JPS6213594A - Steel sheet for sn-coated vessel having excellent property to be coated and corrosion resistance and its production - Google Patents

Abstract

PURPOSE:To develop a steel sheet for vessels having excellent property to be coated, corrosion resistance after coating, adhesion of the secondary paint and corrosion resistance of the end face by providing an Sn-coated layer on the rear surface of a Cr-contg. steel sheet, melting the layer by heating as required and then forming a chromate-coated film. CONSTITUTION:An Sn-coated layer is formed at >300mg/m<2> deposition quantity per one surface on a steel sheet contg. <0.15% C, 0.005-0.10% acid-soluble Al, 1.5-11% Cr or further 0.03-0.50% one or >=2 kinds among Ti, Nb, Zr and V by electroplating, melt plating, vacuum deposition, etc., to obtain a steel sheet for vessels such as a can. The sheet is heated at 300 deg.C which is the m.p. of Sn to melt the Sn layer to form an Fe-Sn alloy layer, if required. Then a chromate-coated film is formed thereon at 1.5-150mg/m<2> deposition quantity per one surface expressed in terms of metallic Cr.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention has excellent paintability, corrosion resistance after painting, paint adhesion after painting (so-called secondary paint adhesion), corrosion resistance, and corrosion resistance of end faces. This invention relates to a steel sheet for containers coated with a Sn coating layer.

(Prior art) As a steel plate for containers that is used after painting, JP-A-55-6
As disclosed in Publication No. 9297, there is an Sn-based coated steel sheet in which a chromate coating layer consisting of a two-layer coating composition of a metal Cr layer and a chromium oxide layer mainly composed of hydrated oxide is applied to a KSn plating layer.
Excellent paint adhesion and corrosion resistance after painting.

In addition, steel sheets with improved corrosion resistance of steel plates for containers having a Sn-based coating layer have an N1-based base coating layer as disclosed in, for example, JP-A No. 57-23091 or JP-A-60-5884. There is Sn-based coated steel sheet.

These steel plates have the superimposed effect of the base coating layer and the Sn coating layer,
This is intended to improve corrosion resistance by reducing exposed areas of the base metal due to the formation of a uniform and dense alloy layer due to the effect of the base coating layer.

Although the Sn-based coated steel plates for containers as described above are used in some places to take advantage of their properties, it is difficult to say that they have necessarily achieved sufficiently satisfactory paintability and corrosion resistance.

(Problem to be solved by the invention) In recent years, the characteristics of steel sheets for containers have improved in response to the diversification of can manufacturing methods and the consumer's preference for high-quality products. In order to cope with the thinning of steel sheets for containers in order to improve various performances or reduce can costs, there is a demand for better corrosion resistance (that is, an increase in corrosion resistance life).

For example, in response to the increasing number of deformed cans such as necked-in cans, it is desired to improve corrosion resistance after painting on parts that have undergone more severe processing than before, and to improve paint adhesion when stored for a long time. .

In addition, as a material for can lids, it is required to be easier to open than before, and in response to the reduction in the thickness of the can lid material and the thickness of the score processed part, we have improved corrosion resistance after painting of the processed part, and paint adhesion. At the same time, there is a need to improve the corrosion resistance, especially the rust resistance, of the large score sheared area where the iron surface is exposed on the outer surface of the can lid in the score processing area.

Furthermore, when an iron-based material is used for the tab of the easy-oven end can lid, corrosion resistance, especially rust resistance, of the end face of the material is required.

In addition, the crown is required to have improved rust resistance on the end face of the crown, improved corrosion resistance after painting of the processed portion of the crown, and improved paint adhesion.

Furthermore, in the welded can making method, further improvements are required in the corrosion resistance and paintability of the welded end face.

In addition, even if the coating layer (Sn coating layer, coating layer) is damaged due to the diversification of contents or processing such as deformed cans, there is little We elution from the steel base, and perforation corrosion occurs. There is a high demand for the development of materials with excellent corrosion resistance, corrosion resistance performance, and corrosion resistance life. As a result of various studies in response to these demands, the present inventors found that the above-mentioned conventional steel sheet for containers (so-called tin plate)
In this case, corrosion resistance improving elements are intentionally added to the plated original plate, and an aluminum killed steel plate is used.
Me.

It was found that the couple corrosion current between the layer and the plated original plate was extremely large.

As a result, in an atmosphere where there is almost no oxygen, such as inside a can, the plated original plate has a high corrosion rate due to the anodic dissolution of Sn. It was found that the film peeled off easily and corrosion progressed significantly from the area where the paint film was peeled off.

In addition, in a corrosive environment on the outer surface of the can, corrosion of the iron progresses due to 7-node melting of the iron at the end face of the sheared part of the plated original plate or the plating defect area, causing rust or perforation corrosion. It was also found that corrosion of the steel base causes rust and perforation corrosion in areas with painted eaves, reducing the corrosion resistance life.

Therefore, the present invention aims to solve these problems by adjusting the steel composition of the plated plate to improve the corrosion resistance of the plated plate itself, and to reduce the couple corrosion between the KSn-based coating layer and the plated plate. By reducing the current, it suppresses the dissolution of the Sn coating layer or base metal due to anode corrosion in a corrosive environment, and prevents the deterioration of paint adhesion and corrosion resistance in defective parts of the paint film after painting due to needle corrosion after painting. In addition, it is an object of the present invention to provide a high-performance steel plate for containers with a Sn coating layer, which prevents deterioration of corrosion resistance due to pitting corrosion in defective portions of the coating layer, and further prevents rust from forming on end surfaces and the like.

(Means for solving the problem) That is, the gist of the present invention is as follows: (1) Weight range: C: 0.151 or less, acid soluble Aj: 0.005 to 0
．． Section 10, Cr: A steel plate containing 1.5 to 11%, the balance consisting of iron and unavoidable impurities, a Sn coating layer with an adhesion amount of 30-0 η/m or more per side, and a metal Cr on the steel plate. The amount of adhesion per one side is 1.5 to 15011 in terms of quantity.
A steel sheet for Sn-coated containers with a chromate-based coating layer of 9/m" and excellent paintability and corrosion resistance.

, (2) Weight range: C: '0.151 or less, acid-soluble Al: 0.005~
0.10'14Cr; Contains 1-5 to 11 s, further IC'rl, Nb.

Zr e VO 1 type or 21!1 or more 0.03 to 0
．． 501, with the remainder being iron and unavoidable impurities, a Sn coating layer with an adhesion amount of 300 mg/m2 or more per side, and a Sn coating layer with an adhesion amount of 165 to 150 mg/m2 or more per side in terms of the amount of metal Cr. A 7t8n coated container steel plate with excellent paintability and corrosion resistance, coated with a mg/m2 chromate coating layer.

(3) In terms of weight range.

C: 0.154 or less, acid-soluble At; 0.005 to 0.
10, Cr: 1.5 to 111, with the remainder being iron and unavoidable impurities, the adhesion amount per side is 300
After applying a Sn coating layer of 11 mg/m2 or more, a heat melting treatment is performed, and then a chromate-based coating layer is applied with a coating amount of 1.5 to 15011197 m'' per side in terms of metal Cr amount. A method for manufacturing a Sn-based coated steel plate for containers with excellent paintability and corrosion resistance.

(4) Weight range: C; 0.154 or less, acid-soluble Al; 0.005 to 0
．． Contains 10%, Cr: 1.5-11%, and further contains 0.03-0.50% of one or more ↑1 Nb p Zre VO, and the remainder is iron and unavoidable The amount of adhesion per side on a steel plate made of impurities is 3008.
After applying a Sn coating layer of 97 m'' or more, a heat melting treatment is performed, and then the amount of deposited per side in terms of the amount of metal Cr is 1.
A method for producing a Sn-based coated steel sheet for containers with excellent paintability and corrosion resistance, characterized by applying a chromate-based coating layer of 5-150 aP/-.

It is in.

(effect) The details of the present invention will be explained below.

Continuous casting of molten steel made in melting furnaces such as converters and electric furnaces,
Or, it is made into a slab through ingot making and blooming method, hot rolling, cold rolling and annealing process, weight width is c; o, ls width is m.
Bottom, acid-soluble Al: 0.005-0.501A, Or
", 1.5 to 11%, with the remainder consisting of iron and unavoidable impurities. =? Master plate or TI on this.

Nb, Zr e V O 1 type or 2 or more types 0.03
A plating original plate containing ~0.5% is used.

In the corrosive environment in which Sn-coated steel sheets are used, S
The Cr content in the steel should be 1.51 or more, preferably 3 to improve corrosion resistance and paintability due to the combined effect with the n coating layer.
Person in charge or above.

Figure 1 shows the measured couple corrosion current between the Sn coating layer and the Cr-containing steel plate when the container is filled with a corrosion-promoting liquid.
Unfortunately, it is extremely small. On the other hand, Fig. 2 shows the measurement of the couple corrosion current between the Sn coating layer and the Cr-containing steel plate when the outer surface of the container was not immersed in the corrosion promoting solution.The couple corrosion current decreased as the Cr content increased. As a result, in conventional steel sheets that contain Cr as an unavoidable impurity, the kaggle corrosion current between the Sn coating layer is extremely large at defects in the coating layer and during processing. S
Dissolution becomes significant due to the sacrificial anticorrosive action of the n coating layer. Therefore, the present invention attempts to prevent the corrosion resistance life from being reduced due to the dissolution of the Sn coating layer by adding Cr to the steel.

Furthermore, even in a corrosive environment on the outer surface of the container, the corrosion rate of the bare metal exposed at the end face of the coating layer and the defective areas described above is significant, causing red rust and perforation corrosion, which significantly reduces the corrosion resistance life of the Sn-coated steel sheet. , can be prevented by using a Cr-containing steel plate such as the one of the present invention.

As described above, when the steel is coated and used, the deterioration of the corrosion resistance life is caused by defects in the coating film that reach the base metal during processing and transportation, or at the end faces of the coating layer.

In other words, in a corrosive environment such as the inner surface of a container where the anode dissolution due to the sacrificial anticorrosion effect of Sn is significant, the dissolution of Sn and the production of corrosion products will cause paint film blisters (so-called blisters), and if the paint film remains in the corrosive environment for a long time. When exposed to such substances, the coating film performance deteriorates due to factors such as the tendency to peel off the coating film. In addition, the Sn coating layer is a cathode (noble), but in a corrosive environment where the anodic dissolution of the base metal is significant, it is unlikely to cause deterioration of the coating performance, but it will significantly accelerate perforation corrosion from the defective parts of the exposed base metal. , which deteriorates the corrosion resistance after coating. Such performance deterioration after painting can be prevented by using a plated base plate of Cr-containing steel.

In general, no matter how strict the control is in manufacturing Sn-coated steel sheets, it is difficult to completely eliminate defects in the coating layer such as ginkholes and non-coating, and the coating may reach the base steel due to the formation of processed parts during use. Layer defects are generated. At the same time,
There are many situations where the end face of the Sn-coated steel plate is exposed to the base metal surface (for example, the welded part of a welded can, the scored part of a can lid, the end face of a crown, etc.).

Therefore, the present invention uses a steel sheet containing Cr as an essential component, which significantly reduces the couple corrosion current between the Sn coating layer and the plated original plate, to improve the plating defects, end faces, and Sn coating layer of the Sn coated steel plate. Dissolution rate is significantly suppressed. As a result, an Sn-based coated steel sheet having an excellent corrosion-resistant life at a temperature of 0.degree.

The octopus effect improves the adhesion of the coating over time or the corrosion resistance after coating, even when the coating is used after coating.

On the other hand, the Sn coating layer is potentially more noble (
[Cathode] In the case of plating defects, end faces, etc., it gives priority to the base metal and significantly suppresses the corrosion rate. the result,
It suppresses the occurrence of perforation corrosion and red rust on exposed parts of the base metal, and has a significant effect of extending the corrosion-resistant life. Furthermore, when used as a coating, it suppresses pitting corrosion, suppresses the formation of corrosion products on the base metal, prevents coating peeling, and significantly improves coating adhesion and post-coating corrosion resistance.

As mentioned above, the Cr content for obtaining such an effect is 1.5 to 11%, preferably 3 to 9%. If the Cr content is less than 1.5, the effect of reducing the kaggle corrosion current between the Sn coating layer and the plated original plate cannot be obtained,
Moreover, the effect of improving the corrosion resistance of the plated original plate itself cannot be obtained.

On the other hand, when the Cr content exceeds 114, the effect of improving the corrosion resistance of the plated original plate itself further increases, but the effect of reducing the kaggle corrosion current with the Sn coating layer may not be obtained depending on the corrosive environment, and the It becomes difficult to obtain sufficiently good adhesion, and weldability and workability deteriorate.

As mentioned above, the addition of CF has a great effect in terms of corrosion resistance and coating performance, but in the present invention, C and acid-soluble k1. The content of other ingredients is also limited. As C content increases, precipitation of chromium carbide increases, which deteriorates the mechanical properties and corrosion resistance of steel.
This inhibits the uniform coverage of the Sn-based coating layer.

Therefore, the C content is 0.151 or less, preferably 0.1
04 or less.

In addition, in the present invention, when adding TI, Nb, etc., the C content is preferably 0.02 or less because it inhibits workability and uniform coverage of the coating layer due to precipitation of titanium carbide and the like.

kA is the acid-soluble kL (8oL Al
) If the content is less than o or oos, it is difficult to prevent the formation of bubbles due to oxidizing gas, which significantly increases the incidence of surface defects in steel and becomes the starting point for deterioration of the corrosion resistance of steel materials. . In addition, excess acid-soluble kA exceeding 0.10% is At
The system oxides are scattered on the steel surface, which causes deterioration of corrosion resistance or causes non-plating, holes, etc. on the surface of the coating layer applied to the steel sheet, impairing the integrity of the coating layer.

Therefore, in the present invention, acid-soluble a is o, oos~0
．． 1 width, preferably 0.01 to 0.08 mm.

In addition to the above-mentioned steel components, the present invention also includes ICTl and Nb.

Zr e V 0.03 to 0.5 with 01 type or 2 or more types
By including 0% of Cr, Cr is combined with C in the steel to make the contained Cr more effective, further improving workability and corrosion resistance.

If the content of steel components such as T1 is less than 0.03%, there is little effect in preventing the precipitation of chromium carbide and improving workability and corrosion resistance, and the content is less than 0.03%.
If it exceeds this, the effect will reach saturation and become uneconomical, and the precipitation of these components will cause the material to become hard.
It tends to deteriorate workability. The preferred content is 0.0
75 to 0.201.

If a steel plate composed of the above-mentioned composition components is used as is, it has superior corrosion resistance compared to conventional steel plates that contain unavoidable impurities such as Cr, but the corrosion resistance is not sufficient as a material for containers. No, no. That is, iron is eluted due to organic acids, moisture containing Ct- ions, etc. contained in the container, and red rust is also significantly generated. In addition, the outer surface of the container is exposed to a corrosive atmosphere containing Ct"" ions and high temperatures.

When stored in high humidity conditions, red rust occurs in a relatively short period of time, and steel plates alone do not have sufficient corrosion resistance. Furthermore, even if the steel plate is directly painted, if it is exposed to a corrosive atmosphere for a long period of time, the corrosive aqueous solution that has penetrated under the coating will generate corrosion products on the steel plate, causing the coating to peel off and impairing the coating performance. deteriorate.

Therefore, in the present invention, a Sn coating layer and a chromate coating layer are applied to the plated original plate in order to impart the corrosion resistance and coating performance required for container materials.

When a 3N coating layer is applied to a steel sheet containing Cr as an essential component, as described above, the coupled corrosion current between the Sn coating layer and the plated original plate is significantly reduced.

As described above, this effect significantly improves the corrosion resistance of the plated original plate and the combined effect with the Sn coating layer, thereby significantly improving the corrosion resistance life and coating performance in a corrosive environment.

The Sn coating method to obtain this performance improvement effect is not particularly stipulated, and after cleaning and activating the steel plate surface, the Sn coating layer is formed by electroplating, hot-dip plating, vacuum evaporation, etc. administer.

For example, in the electroplating method, a ferrostane bath,
A Sn coating layer is applied to both sides of the steel plate in a desired amount by cathodic electrolysis using a borofluoride bath, a borofluoride bath, or the like.

The amount of Sn coating layer adhered is 300 per side.
11197 m" or more. In other words, if the amount of Sn coating layer is less than 300 cm/-2, uniform coverage will be lacking, unplated holes will occur, and the bond between the plated original plate and the Sn coating layer will be increased. Even if the corrosion current becomes smaller, it is difficult to prevent the melting of the base steel because the area where the Sn coating layer can provide anodic corrosion protection on the inner surface of the container is limited.Also, if the Sn coating layer Even in a harsh corrosive atmosphere, there are many exposed parts of the steel base, which promotes anodic corrosion protection of the base steel, increases the amount of dissolved steel, and increases the risk of pitting corrosion.

Therefore, the amount of Sn coating layer is 300 per side.
q/m" or more, preferably 700 ml/m- or more. Particularly, when the Sn adhesion amount is 70011197 m" or more, the end face produced by processing is covered by the force sagging of the 8N coating layer. It is particularly preferred because it further enhances the anti-corrosion effect on end faces such as sheared surfaces and processed surfaces.

Further, the upper limit of the amount of the Sn coating layer is not particularly defined, but from the point of view of economy, a coating amount of 151/ln" or less, preferably 511/m" or less is sufficient.

Furthermore, in the present invention, in order to further improve the performance, after providing the Sn coating layer, the melting point of Sn (231 ° C.
) The Sn coating layer is heated and melted at a temperature of 300° C., preferably 240 to 280° C. from directly above. With this treatment,
Due to the alloying reaction between the plated original plate and the Sn coating layer, Fs
-A Sn-based alloy layer is generated as an intermediate layer between the main plate and the Sn coating layer, and the pinholes in the Sn coating layer are further reduced, so the Sn coating layer is dissolved by Sn anodic corrosion protection or the corrosive atmosphere of the Sn cathode Iron dissolution from the plated original plate is further suppressed, and the corrosion resistance life of the Sn-coated steel sheet is further improved. This heating and melting treatment is not particularly specified, and may be the same as the conventional heating and melting treatment method for Sn-plated steel sheets.

For example, heating and melting treatment can be performed for a short time of 0.3 to 3 seconds at a heating temperature of 240 to 280°C in a N2 gas atmosphere, a MIX gas atmosphere, an aqueous solution of phenolsulfonic acid Sn, or a phenolsulfonic acid Sn. The coating is carried out in the air or in the above-mentioned atmosphere by applying an aqueous solution of phytic acid, an aqueous solution of ZnCL2, or the like as a flux. Furthermore, in the present invention, a chromate-based coating layer is applied to prevent yellowing during storage and improve coating performance. The amount of the chromate coating layer is regulated depending on its use and purpose, but for all purposes, the amount of chromate coating layer should be set within the range of 1.5 to 150 mg/m2 per side in terms of the amount of Cr metal. .

That is, 1.511497 m from preventing yellowing during storage.
If it is more than 1.5 mg/m2, it is sufficient, and if it is less than 1.5 mg/m2, S
The uniform coverage of the surface of the n-coating layer is insufficient, and it is difficult to prevent yellowing during storage due to the combined effect of the oil applied afterwards.

In addition, in order to ensure performance after painting, it is necessary to further improve the chromate coating effect on the surface of the Sn coating layer, and the amount of chromate coating should be 1.5 fmg/m2 or more, preferably 7.5 rn9/m “That’s it.

That is, when the thickness of the chromate coating layer is 1.51119/m'' or more, the uniform coverage of the chromate coating is improved, and the adhesion of the paint to the surface of the Sn coating layer is further ensured through the chromate coating.

On the other hand, the upper limit of the amount of chromate film is 150 mg/m2 or less, preferably 50 rn9/m" or less. If the amount of chromate film exceeds 150 η/m, the above-mentioned effect will be saturated. Cracks will form on the surface and cause galling.

In addition, regarding chromate coating, improvement of coating performance,
A chromate coating layer consisting of a metallic Cr layer and a chromium oxide layer mainly composed of water-conserving oxides is effective in improving paint adhesion over time and post-painting corrosion resistance when exposed to a 11FK corrosive environment for a long period of time. The chromate film with this film structure is made of metal Cr.
The layer has an adhesion amount of 1 to 30 mp/m'' per side, and the chromium oxide layer, which is mainly composed of water-use oxide, has a chromium oxide layer of 5 to 5 mp/m in terms of the amount of metal Cr.
A range of 0 mg/m2 is preferred. The method for forming this chromate film layer is not particularly specified, but chromic acid, chromate, dichromate containing Cr" ions, and an aqueous solution containing SO4 ions and heptadide are used. Then, immersion treatment or cathodic electrolysis treatment is performed.For example, Na2Cr2O7 aqueous solution, CrO5-po
4. Chromate treatment with a hydrated chromium oxide layer as the main component is performed by immersion treatment in an aqueous solution or cathodic electrolysis treatment.

(9) When providing a chromate coating consisting of a metal Cr layer and a chromium oxide layer mainly composed of hydrated oxide, CrO3
-804-2 series bath, Cry, -Na□5iF6- N
It is provided by cathodic electrolytic treatment using an H4F bath with adjusted current density.

The chromate film treatment for improving coating performance is applied to the products of the present invention after processing (for example, after DI molding).
(Similar effects can be obtained when surface cleaning treatment is performed.

(Example) Examples of the present invention will be described below.

Using steel sheets with steel components whose Cr content was mainly varied as shown in Table 1, 0.00% of a surfactant was added to a 34b NaOH aqueous solution.
After degreasing using a degreasing bath containing 31 and washing with water, 201 H2 was added.
Current density 20A/dl at 50℃ using So4 aqueous solution
After cleaning and activating the surface by performing anodic pickling for 1 second at n'', followed by cathodic pickling for 1 second and water washing,
The Sn-based coating layer and chromate coating treatment layer shown in Table 1 were provided, and various performance evaluation tests were conducted.

The performance evaluation was carried out using the following methods, and the performance evaluation results are shown in Table 1.

As a result, the product of the present invention has better coating performance than comparative materials.
It has extremely excellent corrosion resistance, rust resistance on the end surface, etc., and has extremely excellent properties as a material for containers.

O evaluation test method ■ Corrosion resistance targeting defects in coating layer Use 0.25 x 50 x 501 ml of evaluation material - 1 Seal the end and back surfaces, and make scratches reaching the base metal on the evaluation surface (1,51 citric acid + 1 .55b NaCj)
An immersion test was carried out in an aqueous solution of 400 g at a temperature of 50°C for 288 hours in an atmosphere of nitrogen gas with almost no oxygen present.
Elution amount and scratch eave area After the evaluation test, the corrosion resistance was evaluated based on the state of perforation corrosion in the eaves area, which was investigated using a cross-sectional microscope.

The evaluation criteria were as follows.

■ F・Elution amount・Evaluation Δ°= 5ppm or more ~ 7.5
Less than ppm
Drilling corrosion resistance/evaluation ◎... Maximum drilling corrosion depth from the scratched part is less than 25 times the plate thickness O... 254 or more ~ 40
Less than width Δ... 40 units or more
Less than 60 ×... The maximum drilling corrosion depth from the scratched part is 604 or more of the plate thickness ■ Scratch that targets the coating layer defect and reaches the base steel using the same evaluation material as 9 Corrosion Resistance ■.

After making the scratches, an immersion test was conducted in an aqueous solution of 1,01 citric acid + 0,25 phosphoric acid at 50°C for 288 hours in an N2 gas aeration atmosphere with almost no oxygen present. , (2) The amount of F elution was measured and the state of corrosion caused by drilling from the scratch eaves was investigated, and the corrosion resistance was evaluated.

Please note that the evaluation criteria is based on method ■.

■Evaluation of end face■ After shearing the evaluation material with a thickness of 0.25 wm, the end face was frozen (-15°C - 30 min) → high temperature and high humidity (temperature 49°C, humidity ≧98).

60mln)-*Evaluation was carried out by observing the number of cycles at which rust occurs on the sheared surface, with one cycle being left indoors (2 hours at 30°C).

In addition, the evaluation criteria were based on the following method.

◎...Rust occurs in 5 cycles or more O...Rust occurs in 4 cycles or more Δ...l Rust occurs in 3 cycles or more ×... Appears in 2 cycles or less [F] Plate thickness Using the evaluation material of 0.25-1, a 44φ x 81-depth evaluation material was created by de-drawing with a force of -1, and with the sheared surface located at the bottom, an extra-layer exposure test was conducted to remove red rust from the end surface. The occurrence situation was observed and the corrosion resistance was evaluated.

The evaluation criteria were based on the following method.

◎□・・・Rust occurred in an exposure test for 7 days or more O...
・ Occurred in an exposure test for 5 days or more and within 6 days ~ Δ... # 4 days or more and within 5 days 1
X---# Occurred during an exposure test within 3 days ■ Performance evaluation targeting defective parts of the paint film ■ After coating the evaluation material with epoxy phenol paint to a thickness of 5 μm, apply it to the base steel. Insert scratches reaching (1.5m)
Citric acid +1. ．． 51NaCA) in an aqueous solution at 27°C.
After a % time immersion test in a CO2 vented atmosphere with almost no oxygen, it dries immediately and becomes cellophane tea! After peeling, the performance of the coating film over time on the inner surface of the container was evaluated by examining the peeling status of the coating film from defective areas, mainly scratch areas.

In addition, the evaluation criteria were based on the following method.

◎...Almost no peeling of the paint film was observed at the scratch area.

○... Slightly observed.

Δ... Clearly recognized.

×... Remarkably recognized.

■ Paint film performance evaluation After coating the evaluation material with Zn-free pigmented dixy phenol paint to a thickness of 5.5μ, it was applied to the substrate for 1 day x 1.
100 squares of one-sided substrate were prepared, and after a 240-hour immersion test in a 1.5 cicitric acid aqueous solution at 27°C in an N2 aeration atmosphere with almost no oxygen, the cellophane chips were immediately peeled off after drying. The performance of the coating film after time was evaluated based on the condition of the coating film on the inner surface of the container.

In addition, the evaluation criteria were based on the following method.

◎... Paint film peeling area less than 5 inches ○... More than 5 inches - less than 10% Δ...
104 or more - less than 20c6×...
20 or more ■ Performance evaluation board thickness for score processing part of can lid material 0
．． Using a 21m evaluation material, the score remaining thickness was 75μ.
Sea-open can lid processing is performed, the inner surface is sealed, and in an oxygen atmosphere (1,51 citric acid + l,
Performance evaluation was performed after a 120 hour immersion test at 50'C in a 54 NaCt) aqueous solution.

■ Paint film performance evaluation After the above evaluation test, immediately after drying, cellophane tea! After peeling, the coating film performance after time was evaluated by an accelerated test on the outer surface of the container based on the peeling status of the coating film.

In addition, the evaluation criteria were based on the following method.

◎・・・The peeled area of the paint film is 0.40 mainly around the score processed area
Less than m ○... 0.40w or more ~ less than 0.60 electric Δ...
0.60 m or more to less than 1.0 area The corrosion resistance was investigated using a spatula.

In addition, the evaluation criteria were based on the following method.

◎・・・Maximum drilling corrosion depth is 2 (less than 1 ○
... 204 or more - less than 40 inches Δ... 40% or more - 60
'Less than 1 ×... 6
0 or more■ Evaluation of formability Using the evaluation material with a plate thickness of 0.28, perform cylindrical drawing to a depth of 60 m from a blank size of 150 mφ, and examine the occurrence of cracks and galling of the outer coating layer. A relative comparison was made between each evaluation material to evaluate its moldability.

In addition, the evaluation criteria were based on the following method.

◎・・・Very good ○...Good Δ...inferior ×...Very poor

[Brief explanation of drawings]

Figure 1 shows the relationship between the amount of Cr added in the steel and the contents of the can between the Sn coating layer and the couple corrosion current (1.5 tons of citric acid, 021・■ atmosphere, 8 m coating layer anode). Figure 2 shows the couple corrosion current (14NaSO4
+ 0.35'6 NaCt aqueous solution, oxygen saturation, F+
FIG. Agent Teruo Taniyama・,j −1〜,,J Koji Shinbu゛Cr Liaokaryo)−

Claims (4)

[Claims] (1) A steel sheet containing C: 0.15% or less, acid-soluble Al: 0.005 to 0.10%, Cr: 1.5 to 11%, with the balance consisting of iron and unavoidable impurities. , a Sn coating layer with an adhesion amount of 300 mg/m^2 or more per side, and on top of that an adhesion amount of 1.5 per side in terms of the amount of metal Cr.
A Sn-based coated steel sheet for containers with excellent paintability and corrosion resistance, characterized by being coated with a chromate-based coating layer of ~150 mg/m^2. (2) In weight%, C: 0.15% or less, acid-soluble Al: 0.005 to 0.10%, Cr: 1.5 to 11%, one or two of Ti, Nb, Zr, and V 0.03 to more than species
A steel plate containing 0.50% and the remainder consisting of iron and unavoidable impurities,
A Sn coating layer with an adhesion amount of 300 mg/m^2 or more per side, and a Sn coating layer with an adhesion amount of 1.0 mg/m^2 or more on one side in terms of the amount of metal Cr.
A Sn-based coated steel sheet for containers, which has excellent paintability and corrosion resistance, and is characterized by being coated with a chromate-based coating layer of 5 to 150 mg/m^2. (3) In weight percent, C: 0.15% or less, acid-soluble Al: 0.005 to 0.10%, Cr: 1.5 to 11%, the balance being iron and unavoidable impurities per side of the steel plate. After applying a Sn coating layer with an adhesion amount of 300 mg/m^2 or more, heat melting treatment is performed, followed by a chromate-based coating layer with an adhesion amount of 1.5 to 150 mg/m^2 per side in terms of metal Cr amount. A method for manufacturing a Sn-based coated steel sheet for containers, which has excellent paintability and corrosion resistance, and is characterized by applying a coating layer. (4) In weight%, C: 0.15% or less, acid-soluble Al: 0.005 to 0.10%, Cr: 1.5 to 11%, one or two of Ti, Nb, Zr, and V 0.03 to more than species
After applying a Sn coating layer with an adhesion amount of 300 mg/m^2 or more per side to a steel plate containing 0.50% Sn and the balance consisting of iron and unavoidable impurities, a heating melting process is performed, followed by a metal coating. Cr
The amount of adhesion per one side is 1.5 to 150 mg/m^
2. A method for manufacturing a Sn-based coated steel sheet for containers, which has excellent paintability and corrosion resistance, and is characterized by applying a chromate-based coating layer.