JP2703787B2 - Surface-treated steel plate two-piece can and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention is a so-called surface-treated steel can used for packing various products including soft drinks, beer, and other foods, in particular, a so-called unified can bottom and a can body as a side portion. It is about a two-piece can.

[Prior art]

As the material of the two-piece can, an aluminum alloy plate, tinplate, and a surface-treated steel plate containing no tin, so-called TFS-CT (electrolytic chromic acid-treated steel plate), or the like is mainly used. A can using an aluminum alloy plate can prevent the generation of red rust on the outer surface, but increases the cost. Tin-plated, TFS-CT, and other surface-treated steel sheets are inexpensive, but can be easily rusted on the outer surface of the can body and can bottom during production of cans and during the distribution and storage stage, which can detract from commercial value. . Especially when placed on the shelf of a refrigerated showcase, red rust adheres to the saucer and sometimes cannot be removed even by wiping. In the vicinity of the center of the can body and the bottom of the can, rust can be prevented by applying an organic coating to such an extent that the commercial value is not impaired. However, with respect to the grounding portion at the bottom of the can (the portion that comes into contact with the flat plate when the can is placed on the flat plate), it is not sufficient to simply apply the organic coating. The grounding part of the can bottom is rubbed quite frequently during the production of cans and during the distribution stage, and not only the coated organic coating but also the plating layer below it is shaved,
Frequently, rust may be generated to impair the commercial value.

[Problems to be solved by the invention]

As a material of a can body for canning, tinplate is mainly used among surface-treated steel sheets. Tin is a mild steel plate which is obtained by plating tin on the surface of a mild steel plate and then performing a chromate treatment, and is excellent in corrosion resistance and workability. However, since tin has a lower ionization tendency than iron, it does not act as a sacrificial corrosion inhibitor on the steel sheet in the atmosphere, but merely coats the surface of the steel sheet. For this reason, tin cans have the disadvantage that rust occurs as described above if the tin layer is damaged and the steel surface is exposed. The present invention provides a two-piece can made of a surface-treated steel sheet having excellent corrosion resistance due to a sacrificial anticorrosive action on the steel sheet, and a method for producing the same, by taking advantage of the excellent corrosion resistance and workability of the surface-treated steel sheet.

[Means for Solving the Problems]

The present invention for solving the above-mentioned problems will be described below with reference to the drawings. A first invention to which the present invention is applied is a two-piece can made of a surface-treated steel sheet, which is formed of a steel sheet in which a plating layer of at least one of tin, nickel and chromium is covered with a chromium hydrated oxide. The object 1 (see FIG. 1) is characterized in that at least the grounding portion 10 is partially plated with an alloy of tin and zinc having a zinc content of 2 to 20% by weight. Similarly, a second invention is a method for producing a two-piece can made of surface-treated steel sheet, wherein the surface of the steel sheet is plated with one or more metals of tin, nickel, and chromium, and further covered with a chromium hydrated oxide layer to perform surface treatment. A steel plate is formed into a can 1 (see FIG. 1), and at least a ground contact portion of the can 1 (see FIG. 2)
The present invention is characterized in that while the can 10 is immersed in the tin and zinc plating bath 5, the tin body and the plating bath 5 are energized to partially coat the tin and zinc alloy in the grounding portion 10. Similarly, the third invention also relates to a method for producing a two-piece can made of surface-treated steel sheet, wherein the plating bath 5 of the second invention is a bath in which a gap between a groove of a rotating disk and a can body is impregnated with an electrolytic plating solution 7. It is characterized by being.

[Action]

The surface-treated steel plate two-piece can 1 of the present invention has a corrosion resistance due to a sacrificial anticorrosion effect on the steel sheet because the partial plating of the surface of the grounding portion 10 is made of an alloy plating of tin and zinc and the content of zinc is 2 to 20% by weight. It will be excellent. In the case of plating only with tin, if the plated portion is damaged and the steel surface is exposed, tin does not act as a sacrificial anticorrosion for iron, so that the steel rusts. Attempts to prevent this by merely increasing the amount of tin plating would be uneconomical, and would increase the plating time and reduce workability. On the other hand, plating with zinc only
Although it acts as a sacrificial anti-corrosion agent for iron and can prevent rust, zinc is eluted abnormally in a short time due to the large potential difference between iron and zinc, and long-term effects cannot be expected. Zinc is liable to cause white rust and is inferior in appearance. When the content of zinc is less than 2% by weight, the sacrificial anticorrosive action of zinc is not sufficiently exhibited, and rust occurs as in the case of only tin. On the other hand, when the zinc content exceeds 20% by weight, as in the case of plating with zinc alone, abnormal elution of zinc is observed and white rust occurs.

【Example】

Hereinafter, embodiments of the present invention will be described in detail. The two-piece can made of the surface-treated steel sheet of the present invention is obtained by the following steps. First, the surface of a mild steel plate is plated with a metal such as tin, nickel, and chromium, and then subjected to a chromate treatment. Of course, ready-made tin or TFS-CT may be used. This is drawn or ironed to obtain a can body. The can 1
As shown in FIG. 2, a predetermined weight ratio of an alloy of tin and zinc is partially plated on the grounding portion 10 and a portion around the grounding portion 10 to complete it. The above steps are performed by the apparatus shown in FIG. The cans 1 that have been molded and surface-treated and washed are successively conveyed to predetermined positions by a turntable 9, held by a vacuum pad 2, and transferred to the grooves 4 of the rotating disk 3. The rotating disk 3 rotates in the direction of the arrow in the figure, during which the ground portion 10 of the can 1 is plated. The vacuum pad 2 rotates in synchronization with the rotation of the rotating disk 3. The peripheral portion of the groove 4 is made of an electrically insulating material, and its width is larger than the diameter of the can 1, so that the can 1 can be taken in and out. As shown in FIG. 2, the rotating disk 3 has a groove 4 in which a plating bath 5 is formed. The plating bath 5 is divided into upper and lower parts by a perforated plate 6. A sponge 8 of open cells is placed on the upper part, and the plating solution 7 is filled and circulated on the lower part, so that the liquid concentration can be easily controlled. The plating solution 7 is passed through the perforated plate 6 and sponge 8
Is always absorbed. On the other hand, an electrode plate 13 connected to the anode of the power supply 12 is embedded in the groove 4. Vacuum pad 2
Is connected to the cathode of the power supply 12. Accordingly, when the can body 1 held by the vacuum pad 2 is pressed against the sponge 8, electricity is supplied to start electroplating, and predetermined plating is completed on the ground portion and the peripheral portion by one rotation until reaching the outlet. In order to achieve a predetermined zinc content by tin-zinc alloy plating, the tin-zinc ratio in the plating solution can be adjusted. In this case, tin chloride, sulfate, zinc chloride and sulfate can be used as the plating solution.
The current density is preferably about 5 to 10 A / dm ² . The surface of the tin, nickel, and chromium-plated steel sheets formed into the can body is subjected to a chemical conversion treatment, and is coated with a thin film of chromium hydrated oxide as a poor conductor of electricity. Therefore, when carrying out the present invention, in the step of plating the alloy of tin and zinc, a pretreatment may be required depending on the quality of the conductivity. Chromium hydrate oxide thin film thickness of 10 mg like tinplate
If the thickness is less than / m ² , the conductivity is good and no pretreatment is required. Chromium hydrated oxide thin film thickness of 100 like TFS-CT
When the conductivity is poor at mg / m ² or more, it is necessary to remove this coating in advance by applying a current-carrying cathodic treatment to a plating site in a sulfuric acid or hydrochloric acid acidic bath. Examples will be described below. Using a tin-plated steel sheet having a sheet thickness of 0.29 mm and a tin basis weight of 2.8 g / m ^2, a DI can was manufactured by DI (drawing and ironing) processing. After washing the can, the zinc content was 2% by weight, 4% by weight, 6% by weight, 10% by weight,
15% by weight and 20% by weight of tin and zinc alloy plating were applied.
Plating solution used _{was, SnSO 4: 100~300g / l,} ZuSO 4 · 6H
₂ O: 40 to 150 g / l, Na ₂ SO ₄ : 100 g / l, citric acid 20 g / l. The energization conditions are as follows: bath temperature around 50 ° C, current density 5
It is a 10A / dm ^2. This tin-plated steel sheet has a thin chromium hydrate oxide film thickness of 10 mg / m ² or less and has good conductivity, so it is necessary to perform a pretreatment for energization before plating the alloy of tin and zinc. Never After this alloy plating, can 1
The inner and outer surfaces, the grounding portion 10, the dome portion 11 (see FIG. 1) and the like were coated with an ordinary coating using an organic coating. The resulting DI can was subjected to a rust test under the following conditions (1), (2) and (3). (1) Immerse in warm water for 7 days. (2) After rubbing the grounding part with sandpaper, it is immersed in water at room temperature for 7 days. (3) After rubbing the ground part with sandpaper, the relative humidity
Place in 100% desiccator and leave in 50 ° C constant temperature room for 3 days. The results are shown in Examples 1 to 6 in Table 1. In Comparative Examples 1 to 5, alloy cans having a zinc content of 0.5% by weight, 1% by weight, 25% by weight, and 30% by weight were prepared by adding a predetermined concentration of tin and zinc to a plating solution and a can having no alloy plating. Were prepared, and a rust test under the same conditions was performed for comparison.

【The invention's effect】

As described in detail above, the surface-treated steel sheet two-piece can of the present invention is provided with tin and zinc alloy plating, which has a sacrificial anticorrosion effect on iron even in the air, on the grounding portion and its peripheral portion. Excellent rust property. Therefore, even if the steel surface is damaged at any stage of distribution, there is no concern about the occurrence of red rust, and it can be replaced with an expensive aluminum alloy can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a two-piece can made of a surface-treated steel sheet of the present invention, FIG.
The figure is a perspective view of a main part of a manufacturing process. DESCRIPTION OF SYMBOLS 1 ... Steel two-piece can, 2 ... Vacuum pad 3 ... Rotating disk, 4 ... Groove, 5 ... Plating bath 6 ... Perforated plate, 7 ... Plating solution, 8 ... Sponge 9 ... Turntable, 10 ... Grounding part 11 ... Dome, 12… Power supply, 13… Electrode plate

Claims (3)

(57) [Claims] 1. A can body formed of a steel sheet in which a plating layer of at least one metal of tin, nickel and chromium is covered with a hydrated chromium oxide layer, wherein at least the grounding portion has a zinc content of 2%. A two-piece can made of a surface-treated steel sheet, wherein an alloy of tin and zinc of up to 20% by weight is partially plated. 2. The surface of a steel sheet is plated with at least one metal selected from the group consisting of tin, nickel, and chromium, and the surface-treated steel sheet covered with a chromium hydrated oxide layer is formed into a can body. A method for producing a two-piece can made of surface-treated steel sheet, characterized in that at least the grounding part is immersed in a tin and zinc plating bath and a current is applied to the can body and the plating bath to partially coat the tin and zinc alloy in the grounding part. . 3. A two-piece can made of surface-treated steel sheet, wherein the plating bath according to claim 2 is a bath in which a gap between a groove of a rotating disk and a can body is impregnated with an electrolytic plating solution. Manufacturing method.