Surface-treated aluminum material and method for producing same

Abstract

The invention provides a surface-treated aluminum material and a method for manufacturing the same. A surface-treated aluminum material (1) is provided with: a base material (2) comprising aluminum or an aluminum alloy; and a protective film (3) formed on the base material (2). The protective film (3) has: an oxide layer (31) that contains an aluminum oxide and covers the base material (2); and a hydrated oxide layer (32) that contains a hydrated oxide of aluminum and covers the oxide layer (31). When the surface-treated aluminum material (1) has been heated for 1 hour at a temperature of 200 DEG C by the method according to ASTM-G85-A3, the number of corroded parts reaching the base material (2), which are generated on the surface of the surface-treated aluminum material (1), is 1.0 / cm < 2 > or less at a point in time of 48 hours elapsed from the start of the test, when the surface-treated aluminum material (1) has been heated for 1 hour by the method according to ASTM-G85-A3.

Description

TECHNICAL FIELD

[0001] The present application relates to a surface-treated aluminum material and a method for manufacturing the same. BACKGROUND

[0002] Aluminum materials containing aluminum or aluminum alloys are used for various purposes. In order to achieve various purposes such as improvement of corrosion resistance, improvement of damage resistance, and improvement of design, an anodized film is sometimes provided on the surface of these aluminum materials. Since the functions of aluminum materials can be diversified by an anodized film, the application fields of aluminum materials having an anodized film are increasingly expanding.

[0003] As an example of an aluminum material having an anodized film, Patent Literature 1 describes a member for a substrate processing apparatus and a method for forming a film, characterized by a film formed on the surface of a member for a substrate processing apparatus that performs plasma treatment on a substrate, by connecting the member to an anode of a direct current power supply and performing anodizing treatment by immersion in a solution in which an organic acid is a main component, and performing a semi-seal treatment using boiling water on the film.

[0004] PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: Japanese Patent Application Laid-Open No. 2008-81815 SUMMARY However, the pores of the anodized film formed by the film forming method of Patent Literature 1 are not completely sealed. Therefore, the member treated by the film forming method of Patent Literature 1 has a problem of low corrosion resistance.

[0005] On the other hand, in order to improve the corrosion resistance of the member treated by the film forming method of Patent Literature 1, a method of performing a seal treatment, which completely seals the pores of the anodized film, can be considered. However, in this case, in use, when the temperature of the member rises, the anodized film is likely to develop cracks, and it can rather lead to a decrease in corrosion resistance. Therefore, the member treated by the film forming method of Patent Literature 1 has a limit in improving the maximum use temperature, that is, the maximum temperature assumed in the environment in which the member is used, while maintaining high corrosion resistance.

[0006] The present application was achieved in view of such a background, and an object thereof is to provide a surface-treated aluminum material and a method for manufacturing the same, which can easily improve the maximum use temperature while maintaining high corrosion resistance.

[0007] TECHNICAL SOLUTION TO THE PROBLEM One embodiment of the present application is a surface-treated aluminum material in which the surface-treated aluminum material has: a base material containing aluminum or an aluminum alloy; and a protective film formed on the base material, The protective coating film has: an oxide layer containing an oxide of aluminum, and covering the base material; and a hydrated oxide layer containing a hydrated oxide of aluminum, and covering the oxide layer, In a case where SWAAT test is performed on the surface-treated aluminum material after heating at a temperature of 200°C for 1 hour by a method according to ASTM-G85-A3, the number of corrosion portions reaching the base material, which are generated on the surface of the surface-treated aluminum material at a time of 48 hours from the start of the test, is 1.0 per cm 2 The following.

[0008] Another aspect of the present application is a method for manufacturing a surface-treated aluminum material, wherein the method for manufacturing a surface-treated aluminum material is the method for manufacturing a surface-treated aluminum material of the aspect, The oxide layer having pores is formed on the base material by subjecting the base material to an anodizing treatment, Then, the base material and the oxide layer are heated at a temperature of 100°C or higher and 350°C or lower, Then, the oxide layer is brought into contact with a pore sealing agent, and the pores are sealed while the hydrated oxide layer is formed on the oxide layer.

[0009] Effects of the Invention The surface-treated aluminum material (hereinafter referred to as "aluminum material") has a protective coating film having the oxide layer and the hydrated oxide layer on the surface of the base material. In addition, in a case where SWAAT test is performed on the surface-treated aluminum material after heating at a temperature of 200°C for 1 hour by a method according to ASTM-G85-A3, the number of corrosion portions reaching the base material, which are generated on the surface of the surface-treated aluminum material at a time of 48 hours from the start of the test, is 1.0 per cm 2 The following. The aluminum material having such characteristics can suppress the generation of cracks even in a case where the temperature is increased. Therefore, the aluminum material can easily increase the maximum use temperature while maintaining high corrosion resistance.

[0010] In addition, in the method for manufacturing the aluminum material, the oxide layer formed by the anodizing treatment is heated at a temperature within the specific range after the anodizing treatment is performed on the base material. In this way, by heating the oxide layer before the pores of the oxide layer are sealed, the internal stress generated when the oxide layer is formed can be relaxed. Furthermore, by bringing the oxide layer into contact with the pore sealing agent after the internal stress of the oxide layer is relaxed, the pores are sealed while the hydrated oxide layer is formed on the oxide layer, so that the generation of cracks can be suppressed even in a case where the temperature of the aluminum material is increased, and high corrosion resistance can be maintained in a high-temperature environment.

[0011] As described above, according to the described mode, it is possible to provide a surface-treated aluminum material capable of easily increasing the maximum use temperature while maintaining high corrosion resistance, and a manufacturing method thereof. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a cross-sectional view of a surface-treated aluminum material in an embodiment.

[0013] Figure 2 is a cross-sectional view of a base material on which an oxide layer is formed during the manufacturing process of the surface-treated aluminum material in an embodiment. DETAILED DESCRIPTION

[0014] (aluminum material) The base material of the aluminum material contains aluminum or an aluminum alloy. The shape of the base material is not particularly limited, and can take various shapes according to the use of the aluminum material. For example, the base material can be an elongated material (Japanese: junsen zairyo) such as a rolled plate, an extruded material, or can be a cast material, a forged material. In the case where the shape of the base material is a plate shape, the thickness of the base material is not particularly limited. More specifically, the base material can be, for example, a cold-rolled plate having a thickness of about 1 mm, or can be a hot-rolled plate having a thickness of about 50 mm.

[0015] In addition, the material of the base material can be appropriately selected from the group consisting of aluminum and aluminum alloys according to the use of the aluminum material. More specifically, as the aluminum constituting the base material, for example, 1000 series aluminum can be used. In addition, as the aluminum alloy constituting the base material, for example, 2000 series aluminum alloy, 3000 series aluminum alloy, 4000 series aluminum alloy, 5000 series aluminum alloy, 6000 series aluminum alloy, 7000 series aluminum alloy, and 8000 series aluminum alloy can be used. In addition, the base material can also be a clad material in which two or more layers having mutually different chemical compositions are laminated.

[0016] On the base material, a protective film is provided, the protective film containing: an oxide layer containing an oxide of aluminum, laminated on the base material; and a hydrous oxide layer containing a hydrous oxide of aluminum, laminated on the oxide layer. More specifically, the hydrous oxide layer can also be composed of a hydrous oxide of aluminum. In addition, the hydrous oxide layer can also contain a hydrous oxide, and a metal salt and / or a metal oxide. The protective film can be obtained, for example, by performing an anodizing treatment on the base material, forming an oxide layer having a plurality of pores on the surface of the base material, and then performing a pore sealing treatment to close the pores of the oxide layer with a hydrous oxide layer. Such a protective film is excellent in corrosion resistance because the pores are sealed. Therefore, by forming the protective film on the base material, it is possible to improve the corrosion resistance of the aluminum material.

[0017] The thickness of the protective film is preferably 5 μm or more, more preferably 7 μ m or more, further preferably 10 μ m or more. In this case, the corrosion resistance of the aluminum material can be further improved. The upper limit of the thickness of the protective film is not particularly limited from the viewpoint of the corrosion resistance, but the upper limit of the thickness of the protective film in terms of manufacturing is, for example, 200 μ m or less. μ

[0018] After the aluminum material is heated at a temperature of 200°C for 1 hour, in the case where a SWAAT test is performed by a method according to ASTM-G85-A3, the number of corrosion portions reaching the base material generated on the surface of the aluminum material at a time of 48 hours from the start of the test is 1.0 or less per cm 2 or more. The aluminum material having such characteristics can suppress the generation of cracks and improve the corrosion resistance at high temperatures when used at high temperatures. Therefore, the aluminum material can easily improve the maximum use temperature while maintaining high corrosion resistance.

[0019] From the viewpoint of more easily improving the maximum use temperature of the aluminum material, in the case where a SWAAT test is performed under the specific conditions, the number of corrosion portions reaching the base material generated on the surface of the aluminum material at a time of 48 hours from the start of the test is preferably 0.80 or less per cm 2 or more, more preferably 0.60 or less per cm 2 or more, further preferably 0.50 or less per cm 2 or more, particularly preferably 0.30 or less per cm 2 or more, most preferably 0.10 or less per cm 2 or less.

[0020] Note that the specific test method of the SWAAT test and the calculation method of the number of corrosion portions are as follows. First, a corrosion test surface is set in a part of the surface of the protective film in the aluminum material, and the area other than the corrosion test surface in the surface of the protective film is covered with a masking tape. Next, the aluminum material is arranged in a corrosion tester so that the corrosion test surface becomes the front surface. Then, the temperature in the tank of the tester is maintained at 49 ± 2°C, and 0.5 hours of test solution is continuously sprayed to the corrosion test surface. Note that, as the test solution in the SWAAT test, a water solution having a pH of 2.8 or more and 3.0 or less is used, which is prepared by adding acetic acid to an artificial seawater solution having a composition according to ASTM D 1141-98. In addition, the spraying speed of the test solution is set to 1.0 ml / 80 cm 2 or more and 2.0 ml / 80 cm 2 ​Within the range below / h.

[0021] After continuously spraying the test solution onto the corrosion test surface for 0.5 hours, stop spraying the test solution and let the aluminum material stand in the testing machine for 1.5 hours. During this time, the temperature inside the testing machine is set to 49±2℃, and the relative humidity inside the tank is set to above 98%RH. Then, repeat the spraying of the test solution and the standing of the aluminum material. The SWAAT test ends when 48 hours have elapsed since the start of the test.

[0022] After the SWAAT test, the aluminum material removed from the testing machine is washed with water and then dried. Next, the aluminum material is immersed in concentrated nitric acid to remove the corrosion products generated by the SWAAT test. Then, all corrosion patches appearing on the corrosion test surface are observed under a microscope to determine whether the base material is exposed at the bottom of the corrosion patch. The number of exposed corrosion patches at the bottom of the base material is then counted. The number of exposed corrosion patches (unit: number of patches) is divided by the area of ​​the corrosion test surface (unit: cm²). 2 This allows for the calculation of the number of corroded areas reaching the base material after the SWAAT test (unit: number / cm). 2 ).

[0023] After heating the aluminum material at 200°C for 1 hour, and then performing a CASS test according to the method specified in JIS H8502:1999, the number of corrosion sites on the surface of the aluminum material that reach the base material is preferably 2.0 sites / cm² after 24 hours from the start of the test. 2 The following describes aluminum materials with these properties. Even when used at high temperatures, they can suppress crack formation and further improve corrosion resistance at high temperatures. Therefore, aluminum materials with these properties can more easily increase the maximum operating temperature while maintaining high corrosion resistance.

[0024] From the viewpoint of more easily increasing the maximum service temperature of the aluminum material, when conducting the CASS test under the specific conditions, the number of corrosion sites formed on the surface of the aluminum material that reach the base material at 24 hours after the start of the test is preferably 1.8 per cm. 2 The following is more preferred: 1.6 particles / cm 2 The following is a further preferred value of 1.4 per cm. 2 The following is particularly preferred: 1.2 pieces / cm 2 The preferred value is 1.0 / cm. 2 the following.

[0025] Note that the specific test method of the CASS test and the calculation method of the number of corrosion portions are as follows. First, a part of the surface of the protective film in the aluminum material is set as a corrosion test surface, and the area other than the corrosion test surface in the surface of the protective film is covered with a masking tape. Next, the aluminum material is arranged in the corrosion test machine so that the corrosion test surface becomes the front surface. Then, the temperature in the tank of the test machine is maintained at 50 ± 2°C, and at the same time, the test liquid is continuously sprayed to the corrosion test surface. Then, the CASS test is ended at the time when the elapsed time from the start of the test reaches 24 hours. Note that, as the test liquid in the CASS test, a water solution of pH 3.0 prepared by dissolving 50 ± 5 g / L of sodium chloride and 0.26 ± 0.02 g / L of copper (II) chloride dihydrate in pure water, and then adding about 1 mL / L of acetic acid is used. In addition, the spraying speed of the test liquid is set to a range of 1.0 ml / 80 cm 2 / h or more and 2.0 ml / 80 cm 2 / h or less.

[0026] After the CASS test, the aluminum material taken out of the test machine is washed with water, and then dried. Then, the corrosion product generated by the CASS test is removed by immersing the aluminum material in concentrated nitric acid. Then, all the corrosion portions present on the corrosion test surface are observed using a microscope, and it is determined whether or not the base material is exposed at the bottom of the corrosion portion. Then, the number of corrosion portions in which the base material is exposed at the bottom is counted. By dividing the number of corrosion portions in which the base material is exposed (unit: pieces) obtained above by the area of the corrosion test surface (unit: cm 2 ), the number of corrosion portions reaching the base material after the CASS test (unit: pieces / cm 2 ) can be obtained.

[0027] In the case where the sealing degree test is performed by the method prescribed in JIS H8683-2:2013, the mass reduction per unit area of the aluminum material is preferably 0.3 g / dm 2 or more. The aluminum material involved is sufficiently sealed by the hydrated oxide layer from the pores of the oxide layer, and thus the corrosion resistance of the aluminum material can be more reliably improved.

[0028] Note that the specific method of the sealing degree test is as follows. First, 35 mL of phosphoric acid and 20 g of chromic anhydride are dissolved in water, and 1 L of a test liquid is prepared. Next, a test piece including a protective film is collected from the aluminum material, and the area of the protective film in the test piece is measured. After the stains on the surface of the test piece are removed, the mass of the test piece is measured. Then, the test piece is immersed in the test liquid maintained at a temperature of 38°C ± 1°C for 15 minutes ± 5 seconds.

[0029] After the immersion of the test piece in the test liquid is completed, the test piece is washed with running water, and further washed with deionized water or distilled water. After the washed test piece is sufficiently dried, the mass of the test piece is measured.

[0030] The area A (unit: dm 2 ) of the protective coating film of the test piece obtained by the above operation, the mass m1 (unit: g) of the test piece before immersion in the test liquid, and the mass m2 (unit: g) of the test piece after immersion in the test liquid are used to calculate the mass reduction per unit area δ A (unit: g / dm 2 ).

[0031] δ A = (m1 - m2) / A (1) As described above, the aluminum material can easily increase the maximum use temperature while maintaining high corrosion resistance. Therefore, the aluminum material is suitable for members that become high temperature in use, such as a cover member provided around a fan of a heating cooking appliance, a metal housing of a kitchen device, a member for a semiconductor manufacturing device, and the like. More specifically, as a member for a semiconductor manufacturing device, for example, a chamber in a semiconductor manufacturing device such as a film forming device and an etching device, a member disposed in the chamber, and the like can be given. As a kitchen device, for example, a heating cooking appliance such as an oven, a microwave oven, a gas stove, a deep fryer, a hot food display case, and the like can be given.

[0032] (Method for manufacturing aluminum material) In manufacturing the surface-treated aluminum material, first, a base material containing aluminum or an aluminum alloy is prepared. The method for manufacturing the base material is not particularly limited, and a publicly known method can be employed. For example, the base material can be manufactured by a method in which casting, rolling, and heat treatment are appropriately combined. As a casting method for the base material, either of DC casting and continuous casting can be employed.

[0033] In addition, during the period from the manufacturing of the base material to the implementation of the anodizing treatment, a pretreatment for the anodizing treatment such as degreasing, etching, descaling, polishing, and grinding can be implemented as necessary. Subsequently, by implementing the anodizing treatment on the base material, the oxide layer having pores is formed on the base material. In the anodizing treatment, by flowing a direct current between the base material and a counter electrode in a state in which the base material and the counter electrode are immersed in an electrolyte, an oxide layer is formed on the surface of the base material. The oxide layer thus formed is composed of an oxide of aluminum such as aluminum oxide, and has a plurality of pores.

[0034] The electrolyte used in the anodization treatment can be an acidic electrolyte containing sulfuric acid, phosphoric acid or the like as an electrolyte, or an alkaline electrolyte containing sodium metaborate or the like as an electrolyte. The electrolyte used in the anodization treatment preferably contains an inorganic electrolyte containing: an inorganic cation such as a metal ion, an ammonium ion; and an anion selected from one or two or more of a sulfate ion, a phosphate ion, a borate ion. By using an electrolyte containing an inorganic electrolyte for the anodization treatment, it is possible to more easily form an oxide layer having a desired structure.

[0035] The current density of the direct current in the anodization treatment can be appropriately set within a range of, for example, 1 mA / cm 2 The temperature of the electrolyte in the anodization treatment can be appropriately set within a range of, for example, 0°C or higher and 40°C or lower. 2 The temperature of the electrolyte in the anodization treatment can be appropriately set within a range of, for example, 0°C or higher and 40°C or lower.

[0036] The thickness of the oxide layer formed in the anodization treatment is preferably 2 μ μm or more. By making the thickness of the oxide layer 2 μ μm or more, it is possible to make the thickness of the protective film obtained after sealing the pores sufficient, and to more easily obtain an aluminum material excellent in corrosion resistance and heat resistance.

[0037] In the production method, after the anodization treatment, the base material and the oxide layer are heated at a temperature of 100°C or higher and 350°C or lower. By heating the oxide layer at a temperature within the specific range before sealing the pores of the oxide layer after the anodization treatment, it is possible to relax the internal stress of the oxide layer. Furthermore, by sealing the pores after relaxing the internal stress of the oxide layer, it is possible to reduce the internal stress in the protective film after sealing the pores. As a result, it is possible to suppress the generation of cracks in the protective film when heated, and to improve the corrosion resistance of the aluminum material at high temperatures.

[0038] In the case where the heating temperature of the oxide layer is less than 100°C, the relaxation of the internal stress of the oxide layer becomes insufficient, and it is possible that cracks are generated in the protective film when the temperature of the aluminum material rises, and the corrosion resistance decreases. On the other hand, in the case where the heating temperature of the oxide layer exceeds 350°C, the oxide layer cannot follow the thermal expansion of the base material and it is possible that cracks are generated in the protective film. From the viewpoint of more easily increasing the maximum use temperature of the aluminum material, the heating temperature of the oxide layer is preferably 130°C or higher and 330°C or lower, more preferably 150°C or higher and 310°C or lower, further preferably 180°C or higher and 290°C or lower, and particularly preferably 200°C or higher and 280°C or lower.

[0039] In the heating of the oxide layer, the heating can be ended immediately after the temperature of the oxide layer reaches the desired temperature, or the temperature can be maintained for a certain period of time after reaching the desired temperature. From the viewpoint of sufficiently relaxing the internal stress of the oxide layer and more reliably improving the corrosion resistance of the aluminum material at high temperatures, the heating time from the start of the heating of the oxide layer to the end of the heating is preferably 3 minutes or more.

[0040] In addition, the heating temperature of the oxide layer is preferably higher than the maximum use temperature of the surface-treated aluminum material. In this case, the surface-treated aluminum material can be more reliably prevented from being cracked, and the corrosion resistance at high temperatures can be more reliably improved.

[0041] The reason why the above-described effects are obtained by setting the heating temperature of the oxide layer to be higher than the maximum use temperature of the surface-treated aluminum material is not clear, but for example, the following reason can be considered. That is, it is considered that if the oxide layer is heated in the manufacturing method of the aluminum material, the strain having an energy lower than the heating temperature of the oxide layer, which is present in the strain in the oxide layer, is released, and the internal stress is relaxed. Therefore, it is considered that in the case where the temperature of the surface-treated aluminum material obtained by the manufacturing method is a temperature lower than the heating temperature of the oxide layer, a state where the strain that should be released is not present in the oxide layer is obtained. Therefore, it is considered that by setting the heating temperature of the oxide layer to be higher than the maximum use temperature of the surface-treated aluminum material, the cracking accompanying the release of the strain in the oxide layer can be suppressed.

[0042] After the oxide layer is heated, the oxide layer is brought into contact with a sealing agent. Thereby, the hydrated oxide layer is formed on the oxide layer, and the pores are sealed with the hydrated oxide layer. As the sealing agent, for example, warm water having a temperature of 80°C or higher, water vapor, an aqueous solution containing ions of one or two or more metal elements selected from Ni (nickel), Cr (chromium), Zr (zirconium), Si (silicon), Ti (titanium), Au (gold), Ag (silver), Co (cobalt), Mo (molybdenum), Mn (manganese), Nb (niobium), Ta (tantalum), W (tungsten), Zn (zinc), Fe (iron), Ir (iridium), and Sc (scandium), and the like, which can form a hydrated oxide by reacting with an oxide of aluminum, can be used. In the case where the sealing treatment is performed using warm water or water vapor, a hydrated oxide layer containing a hydrated oxide of aluminum can be formed on the oxide layer.

[0043] Furthermore, when sealing pores using an aqueous solution containing ions of the aforementioned metal element, a hydrated oxide layer containing hydrated aluminum oxide and salts and / or oxides of the aforementioned metal element can be formed on the oxide layer. The metal element can exist in the aqueous solution as a metal ion or as a complex ion. More specifically, aqueous solutions containing metal salts of the aforementioned metal element, such as nickel acetate aqueous solution, cobalt acetate aqueous solution, chromate aqueous solution, and silicate aqueous solution, can be used as sealing agents.

[0044] From the viewpoint of more easily obtaining aluminum materials with excellent corrosion resistance and heat resistance, warm water at a temperature of 80°C or higher is preferred as the sealing agent. Furthermore, by sealing the pores of the oxide layer with warm water, a hydrated oxide layer free of metal salts can be formed on the oxide layer. Metal salts in the hydrated oxide layer can potentially cause internal contamination of the device, for example, if the aluminum material is used as a component in a semiconductor manufacturing apparatus. Therefore, by using warm water as the sealing agent to form a hydrated oxide layer free of metal salts, it is possible to easily obtain aluminum materials suitable for use as components in semiconductor manufacturing apparatuses. When using warm water as the sealing agent, it is more preferable to seal the pores of the oxide layer by contacting the oxide layer with warm water at 80°C or higher for 10 minutes to less than 120 minutes.

[0045] Example Reference Figures 1-2 Examples of the surface-treated aluminum material and its manufacturing method are described below. Figure 1 As shown, the surface-treated aluminum material 1 in this example has: a base material 2 comprising aluminum or an aluminum alloy; and a protective coating 3 formed on the base material. The protective coating 3 has: an oxide layer 31 comprising an aluminum oxide covering the base material 2; and a hydrated oxide layer 32 comprising a hydrated aluminum oxide covering the oxide layer 31. When the surface-treated aluminum material 1 was subjected to a SWAAT test after being heated to 200°C for 1 hour according to ASTM-G85-A3, after 48 hours from the start of the test, the number of corrosion sites reaching the base material 2 on the surface of the surface-treated aluminum material 1 was 1.0 / cm². 2 the following.

[0046] When manufacturing aluminum material 1 in this example, as Figure 2 As shown, firstly, anodizing is performed on the base material 2 to form an oxide layer 31 with pores 311. Then, the base material 2 and the oxide layer 31 are heated at a temperature of 100°C or higher and 350°C or lower to alleviate the internal stress of the oxide layer 31. Then, by contacting the oxide layer 31 with a sealing agent, a hydrated oxide layer 32 is formed on the oxide layer 31, and the pores 311 are sealed, thereby obtaining the aluminum material 1.

[0047] Table 1 shows specific examples of aluminum material 1 (test materials A1 to A3). The manufacturing method of test materials A1 to A3 is as follows. First, as the base material 2, an aluminum plate with a chemical composition shown by alloy number A6016 and a thickness of 1 mm is prepared. The base material 2 is subjected to a pretreatment of anodizing. Specifically, as a pretreatment, the base material 2 is first subjected to an alkaline etching treatment by immersing it in an aqueous sodium hydroxide solution with a concentration of 5% by mass and a temperature of 55°C. Then, the base material 2 is immersed in nitric acid with a concentration of 30% by mass for decontamination treatment. Then, the base material 2 is immersed in a mixed solution of phosphoric acid and sulfuric acid at a volume ratio of phosphoric acid:sulfuric acid = 7:3 and a temperature of 85°C for chemical polishing treatment. After the chemical polishing treatment, a decontamination treatment is performed again under the same conditions as above.

[0048] After pretreating the base material 2 as described above, the base material 2 is subjected to anodizing treatment to form an oxide layer 31 on the surface of the base material 2. The electrolyte used in the anodizing treatment is a 15% by mass sulfuric acid aqueous solution, and the electrolyte temperature is set to 5°C. Furthermore, the current density in the anodizing treatment is set to 10 mA / cm². 2 The processing time is set to 60 minutes. For example... Figure 2 As shown, the oxide layer 31 formed in this way is a so-called porous acid-resistant aluminum coating, having multiple pores 311. It should be noted that the thickness of the oxide layer 31 formed by anodizing under the above conditions is approximately 15 mm. μ m.

[0049] After anodizing, the base material 2 is heated in a heating furnace to alleviate the internal stress of the oxide layer 31. The set temperature of the heating furnace is the value shown in the "Heating Temperature" column of Table 1, and the residence time of the base material in the furnace, i.e., the time from the start of heating to the end of heating, is the value shown in the "Heating Time" column of Table 1.

[0050] Then, by immersing the base material 2 having oxide layer 31 in warm water at 100°C (as a sealing agent) for 60 minutes, a hydrated oxide layer 32 containing hydrated aluminum oxide is formed on oxide layer 31, and the hydrated oxide layer 32 is used to seal the pores 311 of oxide layer 31. Through the above, test materials A1 to A3 shown in Table 1 can be obtained. It should be noted that when the pores 311 of oxide layer 31 are sealed under these conditions, the mass reduction per unit area of ​​aluminum material 1 is approximately 0.01 g / dm² when the sealing degree test is performed according to the method specified in JISH 8683-2:2013. 2 .

[0051] The test materials B1 to B2 shown in Table 1 are test materials for comparison with the test materials Al to A3. The manufacturing method of the test material Bl is the same as that of the test material Al except that the oxide layer 31 is not heated but is brought into contact with a sealing agent after the oxide layer 31 is formed on the base material 2. The manufacturing method of the test material B2 is the same as that of the test material Bl except that the heating temperature and the heating time of the oxide layer 31 are changed as shown in Table 1.

[0052] The results of SWAAT tests and CASS tests using the test materials Al to A3 and the test materials Bl to B2 are shown in Table 1. The detailed methods of the SWAAT tests and the CASS tests are described below.

[0053] [SWAAT test] First, each test material is heated at a temperature of 200°C for 1 hour. A rectangular corrosion test surface of 5 cm in length and 10 cm in width is provided on the surface of the protective coating in the heated test material, and the area other than the corrosion test surface in the surface of the protective coating is covered with a masking tape. Then, after the test material is arranged in the corrosion tester with the corrosion test surface facing upward, the SWAAT test is performed by the method according to ASTM-G85-A3. The test material is taken out of the corrosion tester at the time of 48 hours from the start of the test. After the test material is washed with pure water, it is completely dried using a drying machine. Then, the test material is immersed in concentrated nitric acid at a temperature of 25°C for 5 minutes, and the corrosion product generated on the corrosion test surface is removed.

[0054] Next, all the corrosion portions generated on the corrosion test surface are observed using a microscope, and it is determined whether the base material is exposed at the bottom of the corrosion portion. Then, the number of corrosion portions in which the base material is exposed at the bottom is counted. By dividing the number of corrosion portions in which the base material is exposed (unit: pieces) obtained above by the area of the corrosion test surface (unit: cm 2 ), the number of corrosion portions reaching the base material after the SWAAT test (unit: pieces / cm 2 ) can be calculated.

[0055] [CASS test] First, each test material was heated at a temperature of 200°C for 1 hour. A rectangle of 5 cm in length and 10 cm in width was set on the surface of the protective coating film in the heated test material, and the area other than the corrosion test surface in the surface of the protective coating film was covered with a masking tape. Then, after the test material was arranged in the corrosion tester with the corrosion test surface facing upward, a CASS test was performed by the method prescribed in JIS H8502:1999. The test material was taken out of the corrosion tester at the time point of 24 hours from the start of the test. After the test material was washed with pure water and completely dried using a drying machine. Then, the test material was immersed in concentrated nitric acid at a temperature of 25°C for 5 minutes, and the corrosion product generated on the corrosion test surface was removed.

[0056] Next, all the corrosion portions generated on the corrosion test surface were observed using a microscope, and it was determined whether the base material was exposed at the bottom of the corrosion portion. Then, the number of corrosion portions in which the base material was exposed at the bottom was counted. By dividing the number of corrosion portions in which the base material was exposed (unit: pieces) obtained above by the area of the corrosion test surface (unit: cm 2 ), the number of corrosion portions reaching the base material after the CASS test (unit: pieces / cm 2 ) can be obtained.

[0057] [Table 1] As shown in Table 1, the test materials Al to A3 formed an oxide layer on the base material, and after the pores of the oxide layer were sealed, the oxide layer was heated at a temperature within the specified range. Therefore, after these test materials were heated at a temperature of 200°C for 1 hour, a SWAAT test was performed by the method according to ASTM-G85-A3, and in this case, the number of corrosion portions reaching the base material generated on the surface of the surface-treated aluminum material at the time point of 48 hours from the start of the test was 1.0 pieces / cm 2 or more. The aluminum material having such a characteristic can suppress the generation of cracks even in the case where the temperature rises. Therefore, the aluminum material can easily increase the maximum use temperature while maintaining high corrosion resistance.

[0058] On the other hand, the test material Bl formed an oxide layer on the base material, and after the pores of the oxide layer were sealed without heating the oxide layer, and therefore, when a SWAAT test was performed under the specified conditions, the number of corrosion portions reaching the base material generated on the surface of the surface-treated aluminum material increased. Therefore, it was difficult to increase the maximum use temperature of the test material Bl.

[0059] The test material B2 had a short heating time when the oxide layer was heated, and thus, the number of corrosion portions reaching the base material that were generated on the surface of the surface-treated aluminum material under the specific conditions of the SWAAT test was large. Therefore, it was difficult to increase the maximum use temperature of the test material B2.

[0060] The above describes the surface-treated aluminum material and the method for manufacturing the same according to the present application based on the examples, but the specific modes of the surface-treated aluminum material and the method for manufacturing the same according to the present application are not limited to the modes of the examples, and the structure can be appropriately changed within a range not impairing the gist of the present application.

[0061] For example, the surface-treated aluminum material according to the present application can adopt the modes described in [1] to [4] below.

[0062] [1] A surface-treated aluminum material, wherein the surface-treated aluminum material has: a base material including aluminum or an aluminum alloy; and a protective coating film formed on the base material, the protective coating film has: an oxide layer including an oxide of aluminum that covers the base material; and a hydrated oxide layer including a hydrated oxide of aluminum that covers the oxide layer, in a case where a SWAAT test is performed on the surface-treated aluminum material that has been heated at a temperature of 200°C for 1 hour according to a method according to ASTM-G85-A3, the number of corrosion portions reaching the base material that are generated on the surface of the surface-treated aluminum material at a time of 48 hours from the start of the test is 1.0 per cm 2 or more.

[0063] [2] The surface-treated aluminum material according to [1], wherein, in a case where a CASS test is performed on the surface-treated aluminum material that has been heated at a temperature of 200°C for 1 hour according to a method specified in JIS H8502:1999, the number of corrosion portions reaching the base material that are generated on the surface of the surface-treated aluminum material at a time of 24 hours from the start of the test is 2.0 per cm 2 or more.

[0064] [3] The surface-treated aluminum material according to [1] or [2], wherein the thickness of the protective coating film is 5 μ μm or more and 60 μ μm or less.

[0065] [4] The surface-treated aluminum material according to any one of [1] to [3], wherein the mass reduction per unit area in a case where a sealing degree test is performed according to a method specified in JIS H8683-2:2013 is 0.3 g / dm 2 or more.

[0066] Further, the present application relates to a method for manufacturing a surface-treated aluminum material, which can be performed in the following manner shown in [5] to [9].

[0067] [5] A method for manufacturing a surface-treated aluminum material, which is the method for manufacturing a surface-treated aluminum material according to any one of [1] to [4], by subjecting the base material to an anodization treatment, thereby forming the oxide layer having pores on the base material, thereafter, heating the base material and the oxide layer at a temperature of 100°C or higher and 350°C or lower, thereafter, contacting the oxide layer with a pore sealing agent, thereby forming the hydrous oxide layer on the oxide layer while sealing the pores.

[0068] [6] The method for manufacturing a surface-treated aluminum material according to [5], wherein a heating time from the start of the heating of the oxide layer to the end of the heating in the heating is 3 minutes or longer.

[0069] [7] The method for manufacturing a surface-treated aluminum material according to [5] or [6], wherein an electrolyte used in the anodization treatment contains an inorganic electrolyte containing: an inorganic cation; and an anion selected from one or two or more of sulfate ions, phosphate ions, and borate ions.

[0070] [8] The method for manufacturing a surface-treated aluminum material according to any one of [5] to [7], wherein the pore sealing agent is warm water having a temperature of 80°C or higher, an aqueous solution containing ions of a metal element selected from one or two or more of Ni, Cr, Zr, Si, Ti, Au, Ag, Co, Mo, Mn, Nb, Ta, W, Zn, Fe, Ir, and Sc, or water vapor.

[0071] [9] The method for manufacturing a surface-treated aluminum material according to [8], wherein, in the sealing, the oxide layer is contacted with the warm water having a temperature of 80°C or higher as the pore sealing agent for 10 minutes or longer and less than 120 minutes.

Claims

1. A surface-treated aluminum material, characterized in that, having: a base material including aluminum or an aluminum alloy; and a protective coating film formed on the base material, the protective coating film has: an oxide layer including an oxide of aluminum and covering the base material; and a hydrated oxide layer including a hydrated oxide of aluminum and covering the oxide layer, In the case where a SWAAT test is performed on the surface-treated aluminum material after heating at a temperature of 200°C for 1 hour by a method according to ASTM-G85-A3, the number of corrosion portions reaching the base material from the surface of the surface-treated aluminum material produced at a time point of 48 hours from the start of the test is 1.0 per cm 2 The following.

2. The surface-treated aluminum material according to claim 1, wherein In the case where the surface-treated aluminum material is subjected to a CASS test by the method prescribed in JIS H8502: 1999 after being heated at a temperature of 200°C for 1 hour, the number of corrosion portions reaching the base material produced on the surface of the surface-treated aluminum material at a time 24 hours from the start of the test is 2.0 pieces / cm 2 The following.

3. The surface-treated aluminum material according to claim 1 or 2, wherein The protective coating film has a thickness of 5 μ m or more and 60 μ m or less.

4. The surface-treated aluminum material according to any one of claims 1 to 3, wherein The mass reduction per unit area in the case where the sealability test is performed by the method prescribed in JIS H8683-2:2013 is 0.3 g / dm 2 The following.

5. A method for manufacturing the surface-treated aluminum material according to any one of claims 1 to 4, characterized by: forming the oxide layer having pores on the base material by subjecting the base material to an anodizing treatment, thereafter, heating the base material and the oxide layer at a temperature of 100°C or higher and 350°C or lower, thereafter, bringing the oxide layer into contact with a pore sealing agent to form the hydrated oxide layer on the oxide layer while sealing the pores.

6. The method for manufacturing the surface-treated aluminum material according to claim 5, wherein in the heating, a heating time from the start of the heating of the oxide layer to the end of the heating is 3 minutes or longer.

7. The method for manufacturing the surface-treated aluminum material according to claim 5 or 6, wherein the electrolyte used in the anodizing treatment includes an inorganic electrolyte including: inorganic cations; and anions selected from one or two or more of sulfate ions, phosphate ions, and borate ions.

8. The method for manufacturing the surface-treated aluminum material according to any one of claims 5 to 7, wherein the pore sealing agent is warm water having a temperature of 80°C or higher, an aqueous solution of ions of a metal element selected from one or two or more of Ni, Cr, Zr, Si, Ti, Au, Ag, Co, Mo, Mn, Nb, Ta, W, Zn, Fe, Ir, and Sc, or water vapor.

9. The method for manufacturing the surface-treated aluminum material according to claim 8, wherein in the sealing, the oxide layer is brought into contact with the warm water of 80°C or higher as the pore sealing agent for 10 minutes or longer and less than 120 minutes.

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