Plating layer structure plated with gold substitute and electrophoretic paint

Abstract

The utility model discloses a plating structure plated with gold substitute and electrophoretic paint, which comprises a zinc alloy die casting base body, and a polythiocyanate copper plating layer, a pyrophosphate copper plating layer, an acid copper plating layer, a bright nickel plating layer, a gold substitute plating layer and an electrophoretic varnish coating which are sequentially prepared on the zinc alloy die casting base body from inside to outside. According to the plating layer structure plated with the gold substitute and the electrophoretic paint, the binding force of the plating layer is tested by a thermal shock method according to the GB / T 5270-2005 Test Method for Adhesive Strength of Metal Covering Layer Electro-Deposition and Chemical Deposition Layer on Metal Matrix, and the binding force meets the standard requirement; a neutral salt spray test is carried out for 240 hours according to GB / T 10125-2021 Artificial Atmosphere Corrosion Test Salt Spray Test, no corrosive substance is generated on the surface of a plated part, and a plated layer has good corrosion resistance.

Description

Technical Field

[0001] The utility model belongs to the technical field of metal surface treatment, and particularly relates to a coating structure for gold plating and electrophoretic painting. Background Art

[0002] When the tin content is 13% - 15%, the color is similar to 18K - 24K gold and presents a golden yellow color. The electroplating industry uses copper - tin alloy coatings as substitute - gold coatings, which are deeply loved by people. The copper - tin alloy substitute - gold coating has the advantages of small porosity, vivid color, excellent corrosion resistance and appropriate hardness, can prevent the diffusion of the underlying metal to the surface layer, and prevent the discoloration of the metal coating. It has now been widely used in the fields of lamps, furniture, boxes, clocks, jewelry, daily hardware and the construction industry. [1] Compared with the copper - zinc alloy imitation - gold coating, the copper - tin alloy substitute - gold coating has a color closer to gold, and is an ideal coating for replacing the gold - plating layer.

[0003] The traditional process for gold plating on zinc - alloy die - castings is usually to carry out cyanide copper plating, pyrophosphate copper plating, acid copper plating, bright nickel plating, gold plating, chromate electrolytic protection or painting on the zinc - alloy substrate in sequence.

[0004] Cyanide copper plating has high toxicity and high risk. The industry is actively developing cyanide - free copper - plating processes to replace the traditional cyanide copper plating. However, the problem of the bonding force between the coating and the substrate existing in the developed divalent - copper cyanide - free copper - plating process still needs to be studied and improved. [2] Therefore, at present, many electroplating factories still have to use the cyanide copper - plating process to pre - plate copper on zinc - alloy die - castings.

[0005] The newly developed polymeric thiocyanate copper - plating process uses polymeric cuprous thiocyanate as the main salt and polymeric sodium thiocyanate as the complexing agent. Its process performance is close to that of cyanide copper plating, but it does not have the high toxicity of cyanide copper plating.

[0006] References: [1]. Huang Lingfei, Zeng Zhen'ou, Xie Jinping, et al. Research on cyanide - free copper - tin alloy imitation - gold electroplating additives [J]. Surface Technology, 2015, 34(11): 589 - 594. [2]. Qin Zuzu, Li Jiansan, Xu Jinlai. Research progress of cyanide - free copper - plating processes at home and abroad [J]. Electroplating & Finishing, 2015, 34(3): 149 - 152. Content of the Utility Model

[0007] In order to solve the pollution problems of cyanide pre - plating copper on zinc - alloy die - castings and the post - treatment of the substitute - gold coating, the utility model provides a coating structure for gold plating and electrophoretic painting. To achieve the above purpose, the utility model adopts the following technical solutions:

[0008] A gold-plated and electrophoretic coating structure includes a zinc alloy die-cast substrate, and a polymeric thiocyanate copper plating layer, a pyrophosphate copper plating layer, an acid copper plating layer, a bright nickel plating layer, a gold-plated layer, and an electrophoretic varnish coating sequentially prepared on the zinc alloy die-cast substrate from the inside to the outside;

[0009] The gold-plated layer is a coating prepared by a copper-tin alloy plating process, and the coating thickness is 0.1 - 0.3 μm.

[0010] Preferably, the thickness of the polymeric thiocyanate copper plating layer is 3 - 6 μm.

[0011] Preferably, the thickness of the pyrophosphate copper plating layer is 5 - 10 μm.

[0012] Preferably, the thickness of the acid copper plating layer is 8 - 16 μm.

[0013] Preferably, the thickness of the bright nickel plating layer is 1 - 5 μm.

[0014] Preferably, the thickness of the electrophoretic varnish coating is 9 - 18 μm.

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

[0016] 1. The gold-plated and electrophoretic coating structure disclosed by the present utility model overcomes the high pollution problem of pre-plating copper on zinc alloy die-castings using the traditional cyanide copper plating process;

[0017] 2. The gold-plated and electrophoretic coating structure disclosed by the present utility model overcomes the pollution problems of traditional chromate electrolytic protection or spray painting. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0019] Figure 1 is a schematic diagram of the coating structure of Embodiment 1 and Embodiment 2 of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The present utility model will be described in detail below in conjunction with the drawings and specific embodiments. Here, the schematic embodiments and descriptions of the present utility model are used to explain the present utility model, but do not constitute a limitation to the present utility model.

[0021] A gold-plated and electrophoretic coating structure includes a zinc alloy die-cast substrate, and a polymeric thiocyanate copper plating layer, a pyrophosphate copper plating layer, an acid copper plating layer, a bright nickel plating layer, a gold-plated layer, and an electrophoretic varnish coating sequentially prepared on the zinc alloy die-cast substrate from the inside to the outside.

[0022] The matrix of zinc alloy die-castings is subjected to dewaxing, degreasing, and activation treatment by using the current pretreatment process.

[0023] A copper polythiocyanate plating layer is prepared on the pretreated zinc alloy die-castings by using the copper polythiocyanate plating process.

[0024] Preferably, the thickness of the copper polythiocyanate plating layer is 3 - 6 μm.

[0025] Preferably, the copper polythiocyanate plating layer is prepared by using the HT-810 copper polythiocyanate plating process of Zunyi Huitong:

[0026] Copper(I) polythiocyanate 17 - 23 g / L, sodium polythiocyanate 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, bath temperature 45°C - 55°C, bath pH value 12 - 13, cathode current density 0.5 - 1.0 A / dm 2 , cathode moving speed 4 - 6 m / min, anode current density ≤ 0.5 A / dm 2 , and an oxygen-free electrolytic copper angle (or copper grains) is used as the anode.

[0027] A pyrophosphate copper plating layer is prepared on the zinc alloy die-castings plated with copper polythiocyanate by using the current pyrophosphate copper plating process.

[0028] Preferably, the thickness of the pyrophosphate copper plating layer is 5 - 10 μm.

[0029] An acid copper plating layer is prepared on the zinc alloy die-castings plated with pyrophosphate copper by using the current acid copper plating process.

[0030] Preferably, the thickness of the acid copper plating layer is 8 - 16 μm.

[0031] A bright nickel plating layer is prepared on the zinc alloy die-castings plated with acid copper by using the current bright nickel plating process.

[0032] Preferably, the thickness of the bright nickel plating layer is 1 - 5 μm.

[0033] A gold substitute plating layer is prepared on the zinc alloy die-castings plated with bright nickel by using the current gold substitute plating process.

[0034] Preferably, the thickness of the gold substitute plating layer is 0.1 - 0.3 μm.

[0035] Preferably, the gold substitute plating layer is prepared by using the YB-223 bright brass-tin gold substitute plating process of Chaobang Chemical Industry:

[0036] Potassium cyanide 50 - 80 g / L, cuprous cyanide 18 - 25 g / L, zinc cyanide 6 - 10 g / L, potassium hydroxide 1 - 4 g / L, CTA-604 tin salt 1 - 4 g / L, CTA-606 Initial bath starter 80 - 120 mL / L, CTA-606 Bri brightener 10 - 25 mL / L, CTA-606 Carrier auxiliary agent 3 - 10 mL / L, plating solution pH value 12 - 13, plating bath temperature 48 °C - 60 °C, cathode current density 0.6 - 1.8 A / dm 2 , cathode movement 4 - 6 m / min.

[0037] Prepare an electrophoretic clear lacquer coating on a zinc alloy die-casting after gold plating.

[0038] Preferably, the thickness of the electrophoretic clear lacquer coating is 9 - 18 μm.

[0039] Preferably, the electrophoretic clear lacquer coating is prepared by the AKINI 120 electrophoretic process developed by Superbond Chemical Industry:

[0040] AKINI 120 electrophoretic paint 300 - 350 g / L, electrophoretic bath solution pH value 4 - 5, operating temperature 25 °C - 30 °C, bath voltage 30 - 50 V, using the plated part as the cathode and a titanium plate as the anode, and the coating is dried and cured at 120 °C - 140 °C for 20 - 30 min. Example 1

[0041] As Figure 1 shown, a gold-plated and electrophoretically painted coating structure includes a zinc alloy die-casting substrate 1, and a copper thiocyanate plating layer 2, a pyrophosphate copper plating layer 3, an acid copper plating layer 4, a bright nickel plating layer 5, a gold plating layer 6, and an electrophoretic clear lacquer coating 7 sequentially prepared from the inside to the outside on the zinc alloy die-casting substrate 1.

[0042] 1. Pretreatment:

[0043] Perform "chemical dewaxing → water washing → ultrasonic dewaxing → water washing → ultrasonic degreasing → water washing → activation → water washing" on the zinc alloy die-casting substrate 1 according to the current pretreatment process.

[0044] 2. Copper thiocyanate plating:

[0045] Prepare a copper thiocyanate plating layer 2 on the pretreated zinc alloy die-casting by using the HT-810 copper thiocyanate plating process of Zunyi Huitong, and the plating layer thickness is 4 μm.

[0046] Copper thiocyanate 19 g / L, 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, bath temperature 50 °C, bath pH 12.8, cathode current density 0.8 A / dm 2 , cathode moving speed 5 m / min, anode current density 0.4 A / dm 2 , using oxygen-free electrolytic copper angle as anode.

[0047] 3. Copper pyrophosphate plating:

[0048] On the zinc alloy die-casting parts plated with copper thiocyanate, the current copper pyrophosphate plating process is used to prepare the copper pyrophosphate plating layer 3 with a coating thickness of 6 μm.

[0049] 4. Acid copper plating:

[0050] On the zinc alloy die-casting parts plated with copper pyrophosphate, the current acid copper plating process is used to prepare the acid copper plating layer 4 with a coating thickness of 10 μm.

[0051] 5. Bright nickel plating:

[0052] On the zinc alloy die-casting parts plated with acid copper, the current bright nickel plating process is used to prepare the bright nickel plating layer 5 with a coating thickness of 2 μm.

[0053] 6. Gold replacement plating:

[0054] On the zinc alloy die-casting parts plated with bright nickel, the YB-223 bright brass-tin gold replacement plating process of Superbond Chemical Industry is used to prepare the gold replacement plating layer 6 with a coating thickness of 0.2 μm.

[0055] Potassium cyanide 55 g / L, cuprous cyanide 19 g / L, zinc cyanide 7 g / L, potassium hydroxide 1.5 g / L, CTA-604 tin salt 2 g / L, CTA-606 Initial bath starter 90 mL / L, CTA-606 Bri brightener 18 mL / L, CTA-606 Carrier auxiliary agent 6 mL / L, bath pH 12.5, bath temperature 55 °C, cathode current density 1.0 A / dm 2 , cathode moving speed 5 m / min.

[0056] 7. Electrophoretic painting:

[0057] On the zinc alloy die-casting parts plated with gold replacement, the AKINI 120 electrophoretic process developed by Superbond Chemical Industry is used to prepare the electrophoretic clear lacquer coating 7 with a coating thickness of 15 μm.

[0058] AKINI 120 electrophoretic paint 240 g / L, electrophoretic bath pH 4.5, operating temperature 28 °C, bath voltage 30 V, using the plated parts as cathode and titanium plate as anode.

[0059] 8. Drying:

[0060] After electrophoretic painting of zinc alloy die-castings, perform "water washing → pure water washing → drying and curing at 140°C for 20 min". Example 2

[0061] As Figure 1 shown, a coating structure of gold plating and electrophoretic painting includes a zinc alloy die-casting substrate 1, and a copper thiocyanate polymer coating 2, a pyrophosphate copper coating 3, an acid copper coating 4, a bright nickel coating 5, a gold substitute coating 6, and an electrophoretic varnish coating 7 prepared on the zinc alloy die-casting substrate 1 in sequence from inside to outside.

[0062] 1. Pretreatment:

[0063] Perform "chemical dewaxing → water washing → ultrasonic dewaxing → water washing → ultrasonic degreasing → water washing → activation → water washing" on the zinc alloy die-casting substrate 1 according to the current pretreatment process.

[0064] 2. Copper thiocyanate polymer plating:

[0065] Prepare the copper thiocyanate polymer coating 2 on the pretreated zinc alloy die-casting by using the HT-810 copper thiocyanate polymer plating process of Zunyi Huitong, and the coating thickness is 4 μm.

[0066] Copper thiocyanate 22 g / L, 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°C, plating solution pH 12.5, cathode current density 0.8 A / dm 2 , cathode moving speed 5 m / min, anode current density 0.3 A / dm 2 , and use oxygen-free electrolytic copper grains as the anode.

[0067] 3. Pyrophosphate copper plating:

[0068] Prepare the pyrophosphate copper coating 3 on the zinc alloy die-casting after copper thiocyanate polymer plating by using the current pyrophosphate copper plating process, and the coating thickness is 6 μm.

[0069] 4. Acid copper plating:

[0070] Prepare the acid copper coating 4 on the zinc alloy die-casting after pyrophosphate copper plating by using the current acid copper plating process, and the coating thickness is 10 μm.

[0071] 5. Bright nickel plating:

[0072] Prepare the bright nickel coating 5 on the zinc alloy die-casting after acid copper plating by using the current bright nickel plating process, and the coating thickness is 2 μm.

[0073] 6. Gold plating:

[0074] On the zinc alloy die-castings plated with bright nickel, a gold-plated layer 6 is prepared by using the YB-223 bright brass-tin gold plating process of Chaobang Chemical Industry, and the thickness of the gold-plated layer is 0.2 μm.

[0075] Potassium cyanide 75 g / L, cuprous cyanide 24 g / L, zinc cyanide 9 g / L, potassium hydroxide 3.5 g / L, CTA-604 tin salt 3 g / L, CTA-606 Initial bath conditioner 110 mL / L, CTA-606 Bri brightener 18 mL / L, CTA-606 Carrier auxiliary agent 6 mL / L, the pH of the plating solution is 12.5, the plating bath temperature is 55 °C, and the cathode current density is 1.2 A / dm 2 , and the cathode moves at 5 m / min.

[0076] 7. Electrophoretic painting:

[0077] On the zinc alloy die-castings plated with gold, an electrophoretic clear lacquer coating 7 is prepared by using the AKINI 120 electrophoretic process developed by Chaobang Chemical Industry, and the thickness of the coating is 15 μm.

[0078] AKINI 120 electrophoretic paint 340 g / L, the pH of the electrophoretic bath solution is 4.5, the operating temperature is 28 °C, the bath voltage is 30 V, the plated parts are used as the cathode, and the titanium plate is used as the anode.

[0079] 8. Drying:

[0080] After electrophoretic painting of the zinc alloy die-castings, it is subjected to "water washing → pure water washing → drying and curing at 140 °C for 20 min".

[0081] Test example 1:

[0082] For the gold-plated and electrophoretic paint samples prepared according to Example 1 and Example 2, the adhesion of the coating is tested by the thermal shock method in accordance with GB / T 5270–2005 "Review of test methods for adhesion of metallic coatings on metallic substrates - Electrodeposited and chemically deposited coatings". The plated parts are placed in a heating furnace and heated to 150 °C for 30 min, and then taken out and suddenly cooled in water at room temperature. No blistering or peeling occurs on the coating. The coating structure prepared in this example has good adhesion.

[0083] Test example 2:

[0084] For the gold-plated and electrophoretic paint samples prepared according to Example 1 and Example 2, a neutral salt spray test is carried out for 240 h in accordance with GB / T 10125–2021 "Artificial atmosphere corrosion test - Salt spray test". No rust appears on the surface of the plated parts. This coating structure has high corrosion resistance.

[0085] The above has introduced in detail the technical solutions provided by the embodiments of the present utility model. Specific examples are used herein to elaborate on the principles and implementation manners of the embodiments of the present utility model. The description of the above embodiments is only applicable to helping understand the principles of the embodiments of the present utility model. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, several modifications and improvements can still be made, and these all fall within the protection scope of the present utility model.

Claims

1. A coating structure of gold plating and electrophoretic painting, characterized in that: The invention comprises a zinc alloy die-casting substrate, and a polymerized thiocyanate copper plating layer, an acid copper plating layer, a pyrophosphate copper plating layer, a bright nickel plating layer, a gold plating layer, and an electrophoretic varnish coating which are sequentially prepared from the inside to the outside on the zinc alloy die-casting substrate; The gold-substitute plating layer is a plating layer prepared by using a copper-tin alloy plating process, and the plating layer thickness is 0.1-0.2 μm.

2. The gold-plating and electrophoretic coating structure according to claim 1, characterized in that: The thickness of the polymerized thiocyanate copper plating layer is 3-6 μm.

3. The gold-plated and electrophoretic-painted coating structure according to claim 1, characterized in that: The thickness of the pyrophosphate copper plating layer is 5 to 10 μm.

4. The gold-plating and electrophoretic coating structure according to claim 1, characterized in that: The thickness of the acid copper plating layer is 8 to 16 μm.

5. The gold-plating and electrophoretic coating structure according to claim 1, characterized in that: The thickness of the bright nickel plating layer is 1 to 5 μm.

6. The gold-plating and electrophoretic coating structure according to claim 1, characterized in that: The thickness of the electrophoretic varnish coating is 9 to 18 μm.

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