Golden yellow passivated coating structure for zinc plating of aluminum alloy

Abstract

The utility model discloses an aluminum alloy zinc plating golden yellow passivation plating layer structure which comprises an aluminum alloy base body, and a chemical zinc deposition layer, a cyanide-free copper zinc alloy plating layer, a potassium chloride zinc plating layer, a trivalent chromium golden yellow passivation film and an electrophoretic varnish coating which are sequentially prepared on the aluminum alloy base body from inside to outside. According to the aluminum alloy galvanized golden yellow passivated coating structure disclosed by the utility model, the binding force of the coating is measured by a thermal shock test method according to GB / T 5270-2005 < GB / T > 5270-2005 < GB / T > 5270-2005 < GB / T > 5270-2005 > < GB / T > 5270-2005 > < GB / T > 5270-2005 > < GB / T > 5270- A neutral salt spray test is carried out for 432 hours according to GB / T 10125-2021 Artificial Atmosphere Corrosion Test Salt Spray Test, no corrosives are generated on the surface of a plated part, and the prepared plating layer structure has good corrosion resistance.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of metal electroplating and coating, and particularly relates to a zinc-plated gold yellow passivated coating structure of aluminum alloy. BACKGROUND

[0002] Potassium chloride zinc plating has been widely applied due to its bright plating layer, high current efficiency, simple plating solution composition and convenient maintenance. The plating layer performance of the third generation of potassium chloride zinc plating has reached or even surpassed that of cyanide-free alkaline zinc plating [1] , and its market share is increasing year by year.

[0003] The potassium chloride zinc plating layer has good decorative effect after trivalent chromium gold yellow passivation. However, the gloss of such a plating layer is prone to darkening, which limits the application of the potassium chloride zinc plating layer gold yellow passivation process. Therefore, it is of practical significance to solve the problems existing in the trivalent chromium gold yellow passivation process of the zinc plating layer and promote it to the market.

[0004] The trivalent chromium passivation film is thin and does not have self-repairing property [2] , and the passivation film is prone to wear and tear. When the passivation film is damaged, the zinc plating layer will be corroded by corrosive media.

[0005] The traditional process flow of aluminum alloy part zinc plating usually includes sequentially preparing a chemical zinc deposition layer, an acid zinc plating layer and a trivalent chromium passivation film on an aluminum alloy substrate. The electrode potential of metallic zinc is positive with respect to that of metallic aluminum, and the potential difference is large. The zinc plating layer on the aluminum alloy part is a cathodic plating layer, which does not have electrochemical protection effect on the substrate. Such a plating layer structure has low corrosion resistance.

[0006] The resin used for high decorative cathodic electrophoretic paint is synthesized from acrylate or methacrylate monomers. Using such a resin as the base resin of cathodic electrophoretic paint, the paint film is very smooth and bright, has strong weather resistance, and is very suitable for products with high appearance requirements [3] .

[0007] Reference: [1], Xia Liang, Lin An, Guo Chongwu, Potassium Chloride Zinc Plating Process Suitable for Aviation and Aerospace Parts [J], Electroplating and Finishing, 2021, 40(17): 1328-1331. [2], Wu Yinan, Trivalent Chromium Passivation of Zinc Plating Layer [J], Electroplating and Environmental Protection, 2003, 32(2): 30-32. [3], Liu Wenhua, Yao Jinshui, Fan Rui, et al., Research Progress of Cathodic Electrophoretic Paint [J], Journal of Qilu University of Technology, 2014, 28(4): 11-13. SUMMARY

[0008] In order to solve the problem that the aluminum alloy direct galvanizing does not have electrochemical protection effect and the trivalent chromium passivation film is easy to fade, the utility model provides a kind of galvanizing gold yellow passivation's coating structure of aluminum alloy.

[0009] A kind of galvanizing gold yellow passivation's coating structure of aluminum alloy, including aluminum alloy matrix, and the chemical zinc deposition layer, cyanide-free copper zinc alloy coating, potassium chloride zinc plating layer, trivalent chromium gold yellow passivation film and electrophoretic varnish coating layer prepared in sequence from inside to outside on the aluminum alloy matrix;

[0010] The cyanide-free copper zinc alloy coating is the coating prepared by adopting polythiocyanate copper zinc alloy plating process.

[0011] Preferably, the thickness of the cyanide-free copper zinc alloy coating is 3-7 μm.

[0012] Preferably, the thickness of the potassium chloride zinc plating layer is 8-16 μm.

[0013] Preferably, the thickness of the electrophoretic varnish coating layer is 8-17 μm.

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

[0015] 1, the galvanizing gold yellow passivation's coating structure of aluminum alloy disclosed by the utility model takes cyanide-free copper zinc alloy coating as bottom coating layer, solves the defect that direct zinc plating on the surface of aluminum alloy does not have electrochemical protection effect;

[0016] 2, the galvanizing gold yellow passivation's coating structure of aluminum alloy disclosed by the utility model uses electrophoretic painting process to coat electrophoretic varnish on the zinc plating layer passivated by trivalent chromium gold yellow, and the coating is beautiful and not easy to fade, so that the zinc plating layer has the performance of decorative coating, and the application range of zinc plating process is widened.

[0017] 3, the galvanizing gold yellow passivation's coating structure of aluminum alloy disclosed by the utility model uses electrophoretic painting process to coat electrophoretic varnish on the trivalent chromium gold yellow passivation film, which overcomes the defect that the trivalent chromium passivation film is easy to be scratched and does not have self-repairing property. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings described herein are used to provide further understanding of the utility model, constitute a part of this application, and do not constitute improper limitation on the utility model, and in the drawings:

[0019] Figure 1 It is the coating structure schematic view of example 1 and example 2 of the utility model. DETAILED DESCRIPTION

[0020] The utility model will be in conjunction with the drawings and specific embodiments to be explained in detail below, here the utility model's schematic embodiment and explanation are used to explain the utility model, but not as the limitation to the utility model.

[0021] On the aluminum alloy piece base body, the pretreatment, the preparation chemical zinc layer, the cyanide-free copper zinc alloy plating layer, the potassium chloride zinc plating layer, the trivalent chromium gold yellow passivation film and the electrophoretic varnish coating are sequentially carried out.

[0022] The current pretreatment process is used to carry out oil removal, film removal, lightening and weak corrosion on the aluminum alloy piece base body.

[0023] The current aluminum alloy chemical zinc deposition agent is used to prepare the chemical zinc layer:

[0024] Preferably, the chemical zinc layer is prepared by using the cyanide-free aluminum surface zinc deposition process of ALBUME AS-699 of Super Bond Chemical Industry:

[0025] The cyanide-free aluminum surface zinc deposition agent ALBUME AS-699 is 150-170 mL / L, the working solution contains 6-9 g / L of zinc ions and 0.16-0.20 g / L of copper ions, the operation temperature is 20-30 DEG C, and the zinc deposition time is 60-120 s.

[0026] Preferably, the chemical zinc layer is prepared by using the acid aluminum surface zinc deposition agent AZIN-113 of Super Bond Chemical Industry:

[0027] The acid aluminum surface zinc deposition agent AZIN-113 is 50-250 mL / L, the working temperature is 15-30 DEG C, the pH value of the zinc deposition solution is 3.4-4.2, and the zinc deposition time is 20-80 s.

[0028] The preparation process of the chemical zinc layer is as follows: first zinc deposition, water washing, zinc removal, water washing, second zinc deposition and water washing.

[0029] The current polymeric thiocyanate copper zinc alloy plating process is used to prepare the copper zinc alloy plating layer.

[0030] Preferably, the thickness of the copper zinc alloy plating layer is 3-7 μm.

[0031] Preferably, the copper zinc alloy plating layer is prepared by using the following polymeric thiocyanate copper zinc alloy plating process:

[0032] The polymeric cuprous thiocyanate is 18-25 g / L, the polymeric zinc thiocyanate is 8-12 g / L, the polymeric sodium thiocyanate is 125-175 g / L, the ammonium chloride is 3-5 g / L, the pH value of the plating solution is 9.5-11.5, the temperature of the plating bath is 35-45 DEG C, the cathode current density is 0.5-1.5 A / dm 2 , the cathode moves at a speed of 3-5 m / min, and a brass plate is used as the anode.

[0033] The potassium chloride galvanizing layer is prepared by using the current third-generation potassium chloride galvanizing process.

[0034] Preferably, the thickness of the potassium chloride galvanizing layer is 8-16 μm.

[0035] Preferably, the potassium chloride galvanizing layer is prepared by using the DETRONZIN 401 potassium chloride galvanizing process of Superbond Chemical Industry:

[0036] Zinc chloride 60-70 g / L, potassium chloride 180-220 g / L, boric acid 25-35 g / L, DETRONZIN 401 brightener 0.8-1.5 mL / L, DETRONZIN 401 softener 25-30 mL / L, bath temperature 15-30 °C, bath pH value 4.8-5.6, cathode current density 2.0-4.0 A / dm 2 .

[0037] Preferably, the potassium chloride galvanizing layer is prepared by using the DETRONZIN 406 low-foam potassium chloride galvanizing process of Superbond Chemical Industry:

[0038] Zinc chloride 60-70 g / L, potassium chloride 180-220 g / L, boric acid 27-33 g / L, DETRONZIN 406 brightener 0.5-1.5 mL / L, DETRONZIN 406 softener 25-30 mL / L, bath temperature 15-30 °C, bath pH value 5.0-5.5, cathode current density 2.0-4.0 A / dm 2 .

[0039] The trivalent chromium golden yellow passivation film is prepared by using the current trivalent chromium blue-white passivation and golden yellow conversion process.

[0040] Preferably, the trivalent chromium blue-white passivation is prepared by using the TRIROS TCP-305 trivalent chromium passivation process of Superbond Chemical Industry:

[0041] TRIROS TCP-305 opening agent 40-80 mL / L, passivation bath pH value 2.0-2.8, operation temperature 25-35 °C, slight air agitation, passivation time 15-60 s.

[0042] Preferably, the trivalent chromium blue-white passivation is prepared by using the TRIROS TCP-187 trivalent chromium passivation process of Superbond Chemical Industry:

[0043] TRIROS TCP-187A agent 20-40 mL / L, TRIROS TCP-187B agent 20-40 mL / L, passivation bath pH value 1.7-2.5, operation temperature 20-30 °C, air agitation or swing plating, passivation time 30-60 s.

[0044] Preferably, the gold color conversion is carried out by using TRIROS YD-143 gold color conversion process of Superbond Chemicals:

[0045] TRIROS YD-143 gold color conversion agent 10-20 mL / L, bath temperature 25-35℃, immersion time 45-90 s, soft air agitation.

[0046] The electrophoretic clear coating is prepared by using AKINI 120 electrophoretic coating process of Superbond Chemicals.

[0047] Preferably, the thickness of the electrophoretic clear coating is 8-17 μm.

[0048] AKINI 120 electrophoretic paint 300-350 g / L, bath pH value 4-5, operating temperature 25-30℃, bath voltage 30-50 V, using plated parts as cathode and titanium plate as anode, coating is dried and cured at 120-140℃ for 20-30 min.

[0049] Example 1:

[0050] As shown in Figure 1 Fig. 1, a gold color passivated plated layer structure of aluminum alloy zinc-plated layer includes an aluminum alloy base 1, and a chemical zinc deposition layer 2, a cyanide-free copper-zinc alloy plated layer 3, a potassium chloride zinc-plated layer 4, a trivalent chromium gold color passivation film 5, and an electrophoretic clear coating 6 prepared in sequence from inside to outside on the aluminum alloy base 1.

[0051] 1. Pretreatment:

[0052] The aluminum alloy base 1 is subjected to the current pretreatment process of "chemical oil removal→water washing→ultrasonic oil removal→water washing→alkali corrosion→water washing→lightening→water washing→micro-corrosion→water washing".

[0053] 2. Chemical zinc deposition:

[0054] The chemical zinc deposition layer 2 is prepared by using ALBUME AS-699 cyanide-free aluminum zinc deposition agent of Superbond Chemicals after the pretreatment of the aluminum alloy.

[0055] ALBUME AS-699 cyanide-free aluminum zinc deposition agent 155 mL / L, zinc ion 7 g / L and copper ion 0.18 g / L in the working solution, operating temperature 28℃, zinc deposition time 100 s.

[0056] The process flow is: first zinc deposition→water washing→zinc removal→water washing→second zinc deposition→water washing.

[0057] 3. Copper-zinc alloy plating:

[0058] The cyanide-free copper-zinc alloy coating 3 with a thickness of 5 μm was prepared on the pretreated aluminum alloy part by the following polythiocyanate copper-zinc alloy plating process.

[0059] Cuprous polythiocyanate 20 g / L, zinc polythiocyanate 9 g / L, sodium polythiocyanate 140 g / L, ammonium chloride 4 g / L, plating bath pH 10.5, plating bath temperature 40℃, cathode current density 1.0 A / dm 2 , cathode moving speed 4 m / min, and brass plate as anode.

[0060] 4. Potassium chloride zinc plating:

[0061] The potassium chloride zinc plating layer 4 with a thickness of 12 μm was prepared on the copper-zinc alloy plated aluminum alloy part by the following DETRONZIN 401 potassium chloride zinc plating process of Superbond Chemical Industry.

[0062] Zinc chloride 65 g / L, potassium chloride 200 g / L, boric acid 30 g / L, DETRONZIN 401 brightener 1 mL / L, DETRONZIN 401 softener 30 mL / L, plating bath temperature 25℃, plating bath pH 5.2, cathode current density 3 A / dm 2 .

[0063] 5. Golden yellow passivation:

[0064] 1) Trivalent chromium blue-white passivation:

[0065] The trivalent chromium blue-white passivation film was prepared on the potassium chloride zinc plated aluminum alloy part by the following TRIROS TCP-305 trivalent chromium passivation agent of Superbond Chemical Industry.

[0066] TRIROS TCP-305 opening agent 60 mL / L, passivation bath pH 2.4, passivation temperature 30℃, slight air agitation, and passivation time 40 s.

[0067] 2) Golden yellow conversion:

[0068] The trivalent chromium golden yellow passivation film 5 was prepared on the trivalent chromium passivated aluminum alloy part by the following TRIROS YD-143 zinc plating golden yellow conversion process of Superbond Chemical Industry.

[0069] TRIROS YD-143 golden yellow conversion agent 12 mL / L, bath temperature 30℃, immersion time 80 s, and gentle air agitation.

[0070] 6. Electrophoretic coating:

[0071] The electrophoretic clear coating 6 with a thickness of 12 μm was prepared on the trivalent chromium golden yellow passivated aluminum alloy part by the following AKINI 120 electrophoretic process of Superbond Chemical Industry.

[0072] The electrophoretic coating used is AKINI 120, with a concentration of 240g / L. The pH of the electrophoretic bath solution is 4.5, the operating temperature is 28℃, and the tank voltage is 30V. The plated part is used as the cathode, and a titanium plate is used as the anode.

[0073] 7. Drying:

[0074] After electrophoretic coating, aluminum alloy parts undergo "water washing → pure water washing → drying at 140℃ for 20 minutes". Example

[0075] like Figure 1 As shown, an aluminum alloy zinc plating gold passivation coating structure includes an aluminum alloy substrate 1, and chemical zinc plating layer 2, cyanide-free copper-zinc alloy plating layer 3, potassium chloride zinc plating layer 4, trivalent chromium gold passivation film 5, and electrophoretic varnish coating 6, which are sequentially prepared from the inside to the outside on the aluminum alloy substrate 1.

[0076] 1. Pre-processing:

[0077] The current pretreatment process is used to process the aluminum alloy substrate 1 as follows: "chemical degreasing → water washing → ultrasonic degreasing → water washing → alkaline etching → water washing → brightening → water washing → micro-etching → water washing".

[0078] 2. Chemical zinc precipitation:

[0079] After the aluminum alloy parts are pretreated, a chemical zinc coating is prepared using AZIN-113 acidic aluminum zinc coating agent from Chaobang Chemical Co., Ltd. 2.

[0080] AZIN-113 acidic aluminum zinc precipitation agent 150mL / L, working temperature 25℃, zinc precipitation solution pH 3.8, zinc precipitation time 50s.

[0081] The process flow is as follows: first zinc immersion → water washing → zinc stripping → water washing → second zinc immersion → water washing.

[0082] 3. Copper-zinc alloy plating:

[0083] After pretreatment of aluminum alloy parts, a cyanide-free copper-zinc alloy coating 3 was prepared using the following polymer thiocyanate copper-zinc alloy plating process, with a coating thickness of 5μm.

[0084] Polymeric cuprous thiocyanate 23 g / L, polymeric zinc thiocyanate 11 g / L, polymeric sodium thiocyanate 165 g / L, ammonium chloride 4 g / L, plating bath pH 10.5, plating bath temperature 40℃, cathode current density 1.0 A / dm³ 2 The cathode moves at a speed of 4 m / min, and a brass plate is used as the anode.

[0085] 4. Potassium chloride zinc plating:

[0086] The aluminum alloy part is plated with copper-zinc alloy, and then a potassium chloride zinc plating layer 4 is prepared by using DETRONZIN 406 low-foaming potassium chloride zinc plating process of Superbond Chemicals, and the plating layer thickness is 12 μm.

[0087] Zinc chloride 65 g / L, potassium chloride 210 g / L, boric acid 30 g / L, DETRONZIN 406 brightener 1 mL / L, DETRONZIN 406 softener 30 mL / L, plating bath temperature 25 °C, plating solution pH 5.2, cathode current density 3 A / dm 2 .

[0088] 5. Golden yellow passivation:

[0089] 1) Trivalent chromium blue-white passivation:

[0090] The aluminum alloy part is plated with potassium chloride zinc, and then a trivalent chromium blue-white passivation film is prepared by using TRIROS TCP-187 trivalent chromium passivation agent of Superbond Chemicals.

[0091] TRIROS TCP-187A agent 30 mL / L, TRIROS TCP-187B agent 30 mL / L, passivation solution pH 2.1, passivation temperature 25 °C, air stirring, passivation time 45 s.

[0092] 2) Golden yellow conversion:

[0093] The aluminum alloy part is trivalent chromium passivated, and then a trivalent chromium golden yellow passivation film 5 is prepared by using TRIROS YD-143 zinc plating golden yellow conversion process of Superbond Chemicals.

[0094] TRIROS YD-143 golden yellow conversion agent 20 mL / L, bath temperature 30 °C, immersion time 50 s, gentle air stirring.

[0095] 6. Electrophoretic coating:

[0096] The aluminum alloy part is trivalent chromium golden yellow passivated, and then an electrophoretic clear paint coating 6 is prepared by using AKINI 120 electrophoretic process of Superbond Chemicals, and the coating thickness is 12 μm.

[0097] AKINI 120 electrophoretic paint 340 g / L, electrophoretic bath pH 4.5, operating temperature 28 °C, bath voltage 30 V, using plated parts as cathode and titanium plate as anode.

[0098] 7. Drying:

[0099] After the aluminum alloy part is electrophoretically coated, "water washing → pure water washing → 130 °C drying for 25 min" is performed.

[0100] Test Example 1:

[0101] The galvanized yellow passivation and electrophoretic painting sample of the aluminum alloy piece prepared in the embodiment 1 and the embodiment 2 is subjected to a hot shock test method according to GB / T5270-2005 "Metallic Coatings - Measurement of Adhesion - Test Methods" to measure the coating adhesion, the sample is heated to 180 DEG C in a heating furnace for 30 min, and then taken out and rapidly cooled in water at room temperature, and the coating does not appear to bubble and fall off, and the adhesion is good.

[0102] Test Example 2:

[0103] The galvanized yellow passivation and electrophoretic painting sample of the aluminum alloy piece prepared in the embodiment 1 and the embodiment 2 is subjected to a neutral salt spray test for 432 h according to GB / T10125-2021 "Salt Spray Tests in Artificial Atmospheres", and no white corrosion product is generated on the surface of the sample, and the prepared protective decorative coating has good corrosion resistance.

[0104] Test Example 3:

[0105] The galvanized yellow passivation and electrophoretic painting sample of the aluminum alloy piece prepared in the embodiment 1 and the embodiment 2 is subjected to a test for 500 h under the conditions of a temperature of 40 DEG C and a relative humidity of 93% according to GB / T2423.3-2016 "Basic Environmental Testing of Electrical and Electronic Products - Test Ca: Constant Temperature and Humidity Test Method", and no visible change is generated on the appearance of the coating. The test shows that the discoloration resistance of the coating structure meets the use requirements.

[0106] The technical solutions provided by the embodiments of the utility model are described in detail above, and 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 applicable to helping 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 all belong to the protection scope of the utility model.

Claims

1. A zinc-plated, gold-yellow passivated coating structure for aluminum alloy, characterized in that: It includes an aluminum alloy substrate, and on the aluminum alloy substrate, a chemical zinc plating layer, a cyanide-free copper-zinc alloy plating layer, a potassium chloride zinc plating layer, a trivalent chromium gold passivation film, and an electrophoretic varnish coating are sequentially prepared from the inside to the outside. The cyanide-free copper-zinc alloy coating is prepared using a polymeric thiocyanate copper-zinc alloy plating process.

2. The aluminum alloy zinc-plated golden passivated coating structure as described in claim 1, characterized in that: The thickness of the cyanide-free copper-zinc alloy coating is 3–7 μm.

3. The aluminum alloy zinc-plated golden passivated coating structure as described in claim 1, characterized in that: The thickness of the potassium chloride zinc plating layer is 8–16 μm.

4. The aluminum alloy zinc-plated golden passivated coating structure as described in claim 1, characterized in that: The thickness of the electrophoretic varnish coating is 8–17 μm.

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