Plating layer structure of trivalent chromium plating

Abstract

The utility model discloses a plating structure of trivalent chromium plating, which comprises a steel substrate, and a polythiocyanate pre-plating copper layer, an acid copper plating layer, a cupronickel tin plating layer, a trivalent chromium plating layer and a nano polymer protective film which are sequentially prepared on the steel substrate from inside to outside. According to GB / T 5270-2005 Metal Covering Layer Electro-Deposition and Chemical Deposition Layer Adhesive Strength Test Method Assessment on Metal Matrix, the binding force of the plating layer is tested by a thermal shock method, and the binding force meets the standard requirement; according to GB / T 10125-2021 Artificial Atmosphere Corrosion Test Salt Spray Test for 72 h, no corrosives are generated on the surface of a plated part, and the prepared plating 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 trivalent chromium plating layer structure. Background Art

[0002] Trivalent chromium plating of steel parts is mainly used in hardware products and other industries. The plated parts have an elegant and beautiful appearance and low preparation cost, and are deeply favored by users.

[0003] Traditionally, trivalent chromium plating over bright nickel can achieve a flawless appearance. However, white people have skin allergies to nickel, and the EU has enacted the RoHS directive, which prohibits nickel from being present in certain electroplated layers.

[0004] Electroplating high tin copper-tin alloy is known as electroplating white copper tin in the industry. It does not cause skin allergic reactions and complies with RoHS requirements. The white copper tin coating has a luster similar to bright nickel plating and has good corrosion resistance and wear resistance. Western countries have replaced bright nickel plating with white copper tin in the electroplating of some products. [1] Many domestic electroplating companies are also following this electroplating process.

[0005] According to the traditional process, steel parts are prepared with a cyanide copper plating process to prepare a pre-copper layer, and then other plating layers are prepared. Due to the high pollution problem of cyanide, the industry is actively developing a new cyanide-free copper plating process that can replace cyanide copper plating. [2] Polythiocyanate copper plating is a newly developed cyanide-free copper plating process in the industry. Its performance is close to that of cyanide copper plating and is currently in the development and trial stage.

[0006] References: [1]. Guo Chongwu, Electroplating process of white copper tin with acid zinc nickel alloy as the base layer [J], Electroplating and Finishing, 2018, 37(12): 536-537. [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. Utility Model Content

[0007] In order to overcome the defect of nickel plating causing skin allergies, the utility model provides a trivalent chromium plating structure. In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0008] A trivalent chromium plating structure comprises a steel substrate, and a polymeric thiocyanate pre-copper plating layer, an acid copper plating layer, a white copper tin plating layer, a trivalent chromium plating layer, and a nano polymer protective film, which are sequentially prepared on the steel substrate from the inside out.

[0009] Preferably, the thickness of the polythiocyanate pre-copper plating layer is 1 to 5 μm.

[0010] Preferably, the thickness of the acid copper plating layer is 12 to 25 μm.

[0011] Preferably, the thickness of the white copper tin plating layer is 3 to 8 μm.

[0012] Preferably, the thickness of the trivalent chromium plating layer is 0.2 to 0.5 μm.

[0013] A pre-copper layer is deposited on steel surfaces using a polythiocyanate copper plating process, creating excellent adhesion between the coating and the substrate. Acid copper plating enhances the surface brightness and corrosion resistance of the plated component. A cupronickel-tin layer is plated on top of the acid copper layer. The electrode potential of the cupronickel-tin layer is significantly negative compared to that of the copper layer, providing electrochemical protection for the copper layer. This coating structure effectively blocks corrosive media from attacking the substrate. Trivalent chromium plating on the cupronickel-tin layer creates excellent adhesion between the layers.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The trivalent chromium plating structure disclosed in this utility model adopts the white copper tin electroplating process instead of the bright nickel plating process, thus overcoming the skin allergy problem caused by the nickel plating layer;

[0016] 2. The trivalent chromium plating structure disclosed in the utility model adopts an electrolytic protection process to prepare a nano-polymer protective film on the trivalent chromium plating layer, which is non-toxic and harmless, and the process is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute an improper limitation of the present invention. In the drawings:

[0018] Figure 1 It is a schematic diagram of the coating structure of Example 1 and Example 2 of the present utility model. DETAILED DESCRIPTION

[0019] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The schematic embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0020] A trivalent chromium plating structure comprises a steel substrate, and a polymeric thiocyanate pre-copper plating layer, an acid copper plating layer, a white copper tin plating layer, a trivalent chromium plating layer, and a nano polymer protective film, which are sequentially prepared on the steel substrate from the inside out.

[0021] The steel substrate is degreased, derusted, and activated according to the current pre-treatment process.

[0022] After pretreatment of steel parts, a polythiocyanate copper plating process is adopted to prepare a polythiocyanate pre-plated copper layer.

[0023] Preferably, the thickness of the polythiocyanate pre-copper plating layer is 1 to 5 μm.

[0024] Preferably, the polythiocyanate pre-copper plating layer is prepared using Zunyi Huitong's HT-810 polythiocyanate copper plating process:

[0025] Polycuprous thiocyanate 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 moving agent 2-4 mL / L, plating tank temperature 45°C-55°C, plating solution pH 12-13, cathode current density 0.5-1.0 A / dm 2 , cathode movement 4~6m / min, anode current density ≤0.5A / dm 2 , use oxygen-free electrolytic copper corners (or copper particles) as anodes.

[0026] After the steel parts are plated with polymerized thiocyanate copper, the acid copper coating is prepared using the current acid copper plating process.

[0027] Preferably, the thickness of the acid copper plating layer is 12 to 25 μm.

[0028] After the steel parts are plated with acid copper, the white copper tin plating layer is prepared by the current white copper tin plating process.

[0029] Preferably, the thickness of the white copper tin plating layer is 3 to 8 μm.

[0030] Preferably, the white copper tin coating is prepared using the ASELY CTA-535 white copper tin coating process of Chaobang Chemical:

[0031] Potassium cyanide 60-95g / L, cuprous cyanide 12-20g / L, potassium hydroxide 5-20g / L, ASELY CTA-604 cupro-nickel tin salt 50-65g / L, ASELY CTA-602 zinc supplement 12-25mL / L, ASELY CTA-535 Initial cupro-nickel tin opener 20-50mL / L, ASELY CTA-535 Bri cupro-nickel tin brightener 2-6mL / L, ASELY CTA-535 WA cupro-nickel tin wetting agent 0.5-5mL / L, plating solution pH 12.5-13.5, plating tank temperature 45℃-55℃, cathode current density 1.5-2.5A / dm 2 , the cathode moves 4 to 6 m / min.

[0032] After the steel parts are plated with white copper tin, the trivalent chromium coating is prepared using the current trivalent chromium plating process.

[0033] Preferably, the thickness of the trivalent chromium plating layer is 0.2 to 0.5 μm.

[0034] Preferably, the trivalent chromium plating layer is prepared using Chaobang Chemical's Trich-6561 chloride trivalent chromium plating process:

[0035] Trich-6561 pre-treatment salt 400-450 g / L, Trich-6563 complexing agent 65-85 mL / L, Trich-6564 stabilizer 1-2 mL / L, Trich-6565 wetting agent 1-3 mL / L, wherein the mass concentration of trivalent chromium is 23-25 ​​g / L, the mass concentration of boric acid is 55-60 g / L, the pH value of the plating solution is 2.5-3.0, the plating tank temperature is 25-36 ° C, and the cathode current density is 8-16 A / dm 2 , medium air agitation.

[0036] After trivalent chromium plating on steel parts, a nano-polymer protective film is prepared using an electrolytic protection process.

[0037] Preferably, the nano-polymer protective film is prepared using the PROTEZVY 1126 electrolytic protection process of Chaobang Chemical:

[0038] PROTEZVY 1126 MUP opener 30-40 mL / L, PROTEZVY 1126 ADDITIVE C 70-90 mL / L, sodium hydroxide 0.15-0.25 g / L, bath pH 3.4-4.0, operating temperature 55-65°C, cathode current density 0.05-0.1 A / dm 2 , electrolysis time 3 to 10 minutes.

[0039] The steel parts are electrolytically protected with nano-polymers and then washed and dried. Example 1

[0040] like Figure 1 As shown, a trivalent chromium plating structure includes a steel substrate 1, and a polymer thiocyanate pre-copper plating layer 2, an acid copper plating layer 3, a white copper tin plating layer 4, a trivalent chromium plating layer 5, and a nano-polymer protective film 6 prepared on the steel substrate 1 from the inside to the outside.

[0041] 1. Pre-treatment:

[0042] The steel substrate 1 is subjected to "alkaline chemical degreasing → water washing → rust removal → water washing → alkaline cathodic electrolytic degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → activation → water washing".

[0043] 2. Polythiocyanate copper plating:

[0044] After pretreatment of the steel parts, the polythiocyanate pre-plated copper layer 2 was prepared using the HT-810 polythiocyanate copper plating process of Zunyi Huitong, and the coating thickness was 2 μm.

[0045] Polycuprous thiocyanate 18g / L, sodium polythiocyanate 120g / L, potassium sodium tartrate 10g / L, HT-810 brightener 1.5mL / L, HT-810 moving agent 3mL / L, plating tank temperature 53℃, plating solution pH 12.8, cathode current density 0.7A / dm 2 , cathode movement 5m / min, anode current density 0.4A / dm 2 , use oxygen-free electrolytic copper corner as the anode.

[0046] 3. Acid copper plating:

[0047] After the steel parts are plated with polymerized thiocyanate copper, an acid copper plating layer 3 is prepared using the current acid copper plating process, and the coating thickness is 15 μm.

[0048] 4. White copper tin plating:

[0049] After the steel parts were plated with acid copper, a cupronickel tin coating 4 was prepared using the ASELY CTA-535 cupronickel tin coating process of Chaobang Chemical. The coating thickness was 6 μm.

[0050] Potassium cyanide 75g / L, cuprous cyanide 15g / L, potassium hydroxide 12g / L, ASELY CTA-604 cupro-tin salt 55g / L, ASELY CTA-602 zinc supplement 16mL / L, ASELY CTA-535 Initial cupro-tin opener 35mL / L, ASELY CTA-535 Bri cupro-tin brightener 4mL / L, ASELY CTA-535 WA cupro-tin wetting agent 3mL / L, plating solution pH 12, plating tank temperature 50℃, cathode current density 1.9A / dm 2 , cathode moves 5m / min.

[0051] 5. Trivalent chromium plating:

[0052] After the steel parts are plated with white copper tin, a trivalent chromium plating layer 5 is prepared using the Trich-6561 chloride trivalent chromium plating process of Chaobang Chemical, and the plating thickness is 0.5 μm.

[0053] Trich-6561 pre-treatment salt 410g / L, Trich-6563 complexing agent 70mL / L, Trich-6564 stabilizer 1.5mL / L, Trich-6565 wetting agent 2mL / L, the mass concentration of trivalent chromium is 23.5g / L, the mass concentration of boric acid is 56g / L, the plating solution pH is 2.8, the plating tank temperature is 30℃, and the cathode current density is 14A / dm 2, medium air agitation.

[0054] 6. Electrolytic protection:

[0055] After trivalent chromium plating, the steel parts are electrolytically protected with a nano-polymer protective film 6 using the PROTEZVY 1126 electrolytic protection process of Chaobang Chemical.

[0056] PROTEZVY 1126 MUP opener 30 mL / L, PROTEZVY 1126 ADDITIVE C 70 mL / L, sodium hydroxide 0.20 g / L, bath pH 3.6, operating temperature 60°C, cathode current density 0.08 A / dm 2 , electrolysis time 8min.

[0057] 7. Drying:

[0058] After electrolytic protection, the steel parts are subjected to "water washing → pure water washing → drying". Example 2

[0059] like Figure 1 As shown, a trivalent chromium plating structure includes a steel substrate 1, and a polymer thiocyanate pre-copper plating layer 2, an acid copper plating layer 3, a white copper tin plating layer 4, a trivalent chromium plating layer 5, and a nano-polymer protective film 6 prepared on the steel substrate 1 from the inside to the outside.

[0060] 1. Pre-treatment:

[0061] The steel substrate 1 is subjected to "alkaline chemical degreasing → water washing → rust removal → water washing → alkaline cathodic electrolytic degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → activation → water washing".

[0062] 2. Polythiocyanate copper plating:

[0063] After pretreatment of the steel parts, the HT-810 polythiocyanate copper plating process of Zunyi Huitong was used to prepare a polythiocyanate pre-plated copper layer 2, with a coating thickness of 3 μm.

[0064] Polythiocyanate cuprous acid 22g / L, polythiocyanate sodium 150g / L, potassium sodium tartrate 10g / L, HT-810 brightener 1.5mL / L, HT-810 moving agent 3mL / L, plating tank temperature 52℃, plating solution pH 12.8, cathode current density 0.8A / dm 2 , cathode movement 5m / min, anode current density 0.3A / dm 2 , using oxygen-free electrolytic copper particles as anode.

[0065] 3. Acid copper plating:

[0066] After the steel parts are plated with polymerized thiocyanate copper, an acid copper plating layer 3 is prepared using the current acid copper plating process, and the coating thickness is 14 μm.

[0067] 4. White copper tin plating:

[0068] After the steel parts were plated with acid copper, a cupronickel tin coating 4 was prepared using the ASELY CTA-535 cupronickel tin coating process of Chaobang Chemical. The coating thickness was 6 μm.

[0069] Potassium cyanide 80g / L, cuprous cyanide 17g / L, potassium hydroxide 12g / L, ASELY CTA-604 cupro-tin salt 60g / L, ASELY CTA-602 zinc supplement 19mL / L, ASELY CTA-535 Initial cupro-tin opener 35mL / L, ASELY CTA-535 Bri cupro-tin brightener 4mL / L, ASELY CTA-535 WA cupro-tin wetting agent 3mL / L, bath pH 12, bath temperature 50°C, cathode current density 2.2A / dm 2 , cathode moves 5m / min.

[0070] 5. Trivalent chromium plating:

[0071] After the steel parts are plated with white copper tin, a trivalent chromium plating layer 5 is prepared using the Trich-6561 chloride trivalent chromium plating process of Chaobang Chemical, and the plating thickness is 0.5 μm.

[0072] Trich-6561 pre-treatment salt 440g / L, Trich-6563 complexing agent 80mL / L, Trich-6564 stabilizer 1.5mL / L, Trich-6565 wetting agent 2mL / L, the mass concentration of trivalent chromium is 24.5g / L, the mass concentration of boric acid is 60g / L, the plating solution pH is 2.7, the plating tank temperature is 28℃, and the cathode current density is 14A / dm 2 , medium air agitation.

[0073] 6. Electrolytic protection:

[0074] After trivalent chromium plating, the steel parts are electrolytically protected with a nano-polymer protective film 6 using the PROTEZVY 1126 electrolytic protection process of Chaobang Chemical.

[0075] PROTEZVY 1126 MUP opener 40 mL / L, PROTEZVY 1126 ADDITIVE C 90 mL / L, sodium hydroxide 0.25 g / L, bath pH 3.8, operating temperature 55°C, cathode current density 0.08 A / dm 2 , electrolysis time 6min.

[0076] 7. Drying:

[0077] After electrolytic protection, the steel parts are subjected to "water washing → pure water washing → drying".

[0078] Test Example 1:

[0079] The trivalent chromium-plated samples prepared in Example 1 and Example 2 were subjected to an acetic acid salt spray test for 72 hours in accordance with GB / T 10125-2021 "Artificial atmosphere corrosion test salt spray test". The surface of the plated parts was free of rust, which exceeded the requirements of GB / T 9797-2016 "Metallic coating nickel + chromium and copper + nickel + chromium electroplating layer" standard.

[0080] Test Example 2:

[0081] The trivalent chromium-plated samples prepared in Examples 1 and 2 were tested for adhesion strength using the thermal shock method in accordance with 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 300°C in a furnace for 30 minutes, then removed and quenched in room temperature water. No blistering or shedding of the coating occurred, indicating that the prepared coating structure had good adhesion.

[0082] The technical solutions provided by the embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only intended to help understand the principles of the embodiments of the present invention. It should be noted that those skilled in the art may make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements fall within the scope of protection of the present invention.

Claims

1. A trivalent chromium plating structure, characterized in that: The invention comprises a steel substrate, and a polymer thiocyanate pre-plated copper layer, an acid copper plating layer, a white copper tin plating layer, a trivalent chromium plating layer, and a nano polymer protective film which are sequentially prepared on the steel substrate from the inside to the outside.

2. The trivalent chromium plating structure according to claim 1, wherein: The thickness of the polymerized thiocyanate pre-plated copper layer is 1 to 5 μm.

3. The trivalent chromium plating structure according to claim 1, wherein: The thickness of the acid copper plating layer is 12 to 25 μm.

4. The trivalent chromium plating structure according to claim 1, wherein: The thickness of the white copper tin plating layer is 3 to 8 μm.

5. The trivalent chromium plating structure according to claim 1, wherein: The thickness of the trivalent chromium plating layer is 0.2-0.5 μm.

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