Decorative palladium plating layer structure for pre-plating copper with polythiocyanate

Abstract

The utility model discloses a decorative palladium plating layer structure with polythiocyanate pre-plated copper, which comprises a zinc alloy substrate, and a polythiocyanate pre-plated copper layer, a pyrophosphate copper plating layer, an acid copper plating layer, a bright nickel plating layer, a high-corrosion-resistance nickel-tin alloy plating layer and a palladium plating layer which are sequentially prepared on the zinc alloy substrate from inside to outside. The utility model discloses a decorative palladium plating layer structure pre-plated with polythiocyanate, which is characterized in that the binding force of a plating layer is measured by a thermal shock test method according to GB / T 5270-2005 Metal Covering Layer Electro-Deposition and Chemical Deposition Layer Adhesive Strength Test Method on Metal Matrix, and the binding force meets the standard requirement; the acetate fog test is carried out for 120 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 particularly relates to a decorative palladium coating structure with pre-plated copper by polymerized thiocyanate. Background Art

[0002] Palladium is a noble metal material with stable chemical properties similar to gold. Palladium coatings have excellent corrosion resistance, wear resistance, and electrical properties. [1] The palladium plating process can prepare a uniform, bright, silver-white palladium coating, which is suitable for surface coatings of decorative products such as jewelry, watches, and glasses.

[0003] According to the traditional process, a pre-plated copper layer is prepared on zinc alloy die-castings by cyanide copper plating process, and then copper pyrophosphate plating, acid copper plating, bright nickel plating, etc. are carried out. Due to the high pollution and high risk of cyanide, its use has been strictly restricted or even prohibited. However, when directly plating copper on the surface of zinc alloy by the current divalent copper cyanide-free copper plating process, the problem of low coating adhesion still needs to be improved. [2]

[0004] The polymerized thiocyanate copper plating process is a newly developed cyanide-free copper plating process. It uses cuprous salt to prepare the plating solution and polymerized sodium thiocyanate as the complexing agent. Its process characteristics and performance are close to the traditional cyanide copper plating. This process is in the development and trial stage, and its process stability needs to be tested by practice.

[0005] According to the traditional process method, palladium is usually plated on a bright nickel plating layer, but the corrosion resistance of the bright nickel plating layer is poor. The palladium-plated parts prepared by this coating structure still cannot reach an ideal use effect.

[0006] The high-corrosion-resistant nickel-tin alloy coating has high corrosion resistance, but its surface is prone to passivation and is generally used as a surface coating.

[0007] References: [1] Wang Lili, Electroplating Palladium Electrolyte [J], Electroplating & Finishing, 2005, 27(1): 46 - 48. [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

[0008] In order to solve the high pollution problem of preparing cyanide pre-plated copper layer on zinc alloy die-castings by traditional methods, the utility model provides a decorative palladium coating structure with pre-plated copper by polymerized thiocyanate. To achieve the above purpose, the utility model adopts the following technical solutions:

[0009] ​A decorative palladium plating structure with polythiocyanate pre-copper plating, comprising a zinc alloy substrate, and a polythiocyanate pre-copper plating layer, a pyrophosphate copper plating layer, an acid copper plating layer, a bright nickel plating layer, a high corrosion resistance nickel-tin alloy plating layer, and a palladium plating layer, which are sequentially prepared from the inside to the outside on the zinc alloy substrate;

[0010] The palladium-plated layer is prepared by a square wave pulse electroplating process, and the thickness of the plating layer is 0.05 to 0.5 μm;

[0011] The thickness of the polymerized thiocyanate pre-plated copper layer is 2-6 μm.

[0012] Preferably, the thickness of the pyrophosphate copper plating is 7 to 12 μm.

[0013] Preferably, the thickness of the acid copper plating layer is 8-18 μm.

[0014] Preferably, the thickness of the bright nickel plating layer is 7-12 μm.

[0015] Preferably, the high corrosion resistance nickel-tin alloy plating layer is 2 to 5 μm;

[0016] There are many pores on the surface of zinc alloy die castings. After the polythiocyanate pre-copper plating, pyrophosphate copper plating is usually required to completely close the pores. Bright nickel plating is applied on the copper layer. The electrode potential of the nickel layer is relatively negative. It is an anodic coating for the copper layer. This coating structure can better block the corrosion of the corrosive medium toward the substrate. The corrosion resistance of the high corrosion resistance nickel-tin alloy coating is significantly higher than that of the bright nickel coating. Pulse electroplating of palladium is used on the high corrosion resistance nickel-tin alloy coating. Good bonding can be formed between the coatings and the service life of the plated parts can be significantly extended.

[0017] Compared with the prior art, the utility model has the following beneficial effects:

[0018] 1. The utility model discloses a decorative palladium plating structure pre-plated with copper using polythiocyanate, which adopts the polythiocyanate copper plating process instead of cyanide copper plating to prepare the pre-plated copper layer, thus overcoming the high pollution and high risk problems caused by the use of cyanide;

[0019] 2. The utility model discloses a decorative palladium coating structure pre-plated with copper using polymerized thiocyanate, which significantly improves the corrosion resistance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 It is a schematic diagram of the coating structure of Example 1 and Example 2 of the utility model. Detailed Embodiments

[0022] The present utility model will be described in detail below in conjunction with the accompanying drawings and specific embodiments. Here, the illustrative embodiments and descriptions of the present utility model are used to explain the present utility model, but not to limit the present utility model.

[0023] On the matrix of the zinc alloy die-casting, a pre-plated copper layer of polymeric thiocyanate, a copper pyrophosphate plating layer, an acid copper plating layer, a bright nickel plating layer, a highly corrosion-resistant nickel-tin alloy plating layer, and a palladium plating layer are prepared in sequence from the inside to the outside.

[0024] The existing pretreatment process is used to dewax, degrease, and activate the matrix of the zinc alloy die-casting.

[0025] Preferably, the thickness of the pre-plated copper layer of polymeric thiocyanate is 2 - 6 μm, and it is prepared by the polymeric thiocyanate copper plating process.

[0026] Preferably, the pre-plated copper layer of polymeric thiocyanate is prepared by the HT-810 polymeric thiocyanate copper plating process of Zunyi Huitong:

[0027] Copper(I) thiocyanate 17 - 23 g / L, 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, bath temperature 45°C - 55°C, bath pH range 12 - 13, cathode current density 0.5 - 1.0 A / dm 2 , cathode movement 4 - 6 m / min, anode current density ≤ 0.5 A / dm 2 , using oxygen-free electrolytic copper angle (or copper grains) as the anode.

[0028] Preferably, the thickness of the copper pyrophosphate plating layer is 7 - 12 μm, and it is prepared by the existing copper pyrophosphate plating process.

[0029] Preferably, the thickness of the acid copper plating layer is 8 - 18 μm, and the acid copper plating layer is prepared by the existing acid copper plating process.

[0030] Preferably, the thickness of the bright nickel plating layer is 7 - 12 μm, and it is prepared by the existing bright nickel plating process.

[0031] Preferably, the thickness of the highly corrosion-resistant nickel-tin alloy plating layer is 2 - 5 μm, and it is prepared by the existing highly corrosion-resistant nickel-tin alloy plating process.

[0032] Preferably, the highly corrosion-resistant nickel-tin alloy plating layer is prepared by the YF-737 highly corrosion-resistant nickel-tin alloy plating process of Chaobang Chemical Industry:

[0033] Nickel chloride: 140 - 180 g / L, YF-737A additive: 450 - 600 mL / L, YF-737B additive: 30 - 60 mL / L, pH value of plating solution: 3.5 - 4.5, plating bath temperature: 65°C - 70°C, cathode current density: 0.5 - 1.5 A / dm 2 , cathode movement: 3 - 5 m / min.

[0034] Preferably, the thickness of the palladium plating layer is 0.05 - 0.5 μm, and it is prepared by the current pulse palladium plating process.

[0035] Preferably, the palladium plating layer is prepared by the Pallatec PD-300 pulse palladium plating process of Superbond Chemical Industry:

[0036] Pallatec PD-300 starter solution: 740 - 760 mL / L, palladium chloride ammonium: 7.5 - 8.5 g / L, pH value of plating solution: 8.5 - 9.5, plating bath temperature: 28°C - 32°C; conduction time of square wave pulse current: 1 - 9 ms, current off time: 1 - 9 ms, peak cathode current density: 1.2 - 2.4 A / dm 2 , average cathode current density: 0.6 - 1.2 A / dm 2 , cathode movement: 4 - 6 m / min, using a platinum metal plate as the anode.

[0037] After the zinc alloy die-casting is palladium-plated and washed clean, it is dried at 70°C - 80°C for 15 - 25 min. Example 1

[0038] As Figure 1 shown, a decorative palladium plating layer structure with pre-plated copper by polymerized thiocyanate includes a zinc alloy substrate 1, and a polymerized thiocyanate pre-plated copper layer 2, a pyrophosphate copper plating layer 3, an acid copper plating layer 4, a bright nickel plating layer 6, a high anti-corrosion nickel-tin alloy plating layer 6, and a palladium plating layer 7 prepared in sequence from inside to outside on the zinc alloy substrate 1.

[0039] 1. Pretreatment:

[0040] The zinc alloy die-casting substrate 1 is subjected to "chemical dewaxing → water washing → ultrasonic dewaxing → water washing → ultrasonic degreasing → water washing → activation → water washing".

[0041] 2. Polymerized thiocyanate pre-plated copper:

[0042] After the pretreatment of the zinc alloy die-casting, the polymerized thiocyanate pre-plated copper layer 2 is prepared by the HT-810 polymerized thiocyanate copper plating process of Zunyi Huitong, and the thickness of the plating layer is 3 μm.

[0043] Copper(I) thiocyanate 18 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 53 °C, bath pH 12.8, cathode current density 0.7 A / dm 2 , cathode movement 5 m / min, anode current density 0.4 A / dm 2 , using oxygen-free electrolytic copper angle as anode.

[0044] 3. Copper pyrophosphate plating:

[0045] After pre-plating copper with polymerized thiocyanate on zinc alloy die-castings, the current copper pyrophosphate plating process is used to prepare the copper pyrophosphate plating layer 3 with a coating thickness of 8 μm.

[0046] 4. Acid copper plating:

[0047] After copper pyrophosphate plating on zinc alloy die-castings, the current acid copper plating process is used to prepare the acid copper plating layer 4 with a coating thickness of 12 μm.

[0048] 5. Bright nickel plating:

[0049] After acid copper plating on zinc alloy die-castings, the current bright nickel plating process is used to prepare the bright nickel plating layer 5 with a coating thickness of 10 μm.

[0050] 6. High corrosion-resistant nickel-tin alloy plating:

[0051] After bright nickel plating on zinc alloy die-castings, the current high corrosion-resistant nickel-tin alloy plating process is used to prepare the high corrosion-resistant nickel-tin alloy plating layer 6 with a coating thickness of 3 μm.

[0052] Nickel chloride 150 g / L, YF-737A additive 500 mL / L, YF-737B additive 400 mL / L, bath pH 4.2, bath temperature 68 °C, cathode current density 1.0 A / dm 2 , cathode movement 4 m / min.

[0053] 7. Palladium plating:

[0054] After high corrosion-resistant nickel-tin alloy plating on zinc alloy die-castings, the Pallatec PD-300 pulse palladium plating process of Superbond Chemical is used to prepare the palladium plating layer 7 with a coating thickness of 0.3 μm.

[0055] Pallatec PD-300 starter solution 740 mL / L, palladium chloride 7.7 g / L, bath pH 9.2, bath temperature 32 °C; square wave pulse current conduction time 6 ms, current off time 6 ms, peak cathode current density 1.6 A / dm 2 , average cathode current density 0.8 A / dm 2, the cathode moves at 5 m / min, and a platinum plate is used as the anode.

[0056] 8. Drying:

[0057] After the zinc alloy die-casting is palladium-plated and washed clean, it is dried at 80 °C for 15 min. Example 2

[0058] As Figure 1 shown, a decorative palladium plating structure with a pre-plated copper layer of polymeric thiocyanate includes a zinc alloy substrate 1, and a polymeric thiocyanate pre-plated copper layer 2, a pyrophosphate copper plating layer 3, an acid copper plating layer 4, a bright nickel plating layer 5, a highly corrosion-resistant nickel-tin alloy plating layer 6, and a palladium plating layer 7 sequentially prepared on the zinc alloy substrate 1 from the inside to the outside.

[0059] 1. Pretreatment:

[0060] The zinc alloy die-casting substrate 1 is subjected to "chemical dewaxing → water washing → ultrasonic dewaxing → water washing → ultrasonic degreasing → water washing → activation → water washing".

[0061] 2. Pre-plating copper with polymeric thiocyanate:

[0062] After the pretreatment of the zinc alloy die-casting, the polymeric thiocyanate pre-plated copper layer 2 is prepared by using the HT-810 polymeric thiocyanate copper plating process of Zunyi Huitong, and the coating thickness is 5 μm.

[0063] Copper thiocyanate polymer 22 g / L, sodium thiocyanate polymer 150 g / L, potassium sodium tartrate 10 g / L, HT-810 brightener 1.5 mL / L, HT-810 leveling agent 3 mL / L, bath temperature 52 °C, bath pH 12.5, cathode current density 0.8 A / dm 2 , the cathode moves at 6 m / min, and the anode current density is 0.3 A / dm 2 , and an oxygen-free electrolytic copper granule is used as the anode.

[0064] 3. Pyrophosphate copper plating:

[0065] After the zinc alloy die-casting is pre-plated with copper by polymeric thiocyanate, the pyrophosphate copper plating layer 3 is prepared by using the current pyrophosphate copper plating process, and the coating thickness is 6 μm.

[0066] 4. Acid copper plating:

[0067] After the zinc alloy die-casting is plated with pyrophosphate copper, the acid copper plating layer 4 is prepared by using the current acid copper plating process, and the coating thickness is 15 μm.

[0068] 5. Bright nickel plating:

[0069] After the zinc alloy die-casting is plated with acid copper, the bright nickel plating layer 5 is prepared by using the current bright nickel plating process, and the coating thickness is 10 μm.

[0070] 6. High-corrosion-resistant nickel-tin alloy plating:

[0071] After zinc alloy die-castings are plated with bright nickel, a high-corrosion-resistant nickel-tin alloy coating 6 is prepared by using the current high-corrosion-resistant nickel-tin alloy plating process, and the coating thickness is 3 μm.

[0072] Nickel chloride 170 g / L, YF-737A additive 550 mL / L, YF-737B additive 50 mL / L, pH value of the plating solution 3.8, plating bath temperature 63 °C, cathode current density 1.2 A / dm 2 , cathode movement 4 m / min.

[0073] 7. Palladium plating:

[0074] After zinc alloy die-castings are plated with high-corrosion-resistant nickel-tin alloy, a palladium plating layer 7 is prepared by using the Pallatec PD-300 pulse palladium plating process of Superbond Chemical Industry, and the coating thickness is 0.3 μm.

[0075] Pallatec PD-300 starting solution 760 mL / L, palladium chloride 8.3 g / L, pH of the plating solution 8.8, plating bath temperature 28 °C - 30 °C; conduction time of square wave pulse current 6 ms, current off-time 6 ms, peak cathode current density 1.6 A / dm 2 , average cathode current density 0.8 A / dm 2 , cathode movement 5 m / min, using a platinum metal plate as the anode.

[0076] 8. Drying:

[0077] After zinc alloy die-castings are plated with palladium and washed clean, they are dried at 70 °C for 25 min.

[0078] Test Example 1:

[0079] For the palladium-plated samples prepared in Example 1 and Example 2 of this embodiment, the adhesion of the coating was measured by the thermal shock test 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 samples were placed in a heating furnace and heated to 150 °C for 30 min, then taken out and suddenly cooled in water at room temperature. No blistering or peeling occurred on the coating, and its adhesion was good.

[0080] Test Example 2:

[0081] For the palladium-plated samples prepared in Example 1 and Example 2 of this embodiment, the acetic acid salt spray test was carried out for 120 h in accordance with GB / T 10125-2021 "Artificial Atmosphere Corrosion Tests - Salt Spray Tests". No corrosion products were formed on the surface of the samples, and the prepared coatings had good corrosion resistance.

[0082] Comparative Example 1:

[0083] The poly thiocyanate pre - copper plating layer, pyrophosphate copper plating layer, acid copper plating layer, bright nickel plating layer, and palladium plating layer were successively prepared on the zinc alloy die - casting from the inside to the outside according to the process of Example 1. Compared with Example 1, the coating structure of Comparative Example 1 does not include the high - corrosion - resistant nickel - tin alloy coating. The palladium - plated sample prepared in Comparative Example 1 was subjected to an acetic acid salt spray test for 80 h according to GB / T 10125 - 2021 "Artificial atmosphere corrosion test - Salt spray test". Grey corrosion products were formed on the surface of the sample. The comparative test shows that plating palladium on the high - corrosion - resistant nickel - tin alloy coating significantly improves the corrosion resistance of the coating.

[0084] The technical solutions provided by the embodiments of the present utility model have been introduced in detail above. Specific examples are used herein to elaborate on the principles and implementation manners of the embodiments of the present utility model. The descriptions of the above embodiments are 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 belong to the protection scope of the present utility model.

Claims

1. A decorative palladium coating structure pre-plated with copper using polythiocyanate, characterized in that: It comprises a zinc alloy substrate, and a polymerized thiocyanate pre-plated copper layer, a pyrophosphate copper plating layer, an acid copper plating layer, a bright nickel plating layer, a high corrosion resistance nickel-tin alloy plating layer, and a palladium plating layer which are sequentially prepared from the inside to the outside on the zinc alloy substrate; The palladium-plated layer is prepared by a square wave pulse electroplating process, and the thickness of the plating layer is 0.05 to 0.5 μm; The thickness of the polymerized thiocyanate pre-plated copper layer is 2-6 μm.

2. The decorative palladium coating structure pre-plated with copper by polythiocyanate as claimed in claim 1, characterized in that: The thickness of the pyrophosphate copper plating is 7-12 μm.

3. The decorative palladium coating structure pre-plated with copper by polythiocyanate as claimed in claim 1, characterized in that: The thickness of the acid copper plating layer is 8-18 μm.

4. The decorative palladium coating structure pre-plated with copper by polythiocyanate as claimed in claim 1, characterized in that: The thickness of the bright nickel plating layer is 7-12 μm.

5. The decorative palladium coating structure pre-plated with copper by polythiocyanate as claimed in claim 1, characterized in that: The thickness of the high corrosion resistance nickel-tin alloy plating layer is 2-5 μm.

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