selected from hydroxyl, isocyanate, carboxyl, glycidyl and amino group is formed on the first layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface-treated steel sheet made of a zinc-based plated steel sheet, which is particularly suitable for a fuel container such as an automobile fuel tank that uses gasoline as fuel. The surface-treated steel sheet of the present invention does not contain lead and hexavalent chromium, and has a high corrosion resistance (hereinafter referred to as “gasohol”), which is a problem on the inner surface side of the fuel tank, and deteriorated gasoline or alcohol-containing gasoline fuel containing organic acids. It is a collective term for “degradation gasoline resistance” including corrosion resistance against alcohol-containing gasoline fuel, and is excellent in resistance weldability and press formability.

  The fuel tank material for ordinary gasoline-powered automobiles and motorcycles (hereinafter referred to as automobiles) has corrosion resistance on the inner and outer surfaces, especially in the fuel environment on the inner surface of the container, press formability, and weldability. Required.

  As a material for gasoline fuel containers, a Pb-10 to 25% Sn alloy-plated steel sheet, conventionally called a turn sheet, has been widely used. However, due to recent environmental regulations, it becomes difficult to use a turnsheet containing Pb, and the development of a surface-treated steel sheet for a fuel container that replaces this is desired. Further, with respect to the corrosion resistance to fuel, a higher level is required, such as performance in a deteriorated gasoline environment containing an organic acid generated by oxidation of gasoline components.

  In response to this requirement, Al-plated steel plates, Sn—Zn-plated steel plates and the like have been developed as alternatives. Among these, the Al-plated steel sheet has a problem in joining properties such as welding and soldering. In this respect, Sn-approx. 8% Zn alloy-plated steel sheet is said to have a good balance of performance, but since the application of plating itself is almost limited to fuel containers, the market scale is small, stable supply and price There is a problem. Therefore, it is economically advantageous if a relatively inexpensive zinc-based plating (“zinc-based plating” means zinc plating and zinc alloy plating) steel plate, which is widely used in general, can be applied to a fuel container. is there.

  Japanese Unexamined Patent Publication No. 10-137681 (Patent Document 1) is a technique for applying a Zn-based plated steel sheet to an automobile fuel container. In this publication, a chromate-treated galvanized steel sheet is coated with an amine-modified epoxy resin layer containing Ni and Al metal powder on the inner surface side, and a silica-containing resin layer containing wax on the outer surface side. Coated surface-treated steel sheets have been proposed.

  The surface-treated steel sheet described in Patent Document 1 forms a different resin layer on the inner surface and the outer surface after the chromate treatment of a zinc-based plated steel sheet. However, recently, due to environmental problems, there is a growing demand for materials that do not use the chromate treatment containing harmful hexavalent chromium, as well as non-chromium materials that do not contain chromium at all, in addition to the aforementioned Pb. Yes.

In Japanese Patent No. 3328578 (Patent Document 2), a zinc-plated steel sheet is subjected to a chemical conversion treatment such as chromate, zinc phosphate or iron phosphate on one side corresponding to the inner surface of the fuel container, and Ni powder and Al powder are further added. A surface-treated steel sheet coated with an amine-modified epoxy resin layer is proposed. In JP 2000-129461 A (Patent Document 3), a first layer containing a resin and a silica source as a main film forming component is formed on one side of a zinc-based plated steel sheet, and Ni is formed thereon as a second layer. A surface-treated steel sheet having a resin layer containing metal powder containing Al has been proposed.
Japanese Patent Application Laid-Open No. 10-137681 Japanese Patent No. 3328578 JP 2000-1294611 A

  However, in the above-described conventional technology, since the thickness of the resin layer containing the metal powder is as large as 2 to 10 μm, it is difficult to obtain stable weldability in practical use, which is insufficient for use in the manufacture of the fuel container. It was a thing.

  In addition, since the outer surface side of the fuel tank is usually painted after press forming, even if the resin layer of the surface-treated steel sheet is damaged during press forming, corrosion resistance is rarely a problem. On the other hand, since it is normal that the inner surface side is not coated after press molding, it is desired that corrosion resistance in a deteriorated gasoline environment is secured even if the resin layer is damaged by press molding. In the case of a conventional non-chromium material, particularly when the chemical conversion treatment is zinc phosphate or iron phosphate, the corrosion resistance to organic acids is insufficient, and the deterioration gasoline resistance after press molding is remarkably lowered. Further, it is desirable that both the inner and outer surfaces have good press formability and therefore good lubricity so that damage to the resin layer during press forming is minimized.

  The object of the present invention is to use a zinc-based plated steel sheet as a base material, without using lead and hexavalent chromium which are environmentally problematic, and to be excellent in corrosion resistance in a gasoline environment, particularly in deterioration gasoline resistance and in weldability. An object of the present invention is to provide a surface-treated steel sheet for a fuel container such as an automobile gasoline container, which is excellent and further excellent in press formability.

  According to the present invention, the plating surface of the zinc-based plated steel sheet is subjected to a base treatment that does not contain hexavalent chromium, and on one side, the upper layer contains Ni metal powder and / or ferrosilicon powder having a specific particle size. Forming a resin layer with a film thickness in the range, preferably on the other side, by forming a resin layer with excellent lubricity, the surface is compatible with deterioration gasoline resistance and weldability and has excellent press moldability A treated steel sheet is obtained.

In one aspect, the present invention includes a first layer made of a silicon-based coating containing no hexavalent chromium on a plated surface of at least one surface of a zinc-based plated steel sheet, and a second layer thereon. The amount of Si is 10 to 300 mg / m ² as the amount of Si, and the second layer is formed of 100 parts by mass of a binder made of a thermosetting organic resin, Ni powder having an average particle size of 0.1 to 6.0 μm and ferro A surface treatment for a fuel container, characterized in that it is a metal powder-containing resin layer having a film thickness of 0.6 μm or more and less than 2.0 μm, containing metal powder selected from silicon powder in an amount of 1 to 60 parts by mass. It is a steel plate.

In another aspect, the present invention comprises, on the plated surfaces on both sides of a zinc-based plated steel sheet, a silicon film not containing hexavalent chromium as a first layer, and a second layer thereon, the first layer comprising: The adhesion amount is 10 to 300 mg / m ² as the Si amount, and the second layer has an average particle diameter of 0.1 to 6 in 100 parts by mass of a thermosetting resin on one surface of the steel plate. A metal powder-containing resin layer having a film thickness of 0.6 μm or more and less than 2.0 μm, containing metal powder selected from Ni powder and ferrosilicon powder of 0.0 μm in an amount of 1 to 60 parts by mass, opposite to a steel plate On the side surface, 1 to 40 parts by mass of a wax in 100 parts by mass of a binder made of at least one organic 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. And silica, titania At least one selected from zirconia and containing a 5-80 parts by weight, characterized in that it is a layer having a thickness of 0.3 to 2.0 .mu.m, a surface treated steel sheet for fuel containers.

  The silicon coating of the first layer is composed of one or more silica sources (silica or a precursor thereof) selected from aqueous silica, gas phase silica, alkali metal silicate, alkoxysilane, and alkyl silicate ester. ) Is preferably formed by applying and drying a treatment liquid containing as a main component.

  The metal powder-containing resin layer is (1) 5 to 40 parts by mass of at least one selected from silica, titania and zirconia, (2) 5 to 20 parts by mass of wax, and 100 parts by mass of the binder. 3) It may further contain one or more components selected from 1 to 30 parts by mass of metal Al powder. The thermosetting resin that is the binder of the metal powder-containing resin layer is preferably an epoxy resin.

  In the present invention, the mass of the binder is the mass as a solid content of the resin component used as the binder, and in the case where the resin component used as the binder is a type that is thermally cured with a crosslinking agent, the total amount of the resin and the crosslinking agent It is.

  According to the present invention, various performances required for a fuel container for automobile gasoline, in particular, deterioration gasoline resistance, press, using zinc-plated steel sheet as a base material and containing no harmful lead or hexavalent chromium at all. An inexpensive surface-treated steel sheet excellent in formability and weldability can be provided.

[Base material plated steel sheet]
The base material of the surface-treated steel sheet of the present invention is a zinc-based plated steel sheet, that is, a galvanized steel sheet or a zinc alloy-plated steel sheet, and preferably a double-sided plated steel sheet.

  The plated steel sheet may be a general cold-rolled steel sheet that is usually used. However, since it is generally subjected to severe forming processing in fuel container applications, it is a steel sheet with excellent press formability, such as ultra low carbon steel and a component system to which one or more of Ti, Nb, and B are added. Preferably there is.

  The plating applied to the steel sheet is zinc or zinc alloy plating widely used for the purpose of ensuring corrosion resistance. The plating type is not limited to these, but, for example, Zn, Zn-Al, Zn-Al-Si, Zn-Ni, Zn-Fe, Zn-Cr, Zn-Mg, Zn-Sn, Zn -Co etc. are mentioned. Preferred is Zn—Ni alloy plating, which has the best balance between performance and economy. The Ni content of the Zn—Ni alloy plating is preferably in the range of 11 to 14% by mass.

The plating method may be any of a hot dipping method, an electroplating method, a vapor deposition plating method, and the like. The plating layer may contain a small amount of an organic compound such as an organic inhibitor, dextrin, or dextran. The plating adhesion amount is preferably 10 g / m ² or more per side from the viewpoint of corrosion resistance. However, if the adhesion amount is too large, there will be problems in terms of cost, workability, and weldability. A more preferable adhesion amount is 15 to 50 g / m ² per side.

  The surface-treated steel sheet according to the present invention is formed by sequentially forming a coating of a first layer and a second layer, which will be described below, on at least one surface (that is, on the plating layer) of a zinc-based plated steel sheet as a base material. . This two-layer coating is usually formed only on one side which becomes the inner surface of the fuel container, and another surface treatment is applied to the opposite side.

[First layer]
The first layer formed on the zinc-based plating layer is a silicon film that does not contain hexavalent chromium. For the silicon film, a treatment solution containing a silica source (colloidal silica or its precursor) is used, and the treatment solution is applied to the surface of the base plated steel sheet and then dried (or baked) according to a conventional method. Can be formed.

  The silica source is selected from aqueous silica (also called silica sol, colloidal silica, etc.), gas phase silica (also called fumed silica, dry silica, etc.), alkali metal silicate, alkoxysilane, and alkyl silicate ester 1 Species or two or more can be used.

  Alkoxysilane is an n (n = 2 to 3) hydrolyzable group (typically an alkoxy group, particularly a methoxy group or an ethoxy group) per silicon atom and (n-1) non-hydrocarbon groups. It is a compound in which a hydrolyzable organic group (for example, a lower alkyl group such as ethyl or propyl, a lower alkyl group containing a functional substituent such as amino or epoxy, a vinyl group, or the like) is bonded. Preferred as the alkoxysilane used in the first layer in the present invention is one in which the non-hydrolyzable organic group is an alkyl group, for example, ethyltrimethoxysilane, propyltrimethoxysilane, ethyltriethoxysilane, etc. Alkoxysilanes generally called silane coupling agents in which the non-hydrolyzable organic group is an alkyl having a functional group or a vinyl group can also be used.

Silicic acid alkyl ester is tetraalkoxysilane (= alkyl silicate), and specific examples thereof include ethyl silicate.
The alkoxysilane undergoes hydrolysis and polycondensation in the treatment liquid or in coating and drying (baking), and finally becomes a polysiloxane type polymer. Silicic acid alkyl esters similarly undergo hydrolysis and polycondensation and eventually become siliceous components. Therefore, any silica source described above can be applied and dried to form a silicon-containing film as a first layer made of silica or having a polysiloxane structure in which some organic components remain. Is done.

If the adhesion amount of the first layer is too small, it is inferior in the resistance to deterioration gasoline, and if it is too much, the weldability is inferior. The proper adhesion amount, as the adhesion amount of Si contained in the first layer, 10 mg / m ² or more, a degree 300 mg / m ² or less, more preferably in the range of 20 to 100 mg / m ^2.

  The first layer may contain a slight amount of a resin, a phosphoric acid compound and the like in addition to the silicon compound. The resin is preferably a thermoplastic resin having one or more of hydroxyl group, carboxyl group, amino group, glycidyl group, isocyanate group and the like from the viewpoint of adhesion to the second layer. Examples include urethane, acrylic, polyester, epoxy, melamine resin, and alkyd resin. By adding such a resin, the corrosion resistance is improved. Moreover, as a phosphoric acid compound, phosphoric acid, phosphorous acid, hypophosphorous acid, and these alkali metal salts are mentioned, Corrosion resistance improves by the addition. When components other than these silicon compounds are contained in the first layer, the amount thereof is 20 parts by mass or less in total with respect to 100 parts by mass of the silica source (amount as silica) in the resin liquid used for film formation. It is preferable.

[Second layer]
The surface-treated steel sheet according to the present invention includes a resin layer containing metal powder as the second layer that is the uppermost layer on the first layer. The second layer (metal powder-containing resin layer) is obtained by using a thermosetting resin as a binder resin component and containing one or both of Ni powder and ferrosilicon powder having a predetermined particle size. Since this metal powder-containing resin layer is particularly excellent in resistance to deterioration gasoline, it is preferably formed on the inner surface side of the fuel container. Below, this metal powder containing resin layer may be called the 2nd layer of the inner surface side for convenience.

  The binder resin component preferably exhibits an effect as a barrier against a corrosive environment in addition to the role as a binder. For that purpose, it is better that the resin itself as the binder component does not easily dissolve or swell in a gasoline environment. For this purpose, a thermosetting resin is more suitable than a thermoplastic resin. Examples of the thermosetting resin include an epoxy resin, an acrylic resin, a urethane resin, a polyester resin, and a phenol resin. In the present invention, an epoxy resin is preferable. The epoxy resin may be a modified epoxy resin modified with a functional group such as an amino group. The binder resin component may contain not only the thermosetting resin but also a cross-linking agent as a base. Examples of the crosslinking agent include phenol resin, melamine resin, benzoguanamine resin and the like. The thermosetting resin is crosslinked and cured during baking of the film to form a dense resin film.

  By including one or two metal powders selected from Ni powder and ferrosilicon powder in the second layer on the inner surface side, the deterioration gasoline resistance and weldability of the surface-treated steel sheet are improved. This is considered to be because there is an effect of neutralizing the organic acid contained in the deteriorated gasoline, and because a suitable energization site is formed for welding. In particular, Ni powder is excellent in corrosion resistance to alcohols such as methanol and organic acids that are oxides thereof, and has high specific resistance, so that it is effective in improving weldability and is most suitable as an additive metal powder. The shape of the Ni powder may be scaly, but spherical particles are preferred. Ni powders and ferrosilicon powders having an average particle diameter of 0.1 to 6.0 μm are preferably used. If the particle size is too small, the weldability is poor. On the other hand, if it is too large, the resin layer tends to be porous and deteriorate in resistance to deterioration gasoline, and the metal powder itself tends to settle during coating, making it difficult to produce a uniform product. A more preferable average particle diameter is 0.6 to 3.0 μm. In addition, this spherical particle can take the form of the aggregate | assembly with which multiple pieces were connected in a linear form. In that case, the average minor axis of the aggregate falls within the above range.

  The blending amount of the metal powder selected from the Ni powder and the ferrosilicon powder is in the range of 1 to 60 parts by mass in total with respect to 100 parts by mass of the binder (which is resin + crosslinking agent as described above). When the amount of the metal powder is less than 5 parts by mass, the weldability and corrosion resistance are inferior. When the amount exceeds 60 parts by mass, the coating becomes porous and has resistance to deterioration gasoline. Is likely to occur. In addition, since the fluidity of the processing liquid is also reduced, it is very difficult to apply uniformly. A more preferable range is 10 to 40 parts by mass.

  The second layer on the inner surface side may further contain metal Al powder in addition to the Ni powder and / or ferrosilicon powder. Al powder is added mainly for the purpose of improving the corrosion resistance of deteriorated gasoline. As described in Patent Document 1, it is considered that the Al powder is more preferably a scaly shape having a major axis of about 10 to 20 μm because a physical shielding effect against gasoline permeation can be expected. When adding metal Al powder, the quantity shall be the range of 1-30 mass parts with respect to 100 mass parts of binders. When there is too much content of metal Al powder, a coating film will become porous and deterioration gasoline resistance will deteriorate.

  If necessary, the second layer on the inner surface side may be one or more selected from silica, titania, and zirconia, and one or two of lubricant wax, coloring pigment, rust preventive pigment, conductive pigment, and the like. It may further contain seeds or more.

  Among these, since silica, titania, and a zirconia component are effective in improving corrosion resistance, it is preferable that 1 to 40 parts by mass in total is contained in the first layer with respect to 100 parts by mass of the binder. More preferably, it is 5-20 mass parts with respect to 100 mass parts of binders. These components include the above-described silica source (aqueous silica, vapor phase silica, alkoxysilane, alkyl silicate ester, etc.) or titanate coupling agent that is a titania source, It can introduce | transduce in a 2nd layer by adding the zirconate coupling agent etc. which are / or a zirconia source.

  When the second layer contains wax, press formability is enhanced. When the wax is contained in the second layer for this purpose, the amount is preferably 5 to 20 parts by mass with respect to 100 parts by mass of the binder. As the wax, polyolefin waxes such as polyethylene, polypropylene and polybutene, polytetrafluoroethylene and the like are preferable. One kind of wax may be used, or several kinds of waxes may be mixed and used. The average particle size of the wax is preferably 1 to 5 μm.

  The second layer can be formed by using a treatment liquid prepared by sufficiently suspending the Ni powder and / or ferrosilicon powder in a solution or dispersion of a binder resin component, and applying and drying (baking) this. it can. If necessary, the treatment liquid may contain Al powder, silica, titania, a source of zirconia components, wax, and other additive components as described above. However, a hexavalent chromium compound is not contained. The treatment liquid may be an aqueous treatment liquid in which the solvent is water or a mixed solvent of water and a water-miscible organic solvent, or a solvent-based treatment liquid in which the solvent is an organic solvent.

  If the film thickness of the second layer is too thick, the weldability deteriorates, and if it is too thin, the deterioration gasoline resistance deteriorates. Therefore, the average film thickness is set to 0.6 μm or more and less than 2.0 μm, preferably 0.8. ˜1.8 μm. Depending on the particle size of the metal powder or wax, the metal powder or wax may protrude from the surface of the second layer. In the present invention, the film thickness is expressed as a value neglected in principle for such protruding portions of metal powder and wax.

[Opposite side]
The surface-treated steel sheet of the present invention can be provided with the above-described silicon first layer and the second layer comprising the metal powder-containing resin layer on one or both surfaces of the zinc-based plated steel sheet. When the first layer and the second layer are formed on both sides, at least the second layer on the outer side of the fuel container contains at least one selected from wax and silica, titania and zirconia. It is preferable to improve the corrosion resistance and lubricity on the outer surface side.

  When the first layer and the second layer are formed only on one side, the second layer made of a metal powder-containing resin layer having excellent resistance to deterioration gasoline is preferably formed on the inner surface side of the fuel container. Since the surface opposite to the zinc-plated steel sheet, which is the outer surface of the fuel container, is generally coated, only chemical conversion treatment (for example, formation of the same silicon-based film as the first layer) is performed as a coating base. It's okay. However, it is preferable to further form some coating thereon to enhance the corrosion resistance in a corrosive environment (atmosphere, salt damage environment) different from the inner surface side.

  For example, the opposite surface of the galvanized steel sheet is first subjected to a base chemical conversion treatment (may be the same as the first layer), and then coated with one or more layers having excellent corrosion resistance (formation of a resin layer). be able to. The coating thickness at that time is generally determined to be balanced between corrosion resistance, weldability, and press formability since there is a possibility that the weldability is deteriorated if it is too thick. Moreover, in order to improve weldability, a conductive pigment may be contained in the coating film.

  In a preferred embodiment of the present invention, the opposite surface of the galvanized steel sheet is formed on the plating surface by forming the same first layer as described above, that is, a silicon film not containing hexavalent chromium, and wax. And a second layer made of a specific resin containing silica and having excellent lubricity (hereinafter referred to as the second layer on the outer surface side for convenience).

  It is preferable that the second layer on the outer surface side functions as a lubricating film that imparts slidability during press molding as well as improving paint adhesion. Therefore, it is preferable to use 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 as the organic resin serving as a binder. Thereby, paint adhesion can be improved. Specific examples include epoxy resins, alkyd resins, acrylic resins, urethane resins, polyvinyl butyral resins, phenol resins, melamine resins, and the like. Among these, an epoxy resin is most preferable as a binder from the viewpoints of adhesion and top coating suitability with a post-coating process. The epoxy resin has a hydroxyl group or a glycidyl group, but an amino-modified epoxy resin may be used in order to further introduce an amino group.

  As the wax, polyolefin waxes such as polyethylene, polypropylene and polybutene, polytetrafluoroethylene and the like are preferable. One or more of these waxes can be used. The average particle diameter of the wax is preferably 1 to 5 μm, and the addition amount is preferably 5 to 40 parts by mass with respect to 100 parts by mass of the binder (resin solid content). When the amount is less than 1 part by mass, the lubricity is insufficient and press molding becomes difficult. On the other hand, when it exceeds 40 mass parts, the adhesiveness of a resin layer and the adhesiveness with the coating applied after that will fall.

  At least one selected from silica, titania and zirconia is added to improve corrosion resistance. When silica is added, either silica sol (aqueous silica) or fumed silica (vapor phase silica) may be used. Other silica sources such as alkoxysilanes and alkyl silicates described for the first layer can also be used. The amount of silica added is preferably 5 to 40 parts by mass, more preferably 10 to 30 parts by mass as silica with respect to 100 parts by mass of the binder. When titania or zirconia is added, it can be introduced into the second layer by adding a titanate coupling agent that is a titania source and / or a zirconia coupling agent that is a zirconia source.

  In addition to the resin and the above components, the organic resin paint for forming the second layer on the outer surface side includes additives such as an antifoaming agent and a leveling agent for improving the paintability, and coloring, if necessary. Various pigments such as titanium oxide, petals, carbon black for carrying out, wetting and dispersing agents for improving the dispersion stability of pigments, coupling agents such as silane coupling agents, catalysts for accelerating the curing reaction, A crosslinking agent or the like can also be added by a known technique.

  In addition, the second layer on the outer surface side may further contain metal powder, particularly Ni powder and / or ferrosilicon powder, and further Al powder, as in the second layer on the inner surface side. In this case, the formed resin layer corresponds to the second layer on the inner surface side.

  The film thickness of the second layer coating on the outer surface side is in the range of 0.3 to 2.0 μm. When the film thickness is less than 0.3 μm, the effect of the second layer as the lubricating resin film cannot be sufficiently obtained. When the film thickness exceeds 2.0 μm, the insulating property of the second tank is increased and the weldability is deteriorated.

  It is not always necessary to apply anti-rust oil to the surface of the surface-treated steel sheet according to the present invention or to apply lubricating oil at the time of forming, but it is necessary to prevent rust at storage and lubricity at the time of forming. Is desirable. Fuel containers, such as automobile gasoline containers, are generally manufactured by single or multi-stage press molding including spot drawing and spot welding. At that time, the surface where the second layer is the above-described metal powder-containing resin layer is set to the inner surface side of the container.

In this example, the effect on the performance of the surface-treated steel sheet when the type of the silica source of the first layer and its film thickness were varied was examined.
[How to create an evaluation sample]
Formation of the first layer:
An electro-Zn-13% Ni alloy-plated steel sheet made of cold-rolled steel sheet with a thickness of 0.8 mm and containing Ti, Nb, and B (double-sided plating, plating adhesion amount: 20 g / per side) m ² ) was cut into 200 mm × 300 mm, and then a treatment liquid in which various silica sources shown in Table 1 were dissolved or dispersed was applied to one side thereof and dried at 60 ° C. to form a first layer. . The coating method was a bar coating method, and the number of the bar coating and the concentration of the treatment liquid were adjusted so that a predetermined adhesion amount was obtained. The amount of adhesion was determined by measuring the strength of Si in the first layer using a fluorescent X-ray apparatus.

Formation of the second layer:
A treatment liquid prepared by sufficiently suspending Ni metal powder (average particle diameter 0.6 μm) in a solvent-based resin liquid containing a thermosetting epoxy resin (molecular weight 20000) is formed on the first layer. The film was baked at 220 ° C. after coating by a bar coating method so that the film thickness after baking was 1.0 μm. The mass ratio of the resin to the Ni metal powder was 100: 10.

[Evaluation methods]
Anti-degradation gasoline resistance:
Cup drawing was performed under the following drawing conditions so that the surface of the second layer was the inner surface. The obtained cup imitated deteriorated gasoline, 3 cc of an aqueous solution with a formic acid concentration of 300 ppm and 27 cc of gasoline were sealed and kept at 45 ° C. Evaluation was judged as follows in the state of the corrosion products (liquid turbidity) after 30 days (up to ○ passed).

Drawing conditions: blank diameter = 100 mm, punch diameter = 50 mm, punch shoulder = 5 R, die diameter = 52 mm, die shoulder = 5 R, BH pressure = 10 kN, overhang height = 25 mm
Evaluation criteria ◎ +: No change ◎: Almost no change ○: Obstacles of about 10 to 40% seen from above,
Δ: Dust generation of about 40 to 70% when viewed from above (observation of the bottom surface is quite difficult),
X: Red rust is floating in almost the entire liquid (observation of the bottom and sides is quite difficult).

Weldability (resistance between electrodes):
After stacking the two test materials with the second layer surface inside, spot welding was performed under the conditions of pressure 300 kgf, energization 15 cycles, current 8 kA, and the inter-electrode resistance in the first cycle was measured. Evaluation was made as follows (up to ○ passed).

◎ +: Interelectrode resistance is 150 μΩ or less,
A: Interelectrode resistance is 200 μΩ or less,
○: Interelectrode resistance is 200 μΩ or more, or slight dust is generated,
△: considerably large dust generation,
X: Not energized (not weldable).

As the test results are shown in Table 1, those having a silicon coating of 10 mg / m ² or more as the Si adhesion amount as the first layer had good deterioration gasoline resistance. However, when the thickness of the first layer was more than 300 mg / m ² as the Si adhesion amount, the weldability was poor.

In this example, the influence of the base resin type of the second layer was investigated.
[Formation of the first layer]
An electric Zn-plated steel sheet made of the same cold-rolled steel sheet as in Example 1 (double-sided plating, plating coverage: 30 g / m ² per side) was used as a base material, and was cut in the same manner as in Example 1 and then one side thereof Similarly, the first layer was formed by coating by bar coating and drying at 60 ° C. The silica source used was aqueous silica (average particle size 7 nm), and the adhesion amount was 30 mg / m ² as Si.

[Formation of second layer]
After baking a treatment liquid prepared by sufficiently suspending Ni metal powder (average particle size 0.6 μm) in a solvent-based resin liquid containing several thermosetting resins on the first layer The film was applied by a bar coating method so that the film thickness was 1.0 μm, and then baked at 220 ° C. The mass ratio of the resin to the Ni metal powder was 100: 10.

[Evaluation methods]
Degradation gasoline resistance and weldability were evaluated. The evaluation method is the same as in Example 1. The results are shown in Table 2.

  As can be seen from Table 2, epoxy-based thermosetting resin (molecular weight 20000), acrylic-based thermosetting resin (molecular weight 15000), urethane-based thermosetting resin (molecular weight 20000), polyester-based thermosetting resin (molecular weight 20000). Although any thermosetting resin such as phenol thermosetting resin (molecular weight 20000) could be used, the deterioration-resistant gasoline resistance could be satisfied, and among them, the epoxy resin was particularly excellent.

In this example, the influence of metal powder and other components added to the second layer was examined.
[Formation of the first layer]
The first layer was formed in the same manner as in Example 2. The base material was also the same electric Zn-plated steel sheet.

[Formation of second layer]
Ni powder and / or ferrosilicon powder is added to a solvent-based resin liquid containing a thermosetting epoxy resin (molecular weight 20000), and a part of the powder is further flaky Al powder (major axis 9 μm) and, depending on circumstances. A suspension obtained by adding aqueous silica and sufficiently suspending it was used as a treatment liquid. The treatment liquid thus prepared was applied onto the first layer by a bar coating method so that the film thickness after baking was 1.0 μm, and then baked at 220 ° C. The composition of the treatment liquid is as shown in Table 3.

[Evaluation methods]
Degradation gasoline resistance and weldability were evaluated. The evaluation method for the resistance to deterioration gasoline is the same as that in Example 1. The results are also shown in Table 3.

  As can be seen from Table 3, deterioration gasoline resistance and weldability were improved by adding either one or both of Ni powder and ferrosilicon powder. Moreover, the performance with the addition of Al powder and aqueous silica was also good.

In this example, the influence of the film thickness of the second layer was examined.
[Formation of the first layer]
The first layer was formed in the same manner as in Example 2. The base material was also the same electric Zn-plated steel sheet.

[Formation of second layer]
A second layer was formed in the same manner as in Example 2 except that the film thickness was changed variously. The thermosetting resin used was an epoxy resin. After application, baking was performed at 220 ° C. The composition of the treatment liquid and the film thickness of the inner surface second layer are as shown in the table.

[Evaluation methods]
Degradation gasoline resistance and weldability were evaluated. The evaluation method is the same as in Example 1, but the weldability was also evaluated by the seam weldability test shown below in addition to the measurement of interelectrode resistance similar to Example 1. The test results are summarized in Table 4.

Weldability (Seam Weldability):
Two specimens were stacked so that the resin layer was on the mating surface, and after performing a continuous seam welding test for 400 m under the following conditions, a cross-sectional micro observation of a 400 m welded portion was performed and evaluated according to the following criteria.

Applied pressure: 400 kgf,
Energizing time: 2 cycles,
Rest time: 2 cycles,
Current: 11000A
Speed: 2.7 m / min.

Evaluation criteria:
○: Good welding,
Δ: presence of blowhole,
X: There is an unwelded part.

  As shown in Table 4, when the film thickness of the second layer was 0.6 μm or less, the deterioration gasoline resistance was inferior. On the other hand, when the film thickness was 2.0 μm or more, the weldability deteriorated.

In the present embodiment, a surface-treated steel sheet in which the same first layer of silicon coating and different second layers are formed on both surfaces of the steel sheet is illustrated.
[First layer]
b After using the same electric Zn-13% Ni alloy-plated steel sheet as described in Example 1 and cutting it to 200 mm × 300 mm, a treatment liquid containing aqueous silica (average particle diameter 7 nm) was applied to both sides. By drying at 100 ° C., a silicon coating of the first layer was formed. The coating method was a bar coating method, and the count of the bar coating and the concentration of the treatment liquid were adjusted so that a predetermined adhesion amount was obtained. The amount of adhesion was determined by measuring the Si intensity with a fluorescent X-ray apparatus. On the first layer, second resin layers different from each other on the inner surface side and the outer surface side were formed as described below.

[Second layer on the inner side]
A resin liquid containing an epoxy resin (molecular weight 10,000) is selected from wax (average particle size 1 μm) silica (average particle size 7 nm), Ni powder (average particle size 0.6 μm), and ferrosilicon powder (average particle size 3 μm). The second layer is formed by adding various amounts of the obtained components, TiO ₂ (average particle size 0.3 μm) as a film thickness measurement component, and blocked isocyanate as a cross-linking agent, and suspending them sufficiently. A treatment solution was prepared. This treatment solution was applied onto the first layer on one side of the steel plate by a bar coating method so that the film thickness after baking was 1.4 μm, and then baked at 220 ° C. The film thickness was determined by measuring the intensity of Ti with fluorescent X-rays.

[Second layer on the outer surface]
A coating solution containing a urethane-modified epoxy resin as a main component and a blocked isocyanate as a crosslinking agent is applied with a bar coater to a film thickness of 0.6 μm, and heated for 60 seconds so that the plate temperature is 220 ° C. The membrane was dried and the resin was crosslinked to form a second resin layer.

  In addition to the resin and the crosslinking agent, polyethylene wax and colloidal silica were added in various amounts to the coating solution used, and the mixture was sufficiently stirred and dispersed before use. The film thickness was determined by measuring the Si intensity with fluorescent X-rays.

  The surface-treated steel sheets having different coating structures on the inner surface side and the outer surface side thus prepared were examined for deterioration gasoline resistance and weldability by the same method and evaluation criteria as in Example 1. Moreover, the adhesiveness of the resin layer (2nd layer) after a shaping | molding, a moldability, and the corrosion resistance after the coating of the outer surface side were investigated in the following way.

[Adhesion of resin layer after molding]
Cup molding is performed so that the evaluation surface becomes the outer surface under the same conditions as the deterioration gasoline resistance test. Adhesive tape is applied to the inner and outer surfaces of the processed part, then the tape is peeled off, and the pigment adheres to the tape. Whether or not it was visually observed was evaluated as follows (up to ○ passed).

(Double-circle): Peeling is not recognized,
○: Slight peeling is observed,
X: Peeling is clearly observed.

[Formability]
A Bowden test was conducted under the conditions of no oil coating and a load of 1 kgf, and the following evaluation was made based on the initial dynamic friction coefficient (up to ○ passed):
○: Initial dynamic friction coefficient is 0.20 or less.

X: Initial dynamic friction coefficient is 0.20 or more.
[Corrosion resistance after painting on the outer surface]
On the resin layer (second layer) on the outer surface side, an alkyd melamine resin-based paint (manufactured by Nippon Paint, solvent type) was bar-coated so that the dry film thickness was 15 μm, and baked at 120 ° C. After that, a cross-cut was made with a commercially available cutter, a salt spray (SST) test was performed, the rust expansion width was measured, and the following evaluation was performed (up to ○ passed).
A: Rust width 2.5 mm or less,
○: Rust width 3.0 mm or less,
X: Rust width of 3.0 mm or more.

(Test A)
In this test, the relationship between the adhesion amount of the silicon coating of the first layer and various performances is shown. The test results are shown in Table 5.

The second layer resin layer on the inner surface side had a thickness of 1.4 μm and contained 10 parts by mass of wax, 15 parts by mass of silica, and 10 parts by mass of Ni powder with respect to 100 parts by mass of the binder.
The second resin layer on the outer surface side had a thickness of 0.6 μm and contained 10 parts by mass of wax and 15 parts by mass of silica with respect to 100 parts by mass of the binder.

Adhesion amount of from Table 5 of the first layer Si is preferably in the range of 10-300 mg / m ^2, more preferably in the range was 20 to 100 mg / m ^2.

(Test B)
This test shows the relationship between the content of silica, wax, and metal powder in the second resin layer on the inner surface side and various performances. The film thickness and composition of the second resin layer on the outer surface side were the same as in Test A. The test results are shown in Table 6.

  As shown in Table 6, the moldability is improved by adding wax to the second resin layer on the inner surface side, and the inner surface corrosion resistance and weldability are improved by adding Ni powder. By doing so, the weldability was improved.

(Test C)
This test shows the relationship between the amount of each component added on the outer surface side and various performances. The film thickness and composition of the second resin layer on the inner surface side were the same as in Test A. The test results are shown in Table 7.

  As shown in Table 7, the corrosion resistance is improved by adding silica to the second resin layer on the outer surface side, but the addition amount is most preferably 10 to 30 parts by mass per 100 parts by mass of the binder.

Claims (7)

At least one surface of the zinc-based plated steel sheet is provided with a first layer made of a silicon coating containing no hexavalent chromium and a second layer thereon, and the amount of adhesion of the first layer is 10 as the amount of Si. a to 300 mg / m ^2, the second layer, the binder in 100 parts by weight of a thermally curable organic resin, selected from Ni powder and ferrosilicon powder having an average particle diameter 0.1~6.0μm metal A surface-treated steel sheet for a fuel container, which is a metal powder-containing resin layer having a film thickness of 0.6 μm or more and less than 2.0 μm, containing powder in an amount of 1 to 60 parts by mass. The plating surface of both surfaces of a zinc-based plated steel sheet is provided with a silicon film not containing hexavalent chromium as a first layer and a second layer thereon, and the amount of adhesion of the first layer is 10 to 300 mg as the amount of Si. / M ² , and the second layer is composed of Ni powder and ferrosilicon powder having an average particle diameter of 0.1 to 6.0 μm in 100 parts by mass of a thermosetting resin on one surface of the steel plate. A metal powder-containing resin layer having a film thickness of 0.6 μm or more and less than 2.0 μm, containing the selected metal powder in an amount of 1 to 60 parts by mass. On the opposite surface of the steel sheet, a hydroxyl group, an isocyanate group, It was selected from 1 to 40 parts by weight of wax and silica, titania and zirconia in 100 parts by weight of a binder composed of at least one organic resin having at least one functional group selected from a carboxyl group, a glycidyl group and an amino group. Small Containing a Kutomo one 5-80 parts by weight, characterized in that it is a layer having a thickness of 0.3 to 2.0 .mu.m, a fuel container for surface treated steel sheet.   The treatment in which the silicon-based film of the first layer is mainly composed of one or more silica sources selected from aqueous silica, vapor phase silica, alkali metal silicate, alkoxysilane, and alkyl silicate ester. The surface-treated steel sheet for a fuel container according to claim 1 or 2, which is formed by applying and drying a liquid.   The metal powder-containing resin layer further contains at least one selected from silica, titania and zirconia in an amount of 5 to 40 parts by mass with respect to 100 parts by mass of the binder. Surface-treated steel sheet for fuel containers.   The surface-treated steel sheet for a fuel container according to any one of claims 1 to 4, wherein the metal powder-containing resin layer further contains 5 to 20 parts by mass of wax with respect to 100 parts by mass of the binder.   The surface-treated steel sheet for a fuel container according to any one of claims 1 to 5, wherein the metal powder-containing resin layer further contains 1 to 30 parts by mass of metal Al powder with respect to 100 parts by mass of the binder.   The surface-treated steel sheet for fuel containers according to any one of claims 1 to 6, wherein the thermosetting resin is an epoxy resin.