Surface-treated aluminum material and method for producing same

Abstract

A surface-treated aluminum material (1) has a base material (2) made of aluminum or an aluminum alloy, and a protective film (3) formed on the base material (2). The protective film (3) comprises an oxide layer (31) that is made of an aluminum oxide and that covers the base material (2), and a hydrated oxide layer (32) that contains a hydrated oxide of aluminum and that covers the oxide layer (31). When a SWAAT test is performed by a method conforming to ASTM-G85-A3 on the surface-treated aluminum material (1) heated for 1 hour at a temperature of 200°C, the number of corroded parts that occur on the surface of the surface-treated aluminum material (1) and that have reached the base material (2) at the point in time at which 48 hours have elapsed since the start of the test is 1.0 per cm2 or below.

Description

Surface-treated aluminum material and its manufacturing method

[0001] The present invention relates to a surface-treated aluminum material and a method for producing the same.

[0002] Aluminum materials made of aluminum or aluminum alloys are used in a variety of applications. An anodized film may be formed on the surface of these aluminum materials to achieve various purposes, such as improving corrosion resistance, scratch resistance, and design. Because the anodized film can impart a wide variety of functions to aluminum materials, the fields of application of aluminum materials with an anodized film are expanding.

[0003] As an example of an aluminum material having an anodized film, Patent Document 1 describes a component for a substrate processing apparatus that performs plasma processing on a substrate, the component having a film formed on the surface of the component by anodizing treatment in which the component is connected to the anode of a DC power supply and immersed in a solution mainly containing an organic acid, and the film is subjected to a semi-sealing treatment using boiling water, and a method for forming the film.

[0004] JP 2008-81815 A

[0005] However, the pores of the anodic oxide film formed by the film formation method of Patent Document 1 are not completely closed, which causes a problem that the parts treated by the film formation method of Patent Document 1 have low corrosion resistance.

[0006] On the other hand, in order to improve the corrosion resistance of parts treated by the coating formation method of Patent Document 1, a method of completely closing the pores in the anodized coating by performing a pore sealing treatment is conceivable. However, in this case, cracks are likely to occur in the anodized coating when the temperature of the part rises during use, which may actually result in a decrease in corrosion resistance. Therefore, parts treated by the coating formation method of Patent Document 1 have limitations in terms of increasing the maximum operating temperature, i.e., the maximum temperature expected in the environment in which the part will be used, while maintaining high corrosion resistance.

[0007] The present invention has been made in view of the above background, and aims to provide a surface-treated aluminum material and a method for manufacturing the same that can easily increase the maximum use temperature while maintaining high corrosion resistance.

[0008] One aspect of the present invention is a surface-treated aluminum material having a base material made of aluminum or an aluminum alloy and a protective coating formed on the base material, wherein the protective coating comprises an oxide layer made of 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, and when the surface-treated aluminum material is heated at a temperature of 200°C for 1 hour and subjected to a SWAAT test by a method in accordance with ASTM-G85-A3, the number of corrosion areas that occur on the surface of the surface-treated aluminum material and reach the base material 48 hours after the start of the test is 1.0 / cm 2 The following surface-treated aluminum materials are available.

[0009] Another aspect of the present invention is a method for producing a surface-treated aluminum material according to the above aspect, comprising the steps of: anodizing the base material to form the oxide layer having pores on the base material; heating the base material and the oxide layer at a temperature of 100°C or higher and 350°C or lower; and bringing the oxide layer into contact with a sealing agent to form the hydrated oxide layer on the oxide layer and seal the pores.

[0010] The surface-treated aluminum material (hereinafter referred to as "aluminum material") has a protective coating comprising the oxide layer and the hydrated oxide layer on the surface of the base material. When the surface-treated aluminum material is heated at a temperature of 200°C for 1 hour and subjected to a SWAAT test in accordance with ASTM-G85-A3, the number of corrosion areas that have developed on the surface of the surface-treated aluminum material and reached the base material at 48 hours after the start of the test is 1.0 / cm. 2The aluminum material having these properties can suppress the occurrence of cracks even when the temperature rises. Therefore, the aluminum material can easily increase its maximum use temperature while maintaining high corrosion resistance.

[0011] In addition, in the method for producing an aluminum material, the base material is anodized, and then the oxide layer formed by the anodization is heated at a temperature within the specific range. By heating the oxide layer before sealing the pores in the oxide layer, the internal stress generated during the formation of the oxide layer can be alleviated. After the internal stress in the oxide layer is alleviated, the oxide layer is brought into contact with a sealing agent to form a hydrated oxide layer on the oxide layer and seal the pores. This suppresses the occurrence of cracks even when the temperature of the aluminum material rises, and allows the aluminum material to maintain high corrosion resistance in high-temperature environments.

[0012] As described above, according to the above-described aspects, it is possible to provide a surface-treated aluminum material and a method for manufacturing the same that can easily increase the maximum use temperature while maintaining high corrosion resistance.

[0013] Fig. 1 is a cross-sectional view of a surface-treated aluminum material in an example. Fig. 2 is a cross-sectional view of a base material on which an oxide layer has been formed in the manufacturing process of the surface-treated aluminum material in an example.

[0014] (Aluminum Material) The base material of the aluminum material is made of aluminum or an aluminum alloy. The shape of the base material is not particularly limited, and can take various shapes depending on the application of the aluminum material. For example, the base material may be a wrought material such as a rolled plate or an extruded material, or may be a cast material or a forged material. When the base material has a plate shape, the thickness of the base material is not particularly limited. More specifically, the base material may be, for example, a cold-rolled plate having a thickness of about 1 mm, or a hot-rolled plate having a thickness of about 50 mm.

[0015] The material of the base material can be appropriately selected from the group consisting of aluminum and aluminum alloys depending on the application of the aluminum material. More specifically, the aluminum constituting the base material can be, for example, 1000 series aluminum. The aluminum alloy constituting the base material can be, for example, 2000 series aluminum alloys, 3000 series aluminum alloys, 4000 series aluminum alloys, 5000 series aluminum alloys, 6000 series aluminum alloys, 7000 series aluminum alloys, and 8000 series aluminum alloys. The base material may also be a clad material in which two or more layers having different chemical compositions are laminated.

[0016] A protective coating is provided on the base material, the protective coating including an oxide layer made of aluminum oxide and laminated on the base material, and a hydrated oxide layer containing a hydrated oxide of aluminum and laminated on the oxide layer. More specifically, the hydrated oxide layer may be made of a hydrated oxide of aluminum. The hydrated oxide layer may also contain a hydrated oxide and a metal salt and / or a metal oxide. The protective coating can be obtained, for example, by anodizing the base material to form an oxide layer with numerous pores on the surface of the base material, followed by sealing the pores in the oxide layer with the hydrated oxide layer. Such a protective coating has excellent corrosion resistance because the pores are sealed. Therefore, forming the protective coating on the base material can improve the corrosion resistance of the aluminum material.

[0017] The thickness of the protective coating is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 10 μm or more. In this case, the corrosion resistance of the aluminum material can be further improved. From the viewpoint of corrosion resistance, there is no particular upper limit to the thickness of the protective coating, but the upper limit of the thickness of the protective coating in terms of production is, for example, 200 μm. From the viewpoint of further increasing the productivity of the aluminum material, the thickness of the protective coating is preferably 60 μm or less.

[0018] When the aluminum material is heated at a temperature of 200°C for 1 hour and then subjected to a SWAAT test in accordance with ASTM-G85-A3, the number of corrosion areas that have developed on the surface of the aluminum material and reached the base material 48 hours after the start of the test is 1.0 / cm 2 The aluminum material having these properties can suppress the occurrence of cracks even when used at high temperatures, and can improve corrosion resistance at high temperatures. Therefore, the aluminum material can easily increase the maximum use temperature while maintaining high corrosion resistance.

[0019] From the viewpoint of more easily increasing the maximum use temperature of the aluminum material, when the SWAAT test is performed under the specific conditions, the number of corrosion parts that occur on the surface of the aluminum material and reach the base material after 48 hours from the start of the test is 0.80 parts / cm 2 Preferably, the number of particles is 0.60 / cm or less. 2 More preferably, it is 0.50 particles / cm or less. 2 More preferably, it is 0.30 particles / cm or less. 2 It is particularly preferable that the number of particles is 0.10 particles / cm or less. 2 Most preferably, the following:

[0020] The specific test method for the SWAAT test and the method for calculating the number of corroded areas are as follows. First, a corrosion test surface is set on a portion of the surface of a protective coating on an aluminum material, and the area on the surface of the protective coating other than the corrosion test surface is covered with masking tape. Next, the aluminum material is placed in a corrosion tester with the corrosion test surface facing up. Thereafter, while maintaining the temperature inside the tester's tank at 49±2°C, the test liquid is continuously sprayed onto the corrosion test surface for 0.5 hours. The test liquid used in the SWAAT test is an aqueous solution with a pH of 2.8 to 3.0, prepared by adding acetic acid to an artificial seawater solution having a composition in accordance with ASTM D1141-98. The spray rate of the test liquid is 1.0 ml / 80 cm. 2 / h or more 2.0ml / 80cm 2 / h or less.

[0021] After spraying the test liquid on the corrosion test surface for 0.5 hours, the spraying of the test liquid is stopped and the aluminum material is left to stand in the tester for 1.5 hours. The temperature inside the tester's chamber at this time is 49±2°C, and the relative humidity inside the chamber is 98% RH or higher. The spraying of the test liquid and leaving the aluminum material to stand are then repeated, and the SWAAT test is terminated when 48 hours have elapsed since the start of the test.

[0022] After the SWAAT test is completed, the aluminum material is removed from the test machine, washed with water, and then dried. The aluminum material is then immersed in concentrated nitric acid to remove corrosion products generated by the SWAAT test. All corroded areas that appear on the corrosion test surface are then observed using a microscope to determine whether the base material is exposed at the bottom of the corroded areas. The number of corroded areas with exposed base material at the bottom is then counted. The number of corroded areas with exposed base material (unit: pieces) obtained through the above is multiplied by the area of ​​the corrosion test surface (unit: cm). 2 ) to obtain the number of corroded areas (unit: pieces / cm) that have reached the base material after the SWAAT test. 2 ) can be calculated.

[0023] When the aluminum material is heated at a temperature of 200°C for 1 hour and then subjected to a CASS test according to the method specified in JIS H8502:1999, the number of corrosion areas that have occurred on the surface of the aluminum material and reached the base material 24 hours after the start of the test is 2.0 / cm 2 It is preferable that the maximum service temperature is equal to or less than 100°C. An aluminum material having such properties can suppress the occurrence of cracks even when used at high temperatures, and can further improve corrosion resistance at high temperatures. Therefore, an aluminum material having such properties can more easily increase the maximum service temperature while maintaining high corrosion resistance.

[0024] From the viewpoint of more easily increasing the maximum use temperature of the aluminum material, when a CASS test is performed under the specific conditions, the number of corrosion parts that occur on the surface of the aluminum material and reach the base material after 24 hours from the start of the test is 1.8 parts / cm 2 Preferably, the number is 1.6 or less per cm 2More preferably, it is 1.4 particles / cm or less. 2 More preferably, it is 1.2 particles / cm or less. 2 It is particularly preferable that the value is 1.0 / cm or less. 2 Most preferably, the following:

[0025] The specific test method for the CASS test and the method for calculating the number of corroded areas are as follows. First, a corrosion test surface is set on a portion of the surface of a protective coating on an aluminum material, and the area of ​​the protective coating surface other than the corrosion test surface is covered with masking tape. Next, the aluminum material is placed in a corrosion tester with the corrosion test surface facing up. Thereafter, the temperature inside the tester's tank is maintained at 50±2°C, and the test liquid is continuously sprayed onto the corrosion test surface. The CASS test is terminated when 24 hours have elapsed since the start of the test. The test liquid used in the CASS test is an aqueous solution with a pH of 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 approximately 1 mL / L of acetic acid. The test liquid is sprayed at a rate of 1.0 ml / 80 cm. 2 / h or more 2.0ml / 80cm 2 / h or less.

[0026] After the CASS test is completed, the aluminum material is removed from the test machine, washed with water, and then dried. The aluminum material is then immersed in concentrated nitric acid to remove corrosion products generated by the CASS test. All corroded areas that appear on the corrosion test surface are then observed using a microscope to determine whether the base material is exposed at the bottom of the corroded areas. The number of corroded areas with exposed base material at the bottom is then counted. The number of corroded areas with exposed base material (unit: pieces) obtained through the above is multiplied by the area of ​​the corrosion test surface (unit: cm). 2 ) to obtain the number of corroded areas that reached the base material after the CASS test (unit: pieces / cm 2 ) can be calculated.

[0027] When a sealing test was performed according to the method specified in JIS H8683-2:2013, the mass loss per unit area of ​​the aluminum material was 0.3 g / dm 2 In such an aluminum material, the pores of the oxide layer are sufficiently sealed by the hydrated oxide layer, so that the corrosion resistance of the aluminum material can be more reliably improved.

[0028] The specific method for the pore sealing test is as follows. First, 35 mL of phosphoric acid and 20 g of chromic anhydride are dissolved in water to prepare 1 L of test solution. Next, a test piece including a protective coating is taken from the aluminum material, and the area of ​​the protective coating on the test piece is measured. After removing any dirt from the surface of this test piece, the mass of the test piece is measured. Thereafter, the test piece is immersed in the test solution maintained at a temperature of 38°C ± 1°C for 15 minutes ± 5 seconds.

[0029] After the test piece has been immersed in the test solution, it is washed with running water and then with deionized or distilled water. After the test piece has been washed, it is thoroughly dried and its mass is measured.

[0030] The area A (unit: dm ２ ), the mass m of the test piece before immersion in the test liquid １ (unit: g) and the mass m of the test piece after immersion in the test liquid ２ (unit: g) and calculated the mass loss per unit area δ based on the following formula (1): Ａ (unit: g / dm ２ ) can be calculated. Ａ = (m １ -m ２ ) / A...(1)

[0031] As mentioned above, the aluminum material can easily increase the maximum operating temperature while maintaining high corrosion resistance. Therefore, the aluminum material is suitable for use in components that become hot during use, such as cover components provided around the fans of cooking appliances, metal housings of kitchen equipment, and components for semiconductor manufacturing equipment. More specifically, examples of components for semiconductor manufacturing equipment include chambers and components arranged within chambers in semiconductor manufacturing equipment such as film deposition equipment and etching equipment. Examples of kitchen equipment include cooking appliances such as ovens, microwave ovens, gas stoves, and fryers, as well as hot food showcases.

[0032] (Method for manufacturing aluminum material) When manufacturing the surface-treated aluminum material, first, a base material made of aluminum or an aluminum alloy is prepared. The method for manufacturing the base material is not particularly limited, and known methods can be used. For example, the base material may be manufactured by a method that appropriately combines casting, rolling, and heat treatment. Either DC casting or continuous casting may be used as the casting method for the base material.

[0033] Furthermore, after the base material is manufactured, pretreatments for the anodizing treatment, such as degreasing, etching, desmutting, polishing, and grinding, may be performed as needed before the anodizing treatment. Next, the base material is anodized to form the oxide layer having pores on the base material. In the anodizing treatment, the base material and the counter electrode are immersed in an electrolyte, and a direct current is passed between the base material and the counter electrode to form the oxide layer on the surface of the base material. The oxide layer formed in this manner is composed of an aluminum oxide such as alumina and has numerous pores.

[0034] The electrolytic solution used in the anodizing treatment may be, for example, an acidic electrolytic solution containing an electrolyte such as sulfuric acid or phosphoric acid, or an alkaline electrolytic solution containing an electrolyte such as sodium metaborate. The electrolytic solution used in the anodizing treatment preferably contains an inorganic electrolyte consisting of inorganic cations such as metal ions or ammonium ions and one or more anions selected from the group consisting of sulfate ions, phosphate ions, and borate ions. By performing the anodizing treatment using an electrolytic solution containing an inorganic electrolyte, an oxide layer having a desired structure can be more easily formed.

[0035] The current density of the direct current in the anodizing treatment is, for example, 1 mA / cm ２ 100mA / cm or more ２ The temperature of the electrolytic solution in the anodizing treatment can be appropriately set within the range of 0°C or higher and 40°C or lower.

[0036] The thickness of the oxide layer formed in the anodizing treatment is preferably 2 μm or more. By making the thickness of the oxide layer 2 μm or more, the thickness of the protective coating obtained after sealing can be made sufficiently thick, and an aluminum material having excellent corrosion resistance and heat resistance can be more easily obtained.

[0037] In the manufacturing method, after anodizing, 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 after anodizing and before sealing the pores in the oxide layer, the internal stress in the oxide layer can be alleviated. Then, by sealing the pores after alleviating the internal stress in the oxide layer, the internal stress in the protective coating after sealing can be reduced. As a result, the occurrence of cracks in the protective coating when heated can be suppressed, and the corrosion resistance of the aluminum material at high temperatures can be improved.

[0038] If the heating temperature of the oxide layer is less than 100°C, the internal stress of the oxide layer will not be sufficiently alleviated, and cracks will occur in the protective coating when the temperature of the aluminum material increases, which may result in a loss of corrosion resistance. On the other hand, if the heating temperature of the oxide layer exceeds 350°C, the oxide layer will not be able to follow the thermal expansion of the base material, which may result in cracks in the protective coating. 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, even more preferably 180°C or higher and 290°C or lower, and particularly preferably 200°C or higher and 280°C or lower.

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

[0040] Furthermore, the heating temperature of the oxide layer is preferably equal to or higher than the maximum use temperature of the surface-treated aluminum material, which more reliably suppresses the occurrence of cracks in the surface-treated aluminum material and more reliably improves corrosion resistance at high temperatures.

[0041] Although the reason why the aforementioned effect is obtained by setting the heating temperature of the oxide layer at or above the maximum use temperature of the surface-treated aluminum material is not entirely clear, the following reason is thought to be the case. That is, when the oxide layer is heated in the method for producing an aluminum material, it is thought that among the strains present in the oxide layer, strains having an energy level below the heating temperature of the oxide layer are released, thereby alleviating internal stress. Therefore, when the temperature of the surface-treated aluminum material obtained by the above-mentioned production method is below the heating temperature of the oxide layer, it is thought that the oxide layer is in a state where no strain that should be released is present. Therefore, it is thought that by setting the heating temperature of the oxide layer at or above the maximum use temperature of the surface-treated aluminum material, it is possible to suppress the occurrence of cracks due to the release of strain in the oxide layer.

[0042] After heating the oxide layer, the oxide layer is brought into contact with a sealing agent. This forms a hydrated oxide layer on the oxide layer, and the pores are sealed by the hydrated oxide layer. Examples of sealing agents include hot water or steam at a temperature of 80°C or higher, and aqueous solutions containing ions of one or more metal elements selected from the group consisting of 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). When the sealing treatment is performed using hot water or steam, a hydrated oxide layer made of hydrated aluminum oxide can be formed on the oxide layer.

[0043] Furthermore, when sealing is performed using an aqueous solution containing ions of the metal element, a hydrated oxide layer containing a hydrated oxide of aluminum and a salt and / or oxide of the metal element can be formed on the oxide layer. The metal element may exist as a metal ion in the aqueous solution or as a complex ion. More specifically, the sealing agent may be an aqueous solution of a metal salt containing the metal element, such as an aqueous nickel acetate solution, an aqueous cobalt acetate solution, an aqueous chromate solution, or an aqueous silicate solution.

[0044] From the viewpoint of more easily obtaining an aluminum material having excellent corrosion resistance and heat resistance, it is preferable that the sealing agent be hot water having a temperature of 80°C or higher. Furthermore, by sealing the pores of the oxide layer using hot water, a hydrated oxide layer containing no metal salts can be formed on the oxide layer. For example, when the aluminum material is used as a component for semiconductor manufacturing equipment, the metal salts in the hydrated oxide layer may cause contamination inside the equipment. Therefore, by using hot water as a sealing agent and forming a hydrated oxide layer containing no metal salts, an aluminum material suitable for use as a component for semiconductor manufacturing equipment can be easily obtained. When hot water is used as a sealing agent, it is more preferable to seal the pores of the oxide layer by contacting the oxide layer with hot water having a temperature of 80°C or higher as a sealing agent for 10 minutes or more but less than 120 minutes.

[0045] An example of the surface-treated aluminum material and its manufacturing method will be described with reference to Figures 1 and 2. As shown in Figure 1, the surface-treated aluminum material 1 of this example has a base material 2 made of aluminum or an aluminum alloy, and a protective coating 3 formed on the base material. The protective coating 3 has an oxide layer 31 made of aluminum oxide that covers the base material 2, and a hydrated oxide layer 32 containing hydrated oxide of aluminum that covers the oxide layer 31. When the surface-treated aluminum material 1 was heated at a temperature of 200°C for 1 hour and subjected to a SWAAT test using a method in accordance with ASTM-G85-A3, the number of corrosion areas that had developed on the surface of the surface-treated aluminum material 1 and reached the base material 2 48 hours after the start of the test was 1.0 / cm. 2 The following is the result.

[0046] In producing the aluminum material 1 of this example, first, an oxide layer 31 having pores 311 is formed on the base material 2 by anodizing the base material 2 as shown in Fig. 2. 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 relieve internal stress in the oxide layer 31. Then, the oxide layer 31 is brought into contact with a sealing agent to form a hydrated oxide layer 32 on the oxide layer 31 and seal the pores 311, thereby obtaining the aluminum material 1.

[0047] Table 1 shows specific examples of aluminum material 1 (test materials A1 to A3). Test materials A1 to A3 are manufactured, for example, as follows. First, an aluminum plate having a thickness of 1 mm and a chemical composition represented by alloy number A6016 is prepared as base material 2. This base material 2 is subjected to a pretreatment for anodizing. Specifically, as a pretreatment, an alkali etching treatment is performed by immersing the base material 2 in a sodium hydroxide aqueous solution with a concentration of 5% by mass and a temperature of 55°C. Subsequently, a desmutting treatment is performed by immersing the base material 2 in nitric acid with a concentration of 30% by mass. Subsequently, a chemical polishing treatment is performed by immersing the base material 2 in a mixed solution of phosphoric acid and sulfuric acid at a volume ratio of phosphoric acid:sulfuric acid = 7:3 at a temperature of 85°C. After the chemical polishing treatment, a desmutting treatment is performed again under the same conditions as those described above.

[0048] After the base material 2 has been pretreated as described above, the base material 2 is anodized to form an oxide layer 31 on the surface of the base material 2. The electrolyte used in the anodization is a sulfuric acid aqueous solution with a concentration of 15% by mass, and the temperature of the electrolyte is 5°C. The current density in the anodization is 10 mA / cm ２ The anodizing treatment was carried out under the above-mentioned conditions for 60 minutes. The oxide layer 31 thus formed is a porous alumite coating, and has a large number of pores 311, as shown in Fig. 2. The thickness of the oxide layer 31 formed by anodizing treatment under the above-mentioned conditions is approximately 15 µm.

[0049] After the anodizing treatment, the base material 2 is heated in a heating furnace to relieve 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, that is, 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] Thereafter, the base material 2 provided with the oxide layer 31 is immersed in hot water at a temperature of 100°C as a sealant for 60 minutes, thereby forming a hydrated oxide layer 32 made of a hydrated oxide of aluminum on the oxide layer 31, and sealing the pores 311 in the oxide layer 31 with the hydrated oxide layer 32. In this manner, test materials A1 to A3 shown in Table 1 can be obtained. When the pores 311 in the oxide layer 31 are sealed under these conditions, the mass loss per unit area of ​​the aluminum material 1 is approximately 0.01 g / dm when a sealing test is performed according to the method specified in JIS H8683-2:2013. 2 This becomes:

[0051] Test materials B1 and B2 shown in Table 1 are test materials for comparison with test materials A1 to A3. The manufacturing method of test material B1 is the same as that of test material A1, except that after forming an oxide layer 31 on a base material 2, the oxide layer 31 is brought into contact with a sealing agent without being heated. The manufacturing method of test material B2 is the same as that of test material B1, except that the heating temperature and heating time of the oxide layer 31 are changed as shown in Table 1.

[0052] The results of the SWAAT test and the CASS test using the test materials A1 to A3 and the test materials B1 to B2 are shown in Table 1. The detailed methods of the SWAAT test and the CASS test are as follows.

[0053] [SWAAT Test] First, each test material is heated at 200°C for 1 hour. After heating, a rectangular corrosion test surface measuring 5 cm in length and 10 cm in width is set on the surface of the protective coating of the heated test material, and the area of ​​the protective coating surface other than the corrosion test surface is covered with masking tape. Then, the test material is placed in a corrosion tester with the corrosion test surface facing up, and the SWAAT test is performed using a method in accordance with ASTM-G85-A3. 48 hours after the start of the test, the test material is removed from the corrosion tester. The test material is washed with pure water and then completely dried using a dryer. The test material is then immersed in concentrated nitric acid at 25°C for 5 minutes to remove corrosion products that have formed on the corrosion test surface.

[0054] Next, all corroded areas that have occurred on the corrosion test surface are observed using a microscope to determine whether or not the base material is exposed at the bottom of the corroded areas. Then, the number of corroded areas where the base material is exposed at the bottom is counted. The number of corroded areas where the base material is exposed (unit: pieces) obtained as a result of the above is multiplied by the area (unit: cm) of the corrosion test surface. 2 ) to obtain the number of corroded areas (unit: pieces / cm) that have reached the base material after the SWAAT test. 2 ) can be calculated.

[0055] [CASS Test] First, each test material is heated at 200°C for 1 hour. After heating, a rectangular corrosion test surface measuring 5 cm in length and 10 cm in width is set on the surface of the protective coating of the heated test material, and the area of ​​the protective coating surface other than the corrosion test surface is covered with masking tape. Then, the test material is placed in a corrosion tester with the corrosion test surface facing up, and a CASS test is performed according to the method specified in JIS H8502:1999. 24 hours after the start of the test, the test material is removed from the corrosion tester. The test material is washed with pure water and then completely dried using a dryer. Then, the test material is immersed in concentrated nitric acid at 25°C for 5 minutes to remove corrosion products that have formed on the corrosion test surface.

[0056] Next, all corroded areas that have occurred on the corrosion test surface are observed using a microscope to determine whether or not the base material is exposed at the bottom of the corroded areas. Then, the number of corroded areas where the base material is exposed at the bottom is counted. The number of corroded areas where the base material is exposed (unit: pieces) obtained as a result of the above is multiplied by the area (unit: cm) of the corrosion test surface. 2 ) to obtain the number of corroded areas that have reached the base material after the CASS test (unit: pieces / cm 2 ) can be calculated.

[0057]

[0058] As shown in Table 1, for test materials A1 to A3, after an oxide layer was formed on the base material, the oxide layer was heated at a temperature within the above-mentioned specific range before the pores in the oxide layer were sealed. Therefore, when these test materials were heated at a temperature of 200°C for 1 hour and then subjected to a SWAAT test in accordance with ASTM-G85-A3, the number of corrosion areas that had developed on the surface of the surface-treated aluminum material and reached the base material 48 hours after the start of the test was 1.0 / cm. 2 The aluminum material having these characteristics can suppress the occurrence of cracks even when the temperature rises. Therefore, the aluminum material can easily increase its maximum use temperature while maintaining high corrosion resistance.

[0059] On the other hand, in the case of test material B1, after an oxide layer is formed on the base material, the pores are sealed without heating the oxide layer, so when the SWAAT test is performed under the specific conditions, a large number of corrosion areas appear on the surface of the surface-treated aluminum material and reach the base material. Therefore, it is difficult to increase the maximum use temperature of test material B1.

[0060] For test material B2, the heating time for heating the oxide layer was too short, so when the SWAAT test was performed under the specific conditions, a large number of corrosion areas appeared on the surface of the surface-treated aluminum material and reached the base material. Therefore, it was difficult to increase the maximum use temperature of test material B2.

[0061] The above has described aspects of the surface-treated aluminum material and the method for manufacturing the same according to the present invention based on the examples, but the specific aspects of the surface-treated aluminum material and the method for manufacturing the same according to the present invention are not limited to the aspects of the examples, and the configuration can be changed as appropriate within the scope that does not impair the intent of the present invention.

[0062] For example, the surface-treated aluminum material according to the present invention can take the following forms [1] to [4].

[0063] [1] A surface-treated aluminum material having a base material made of aluminum or an aluminum alloy and a protective coating formed on the base material, wherein the protective coating comprises an oxide layer made of 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, wherein when the surface-treated aluminum material is heated at a temperature of 200°C for 1 hour and subjected to a SWAAT test in accordance with a method in accordance with ASTM-G85-A3, the number of corrosion areas that develop on the surface of the surface-treated aluminum material and reach the base material 48 hours after the start of the test is 1.0 / cm 2 The surface-treated aluminum material is as follows:

[0064] [2] When the surface-treated aluminum material is heated at a temperature of 200°C for 1 hour and subjected to a CASS test according to the method specified in JIS H8502:1999, the number of corrosion areas that have occurred on the surface of the surface-treated aluminum material and reached the base material 24 hours after the start of the test is 2.0 / cm 2 [3] The surface-treated aluminum material according to [1] or [2], wherein the protective coating has a thickness of 5 μm or more and 60 μm or less.

[0065] [4] When a sealing test was performed according to the method specified in JIS H8683-2:2013, the mass loss per unit area was 0.3 g / dm 2 The surface-treated aluminum material according to any one of [1] to [3] below.

[0066] Furthermore, the method for producing a surface-treated aluminum material according to the present invention can take the following aspects [5] to [9].

[0067] [5] A method for producing a surface-treated aluminum material according to any one of [1] to [4], comprising the steps of: anodizing the base material to form the oxide layer having pores on the base material; heating the base material and the oxide layer at a temperature of 100°C or higher and 350°C or lower; and bringing the oxide layer into contact with a sealing agent to form the hydrated oxide layer on the oxide layer and seal the pores.

[0068] [6] The method for producing a surface-treated aluminum material according to [5], wherein the heating time from the start of heating the oxide layer to the end of heating is 3 minutes or more. [7] The method for producing a surface-treated aluminum material according to [5] or [6], wherein the electrolytic solution used in the anodizing treatment contains an inorganic electrolyte comprising inorganic cations and one or more anions selected from the group consisting of sulfate ions, phosphate ions, and borate ions.

[0069] [8] The method for producing a surface-treated aluminum material according to any one of [5] to [7], wherein the sealing agent is hot water having a temperature of 80°C or higher, an aqueous solution containing ions of one or more metal elements selected from the group consisting 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 producing a surface-treated aluminum material according to [8], wherein the sealing is performed by contacting the oxide layer with hot water of 80°C or higher serving as the sealing agent for 10 minutes or more but less than 120 minutes.

Claims

1. A surface-treated aluminum material having a base material made of aluminum or an aluminum alloy and a protective film formed on the base material, wherein the protective film comprises an oxide layer made of an oxide of aluminum covering the base material, and a hydrated oxide layer containing a hydrated oxide of aluminum covering the oxide layer, and when the surface-treated aluminum material is heated at a temperature of 200°C for 1 hour and subjected to a SWAAT test according to a method in accordance with ASTM-G85-A3, the number of corrosion parts that have developed on the surface of the surface-treated aluminum material and reached the base material 48 hours after the start of the test is 1.0 piece / cm 2 The surface-treated aluminum material is as follows.

2. When the surface-treated aluminum material is heated at 200°C for 1 hour and then subjected to a CASS test according to the method specified in JIS H8502:1999, the number of corrosion areas that have developed on the surface of the surface-treated aluminum material and reached the base material 24 hours after the start of the test is 2.0 pieces / cm 2 The surface-treated aluminum material according to claim 1, wherein:

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

4. When a sealing test was conducted according to the method specified in JIS H8683-2:2013, the mass loss per unit area was 0.3 g / dm 2 The surface-treated aluminum material according to any one of claims 1 to 3, wherein:

5. A method for producing a surface-treated aluminum material according to any one of claims 1 to 4, comprising the steps of: anodizing the base material to form the oxide layer having pores on the base material; heating the base material and the oxide layer at a temperature of 100°C or higher and 350°C or lower; and contacting the oxide layer with a sealing agent to form the hydrated oxide layer on the oxide layer and seal the pores.

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

7. A method for producing a surface-treated aluminum material as described in claim 5 or 6, wherein the electrolytic solution used in the anodizing treatment contains an inorganic electrolyte consisting of inorganic cations and one or more anions selected from the group consisting of sulfate ions, phosphate ions and borate ions.

8. A method for producing a surface-treated aluminum material according to any one of claims 5 to 7, wherein the sealing agent is hot water having a temperature of 80°C or higher, an aqueous solution containing ions of one or more metal elements selected from the group consisting 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 producing a surface-treated aluminum material according to claim 8, wherein the sealing step comprises contacting the oxide layer with hot water of 80° C. or higher as the sealing agent for 10 minutes or more and less than 120 minutes.