JP2006089792A - Method for producing galvanized steel sheet for fuel container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a galvanized steel sheet for a fuel container which can inexpensively solve the problem on various performance required for the internal side and the external side in the fuel container using galvznized steel sheet such as fuel corrosion resistance of the internal face and corrosion resistance after coating in the external face by controlling the drying conditions for a posttreatment film. <P>SOLUTION: A posttreatment film is applied onto the surface of the galvanized steel sheet by 0.1 to 2.0 g/m<SP>2</SP>as coating weight, and then is heated from the plated surface side at a heating rate of ≥20°C/s to dry the posttreatment film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The method of the present invention relates to a method for producing a zinc-based steel plate for a fuel container.

  With the recent movement toward environmental regulations, market needs for materials that do not use hazardous metals are increasing. In the automotive field, there is a high demand for lead-free materials for lead-tin alloy-plated steel sheets (hereinafter abbreviated as turn sheets), which have been the mainstream material for fuel containers.

  Many proposals have been made using galvanized steel sheets that have a proven track record for automobile interior and exterior plates and are superior in cost to the specific required performance of fuel containers, ie, internal corrosion resistance while the fuel is sealed. (Patent Documents 1 to 6)

  Corrosion resistance to various organic acids generated by deterioration of the fuel is required for the inner surface corrosion resistance. Zinc usually dissolves easily in organic acids, so if it is used on a zinc-plated steel sheet without any special surface treatment, it dissolves rapidly and eventually reaches the steel sheet substrate, causing perforation. End up. Therefore, materials that can sufficiently exhibit corrosion resistance even in poor fuels containing organic acids have been developed by applying post-plating treatment such as chromate treatment to zinc-based materials.

  However, it cannot be said that the above-mentioned deteriorated fuel corrosion resistance alone is sufficient for the inner surface corrosion resistance of the fuel container. In the market, as water draining agents are commercially available, rusting troubles in the fuel container due to water generated mainly due to condensation cannot be ignored. Therefore, in the fuel container, the corrosion resistance performance due to the generated condensed water should be fully examined. As known in Patent Document 6, a water-repellent film is effective for corrosion resistance against condensed water, and it is effective that the surface of the steel sheet is more hydrophobic.

  In addition, as long as the fuel container is exposed to the atmosphere, the post-paint corrosion resistance on the outer surface side is required to be the same as that of the automobile body, and not only the various fuel corrosion resistance but also the external performance such as paint adhesion and post-paint corrosion resistance. It is essential to do.

  The coating suitability with various plated steel sheets varies greatly depending on the properties of the paint used. The properties of the paints are roughly classified into solvent-based and water-based systems. Recently, water-based paints are increasingly used especially for automobile materials in consideration of environmental load. In the case of using a water-based paint, the steel sheet to which the paint is applied must be compatible with water, and the surface of the steel sheet is required to be hydrophilic.

  That is, in order to reduce the load on the environment to the maximum extent, the required properties are greatly different on the inner and outer surfaces of the fuel container, and a hydrophilic surface on the outer surface and a hydrophobic surface on the inner surface side are required. Of course, it is effective to change the type of film on the front and back as known in Patent Document 2, Patent Document 3, and Patent Document 4 for this problem, but changing the type of film on the inner and outer surfaces is a production cost. Compulsory increase. Further, although there is a means for controlling the contact angle with water in Patent Document 6, it imposes operational difficulties.

As far as the production method of fuel container materials mainly composed of zinc is concerned with the various performances required for the inner and outer surfaces of the fuel container, the manufacturing means that enable this at a low cost are always fully evaluated. It cannot be said that it is done.
Japanese Patent Laid-Open No. 62-27587 JP-A-10-265964 JP-A-10-291278 Japanese Patent Laid-Open No. 10-305517 JP 2001-323388 A JP 2004-169122 A

  In view of the above problems, the present invention is required for a fuel container such as an inner surface fuel corrosion resistance and an outer surface corrosion resistance after coating with a zinc-based plated steel sheet that has a proven record in automobile inner and outer plates and is superior in cost. The present invention provides a method for producing a steel sheet for a zinc-based fuel container, which solves various performances without incurring process costs as much as possible.

The inventors of the present invention first examined a film that exhibits internal corrosion resistance. As a result, it was found that the performance varies depending on the treatment of the film and the drying conditions. That is, if the drying is performed slowly for a long time (for example, 10 seconds or more), excellent inner surface performance is exhibited. However, if the drying is performed for a short time (for example, within 5 seconds), the inner surface performance varies.
Next, the suitability of the coating on the outer surface side, particularly the water-resistant secondary adhesion and the outer surface corrosion resistance, was examined. Long drying can be easily achieved by reducing the production rate, but this leads to a decrease in productivity and an increase in cost.

  Therefore, intensive studies were made on means for satisfying the performance of the inner and outer surfaces by drying in a short time. As a result, after applying the post-treatment liquid, it is effective for exerting performance to heat the steel plate itself quickly in a short time, rather than externally heating, to accelerate the reaction between the plating surface and the post-treatment film and to dry it. I found out.

The present invention was made based on the above findings, and the gist of the present invention is as follows:
(1) After depositing 0.1 to 2.0 g / m ² with a post-treatment film on the zinc-based plated steel sheet, the temperature is raised from the plating surface side at a rate of 20 ° C./s or more. A method for producing a steel sheet for a zinc-based fuel container, wherein the post-treatment film is dried;
(2) The method for heating a zinc-based fuel container according to (1) above, wherein the method of heating and heating from the plating surface side at a rate of 20 ° C./s or more is either induction heating or current heating. Steel plate manufacturing method,
(3) Zinc-based plated steel sheet is electrogalvanized, hot-dip galvanized, electrogalvanized-iron alloy electroplated containing 25% or less of iron, alloyed hot-dip galvanized containing 25% or less of iron, or less than 25% of nickel The method for producing a steel sheet for a zinc-based fuel container according to the above (1) and (2), wherein the zinc-nickel alloy plating is any one of
(4) On the galvanized steel sheet, 10 g / m ² with an adhesion amount of either an iron-zinc alloy plating layer or nickel plating layer having 80% iron (mass%, the same applies hereinafter) or more as the second layer. The method for producing a steel sheet for a zinc-based fuel container according to (1), (2), or (3), characterized in that:
It is.

  As described above, the present invention changes the type of each coating for the independent performance of the inner and outer surfaces required for the fuel container material, and classifies the means for forming the coating for each of the inner and outer surfaces. It has been made possible at low cost, and the contribution to the industry is extremely large.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a conceptual diagram illustrating an embodiment of the present invention, where 1 is a base material, 2 is galvanized, 3 is Ni plating of the second layer, 4 is a post-treatment layer, and 5 is an arrow indicating the heat transfer direction. Show. By heating the base material 1, heat is transferred in the direction as indicated by the arrow 5 to dry the post-treatment film from the plating surface.

The amount of the post-treatment film in the present invention is required to be 0.1 g / m ² or more, and if it is less than this, the inner and outer surface corrosion resistance becomes insufficient. On the other hand, if it exceeds 2.0 g / m ² , the coating adhesion gradually deteriorates, so the upper limit is 2.0 g / m ² .
Drying of the post-treatment film requires a rate of 20 ° C./s or more at the steel plate temperature. The heating rate of the post-treatment liquid is not limited as long as the heating rate of the steel sheet is 20 ° C./s or more. The reason why the performance is improved by heating the steel plate to dry the post-treatment film from the plating surface side is not clear, but by increasing the film formation rate of the post-treatment film on the outermost surface of the plating, This is probably because the orientation, film-forming property, adhesion, etc. were improved.
When the temperature increase rate of the steel sheet is lower than 20 ° C./s, the film formation rate becomes slow, so that the film formation at the plating / post-treatment film interface does not occur precisely, and the corrosion resistance on the inner surface side varies. The upper limit is not particularly defined, but at an extreme rate of increase exceeding 100 ° C./s, a bumping phenomenon in which the post-treatment liquid suddenly evaporates may occur, and the film may be defective. preferable.

  The maximum attainable temperature of the steel sheet is not particularly defined, and depends on the type of post-treatment film, and there is no problem as long as it is in a temperature range in which decomposition of components constituting the film does not occur. However, if the ultimate temperature of the steel sheet exceeds 400 ° C., alloying between the zinc during plating and the base steel sheet proceeds, and there is a concern such as deterioration of plating adhesion. Generally, it is 250 degrees C or less. Moreover, the minimum attainment temperature of a steel plate is not specifically defined, What is necessary is just to select according to the kind of post-processing film | membrane, and 80 to 150 degreeC is common.

  The method for raising the temperature of the steel sheet is not particularly limited as long as it is a method of heating and heating from the steel sheet side, but from the viewpoint of ease of operation and productivity, an induction heating method and an electric heating method are preferable. Since it is the gist of the present invention that the steel sheet itself is rapidly heated and the post-treatment is dried by the heat to form a film, a general drying furnace using a burner or hot air is not suitable. These external heating can ensure the rate of temperature rise of the steel sheet at 20 ° C./s or more, but the temperature of the post-treatment rises before the steel plate temperature rises, and from the plating surface / post-treatment interface. Since it is not dry, no performance improvement is observed. However, there is no problem in the present invention in that various hot-air type drying furnaces are further installed or used after heating and heating to a predetermined steel plate temperature with equipment for heating and heating from the plating surface side.

  The kind of the post-treatment film is not particularly limited. For example, as a component constituting the film, an acrylic resin, a phenol resin, a urethane resin, or a modified one thereof is used alone, or two or more kinds thereof are used. It can be used in a mixed manner, and a multi-layer treatment may be carried out if necessary. Furthermore, the post-treatment film is made of other resin components, oxides such as silica, titania and zirconia, hexavalent chromium, trivalent, for the purpose of enhancing the performance of the treatment film and ensuring the stability of the treatment liquid. It may contain chromium, other metal ions, or organic components. The method for attaching the post-treatment film is not limited, and a method according to production equipment such as a roll coater, an air knife, or an electrolytic method can be employed.

The zinc-based plating used for the base material is preferably hot dip galvanizing, alloyed hot dip galvanizing, electro galvanizing, electro zinc-iron alloy plating, electro zinc-nickel alloy plating, etc. in view of its versatility. The plating adhesion amount does not affect the present invention at all, and for example, an adhesion amount of 20 to 120 g / m ² per one surface generally used for automobiles can be adopted.
Further, an iron-zinc alloy plating layer having 80% or more of iron or a nickel plating layer can be applied to the upper layer of these zinc-based platings for the purpose of improving weldability, formability, paintability, and the like.

  The steel plate used in the present invention is mainly Fe, and other additive elements include C, Si, Mn, P, S, Cu, Ni, Cr, Mo, Co, Al, Nb, V, Ti, and Zr. , Hf, Bi, Sb, B, N, O, rare earth elements, Ca, Mg included in accordance with the characteristics required for the steel sheet, and inevitable impurities such as Sn and As To do. Moreover, the plate | board thickness of the steel plate used in this invention is not restrict | limited at all, The plate | board thickness normally used, for example, about 0.3 mm-4 mm, can be used. Next, the Example of this invention is given with a comparative example.

Table 1 shows the types of galvanization, post-treatment film types, each treatment method, and drying conditions. The adhesion amount of the base plating was 45 g / m ^2, and a Ni plating layer 5 g / m ² on the upper layer was used as a base material, and a post-treatment film was further applied. In consideration of productivity, the post-treatment film was dried in 5 seconds. When the plate temperature exceeded 250 ° C. within 5 seconds, the remaining drying time was maintained at 250 ° C. After drying, it was rapidly cooled to room temperature with cold air.

These samples were subjected to deteriorated fuel corrosion resistance, condensation water corrosion resistance, paint adhesion, and post-paint corrosion resistance.
As for the deteriorated fuel corrosion resistance and the dew condensation water corrosion resistance, various corrosive liquids were enclosed in a cylindrical molded body having an inner diameter of 50 mm and a depth of 35 mm. Corrosion resistance of deteriorated fuel is as follows: ◎: No corrosion, ○: Practical problem in the condition of corrosion after enclosing gasoline containing formic acid 100ppm, acetic acid 300ppm, water 1.0% by volume and holding at 30 ℃ for 2 months No minor corrosion, Δ: Partially corroded, ×: Corrosion over the entire surface. Condensation water corrosion resistance is the corrosion state after filling gasoline containing 50.0% by volume of water and holding it at 30 ° C for 2 months. ◎: No corrosion, ○: Minor corrosion with no practical problem, △ : Partially corroded, x: Corrosion over the entire surface.
Paintability is 20 μm after coating with an alkydmelanin-based water-based black paint, and then a cross-cut peel test and a water resistance secondary adhesion test (40 ° C. pure water, cross-cut peel test after 240 hours of immersion) are conducted. , ○: Mild peeling less than 5% of the grid, Δ: peeling exceeding 5% of the grid, and x: peeling exceeding 50% of the grid.
Corrosion resistance after painting is as follows: JASO (M609) 90 cycles of cross-cut coating material, ◎: rust width within 1 mm, ○: rust width within 3 mm, △: rust width within 5 mm, ×: rust width over 5 mm did. The results are shown in Table 2.

  All of the inventive examples in Table 2 were excellent in inner surface corrosion resistance, coating adhesion, and post-coating corrosion resistance. On the other hand, Comparative Example 1 had an excessively large coating amount and poor external surface performance, and Comparative Example 2 had an excessively small coating amount and poor internal surface performance. In Comparative Example 3, the temperature rising rate of drying was too low, and the resin was not sufficiently formed, and various performances were inferior. Moreover, in the comparative example 4 using a warm air drying system, the outer surface performance was inferior.

It is explanatory drawing of the manufacturing method of the steel plate for zinc fuel containers of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 2 Zinc plating layer 3 Ni plating layer 4 Post-treatment film 5 Arrow which shows electric heating direction

Claims (4)

After depositing 0.1 to 2.0 g / m ² on the zinc-plated steel sheet, the post-treatment film is heated from the plating surface side at a rate of 20 ° C./s or higher. A method for producing a steel sheet for a zinc-based fuel container, wherein the steel is dried.   The method for producing a steel sheet for a zinc-based fuel container according to claim 1, wherein the method of heating and heating from the plating surface side at a rate of 20 ° C / s or more is either induction heating or current heating. .   Zinc-based steel sheet is electrogalvanized, hot dip galvanized, electrogalvanized-iron alloy electroplated containing 25% or less of iron, galvannealed alloy containing 25% or less of iron, electrozinc containing 25% or less of nickel The method for producing a steel sheet for a zinc-based fuel container according to claim 1 or 2, wherein the method is any one of nickel alloy plating. On the galvanized steel sheet, 10 g / m ² or less is applied as the second layer, with an iron-zinc alloy plating layer or nickel plating layer having 80% (mass%, the same applies hereinafter) or more of iron as the second layer. The method for producing a steel sheet for a zinc-based fuel container according to claim 1, 2 or 3, wherein a post-treatment film is further applied to the upper surface of the second layer.

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