Plating layer structure for functional gold plating of aluminum alloy machined part

Abstract

The utility model discloses a functional gold-plated coating structure of an aluminum alloy machining part, which comprises an aluminum alloy substrate, and a chemical zinc deposition layer, a cyanide-free pre-plated copper layer, an acid copper coating, a high-corrosion-resistance nickel-phosphorus alloy coating and a gold-plated layer which are sequentially prepared on the aluminum alloy substrate from inside to outside. According to the functional gold-plated coating structure of the aluminum alloy machined part disclosed by the utility model, the binding force of the coating is measured by a thermal shock test method according to the 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 360 h 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 has good corrosion resistance.

Description

Technical Field

[0001] This utility model belongs to the field of metal electroplating, specifically relating to a plating structure for functional gold plating of aluminum alloy machined parts. Background Technology

[0002] Gold plating has excellent corrosion resistance and an elegant and beautiful appearance. It is generally suitable for preparing functional plating layers for high-end electronic products and decorative plating layers for jewelry.

[0003] Traditionally, machined aluminum alloy parts undergo chemical zinc plating followed by cyanide copper plating to prepare a pre-plated copper layer, which is then subjected to pyrophosphate copper plating, acid copper plating, and bright nickel plating. Cyanide is a highly toxic compound, and its use poses significant pollution and risk. Previous cyanide-free copper plating technologies require further breakthroughs to truly and completely replace cyanide copper plating. [1] Therefore, it is particularly important to research and develop a completely new cyanide-free copper plating process.

[0004] The utility model patent with authorization announcement number CN 212103011 U discloses "A coating structure for environmentally friendly gold plating of aluminum alloy die castings". The coating structure includes an aluminum alloy substrate and, from the inside to the outside, a zinc immersion layer, an acidic zinc-nickel alloy coating, a chemical nickel plating layer, a pyrophosphate copper plating layer, an acid copper plating layer, a bright nickel plating layer, a nickel-phosphorus alloy plating layer, and a gold plating layer. This coating structure is too complex and has a high production cost.

[0005] Polymeric thiocyanate copper plating is a newly introduced cyanide-free copper plating process. Its characteristic is that it uses polycuprous thiocyanate as the main salt and sodium thiocyanate as the complexing agent. Its process performance is currently the closest to that of cyanide copper plating.

[0006] High corrosion-resistant nickel-phosphorus alloy coatings exhibit significantly higher corrosion resistance and hardness than bright nickel coatings, making them suitable as an undercoat for noble metal coatings in the preparation of functional coatings. Summary of the Invention

[0007] To address the high contamination issue associated with preparing the pre-copper layer using cyanide copper plating after chemical zinc immersion on machined aluminum alloy parts, this invention provides a functional gold plating structure for machined aluminum alloy parts. To achieve the above objective, this invention employs the following technical solution:

[0008] A functional gold plating structure for machined aluminum alloy parts includes an aluminum alloy substrate and, sequentially prepared from the inside out, a chemical zinc plating layer, a cyanide-free pre-plated copper layer, an acid copper plating layer, a high corrosion-resistant nickel-phosphorus alloy plating layer, and a gold plating layer on the aluminum alloy substrate.

[0009] The cyanide-free pre-plated copper layer is a copper plating layer prepared using a polymeric thiocyanate copper plating process;

[0010] The thickness of the cyanide-free pre-plated copper layer is 4–9 μm.

[0011] Preferably, the thickness of the acid copper plating layer is 10–20 μm.

[0012] Preferably, the thickness of the high corrosion resistant nickel-phosphorus alloy coating is 6–12 μm.

[0013] Preferably, the thickness of the gold plating layer is 0.3 to 3 μm.

[0014] The surface of machined aluminum alloy parts is non-porous, allowing for direct acid copper plating after pre-plating with polythiocyanate without the need for additional pyrophosphate copper plating on the pre-plated copper layer. Acid copper plating on the polythiocyanate copper layer increases the gloss of the coating surface. A high-corrosion-resistant nickel-phosphorus alloy is then plated on the acid copper layer. The nickel-phosphorus alloy coating has a relatively negative electrode potential, making it an anodic coating for the copper layer, which effectively blocks corrosive media from eroding the substrate. Using the high-corrosion-resistant nickel-phosphorus alloy coating as the undercoat for gold plating further enhances the corrosion resistance of the coating.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The functional gold plating structure of the aluminum alloy machined parts disclosed in this utility model adopts a polymer thiocyanate copper plating process instead of the highly toxic cyanide copper plating process, which is environmentally friendly.

[0017] 2. The functional gold plating structure of the aluminum alloy machined parts prepared by this utility model has good coating adhesion and meets the requirements of GB / T 5270-2005 standard. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the present invention and form part of this application, do not constitute an undue limitation of the present invention. In the drawings:

[0019] Figure 1 This is a schematic diagram of the coating structure of Embodiment 1 and Embodiment 2 of this utility model. Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0021] A chemical zinc plating layer, a cyanide-free copper plating layer, an acid copper plating layer, a high corrosion-resistant nickel-phosphorus alloy plating layer, and a gold plating layer are sequentially prepared on an aluminum alloy machined part substrate from the inside out.

[0022] The existing pretreatment process is used to degrease, alkali corrosion, brighten, and micro-corrode aluminum alloy machined parts.

[0023] After pretreatment, aluminum alloy machined parts are prepared with a chemical zinc coating using the current chemical zinc plating process.

[0024] Preferably, the chemical zinc plating layer is prepared using the ALBUME AS-699 cyanide-free aluminum zinc plating process from Chaobang Chemical Co., Ltd.

[0025] ALBUME AS-699 cyanide-free aluminum zinc precipitation agent, 160-220 mL / L, operating temperature 20℃-30℃, zinc precipitation time 60-120 s. The zinc precipitation agent contains 6-9 g / L of zinc ions and 0.16-0.20 g / L of copper ions.

[0026] Preferably, the chemical zinc plating layer is prepared using Chaobang Chemical's AZIN-113 acidic aluminum zinc plating process:

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

[0028] After chemical zinc plating, aluminum alloy machined parts are prepared with a cyanide-free pre-plated copper layer using a polymeric thiocyanate copper plating process.

[0029] Preferably, the thickness of the cyanide-free pre-plated copper layer is 4–9 μm.

[0030] Preferably, the cyanide-free pre-plated copper layer is prepared using Zunyi Huitong's HT-810 polymeric thiocyanate copper plating process:

[0031] Polymeric cuprous thiocyanate 17–23 g / L, polymeric sodium thiocyanate 100–160 g / L, potassium sodium tartrate 8–12 g / L, HT-810 brightener 1–2 mL / L, HT-810 leveling agent 2–4 mL / L, plating bath temperature 45℃–55℃, plating solution pH range 12–13, cathode current density 0.5–1.0 A / dm³ 2 The cathode moves at a speed of 4–6 m / min, and the anode current density is ≤0.5 A / dm². 2 An oxygen-free electrolytic copper horn (or copper granules) is used as the anode.

[0032] After cyanide-free copper pre-plating, aluminum alloy machined parts are coated with acid copper using the existing acid copper plating process.

[0033] Preferably, the thickness of the acid copper plating layer is 10–20 μm.

[0034] After acid copper plating, aluminum alloy machined parts are coated with a high-corrosion-resistant nickel-phosphorus alloy using the existing high-corrosion-resistant nickel-phosphorus alloy plating process.

[0035] Preferably, the thickness of the high corrosion resistant nickel-phosphorus alloy coating is 6–12 μm.

[0036] Preferably, the high corrosion-resistant nickel-phosphorus alloy coating is prepared using the PROTEXYER 8713 high corrosion-resistant nickel-phosphorus alloy plating process from Chaobang Chemical Co., Ltd.

[0037] PROTEXYER 8713 MU plating bath starter 580~620mL / L, nickel sulfate 280~340g / L, plating bath pH range 2.6~2.7, plating bath temperature 60℃~65℃, cathode current density 3~6A / dm³ 2 The cathode moves at a speed of 3–5 m / min.

[0038] Aluminum alloy machined parts are plated with high corrosion-resistant nickel-phosphorus alloy and then the gold plating layer is prepared using the current gold plating process.

[0039] Preferably, the thickness of the gold plating layer is 0.3 to 3 μm.

[0040] Preferably, the gold plating layer is prepared using the BALILOY 300 FC 3N acidic gold plating process from Chaobang Chemical Co., Ltd.

[0041] BALILOY 300 FC MU plating bath starter 800mL / L, BALILOY CO cobalt salt 20mL / L, potassium gold cyanide 3.7g / L, plating bath pH range 3.6~4.0, operating temperature 30℃~40℃, cathode current density 0.5~0.7A / dm³ 2 The cathode moves at a speed of 4–6 m / min.

[0042] After the machined aluminum alloy parts are gold-plated and washed with water, they are dried at 70℃~80℃ for 15~25 minutes. Example

[0043] like Figure 1 As shown, a functional gold plating structure for an aluminum alloy machined part includes an aluminum alloy substrate 1, and a chemical zinc plating layer 2, a cyanide-free pre-plated copper layer 3, an acid copper plating layer 4, a high corrosion-resistant nickel-phosphorus alloy plating layer 5, and a gold plating layer 6, which are sequentially prepared from the inside to the outside on the aluminum alloy substrate 1.

[0044] 1. Pre-processing:

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

[0046] 2. Chemical zinc precipitation:

[0047] After pretreatment, aluminum alloy machined parts are coated with a chemical zinc layer using Chaobang Chemical's ALBUME AS-699 cyanide-free aluminum zinc plating process.

[0048] ALBUME AS-699 cyanide-free aluminum zinc precipitation agent, 200 mL / L, operating temperature 25℃, zinc precipitation time 90 s. The zinc precipitation agent contains 7 g / L zinc ions and 0.18 g / L copper ions.

[0049] The specific process is as follows: "First zinc immersion → water washing → zinc stripping → water washing → second zinc immersion → water washing".

[0050] 3. Cyanide-free pre-plated copper:

[0051] After chemical zinc plating, aluminum alloy machined parts are prepared with a cyanide-free pre-plated copper layer 3 using Zunyi Huitong's HT-810 polymer thiocyanate copper plating process, with a plating thickness of 5μm.

[0052] Polymeric cuprous thiocyanate 18 g / L, polymeric sodium thiocyanate 120 g / L, potassium sodium tartrate 10 g / L, HT-810 brightener 1.5 mL / L, HT-810 leveling agent 3 mL / L, plating bath temperature 53℃, plating solution pH 12.3, cathode current density 0.7 A / dm³ 2 The cathode moves at a speed of 5 m / min, and the anode current density is 0.4 A / dm². 2 An oxygen-free electrolytic copper horn was used as the anode.

[0053] 4. Acid copper plating:

[0054] After cyanide-free copper plating, the aluminum alloy machined parts are prepared with acid copper plating layer 4 using the current acid copper plating process, with a plating thickness of 18μm.

[0055] 5. High corrosion resistant nickel-phosphorus alloy plating:

[0056] After acid copper plating, the machined aluminum alloy parts were coated with a high corrosion resistant nickel-phosphorus alloy using the PROTEXYER 8713 process from Chaobang Chemical to prepare a high corrosion resistant nickel-phosphorus alloy coating 5 with a thickness of 8μm.

[0057] PROTEXYER 8713 MU plating bath starter 590mL / L, nickel sulfate 290g / L, plating bath pH 2.7, plating bath temperature 62℃, cathode current density 4A / dm³ 2 The cathode moves at a speed of 4 m / min.

[0058] 6. Gold plating:

[0059] After the aluminum alloy machined parts are plated with high corrosion resistant nickel-phosphorus alloy, a gold plating layer 6 is prepared using the BALILOY 300 FC 3N acidic gold plating process of Chaobang Chemical, with a plating thickness of 1.5μm.

[0060] The plating bath composition consists of 800 mL / L BALILOY 300 FC MU plating starter, 20 mL / L BALILOY CO cobalt salt, 3.7 g / L potassium gold cyanide, a pH of 3.8, a bath temperature of 33°C, and a cathode current density of 0.6 A / dm³. 2 The cathode moves at a speed of 5 m / min.

[0061] 7. Drying:

[0062] After the machined aluminum alloy parts are gold-plated and washed with water, they are dried at 80℃ for 15 minutes. Example

[0063] like Figure 1 As shown, a functional gold plating structure for an aluminum alloy machined part includes an aluminum alloy substrate 1, and a chemical zinc plating layer 2, a cyanide-free pre-plated copper layer 3, an acid copper plating layer 4, a high corrosion-resistant nickel-phosphorus alloy plating layer 5, and a gold plating layer 6, which are sequentially prepared from the inside to the outside on the aluminum alloy substrate 1.

[0064] 1. Pre-processing:

[0065] The aluminum alloy machining substrate 1 is subjected to the following process: "chemical degreasing → water washing → ultrasonic degreasing → water washing → alkaline etching → water washing → brightening → water washing → micro-etching → water washing".

[0066] 2. Chemical zinc precipitation:

[0067] After pretreatment, aluminum alloy machined parts are coated with a chemical zinc layer using Chaobang Chemical's AZIN-113 acidic aluminum zinc plating process.

[0068] AZIN-113 acidic aluminum zinc precipitation agent 200mL / L, working temperature 25℃, bath pH 4.2, zinc precipitation time 60s.

[0069] The specific process is as follows: "First zinc immersion → water washing → zinc stripping → water washing → second zinc immersion → water washing".

[0070] 3. Cyanide-free pre-plated copper:

[0071] After chemical zinc plating, aluminum alloy machined parts are prepared with a cyanide-free pre-plated copper layer 3 using Zunyi Huitong's HT-810 polymer thiocyanate copper plating process, with a plating thickness of 7μm.

[0072] Polymeric cuprous thiocyanate 22 g / L, polymeric sodium thiocyanate 150 g / L, potassium sodium tartrate 10 g / L, HT-810 brightener 1.5 mL / L, HT-810 leveling agent 3 mL / L, plating bath temperature 52℃, plating solution pH 12.1, cathode current density 0.8 A / dm³ 2 The cathode moves at a speed of 5 m / min, and the anode current density is 0.3 A / dm². 2 Oxygen-free electrolytic copper particles are used as the anode.

[0073] 4. Acid copper plating:

[0074] After cyanide-free copper plating, the aluminum alloy machined parts are prepared with acid copper plating layer 4 using the current acid copper plating process, with a plating thickness of 14μm.

[0075] 5. High corrosion resistant nickel-phosphorus alloy plating:

[0076] After acid copper plating, the machined aluminum alloy parts were coated with a high corrosion resistant nickel-phosphorus alloy using the PROTEXYER 8713 process from Chaobang Chemical to prepare a high corrosion resistant nickel-phosphorus alloy coating 5 with a thickness of 10μm.

[0077] PROTEXYER 8713 MU plating bath starter 610mL / L, nickel sulfate 330g / L, plating bath pH 2.6, plating bath temperature 62℃, cathode current density 4A / dm³ 2 The cathode moves at a speed of 4 m / min.

[0078] 6. Gold plating:

[0079] After being plated with a high-corrosion-resistant nickel-phosphorus alloy, the machined aluminum alloy parts were treated with a gold plating layer 6 prepared using Chaobang Chemical's BALILOY 300 FC 3N acidic gold plating process. The plating layer thickness was 1.5μm.

[0080] The plating solution used was 800 mL / L of BALILOY 300 FC MU plating starter, 20 mL / L of BALILOY CO cobalt salt, 3.7 g / L of potassium gold cyanide, with a pH of 3.8, an operating temperature of 35℃, and a cathode current density of 0.6 A / dm³. 2 The cathode moves at a speed of 5 m / min.

[0081] 7. Drying:

[0082] After the machined aluminum alloy parts are gold-plated and washed with water, they are dried at 70℃ for 25 minutes.

[0083] Experimental Example 1:

[0084] The functional gold-plated samples prepared in Examples 1 and 2 were tested for adhesion using the thermal shock test method according to GB / T 5270-2005 "Review of Test Methods for Adhesion Strength of Electrodeposited and Chemically Deposited Metallic Coatings on Metal Substrates". The plated parts were heated to 220°C in a furnace and held for 30 minutes, then removed and rapidly cooled in room temperature water. No blistering or peeling occurred in the plating, indicating good adhesion of the prepared plating.

[0085] Experimental Example 2:

[0086] The functional gold-plated samples prepared in Examples 1 and 2 were subjected to a neutral salt spray test for 360 hours according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". No corrosion products were generated on the surface of the plated parts, and the prepared coating has good corrosion resistance.

[0087] The technical solutions provided by the embodiments of this utility model have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of this utility model. The descriptions of the embodiments above are only intended to help understand the principles of the embodiments of this utility model. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model.

Claims

1. A functional gold plating structure for machined aluminum alloy parts, characterized in that: It includes an aluminum alloy substrate, and chemical zinc plating, cyanide-free copper plating, acid copper plating, high corrosion-resistant nickel-phosphorus alloy plating, and gold plating layer sequentially prepared from the inside to the outside on the aluminum alloy substrate. The cyanide-free pre-plated copper layer is a copper plating layer prepared using a polymeric thiocyanate copper plating process; The thickness of the cyanide-free pre-plated copper layer is 4–9 μm.

2. The plating structure for functional gold plating of aluminum alloy machined parts as described in claim 1, characterized in that: The thickness of the acid copper plating layer is 10–20 μm.

3. The plating structure for functional gold plating of aluminum alloy machined parts as described in claim 1, characterized in that: The thickness of the high corrosion resistant nickel-phosphorus alloy coating is 6–12 μm.

4. The plating structure for functional gold plating of aluminum alloy machined parts as described in claim 1, characterized in that: The thickness of the gold plating layer is 0.3–3 μm.

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