Protective layer structure for coating electrophoretic paint on aluminum alloy part

Abstract

The utility model discloses a protective layer structure for coating an aluminum alloy part with electrophoretic paint. The protective layer structure comprises an aluminum alloy substrate, and a trivalent chromium passivation film and an electrophoretic paint coating which are sequentially prepared on the aluminum alloy substrate from inside to outside. The binding force is tested by a thermal shock method according to GB / T 5270-2005 Metal Covering Layer Electro-Deposition and Chemical Deposition Layer Adhesion Strength Test Method on Metal Matrix, the prepared protective layer is free of blistering and shedding, and the binding force meets the standard requirement. A neutral salt spray test is carried out for 600 h according to GB / T 10125-2021 Artificial Atmosphere Corrosion Test Salt Spray Test, the surface of a sample piece is free of rust, and the prepared protective layer has good corrosion resistance. The protective layer structure for coating the electrophoretic paint on the aluminum alloy part, disclosed by the utility model, has a good market prospect.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of metal surface treatment, specifically relates to a kind of aluminium alloy piece coating electrophoretic paint's protective layer structure. BACKGROUND

[0002] Due to the low specific gravity of aluminum alloy and considerable hardness, it has wide application value in aerospace, aviation, instruments and meters, electrical appliances, computers, automobiles and other aspects. But aluminum alloy is prone to local corrosion in humid environment, which affects the appearance quality of aluminum alloy parts. In order to improve its corrosion resistance, surface treatment is needed for aluminum alloy. At present, the surface treatment methods of aluminum alloy mainly include anodic oxidation, electroplating and passivation.

[0003] The most commonly used method for aluminum alloy surface treatment is sulfuric acid anodizing, and HB 5362-1986 "Quality Inspection of Corrosion Resistance of Protective Layer of Commonly Used Metals for Aircraft" requires that there is no rust after 336h neutral salt spray test after aluminum alloy sulfuric acid anodizing and sealing treatment. Currently, nickel salt is usually used to seal the pores of anodized film on aluminum alloy civilian products. This protective process has the problem of nickel pollution [1] .

[0004] Preparation of passivation film on the surface of aluminum alloy by chromate passivation process can obtain high corrosion resistance, but hexavalent chromium is highly toxic, and its use has been subject to increasingly strict restrictions.

[0005] Electroplating method is used to prepare protective layer on the surface of aluminum alloy, which has high cost and is mainly used in high-end manufacturing industries such as aerospace, and is not widely used in civilian products.

[0006] The preparation of chemical conversion film on the surface of aluminum alloy by rare earth salt is a new method being studied in the industry, and the developed process is not mature enough at present.

[0007] In order to develop a new type of corrosion protection system that is non-toxic, environmentally friendly and comparable to chromate passivation, researchers have made a lot of research on hexavalent chromium-free treatment on the surface of aluminum alloy. Trivalent chromium passivation treatment has much lower toxicity than chromate passivation, and its corrosion resistance is relatively good compared with other conversion films, so it is considered as the most likely alternative to chromate passivation [2] in recent years. But the corrosion resistance of trivalent chromium passivation protective layer of aluminum alloy cannot reach the effect of chromate passivation [3] , which limits its application.

[0008] Reference: [1], and Ximing, Guo Chongwu, Wang Qi, etc, New process for treating anodic oxidation film sealing wastewater of aluminum alloy [J], electroplating and finishing, 2022, 41 (9) : 670-674. [2], Song Liangliang, Li Jingfeng, Cai Chao, Preparation and corrosion resistance of trivalent chromium conversion film on 2024-T3 aluminum alloy [J], electroplating and finishing, 2015, 34 (9) : 480-486. [3], Liu Chao, Peng Jinping, Chen Shirong, etc, Research on new type of trivalent chromium composite conversion film process of aluminum alloy [J], electroplating and finishing, 2015, 34 (21) : 1226-1231. SUMMARY

[0009] In order to solve the pollution problem existing in the current aluminum alloy surface protection process, the utility model provides a kind of protective layer structure of aluminum alloy piece coating electrophoretic paint. In order to achieve the above-mentioned purpose, the utility model uses the following technical solutions:

[0010] A kind of protective layer structure of aluminum alloy piece coating electrophoretic paint, including aluminum alloy matrix, and trivalent chromium passivation film and electrophoretic paint coating prepared in turn from inside to outside on the aluminum alloy matrix;

[0011] The electrophoretic paint coating is the coating prepared by using graphene modified electrophoretic paint.

[0012] Preferably, the thickness of the trivalent chromium passivation film is 0.2-0.5 μm.

[0013] Preferably, the thickness of the electrophoretic paint coating is 10-25 μm.

[0014] Compared with the prior art, the utility model has the following beneficial effects:

[0015] 1, the protective layer structure of aluminum alloy piece coating electrophoretic paint disclosed by the utility model adopts graphene modified electrophoretic paint to prepare electrophoretic paint coating on the surface of passivated aluminum alloy, which significantly improves the corrosion resistance of aluminum alloy piece.

[0016] 2, the protective layer structure of aluminum alloy piece coating electrophoretic paint disclosed by the utility model adopts trivalent chromium passivation instead of traditional chromate passivation, which overcomes the high pollution problem caused by using hexavalent chromium. DRAWINGS

[0017] The drawings explained here are used to provide further understanding of the utility model, constitute a part of this application, and do not constitute undue limitation on the utility model, in the drawings:

[0018] Figure 1 It is the protective layer structure schematic view of embodiment 1 and embodiment 2 of the utility model. IMPLEMENTATION

[0019] The utility model will be in conjunction with the specific embodiments and drawings to be explained in detail below, in this utility model illustrative embodiment and explanation are used to explain the utility model, but not as the limitation of the utility model.

[0020] An aluminum alloy part coating electrophoretic paint protective layer structure, including aluminum alloy base, and in the aluminum alloy base from inside to outside sequentially prepared trivalent chromium passivation film, and electrophoretic paint coating.

[0021] The current pretreatment process is used to remove oil, alkali corrosion, light, and micro-etching on the aluminum alloy part.

[0022] The trivalent chromium passivation film is prepared on the pretreated aluminum alloy part by using the current trivalent chromium passivation process.

[0023] Preferably, the thickness of the trivalent chromium passivation film is 0.2-0.5 μm.

[0024] Preferably, the trivalent chromium passivation film is prepared by using ALBUME AP-773 aluminum alloy trivalent chromium passivation process of Superb Chemical Industry:

[0025] ALBUME AP-773 aluminum alloy trivalent chromium passivation agent 100-200 mL / L, passivation solution pH value 3.9-4.1, working temperature 30-50 ℃, passivation time 2-6 min.

[0026] The electrophoretic paint coating is prepared on the trivalent chromium passivated aluminum alloy part by using the electrophoretic coating process.

[0027] Preferably, the thickness of the electrophoretic paint coating is 10-25 μm.

[0028] Preferably, the electrophoretic paint coating is prepared by using AKINI 120 electrophoretic coating process of Superb Chemical Industry.

[0029] AKINI 120 electrophoretic paint 300-350 g / L, graphene filler 150-200 g / L, pigment 8-12 g / L, bath pH value 4-5, operating temperature 25-30 ℃, tank voltage 30-50 V, using aluminum alloy part as cathode and titanium plate as anode, and baking and curing at 120-140 ℃ for 20-30 min after electrophoretic coating. Example 1

[0030] As shown in Figure 1 A kind of aluminum alloy part coating electrophoretic paint protective layer structure, including aluminum alloy base 1, and in the aluminum alloy base 1 from inside to outside sequentially prepared trivalent chromium passivation film 2, and electrophoretic paint coating 3.

[0031] The model of the aluminum alloy is 2024.

[0032] 1, pretreatment:

[0033] The aluminum alloy substrate 1 is subjected to the following process: chemical degreasing → water washing → ultrasonic degreasing → water washing → alkaline corrosion → water washing → brightening → water washing → micro-corrosion → water washing.

[0034] 2. Trivalent chromium passivation:

[0035] After pretreatment, the aluminum alloy parts were treated with ALBUME AP-773 aluminum alloy trivalent chromium passivation process by Chaobang Chemical to prepare a trivalent chromium passivation film 2 with a thickness of 0.3μm.

[0036] ALBUME AP-773 aluminum alloy trivalent chromium passivating agent 180mL / L, passivation solution pH 4.1, working temperature 35℃, passivation time 5min.

[0037] 3. Electrophoretic coating:

[0038] After trivalent chromium passivation, the aluminum alloy parts were coated with an electrophoretic paint coating 3 using the AKINI 120 electrophoretic coating process of Chaobang Chemical. The coating thickness was 15μm.

[0039] The electrophoretic coating consists of 340g / L AKINI 120 paint, 150g / L graphene filler, 11g / L silver-gray pigment, pH value of the bath solution 4.5, operating temperature 25℃, and bath voltage 40V. The cathode is made of aluminum alloy and the anode is made of titanium plate.

[0040] 4. Drying:

[0041] After electrophoretic coating, aluminum alloy parts are dried and cured at 135℃ for 20 minutes. Example 2

[0042] like Figure 1 As shown, a protective layer structure for coating aluminum alloy parts with electrophoretic paint includes an aluminum alloy substrate 1, a trivalent chromium passivation film 2 formed sequentially from the inside to the outside on the aluminum alloy substrate 1, and an electrophoretic paint coating 3.

[0043] The aluminum alloy is designated as 2024-T3.

[0044] 1. Pre-processing:

[0045] The aluminum alloy substrate 1 is subjected to the following process: chemical degreasing → water washing → ultrasonic degreasing → water washing → alkaline corrosion → water washing → brightening → water washing → micro-corrosion → water washing.

[0046] 2. Trivalent chromium passivation:

[0047] After pretreatment, the aluminum alloy parts were treated with ALBUME AP-773 aluminum alloy trivalent chromium passivation process by Chaobang Chemical to prepare a trivalent chromium passivation film 2 with a thickness of 0.3μm.

[0048] ALBUME AP-773 aluminum alloy trivalent chromium passivation agent 120 mL / L, passivation solution pH value 3.9, working temperature 45℃, passivation time 4 min.

[0049] 3. Electrophoretic painting:

[0050] The trivalent chromium passivated aluminum alloy part is prepared into an electrophoretic paint coating 3 by using AKINI 120 electrophoretic coating process of Super Bond Chemical Co., Ltd., and the thickness of the coating is 15 μm.

[0051] AKINI 120 electrophoretic paint 310 g / L, graphene filler 160 g / L, black pigment 9 g / L, bath solution pH value 4.5, operating temperature 28℃, tank voltage 40 V, using an aluminum alloy part as a cathode and a titanium plate as an anode.

[0052] 4. Drying:

[0053] The electrophoretically painted aluminum alloy part is dried and cured at 125℃ for 30 min.

[0054] Test Example 1:

[0055] The aluminum alloy electrophoretic paint sample parts prepared in Example 1 and Example 2 are subjected to neutral salt spray test for 600 h according to GB / T 10125–2021 “Artificial Atmosphere Corrosion Test Salt Spray Test”, and the sample part surface is free of rust. The test shows that the protective layer structure of the aluminum alloy electrophoretic paint prepared by the utility model has good corrosion resistance.

[0056] Test Example 2:

[0057] The aluminum alloy electrophoretic paint sample parts prepared in Example 1 and Example 2 are tested for protective layer adhesion by thermal shock method according to GB / T 5270-2005 “Metallic Coatings on Metal Substrates Adhesion Strength Test Methods for Electrodeposited and Chemically Deposited Coatings”, and the sample parts are heated to 180℃ in a heating furnace for 30 min, and then taken out and placed in room temperature water for sudden cooling. The protective layer does not appear to bubble and fall off. The test shows that the protective layer structure of the aluminum alloy electrophoretic paint prepared by the utility model has good adhesion.

[0058] The above describes the technical solutions provided by the embodiments of the utility model in detail. The principles and implementation modes of the embodiments of the utility model are described by applying specific examples. The above description of the embodiments is only used to help understand the principles of the embodiments of the utility model. It should be noted that, for ordinary skilled persons in the art, without departing from the concept of the utility model, a number of modifications and improvements can be made, which are within the protection scope of the utility model.

Claims

1. A protective layer structure for electrophoretic coating of aluminum alloy parts, characterized in that: It includes an aluminum alloy substrate, a trivalent chromium passivation film formed sequentially from the inside to the outside on the aluminum alloy substrate, and an electrophoretic paint coating; The electrophoretic paint coating is prepared using graphene-modified electrophoretic paint.

2. The protective layer structure for electrophoretic coating of aluminum alloy parts as described in claim 1, characterized in that: The thickness of the trivalent chromium passivation film is 0.2–0.5 μm.

3. The protective layer structure for electrophoretic coating of aluminum alloy parts as described in claim 1, characterized in that: The thickness of the electrophoretic paint coating is 10–25 μm.

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