Plating layer structure plated with cupronickel tin and electrophoretic paint

Abstract

The utility model discloses a plating layer structure plated with cupronickel tin and electrophoretic paint, which comprises a steel substrate, and a polythiocyanate pre-plated copper layer, an acid copper plating layer, a cupronickel tin plating layer and an electrophoretic varnish coating which are sequentially prepared on the steel substrate from inside to outside. According to the plating layer structure plated with the white copper tin and the electrophoretic paint, the binding force of the plating layer is tested by a thermal shock method according to GB / T 5270-2005 Metal Cover Electrodeposition and Chemical Deposition Layer Adhesion Strength Test Method on Metal Substrate, the plating layer does not blister or fall off, and the binding force of the plating layer 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 in particular relates to a coating structure of white copper tin plating and electrophoretic painting. Background Art

[0002] Electroplating high-tin copper-tin alloy is called electroplating white copper tin in the industry. The coating will not cause skin allergic reactions and fully complies with RoHS requirements. Studies have shown that white copper tin can achieve the same performance as electroplated nickel. It has a similar luster to nickel plating and has good corrosion resistance and wear resistance. Many electroplated parts in Western countries have replaced the bright nickel plating process with white copper tin plating. [1] Many domestic electroplating companies are also using white copper tin plating instead of bright nickel plating in electroplating products processed and exported to Europe and the United States.

[0003] The traditional process of plating white copper tin on steel parts is usually to perform cyanide copper plating, pyrophosphate copper plating, acid copper plating, white copper tin plating, and chromate electrolytic protection on the steel substrate in sequence.

[0004] Cyanide copper plating is highly toxic and risky. The industry is actively developing cyanide-free copper plating technology to replace traditional cyanide copper plating. However, the developed divalent copper cyanide-free copper plating technology has encountered a bottleneck problem in improving the plating strength. [2] Therefore, there are still many electroplating plants that use the cyanide copper plating process to pre-plated copper on steel substrates.

[0005] The polythiocyanate copper plating process is a newly developed cyanide-free copper plating process, which uses polycuprous thiocyanate as the main salt and polysodium thiocyanate as the coordination agent. Its process performance is close to that of cyanide copper plating, but it does not have the high toxicity problem of cyanide copper plating. The process is currently in the development and trial stage, and its stability needs to be tested in practice.

[0006] The anti-discoloration ability of the decorative coating made of electroplated copper-nickel tin is not ideal. The traditional method of electrolytic protection of the copper-nickel tin coating with chromate can improve the anti-discoloration ability, but there is a problem of high pollution of hexavalent chromium. In addition, the speed of electroplating copper-nickel tin is slow and not suitable for preparing thicker coatings, while the corrosion resistance of thinner copper-nickel tin coatings is not high enough.

[0007] The utility patent "A plating structure with high corrosion resistance and decorative properties" with the authorization announcement number CN 204982090 U discloses a nickel-tin plating structure, including a base metal substrate, and a bright zinc-nickel alloy plating layer and a high-tin copper-tin alloy plating layer sequentially prepared on the base metal substrate. According to GB / T 10125-2021 "Artificial atmosphere corrosion test salt spray test", a neutral salt spray test was carried out for 24 hours, and no corrosion products were generated on the surface of the plated part. It can be seen that the corrosion resistance of this decorative nickel-tin plating is low.

[0008] References: [1] Guo Chongwu, Electroplating White Copper Tin Process with Acid Zinc Nickel Alloy Plating as the Underlayer [J], Electroplating & Finishing, 2018, 37(12): 536 - 537. [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

[0009] In order to solve the pollution problems of cyanide pre - plating copper on the steel surface and chromate electrolytic protection of the white copper tin coating, the present utility model provides a coating structure of white copper tin plating and electrophoretic painting. To achieve the above - mentioned purpose, the present utility model adopts the following technical solutions:

[0010] A coating structure of white copper tin plating and electrophoretic painting, comprising a steel substrate, and a polymeric thiocyanate pre - copper plating layer, an acid copper plating layer, a white copper tin plating layer, and an electrophoretic varnish coating which are sequentially prepared on the steel substrate from the inside to the outside;

[0011] The thickness of the white copper tin plating layer is 2 - 6 μm.

[0012] Preferably, the thickness of the polymeric thiocyanate pre - copper plating layer is 1 - 4 μm.

[0013] Preferably, the thickness of the acid copper plating layer is 10 - 20 μm.

[0014] Preferably, the thickness of the electrophoretic varnish coating is 10 - 18 μm.

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

[0016] 1. The coating structure of white copper tin plating and electrophoretic painting disclosed by the present utility model overcomes the high - pollution problem of pre - plating copper on the steel substrate by using the cyanide copper plating process;

[0017] 2. The coating structure of white copper tin plating and electrophoretic painting disclosed by the present utility model overcomes the high - pollution problem of traditional chromate electrolytic protection. 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 It 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 accompanying drawings and specific embodiments. The illustrative embodiments and descriptions herein are used to explain the present utility model, but not to limit the present utility model.

[0021] A plating structure of white copper-tin plating and electrophoretic painting, comprising a steel substrate, and a pre-plated copper layer of polymeric thiocyanate, an acid copper plating layer, a white copper-tin plating layer, and an electrophoretic varnish coating sequentially prepared on the steel substrate from inside to outside.

[0022] The steel part substrate is degreased, derusted, and activated by using the current pretreatment process.

[0023] The pre-plated copper layer of polymeric thiocyanate is prepared on the pretreated steel part by using the polymeric thiocyanate copper plating process.

[0024] Preferably, the thickness of the pre-plated copper layer of polymeric thiocyanate is 1-4 μm.

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

[0026] Cuprous 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, plating bath temperature 45 °C - 55 °C, plating solution pH value 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 granule) as the anode.

[0027] The acid copper plating layer is prepared on the steel part plated with polymeric thiocyanate by using the current acid copper plating process.

[0028] Preferably, the thickness of the acid copper plating layer is 10-20 μm.

[0029] The white copper-tin plating layer is prepared on the steel part plated with acid copper by using the current white copper-tin plating process.

[0030] Preferably, the thickness of the white copper-tin plating layer is 2-6 μm.

[0031] Preferably, the white copper-tin plating layer is prepared by using the ASELY CTA-535 white copper-tin plating process of Chaobang Chemical Industry:

[0032] Potassium cyanide 60 - 95 g / L, cuprous cyanide 12 - 20 g / L, potassium hydroxide 5 - 20 g / L, ASELY CTA-604 white copper-tin tin salt 50 - 65 g / L, ASELY CTA-602 zinc supplement 12 - 25 mL / L, ASELY CTA-535 Initial white copper-tin plating bath starter 20 - 50 mL / L, ASELY CTA-535 Bri white copper-tin brightener 2 - 6 mL / L, ASELY CTA-535 WA white copper-tin wetting agent 0.5 - 5 mL / L, pH value of plating solution 12.5 - 13.5, plating bath temperature 45 °C - 55 °C, cathode current density 1.5 - 2.5 A / dm 2 , cathode movement 4 - 6 m / min.

[0033] Prepare an electrophoretic varnish coating on the steel parts plated with white copper-tin.

[0034] Preferably, the thickness of the electrophoretic varnish coating is 10 - 18 μm.

[0035] Preferably, the electrophoretic varnish coating is prepared by the AKINI 120 electrophoretic process of Superbond Chemical Industry:

[0036] AKINI 120 electrophoretic paint 300 - 350 g / L, pH value of electrophoretic bath solution 4 - 5, operating temperature 25 °C - 30 °C, bath voltage 30 - 50 V, using the plated parts as the cathode and titanium plates as the anodes, and the coating is dried and cured at 120 °C - 140 °C for 20 - 30 min. Example 1

[0037] As Figure 1 shown, a coating structure of plating white copper-tin and electrophoretic painting includes a steel substrate 1, and a pre-plated copper layer 2 of polymeric thiocyanate, a copper sulfate plating layer 3, a white copper-tin plating layer 4, and an electrophoretic varnish coating 5 prepared in sequence from the inside to the outside on the steel substrate 1.

[0038] 1. Pretreatment:

[0039] Perform "alkaline chemical degreasing → water washing → pickling → water washing → alkaline cathodic electro-degreasing → water washing → alkaline anodic electro-degreasing → water washing → activation → water washing" on the steel part substrate 1 according to the current pretreatment process.

[0040] 2. Plating copper with polymeric thiocyanate:

[0041] Prepare a pre-plated copper layer 2 of polymeric thiocyanate on the pretreated steel parts by using the HT-810 polymeric thiocyanate copper plating process of Zunyi Huitong, and the coating thickness is 2 μm.

[0042] 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.

[0043] 3. Acid copper plating:

[0044] On the steel parts that have been plated with copper thiocyanate, the current acid copper plating process is used to prepare the acid copper coating 3, and the coating thickness is 15 μm.

[0045] 4. White copper tin plating:

[0046] On the steel parts that have been plated with acid copper, the ASELY CTA-535 white copper tin plating process of Superbond Chemical Industry is used to prepare the white copper tin coating 4, and the coating thickness is 4 μm.

[0047] Potassium cyanide 65 g / L, cuprous cyanide 15 g / L, potassium hydroxide 10 g / L, ASELY CTA-604 white copper tin tin salt 55 g / L, ASELY CTA-602 zinc supplement 15 mL / L, ASELY CTA-535 Initial white copper tin starter 30 mL / L, ASELY CTA-535 Bri white copper tin brightener 4 mL / L, ASELY CTA-535 WA white copper tin wetting agent 3 mL / L, bath pH 13, bath temperature 52 °C, cathode current density 1.8 A / dm 2 , cathode moving speed 5 m / min.

[0048] 5. Electrophoretic painting:

[0049] On the steel parts that have been plated with white copper tin, the AKINI 120 electrophoretic process of Superbond Chemical Industry is used to prepare the electrophoretic clear lacquer coating 5, and the coating thickness is 13 μm.

[0050] 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 the cathode and titanium plates as the anode.

[0051] 6. Drying:

[0052] After electrophoretic painting of the steel parts, "water washing → pure water washing → drying and curing at 140 °C for 20 min" is carried out. Example 2

[0053] As Figure 1As shown in the figure, a coating structure of white copper-tin plating and electrophoretic painting includes a steel substrate 1, and a polymeric thiocyanate pre-copper layer 2, an acid copper coating 3, a white copper-tin coating 4, and an electrophoretic varnish coating 5 that are sequentially prepared on the steel substrate 1 from the inside to the outside.

[0054] 1. Pretreatment:

[0055] Perform "alkaline chemical degreasing → water washing → pickling → water washing → alkaline cathodic electro-degreasing → water washing → alkaline anodic electro-degreasing → water washing → activation → water washing" on the steel substrate 1 of the steel parts according to the current pretreatment process.

[0056] 2. Polymeric thiocyanate copper plating:

[0057] Prepare the polymeric thiocyanate pre-copper layer 2 on the pretreated steel parts by using the HT-810 polymeric thiocyanate copper plating process of Zunyi Huitong, and the coating thickness is 3 μm.

[0058] 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, bath temperature 53 °C, bath pH 12.5, cathodic current density 0.8 A / dm 2 , cathode moving speed 5 m / min, anodic current density 0.3 A / dm 2 , and use oxygen-free electrolytic copper grains as the anode.

[0059] 3. Acid copper plating:

[0060] Prepare the acid copper coating 3 on the steel parts after polymeric thiocyanate copper plating by using the current acid copper plating process, and the coating thickness is 13 μm.

[0061] 4. White copper-tin plating:

[0062] Prepare the white copper-tin coating 4 on the steel parts after acid copper plating by using the ASELY CTA-535 white copper-tin plating process of Chaobang Chemical Industry, and the coating thickness is 4 μm.

[0063] Potassium cyanide 90 g / L, cuprous cyanide 18 g / L, potassium hydroxide 15 g / L, ASELY CTA-604 white copper-tin tin salt 60 g / L, ASELY CTA-602 zinc supplement 20 mL / L, ASELY CTA-535 Initial white copper-tin starter 40 mL / L, ASELY CTA-535 Bri white copper-tin brightener 4 mL / L, ASELY CTA-535 WA white copper-tin wetting agent 3 mL / L, bath pH 13, bath temperature 48 °C, cathodic current density 2.2 A / dm 2 , cathode moving speed 5 m / min.

[0064] 5. Electrophoretic painting:

[0065] On the steel parts plated with white copper tin, an electrophoretic clear lacquer coating 5 is prepared by using the AKINI 120 electrophoretic process developed by Chaobang Chemical Industry, and the coating thickness is 15 μm.

[0066] The AKINI 120 electrophoretic paint is 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.

[0067] 6. Drying:

[0068] After the steel parts are electrophoretically painted, they are subjected to "water washing → pure water washing → drying and curing at 130 °C for 25 min".

[0069] Test Example 1:

[0070] Steel parts plated with white copper tin and painted with electrophoretic paint samples are prepared according to Example 1 and Example 2. According to GB / T 5270–2005 "Review of Test Methods for Adhesion of Metallic Coatings on Metallic Substrates - Electrodeposited and Chemically Deposited Coatings", the adhesion of the coating is tested by the thermal shock method. The samples are placed in a heating furnace and heated to 200 °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 test shows that the coating structure prepared in this example has good adhesion.

[0071] Test Example 2:

[0072] Steel parts plated with white copper tin and painted with electrophoretic paint samples are prepared according to Example 1 and Example 2. According to GB / T 10125–2021 "Artificial Atmosphere Corrosion Tests - Salt Spray Tests", a neutral salt spray test is carried out for 240 h, and no rust appears on the surface of the plated parts.

[0073] The technical solutions provided by the embodiments of the present utility model have been introduced in detail above. Specific examples are used in this article 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 help 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 deformations and improvements can still be made, and these all belong to the protection scope of the present utility model.

Claims

1. A coating structure of white copper tin plating and electrophoretic painting, characterized in that: The invention comprises a steel substrate, and a polymerized thiocyanate pre-plated copper layer, an acid copper plating layer, a white copper tin plating layer, and an electrophoretic varnish coating layer which are sequentially prepared from the inside to the outside on the steel substrate; The thickness of the nickel silver tin plating layer is 2-6 μm.

2. The coating structure of white copper tin plating and electrophoretic painting as claimed in claim 1, characterized in that: The thickness of the polymerized thiocyanate pre-plated copper layer is 1-4 μm.

3. The coating structure of white copper tin plating and electrophoretic painting as claimed in claim 1, characterized in that: The thickness of the acid copper plating layer is 10-20 μm.

4. The coating structure of white copper tin plating and electrophoretic painting as claimed in claim 1, characterized in that: The thickness of the electrophoretic varnish coating is 10 to 18 μm.

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