JP4660598B2 - Method for producing tin-plated steel sheet with excellent post-retort coating adhesion - Google Patents

Description

  The present invention relates to a method for producing a tin-plated steel sheet that is used for food cans with resin coating such as painting.

  Tin-plated steel sheets are widely used as materials for metal cans. When the contents are fruit, the inner surface of the can may be used without painting, but with other contents, it is generally used with a resin coating such as painting. A variety of can contents are filled. Excluding acidic foods such as carbonated drinks, fruit juice drinks and fruits, most contents are retort sterilized after filling. For this reason, the tin-plated steel sheet as a raw material is required to have a coating film adhesion under a high temperature and humidity environment. In particular, the contents on the inner surface side are diverse, and the mechanism for reducing the adhesion of the coating film varies depending on the contents. Rather than preparing a tin-plated steel sheet material for each content, a material that can ensure coating film adhesion after retorting over a wide range of contents is desired. In addition, the tin-plated steel sheet material is sometimes transported in a high temperature range on a ship or stored for a long time in a warehouse, and it is required that the coating film adhesion after retort can be secured even after aging.

  Various proposals have heretofore been made for a method for producing a tin-plated steel sheet excellent in paint adhesion over time under wet conditions. For example, in Patent Document 1 below, a cleaning treatment step with an alkaline solution after a reflow step or nickel A cleaning process with strong acid containing ions has been proposed, and it is possible to ensure adhesion of the coating film after retorting. However, in conventional tin-plated steel sheet equipment, the cleaning process is used as the equipment. Incorporation requires major equipment modifications and is not realistic.

  Further, in Patent Document 2 below, a method has been proposed in which tin oxide of a tin-plated steel sheet is converted to orthorhombic SnO, and it is possible to ensure smudge property and primary adhesion. As for the next adhesion, sufficient adhesion could not be ensured.

Japanese Patent Laid-Open No. 7-11483 JP 54-142135 A

  This invention solves the problem of the prior art mentioned above, and makes it a subject to provide the manufacturing method of the tin plating steel plate excellent in the coating film adhesiveness after a retort, without performing big equipment remodeling.

The inventors of the present invention have made various studies on the reflow treatment conditions and the chemical conversion treatment conditions after tin plating and have arrived at the present invention. The gist of the present invention is as follows. Content.
(1) A method for producing a tin-plated steel sheet for cans, which comprises subjecting a cold-rolled steel sheet to tin plating, reflow treatment, and chemical conversion treatment. 0.0 g / m ² of tin plating is performed, and in the reflow process, reflow treatment is performed in an atmosphere having a water vapor concentration of 0 to 40 g / m ³ .
After immersion in sodium dichromate aqueous solution for 0.5 to 4.0 seconds without electrolysis, chemical conversion treatment by cathodic electrolysis is performed in sodium dichromate aqueous solution at a current of 0.8 to 6.5 C / dm ^2. The manufacturing method of the tin plating steel plate excellent in the retort adhesiveness characterized by the above-mentioned.
(2) In the said reflow process, the reflow process from which the melting time of tin plating becomes 0.1 to 0.7 second is performed, The manufacturing method of the tin plating steel plate excellent in the retort adhesiveness as described in (1) .

  According to the present invention, the combination of the control of the reflow conditions after tin plating and the securing of the electroless immersion time in the chemical conversion solution is excellent in retort adhesion that could not be stably obtained with conventional tin-plated steel sheets. It becomes possible to manufacture tin-plated steel sheets at low cost without incurring great expenses such as large equipment changes, and there are significant industrially useful effects.

Hereinafter, the present invention will be described in detail.
First, a cold rolled steel sheet is electrolytically degreased in an aqueous alkaline solution as a pretreatment for tin plating, and then pickled and electrotin plated. As the plating bath, a known tin plating bath, phenol sulfone bath, sulfuric acid bath, methanesulfonic acid bath, halogen bath, alkaline bath, or the like can be used. The amount of tin plating attached is at least 1.5 to 13.0 g / m ² on the inner surface side of the can. However, when the amount of tin attached is less than 1.5 g / m ² , the surface of the steel plate is completely covered with tin. Since it is not coated and iron is exposed, and iron is easily dissolved in acetic acid, adhesion of the coating film after retorting by heat sterilization with an acetic acid solution tends to be unstable, and sacrificial corrosion prevention of tin This is because the corrosion resistance becomes insufficient because the period is shortened. Moreover, when the adhesion amount of tin plating exceeds 13.0 g / m ² , the corrosion resistance can be sufficiently satisfied, and the effect of the tin weight is saturated, resulting in a cost disadvantage. Furthermore, the tin adhesion amount in the range of 2.0 to 4.0 g / m ² is preferable.

  Next, a reflow process for heating and dissolving the plated tin is performed. This reflow process changes the electroplated tin from a dull appearance to a glossy appearance. At the same time, a part of tin reacts with the base iron to form a tin-iron alloy layer effective for corrosion resistance.

On the other hand, tin oxide is generated on the surface of tin plating. There are two types of tin oxide produced here: SnO and SnO ₂ . Note that the reflow heating method is preferably an electric heating method, an induction heating method, or a combination of the electric heating method and the induction heating method in terms of temperature control.

  The present inventors have obtained the knowledge that by controlling this tin oxide in the reflow treatment step and the chemical conversion treatment step, the adhesion of the coating film after retort can be greatly improved without performing major equipment modifications. Invented.

That is, in the reflow process for melting the plated tin, the reflow process is performed in an atmosphere having a water vapor concentration of 0 to 40 g / m ³ or less, and the cathode electrolysis process in the sodium dichromate aqueous solution in the next chemical conversion process is performed. The most important point of the present invention is the combination of securing the electroless immersion time in the aqueous solution of sodium dichromate before 0.5 to 4.0 seconds.

When the water vapor concentration of the atmosphere in the reflow treatment exceeds 40 g / m ³ , among the tin oxides formed on the tin surface after the reflow treatment, SnO that decreases the adhesion of the coating film after retorting with the acetic acid solution increases. is there. Preferably, the upper limit of the water vapor concentration is 30 g / m ³ . The lower the water vapor concentration, the less SnO is produced and the better the coating film adhesion after retorting with an acetic acid solution.

  In the first stage of the chemical conversion treatment step, when the immersion time in electroless sodium dichromate aqueous solution is less than 0.5 seconds, the adhesion of the coating film after retorting with an acetic acid solution is greatly reduced. The reason for this is not clear, but SnO generated in the reflow treatment process dissolves by electroless immersion in an aqueous sodium dichromate solution. However, if the immersion time is short, the dissolution of SnO becomes insufficient and the acetic acid type It is presumed that the adhesion of the coating film after retorting with the solution is greatly reduced. In addition, when the electroless immersion time in the sodium dichromate aqueous solution exceeds 4.0 seconds, SnO is presumed to be sufficiently dissolved, and the coating film adhesion after retorting with an acetic acid solution is sufficient. However, in order to secure a soaking time of more than 4.0 seconds, it is necessary to significantly reduce the production speed or change the equipment layout in order to lengthen the chemical conversion treatment process. This is not preferable because the processing section becomes large and high capital investment is required. For this reason, the electroless immersion time in the sodium dichromate aqueous solution is 0.5 to 4.0 seconds, and more preferably 0.7 to 2.0 seconds.

  If the time for melting tin in the reflow process is less than 0.1 seconds, the formation of a tin-iron alloy layer effective for corrosion resistance may become uneven in the width direction or longitudinal direction of the steel sheet. Glossy appearance after melting causes problems such as being not uniformly obtained. On the other hand, if the time for melting tin exceeds 0.7 seconds, tin oxide increases. Naturally, SnO also increases, and the adhesion of the coating film after retorting with an acetic acid-based solution is lowered. For this reason, the time for melting tin in the reflow treatment step is preferably in the range of 0.1 to 0.7 seconds.

The next important point is the amount of cathodic electrolysis in the aqueous sodium dichromate solution in the second stage of the chemical conversion treatment step. Energization amount is 0.8~6.5C / dm ^2. If it is less than 0.8 C / dm ² , discoloration of the tin-plated steel sheet called yellowing may occur over time, and if it exceeds 6.5 C / dm ² , the effect of the chemical conversion treatment film is saturated and excessive chemical conversion treatment film As a result, the corrosion concentrates on one point, and there is a risk of piercing corrosion of the can body. More preferably, the range of 0.8 to 4.0 C / dm ² is preferable.

Cathodic current density at bichromate sodium in aqueous solution in the second stage of the chemical conversion treatment step is preferably in the range of 0.2 to 10.0 / dm ^2. The influence of the current density appears notably after time. Tin-plated steel sheets are sometimes stored in warehouses for a long time until they are transported or used in the equator, and this point needs to be taken into consideration. When the cathode current density is less than 0.2 A / dm ² , the adhesion of the coating film after retorting with an acetic acid-based solution when coated after a lapse of time is greatly reduced, and similarly, even when the cathode current density exceeds 10 A / dm ² The adhesion of the coating film after retorting with an acetic acid-based solution when applied after lapse of time is greatly reduced. This is presumably because the chemical conversion treatment film becomes non-uniform when the cathode current density is less than 0.2 A / dm ² and SnO on the surface of the tin-plated steel sheet grows with time. Further, when the cathode current density exceeds 10 A / dm ² , the coating of the chemical conversion treatment film becomes uniform, but the adhesion of the coating film after retorting by heat sterilization with an acetic acid solution decreases. The reason is unknown at this time. More preferably, it is the range of 0.2-5.0 A / dm < ² >.

  Furthermore, the bath temperature of the chemical conversion treatment is preferably in the range of 40 to 55 ° C. from the viewpoint of workability and equipment. Further, the concentration of sodium dichromate, which is the chemical conversion solution, is preferably in the range of 20 to 30 g / L from the viewpoint of workability and equipment.

  The chemical conversion treatment liquid is in a direction in which heat is applied to the bath due to the resistance heat generation of the solution during electrolysis, and in particular, a cooling device is required to control the bath temperature below 40 ° C. in the summer.

  Also, if the bath temperature exceeds 55 ° C, the amount of water vapor evaporated from the bath will increase, and it will be necessary to increase the frequency of bath concentration management. It is necessary to use a material with high corrosion resistance.

Examples of the present invention, comparative examples, and evaluation methods are described below.
<Invention Example 1>
A 0.20 mm thick cold-rolled steel sheet was electrolytically degreased with a 10% aqueous sodium hydroxide solution, washed with water, dipped in a 10% aqueous hydrochloric acid solution, washed with water, and then washed with 1.7 g / m ² tin in a phenolsulfonic acid bath. Plating was applied. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 1.3 C / dm ² .

<Invention Example 2>
The same pretreatment as in Invention Example 1 was performed, and a methanesulfonic acid bath 12.4 g / m ² tin plating was applied. Subsequently, the same reflow treatment was performed in the same atmosphere as in Invention Example 1, and the same cathodic electrolysis treatment was performed after electroless immersion as in Invention Example 1.

<Invention Example 3>
The same pretreatment as in Invention Example 1 was performed, and 2.1 g / m ² tin plating was applied in a phenolsulfonic acid bath. Subsequently, the same reflow treatment was performed in the same atmosphere as in Invention Example 1, and the same cathodic electrolysis treatment was performed after electroless immersion as in Invention Example 1.

<Invention Example 4>
The same pretreatment as in Invention Example 1 was performed, and 3.8 g / m ² tin plating was applied in a phenolsulfonic acid bath. Subsequently, the same reflow treatment was performed in the same atmosphere as in Invention Example 1, and the same cathodic electrolysis treatment was performed after electroless immersion as in Invention Example 1.

<Invention Example 5>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Subsequently, reflow treatment was performed in an atmosphere having a water vapor concentration of 37 g / m ³ to melt tin and rapidly cooled in 80 ° C. warm water. The melting time of tin was 0.42 seconds. Further, after the same electroless immersion as in Invention Example 1, the same cathodic electrolysis treatment was performed.

<Invention Example 6>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, reflow treatment was performed in an atmosphere having a water vapor concentration of 27 g / m ³ to melt tin and rapidly cooled in 80 ° C. warm water. The melting time of tin was 0.42 seconds. Further, after the same electroless immersion as in Invention Example 1, the same cathodic electrolysis treatment was performed.

<Invention Example 7>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The tin melting time was 0.12 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.0 second in a non-electrical state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 2.2 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 1.0 C / dm ² .

<Invention Example 8>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The tin melting time was 0.68 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 2.2 C / dm ² .

<Invention Example 9>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 0.6 seconds in a non-electrical state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 1.3 C / dm ² .

<Invention Example 10>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The tin melting time was 0.65 seconds. Next, it was immersed in an aqueous solution of sodium dichromate at 50 ° C. and 25 g / L for 3.7 seconds in an uncharged state, and then at a current density of 1.8 A / dm ² in an aqueous solution of sodium dichromate at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by a second-stage cathodic electrolysis at a current density of 1.1 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The energization amount was 1.9 C / dm ² .

<Invention Example 11>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 0.8 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 1.3 C / dm ² .

<Invention Example 12>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The tin melting time was 0.65 seconds. Next, it was immersed in an aqueous solution of sodium dichromate at 50 ° C. and 25 g / L for 1.8 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in an aqueous solution of sodium dichromate at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 2.2 C / dm ² .

<Invention Example 13>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 0.3 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 1.1 C / dm ² .

<Invention Example 14>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 9.0 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 1.6 C / dm ² .

<Invention Example 15>
The same pretreatment as in Invention Example 1 was performed, and 2.6 g / m ² tin plating was applied in a methanesulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 4.6 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 1.4 C / dm ² .

<Invention Example 16>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis in a 25 g / L sodium dichromate aqueous solution at a current density of 0.3 A / dm ² . The energization amount was 2.2 C / dm ² .

<Invention Example 17>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 1.8 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L at a current density of 9.0 A / dm ² . The energization amount was 1.6 C / dm ² .

<Invention Example 18>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 4.6 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The energization amount was 3.0 C / dm ² .

<Invention Example 19>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by a second-stage cathodic electrolysis at a current density of 1.1 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The energization amount was 0.9 C / dm ² .

<Invention Example 20>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The tin melting time was 0.65 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 4.5 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The energization amount was 6.2 C / dm ² .

<Invention Example 21>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The tin melting time was 0.65 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.4 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by a second-stage cathodic electrolysis at a current density of 3.4 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 3.7 C / dm ² .

<Invention Example 22>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 42 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 42 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in a sodium dichromate aqueous solution at 42 ° C. and 25 g / L. The energization amount was 1.3 C / dm ² .

<Invention Example 23>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in an aqueous solution of sodium dichromate at 53 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in an aqueous solution of sodium dichromate at 53 ° C. and 25 g / L. The first-stage cathodic electrolysis treatment was further performed, and then the second-stage cathodic electrolysis treatment was performed at 53 ° C. in a 25 g / L sodium dichromate aqueous solution at a current density of 1.8 A / dm ² . The energization amount was 1.3 C / dm ² .

<Invention Example 24>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 22 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in an aqueous solution of sodium dichromate at 50 ° C. and 22 g / L. The first-stage cathodic electrolysis was further performed, followed by a second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in a 50 g, 22 g / L sodium dichromate aqueous solution. The energization amount was 1.3 C / dm ² .

<Invention Example 25>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in an aqueous solution of sodium dichromate at 50 ° C. and 28 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in an aqueous solution of sodium dichromate at 50 ° C. and 28 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 28 g / L. The energization amount was 1.3 C / dm ² .

<Invention Example 26>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.0 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 1.3 C / dm ² .

<Invention Example 27>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 2.2 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. Cathodic electrolysis was performed. The energization amount was 1.3 C / dm ² .

<Invention Example 28>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.08 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 0.9 C / dm ² .

<Invention Example 29>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.73 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.0 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by a second-stage cathodic electrolysis at a current density of 1.1 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. Energization amount was 2.1C / dm ^2.

<Comparative Example 1>
The same pretreatment as in Invention Example 1 was performed, and 1.2 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1 second in an uncharged state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 1.3 C / dm ² .

<Comparative Example 2>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, reflow treatment was performed in an atmosphere having a water vapor concentration of 45 g / m ³ to melt the tin and rapidly cooled in 80 ° C. warm water. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 1.3 C / dm ² .

<Comparative Example 3>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 0.3 seconds in a non-electrical state, and then at a current density of 3.7 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 1.8 A / dm ² in an aqueous sodium dichromate solution at 50 ° C. and 25 g / L. The energization amount was 1.3 C / dm ² .

<Comparative example 4>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 0.9 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by the second-stage cathodic electrolysis at a current density of 0.9 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The energization amount was 0.6 C / dm ² .

<Comparative Example 5>
The same pretreatment as in Invention Example 1 was carried out, and 2.6 g / m ² tin plating was performed in a phenolsulfonic acid bath. Next, a reflow treatment was performed in an atmosphere having a water vapor concentration of 25 g / m ³ to melt tin and quench in hot water at 80 ° C. The melting time of tin was 0.42 seconds. Next, it was immersed in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L for 1.5 seconds in an uncharged state, and then at a current density of 4.2 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The first-stage cathodic electrolysis was further performed, followed by a second-stage cathodic electrolysis at a current density of 4.2 A / dm ² in a sodium dichromate aqueous solution at 50 ° C. and 25 g / L. The energization amount was 6.9 C / dm ² .

The tin-coated steel sheets obtained in Invention Examples 1 to 29 and Comparative Examples 1 to 5 were subjected to the following paint adhesion evaluation test, and the results are shown in Tables 1 and 2.
<Evaluation method>
(1) Painting and molding An epoxy phenol coating was applied to the sample surface at 8 g / m ² , heated at 204 ° C. for 10 minutes, and then cooled to room temperature. Furthermore, after storing at room temperature for 8 hours or more, an END (can lid) of φ200 was molded so that the painted surface became the inner surface of the can.
(2) Retort adhesion The molded END (can lid) was immersed in four types of aqueous solutions and retorted at 120 ° C. for 90 minutes. Immediately after completion of the retort, water washing, crosscutting, and tape peeling test were performed.
The crosscut formed a grid of 100 squares at a pitch of 3 mm, and evaluated the adhesion in 10 stages (10 points for no peeling, 1 point for 100% peeling) according to the peeling area in the tape peeling test. In the test with four kinds of immersion liquids, all of the adhesion points of 7 or more were regarded as acceptable.
The following four types of immersion liquids were used.
A: 3% acetic acid + 2% NaCl
B: 1.1% lactic acid C: 2% citric acid + 0.4% ascorbic acid D: 0.056% cysteine HCl + 0.4% KH ₂ PO ₄ + 0.81% Na ₂ HPO ₄
(3) Aging test The prepared tin-plated steel sheet was packed in rust-proof paper at 50 ° C. and a humidity of 90% RH, stored for 7 days under the same conditions, and then under the same conditions as in (1) and (2) above. Retort adhesion was evaluated.

Inventive Examples 1 to 29 satisfy the conditions of the present invention, so that the appearance is all good, and the immersion liquids A to D are used in all cases where the aging treatment is not performed and when the aging treatment is performed. In any of the cases, the retort adhesion evaluation result was 7 points or more.
On the other hand, Comparative Example 1 had a tin plating amount of 1.2 g / m ^{2 and} was less than the range of the invention, so that the gloss was very low, and the retort adhesion evaluation results for immersion liquids A and D were 6 points or less.
In Comparative Example 2, since the water vapor concentration in the atmosphere of the reflow treatment was 45 g / m ³ and exceeded the range of the invention, in the case of the immersion liquid A, the retort adhesion evaluation result was 6 points or less.
In Comparative Example 3, since the second immersion time in an electroless state in an aqueous sodium dichromate solution was 0.3 seconds and less than the range of the invention, the retort adhesion evaluation result for the immersion liquid A was 6 points or less.
In Comparative Example 4, the energization amount in the electrolytic treatment of the chemical conversion treatment was 0.6 C / dm ² , which was less than the scope of the invention, so the retort adhesion evaluation result for the immersion liquid D was 6 points or less.
In Comparative Example 5, the energization amount in the electrolytic treatment of the chemical conversion treatment was 6.9 C / dm ² and exceeded the scope of the invention, so the retort adhesion evaluation result for the immersion liquid A after the aging treatment was 6 points or less.
The effects of the present invention were confirmed by the above examples.

Claims (2)

A method for producing a tin-plated steel sheet for cans that is subjected to tin plating, reflow treatment, and chemical conversion treatment on a cold-rolled steel sheet,
In the tin plating step, 1.5 to 13.0 g / m ² of tin plating is applied to the side of the steel plate that becomes the inner surface of the can.
In the reflow process, reflow treatment is performed in an atmosphere having a water vapor concentration of 0 to 40 g / m ³ ,
After immersion in sodium dichromate aqueous solution for 0.5 to 4.0 seconds without electrolysis, chemical conversion treatment by cathodic electrolysis is performed in sodium dichromate aqueous solution at a current of 0.8 to 6.5 C / dm ^2. The manufacturing method of the tin plating steel plate excellent in the retort adhesiveness characterized by the above-mentioned.   2. The method for producing a tin-plated steel sheet having excellent retort adhesion according to claim 1, wherein in the reflow step, a reflow process is performed in which the melting time of tin plating is 0.1 to 0.7 seconds.