JP3256009B2 - Tinplate surface treatment liquid and surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is a tinplate (tin-plated steel)
More specifically, the present invention relates to a surface treatment solution and a treatment method for a phosphate of a material, and more specifically, to a molded product such as a tinplate, a strip, and a can, before coating and printing, excellent corrosion resistance and paint on the surface. The present invention relates to an improvement in treatment applied to impart adhesion. In particular, the processing solution and the processing method of the present invention apply the DI processing (drawing & ironing) to tinplate.
This is suitable for the surface treatment of tinplate formed by the above. That is, the present invention reduces the productivity of tinplate surface treatment lines when applied to the surface of tinplate to impart excellent corrosion resistance and paint adhesion to the surface, and tin ions eluted in the liquid. And a novel tinting material surface treatment technique that has no or very little precipitation of insoluble salts (hereinafter referred to as “sludge”) caused by iron ions.

[0002]

BACKGROUND OF THE INVENTION Cleaning and surface treatment of tinplates is often performed by spraying. For example, the surface treatment equipment for tinplate DI cans is usually called a washer, and the formed DI cans are continuously treated with a cleaning liquid or a surface treatment liquid in an inverted state. Existing washers are pre-washed,
It consists of six steps of washing, water washing, surface treatment, water washing, and deionized water washing, all of which are performed by spraying.

With respect to the surface treatment solution for tinplate DI cans, the composition comprising phosphate ions, tin ions and an oxidizing agent is well known. Report ”'8
9, No. 2 As discussed on page 6, it consists of an elution reaction of tin and iron (anode reaction) and precipitation of insoluble phosphate (cathode reaction). Further, the invention of Japanese Patent Application Laid-Open No. 1-110081 has been proposed as a composition proposed by the present applicant for the purpose of reversing the tin-iron potential in a chemical conversion bath (that is, using a tin portion as an anode and an iron portion as a cathode). Can be According to the present invention, phosphate ions 1 to 50 g / L, oxyacid ions 0.2 to 20.0 g / L, tin ions 0.01 to 2.0 g / L
g / L, containing 0.01 to 5.0 g / L of condensed phosphate ions and having a pH of 2 to 6 and a coating chemical conversion solution for metal surface treatment. It is capable of forming a phosphate film having excellent corrosion resistance and paint adhesion on the surface of a can. The oxyacid ion is an oxidizing agent and has a role of oxidizing and removing hydrogen generated by the anodic reaction.

However, when the present invention is actually used continuously, it is possible to perform good surface treatment at the initial stage, but tin ions and iron ions gradually eluted from the tinplate coexist with them. It was found that sludge consisting of phosphate was formed by reacting with phosphate ions. Iron ions elute from tinplate in a divalent state,
It is gradually oxidized by an oxidizing agent such as oxyacid ion and becomes trivalent in the surface treatment solution, and is present in the solution at about 0.05 g / L.
It became clear that this was the cause of sludge generation. This sludge adheres to the surface of the tinplate material, deteriorating the adhesion of the paint, and may cause a problem. In addition, since these sludges clog the pipes and nozzles of the spray device and prevent good surface treatment, there has been a problem of maintenance and quality instability of periodically cleaning the pipes and nozzles of the spray device. . In recent years, improvements in productivity and quality stability have been important issues, and surface treatment liquids that reduce the cleaning load and stabilize quality, that is, generate no sludge in the liquid even when used continuously, are desired. It is rare.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention solves the above-mentioned current problems, and provides a tinting material surface treatment solution and treatment capable of improving productivity such as quality stability and ease of maintenance. The aim is to provide a method.

[0006]

As a result of intensive studies on the above-mentioned conventional problems, it has become clear that the generation of sludge is greatly influenced by the state of iron ions (divalent / trivalent) eluted from the tinplate material. And, in the surface treatment solution for tinplate containing at least phosphate ion, chelating agent and tin ion, it has a hydrogen ion concentration in the range of pH 2.0 to 4.5, and the concentration of the chelating agent is 0.1. ~ 5.
0 g / L, containing oxidizing agent and ferric ion
By the tinting material surface treatment liquid characterized by not being
The inventors of the present invention have confirmed that they imparted excellent corrosion resistance and paint adhesion, and did not generate sludge even when they were continuously treated, thereby completing the present invention.

In the surface treatment method, iron ions eluted from a tinplate when a surface treatment solution is continuously used are often spontaneously oxidized to be trivalent. A tinting material obtained by contacting a tinting material with an acidic surface treatment solution containing at least a phosphate ion, a chelating agent, and a tin ion with the aim of maintaining iron ions in a divalent state by examining the potential to be grasped. In the surface treatment method, the hydrogen ion concentration (p
H) is in the range of 2.0 to 4.5, and the oxidation-reduction potential of the surface treatment liquid is adjusted to 45 by adding a reducing agent if necessary.
The present inventors have found a surface treatment method for tinplate, which is characterized by controlling it to 0 mV or less, and have completed the present invention. Hereinafter, the configuration of the present invention will be described.

[0008] Phosphoric acid (H ₃
PO ₄ ), sodium phosphate (Na ₃ PO ₄ ), and the like can be used, and the amount used is the amount required to cause the precipitation of tin phosphate. If the phosphate ion content is less than 1 g / L, the reactivity is poor and it is difficult to form a sufficient film under normal processing conditions. Even if the amount exceeds 30 g / L, a good film is formed.
Since the cost of the processing solution is high and there is an economic problem, its content is preferably in the range of 1 to 30 g / L, particularly 4 to 30 g / L.
A range of 8 g / L is preferred.

In the present invention, it is important that the solution contains a chelating agent in such an amount as to perform appropriate etching, selective formation of a chemical conversion film on the exposed iron portion, stabilization of tin ions, and the like. Preferred chelators suitable for this purpose include condensed phosphate ions, tartaric acid, oxalic acid, citric acid. Particularly preferred chelating agents are one or more selected from condensed phosphate ions.
The reason is that the condensed phosphate ion is gradually decomposed into phosphoric acid, and has little effect on wastewater treatment. To contain the condensed phosphate ion, its acid or salt can be used. For example, pyrophosphate (H ₄ P ₂ O ₇ ), sodium pyrophosphate (Na ₄ P ₂ O ₇ ), or the like can be used to contain pyrophosphate ions. If the chelating agent is less than 0.1 g / L, the etching action is weak and a film is not formed sufficiently. If the chelating agent exceeds 5 g / L, the etching action is too strong to inhibit the film forming reaction. The range is preferably from 1 to 5 g / L, particularly from 0.2 to 5 g / L.
A range of 1.0 g / L is preferred.

[0010] Since the tinned DI can has been subjected to DI processing, a tin-plated portion and an iron portion exposed by the processing coexist on the surface. Generally, the corrosion resistance is inferior when the iron exposed portion is large. Therefore, how to uniformly cover the exposed iron portion with the chemical conversion film is an important issue for improving the corrosion resistance. Since a chelating agent is added to the surface treatment liquid of the present invention, the exposed iron portion where the formation failure is remarkable when the chelating agent is not added is selectively and uniformly covered with the chemical conversion film. I have. For this reason, it is possible to obtain a chemical conversion film having excellent corrosion resistance. The chelating agent, particularly condensed phosphoric acid, also has the effect of stabilizing the eluted tin ions in the liquid and suppressing the generation of sludge.

In order to contain tin ions, metal tin and tin salts such as tin chloride can be used, but are not particularly limited. When the treatment is performed continuously, tin ions need not be replenished because tin ions elute from the tinplate. The tin ion content is selected to form a suitable tin phosphate film,
The range of 2.0 g / L is preferred, and especially 0.1 to 1.0 g.
/ L range is preferred. More preferably 0.2 to 0.6
The range of g / L is good. 0.01 g / L to 2.0 g above
In the range of / L, a film having excellent corrosion resistance is formed, and sludge deposition hardly occurs.

The pH of the treatment liquid is adjusted to 2.0 to 4.5, but if it is less than 2.0, etching will increase and it will be difficult to form a film. In the treatment liquid of the present invention, since the anodic reaction hardly proceeds due to the substantial absence of the oxidizing agent, when the pH exceeds 4.5, the anodic reaction conditions are greatly deteriorated, and a film having excellent corrosion resistance is formed. No longer. Therefore, the pH must be controlled in the range from 2.0 to 4.5. Preferably, the pH is in the range of 2.5-3.5, more preferably in the range of 2.7-3.3.
The pH is adjusted by using an acid such as phosphoric acid or sulfuric acid and an alkali such as sodium hydroxide, sodium carbonate or ammonium hydroxide.

The treatment liquid of the present invention comprises an oxidizing agent and ferric ion
Is not contained . Although the conventional surface treatment solution contained an oxidizing agent, the surface treatment solution of the present invention is an anodic agent.
Causes appreciable removal of hydrogen generated by the hydrogen reaction
Does not contain oxidizing agents such as oxyacid ions. The reason for this is that when an oxidizing agent is contained, divalent and trivalent iron ions coexist and sludge precipitates easily due to trivalent iron ions. Conventionally, it was thought that if the oxidizing agent was not present in the tinting material surface treatment liquid, the chemical conversion was unstable, and in particular, it was not possible to obtain a uniform chemical conversion on the exposed iron portion, which was considered undesirable. By controlling the pH, the pH and the concentration of the chelating agent within the above ranges, it became possible to continue the chemical conversion while maintaining a good chemical conversion film even if the oxidizing agent was not contained.

Further, an important point in the processing method of the present invention is to control the oxidation-reduction potential of the processing solution to 450 mV during the processing. The electrode used for measuring the oxidation-reduction potential is not particularly limited. In the present invention, a platinum electrode was used as a redox electrode and a silver chloride electrode was used as a reference electrode in order to define the potential. In this case, the oxidation-reduction potential is 4
If it is 50 mV or less, almost all iron ions are in a divalent state, and the generation of sludge is suppressed.

The ferrous ions in the treatment liquid are also oxidized by oxygen in the air in addition to the oxidizing agent. The susceptibility to oxidation of divalent iron ions varies depending on the conditions of the apparatus, spray conditions, and the like. The oxidation-reduction potential may exceed 450 mV when the present invention is used continuously under such processing conditions that air is easily entrained and the renewal of the surface treatment solution (removal of the inevitable solution depending on the treated product) is small. In such a case, sludge is generated and causes a problem in quality or maintenance of the apparatus. Therefore, it is important to add a reducing agent in advance or to add a reducing agent when the oxidation-reduction potential becomes high. This makes it possible to keep the oxidation-reduction potential at 450 mV or less. The reducing agent is not particularly limited, but those which inhibit the film forming property of the tinting material by the surface treatment liquid are not preferred. In this regard, since the surface treatment liquid contains phosphate ions as a main component, the reducing agent is preferably phosphorous acid or hypophosphorous acid. This is because phosphorous acid or hypophosphorous acid becomes phosphate ions after acting as a reducing agent, and there is no adverse effect due to accumulation of decomposition products.

To add phosphorous acid or hypophosphorous acid, its acid or salt can be used. The addition amount varies depending on the processing conditions, but is preferably smaller for economic reasons. That is, the oxidation-reduction potential is 450 mV
It is sufficient to contain or add the minimum amount to keep below. In other words, the amount of the reducing agent added can be controlled by the oxidation-reduction potential, and if the reducing agent is replenished so as to keep the oxidation-reduction potential at 450 mV or less, the iron ions are kept in a divalent state, Even if the treatment is performed for a long period of time, sludge can not be generated in the surface treatment liquid.

Next, the chemical conversion film to be formed will be outlined. In general, a chemical conversion film formed by a surface treatment liquid of a tinplate is mainly a phosphate mainly composed of tin phosphate, and the basic mechanism is the same in the present invention. That is, the tinplate base material is etched by the phosphate ions and the chelating agent, particularly the condensed phosphate ions, and at that time, a local pH rise occurs at the interface, and the phosphate conversion film mainly containing tin phosphate is formed on the surface. Precipitates out. The difference between the conventional phosphate film and that of the present invention is that the conventional film is formed by the coexistence of a chelating agent and an oxidizing agent, whereas the present invention uses a chelating agent and (if necessary) a reducing agent. In other words, the coexistence with the above means that iron ions are divalent only and are substantially not formed containing trivalent ferric ions. It is presumed to be small. “Sludge fogging” refers to a state in which a scum-like substance having somewhat poor adhesion adheres to the vicinity of the original tin phosphate-based film. The phosphate coating of tin-plated steel sheet is an extremely thin coating of about 10 to 20 angstroms in both tin-plated and exposed iron parts in the case of tin DI can. Unlike a zinc-based coating (about 1 to 10 g / m ² , 1000 to 8000 angstroms), sludge fogging cannot be determined visually, and the exact location has not yet been elucidated.

Next, an outline of a tinplate treatment process to which the surface treatment liquid of the present invention is applied will be described. The treatment liquid of the present invention is applied in a process described below as a preferred example.

Washing of tinplate: Degreasing (generally using a weak alkaline degreasing agent) Water washing Surface treatment (application of the treatment solution of the present invention) Treatment temperature: 30 to 70 ° C Treatment method: spray or immersion Treatment time: 2 to 40 seconds Rinse with water Deionized water dry

The treatment temperature of the surface treatment solution of the present invention is 30 to 7
0 ° C. is preferred. More preferably, it is usually used by heating to 40 to 60 ° C. Preferred processing time is 2-4
0 seconds. If it is less than 2 seconds, it does not react sufficiently, and a film having excellent corrosion resistance is not formed.
A range of ~ 40 seconds is appropriate

The treatment method can be either an immersion method or a spray method. As described above, the present invention exerts particularly excellent effects when used in a spray device.

[0022]

As described above, the generation of sludge largely depends on the state of iron ions eluted from the tinplate. The iron ions are eluted from the tinplate as divalent ferrous ions. In the processing solution of the present invention, iron ions during running are generally 0.0
It is present in the form of ferrous ions at a concentration of about 5 g / L, and no ferric ions are present. On the other hand, in the conventional processing solution, almost all ferrous ions are oxidized and exist in the form of ferric ions or colloids, and the concentration thereof is generally about 0.05 g / L. It is considered that ferric ion forms an insoluble salt with phosphate ion, and further, entrains coexisting tin ion and phosphate ion to cause sludge generation. That is, the generation of sludge in the surface treatment liquid can be suppressed by keeping the iron ions eluted from the tinting material divalent. In the present invention, by eliminating the presence of the oxidizing agent used in the conventional processing solution, ferric ions could be made to occupy almost all of the iron ions. Is 2 tin ions
This is considered to be due to the coexistence of valence and tetravalence, and divalent tin ions can rapidly reduce trivalent iron ions to divalent.

Generally, the oxidation-reduction potential is the equilibrium electrode potential of the oxidation-reduction electrode, and is an amount representing the strength of the oxidizing or reducing power of the solution. The oxidation-reduction potential corresponding to the oxidation reaction (Fe ²⁺ → Fe ³⁺ + e) from ferrous ions to ferric ions is expressed by the following equation. _{Ee = E 0 - (RT /} F) ln ([R] / [O]) wherein R is the gas constant, T is absolute temperature, F is Faraday - Constant, [R] and [O] is ferrous respectively Ion and second
The iron ion activity, E _0, is the standard electrode potential in this system. The larger the value of Ee, the stronger the oxidizing power and the ferric ion /
The ratio of ferrous ions increases. In other words, the lower the redox potential, the less ferric ion. Therefore, the state (divalent / trivalent) of the eluted iron ions can be qualitatively determined by the oxidation-reduction potential.

[0024]

EXAMPLES Several examples of the surface treating solution of the present invention are given below, and the usefulness thereof is shown in comparison with comparative examples. Tinplate is tinplated D made from tin plated steel sheet by DI processing.
I cans were used. Corrosion resistance after surface treatment is based on iron exposure (IE
V). In addition, IEV is measured by USPate
According to nt4332646. The lower the IEV value, the better the corrosion resistance. For paint adhesion, use epoxy urea-based can paint on the surface of the treated
7 μm, baked at 215 ° C. for 4 minutes,
It was cut into strips of 150 mm in size and thermocompressed with a polyamide-based film to obtain test pieces, which were peeled by a 180-degree peel test method, and evaluated from the peel strength at that time. Therefore, the higher the peel strength, the better the paint adhesion. Generally, it is good if the width is 1.5 kgf / 5 mm or more.

Further, generation of sludge was performed by adding 0.05 g / L (ferrous chloride) of iron ions to the surface treatment solutions shown in Examples and Comparative Examples, adjusting the pH after the addition, and allowing the solution to stand for 1 day. The state of the subsequent liquid was observed and evaluated. Those that are transparent and free of precipitates can be determined to contain no ferric ion . The oxidation-reduction potential after standing was measured using a platinum electrode as a redox electrode and a silver chloride electrode as a reference electrode.

Further, for the purpose of confirming the state of sludge generation during the continuous treatment, the surface treatment liquids shown in Examples and Comparative Examples were newly prepared and continuously treated. The amount of the processing solution in the continuous processing was 2 L, and a total of 360 cans were processed for 30 seconds. The amount of the solution was adjusted depending on the used surface treatment solution, and the pH was adjusted with phosphoric acid so as to maintain the initial value. The state of the liquid after the continuous test and the oxidation-reduction potential (ORP) were measured.
If the liquid is transparent and no sedimentation occurs, the liquid
It can be determined that no ON is contained. After the continuous treatment, the iron ion concentration during the treatment was measured by an atomic absorption method.
When a precipitate was generated, hydrochloric acid was added to dissolve the precipitate and the analysis was performed.

Example 1 Tin-plated tins made by tinning a tin-plated steel sheet were treated with a slightly alkaline degreasing agent (registered trademark, Fine Cleaner-448).
8, 1% heated aqueous solution of Nippon Parkerizing Co., Ltd.), and after that, the surface treatment liquid 1 was heated to 60 ° C., spray-treated for 20 seconds, and then washed with tap water, After spraying with deionized water of 3 MΩcm or more for 10 seconds, the film was dried in a hot air drying oven at 180 ° C. for 3 minutes.
Then, the corrosion resistance and coating film adhesion of the treated can were evaluated. Further, the sludge generation property of the surface treatment liquid 1 was evaluated. Surface treatment bath 1 75% phosphoric acid _{(H 3 PO 4) 10.0 g} / L (PO 4 3-: 7.2 g / L) sodium pyrophosphate _{(Na 4 P 2 O 7 ·} 10H 2 O) 1.0 g / L (P ^{_{2 O 7 4-: 0.4 g /}} L) tin _{(SnCl 4 · 5H 2 O)} 0.6 g / L (Sn 4+: 0.2 g / L) of iron _{(FeCl 3 · 6H 2 O)} 4.8mg / L (Fe 3 ^+: 1.0 mg / L) phosphorous acid _{(H 3 PO 3) 0.01g /} L (H 3 PO 3: 0.01g / L) adjusted at pH 3.0 (sodium carbonate) Note ferric chloride generation of sludge Was added to investigate the effect of trivalent iron ions on the amount of trivalent iron.

Example 2 After cleaning the tinplate DI can under the same conditions as in Example 1, the surface treatment liquid 2 was heated to 40 ° C. and sprayed for 10 seconds. After the treatment, it was washed with water and dried under the same conditions as in Example 1. Then, the corrosion resistance and coating film adhesion of the treated can were evaluated. In addition, sludge generation property of the surface treatment liquid 2 was evaluated. Surface treatment bath 2 75% phosphoric acid _{(H 3 PO 4) 5.0 g} / L (PO 4 3-: 3.6 g / L) sodium pyrophosphate _{(Na 4 P 2 O 7 ·} 10H 2 O) 2.0 g / L (P ^{_{2 O 7 4-: 0.8 g /}} L) tin _{(SnCl 4 · 5H 2 O)} 1.2 g / L (Sn 4+: 0.4 g / L) pH 2.8 ( adjusted with phosphoric acid)

Example 3 After cleaning the tinplate DI can under the same conditions as in Example 1, the surface treatment liquid 3 was heated to 60 ° C. and sprayed for 40 seconds. After the treatment, it was washed with water and dried under the same conditions as in Example 1. Then, the corrosion resistance and coating film adhesion of the treated can were evaluated. Further, the sludge generation property of the surface treatment liquid 3 was evaluated. Surface treatment bath 3 75% phosphoric acid _{(H 3 PO 4) 5.0 g} / L (PO 4 3-: 3.6 g / L) sodium pyrophosphate _{(Na 4 P 2 O 7 ·} 10H 2 O) 2.0 g / L (P ^{_{2 O 7 4-: 0.8 g /}} L) tin _{(SnCl 4 · 5H 2 O)} 0.01g / L (Sn 4-: 0.03g / L) hypophosphorous acid _{(H 3 PO 2) 0.01g /} L (H ₃ PO ₂ : 0.01g / L) pH 4.0 (adjusted with sodium hydroxide)

Example 4 After cleaning the tinplate DI can under the same conditions as in Example 1, the surface treatment liquid 4 was heated to 40 ° C. and sprayed for 10 seconds. After the treatment, it was washed with water and dried under the same conditions as in Example 1. Then, the corrosion resistance and coating film adhesion of the treated can were evaluated. Further, the sludge generation property of the surface treatment liquid 4 was evaluated. Surface treatment bath 4 75% phosphoric acid _{(H 3 PO 4) 15.0 g} / L (PO 4 3-: 10.8 g / L) sodium pyrophosphate _{(Na 4 P 2 O 7 ·} 10H 2 O) 2.0 g / L (P ^{_{2 O 7 4-: 0.8 g /}} L) sodium tripolyphosphate _{(Na 5 P 3 O 10)} 1.0 g / L (P 3 O 10 5-: 0.6 g / L) tin _{(SnCl 4 · 5H 2 O)} 1.2 g / L (Sn ⁴⁺ : 0.4 g / L) Phosphorous acid (H ₃ PO ₃ ) 0.01 g / L (H ₃ PO ₃ : 0.01 g / L) Hypophosphorous acid (H ₃ PO ₂ ) 0.01 g / L (H ₃ PO ₂ : 0.01 g / L) pH 3.0 (adjusted with sodium carbonate)

Example 5 After cleaning the tinplate DI can under the same conditions as in Example 1, the surface treatment liquid 5 was heated to 50 ° C. and sprayed for 30 seconds. After the treatment, it was washed with water and dried under the same conditions as in Example 1. Then, the corrosion resistance and coating film adhesion of the treated can were evaluated. In addition, sludge generation property of the surface treatment liquid 5 was evaluated. Surface treatment bath 5 75% phosphoric acid _{(H 3 PO 4) 1.0 g} / L (PO 4 3-: 0.7 g / L) sodium pyrophosphate _{(Na 4 P 2 O 7 ·} 10H 2 O) 2.0 g / L (P ^{_{2 O 7 4-: 0.8 g /}} L) tin _{(SnCl 4 · 5H 2 O)} 1.2 g / L (Sn 4+: 0.4 g / L) phosphorous acid _{(H 3 PO 3) 0.01g /} L (H 3 PO ₄ : 0.01g / L) pH 3.0 (adjusted with phosphoric acid)

Example 6 After cleaning the tinplate DI can under the same conditions as in Example 1, the surface treatment liquid 6 was heated to 50 ° C. and sprayed for 20 seconds. After the treatment, it was washed with water and dried under the same conditions as in Example 1. Then, the corrosion resistance and coating film adhesion of the treated can were evaluated. Further, sludge generation property of the surface treatment liquid 6 was evaluated. Surface treatment bath 6 75% phosphoric acid _{(H 3 PO 4) 5.0 g} / L (PO 4 3-: 3.6 g / L) sodium pyrophosphate _{(Na 4 P 2 O 7 ·} 10H 2 O) 2.0 g / L (P ₂ O ₇ ^4- : 0.8 g / L) Tin (dissolves metallic tin) 0.2 g / L (Sn ²⁺ : 0.2 g / L) Phosphorous acid (H ₃ PO ₃ ) 0.01 g / L (H ₃ PO ₃ : 0.01g / L) pH 3.0 (adjusted with phosphoric acid)

Example 7 After cleaning the tinplate DI can under the same conditions as in Example 1, the surface treatment liquid 7 was heated to 70 ° C. and sprayed for 2 seconds. After the treatment, it was washed with water and dried under the same conditions as in Example 1. Then, the corrosion resistance and coating film adhesion of the treated can were evaluated. Further, sludge generation property of the surface treatment liquid 7 was evaluated. Surface treatment solution 7 75% phosphoric acid (H ₃ PO ₄ ) 30.0 g / L (PO ₄ ³ : 21.6 g / L) Sodium pyrophosphate (Na ₄ P ₂ O ₇ .10H ₂ O) 2.0 g / L (P ^{_{2 O 7 4-: 0.8 g /}} L) sodium tripolyphosphate _{(Na 5 P 3 O 10)} 1.0 g / L (P 3 O 10 5-: 0.6 g / L) tin _{(SnCl 4 · 5H 2 O)} 1.2 g / L (Sn ⁴⁺ : 0.4 g / L) Phosphorous acid (H ₃ PO ₃ ) 0.01 g / L (H ₃ PO ₃ : 0.01 g / L) Hypophosphorous acid (H ₃ PO ₂ ) 0.01 g / L (H ₃ PO ₂ : 0.01g / L) pH 2.0 (adjusted with phosphoric acid)

Comparative Example 1 After cleaning the tinplate DI can under the same conditions as in Example 1, the surface treating solution 8 was heated to 40 ° C. and sprayed for 30 seconds. After the treatment, it was washed with water and dried under the same conditions as in Example 1. Then, the corrosion resistance and coating film adhesion of the treated can were evaluated. The sludge generation property of the surface treatment liquid 8 was evaluated. Surface treatment bath 8 75% phosphoric acid _{(H 3 PO 4) 10.0 g} / L (PO 4 3-: 7.2 g / L) Tin _{(SnCl 4 · 5H 2 O)} 0.6 g / L (Sn 4+: 0.2 g / L) Phosphorous acid (H ₃ PO ₃ ) 0.01 g / L (H ₃ PO ₃ : 0.01 g / L) pH 3.0 (adjusted with sodium carbonate)

Comparative Example 2 After cleaning the tinplate DI can under the same conditions as in Example 1, the surface treatment liquid 9 was heated to 50 ° C. and sprayed for 30 seconds. After the treatment, it was washed with water and dried under the same conditions as in Example 1. Then, the corrosion resistance and coating film adhesion of the treated can were evaluated. Further, sludge generation property of the surface treatment liquid 9 was evaluated. Surface treatment bath 9 75% phosphoric acid _{(H 3 PO 4) 10.0 g} / L (PO 4 3-: 7.2 g / L) sodium pyrophosphate _{(Na 4 P 2 O 7 ·} 10H 2 O) 1.0 g / L (P ^{_{2 O 7 4-: 0.4 g /}} L) tin _{(SnCl 4 · 5H 2 O)} 0.6 g / L (Sn 4+: 0.2 g / L) phosphorous acid _{(H 3 PO 3) 0.01g /} L (H 3 PO ₃ : 0.01g / L) pH 4.6 (adjusted with sodium hydroxide)

Comparative Example 3 After cleaning the tinplate DI can under the same conditions as in Example 1, the surface treatment liquid 10 was heated to 50 ° C. and sprayed for 30 seconds. After the treatment, it was washed with water and dried under the same conditions as in Example 1. And
The corrosion resistance and coating film adhesion of the treated can were evaluated. Further, the sludge generation property of the surface treatment liquid 10 was evaluated. Surface treatment bath 10 75% phosphoric acid _{(H 3 PO 4) 1.33g /} L (PO 4 3-: 0.9 7 g / L) sodium pyrophosphate _{(Na 4 P 2 O 7 ·} 10H 2 O) 1.0 g / L ( ^{_{P 2 O 7 4-: 0.4 g}} / L) tin _{(SnCl 4 · 5H 2 O)} 0.6 g / L (Sn 4+: 0.2 g / L) of iron _{(FeCl 3 · 6H 2 O)} 48 mg / L (Fe ³⁺ : 10 mg / L) pH 4.0 (adjusted with sodium carbonate)

COMPARATIVE EXAMPLE 4 After cleaning the tinplate DI can under the same conditions as in Example 1, a commercially available tinplate DI can surface treatment agent (palphos-K346) was used.
6 Nippon Parkerizing Co., Ltd.) was heated to 50 ° C. and sprayed for 30 seconds. After the treatment, it was washed with water and dried under the same conditions as in Example 1. Then, the corrosion resistance and coating film adhesion of the treated can were evaluated. In addition, sludge generation property of this treatment liquid was evaluated.

Comparative Example 5 A tinplate DI can was cleaned under the same conditions as in Example 1 and then a commercially available tinplate DI can surface treating agent (palphos-K348).
2 Nippon Parkerizing Co., Ltd.) was heated to 50 ° C. and sprayed for 30 seconds. After the treatment, it was washed with water and dried under the same conditions as in Example 1. Then, the corrosion resistance and coating film adhesion of the treated can were evaluated. In addition, sludge generation property of this treatment liquid was evaluated. Table 1 shows the results.

[0039]

[Table 1]

[0040]

As described above, tinplate is obtained by treating the surface of tinplate (tin-plated steel) plates and strips and the surface of this molded product (can, etc.) with the surface treatment liquid according to the present invention. Provides excellent corrosion resistance and adhesion to the material surface,
In addition, there is an excellent effect that sludge is not generated in the processing liquid when the processing is performed continuously.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 22/00-22/86

Claims (2)

(57) [Claims] 1. A tin material surface treatment liquid containing at least a phosphate ion, a chelating agent and a tin ion and forming a chemical conversion film mainly containing a phosphate, has a pH of 2.0 or more.
It has a hydrogen ion concentration in the range of 4.5, and the chelating agent is at least one selected from condensed phosphate ions, tartaric acid, oxalic acid and citric acid, and the concentration is 0.1 to 5.5.
0 g / L, and the oxidizing agent and ferric ion
A tinting material surface treatment liquid characterized by not containing . 2. A method for surface treatment of a tin material in which a phosphate-based chemical conversion film is formed on the surface of the tin material by contacting an acidic surface treatment solution containing at least a phosphate ion, a chelating agent and a tin ion. Wherein the hydrogen ion concentration (pH) of the surface treatment solution is in the range of 2.0 to 4.5 , and one or more reducing agents selected from phosphorous acid , hypophosphorous acid, and salts thereof are added. Thereby controlling the oxidation-reduction potential of the surface treatment liquid to 450 mV or less.