ALUMINUM COATED MATERIAL AND METHOD FOR PRODUCING SAME

Abstract

Provided is a coated aluminum material having a coating film on a surface of an aluminum material, and capable of exerting excellent corrosion resistance even under severe use conditions while being chromium-free. The coating film is formed on a surface of the aluminum material with a silica-containing film including a water dispersible silica, a phosphorus compound, and a silane coupling agent provided therebetween. The silica-containing film includes 0.5 to 35 mass % of a silane coupling agent, and has Si and P contents of 2 to 60, and 0.1 to 6.0 mg/m.sup.2, respectively, and a P/Si mass ratio of P content and Si content of 0.02 to 0.15. Further, provided is a method for producing such a coated aluminum material.

Claims

1. A coated aluminum material comprising: an aluminum material including aluminum or an aluminum alloy, and a coating film formed on a surface of the aluminum material with a silica-containing film including a water dispersible silica, a phosphorus compound, and a silane coupling agent provided thereunder, wherein the silica-containing film includes the silane coupling agent in a ratio of 0.5 to 35 mass %, and has a Si content falling within the range of 2 to 60 mg/m.sup.2, a P content falling within the range of 0.1 to 6.0 mg/m.sup.2, and a P/Si mass ratio of the P content to the Si content falling within the range of 0.02 to 0.15.

2. A coated aluminum material according to claim 1, wherein the water dispersible silica is a colloidal silica.

3. A method for producing a coated aluminum material, the coated aluminum material including an aluminum material including aluminum or an aluminum alloy, and a coating film formed on a surface of the aluminum material with a silica-containing film including a water dispersible silica, a phosphorus compound, and a silane coupling agent provided thereunder, the method, comprising: forming the silica-containing film including the silane coupling agent in a ratio of 0.5 to 35 mass %, and having a Si content falling within the range of 2 to 60 mg/m.sup.2, and a P content falling within the range of 0.1 to 6.0 mg/m.sup.2 on a surface of the aluminum material; and then, forming the coating film on the silica-containing film.

Description

DESCRIPTION OF EMBODIMENTS

[0032] Hereinafter, preferred embodiments of the present invention will be specifically described by way of Examples and Comparative Examples.

Examples 1 to 10 and Comparative Examples 1 to 8

[0033] As an aluminum material, an aluminum sheet (JIS 5052-H18) with dimensions of 70 mm150 mm1.0 mm was prepared. Each prepared aluminum sheet of respective Examples and Comparative Examples was subjected to a pretreatment, a film-forming treatment of a silica-containing film, and formation of a coating film shown below, thereby preparing each aluminum coated material of respective Examples and Comparative Examples.

[0034] [Pretreatment]

[0035] In respective Examples and Comparative Examples, each of the aluminum sheets was subjected to the following pretreatment.

[0036] Namely, a degreasing treatment in which the aluminum sheet was immersed in a 2 mass % aqueous solution of a degreasing agent (trade name: SURFCLEANER 155 manufactured by NIPPON PAINT Co., Ltd.) containing sodium metasilicate under the conditions of 60 C. and 30 seconds was performed, followed by water washing and drying.

[0037] [Film-Forming Treatment]

[0038] As a treatment solution for forming a silica-containing film, using the colloidal silicas and additive resins, and the like shown in Table 1, the phosphorus compounds, the silane coupling agents, and water or isopropanol (iso-PrOH) as a solvent shown in Table 2, a film-forming treatment solution with each composition shown in Table 2 was prepared.

TABLE-US-00001 TABLE 1 Types of colloidal silica, additive resin, etc. Solid content Average Concentration Particle Dispersion Manufacturer (wt %) Size (nm) medium Colloidal ST-C Nissan 20 10 to 20 Water silica Chemical Corporation ST-O Nissan 20 10 to 21 Water Chemical Corporation ST-UP Nissan 20 40 to 300 Water Chemical chain-shaped Corporation ST-OL Nissan 20 40 to 50 Water Chemical Corporation ST-40 Nissan 40 10 to 20 Water Chemical Corporation IPA-ST Nissan 30 10 to 20 iso-PrOH Chemical Corporation Additive Acumer manufactured 25 Organic binder: resin, etc. 1510 by Rohm & Polyacrylic acid Haas Co. Pentalite KOEI CHEMICAL Cross linker: COMPANY Ltd. Pentaerythritol MODEPICS 302 ARAKAWA 33 Acrylic modified epoxy CHEMICAL resin emulsion INDUSTRIES Ltd.

TABLE-US-00002 TABLE 2 Composition of film-forming treatment solution Examples 1 2 3 4 5 6 7 8 9 Colloidal ST-C 4.5 silica ST-O 15 15 15 ST-OL 48 ST-UP 0.9 9 ST-40 IPA-ST 15 15 Phosphorus Phosphoric 1.8 0.3 0.13 0.02 0.4 0.4 0.2 0.4 0.2 compound acid Silane KBE403 (epoxy 0.2 0.1 coupling group) agent KBE803 (thiol 0.3 0.03 1 0.1 1.6 0.1 group) KBE903 (amino 0.05 group) Additive Acumer 1510 resin, etc. Pentalite MODEPICS302 The balance Water 50 84.4 95.32 5.0 90.5 10.0 84.7 10.0 84.7 iso-PrOH 94.05 73.6 73.0 Example Comparative Exaraples 10 1 2 3 4 5 6 7 8 Colloidal ST-C silica ST-O 2 15 50 50 ST-OL 12 ST-UP 0.45 9 ST-40 50 IPA-ST 3.5 Phosphorus Phosphoric 0.01 0.1 0.3 0.1 0.3 0.3 0.5 0.3 compound acid Silane KBE403 (epoxy 0.1 coupling group) agent KBE803 (thiol 0.05 2.0 0.3 0.3 group) KBE903 (amino 10 group) Additive Acumer 1510 0.1 resin, etc. Pentalite 0.003 MODEPICS302 50 The balance Water 5 97.9 82.7 5.0 49.4 49.4 90.4 87.6 iso-PrOH 94.49 91.4

[0039] [Manufacturing of Aluminum Coated Material]

[0040] In each of Examples 1, 3, and 5 to 9, and Comparative Examples 1 to 7, after completion of the pretreatment, using a bar coater, the film-forming treatment solution with each composition shown in Table 2 was coated so as to achieve a coating amount of 1 g/m.sup.2. Then, at a peak temperature (PMT: Peak metal temperature) of 180 C., drying was performed for 1 minute, thereby forming a silica-containing film on a surface of the aluminum sheet.

[0041] Further, in Example 2, after completion of the pretreatment, using a bar coater, the film-forming treatment solution with each composition shown in Table 2 was coated so as to achieve a coating amount of 2.5 g/m.sup.2. Then, at a PMT of 180 C., drying was performed for 1 minute, thereby forming a silica-containing film on a surface of the aluminum sheet.

[0042] Further, in Example 4, after completion of the pretreatment, using a spray gun, the film-forming treatment solution with each composition shown in Table 2 was coated so as to achieve a coating amount of 25 g/m.sup.2. Then, at a PMT of 180 C., drying was performed for 1 minute, thereby forming a silica-containing film on a surface of the aluminum sheet.

[0043] Further, in Example 10, after completion of the pretreatment, using a spray gun, the film-forming treatment solution with each composition shown in Table 2 was coated so as to achieve a coating amount of 50 g/m.sup.2. Then, at a PMT of 180 C., drying was performed for 1 minute, thereby forming a silica-containing film on a surface of the aluminum sheet.

[0044] Further, in Comparative Example 8, after completion of the pretreatment, using a bar coater, the film-forming treatment solution with each composition shown in Table 2 was coated so as to achieve a coating amount of 1 g/m.sup.2. Then, at a PMT of 100 C., drying was performed for 1 minute, thereby forming a silica-containing film on a surface of the aluminum sheet.

[0045] As for each silica-containing film of respective Examples and Comparative Examples formed as described above, the silicon content (Si content: mg/m.sup.2) and the phosphorus content (P content: mg/m.sup.2) contained in film unit area were measured by fluorescent X ray analysis, respectively. For this measurement, a silica-containing film was prepared on a 99.999% pure aluminum sheet by the same method as that in respective Examples and Comparative Examples. Thus, the silicon content (Si content: mg/m.sup.2) and the phosphorus content (P content: mg/m.sup.2) contained in unit area of the silica-containing film were subjected to quantitative analysis.

[0046] [Formation of Coating Film]

[0047] For the coating film staked on a surface of the aluminum sheet with the silica-containing film provided therebetween, using the coating film-forming paints shown in Table 3 described below, coating films with respective film thicknesses shown in Table 3 were formed, respectively, in the order of a first layer, a second layer, and a third layer.

TABLE-US-00003 TABLE 3 Coating film-forming paint Name of paint Manufacturer Resin type Color A PrecolorTX4427 BASF Polyester type White B V nit #120 DAI NIPPON TORYO Co., Ltd. Epoxy type Clear C V nit #500 DAI NIPPON TORYO Co., Ltd. Polyester type Clear D V-PET#4000W DAI NIPPON TORYO Co., Ltd. Polyester type Grey E V top H intermediate coat DAI NIPPON TOKYO Co., Ltd. Polyurethane type White F V top H top coat DAI NIPPON TOKYO Co., Ltd. Polyurethane type White

[0048] For each aluminum sheet of respective Examples and Comparative Examples after performing the pretreatment and the film-forming treatment, a coating film was formed in the following manner, thereby preparing each specimen (aluminum coated material) of respective Examples and Comparative Examples.

[0049] In Example 1, a paint A was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 210 C. for 60 seconds to be dried, thereby forming a coating film with a film thickness (total coating film thickness) of 30 m.

[0050] In Example 2, a paint B was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 210 C. for 60 seconds to be dried, thereby forming a coating film with a film thickness of 5 m. Then, a paint E was coated by a spray gun, thereby forming a 50-m coating film, and was baked in a heating furnace set at 80 C. for 5 minutes. Further, a paint F was coated by a spray gun, thereby forming a 50-m coating film, and was baked in a heating furnace set at 80 C. for 10 minutes, resulting in preparation of a specimen (aluminum coated material) with a total coating film thickness of 105 m.

[0051] In Example 3, the paint B was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 210 C. for 40 seconds to be dried, thereby forming a coating film with a film thickness of 10 m. Then, a paint C was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 225 C. for 60 seconds to be dried, thereby forming a coating film with a film thickness of 30 m, resulting in preparation of a specimen (aluminum coated material) with a total coating film thickness of 40 m.

[0052] In Example 4, a paint D was subjected to electrostatic powder coating, and was baked in a heating furnace set at 180 C. for 30 minutes, thereby forming a coating film with a film thickness (total coating film thickness) of 100 m, resulting in preparation of a specimen (aluminum coated material).

[0053] In Example 5, the paint B was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 210 C. for 40 seconds to be dried, thereby forming a coating film with a film thickness of 2 m. Then, the paint A was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 210 C. for 60 seconds to be dried, thereby forming a coating film with a film thickness of 30 m, resulting in preparation of a specimen (aluminum coated material) with a total coating film thickness of 32 m.

[0054] In Example 6, the paint C was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 225 C. for 60 seconds to be dried, thereby forming a coating film with a film thickness (total coating film thickness) of 20 m.

[0055] In Example 7, the paint B was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 225 C. for 60 seconds to be dried, thereby forming a coating film with a film thickness (total coating film thickness) of 5 m, resulting in preparation of a specimen (aluminum coated material).

[0056] In Example 8, the paint C was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 225 C. for 60 seconds to be dried, thereby forming a coating film with a film thickness (total coating film thickness) of 35 m.

[0057] In Example 9, the paint B was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 225 C. for 60 seconds to be dried, thereby forming a coating film with a film thickness (total coating film thickness) of 40 m, resulting in preparation of a specimen (aluminum coated material).

[0058] In Example 10, the paint D was subjected to electrostatic powder coating, and was baked in a heating furnace set at 180 C. for 30 minutes, thereby forming a coating film with a film thickness (total coating film thickness) of 50 m, resulting in preparation of a specimen (aluminum coated material).

[0059] In Comparative Example 1, the paint D was subjected to electrostatic powder coating, and was baked in a furnace set at 180 C. for 30 minutes, thereby forming a coating film with a film thickness (total coating film thickness) of 100 m, resulting in preparation of a specimen (aluminum coated material). The aluminum coated material of Comparative Example 1 has a silica-containing film with substantially the same P/Si mass ratio as that described in Example 2 of PTL 4, and is free from a silane coupling agent.

[0060] In Comparative Example 2, the paint D was subjected to electrostatic powder coating, and was baked in a furnace set at 180 C. for 30 seconds, thereby forming a coating film with a film thickness (total coating film thickness) of 100 m, resulting in preparation of a specimen (aluminum coated material). In Comparative Example 2, the silane coupling agent content exceeds the upper limit value.

[0061] In Comparative Example 3, the paint B was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 210 C. for 40 seconds to be dried, thereby forming a coating film with a film thickness (total coating film thickness) of 5 m, resulting in preparation of a specimen (aluminum coated material). The aluminum coated material of Comparative Example 3 has a silica-containing film with substantially the same P/Si mass ratio as that described in Example 9 of PTL 4, and is free from a silane coupling agent.

[0062] In Comparative Example 4, the paint B was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 210 C. for 40 seconds to be dried, thereby forming a coating film with a film thickness of 5 m. Then, the paint C was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 225 C. for 60 seconds to be dried, thereby forming a coating film with a film thickness of 30 m, resulting in preparation of a specimen (aluminum coated material) with a total film thickness of 35 m. In Comparative Example 4, the P/Si mass ratio is smaller than the lower limit value.

[0063] In Comparative Example 5, the paint B was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 210 C. for 40 seconds to be dried, thereby forming a coating film with a film thickness of 5 m. Then, the paint C was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 225 C. for 60 seconds to be dried, thereby forming a coating film with a film thickness of 10 pin, resulting in preparation of a specimen (aluminum coated material) with a total coating film thickness of 15 m. In Comparative Example 5, the P/Si mass ratio is smaller than the lower limit value.

[0064] In Comparative Example 6, the paint B was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 210 C. for 60 seconds to be dried, thereby forming a coating film with a film thickness of 5 m. Then, the paint E was coated by a spray gun, thereby forming a 50-m coating film, and was baked in a heating furnace set at 80 C. for 5 minutes. Further, the paint F was coated by a spray gun, thereby forming a 50-pin coating film, and was baked in a heating furnace set at 80 C. for 10 minutes, resulting in preparation of a specimen (aluminum coated material) with a total coating film thickness of 105 pin. The aluminum coated material of Comparative Example 6 has a P/Si mass ratio exceeding the upper limit.

[0065] In Comparative Example 7, the paint B was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 210 C. for 40 seconds to be dried, thereby forming a coating film with a film thickness of 5 m. Then, the paint D was subjected to electrostatic powder coating, and was baked in a heating furnace set at 180 C. for 30 minutes, thereby forming a coating film with a film thickness of 50 m, resulting in preparation of a specimen (aluminum coated material) with a total coating film thickness of 55 m. The Comparative Example 7 has a silica-containing film with substantially the same P/Si mass ratio as that described in Example 2 of PTL 5, and is free from a silane coupling agent.

[0066] In Comparative Example 8, the paint B was subjected to bar coat coating, and was subjected to a baking treatment at a PMT of 210 C. for 40 seconds to be dried, thereby forming a coating film with a film thickness of 5 m. Then, the paint D was subjected to electrostatic powder coating, and was baked in a heating furnace set at 180 C. for 30 minutes, thereby forming a coating film with a film thickness of 70 m, resulting in preparation of a specimen (aluminum coated material) with a total coating film thickness of 75 m. The aluminum coated material of Comparative Example 8 includes a silica-containing film in which a phosphorus compound is not added, the P/Si mass ratio is zero (0), and a silane coupling agent is added in an amount exceeding 21 mass %.

[0067] [Corrosion Resistance Test]

[0068] As for each specimen of respective Examples and Comparative Examples prepared in the manner described up to this point, the following salt spray test, wetting test, and boiling water immersion test were performed to examine the adhesion, thereby evaluating the corrosion resistance.

[0069] With the salt spray test, each specimen of respective Examples and Comparative Examples was cross-cut with the method of JIS K 5600, and a 1000-hour test was carried out. With the salt spray test, evaluation was performed with the evaluation criteria of : corrosion, swelling, and the like were not caused at the cut part at all, and the adhesion of the cut part was good, : the corrosion of the cut part was equal to or smaller than 1 mm in size, and swelling was not caused, and the adhesion was good, and X: the corrosion of the cut part was 1 mm or more in size, or abnormal condition such as occurrence of swelling or poor adhesion was caused, in the coating film after 1000 hours.

[0070] With the wetting test, each specimen of respective Examples and Comparative Examples was allowed to stand still in a 50 C. and 95% RH constant temperature constant humidity chamber for 1000 hours. Then, the adhesion of the coating film was evaluated. The adhesion of the coating film was evaluated by rating the case where the area of the cross cut part which had undergone peeling was 5% or less (classification 1 or less) as ; the case of more than 5% and 15% or less as , the case of more than 15% and 35% or less as ; and the case of more than 35% as X with the method of adhesion (cross-cut method) of JIS K 5600.

[0071] With the boiling water immersion test, each specimen of respective Examples and Comparative Examples was immersed in boiling water for 5 hours. Then, in the same manner as with the case of the wetting test, the adhesion of the coating film was evaluated based on the same evaluation criteria.

[0072] The results of the adhesion after the salt spray test, and the wetting test, and the adhesion after the boiling water immersion test are shown in Table 4.

TABLE-US-00004 TABLE 4 Examples 1 2 3 4 5 6 7 8 9 Coating film First layer A B B D B C B C B configuration Second layer E C A Third layer F Coating film First layer 30 5 10 100 2 20 5 35 40 thickness Second layer 50 30 30 (m) Third layer 50 Total coating 30 105 40 100 32 20 5 35 40 film thickness Composition Film mass (mg/m.sup.2) 112.1 88.88 10.6 56.75 22.4 60.4 47.7 64.4 47.7 of silica Si content (mg/m.sup.2) 44.9 36.1 4.26 22.1 8.53 22.7 21.1 23.3 21.1 containing P content (mg/m.sup.2) 4.84 2.01 0.35 1.34 1.07 1.07 0.54 1.07 0.54 film P/Si mass ratio 0.108 0.056 0.082 0.061 0.125 0.047 0.026 0.046 0.026 Si content ratio 40.04 40.58 40.20 38.89 38.06 37.60 44.32 36.15 44.32 (mass %) P content ratio 4.31 2.27 3.29 2.37 4.80 1.78 1.13 1.66 1.13 (mass %) Silane coupling 0.71 8.43 4.71 13.21 4.46 19.87 2.10 24.84 2.10 agent content ratio (mass %) Evaluation of Salt, spray test Corrosion Adhesion after resistance wetting test Adhesion after boiling water immersion test Comparative Examples Ex. 10 1 7 3 4 5 6 7 8 Coating film First layer D D D B B B B B B configuration Second layer C C E D D Third layer F Coating film First layer 50 100 100 5 5 5 5 5 5 thickness Second layer 30 10 50 50 70 (m) Third layer 50 Total coating 50 100 100 5 35 15 105 55 75 film thickness Composition Film mass (mg/m.sup.2) 74.24 4.85 52.55 11.35 105.6 105.6 23.3 26.83 465 of silica Si content(mg/m.sup.2) 24.56 1.87 16.85 4.9 47.1 47.1 8.53 11.2 106 containing P content (mg/m.sup.2) 1.34 0.27 0.81 0.27 0.81 0.81 1.34 0.81 0 film P/Si mass ratio 0.055 0.144 0.048 0.055 0.017 0.017 0.157 0.072 0.000 Si content ratio 33.08 38.48 32.07 43.17 44.62 44.62 36.67 41.74 22.79 (mass %) P content ratio 1.81 5.54 1.53 2.37 0.76 0.76 5.78 3.00 0.00 (mass %) Silane coupling 33.67 0.00 38.05 0.00 2.84 2.84 4.30 0.00 21.51 agent content ratio (mass %) Evaluation of Salt spray test X X X corrosion Adhesion after X X X X X X X resistance wetting test Adhesion after X X X X X X boiling water immersion test