Cyanide-free plating imitation gold and electrophoretic coating plating layer structure

Abstract

The utility model discloses a cyanide-free plating imitation gold and electrophoretic coating plating layer structure which comprises a steel substrate, and a cyanide-free pre-plating copper layer, an acid copper plating layer, a nickel-copper alloy plating layer, a cyanide-free imitation gold plating layer and an electrophoretic varnish coating which are sequentially prepared on the steel substrate from inside to outside. According to the cyanide-free plating imitation gold and electrophoretic coating plating layer structure disclosed by the utility model, the binding force of the plating layer is tested by a thermal shock 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 > 5270-2005 > < The acetate fog test is carried out for 168 hours according to GB / T 10125-2021 Artificial Atmosphere Corrosion Test Salt Spray Test, no red corrosive substance is generated on the surface of a plated part, and the plating layer structure has good corrosion resistance.

Description

Technical Field

[0001] This utility model belongs to the field of metal surface treatment technology, specifically relating to a cyanide-free gold plating and electrophoretic coating structure. Background Technology

[0002] Imitation gold plating boasts a vibrant color and is primarily used as a decorative coating for metal accessories such as watches, eyeglasses, and handbags. The traditional process for plating imitation gold onto steel parts typically involves sequentially applying cyanide pre-plating of copper, pyrophosphate copper plating, acid copper plating, bright nickel plating, cyanide imitation gold plating, and post-treatment. The use of cyanide is strictly controlled in my country, and the complete phasing out of cyanide electroplating processes is currently a hot research topic in the industry.

[0003] Nickel-copper alloy coatings possess excellent mechanical properties and corrosion resistance, and electroplated nickel-copper alloys are receiving increasing attention from domestic peers. [1] Nickel-copper alloy coatings have better performance than nickel coatings and are currently mainly used as decorative coatings.

[0004] The divalent copper cyanide-free copper plating process, developed over many years, still lags behind cyanide copper plating. The problem of poor adhesion when using this process on substrates such as steel has not been completely resolved. [2] .

[0005] Polymerized thiocyanate copper plating process has performance close to that of cyanide copper plating and is a promising cyanide-free copper plating process that can replace cyanide copper plating.

[0006] According to traditional processes, imitation gold plating requires chromate electrolytic protection treatment or spraying with organic varnish for protection. Both of these methods have pollution problems that need to be solved.

[0007] The resin used in high-decoration cathodic electrophoretic coatings is synthesized from acrylate or methacrylate monomers. Using this resin as the base resin for cathodic electrophoretic coatings results in a very smooth and glossy paint film with strong weather resistance, making it ideal for products with high aesthetic requirements. [3] .

[0008] References: [1]. Yang Ruisong, Li Mingtian, Wang Ying, et al. Effects of process parameters on the composition and phase structure of electroplated nickel-copper alloy coatings [J]. Electroplating and Finishing, 2014, 33(15): 633-635. [2]. Qin Zuzu, Li Jiansan, Xu Jinlai. Research progress of cyanide-free copper plating process at home and abroad [J]. Electroplating and Finishing, 2015, 34(3): 149-152. [3]. Liu Wenhua, Yao Jinshui, Fan Rui, et al. Research progress of cathodic electrophoretic coatings [J]. Journal of Qilu University of Technology, 2014, 28(4): 11-13. Summary of the Invention

[0009] To address the high pollution problem of cyanide plating for imitation gold, this invention provides a cyanide-free plating structure for imitation gold plating and electrophoretic coating. To achieve the above objective, this invention adopts the following technical solution:

[0010] A cyanide-free gold plating and electrophoretic coating structure includes a steel substrate and, sequentially prepared from the inside to the outside on the steel substrate, a cyanide-free pre-plated copper layer, an acid copper plating layer, a nickel-copper alloy plating layer, a cyanide-free gold plating layer, and an electrophoretic varnish coating.

[0011] The cyanide-free imitation gold plating is an imitation gold plating prepared by a polymeric thiocyanate copper-zinc alloy plating process, with a plating thickness of 0.05–0.15 μm.

[0012] Preferably, the thickness of the cyanide-free pre-plated copper layer is 1–4 μm.

[0013] Preferably, the thickness of the acid copper plating layer is 9–17 μm.

[0014] Preferably, the thickness of the nickel-copper alloy coating is 3–8 μm.

[0015] Preferably, the thickness of the electrophoretic varnish coating is 10–19 μm.

[0016] The electrode potential of the nickel-copper alloy coating is significantly more negative than that of the copper coating. When nickel-copper alloy is plated on an acid copper coating, the nickel-copper alloy coating is an anodic coating and provides electrochemical protection to the copper coating. This coating structure can effectively prevent corrosive media from eroding the steel substrate.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The coating structure of the cyanide-free imitation gold plating and electrophoretic coating disclosed in this utility model uses a polymer thiocyanate imitation gold plating process to prepare the imitation gold coating, which overcomes the high pollution problem of cyanide imitation gold plating.

[0019] 2. The plating structure of the cyanide-free imitation gold plating and electrophoretic coating disclosed in this utility model prepares a cyanide-free pre-plated copper layer on the steel surface, overcoming the high pollution problem of cyanide pre-plated copper.

[0020] 3. The plating structure of the cyanide-free imitation gold plating and electrophoretic coating disclosed in this utility model can significantly increase the decorative effect of the imitation gold plating by preparing an electrophoretic clear varnish coating on the cyanide-free imitation gold plating layer, and overcome the pollution problems of the chromate electrolytic protection method and the organic spraying method. Attached Figure Description

[0021] 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:

[0022] Figure 1 This is a schematic diagram of the coating structure of Embodiment 1 and Embodiment 2 of this utility model. Detailed Implementation

[0023] 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.

[0024] A cyanide-free gold plating and electrophoretic coating structure includes a steel substrate and, sequentially from the inside to the outside, a cyanide-free pre-plated copper layer, an acid copper plating layer, a nickel-copper alloy plating layer, a cyanide-free gold plating layer, and an electrophoretic varnish coating on the steel substrate.

[0025] The steel substrate is degreased, derusted, and activated according to the current pretreatment process.

[0026] After pretreatment of steel parts, a cyanide-free pre-plated copper layer is prepared using the existing polymeric thiocyanate copper plating process.

[0027] Preferably, the thickness of the cyanide-free pre-plated copper layer is 1–4 μm.

[0028] Preferably, the cyanide-free pre-plated copper layer is prepared using Zunyi Huitong's HT-810 polymeric thiocyanate copper plating process:

[0029] 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 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.

[0030] After copper plating with polymeric thiocyanate, the steel parts are coated with an acid copper layer using the existing acid copper plating process.

[0031] Preferably, the thickness of the acid copper plating layer is 9–17 μm.

[0032] After acid copper plating, steel parts are coated with nickel-copper alloy using the existing nickel-copper alloy plating process.

[0033] Preferably, the thickness of the nickel-copper alloy coating is 3–7 μm.

[0034] Preferably, the nickel-copper alloy plating is prepared using the Nistar 6070 bright nickel-copper alloy plating process from Chaobang Chemical Co., Ltd.

[0035] 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 bath pH 4.3–4.8, plating bath temperature 50℃–55℃, cathode current density 2.6–3.2 A / dm³ 2 The cathode moves at a speed of 3–5 m / min.

[0036] After plating steel parts with nickel-copper alloy, a cyanide-free imitation gold coating is prepared using a polymeric thiocyanate plating process.

[0037] Preferably, the thickness of the cyanide-free imitation gold plating layer is 0.05 to 0.15 μm.

[0038] Polymeric cuprous thiocyanate 18–25 g / L, polymeric zinc thiocyanate 8–10.5 g / L, polymeric sodium thiocyanate 125–175 g / L, ammonium chloride 3–5 g / L, plating bath pH 9.5–11.5, plating bath temperature 35℃–45℃, cathode current density 0.5–1.5 A / dm³ 2 The cathode moves at a speed of 3-5 m / min, and a brass plate is used as the anode.

[0039] After cyanide-free gold plating, steel parts are coated with an electrophoretic clear varnish using AKINI 120 electrophoretic coating process developed by Chaobang Chemical.

[0040] Preferably, the thickness of the electrophoretic varnish coating is 10–19 μm.

[0041] AKINI 120 electrophoretic paint 300~350g / L, bath solution pH 4~5, operating temperature 25℃~30℃, bath voltage 30~50V, using the plated part as the cathode and the titanium plate as the anode, the coating is dried and cured at 120℃~140℃ for 20~30min. Example 1

[0042] like Figure 1 As shown, a cyanide-free gold plating and electrophoretic coating structure includes a steel substrate 1, and a cyanide-free pre-plated copper layer 2, an acid copper plating layer 3, a nickel-copper alloy plating layer 4, a cyanide-free gold plating layer 5, and an electrophoretic varnish coating 6, which are sequentially prepared from the inside to the outside on the steel substrate 1.

[0043] 1. Pre-processing:

[0044] The current pretreatment process is used to perform the following steps on the steel substrate 1: "alkaline chemical degreasing → water washing → pickling → water washing → alkaline cathodic electrolytic degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → activation → water washing".

[0045] 2. Polymerized thiocyanate copper plating:

[0046] After pretreatment of the steel parts, a cyanide-free pre-plated copper layer 2 was prepared using the polymer thiocyanate copper plating process of Zunyi Huitong, with a plating thickness of 3μm.

[0047] Polymeric cuprous thiocyanate 19 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 50℃, plating solution pH 12.8, cathode current density 0.8 A / dm³ 2 The cathode moves at a speed of 5 m / min, and the anode current density is 0.4 A / dm³. 2 An oxygen-free electrolytic copper horn was used as the anode.

[0048] 3. Acid copper plating:

[0049] After copper plating with polymeric thiocyanate, the steel parts are coated with an acid copper layer 3 using the existing acid copper plating process, with a coating thickness of 12μm.

[0050] 4. Nickel-plated copper alloy:

[0051] After acid copper plating, the steel parts were coated with Nistar 6070 bright nickel-copper alloy using Chaobang Chemical to prepare a nickel-copper alloy coating 4 with a coating thickness of 5μm.

[0052] Nickel sulfate hexahydrate 200 g / L, copper sulfate pentahydrate 10 g / L, trisodium citrate 60 g / L, disodium hydroxyethylidene diphosphonate 25 g / L, boric acid 32 g / L, sodium chloride 7 g / L, NISTAR 6070 brightener 0.4 mL / L, NISTAR 6071 auxiliary agent 8 mL / L, NI-35 wetting agent 0.7 mL / L, plating bath pH 4.6, plating tank temperature 53℃, cathode current density 3 A / dm³ 2 The cathode moves at a speed of 4 m / min.

[0053] 5. Cyanide-free imitation gold plating:

[0054] After plating steel parts with nickel-copper alloy, a cyanide-free imitation gold plating layer 5 is prepared using the following polymer thiocyanate plating imitation gold process, with a plating thickness of 0.1 μm.

[0055] The plating bath composition includes: 24 g / L cuprous thiocyanate, 10 g / L zinc thiocyanate, 160 g / L sodium thiocyanate, and 4.2 g / L ammonium chloride. The pH of the plating bath is 9.7, the bath temperature is 38℃, and the cathode current density is 1.0 A / dm³. 2The cathode moves at a speed of 4 m / min, and a brass plate is used as the anode.

[0056] 6. Electrophoretic coating:

[0057] After cyanide-free gold plating, the steel parts were coated with an electrophoretic clear varnish 6 using the AKINI 120 electrophoretic coating process from Chaobang Chemical Co., Ltd. The coating thickness was 15μm.

[0058] The AKINI 120 electrophoretic paint is 340g / L, the bath pH is 4.3, the operating temperature is 26℃, the bath voltage is 40V, the plated part is used as the cathode, and the titanium plate is used as the anode.

[0059] 7. Drying and curing:

[0060] After electrophoretic coating, steel parts are dried and cured at 135℃ for 20 minutes. Example 2

[0061] like Figure 1 As shown, a cyanide-free gold plating and electrophoretic coating structure includes a steel substrate 1, and a cyanide-free pre-plated copper layer 2, an acid copper plating layer 3, a nickel-copper alloy plating layer 4, a cyanide-free gold plating layer 5, and an electrophoretic varnish coating 6, which are sequentially prepared from the inside to the outside on the steel substrate 1.

[0062] 1. Pre-processing:

[0063] The current pretreatment process is used to perform the following steps on the steel substrate 1: "alkaline chemical degreasing → water washing → pickling → water washing → alkaline cathodic electrolytic degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → activation → water washing".

[0064] 2. Polymerized thiocyanate copper plating:

[0065] After pretreatment of the steel parts, a cyanide-free pre-plated copper layer 2 was prepared using the polymer thiocyanate copper plating process of Zunyi Huitong, with a plating thickness of 2μm.

[0066] 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 53℃, plating solution pH 12.6, 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.

[0067] 3. Acid copper plating:

[0068] After copper plating with polymeric thiocyanate, the steel parts are coated with an acid copper layer 3 using the existing acid copper plating process, with a coating thickness of 13μm.

[0069] 4. Nickel-plated copper alloy:

[0070] After acid copper plating, the steel parts were coated with Nistar 6070 bright nickel-copper alloy using Chaobang Chemical to prepare a nickel-copper alloy coating 4 with a coating thickness of 5μm.

[0071] Nickel sulfate hexahydrate 190 g / L, copper sulfate pentahydrate 9 g / L, trisodium citrate 55 g / L, disodium hydroxyethylidene diphosphonate 22 g / L, boric acid 30 g / L, sodium chloride 6 g / L, NISTAR 6070 brightener 0.5 mL / L, NISTAR 6071 auxiliary agent 8 mL / L, NI-35 wetting agent 0.6 mL / L, plating bath pH 4.5, plating tank temperature 52℃, cathode current density 2.7 A / dm³ 2 The cathode moves at a speed of 4 m / min.

[0072] 5. Cyanide-free imitation gold plating:

[0073] After plating steel parts with nickel-copper alloy, a cyanide-free imitation gold plating layer 5 is prepared using the following polymer thiocyanate plating imitation gold process, with a plating thickness of 0.1 μm.

[0074] The plating solution contained 19 g / L of polycuprous thiocyanate, 8.5 g / L of polyzinc thiocyanate, 140 g / L of polysodium thiocyanate, and 3.8 g / L of ammonium chloride. The pH of the plating bath was 10.2, the bath temperature was 42℃, and the cathode current density was 1.0 A / dm³. 2 The cathode moves at a speed of 4 m / min, and a brass plate is used as the anode.

[0075] 6. Electrophoretic coating:

[0076] After cyanide-free gold plating, the steel parts were coated with an electrophoretic clear varnish 6 using the AKINI 120 electrophoretic coating process from Chaobang Chemical Co., Ltd. The coating thickness was 15μm.

[0077] The AKINI 120 electrophoretic paint is 310g / L, the bath pH is 4.7, the operating temperature is 28℃, the bath voltage is 40V, the plated part is used as the cathode, and the titanium plate is used as the anode.

[0078] 7. Drying and curing:

[0079] After electrophoretic coating, steel parts are dried and cured at 125℃ for 30 minutes.

[0080] Experimental Example 1:

[0081] The steel samples prepared in Examples 1 and 2, which were cyanide-free gold-plated and electrophoretic coated, showed no rust on their surfaces after 168 hours of acetic acid spray testing according to GB / T10125–2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", which is far superior to the requirement of GB / T 9797–2022 "Metallic Coatings - Nickel + Chromium and Copper + Nickel + Chromium Electroplating" for 48 hours of acetic acid spray testing.

[0082] Experimental Example 2:

[0083] The steel surfaces prepared in Examples 1 and 2 were subjected to cyanide-free gold plating and electrophoretic coating. The adhesion of the coating was tested by thermal shock method according to GB / T5270–2005 "Review of Test Methods for Adhesion Strength of Electrodeposition and Chemical Deposition Layers on Metal Substrates". The coated parts were heated to 180°C in a heating furnace and held for 30 minutes. After being taken out, they were quenched in water at room temperature. No blistering or peeling of the coating occurred. The coating structure prepared by this invention has good adhesion.

[0084] Experimental Example 3:

[0085] The steel samples prepared in Examples 1 and 2, which were cyanide-free gold-plated and electrophoretic coated, were tested for 600 hours at 40°C and 93% relative humidity according to GB / T2423.3-2016 "Basic Environmental Testing Procedures for Electrical and Electronic Products - Test Ca: Constant Damp Heat Test Method". No visible changes were observed in the appearance of the coating, indicating that the coating structure has good resistance to discoloration.

[0086] 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 for helping to 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 cyanide-free gold-like plated and electrophoretically painted plated structure, characterized by: The steel substrate is provided with a cyanide-free pre-copper plating layer, an acid copper plating layer, a nickel-copper alloy plating layer, a cyanide-free imitation gold plating layer and an electrophoretic varnish coating layer in sequence from inside to outside. The cyanide-free imitation gold plating layer is an imitation gold plating layer prepared by a polymeric thiocyanate copper-zinc alloy plating process, and has a thickness of 0.05-0.15 μm.

2. The cyanide-free gold-like plated and electrophoretically painted plated structure according to claim 1, characterized in that: The cyanide-free pre-copper plating layer has a thickness of 1-4 μm.

3. The cyanide-free gold-like plated and electrophoretically painted plated structure according to claim 1, characterized in that: The acid copper plating layer has a thickness of 9-17 μm.

4. The cyanide-free gold-like plated and electrophoretically painted plated structure according to claim 1, characterized in that: The nickel-copper alloy plating layer has a thickness of 3-8 μm.

5. The cyanide-free gold-like plated and electrophoretically painted plated structure according to claim 1, characterized in that: The electrophoretic varnish coating layer has a thickness of 10-19 μm.

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