Method for producing aluminum having surface-treated film

Abstract

To prevent an object from being contaminated with iodine-specific color or odor even when the object is brought into contact with aluminum which has an oxide film formed on its surface, with fine pores or fine irregularities of the oxide film being impregnated with iodine or an iodine compound.SOLUTION: A method for producing aluminum having a surface-treated film comprises: an anodizing process for forming an oxide film having fine pores or recesses on the surface of aluminum; an iodine impregnation process for impregnating the fine pores or recesses of the oxide film with iodine or an iodine compound; and a decolorization and deodorization process, following the iodine impregnation process, for reducing the diffusion of the color and odor of the iodine or iodine compound.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] An embodiment of the present invention relates to a method for producing aluminum having a surface treatment film. [Background technology]

[0002] The process of forming an oxide film on the surface of aluminum using electrolytes such as sulfuric acid electrolyte or oxalic acid electrolyte is known as anodizing. The aluminum oxide (Al2O3) itself formed on the surface of aluminum as an oxide film is also often called anodizing. The main purposes of anodizing are to improve corrosion resistance, color, provide lubricity and wear resistance, and provide electrical insulation.

[0003] When aluminum is anodized, fine holes or irregularities are generated on the surface. For this reason, a sealing treatment is usually performed after the anodization treatment to close the fine holes or irregularities. Representative sealing treatments include pressurized steam sealing, which seals holes using pressurized steam in a high-pressure vessel, boiling water sealing, which seals holes in boiling water, and nickel acetate sealing, which seals holes in an aqueous solution of nickel acetate.

[0004] Also, a technique is known in which iodine or an iodine compound is impregnated into the fine pores or irregularities formed in the oxide film of a metal containing aluminum to impart bactericidal and antibacterial properties (see, for example, Patent Document 1). As a practical example, after anodizing aluminum, a material having bactericidal and antibacterial properties can be produced by impregnating the fine pores of the oxide film with polyvinylpyrrolidone iodide (PVPI), an iodine compound that is easily available, by electrophoretic deposition. PVPI is also known as povidone iodine.

[0005] The technique described in Patent Document 1 is a technique that does not perform a sealing treatment after impregnation with PVPI, i.e., a technique that forms a film structure in which PVPI is exposed to the outside. This is because if a sealing treatment is performed after impregnation with PVPI, the PVPI, which exerts bactericidal and antibacterial properties immediately after the sealing treatment, is trapped in the micropores or microscopic irregularities of the oxide film, whereas if a sealing treatment is performed using a conventional sealing agent, iodine dissolves into the sealing agent, causing discoloration.

[0006] In view of this, a technique has been proposed in which a sealing treatment is performed so that the PVPI is partially exposed after the PVPI is impregnated (see, for example, Patent Document 2). The method described in Patent Document 2 involves immersion dyeing of PVPI mixed with a dye into micropores or microscopic irregularities in an oxide film, or impregnation of PVPI by electrophoretic deposition, followed by at least a low-temperature sealing treatment and, if necessary, a high-temperature sealing treatment.

[0007] The low-temperature sealing treatment is a sealing treatment in which a substrate on which an oxide film has been formed is immersed in a low-temperature sealing solution mainly composed of nickel fluoride or nickel acetate, thereby partially closing the micropores or microscopic irregularities to the extent that PVPI can at least vaporize and diffuse, while the high-temperature sealing treatment is a sealing treatment that completely closes the micropores or microscopic irregularities to the extent that there is no vaporization or diffusion of PVPI. It is believed that sealing treatments that include at least the low-temperature sealing treatment can suppress the vaporization of PVPI and exhibit weather resistance.

[0008] In addition, Patent Document 2 describes that mixing PVPI into a sealant causes PVPI to diffuse not only from within the micropores or microscopic irregularities but also from the film-like sealing portion. Therefore, even when a high-temperature sealing treatment is performed, PVPI diffuses from the film-like sealing portion, and after the film-like sealing portion wears away, the PVPI diffuses from within the micropores or microscopic irregularities, thereby continuously exerting bactericidal and antibacterial properties.

[0009] Other known methods include coloring with an organic dye or electrolytic coloring prior to impregnation of the fine pores or fine irregularities of an oxide film with an iodine compound by electrophoretic deposition (see, for example, Patent Document 3), and using trimethylsulfoxonium iodide (TMSOI) or trimethylsulfonium iodide (TMSI) as an iodine compound (see, for example, Patent Documents 4 to 6).

[0010] It is understood that in the method described in Patent Document 3, no sealing treatment is performed after impregnation with the iodine compound, whereas in the methods described in Patent Documents 4 to 6, it is possible to perform a sealing treatment using a sealing agent, a sealing treatment using hot water at 80°C or higher without using a sealing agent, and a treatment in which the oxide film is immersed in an aqueous iodine compound solution at 85°C or higher to perform both the impregnation with the iodine compound and the sealing treatment. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2000-054194 A [Patent Document 2] JP 2005-350741 A [Patent Document 3] JP 2001-169996 A [Patent Document 4] JP 2012-197481 A [Patent Document 5] JP 2012-197482 A [Patent Document 6] JP 2014-047380 A Summary of the Invention [Problem to be solved by the invention]

[0012] As described above, when aluminum having an oxide film formed on its surface and having iodine or an iodine compound impregnated into the micropores or micro-irregularities of the oxide film is brought into contact with an object, the reddish-brown color of iodine may adhere to the object. That is, the reddish-brown color specific to iodine may fade. In addition, not only may the odor of iodine be generated, but the odor of iodine may be transferred to the object. As a result, there is a problem that it is difficult to construct a container, vessel, or the like using aluminum having an oxide film formed on its surface and having iodine or an iodine compound impregnated into the micropores or micro-irregularities of the oxide film.

[0013] In response to this, it has been proposed that sealing with a low-temperature sealing solution containing nickel fluoride or nickel acetate as the main component can reduce the adhesion of the iodine color to the object or the transfer of the iodine odor to the object, but there is a problem that nickel and nickel oxide are reported to be harmful to the human body or are at least suspected to be harmful to the human body. Therefore, when there is a need to not use nickel, such as in medical instruments, sealing with a sealing solution cannot be performed.

[0014] On the other hand, the iodine compounds TMSOI and TMSI are very expensive compared to PVPI, so it is desirable to use PVPI, which is easily available, as the iodine compound.

[0015] Therefore, an object of the present invention is to make it difficult for the color and odor peculiar to iodine or iodine compounds to adhere to an object even when the object is brought into contact with aluminum having an oxide film formed on its surface and having iodine or an iodine compound impregnated into the micropores or microscopic irregularities of the oxide film, regardless of the type of iodine compound.

[0016] Another object of the present invention is to realize, without using nickel, an object that is unlikely to acquire the color or odor characteristic of iodine or iodine compounds even when the object is brought into contact with aluminum having an oxide film formed on its surface and having iodine or an iodine compound impregnated into the micropores or microscopic irregularities of the oxide film, regardless of the type of iodine compound. [Means for solving the problem]

[0017] A method for producing aluminum having a surface treatment film according to an embodiment of the present invention includes anodizing treatment for forming an oxide film having fine pores or recesses on the surface of the aluminum, an iodine impregnation treatment for impregnating the fine pores or recesses of the oxide film with iodine or an iodine compound, and a decolorization and deodorization treatment for reducing the diffusion of the color and odor of the iodine or iodine compound after the iodine impregnation treatment. [Brief description of the drawings]

[0018] [Figure 1] 1 is a flowchart showing the steps of a method for producing aluminum having a surface treatment film according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a detailed structure of aluminum having a surface treatment film produced by the production method shown in FIG. 1. [Diagram 3] 2 is a table showing the relationship between the temperature of the electrolyte in the anodizing treatment shown in FIG. 1 and the state of the surface treatment film. [Figure 4] 2 is a table showing the relationship between the current application time, the sealing method, and the state of the surface treatment film in the iodine impregnation treatment shown in FIG. 1. [Diagram 5] 5 is a flowchart showing the steps of a method for producing aluminum having a surface treatment film according to a second embodiment of the present invention. [Figure 6] 6 is a table comparing the state of the surface treatment film after hot water sealing shown in FIG. 5 with the state of the surface treatment film after other sealing treatments. [Figure 7] 6 is a table showing the relationship between the hot water sealing treatment time shown in FIG. 5 and the state of the surface treatment film. [Figure 8] 5 is a flowchart showing the steps of a method for producing aluminum having a surface treatment film according to a third embodiment of the present invention. [Figure 9] 10 is a flowchart showing the steps of a method for producing aluminum having a surface treatment film according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A method for producing aluminum having a surface treatment film according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0020] (First embodiment) FIG. 1 is a flow chart showing the steps of a method for producing aluminum having a surface treatment film according to a first embodiment of the present invention.

[0021] As shown in FIG. 1, the method for producing aluminum having a surface treatment film includes step P1, which performs a pretreatment process, step P2, which performs anodizing (anodizing) process, step P3, which performs an iodine impregnation process by electrophoretic deposition, step P4, which performs a sealing process, and step P5, which performs a drying process.

[0022] In the pretreatment in step P1, known treatments such as degreasing, etching, and desmutting are carried out. Degreasing is a treatment in which oil is removed by cleaning the aluminum surface with a solvent, alkali, acid, or the like. Etching is a treatment in which an alkaline solution such as a sodium hydroxide solution is used to dissolve the aluminum surface, thereby removing scratches and removing oil remaining after the degreasing treatment. Desmutting is a treatment in which residues remaining on the aluminum surface during etching are removed with a nitric acid solution, or the like. Other pretreatments that may be used include chemical polishing and chemical matte finishing.

[0023] The anodizing treatment in step P2 is a treatment to form an oxide film having fine holes or recesses on the surface of aluminum by electrolysis. Specifically, the aluminum is immersed in an acidic aqueous solution to serve as an anode, and an oxide film is formed on the surface of the aluminum by passing an electric current through it.

[0024] The anodizing treatment in step P2 is carried out in a sulfuric acid solution having a temperature of 5°C or higher and 15°C or lower and a sulfuric acid concentration of 15 wt% or higher and 25 wt% or lower, so as to form an oxide film having a thickness of 10 μm or higher and 50 μm or lower.

[0025] The iodine impregnation treatment in step P3 is a treatment in which iodine or an iodine compound is impregnated into minute holes or recesses in the oxide film by electrophoretic deposition of iodine or an iodine compound. Therefore, the anodization treatment in step P2 corresponds to the primary electrolytic treatment, and the iodine impregnation treatment in step P3 corresponds to the secondary electrolytic treatment.

[0026] A representative example of an easily available iodine compound is PVPI, but electrophoresis may be performed using TMSOI, TMSI, other iodine compounds, or even iodine alone. Depending on the type of iodine compound, only iodine may be electrodeposited into the fine holes or recesses of the oxide film, or the iodine compound may be electrodeposited into the fine holes or recesses of the oxide film.

[0027] The iodine impregnation treatment in step P3 is performed by applying an electrolysis voltage of 30 V to 110 V to a solution of iodine or an iodine compound in which the iodine content is 1.0 wt % to 5.0 wt %, for an electrolysis time of 1 minute to 5 minutes.

[0028] The sealing treatment in step P4 is a treatment to close fine holes or recesses in the oxide film after the iodine impregnation treatment. Typical types of sealing treatment include pressurized steam sealing, boiling water sealing, and nickel salt sealing, but pressurized steam sealing is not used. This is because tests have confirmed that pressurized steam sealing causes iodine to leak from fine holes or recesses in the oxide film, resulting in unevenness.

[0029] When a sealing treatment is performed using a method other than pressurized steam sealing, the fine holes or recesses in the oxide film are not completely blocked, but are only partially blocked. The degree to which the fine holes or recesses in the oxide film are blocked is evaluated using the degree of sealing as an index. There are several sealing tests for determining the degree of sealing, such as a dye drop test, a phosphoric acid-chromic acid aqueous solution immersion test, and an admittance measurement test, and the value of the degree of sealing varies with each sealing test.

[0030] If a sealing method with a high degree of sealing is adopted, it leads to improvement of the corrosion resistance of the oxide film, which is the original purpose of the sealing treatment. On the other hand, if a sealing method with a low degree of sealing is adopted, the amount of iodine leaking from the minute holes or recesses of the incompletely blocked oxide film increases, leading to improvement of the bactericidal and antibacterial effects of iodine. Therefore, a sealing method can be selected according to the properties required for aluminum having a surface treatment film.

[0031] Nickel salt sealing is a sealing treatment that closes fine holes or recesses by immersing the oxide film in a sealing liquid whose main component is a nickel salt such as nickel fluoride or nickel acetate. As a representative example, when the sealing treatment is performed in a sealing liquid consisting of an aqueous solution of nickel acetate, the temperature of the sealing liquid is typically set to 95°C or higher, and the oxide film is immersed in the sealing liquid for about 10 to 20 minutes.

[0032] In addition, a sealing treatment using a cobalt salt such as cobalt acetate as a metal salt sealant other than nickel salt is also known. By using nickel salt sealant such as nickel acetate or cobalt salt sealant, the bactericidal and antibacterial effects of nickel or cobalt can be obtained in addition to the bactericidal and antibacterial effects of iodine.

[0033] Boiling water sealing is a sealing process that closes minute holes or recesses by immersing an oxide film in hot water of 80°C or higher, typically hot water of 95°C to 100°C. If boiling water sealing is used, the surface treatment film of aluminum after the sealing process will not contain nickel elements. Therefore, if boiling water sealing is used, it becomes possible to use aluminum with a surface treatment film as a material for medical instruments and medical parts that cannot use nickel, which is suspected to be harmful to the human body.

[0034] Conversely, the sealing degree by metal salt sealing such as nickel salt sealing is higher than that by boiling water sealing, so metal salt sealing may be used when emphasis is placed on the corrosion resistance of aluminum having a surface treatment film.

[0035] After anodizing and iodine impregnation were performed under the above-mentioned conditions, the sealing degree was measured in an admittance measurement test for the cases where only nickel salt sealing was performed and only boiling water sealing was performed. The admittance measurement test is a sealing degree test in which the measured value of admittance in the oxide film is the sealing degree. The unit of the measured value of admittance is siemens [S], which is the reciprocal ([S] = [1 / Ω]) of ohm [Ω], which is the unit of electrical resistance (resistance) and impedance.

[0036] The admittance measurement test results showed that the sealing degree was 20.0 μS when nickel salt sealing was performed for 5 minutes, and 30.0 μS when boiling water sealing was performed in 85°C hot water for 5 minutes. The smaller the measured value [S] of the sealing degree measured by the admittance measurement test, the higher the sealing degree [%]. For example, when pressurized steam sealing was performed, which gives the highest sealing degree, the sealing degree reaches nearly 0 μS. Therefore, the admittance measurement test results also confirm that the sealing degree [%] by nickel salt sealing is higher than the sealing degree [%] by boiling water sealing.

[0037] As a sealing treatment, a two-stage sealing process in which different sealing processes are performed twice is also known. Therefore, when it is particularly desired to improve the sealing degree and corrosion resistance, metal salt sealing such as nickel acetate sealing may be performed first, followed by boiling water sealing.

[0038] After the sealing process in step P4 is completed, the surface of the oxide film is washed with pure water, and then natural drying or hot air drying is performed in the subsequent step P5.

[0039] Next, a detailed structure of the aluminum having the surface treatment film produced by the above-mentioned production method will be described.

[0040] FIG. 2 is a schematic diagram showing a detailed structure of the aluminum plate 2 having the surface treatment film 1 produced by the production method shown in FIG.

[0041] As shown in Fig. 2, a surface treatment film 1 is formed on the surface of aluminum 2, which is a base material. The surface treatment film 1 has a structure including an oxide film 4 having fine pores or recesses 3, iodine or an iodine compound 5 impregnated in the fine pores or recesses 3, and a sealing layer 6 precipitated in the vicinity of the openings of the fine pores or recesses 3.

[0042] Typically, as illustrated in Fig. 2, it is believed that a large number of fine blind holes 3 are formed in the oxide film 4, each of which has a U-shaped cross section and whose central axes and depth directions are generally perpendicular to the surface of the oxide film 4. It is believed that iodine or an iodine compound 5 precipitates on the inner surface of the blind hole 3. On the other hand, it is believed that most of the sealing layer 6 precipitates from the inner surface of the blind hole 3 toward the central axis of the blind hole 3, mainly near the opening of the blind hole 3.

[0043] However, depending on the conditions of the anodizing treatment, it is considered that a large number of fine recesses having a V-shaped or similar shape in cross section and with a central axis and depth direction generally perpendicular to the surface of the oxide film 4 may be formed in the oxide film 4. Even in this case, it is considered that iodine or iodine compounds 5 are precipitated on the inner surface of the recesses, and most of the sealing layer 6 is precipitated from the inner surface of the recesses toward the central axis of the recesses, mainly near the openings of the recesses.

[0044] Even if the oxide film 4 is subjected to a sealing treatment, the degree of sealing will not be 100% unless pressurized steam sealing is performed. That is, the oxide film 4 is not completely sealed, but is in a partially sealed state. Specifically, the minute holes or recesses 3 are incompletely closed by the sealing layer 6. In other words, minute gaps narrower than the openings of the minute holes or recesses 3 remain in the sealing layer 6, and the size of the minute gaps corresponds to the degree of sealing.

[0045] Therefore, iodine or iodine compounds 5 pass through the minute gaps in the sealing layer 6 and diffuse to the outside of the surface treatment film 1. As a result, a bactericidal effect and an antibacterial effect can be obtained by the iodine or iodine compounds 5 leaking from the minute holes or recesses 3. Thus, at least a part of a container such as a vessel or a box can be formed from the aluminum 2 having the surface treatment film 1. In other words, the aluminum 2 having the surface treatment film 1 can be used as a material for the container.

[0046] The composition of the sealing layer 6 varies depending on the type of sealing treatment. For example, when nickel salt sealing is performed, one or both of nickel and nickel salt are precipitated as the sealing layer 6. On the other hand, when boiling water sealing is performed, boehmite (Al2O3·H2O) is formed as the sealing layer 6.

[0047] (effect) FIG. 3 is a table showing the relationship between the temperature of the electrolyte in the anodizing treatment shown in FIG. 1 and the state of the surface treatment film.

[0048] The table in Figure 3 shows the state of the surface treatment film when aluminum is anodized in a sulfuric acid solution with a concentration of 20 wt% to form an oxide film with a thickness of 30 μm, and then iodine is electrophoretically deposited by applying a voltage for 3 minutes to a PVPI solution with an iodine content of 3.0 wt%.

[0049] As shown in the table of Fig. 3, the electrolyte temperature in the anodizing treatment performed as the primary electrolysis and the electrolysis voltage in the electrophoretic deposition of iodine performed as the secondary electrolysis were changed to examine the state of the oxide film, the state of iodine deposition, and the amount of iodine deposition. More specifically, the electrolyte temperature in the anodizing treatment was changed from 5°C to 30°C in 5°C increments. Meanwhile, the electrolysis voltage in the electrophoretic deposition was set to 30V, 50V, 80V, and 100V. In the table of Fig. 3, ◯ indicates that the quality is good, △ indicates that the quality is within the acceptable range, and × indicates that the quality is outside the acceptable range.

[0050] As a result of the surface treatment test, it was found that when the temperature of the electrolyte in the anodizing treatment exceeds 15°C, an excessive amount of iodine is deposited by electrophoretic deposition of iodine. In addition, it was found that the excessive deposition of iodine leads to an undesirable deposition state of iodine, such as unevenness. If the amount of iodine deposition is excessive, the color and smell of iodine will adhere to objects that come into contact with or are brought close to the surface of the surface treatment film.

[0051] Therefore, when anodizing is performed to form an oxide film having a thickness of 10 μm to 50 μm in an electrolyte solution of sulfuric acid with a sulfuric acid concentration of 15 wt% to 25 wt%, excessive precipitation of iodine can be avoided by setting the electrolysis temperature to 5° C. to 15° C. As a result, it is possible to avoid or reduce the color and odor of iodine from adhering to an object that comes into contact with or is brought close to the surface of the surface treatment film. This is also considered to be the case when iodine compounds are precipitated.

[0052] In addition, as shown in the table of Fig. 3, when the electrolysis temperature in the anodizing treatment is 5°C to 15°C, it was found that the appropriate range of the electrolysis voltage in performing the electrophoretic deposition of iodine as the iodine impregnation treatment is 30 V to 110 V in order to avoid excessive deposition of iodine. This is also considered to be the same when iodine compounds are deposited.

[0053] FIG. 4 is a table showing the relationship between the current application time, the sealing method, and the state of the surface treatment film in the iodine impregnation treatment shown in FIG.

[0054] The table in Figure 4 shows the state of the surface treatment film when aluminum is anodized in a sulfuric acid solution with a concentration of 20 wt% at a liquid temperature of 10°C to form an oxide film with a thickness of 30 μm, and then a voltage of 100 V is applied to a PVPI solution with an iodine content of 3.0 wt% to perform electrophoretic deposition of iodine.

[0055] As shown in the table of Figure 4, the current flow time during electrophoretic deposition of iodine, which is performed as secondary electrolysis, and the sealing method after electrophoretic deposition of iodine were changed to examine the state of the surface treatment film. More specifically, the current flow time during electrophoretic deposition of iodine was set to 1 minute, 3 minutes, 5 minutes, and 10 minutes. Meanwhile, the state of the surface treatment film was examined by performing sealing treatments using nickel salt sealing, boiling water sealing using hot water at 85°C, and warm water sealing using warm water at 75°C, as well as without sealing treatment.

[0056] The condition of the surface treatment film was evaluated based on the color tone or appearance of the film surface immediately after electrophoretic deposition of iodine and before sealing treatment, as well as the state of iodine elution, the degree of powdering, the degree of discoloration, and the degree of iodine odor after sealing treatment or without sealing treatment. In the table of Figure 4, ◯ indicates good quality, △ indicates quality within the acceptable range, and × indicates quality outside the acceptable range. The evaluation results for the unsealed cases represent the evaluation results after washing with pure water at room temperature to remove impurities.

[0057] As a result of the surface treatment test, even if the electrolysis time during electrophoretic deposition of iodine was extended beyond 5 minutes, no increase in the amount of effective iodine deposition was confirmed. In other words, even if a voltage of 100 V was applied to a PVPI solution for more than 5 minutes, no change in color due to iodine was confirmed, and only an increase in the excessive deposition of iodine was observed.

[0058] Therefore, when electrophoretic deposition of iodine or iodine compounds is performed by applying an electrolysis voltage of 30 V to 110 V to a solution of iodine or iodine compounds with an iodine content of 1.0 wt% to 5.0% as an iodine impregnation treatment, it is appropriate to apply the electrolysis voltage for an electrolysis time of 1 minute to 5 minutes from the viewpoint of avoiding excessive deposition of iodine. In other words, if the current application time of the secondary electrolysis treatment is set to 1 minute to 5 minutes, it is possible to avoid or reduce the color and odor of iodine from adhering to objects that are in contact with or close to the surface of the surface treatment film. This is also considered to be the case when iodine compounds are deposited.

[0059] On the other hand, for the sealing method, the surface treatment state changes if the sealing conditions, such as the type of nickel salt, the sealing time, and the sealing temperature, are changed. That is, the table in FIG. 4 shows the results of a surface treatment test when sealing is performed under certain sealing conditions and methods. For this reason, depending on the sealing conditions, the surface treatment test results will not necessarily be as shown in the table in FIG. 4. Therefore, by determining an appropriate sealing method and sealing conditions that correspond to the required quality, it is possible to produce aluminum having a surface treatment film that meets the required quality.

[0060] As described above, by appropriately setting the electrolytic treatment conditions for the anodization of aluminum as the primary electrolytic treatment and the electrophoretic deposition of iodine or iodine compounds as the secondary electrolytic treatment as shown in Fig. 1, it is possible to reduce the brown discoloration and odor characteristic of iodine or iodine compounds. As a result, it is possible to reduce or avoid the attachment of color and odor to objects while exerting the bactericidal and antibacterial effects of iodine or iodine compounds.

[0061] Furthermore, it becomes possible to use aluminum having a surface treatment film produced by the above-mentioned manufacturing method as a material for containers such as vessels and boxes in which adhesion of color and odor to stored items must be avoided. In other words, when a container is made of aluminum having a surface treatment film produced by the above-mentioned manufacturing method, it is possible to reduce or avoid adhesion of color and odor from the container to objects stored in the container.

[0062] Second embodiment FIG. 5 is a flow chart showing the steps of a method for producing aluminum having a surface treatment film according to the second embodiment of the present invention.

[0063] 5 differs from the method for producing aluminum having a surface treatment film in the first embodiment in that the conditions for the anodizing treatment and the iodine impregnation treatment are not limited, and instead the sealing treatment is limited to hot water sealing. The other steps in the method for producing aluminum having a surface treatment film in the second embodiment are not substantially different from the method for producing aluminum having a surface treatment film in the first embodiment, so the same steps are denoted by the same reference numerals and description thereof will be omitted.

[0064] In the second embodiment, in step P2', anodizing is performed in the same manner as in step P2 in the first embodiment, but anodizing may be performed in an acidic aqueous solution of chromic acid, phosphoric acid, oxalic acid, or the like in addition to sulfuric acid. Therefore, the electrolytic treatment conditions may be changed as appropriate. However, if anodizing of aluminum is performed under the same electrolytic treatment conditions as in step P2 in the first embodiment, it is possible to more effectively prevent or reduce the color and odor of iodine from adhering to an object that comes into contact with or is brought close to the surface of the surface treatment film.

[0065] In step P3' in the second embodiment, iodine impregnation is performed in the same manner as in step P3 in the first embodiment, but the method is not limited to electrophoretic deposition of iodine or an iodine compound, and the iodine impregnation may be performed by immersion in a solution containing PVPI such as iodine or an iodine compound. However, if electrophoretic deposition of iodine or an iodine compound is performed under electrolytic treatment conditions similar to those in step P3 in the first embodiment, it is possible to more effectively prevent or reduce the adhesion of the color and odor of iodine to objects that come into contact with or are brought close to the surface of the surface treatment film.

[0066] In step P4' of the second embodiment, a pore sealing treatment is performed similarly to step P4 of the first embodiment, but hot water sealing is performed as the pore sealing treatment. The hot water sealing is a pore sealing treatment using hot water of 60°C or more and less than 80°C.

[0067] Like boiling water sealing, hot water sealing is a sealing treatment that does not use metal salts such as nickel salts or cobalt salts, and therefore, by performing hot water sealing, safety to the human body can be ensured. In other words, aluminum having a surface treatment film can be made nickel-free. As a result, aluminum having a surface treatment film can be used as a material for medical instruments and containers, which require safety to the human body in particular.

[0068] As a result of the surface treatment test, as shown in the table of FIG. 4 mentioned in the first embodiment, it was found that when boiling water sealing is performed as the sealing treatment, depending on the conditions of the electrophoretic deposition of iodine or an iodine compound, iodine, which is a bactericidal and antibacterial component, may be eluted, resulting in an appearance with a non-uniform pattern or precipitation of powdery substances.

[0069] In contrast, as shown in the table of Figure 4, it was found that hot water sealing not only avoids problems such as uneven appearance and powdering that occur when boiling water sealing is performed, but also makes it difficult to remove the color and odor of iodine or iodine compounds. Therefore, although the sealing degree of hot water sealing is smaller than that of boiling water sealing, hot water sealing not only reduces uneven appearance and powder deposition, but also prevents or reduces the adhesion of the color and odor of iodine or iodine compounds to objects that come into contact with or are brought close to the surface of the surface treatment film. In short, it can be said that hot water sealing is a sealing treatment that is compatible with iodine impregnation treatment.

[0070] FIG. 6 is a table comparing the state of the surface treatment film after hot water sealing shown in FIG. 5 with the state of the surface treatment film after other sealing treatments.

[0071] The table in Figure 6 shows an example in which, in step P2', aluminum is anodized in a sulfuric acid solution with a concentration of 20 wt% at a liquid temperature of 10°C to form an oxide film with a thickness of 30 μm, and then, in step P3', a voltage of 100 V is applied for 3 minutes to a PVPI solution with an iodine content of 3.0 wt% to perform electrophoretic deposition of iodine, and then, in step P4', hot water sealing is performed. The state of the surface treatment film obtained is compared with cases in which boiling water sealing and nickel salt sealing are performed.

[0072] More specifically, as shown in the table of Figure 6, boiling water sealing using 90°C hot water, boiling water sealing using 85°C hot water, boiling water sealing using 80°C hot water, warm water sealing using 75°C warm water, and nickel salt sealing were performed to examine the state of the surface treatment film. The state of the surface treatment film was evaluated in terms of the state of iodine elution, the degree of powdering, the degree of discoloration, and the degree of iodine odor after 12 hours. In the table of Figure 6, ◯ indicates good quality, △ indicates quality within the acceptable range, and × indicates quality outside the acceptable range.

[0073] As shown in the table in Figure 6, the results of surface treatment tests including sealing tests showed that powdering occurred when nickel salt sealing was performed and when boiling water sealing was performed using hot water of 85°C or higher. It was also found that the lower the temperature of the pure water used in the sealing treatment, the more the iodine odor can be reduced. This means that even if the sealing degree of the oxide film is low, the amount of leakage of the color and odor of iodine or iodine compounds does not increase to an observable extent. However, if the temperature of the pure water is too low, the sealing degree decreases, and there is a risk that the original purpose of the sealing treatment, which is to provide corrosion resistance to the aluminum alloy by the oxide film, will be insufficient.

[0074] Therefore, although a sealing treatment using hot water of 60° C. or more and less than 80° C. is classified as hot water sealing, from the viewpoint of ensuring the corrosion resistance of the aluminum alloy while suppressing the diffusion of the color and odor of iodine or iodine compounds, it is considered that the preferable temperature range of the hot water is 70° C. or more and 75° C. or less. In other words, if hot water sealing is performed using hot water of 70° C. or more and 75° C. or less as the sealing treatment, it is possible to more effectively avoid or reduce the adhesion of the color and odor of iodine to objects that are in contact with or close to the surface of the surface treatment film while ensuring the corrosion resistance of the aluminum alloy.

[0075] FIG. 7 is a table showing the relationship between the hot water sealing treatment time shown in FIG. 5 and the state of the surface treatment film.

[0076] The table in Figure 7 shows the state of the surface treatment film when, in step P2', aluminum is anodized in a sulfuric acid solution with a concentration of 20 wt% at a liquid temperature of 10°C to form an oxide film with a thickness of 30 μm, and then, in step P3', a voltage of 100 V is applied for 3 minutes to a PVPI solution with an iodine content of 3.0 wt% to perform electrophoretic deposition of iodine, and then, in step P4', hot water sealing is performed using hot water at 75°C.

[0077] As shown in the table of Figure 7, surface treatment tests including sealing tests were conducted by changing the hot water sealing treatment time. More specifically, as shown in the table of Figure 7, the state of the surface treatment film was examined by changing the hot water sealing treatment time to 10 minutes, 5 minutes, 1 minute, and 10 seconds. The state of the surface treatment film was evaluated by the state of iodine elution, the degree of powdering, the degree of discoloration, and the degree of iodine odor after 12 hours. In the table of Figure 7, ◯ indicates good quality, △ indicates quality within the acceptable range, and × indicates quality outside the acceptable range.

[0078] As shown in the table in Figure 7, the results of the surface treatment test including the sealing test showed that powdering occurred when the hot water sealing treatment time was 10 minutes. It was also confirmed that the elution of iodine, discoloration of iodine, and iodine odor, which cause appearance unevenness, could be reduced the most when the hot water sealing treatment time was 5 minutes.

[0079] Therefore, from the viewpoint of reducing the odor of iodine or iodine compounds while avoiding powdering, the preferable range of hot water sealing treatment time is considered to be 3 minutes or more and 7 minutes or less. In other words, if hot water sealing is performed as the sealing treatment and the hot water sealing treatment time is 3 minutes or more and 7 minutes or less, it is possible to more effectively avoid or reduce the odor of iodine from adhering to objects that come into contact with or near the surface of the surface treatment film while avoiding powdering, which is a typical problem in anodizing.

[0080] When hot water sealing is used as the sealing treatment, bayerite (Al2O3 3H2O) precipitates on the surface of the oxide film, including the fine holes or recesses. That is, in aluminum 2 having a surface treatment film 1 shown in Figure 2, the composition of the sealing layer 6 is bayerite. More specifically, it is considered that the sealing layer 6 made of a bayerite layer grows from the oxide film 4 made of an aluminum oxide layer near the opening of the fine hole or recess 3 toward the center of the fine hole or recess 3.

[0081] Therefore, if boehmite is not precipitated in the surface treatment film 1 but bayerite is, then hot water sealing, not boiling water sealing, has been performed as the sealing treatment. Also, if bayerite is precipitated in the surface treatment film 1 and a metal such as nickel is not contained as an element, then metal salt sealing as the two-step sealing has not been performed.

[0082] However, it is not easy to directly determine whether bayerite or boehmite has precipitated in the surface treatment film, so a method is usually adopted in which the degree of pore sealing of the oxide film is measured to indirectly determine whether bayerite or boehmite has precipitated in the surface treatment film.

[0083] When boehmite is precipitated on the surface of the oxide film due to boiling water sealing, the degree of sealing according to the admittance measurement test is thought to be approximately 30.0 μS as described in the first embodiment. The degree of sealing is thought to vary depending on the sealing conditions such as the sealing time and the hot water temperature.

[0084] In contrast, when bayerite is precipitated on the surface of the oxide film by hot water sealing, the sealing degree in the admittance measurement test is considered to be in the range of approximately 40 μS to 60 μS depending on sealing conditions such as the sealing time and the temperature of the hot water. Therefore, if the sealing degree of the oxide film in the admittance measurement test is 40 μS to 60 μS, it is considered that bayerite is precipitated on the surface of the oxide film by hot water sealing. When hot water sealing was actually performed for 5 minutes using 75°C hot water, the sealing degree of the oxide film was measured in the admittance measurement test and was found to be 50 μS.

[0085] As described above, in the first embodiment, the electrolytic treatment conditions for the anodizing treatment and the iodine impregnation treatment are determined so that the color and odor of iodine or iodine compounds are hard to remove, whereas in the second embodiment, the conditions for the sealing treatment are determined so that the color and odor of iodine or iodine compounds are hard to remove.

[0086] Therefore, according to the second embodiment, like the first embodiment, it is possible to reduce or avoid adhesion of color and odor to an object while exerting the bactericidal and antibacterial effects of iodine or iodine compounds. In addition, according to the second embodiment, safety to the human body can be ensured by making the aluminum having the surface treatment film nickel-free or the like. Therefore, it is possible to use aluminum having the surface treatment film as a material for medical instruments and containers that require safety to the human body.

[0087] Of course, the first and second embodiments may be combined. In other words, not only are the electrolytic treatment conditions for the aluminum anodization treatment performed as the first electrolytic treatment and the electrophoretic deposition of iodine or iodine compounds performed as the second electrolytic treatment appropriately set, but also the sealing treatment may be performed with hot water, so that the color and odor of iodine or iodine compounds are less likely to adhere to the object.

[0088] (Third embodiment) FIG. 8 is a flow chart showing the steps of a method for producing aluminum having a surface treatment film according to the third embodiment of the present invention.

[0089] The method for producing aluminum having a surface treatment film in the third embodiment shown in Fig. 8 differs from the method for producing aluminum having a surface treatment film in the second embodiment in that after the iodine impregnation treatment, a decolorizing and deodorizing treatment that also serves as drying is performed without performing a sealing treatment of the oxide film. The other steps in the method for producing aluminum having a surface treatment film in the third embodiment are not substantially different from the method for producing aluminum having a surface treatment film in the second embodiment, so the same steps are denoted by the same reference numerals and a description thereof will be omitted.

[0090] 8, in step P10 following the iodine impregnation treatment in step P3', a decolorization and deodorization treatment is performed to reduce the diffusion of the color and odor of iodine or iodine compounds to a negligible level. The decolorization and deodorization treatment can be a treatment in which iodine or iodine compounds impregnated into minute holes or recesses of an oxide film are exposed to air, thereby diffusing the iodine or iodine compounds into the air.

[0091] As a result of the test, no significant improvement in the deodorizing and decolorizing effects of iodine or iodine compounds was confirmed even when the surface of the oxide film was exposed to air at room temperature for 24 hours or more. Therefore, the decolorizing and deodorizing treatment can be a treatment in which iodine or iodine compounds impregnated into the fine holes or recesses of the oxide film are exposed to air for 24 hours or more. However, the decolorizing and deodorizing treatment may be replaced with another treatment or may be used in combination with another treatment as the decolorizing and deodorizing treatment. In addition, the decolorizing and deodorizing treatment is not limited to being performed at room temperature. At least a part of the decolorizing and deodorizing treatment may also serve as hot air drying by using hot air.

[0092] When decolorization and deodorization is performed, iodine or iodine compounds are dispersed into the atmosphere to the extent that their color and odor are not lost, as shown in the table in Figure 4. In addition, there are no defects such as iodine elution or powdering, which can cause uneven appearance.

[0093] The color of the surface treatment film immediately after the iodine impregnation treatment depends on the conditions of the iodine impregnation treatment, as exemplified in the table of Figure 4, but the color of the surface treatment film after the decolorization and deodorization treatment is light orange or yellow. Typically, the color of the surface treatment film gradually changes from brown to yellow when the decolorization and deodorization treatment is performed. As a result, the color of the aluminum with the surface treatment film becomes close to gold due to the metallic luster of the aluminum, which is the base material.

[0094] As can be seen from the appearance, even after the decolorization and deodorization treatment, a thin layer of iodine or iodine compounds remains on the inner surface of the fine holes or recesses in the oxide film, which allows the bactericidal and antibacterial effects of iodine or iodine compounds to be maintained.

[0095] Therefore, according to the third embodiment, it is possible to further reduce or more reliably prevent the color and odor of iodine or iodine compounds from fading and adhering to objects while maintaining the bactericidal and antibacterial effects of iodine or iodine compounds. In addition, it is possible to obtain an appearance close to gold.

[0096] Furthermore, if the decolorizing and deodorizing treatment is performed in step P10, even if the amount of iodine or iodine compounds precipitated in excess or the iodine is eluted, causing an uneven appearance, the iodine or iodine compounds will fall off from the oxide film in the subsequent decolorizing and deodorizing treatment.

[0097] Therefore, strictly speaking, unlike the second embodiment, in the third embodiment, it is not important to optimize the treatment conditions for avoiding excessive precipitation of iodine or iodine compounds or elution of iodine in the anodizing treatment in step P2' and the iodine impregnation treatment in step P3'. For example, in the third embodiment, it is not important to determine the electrolytic treatment conditions in the anodizing treatment and the iodine impregnation treatment so that the color and odor of iodine or iodine compounds are difficult to remove, as in the first embodiment.

[0098] (Fourth embodiment) FIG. 9 is a flowchart showing the steps of a method for producing aluminum having a surface treatment film according to the fourth embodiment of the present invention.

[0099] The manufacturing method of aluminum having a surface treatment film in the fourth embodiment shown in FIG. 9 differs from the manufacturing method of aluminum having a surface treatment film in the third embodiment in that after decolorization and deodorization, sealing and drying are performed. The steps up to the decolorization and deodorization in the manufacturing method of aluminum having a surface treatment film in the fourth embodiment are not substantially different from the manufacturing method of aluminum having a surface treatment film in the third embodiment. Moreover, the drying performed in the manufacturing method of aluminum having a surface treatment film in the fourth embodiment is not substantially different from the manufacturing method of aluminum having a surface treatment film in the first embodiment. For this reason, in the fourth embodiment, the same steps as those in the first or third embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0100] As shown in FIG. 9, after the decolorizing and deodorizing treatment in step P10, a step P4'' in which a pore-sealing treatment of the oxide film is performed may be carried out. In that case, a step P5 in which drying is performed is provided after the pore-sealing treatment in step P4''.

[0101] When the oxide film is sealed after the decolorization and deodorization, the deodorization and decolorization of the iodine or iodine compound is already completed to the extent that the color and odor of the iodine or iodine compound are removed and the iodine or iodine compound does not adhere to the object before the oxide film is sealed. Therefore, unlike the first embodiment, there is no restriction on the sealing conditions to make it difficult for the color and odor of the iodine or iodine compound to be removed. Therefore, the sealing can be performed under desired sealing conditions for the purpose of improving the corrosion resistance of the surface treatment film.

[0102] For example, aluminum having a nickel-free surface treatment film can be produced by performing boiling water sealing or hot water sealing. In particular, boiling water sealing can improve the degree of sealing compared to hot water sealing, thereby improving the corrosion resistance of the surface treatment film.

[0103] Needless to say, it is appropriate that the sealing treatment of the oxide film, which is carried out after the decolorizing and deodorizing treatment, be carried out before the oxide film is corroded.

[0104] According to the fourth embodiment described above, not only can the color and odor of iodine or iodine compounds be reduced or prevented from adhering to objects while maintaining the bactericidal and antibacterial effects of iodine or iodine compounds, but also corrosion resistance can be imparted to the surface treatment film by the sealing treatment. In addition, by providing a decolorization and deodorization process for removing the color and odor of iodine or iodine compounds, it is possible to avoid restrictions on the treatment conditions of anodization, iodine impregnation, and sealing treatment in order to avoid excessive precipitation of iodine or iodine compounds or elution of iodine. EXAMPLES

[0105] Example 1 As the primary electrolysis, aluminum was anodized in a sulfuric acid solution with a sulfuric acid concentration of 20 wt% and an electrolysis bath temperature of 10°C to obtain aluminum with an oxide film 30 μm thick. Next, as the secondary electrolysis, electrophoretic deposition of iodine was performed in a PVPI solution with an iodine content of 3.0%. The electrolysis voltage for the secondary electrolysis was 100 V, the electrolysis time for the secondary electrolysis was 3 minutes, and the electrolysis bath temperature for the secondary electrolysis was room temperature.

[0106] Thereafter, nickel salt sealing was performed by immersing the aluminum alloy in a sealing solution containing nickel acetate as a main component for 1 minute, and then drying, thereby producing aluminum alloy having a surface treatment film of Example 1 according to the manufacturing method of the first embodiment.

[0107] Example 2 Anodizing treatment of aluminum and electrophoretic deposition of iodine were performed under the same conditions as in Example 1. After that, hot water sealing was performed for 5 minutes using hot water at 70°C, and then drying was performed to produce aluminum having a surface treatment film of Example 2 by the manufacturing method in the second embodiment.

[0108] Example 3 Anodizing treatment of aluminum and electrophoretic deposition of iodine were performed under the same conditions as in Example 1. Thereafter, the aluminum was simply washed with pure water, but was not sealed, and was exposed to air for 24 hours or more to decolorize and deodorize the iodine, thereby producing aluminum having a surface treatment film of Example 3 by the manufacturing method in the third embodiment.

[0109] Comparative Example 1 Anodizing treatment of aluminum and electrophoretic deposition of iodine were carried out under the same conditions as in Example 1. Then, boiling water sealing was carried out for 5 minutes using hot water at 85°C as shown in the table of Fig. 6, and then drying was carried out to produce aluminum having the surface treatment film of Comparative Example 1 with powdery foxing.

[0110] (Other embodiments) Although specific embodiments have been described above, the described embodiments are merely examples and do not limit the scope of the invention. The novel methods and apparatus described herein may be embodied in various other forms. In addition, various omissions, substitutions, and modifications may be made in the forms of the methods and apparatus described herein without departing from the spirit of the invention. The appended claims and their equivalents include such various forms and modifications as falling within the scope and spirit of the invention. [Explanation of symbols]

[0111] 1 Surface treatment film 2. Aluminum 3. Microscopic holes or recesses 4. Oxide film 5 Iodine or iodine compounds 6 Sealing layer

Claims

1. Anodizing treatment for forming an oxide film having fine holes or recesses on the surface of aluminum; an iodine impregnation treatment for impregnating the fine holes or recesses of the oxide coating with iodine or an iodine compound; a decolorizing and deodorizing treatment for reducing the diffusion of the color and odor of the iodine or iodine compound after the iodine impregnation treatment; A method for producing aluminum having a surface treatment film, comprising the steps of:

2. 2. The method for producing aluminum having a surface treatment film according to claim 1, wherein the decolorizing and deodorizing treatment is a treatment in which the iodine or iodine compound impregnated in the fine pores or recesses is exposed to air for 24 hours or more.

3. 3. The method for producing aluminum having a surface treatment film according to claim 1, wherein the oxide film is not subjected to a sealing treatment.

4. 3. The method for producing aluminum having a surface treatment film according to claim 1, further comprising the step of sealing the oxide film after the decolorizing and deodorizing treatment.

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