JP5919990B2 - Manufacturing method of surface-treated steel sheet - Google Patents

Description

  The present invention relates to a surface-treated steel sheet used mainly for containers such as cans after being coated with a resin film by laminating a resin film or the like on the surface or by applying a paint containing resin, particularly in a high-temperature and humid environment. The present invention relates to a method for producing a surface-treated steel sheet that has excellent adhesion to a resin coated in (hereinafter referred to as wet resin adhesion) and exhibits excellent corrosion resistance even when the coated resin is missing.

  Various metal cans such as beverage cans, food cans, pail cans and 18 liter cans use metal plates such as electrolytic chromic acid treated steel plates called tin-plated steel plates or tin-free steel plates. Among these, tin-free steel sheets are manufactured by electrolytically treating steel sheets in a plating bath containing hexavalent Cr, and are characterized by excellent wet resin adhesion to resins such as paints.

  In recent years, due to the increasing awareness of the environment, the use of hexavalent Cr has been regulated worldwide, and there is an alternative material for tin-free steel plates manufactured using a hexavalent Cr plating bath. It has been demanded.

  On the other hand, various types of metal cans have been manufactured by processing metal cans such as tin-free steel sheets and then processing them into cans. Instead of this, a method of processing a resin-coated metal plate coated with a resin such as a resin film into a can body is frequently used. In this resin-coated metal plate, it is necessary that the resin is strongly adhered to the metal plate. In particular, the resin-coated metal plate used as a beverage can or a food can is subjected to a retort sterilization process after filling the contents. Because there are cases where the resin does not peel off even in a high-humidity environment, even if the resin is partially lost due to scratching, the contents of the can are eroded and holes are opened. There is a demand for excellent corrosion resistance that does not occur.

  In response to such a request, the present inventors recently disclosed in Patent Document 1 a Ni layer, a Sn layer, a Fe—Ni alloy layer, a Fe—Sn alloy layer, and a Fe—Ni—Sn alloy layer on at least one surface of a steel plate. After forming a corrosion-resistant film consisting of at least one layer selected from the above, it contains ions containing Ti, and further contains at least one metal element selected from Co, Fe, Ni, V, Cu, Mn and Zn. It was proposed that a surface-treated steel sheet having excellent wet resin adhesion and excellent corrosion resistance can be produced without using Cr by forming an adhesive film by cathodic electrolysis in an aqueous solution containing ions.

JP 2009-155665 A

  However, in the method described in Patent Document 1, if an adhesive film is formed by continuous cathodic electrolysis in an aqueous solution containing Ti and Co, excellent wet resin adhesion may not be obtained.

  The present invention provides a Cr-free surface-treated steel sheet that can reliably provide excellent wet resin adhesion and corrosion resistance even when an adhesive film is formed by continuous cathodic electrolysis in an aqueous solution containing Ti and Co. It aims to provide a method.

  As a result of intensive studies on the above-described method for producing a surface-treated steel sheet, the present inventors have obtained an anode comprising a conductive substrate having a catalyst layer containing at least one of iridium oxide and ruthenium oxide on the surface. It was found that it is effective to use the cathode electrolytic treatment.

  The present invention has been made based on such knowledge, and at least one surface of a steel plate is selected from a Ni layer, a Sn layer, a Fe—Ni alloy layer, a Fe—Sn alloy layer, and a Fe—Ni—Sn alloy layer. After forming the at least one layer of the corrosion-resistant film, iridium oxide and ruthenium oxide are formed on the surface in an aqueous solution containing 0.008 to 0.07 mol / l (l: liter) of Ti and further containing 0.01 to 10 moles of Co with respect to Ti. There is provided a method for producing a surface-treated steel sheet, characterized in that an adhesive film is formed by cathodic electrolysis using an anode made of a conductive substrate having a catalyst layer containing at least one of the above.

In the production method of the present invention, the amount of Ti contained in the adhesive film is preferably 3 to 200 mg / m ² per side.

  By the manufacturing method of the present invention, even if the cathode electrolysis treatment is continuously carried out in an aqueous solution containing Ti and Co to form an adhesive film, a Cr-free surface treatment that ensures excellent wet resin adhesion and corrosion resistance can be obtained. Steel sheets can be manufactured. The surface-treated steel sheet produced by the production method of the present invention can be used as a substitute for conventional tin-free steel sheets without any problem and without being coated with a resin on a container containing oil, organic solvent, paint, or the like. Further, even if the resin is coated to form a resin-coated steel sheet, processed into a can or can lid and exposed to a retort atmosphere, the resin does not peel at all. Further, even in a resin missing portion such as a scratch, the dissolution of Fe as a base material is remarkably small, and the corrosion resistance is extremely excellent.

It is a figure explaining a 180 degree peel test.

1) Formation of corrosion-resistant film As a material, a low-carbon cold-rolled steel sheet for cans is used as a raw material. First, the steel sheet surface is first firmly bonded to the base steel sheet to form a resin-coated steel sheet. In order to give excellent corrosion resistance to the steel sheet even if the material is missing, a single layer of Ni layer, Sn layer, Fe-Ni alloy layer, Fe-Sn alloy layer and Fe-Ni-Sn alloy layer or a multilayer thereof can be used. A corrosion resistant film is formed. This corrosion-resistant film can be formed by a known method according to the contained metal element.

In the case of the Ni layer, the amount of Ni per one side of the steel sheet contained in the corrosion resistant film is preferably 200 mg / m ² or more. In the case of the Fe—Ni alloy layer, the amount of Ni per one side of the steel sheet contained in the corrosion resistant film is preferably 60 mg / m ² or more. In the case of the Sn layer or the Fe—Sn alloy layer, it is preferable that the Sn amount per one side of the steel sheet contained in the corrosion-resistant film is 100 mg / m ² or more. In the case of the Fe—Ni—Sn alloy layer, it is preferable that the amount of Ni per one side of the steel sheet contained in the corrosion-resistant film is 50 mg / m ² or more and the amount of Sn is 100 mg / m ² or more. Here, the measurement of the amount of Ni or Sn can be performed by surface analysis using fluorescent X-rays.

2) Formation of adhesion film Next, on this corrosion-resistant film, the surface is oxidized in an aqueous solution containing 0.008 to 0.07 mol / l (l: liter) of Ti and further containing 0.01 to 10 of Co in molar ratio to Ti. An adhesive coating is formed by cathodic electrolysis using an anode made of a conductive substrate having a catalyst layer containing at least one of iridium and ruthenium oxide.

  Using an aqueous solution containing 0.008 to 0.07 mol / l (l: liter) of Ti and further containing 0.01 to 10 of Co in a molar ratio with respect to Ti forms a dense adhesive film with uneven surface distribution more evenly. This is to obtain excellent wet resin adhesion. It should be noted that using an aqueous solution containing 0.1 to 2.5 mol of Ti in a molar ratio of Ti to 0.02 to 0.05 mol / l and Co to form a denser adhesive film with surface irregularities more evenly distributed. It is preferable for obtaining excellent wet resin adhesion.

  Further, cathodic electrolysis using an anode made of a conductive substrate having a catalyst layer containing at least one of iridium oxide and ruthenium oxide on the surface is aimed at a specific effect in the treatment liquid of the present invention. In order to prevent the wet resin adhesion from being deteriorated when the cathode electrolytic treatment is continuously performed to form the adhesive film. The cause is considered as follows. That is, when cathodic electrolysis is performed using a general lead electrode, platinum electrode, or anode having a platinum coating layer on a conductive substrate such as titanium, divalent cobalt ions are oxidized and trivalent at the anode. The potential to become cobalt ions is lower than the oxygen generation potential (eg, the oxygen generation potential of the anode coated with platinum on a titanium substrate is 2.1 V (vs. NHE), oxidation from divalent cobalt to trivalent cobalt) Since the potential is 1.95V (vs. NHE), the oxidation reaction of cobalt ions takes place preferentially. Trivalent cobalt ions generated by oxidation react with water to form solid cobalt oxyhydroxide, and as the electrolysis continues, a large number of them float in the solution. For this reason, solid matter of cobalt oxyhydroxide comes to adhere on the adhesive film, and the wet resin adhesion of the film deteriorates with time. However, when a catalyst layer containing at least one of iridium oxide and ruthenium oxide is provided on the surface of a conductive substrate such as titanium, the oxygen generation potential becomes lower than the oxidation potential of cobalt ions (eg, iridium oxide on the titanium substrate). The oxygen generation potential of the anode coated with A is 1.5 V (vs. NHE), and the oxidation potential from divalent cobalt to trivalent cobalt is 1.95 V (vs. NHE). For this reason, the current is consumed by the generation of oxygen, the production of trivalent cobalt ions and the reaction with water are delayed, and the production of cobalt oxyhydroxide is suppressed, resulting in continuous cathodic electrolysis treatment. Even so, excellent wet resin adhesion can be obtained.

  As the aqueous solution containing Ti, an aqueous solution containing fluorotitanate ions or an aqueous solution containing fluorotitanate ions and a fluorine salt is suitable. As the compound that gives fluorotitanate ions, fluorinated titanate, ammonium fluoride titanate, potassium fluoride titanate, and the like can be used. As the fluorine salt, sodium fluoride, potassium fluoride, silver fluoride, tin fluoride, or the like can be used. In particular, the method of cathodic electrolysis of a steel sheet after the formation of a corrosion-resistant film in an aqueous solution containing potassium fluoride titanate or an aqueous solution containing potassium fluoride titanate and sodium fluoride forms an efficient uniform film It is possible and preferable.

  In addition, cobalt sulfate, cobalt chloride, or the like can be used as a compound that gives Co.

In the cathodic electrolysis treatment, it is preferable that the current density is 5 to 20 A / dm ² and the electrolysis time is 1 to 10 seconds.

The amount of Ti contained in the adhesive film is preferably 3 to 200 mg / m ² per side. This is because when the amount of Ti is 3 mg / m ² or more, the effect of improving wet resin adhesion is sufficiently obtained, and when it exceeds 200 mg / m ² , further improvement in wet resin adhesion cannot be expected, resulting in high costs. . The Ti amount of the adhesive film can be controlled by the Ti concentration and pH in the aqueous solution, the current density during cathodic electrolysis, the amount of electricity, and the like.

  The amount of Co contained in the adhesive film needs to be 0.01 to 10, preferably 0.1 to 2.5 in terms of a mass ratio (Co / Ti) to Ti. This is because it is possible to form an adhesive film that is dense and has surface irregularities distributed more uniformly, and excellent wet resin adhesion can be obtained.

  The adhesive film preferably further contains O. This is because inclusion of O results in a film mainly composed of an oxide of Ti and contributes to wet resin adhesion.

  The amount of Ti or Co contained in the adhesive film can be measured by surface analysis using fluorescent X-rays. The amount of O is not particularly defined, but its presence can be confirmed by surface analysis using XPS (X-ray photoelectron spectroscopy analyzer).

  On such a surface-treated steel sheet produced by the method of the present invention, a resin film can be laminated to obtain a laminated steel sheet. As described above, since the surface-treated steel sheet produced by the method of the present invention has excellent wet resin adhesion, this laminated steel sheet has excellent corrosion resistance and workability.

  There is no limitation in particular as a resin film laminated on the surface treatment steel plate manufactured by the method of this invention, The film which consists of various thermoplastic resins and thermosetting resins can be mentioned. For example, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, olefin resin film such as ionomer, polyester film such as polybutylene terephthalate, or nylon 6 A non-stretched or biaxially stretched thermoplastic resin film such as a polyamide film such as nylon 6,6, nylon 11, or nylon 12, a polyvinyl chloride film, or a polyvinylidene chloride film can be used. When an adhesive is used in the lamination, a urethane adhesive, an epoxy adhesive, an acid-modified olefin resin adhesive, a copolyamide adhesive, a copolyester adhesive, or the like is preferable.

  Furthermore, modified epoxy paint such as phenol epoxy, amino-epoxy, vinyl chloride-vinyl acetate copolymer, saponified vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, epoxy-modified- , Epoxyamino modified-, Epoxyphenol modified-Vinyl or modified vinyl paint, Acrylic paint, Thermoplastic or thermosetting paint such as synthetic rubber paint such as styrene-butadiene copolymer. Can be used in combination.

  The thickness of the resin laminate layer is preferably 3 to 50 μm. This is because when the thickness is below the above range, the corrosion resistance becomes insufficient, and when the thickness is above the above range, problems are likely to occur in terms of workability.

  The resin laminate layer can be formed on the surface-treated steel sheet by any means. For example, it can be performed by an extrusion coating method, a cast film thermal bonding method, a biaxially stretched film thermal bonding method, or the like.

Using plating baths a and b shown in Table 1 on both sides of cold-rolled cold-rolled steel sheets (thickness 0.2 mm) as cold-rolled steel used for the production of tin-free steel sheets (TFS), A corrosion-resistant film is formed by the plating methods A to D.
A: The cold-rolled steel sheet, with _{10vol% H 2 + 90vol% N} 2 atmosphere, was annealed at about 700 ° C., after temper rolling elongation of 1.5%, and the alkaline electrolytic degreasing and acid pickling After the application, Ni plating treatment is performed using the plating bath a to form a corrosion-resistant film composed of a Ni layer.
B: The cold-rolled steel sheet was alkali electrolytic degreasing, was subjected to Ni plating using a plating bath a, with _{10vol% H 2 + 90vol% N} 2 atmosphere, it was annealed at about 700 ° C., a Ni plating spread After the permeation, temper rolling with an elongation of 1.5% is performed to form a corrosion-resistant film composed of a Fe—Ni alloy layer.
C: The cold-rolled steel sheet was alkali electrolytic degreasing, was subjected to Ni plating using a plating bath a, with _{10vol% H 2 + 90vol% N} 2 atmosphere, was annealed at about 700 ° C., cementation Ni plating After temper rolling with an elongation rate of 1.5%, degreasing, pickling, Sn plating treatment using the plating bath b, and heat melting treatment for heating and holding above the melting point of Sn are performed. By this treatment, a corrosion-resistant film composed of an Fe—Ni—Sn alloy layer and an upper Sn layer is formed.
D: Alkaline electrolytic degreasing of the cold-rolled steel sheet, annealing and temper rolling in the same manner as in Condition A, followed by Sn plating using the plating bath b, followed by a heat-melting treatment that heats and maintains the melting point of Sn or higher . By this treatment, a corrosion-resistant film composed of the Fe—Sn alloy layer and the upper Sn layer is formed.

  In the treatment of C and D, a part of Sn plating is alloyed by heat melting treatment.

  Next, on the corrosion-resistant film formed on both surfaces of the steel sheet, cathodic electrolysis is performed under the conditions of cathodic electrolysis shown in Tables 2 and 3, that is, aqueous solution composition, anode, and current density, and dried to form an adhesive film. Surface-treated steel plates No. 1 to 18 are produced. Surface-treated steel sheets No. 5, 8, 11, 16, 17, and 18 are comparative examples in which an adhesive film is formed on the surface using an anode that does not have the catalyst layer of the present invention.

  The amounts of Ni and Sn contained in the corrosion resistant coating and the amount of Ti contained in the adhesive coating are determined by fluorescent X-ray analysis in comparison with a calibration plate obtained by chemical analysis of the amount of adhesion in advance. In addition, the amount of Co contained in the adhesive film is determined by selecting an appropriate measurement method from the same fluorescent X-ray analysis method as that of Ti, and chemical analysis, Auger electron spectroscopy analysis and secondary ion mass spectrometry. The mass ratio of Co to Ti contained (Co / Ti) is evaluated. These results are shown in Tables 2 and 3. Moreover, O can confirm the presence by surface analysis by XPS about all the surface-treated steel plates No. 1-18.

In addition, on both surfaces of these surface-treated steel plates No. 1 to 18, a resin film using an isophthalic acid copolymer polyethylene terephthalate film having a draw ratio of 3.1 × 3.1, a thickness of 25 μm, a copolymerization ratio of 12 mol%, and a melting point of 224 ° C. Lamination conditions such that the BO value of the steel sheet is 150, that is, steel sheet feed rate: 40 m / min, rubber roll nip length: 17 mm, time after pressure bonding to water cooling: 1 second, laminated steel sheet No. 1-18 Is made. Here, the nip length is the length in the transport direction of the portion where the rubber roll and the steel plate are in contact. The BO value of the resin film is the X-ray diffraction intensity of the PET (100) plane observed in the vicinity of 2θ = 26 ° measured using a Cu tube as the X-ray source. And about the produced laminated steel plates No. 1-18, wet resin adhesiveness and corrosion resistance are evaluated by the following method. At this time, the wet resin adhesion is evaluated for the case where the adhesive film is produced immediately after the start of the electrolytic treatment and the case where it is produced after the continuous electrolytic treatment for 6 hours.
Wet resin adhesion: Wet resin adhesion is evaluated by a 180 ° peel test in a retort atmosphere at a temperature of 130 ° C. and a relative humidity of 100%. The 180 ° peel test is a test piece (size: 30 mm x 100 mm, with both sides on the front and back sides set to n = 1, leaving a film 2 as shown in Fig. 1 (a) and cutting out part 3 of the steel plate 1 , N = 2 for each laminated steel plate), as shown in Fig. 1 (b), attach a weight 4 (100g) to one end of the test piece, turn it 180 ° to the film 2 side, and leave it for 30 minutes This is a film peeling test. Then, the peel length 5 shown in (c) of FIG. 1 is measured and evaluated, and the average of the peel lengths (n = 2) on the front and back surfaces of each laminated steel sheet is obtained. The smaller the peel length 5 is, the better the wet resin adhesion is.If the peel value 5 is less than 10 mm when the BO value is 150, the excellent wet resin adhesion targeted by the present invention is obtained. evaluate.
Corrosion resistance: Cut the laminate surface of the laminated steel plate to reach the steel plate substrate using a cutter knife, and immerse it in 80 ml of a test solution in which 1.5% by mass NaCl aqueous solution and 1.5% by mass citric acid aqueous solution are mixed in equal amounts, 55 ° C And left for 9 days to evaluate the corrosion resistance of the cut part (where both the front and back surfaces are n = 1 and n = 2 for each laminated steel sheet) as follows. And
○: No corrosion at n = 2 ×: Corrosion at 1 or more of n = 2 Table 4 shows the results. In the laminated steel sheet No. 1 to 4, 6, 7, 9, 10, 12 to 15 which is an example of the present invention, both when the adhesive film is produced immediately after the start of the electrolytic treatment and when produced after the continuous electrolytic treatment for 6 hours, Excellent wet resin adhesion is obtained. On the other hand, in the laminated steel sheets No. 5, 8, 11, and 16 to 18 as comparative examples, excellent wet resin adhesion was obtained when the adhesive film was produced immediately after the start of electrolytic treatment, When prepared after time-continuous electrolytic treatment, wet resin adhesion is poor. In any laminated steel sheet, the corrosion resistance is excellent.

DESCRIPTION OF SYMBOLS 1 Steel plate 2 Film 3 Part cut out of steel plate 4 Weight 5 Peeling length

Claims (2)

  After forming a corrosion-resistant film consisting of at least one layer selected from Ni layer, Sn layer, Fe-Ni alloy layer, Fe-Sn alloy layer and Fe-Ni-Sn alloy layer on at least one surface of the steel plate, Ti is 0.008. From an electrically conductive substrate having a catalyst layer containing at least one of iridium oxide and ruthenium oxide on the surface in an aqueous solution containing ~ 0.07 mol / l (l: liter) and further containing Co in a molar ratio of 0.01 to 10 with respect to Ti A method for producing a surface-treated steel sheet, comprising forming an adhesion film by cathodic electrolysis using an anode. ^{2. The} method for producing a surface-treated steel sheet according to claim 1, wherein the amount of Ti contained in the adhesive film is 3 to 200 mg / m ² per side.

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