Trivalent chromium plating layer structure of aerospace aluminum alloy part

Abstract

The utility model discloses a trivalent chromium plating layer structure of an aerospace aluminum alloy part, which comprises an aluminum alloy substrate, and a chemical zinc deposition layer, a chemical nickel preplating layer, a nickel-copper alloy plating layer, a nickel-tin alloy plating layer, a trivalent chromium plating layer and a nano polymer protective film which are sequentially prepared on the aluminum alloy substrate from inside to outside. According to GB / T5270-2005 Assessment of Metal Covering Layer Electro-Deposition and Chemical Deposition Layer Adhesive Strength Test Method on Metal Matrix, the binding force of the plating layer is measured by a thermal shock test method, and the measurement result meets the standard requirement. The corrosion resistance of the coating is measured according to GB / T10125-2021 Artificial Atmosphere Corrosion Test Salt Spray Test, no white corrosive is generated on the surface of a plated part after a neutral salt spray test is carried out for 148 hours, and the corrosion resistance of the coating meets the special requirements of aerospace accessories.

Description

Technical Field

[0001] The utility model belongs to the field of metal electroplating, and in particular relates to a trivalent chromium plating layer structure of an aerospace aluminum alloy part. Background Art

[0002] To mitigate the pollution caused by cadmium plating, some domestic aerospace electrical components are currently experimenting with electroless nickel plating instead of traditional cadmium plating. The process for electroless nickel plating on aluminum alloy parts typically involves sequentially depositing an electroless zinc layer, an electroless pre-nickel layer, and an electroless nickel plating layer on an aluminum alloy substrate. The resulting protective layer is required to withstand a 96-hour neutral salt spray test without corrosion. However, the electroless nickel plating layer is cathodic relative to the aluminum alloy substrate. When the coating is damaged or has pores, galvanic corrosion will occur on the plated part, destroying the aluminum alloy substrate. Therefore, the corrosion resistance of this coating structure is less than ideal.

[0003] Nickel-copper alloy coating has good mechanical properties, corrosion resistance and electrical properties, and has been increasingly valued by domestic peers. [1] The performance of nickel-copper alloy coating is better than nickel coating and it is currently mainly used as decorative coating.

[0004] Nickel-tin alloy coating is elegant dark white, with better corrosion resistance and wear resistance than nickel coating. It is suitable for protective decorative coatings such as automobile and motorcycle parts, marine equipment, electrical accessories, bathroom supplies, hardware products, etc. Nickel-tin alloy coating will show a certain degree of brittleness when it reaches a certain thickness. [2] , therefore, it is not suitable for preparing thicker coatings.

[0005] The corrosion resistance and discoloration resistance of trivalent chromium plating are not as good as those of hexavalent chromium plating. [3] , it is necessary to develop new post-processing protection processes to protect them.

[0006] References: [1]. Yang Ruisong, Li Mingtian, Wang Ying, et al., Effect of process parameters on the composition and phase structure of electroplated nickel-copper alloy coating [J], Electroplating and Finishing, 2014, 33(15): 633-635. [2]. Song Zhenxing, Ma Shuyuan, Yao Suwei, et al., Study on corrosion resistance of electroplated nickel-tin alloy [J], Electroplating and Finishing, 2013, 35(10): 1-4+16. [3]. Tu Zhenmi, Zheng Jian, Li Ning, et al., Current status and development trend of trivalent chromium electroplating [J], Surface Technology, 2007, 36(5): 59-63+87. Utility Model Content

[0007] In order to overcome the technical defect that chemical nickel plating of aerospace aluminum alloy parts does not have electrochemical protection, the utility model provides a trivalent chromium plating layer structure for aerospace aluminum alloy parts. In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0008] A trivalent chromium plating layer structure for an aerospace aluminum alloy part, characterized by comprising an aluminum alloy substrate, and an electroless zinc deposition layer, an electroless pre-plated nickel layer, a nickel-copper alloy plating layer, a nickel-tin alloy plating layer, a trivalent chromium plating layer, and a nano-polymer protective film sequentially prepared on the aluminum alloy substrate from the inside out;

[0009] Preferably, the thickness of the chemical pre-plated nickel layer is 0.8 to 1.5 μm.

[0010] Preferably, the thickness of the nickel-copper alloy plating layer is 10 to 22 μm.

[0011] Preferably, the thickness of the nickel-tin alloy plating layer is 2 to 5 μm.

[0012] Preferably, the thickness of the trivalent chromium plating layer is 0.3 to 0.6 μm.

[0013] The electrode potential of nickel-tin alloy is more negative than that of nickel-copper alloy. Plating nickel-tin alloy on a nickel-copper alloy coating provides an anodic coating, providing electrochemical protection for the nickel-copper alloy coating and effectively preventing the corrosive medium from eroding the substrate. The trivalent chromium plating solution has a strong activation ability, forming a good bond between the nickel-tin alloy coating and the trivalent chromium plating. Trivalent chromium plating has higher corrosion resistance than nickel-tin alloy coatings, and plating trivalent chromium on a nickel-tin alloy coating can further improve the corrosion resistance of the coating.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The trivalent chromium plating structure of aerospace aluminum alloy parts disclosed in the utility model is a nickel-tin alloy plated on a nickel-copper alloy plated layer. The nickel-tin alloy plated layer has an electrochemical protective effect on the base plated layer, overcoming the technical defect that the chemical nickel plated layer directly prepared on the aluminum alloy parts does not have an electrochemical protective effect.

[0016] 2. The corrosion resistance of the trivalent chromium plating structure, nickel-copper alloy plating and nickel-tin alloy plating of aerospace aluminum alloy parts disclosed in the utility model is higher than that of the traditional nickel plating;

[0017] 3. The trivalent chromium plating structure of aerospace aluminum alloy parts disclosed in the utility model is a trivalent chromium plating layer prepared on a nickel-tin alloy plating layer, which further improves the corrosion resistance of the plating layer;

[0018] 4. The trivalent chromium plating layer structure of aerospace aluminum alloy parts disclosed in the utility model prepares a nano-polymer protective film on the trivalent chromium plating layer, and the process is environmentally friendly and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute an improper limitation of the present invention. In the drawings:

[0020] Figure 1 It is a schematic diagram of the coating structure of Example 1 and Example 2 of the present utility model. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The schematic embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0022] The aluminum alloy parts are subjected to degreasing, alkali corrosion, polishing, slag removal and micro-corrosion activation according to the current pre-treatment process.

[0023] After the aluminum alloy parts are pre-treated, the chemical zinc deposition layer is prepared using the current aluminum alloy chemical zinc deposition agent.

[0024] Preferably, the chemical zinc deposition layer is prepared using ALBUME AS-699 cyanide-free aluminum zinc deposition agent produced by Chaobang Chemical:

[0025] ALBUME AS-699 cyanide-free aluminum zinc precipitation agent 140 ~ 180mL / L, the working solution contains zinc ions 6 ~ 9g / L, copper ions 0.16 ~ 0.20g / L, the operating temperature is 20 ℃ ~ 30 ℃, the zinc precipitation time is 60 ~ 120s.

[0026] Preferably, the chemical zinc deposition layer is prepared using AZIN-113 acidic aluminum zinc deposition agent produced by Chaobang Chemical:

[0027] AZIN-113 acidic aluminum zinc precipitation agent 150 ~ 250mL / L, working temperature 15 ℃ ~ 30 ℃, bath pH value 3.4 ~ 4.5, zinc precipitation time 30 ~ 90s.

[0028] After electroless zinc deposition on aluminum alloy parts, the current low-temperature electroless nickel plating process is used to prepare an electroless pre-plated nickel layer.

[0029] Preferably, the thickness of the chemical pre-plated nickel layer is 0.5 to 1.2 μm.

[0030] Preferably, the chemical pre-plated nickel layer is prepared using Chaobang Chemical's GG-178 alkaline chemical nickel plating process:

[0031] GG-178 A additive 25~50mL / L, GG-178 B reducing agent 25~40mL / L, GG-178 C stabilizer 30~60mL / L, operating temperature 25℃~38℃, plating solution pH 8.5~9.5.

[0032] Preferably, the chemical pre-plated nickel layer is prepared using Chaobang Chemical's GG-158 alkaline chemical nickel plating process:

[0033] GG-158 A opener: 140-160 mL / L, GG-158 B supplement: 90-110 mL / L, GG-158 C supplement: 90-110 mL / L, operating temperature: 30°C-45°C, pH value of plating solution: 7.5-8.5.

[0034] The aluminum alloy parts are chemically pre-nickel plated and then the nickel-copper alloy coating is prepared by adopting the current nickel-copper alloy plating process.

[0035] Preferably, the thickness of the nickel-copper alloy plating layer is 10 to 22 μm.

[0036] Preferably, the nickel-copper alloy coating is prepared using the Nistar 6070 bright nickel-copper alloy plating process of Chaobang Chemical:

[0037] Nickel sulfate hexahydrate 180-220 g / L, copper sulfate pentahydrate 8-12 g / L, trisodium citrate 50-70 g / L, disodium hydroxyethylidene diphosphonate 20-30 g / L, boric acid 28-35 g / L, sodium chloride 5-8 g / L, NISTAR 6070 brightener 0.3-0.7 mL / L, NISTAR 6071 auxiliary agent 6-10 mL / L, NI-35 wetting agent 0.3-1.0 mL / L, plating solution pH 4.3-4.8, plating tank temperature 50-55 °C, cathode current density 2.6-3.2 A / dm 2 , the cathode moves 3 to 5 m / min.

[0038] After the aluminum alloy parts are plated with nickel-copper alloy, the nickel-tin alloy coating is prepared using the current nickel-tin plating process.

[0039] Preferably, the thickness of the nickel-tin alloy plating layer is 2 to 5 μm.

[0040] Preferably, the nickel-tin alloy coating is prepared using Chaobang Chemical's YF-737 high-corrosion-resistant nickel-tin alloy plating process:

[0041] Nickel chloride 140-180 g / L, YF-737A additive 450-600 mL / L, YF-737B additive 30-60 mL / L, plating solution pH 3.5-4.5, plating tank temperature 65-70 ° C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3 to 5 m / min.

[0042] After the aluminum alloy parts are plated with nickel-tin alloy, a trivalent chromium plating layer is prepared using the current trivalent chromium plating process.

[0043] Preferably, the thickness of the trivalent chromium plating layer is 0.3 to 0.6 μm.

[0044] Preferably, the trivalent chromium plating layer is prepared using Chaobang Chemical's Trich-6561 chloride trivalent chromium plating process:

[0045] Trich-6561 pre-treatment salt 400-450 g / L, Trich-6563 complexing agent 65-85 mL / L, Trich-6564 stabilizer 1-2 mL / L, Trich-6565 wetting agent 1-3 mL / L, wherein the mass concentration of trivalent chromium is 23-25 ​​g / L, the mass concentration of boric acid is 55-60 g / L, the pH value of the plating solution is 2.5-3.0, the plating tank temperature is 25-36 ° C, and the cathode current density is 8-16 A / dm 2 , medium air agitation.

[0046] After trivalent chromium plating of aluminum alloy parts, the nano-polymer protective film is prepared by the current nano-polymer electrolytic protection process.

[0047] Preferably, the nano-polymer protective film is prepared using the PROTEZVY 1126 electrolytic protection process of Chaobang Chemical:

[0048] PROTEZVY 1126 MUP opener 30-40 mL / L, PROTEZVY 1126 ADDITIVE C 70-90 mL / L, sodium hydroxide 0.15-0.25 g / L, bath pH 3.4-4.0, operating temperature 55-65°C, cathode current density 0.05-0.1 A / dm 2 , electrolysis time 3 to 10 minutes.

[0049] Aluminum alloy parts are electrolytically protected and then washed and dried. Example 1

[0050] like Figure 1 As shown, a trivalent chromium plating layer structure of an aerospace aluminum alloy part includes an aluminum alloy substrate 1, and an electroless zinc deposition layer 2, an electroless pre-plated nickel layer 3, a nickel-copper alloy plating layer 4, a nickel-tin alloy plating layer 5, a trivalent chromium plating layer 6, and a nano-polymer protective film 7 prepared in sequence from the inside to the outside on the aluminum alloy substrate 1.

[0051] 1. Pre-treatment:

[0052] According to the current aluminum alloy pretreatment process, the aluminum alloy substrate 1 is subjected to "chemical degreasing → water washing → ultrasonic degreasing → water washing → alkaline corrosion → water washing → polishing → water washing → descaling → water washing → micro-corrosion → water washing".

[0053] 2. Chemical zinc precipitation:

[0054] After pre-treatment of the aluminum alloy parts, the chemical zinc deposition layer 2 was prepared using ALBUME AS-699 cyanide-free aluminum zinc deposition agent produced by Chaobang Chemical.

[0055] ALBUME AS-699 cyanide-free aluminum zinc precipitation agent 150mL / L, the working solution contains zinc ions 8g / L, copper ions 0.18g / L, operating temperature 23℃, zinc precipitation time 100s.

[0056] The specific process flow is "first zinc precipitation → water washing → zinc stripping → water washing → second zinc precipitation → water washing".

[0057] 3. Chemical pre-nickel plating:

[0058] After electroless zinc deposition on the aluminum alloy part, the chemical pre-plated nickel layer 3 was prepared using Chaobang Chemical's GG-178 alkaline chemical nickel plating process, with a coating thickness of 1 μm.

[0059] GG-178 A additive 42mL / L, GG-178 B reducing agent 32mL / L, GG-178 C stabilizer 45mL / L, operating temperature 33℃, plating solution pH 9.2.

[0060] 4. Nickel-plated copper alloy:

[0061] After chemical pre-nickel plating, the aluminum alloy part is subjected to Nistar 6070 bright nickel-copper alloy plating process produced by Chaobang Chemical to prepare a nickel-copper alloy coating 4 with a coating thickness of 15 μm.

[0062] Nickel sulfate hexahydrate 200g / L, copper sulfate pentahydrate 10g / L, trisodium citrate 60g / L, disodium hydroxyethylidene diphosphonate 25g / L, boric acid 31g / L, sodium chloride 6g / L, NISTAR 6070 brightener 0.5mL / L, NISTAR 6071 auxiliary agent 8mL / L, NI-35 wetting agent 0.6mL / L, plating solution pH 4.5, plating tank temperature 53℃, cathode current density 3A / dm 2 , cathode moves 4m / min.

[0063] 5. Nickel-tin alloy plating:

[0064] After the aluminum alloy part is plated with nickel-copper alloy, the nickel-tin alloy coating 5 is prepared using Chaobang Chemical's YF-737 high-corrosion-resistant nickel-tin alloy plating process, and the coating thickness is 3 μm.

[0065] Nickel chloride 170g / L, YF-737A additive 550mL / L, YF-737B additive 50mL / L, plating solution pH 3.8, plating tank temperature 66℃, cathode current density 1.0A / dm 2 , cathode moves 4m / min.

[0066] 6. Trivalent chromium plating:

[0067] After the aluminum alloy part is plated with nickel-tin alloy, a trivalent chromium plating layer 6 is prepared using Chaobang Chemical's Trich-6561 chloride trivalent chromium plating process, with a coating thickness of 0.5 μm.

[0068] Trich-6561 pre-treatment salt 440g / L, Trich-6563 complexing agent 80mL / L, Trich-6564 stabilizer 1.5mL / L, Trich-6565 wetting agent 2mL / L, the mass concentration of trivalent chromium is 24.7g / L, the mass concentration of boric acid is 59g / L, the plating solution pH is 2.6, the plating tank temperature is 30℃, and the cathode current density is 14A / dm 2 , medium air agitation.

[0069] 7. Electrolytic protection:

[0070] After trivalent chromium plating, the aluminum alloy parts were electrolytically protected with a nano-polymer protective film 7 using the PROTEZVY 1126 electrolytic protection process of Chaobang Chemical.

[0071] PROTEZVY 1126 MUP opener 37 mL / L, PROTEZVY 1126 ADDITIVE C 85 mL / L, sodium hydroxide 0.22 g / L, bath pH 3.8, operating temperature 58°C, cathode current density 0.08 A / dm 2 , electrolysis time 6min.

[0072] 8. Drying:

[0073] After electrolytic protection, aluminum alloy parts are subjected to "water washing → pure water washing → drying". Example 2

[0074] like Figure 1 As shown, a trivalent chromium plating layer structure of an aerospace aluminum alloy part includes an aluminum alloy substrate 1, and an electroless zinc deposition layer 2, an electroless pre-plated nickel layer 3, a nickel-copper alloy plating layer 4, a nickel-tin alloy plating layer 5, a trivalent chromium plating layer 6, and a nano-polymer protective film 7 prepared in sequence from the inside to the outside on the aluminum alloy substrate 1.

[0075] 1. Pre-treatment:

[0076] According to the current aluminum alloy pretreatment process, the aluminum alloy substrate 1 is subjected to "chemical degreasing → water washing → ultrasonic degreasing → water washing → alkaline corrosion → water washing → polishing → water washing → descaling → water washing → micro-corrosion → water washing".

[0077] 2. Chemical zinc precipitation:

[0078] After pre-treatment of the aluminum alloy parts, the chemical zinc deposition layer 2 was prepared using Chaobang Chemical's AZIN-113 acidic aluminum zinc deposition agent.

[0079] AZIN-113 acidic aluminum zinc precipitation agent 200mL / L, working temperature 25℃, bath pH 4.0, zinc precipitation time 60s.

[0080] The specific process flow is "first zinc precipitation → water washing → zinc stripping → water washing → second zinc precipitation → water washing".

[0081] 3. Chemical pre-nickel plating:

[0082] After electroless zinc deposition on the aluminum alloy part, a chemical pre-plated nickel layer 3 was prepared using Chaobang Chemical's GG-158 alkaline chemical nickel plating process, with a coating thickness of 1 μm.

[0083] GG-158 A opener 150mL / L, GG-158 B supplement 100mL / L, GG-158 C supplement 100mL / L, operating temperature 35℃, plating solution pH 8.2.

[0084] 4. Nickel-plated copper alloy:

[0085] After chemical pre-nickel plating, the aluminum alloy part is subjected to Nistar 6070 bright nickel-copper alloy plating process produced by Chaobang Chemical to prepare a nickel-copper alloy coating 4 with a coating thickness of 15 μm.

[0086] Nickel sulfate hexahydrate 220g / L, copper sulfate pentahydrate 12g / L, trisodium citrate 70g / L, disodium hydroxyethylidene diphosphonate 20g / L, boric acid 35g / L, sodium chloride 8g / L, NISTAR 6070 brightener 0.5mL / L, NISTAR 6071 auxiliary agent 8mL / L, NI-35 wetting agent 0.6mL / L, plating solution pH 4.5, plating tank temperature 52℃, cathode current density 3A / dm 2 , cathode moves 4m / min.

[0087] 5. Nickel-tin alloy plating:

[0088] After the aluminum alloy part is plated with nickel-copper alloy, the nickel-tin alloy coating 5 is prepared using Chaobang Chemical's YF-737 high-corrosion-resistant nickel-tin alloy plating process, and the coating thickness is 3 μm.

[0089] Nickel chloride 150g / L, YF-737A additive 480mL / L, YF-737B additive 40mL / L, plating solution pH 4.2, plating tank temperature 66℃, cathode current density 0.8A / dm 2 , cathode moves 4m / min.

[0090] 6. Trivalent chromium plating:

[0091] After the aluminum alloy part is plated with nickel-tin alloy, a trivalent chromium plating layer 6 is prepared using Chaobang Chemical's Trich-6561 chloride trivalent chromium plating process, with a coating thickness of 0.5 μm.

[0092] Trich-6561 pre-treatment salt 410g / L, Trich-6563 complexing agent 70mL / L, Trich-6564 stabilizer 1.5mL / L, Trich-6565 wetting agent 2mL / L, the mass concentration of trivalent chromium is 23.3g / L, the mass concentration of boric acid is 56g / L, the plating solution pH is 2.8, the plating tank temperature is 30℃, and the cathode current density is 14A / dm 2 , medium air agitation.

[0093] 7. Electrolytic protection:

[0094] After trivalent chromium plating, the aluminum alloy parts were electrolytically protected with a nano-polymer protective film 7 using the PROTEZVY 1126 electrolytic protection process of Chaobang Chemical.

[0095] PROTEZVY 1126 MUP opener 33 mL / L, PROTEZVY 1126 ADDITIVE C 75 mL / L, sodium hydroxide 0.18 g / L, bath pH 3.6, operating temperature 62°C, cathode current density 0.08 A / dm 2 , electrolysis time 7min.

[0096] 8. Drying:

[0097] After electrolytic protection, aluminum alloy parts are subjected to "water washing → pure water washing → drying".

[0098] Test Example 1:

[0099] Aluminum alloy trivalent chromium-plated samples were prepared according to the process of Examples 1 and 2. The coating adhesion was tested in accordance with GB / T 5270–2005 "Review of test methods for adhesion strength of electrodeposited and chemically deposited metallic coatings on metal substrates." The samples were heated to 220°C in a heating furnace for 30 minutes, then removed and quenched in room temperature water. No blistering or shedding of the coating occurred, indicating that the coating had good adhesion.

[0100] Test Example 2:

[0101] Aluminum alloy trivalent chromium-plated samples were prepared according to the process of Example 1 and Example 2, and the corrosion resistance was tested according to GB / T10125-2021 "Artificial atmosphere corrosion test salt spray test". The sample was subjected to a neutral salt spray test for 148 hours and no white corrosion products were generated on its surface. The prepared coating has excellent corrosion resistance.

[0102] Test Example 3:

[0103] The aluminum alloy trivalent chromium-plated samples prepared according to the process of Example 1 and Example 2 were subjected to a constant humidity test in accordance with GB / T2423.3-2016 "Basic Environmental Testing Procedures for Electrical and Electronic Products Test Ca: Constant Humidity Test Method". The test was carried out for 1000 hours at a temperature of 40°C and a relative humidity of 93%. There was no visible change in the coating. The anti-discoloration ability of the coating prepared by the utility model fully meets customer requirements.

[0104] The technical solutions provided by the embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only intended to help understand the principles of the embodiments of the present invention. It should be noted that, for those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements fall within the scope of protection of the present invention.

Claims

1. A trivalent chromium plating layer structure for an aerospace aluminum alloy part, characterized by: The invention comprises an aluminum alloy substrate, and a chemical zinc deposition layer, a chemical pre-plated nickel layer, a nickel-copper alloy plating layer, a nickel-tin alloy plating layer, a trivalent chromium plating layer, and a nano polymer protective film which are sequentially prepared on the aluminum alloy substrate from the inside to the outside.

2. The trivalent chromium plating layer structure for aerospace aluminum alloy parts according to claim 1, characterized in that: The thickness of the chemical pre-plated nickel layer is 0.8-1.5 μm.

3. The trivalent chromium plating layer structure for aerospace aluminum alloy parts according to claim 1, characterized in that: The thickness of the nickel-copper alloy plating layer is 10 to 22 μm.

4. The trivalent chromium plating layer structure for aerospace aluminum alloy parts according to claim 1, characterized in that: The thickness of the nickel-tin alloy plating layer is 2-5 μm.

5. The trivalent chromium plating layer structure for aerospace aluminum alloy parts according to claim 1, characterized in that: The thickness of the trivalent chromium plating layer is 0.3-0.6 μm.

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