Cyanide-free cadmium plating and chromium-free passivation coating structure

Abstract

The utility model discloses a cyanide-free cadmium plating and chromium-free passivation coating structure which comprises a stainless steel substrate, and an impact nickel coating, a cyanide-free cadmium plating layer and a chromium-free passivation layer which are sequentially prepared on the stainless steel substrate from inside to outside. According to GB / T 5270-2005 Metal Covering Layer Electro-Deposition and Chemical Deposition Layer Adhesion Strength Test Method on Metal Matrix, the binding force of a plating layer is tested by a thermal shock method, the binding force meets the standard requirement, an acetate fog test is carried out for 450 h according to GB / T 10125-2021 Artificial Atmosphere Corrosion Test Salt Spray Test, no corrosives are generated on the surface of a plating piece, and the plating piece has good corrosion resistance. And the prepared plating 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 of cyanide-free cadmium plating and chromium-free passivation. Background Art

[0002] The protective layer of aerospace stainless steel parts is usually prepared by the process methods of cadmium plating and hexavalent chromium passivation, which significantly improves the corrosion resistance and service life of stainless steel parts.

[0003] Hexavalent chromium passivation has the problem of high pollution. How to solve the high pollution problem of hexavalent chromium has been a hot issue studied by the industry for many years. Trivalent chromium passivation has basically replaced hexavalent chromium passivation in civilian product electroplating, but the trivalent chromium passivation film does not have self-repairing property and cannot meet the technical requirements of the aerospace field.

[0004] The passivation layer prepared by the solvent-based silane chromium-free passivating agent has high corrosion resistance and self-repairing property [1] , and has similar characteristics to the hexavalent chromium passivation film. The application of solvent-based silane chromium-free passivation in the production of zinc plating and zinc-nickel alloy plating has achieved good environmental and social benefits.

[0005] The passivation layer prepared by the water-based silane chromium-free passivating agent lacks self-repairing property and currently cannot meet the special requirements of aerospace parts.

[0006] Reference: [1], Lai Huanwen, Guo Chongwu, High-performance chromium-free passivation technology [J], Electroplating & Pollution Control, 2012, 32(6): 35-37. Content of the Utility Model

[0007] In order to overcome the high pollution problem of hexavalent chromium passivation, the utility model provides a coating structure of cyanide-free cadmium plating and chromium-free passivation. In order to achieve the above purpose, the utility model adopts the following technical scheme:

[0008] A coating structure of cyanide-free cadmium plating and chromium-free passivation, comprising a stainless steel substrate, and an impact nickel coating, a cyanide-free cadmium plating layer, and a chromium-free passivation layer sequentially prepared on the stainless steel substrate from inside to outside;

[0009] The chromium-free passivation layer is a passivation layer prepared by a solvent-based silane chromium-free passivating agent.

[0010] Preferably, the thickness of the chromium-free passivation layer is 0.8-1.0 μm.

[0011] Preferably, the thickness of the cyanide-free cadmium plating layer is 6-15 μm.

[0012] The utility model plates impact nickel on the stainless steel substrate, and a good bonding force can be formed between the coating and the substrate.

[0013] Compared with the prior art, the utility model has the following beneficial effects:

[0014] 1. For the coating structure of cyanide-free cadmium plating and chromium-free passivation disclosed by the utility model, a solvent-based silane chromium-free passivating agent is used to prepare a passivation layer on the cadmium plating layer, overcoming the high pollution problem existing in traditional hexavalent chromium passivation;

[0015] 2. For the coating structure of cyanide-free cadmium plating and chromium-free passivation disclosed by the utility model, the passivation layer prepared by using a solvent-based silane chromium-free passivating agent on the cadmium plating layer has self-repairing property, meeting the special requirements of the aerospace field. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the utility model, constitute a part of this application, and do not constitute an improper limitation to the utility model. In the drawings:

[0017] Figure 1 is a schematic diagram of the coating structure of Embodiment 1 and Embodiment 2 of the utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The following will detail the utility model in conjunction with the drawings and specific embodiments. Here, the schematic embodiments and descriptions of the utility model are used to explain the utility model, but not to limit the utility model.

[0019] A coating structure of cyanide-free cadmium plating and chromium-free passivation, and its preparation process includes sequentially preparing an impact nickel coating, a cyanide-free cadmium plating layer, and a chromium-free passivation layer from the inside to the outside on a stainless steel substrate.

[0020] Degrease, anodically electrolytically activate, and cathodically electrolytically activate the stainless steel part substrate according to the current pretreatment process.

[0021] Preferably, the anodic electrolytic activation adopts the following electrolytic activation process:

[0022] Sulfuric acid 100 - 200 g / L, operating at room temperature, anodic current density 0.5 - 1.5 A / dm 2 , electrolysis time 30 - 60 s.

[0023] Preferably, the cathodic electrolytic activation adopts the following electrolytic activation process:

[0024] Sulfuric acid 100 - 200 g / L, operating at room temperature, cathodic current density 1 - 2 A / dm 2 , electrolysis time 30 - 60 s.

[0025] The impact nickel coating is prepared by using the current impact nickel plating process. Preferably, the impact nickel coating is prepared by the following process:

[0026] Nickel chloride hexahydrate 80 - 120 g / L, hydrochloric acid 80 - 120 g / L, operating at room temperature, cathode current density 2 - 6 A / dm 2 , plating time 2 - 6 min.

[0027] The cyanide-free cadmium plating layer is prepared by the current cyanide-free cadmium plating process. Preferably, the thickness of the cyanide-free cadmium plating layer is 6 - 15 μm.

[0028] Preferably, the cyanide-free cadmium plating layer is prepared by the PULIZIER NCC-617 potassium chloride cyanide-free cadmium plating process of Superbond Chemical Industry:

[0029] Cadmium chloride 25 - 35 g / L, potassium chloride 100 - 140 g / L, PULIZIER NCC-617 complexing agent 100 - 140 g / L, PULIZIER NCC-617 brightening agent 1 - 2 mL / L, PULIZIER NCC-617 auxiliary agent 25 - 30 mL / L, PULIZIER NCC-617 high area brightening agent 5 - 10 mL / L, pH value of the plating solution 7 - 9, working temperature 20 - 35 °C, cathode current density 0.5 - 1.5 A / dm 2 , cathode moving speed 2 - 4 m / min.

[0030] The chromium-free passivation layer is prepared by the current solvent-based silane chromium-free passivating agent. Preferably, the thickness of the chromium-free passivation layer is 0.8 - 1.0 μm.

[0031] Preferably, the chromium-free passivation layer is prepared by the zinccote PRODICO Z-Caot 888 FL chromium-free passivating agent of Superbond Chemical Industry:

[0032] Zinccote PRODICO Z-Caot 888 FL is solvent-based, used as the original solution, operating at room temperature, passivation time 30 - 90 s.

[0033] Preferably, the chromium-free passivation layer is prepared by the zinccote ZECCOAT-825 chromium-free passivating agent of Superbond Chemical Industry:

[0034] Zinccote ZECCOAT-825 chromium-free passivating agent is solvent-based, used as the original solution, operating at room temperature, passivation time 30 - 90 s.

[0035] The specific process is: "brightening with 1.5% nitric acid by volume → water washing → activation with 1.5% sulfuric acid by volume → water washing → drying → chromium-free passivation".

[0036] The stainless steel parts are baked at 70 - 90 °C for 20 - 25 min after chromium-free passivation. Example 1

[0037] As Figure 1As shown in the figure, a coating structure of cyanide-free cadmium plating and chromium-free passivation includes a stainless steel substrate 1, and an impact nickel coating 2, a cyanide-free cadmium plating layer 3, and a chromium-free passivation layer 4 sequentially prepared on the stainless steel substrate 1 from the inside to the outside.

[0038] 1. Pretreatment:

[0039] 1) Degreasing:

[0040] Perform "chemical degreasing → water washing → alkaline cathodic electro-degreasing → water washing → alkaline anodic electro-degreasing → water washing" on the stainless steel substrate 1 according to the current pretreatment process.

[0041] 2) Anodic electrolytic activation:

[0042] After degreasing the stainless steel parts, activate them using the following anodic electrolytic activation process:

[0043] Sulfuric acid 150 g / L, operating at room temperature, anodic current density 1.0 A / dm 2 , electrolysis time 40 s.

[0044] 3) Cathodic electrolytic activation:

[0045] After anodic electrolytic activation of the stainless steel parts, activate them using the following cathodic electrolytic activation process:

[0046] Sulfuric acid 150 g / L, operating at room temperature, cathodic current density 1.5 A / dm 2 , electrolysis time 40 s.

[0047] 2. Plating impact nickel:

[0048] After pretreatment of the stainless steel parts, prepare the impact nickel coating 2 using the following impact nickel plating process.

[0049] Nickel chloride hexahydrate 100 g / L, hydrochloric acid 100 g / L, operating at room temperature, cathodic current density 4 A / dm 2 , plating time 4 min.

[0050] 3. Cyanide-free cadmium plating:

[0051] After plating the impact nickel on the stainless steel parts, prepare the cyanide-free cadmium plating layer 3 using the PULIZIER NCC-617 potassium chloride cyanide-free cadmium plating process of Superbond Chemical Industry, and the thickness of the cadmium plating layer is 12 μm.

[0052] 30 g / L cadmium chloride, 120 g / L potassium chloride, 120 g / L PULIZIER NCC-617 complexing agent, 1.5 mL / L PULIZIER NCC-617 brightening agent, 28 mL / L PULIZIER NCC-617 auxiliary agent, 8 mL / L PULIZIER NCC-617 high area brightening agent, bath pH 8, operating temperature 35 °C, cathode current density 1.0 A / dm 2 , cathode movement 3 m / min.

[0053] 4. Chromium-free passivation:

[0054] After cyanide-free cadmium plating of stainless steel parts, a chromium-free passivation layer 4 is prepared using SUPERBON CHEMICAL's Zincot PRODICO Z-Caot 888 FL chromium-free passivating agent, and the thickness of the passivation layer is 0.9 μm.

[0055] Zincot PRODICO Z-Caot 888 FL is solvent-based, used as the stock solution, operated at room temperature, and the passivation time is 60 s.

[0056] The specific process is: "Pickling in 1.5% nitric acid by volume → Water washing → Activation in 1.5% sulfuric acid by volume → Water washing → Drying → Chromium-free passivation".

[0057] 5. Drying:

[0058] After chromium-free passivation of stainless steel parts, bake at 80 °C for 20 min. Example 2

[0059] As Figure 1 shown, a coating structure of cyanide-free cadmium plating and chromium-free passivation includes a stainless steel substrate 1, and an impact nickel coating 2, a cyanide-free cadmium coating 3, and a chromium-free passivation coating 4 sequentially prepared on the stainless steel substrate 1 from the inside to the outside.

[0060] 1. Pretreatment:

[0061] 1) Degreasing:

[0062] According to the current pretreatment process, the stainless steel part substrate 1 is subjected to "chemical degreasing → water washing → alkaline cathodic electro-degreasing → water washing → alkaline anodic electro-degreasing → water washing".

[0063] 2) Anodic electrolytic activation:

[0064] After degreasing the stainless steel parts, the following anodic electrolytic activation process is used for activation:

[0065] 200 g / L sulfuric acid, operated at room temperature, anode current density 1.0 A / dm 2 , electrolysis time 40 s.

[0066] 3) Cathodic electrolytic activation:

[0067] After the anodic electrolytic activation of the stainless-steel parts, the following cathodic electrolytic activation process is used for activation:

[0068] Sulfuric acid: 200 g / L, operating at room temperature, cathodic current density: 1.5 A / dm 2 , electrolysis time: 40 s.

[0069] 2. Electroplating shock nickel:

[0070] After the pretreatment of the stainless-steel parts, the following process for electroplating shock nickel is used to prepare the shock nickel coating 2.

[0071] Nickel chloride hexahydrate: 120 g / L, hydrochloric acid: 120 g / L, operating at room temperature, cathodic current density: 4 A / dm 2 , plating time: 4 min.

[0072] 3. Non-cyanide cadmium plating:

[0073] After the stainless-steel parts are electroplated with shock nickel, the PULIZIER NCC-617 potassium chloride non-cyanide cadmium plating process of Superbond Chemical Industry is used to prepare the non-cyanide cadmium coating 3, and the thickness of the cadmium coating is 12 μm.

[0074] Cadmium chloride: 35 g / L, PULIZIER NCC-617 complexing agent: 140 g / L, potassium chloride: 100 g / L, PULIZIER NCC-617 brightener: 1.5 mL / L, PULIZIER NCC-617 auxiliary agent: 28 mL / L, PULIZIER NCC-617 high-zone brightener: 8 mL / L, pH of the plating solution: 8, working temperature: 30 °C, cathodic current density: 1.0 A / dm 2 , cathode moving speed: 3 m / min.

[0075] 4. Chromium-free passivation:

[0076] After the stainless-steel parts are non-cyanide cadmium plated, the zinc-free ZECCOAT-825 chromium-free passivating agent of Superbond Chemical Industry is used to prepare the chromium-free passivation layer 4, and the thickness of the passivation layer is 0.9 μm.

[0077] The zinc-free ZECCOAT-825 chromium-free passivating agent is solvent-based, used as the original solution, operating at room temperature, passivation time: 60 s.

[0078] The specific process is: "Pickling with 1.5% nitric acid by volume → Water washing → Activation with 1.5% sulfuric acid by volume → Water washing → Drying → Chromium-free passivation".

[0079] 5. Drying:

[0080] After the stainless-steel parts are chromium-free passivated, they are baked at 80 °C for 20 min.

[0081] Test example 1:

[0082] The cadmium-free electroplated cadmium stainless steel samples prepared in Example 1 and Example 2 were subjected to an acetate salt spray test for 450 h in accordance with GB / T 10125–2021 "Artificial atmosphere corrosion test - Salt spray test". No rusting occurred on the surface of the plated parts, and the coating had excellent corrosion resistance.

[0083] Test Example 2:

[0084] The cadmium-free electroplated cadmium stainless steel samples prepared in Example 1 and Example 2 were used to test the adhesion of the coating by the thermal shock method in accordance with GB / T 5270-2005 "Review of test methods for adhesion of metallic and other non-metallic coatings on metallic substrates". The plated parts were placed in a heating furnace and heated to 300 °C and held for 30 min, then taken out and quenched suddenly in water at room temperature. No blistering or peeling of the coating occurred. The test shows that the coating structure prepared by the present utility model has good adhesion.

[0085] 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 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 modifications 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 cyanide-free cadmium plating and chromium-free passivation, characterized in that: It includes a stainless steel substrate, and an impact nickel plating layer, a cyanide-free cadmium plating layer, and a chromium-free passivation layer which are sequentially prepared on the stainless steel substrate from the inside to the outside; The chromium-free passivation layer is a passivation layer prepared by using a solvent-based silane chromium-free passivating agent.

2. The coating structure of cyanide-free cadmium plating and chromium-free passivation according to claim 1, characterized in that: The thickness of the chromium-free passivation layer is 0.8 to 1.0 μm.

3. The coating structure of cyanide-free cadmium plating and chromium-free passivation according to claim 1, characterized in that: The thickness of the cyanide-free cadmium plating layer is 6 to 15 μm.

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