Preparation and use method of gel electric brush galvanizing medium

Abstract

The invention relates to a preparation and use method of a gel electric brush galvanization medium, which comprises the following steps: preparing a main salt solution and a gel medium precursor solution, heating the main salt solution to 80-90 DEG C, dropwise adding the main salt solution into the gel medium precursor solution, and heating and stirring the gel medium precursor solution in the dropwise adding process to obtain the gel electric brush galvanization medium. Maintaining the temperature of the gel medium precursor solution to be higher than 90 DEG C, and continuously stirring and heating after dropwise adding until a milk white solution is obtained; placing the milk white solution in a low-temperature freezing environment for not less than 8 hours; and unfreezing in a natural environment to obtain the gel brush plating medium. The coating is uniform and compact, the splashing risk is low, the coating can be used for local plating, and equipment is simple.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electroplating, in particular to a preparation method and use method of a gel electro-brush plating zinc medium. BACKGROUND The zinc plating process is one of the important process technologies in aviation manufacturing, which is widely used in the manufacturing of landing gear, engine shell and other parts. The commonly used zinc plating process can be divided into four categories according to the electroplating solution, which are cyanide zinc plating, zincate zinc plating, potassium salt zinc plating and sulfate zinc plating. For the brush plating process, an alkaline zinc plating solution is commonly used. This process has the risk of flowing of the plating solution, easy pollution of non-electroplating area, strong alkalinity of the plating solution, easy chemical burns caused by improper operation, and irritating fumes of the alkaline zinc plating solution to the respiratory tract. The process improvement of brush plating zinc is focused on the brush plating device, pretreatment method and post-treatment process improvement. For the plating solution itself, the focus is on changing its toxicity and using a cyanide-free process instead of a cyanide process. There is no report on improving the flowability of the plating solution. The present application focuses on solving the problem of flow of the plating solution in the brush plating process. SUMMARY

[0002] The purpose of the present application is: The current repair of the zinc plating layer of the parts is carried out by using the electro-brush plating method. The brush plating solution used in this method has strong alkalinity and is in the form of solution, which can easily cause splashing and flowing during the brush plating process, resulting in pollution of the non-repair area. In addition, the solution type plating solution can easily cause chemical burns when operated improperly.

[0003] The technical solution of the present application is: The present application solves the problem of flow in the brush plating process by developing a new type of solid brush plating medium. The formula does not contain toxic cyanide and belongs to a new type of low-toxicity brush plating zinc formula.

[0004] To avoid the flow of the brush plating solution, a high molecular material capable of forming a gel is added to solidify the brush plating solution, so as to obtain a solid conductive brush plating medium. The electrical conductivity of the solid conductive brush plating medium is low, and the content of different components in the formula needs to be adjusted to ensure the quality and efficiency of the brush plating. Since the brush plating medium has been changed, the brush plating process is optimized to ensure the quality of the brush plating. Therefore, the technical solution of the present application includes: preparation of a gel electro-brush plating zinc medium and a method for brush plating zinc.

[0005] A preparation method of a gel electro-brush plating zinc medium is provided, which comprises the following steps: Step 1, preparation of a main salt solution and a gel medium precursor solution A soluble sodium or potassium salt solid is dissolved in water as an additive until it is completely dissolved to obtain a colorless solution. A conductive salt is added to the colorless solution, and after the conductive salt is completely dissolved, a main salt and a complexing agent are added to obtain a main salt solution. The conductive salt is one of sodium chloride, potassium chloride, or ammonium chloride. The main salt is one of zinc oxide, zinc acetate, zinc chloride, zinc sulfate, or zinc citrate. The complexing agent is one of ammonium chloride, nitrilotriacetic acid, triethanolamine, or tetraethylenepentamine. Water is heated to 95°C and stirred. While stirring, a polymer additive is added to form a mixed solution. The polymer additive is one of polyvinyl alcohol, polyacrylic acid, polyacrylamide, and nano silica. When the mixed solution changes from turbid to clear, a gel medium precursor solution is obtained. Step 2: Heat the main salt solution to 80℃~90℃, then add it dropwise to the gel medium precursor solution. During the dropwise addition, maintain heating and stirring of the gel medium precursor solution to keep its temperature above 90℃. After the dropwise addition is complete, continue stirring and heating until a milky white solution is obtained. The concentration of the conductive salt in the milky white solution is 3g / L~10g / L; the concentration of sodium or potassium in the milky white solution is 10g / L~70g / L; the concentration of zinc ions in the milky white solution is 10g / L~50g / L; and the concentration of the polymer in the milky white solution is 50g / L~200g / L. Step 3: Place the milky white solution in a low-temperature freezing environment for no less than 8 hours; the low-temperature freezing temperature range is -18℃ to -15℃. Step 4: After thawing in a natural environment, a gel brush plating medium is obtained.

[0006] Furthermore, the sodium or potassium salt solid is one of sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate. More preferably, the concentration of the sodium or potassium salt in the milky white solution is 25 g / L to 40 g / L.

[0007] Furthermore, the concentration of zinc ions in the milky white solution ranges from 15 g / L to 48 g / L.

[0008] Furthermore, the concentration of the complexing agent is 0.8 to 5.0 times the concentration of zinc ions. Even further, the concentration of the complexing agent is 2.5 to 5 times the concentration of zinc ions.

[0009] Furthermore, in step 1, after adding the complexing agent, the mixture is stirred and heated to a temperature above 80°C.

[0010] Furthermore, the concentration of the polymeric additive in the milky white solution is 80 g / L to 150 g / L.

[0011] Furthermore, in step 2, the stirring and heating time should be at least 30 minutes after the addition is completed.

[0012] A method for using a gel-based zinc plating medium via an electric brush is provided, comprising the following steps: Step 1: Wipe the surface of the parts with an organic solvent to remove surface marks or dirt; after degreasing with organic solvent, immerse the parts in a degreasing solution containing alkaline substances, then rinse with water to remove alkaline substances from the surface of the parts, and then dry them. Step 2: Apply the gel plating medium described above to the surface of the part to be plating. The thickness of the applied gel plating medium should be 5mm to 20mm. Select a suitable electrode for electroplating. The electroplating time should be adapted to the plating thickness. The cathode current density should be 2 to 4 A / dm³. 2 ; Step 3: After electroplating, rinse with water, brighten with 3% dilute nitric acid, rinse with clean water, passivate with trivalent chromium passivating agent, keep the passivation solution in place for 15s to 30s, rinse with water and dry.

[0013] Furthermore, the organic solvent is ethanol or butanone. Furthermore, the alkaline substance in the degreasing solution containing an alkaline substance is sodium hydroxide, sodium carbonate, or trisodium phosphate.

[0014] The advantages of this invention are: 1. Uniform and dense coating: The high viscosity of the gel medium limits the ion diffusion rate, ensuring uniform coating thickness (±1μm) and avoiding excessive thickness at the edges or missed coating.

[0015] 2. Low risk of splashing: The gel medium has strong adhesion, reducing the harm to operators caused by solution splashing.

[0016] 3. The entire electroplating process is carried out at room temperature: no high-temperature bath is required (traditional electroplating requires 40-60℃), reducing the risk of burns.

[0017] 4. Can be used for localized plating: Eliminates the need for overall immersion plating, avoiding contamination of non-plated areas, and is suitable for precise repair of complex-shaped parts. 6. Simple equipment: Only requires a DC power supply, electrodes, and molds; floor space < 0.5m² 2 It is suitable for on-site operations. The equipment used is the same as that used for the original electroplating solution, and no modifications are required. Detailed Implementation

[0018] In fact, many different examples can be described, and these examples should not be construed as limited to those set forth herein. Rather, these examples are described so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0019] Example 1 – Brush-plating zinc onto copper test pieces: 1. Preparation of gel brush plating medium (taking 1L plating medium as an example): (1) Preparation of main salt solution: Dissolve 30g sodium hydroxide in 115ml deionized water and stir until dissolved. Add 5g potassium chloride and stir until completely dissolved. Slowly add 20g zinc oxide and stir continuously at 95℃ for 30 minutes. After dissolving, add 30g ammonium chloride. The final solution is colorless and transparent.

[0020] (2) Preparation of gel precursor solution: Heat 700ml of deionized water to 95℃ in another container, slowly add 100g of polyvinyl alcohol to 700ml of deionized water while stirring. After the addition is complete, continue stirring and heating until the solution changes from turbid to clear and transparent.

[0021] (3) Mix the main salt with the gel precursor solution: Slowly add the main salt solution dropwise into the gelling amine precursor solution while stirring continuously. After the addition is complete, continue heating and stirring for 30 minutes to form a milky white solution.

[0022] (4) Freezing and setting: Pour the solution into the mold and freeze at 18°C ​​for 8 hours.

[0023] (5) Thawing and use: Remove the frozen gel and thaw at room temperature before use. 2. Copper test piece brush plating process: (1) Pretreatment of copper test pieces: Organic dissolution degreasing: Ultrasonic cleaning with anhydrous ethanol for 5 minutes to remove oil and fingerprints; Chemical degreasing: Soaking in a chemical degreasing solution at 50℃ (formula: sodium hydroxide 20g / L + sodium carbonate 15g / L + sodium phosphate 10g / L) for 3 minutes, rinsing with water and drying; Acid activation: Soaking in 5% sulfuric acid solution for 10 seconds to remove residual oxide film, rinsing with water and immediately entering the brush plating process.

[0024] (2) Brush plating: The current density is controlled at 2.5 A / dm² according to the area of ​​the test piece. 2 Brush plating is performed, and the plating time is approximately 15 minutes.

[0025] 3) Post-treatment: Brightening: Immerse in 3% nitric acid solution for 5 seconds, rinse with water to remove surface dust; Trivalent chromium passivation: Immerse at 30℃ for 3 minutes, rinse with water and dry (Trivalent chromium passivation formula: 25g / l chromium nitrate + 15g / l boric acid). After brush plating, a zinc plating layer with a thickness of 5μm-8μm can be obtained. The plating layer is uniform, dense, and has a silvery-white metallic luster, without any missed plating, blistering, or cracks. The corrosion resistance and adhesion of the plating layer meet the requirements for aerospace zinc plating layers.

[0026] Example 2 – Gel-coated zinc plating on the inner and outer surfaces of copper tubes (outer diameter 40mm x wall thickness 1.5mm): 1. Preparation of gel brush plating medium (taking 1L plating medium as an example): (1) Preparation of main salt solution: Dissolve 35g potassium hydroxide in 132mL water, add 8g ammonium chloride to dissolve, then slowly add 25g zinc acetate and stir until clear.

[0027] (2) Preparation of gel precursor solution: Add 120g of polyacrylamide to 680ml of deionized water. Heat to 80℃ and stir until completely dissolved. … (3) Mixing and curing of main salt and gel precursor solution: Mix main salt solution with polyacrylamide solution: Stir for 35 minutes and then inject into mold: Freeze at -20℃ for 12 hours.

[0028] 2. Electroplating of copper pipes: (1) Copper tube pretreatment process: First, ultrasonic immersion degreasing is performed in an ethanol:water = 1:1 solution for 10 minutes (frequency 40kHz); the second step is chemical degreasing: immersion in a 60℃ chemical degreasing solution (solution formula: sodium hydroxide 30g / L + sodium carbonate 20g / L + OP-10 emulsifier 5g / L) for 1 minute. After rinsing with clean water, electroplating is performed.

[0029] (2) Electroplating: The current density on the outer surface of the copper tube is 3.0 A / dm. 2 Brush plating was performed at a constant current at a speed of 0.5 m / min for approximately 20 minutes. An auxiliary electrode was used for plating the inner surface of the copper tube. Electroplating gel was filled into the tube, and an electrode of the same length as the copper tube was inserted into the gel, ensuring close contact and compaction between the gel, the electroplating rod, and the copper tube.

[0030] (3) Post-treatment: Brightening: Immerse in 3% nitric acid solution for 5 seconds, rinse with water to remove surface dust; Trivalent chromium passivation: Immerse at 30℃ for 3 minutes, rinse with water and blow dry (Trivalent chromium passivation formula: 25g / L chromium nitrate + 1g / L boric acid) This method can repair the outer surface coating while ensuring the uniformity and integrity of the inner surface coating.

[0031] Descriptions of various advantageous arrangements have been shown for illustrative and descriptive purposes, but such descriptions are not intended to be exclusive or limited to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. Furthermore, different advantageous examples may describe different advantages compared to other advantageous examples. One or more examples have been selected and described in order to best illustrate the principles and practical application of the examples, and to enable those skilled in the art to understand that this disclosure contains various examples with various modifications suitable for the particular intended use.

Claims

1. A method for preparing a gel-based zinc plating medium, characterized in that, Includes the following steps: Step 1: Prepare the main salt solution and gel medium precursor solution. A soluble sodium or potassium salt solid is dissolved in water as an additive until it is completely dissolved to obtain a colorless solution. A conductive salt is added to the colorless solution, and after the conductive salt is completely dissolved, a main salt and a complexing agent are added to obtain a main salt solution. The conductive salt is one of sodium chloride, potassium chloride, or ammonium chloride. The main salt is one of zinc oxide, zinc acetate, zinc chloride, zinc sulfate, or zinc citrate. The complexing agent is one of ammonium chloride, nitrilotriacetic acid, triethanolamine, or tetraethylenepentamine. Water is heated to 95°C and stirred. While stirring, a polymer additive is added to form a mixed solution. The polymer additive is one of polyvinyl alcohol, polyacrylic acid, polyacrylamide, and nano silica. When the mixed solution changes from turbid to clear, a gel medium precursor solution is obtained. Step 2: Heat the main salt solution to 80℃~90℃, then add it dropwise to the gel medium precursor solution. During the dropwise addition, maintain heating and stirring of the gel medium precursor solution to keep its temperature above 90℃. After the dropwise addition is complete, continue stirring and heating until a milky white solution is obtained. The concentration of the conductive salt in the milky white solution is 3g / L~10g / L; the concentration of sodium or potassium in the milky white solution is 10g / L~70g / L; the concentration of zinc ions in the milky white solution is 10g / L~50g / L; and the concentration of the polymer in the milky white solution is 50g / L~200g / L. Step 3: Place the milky white solution in a low-temperature freezing environment for no less than 8 hours; the low-temperature freezing temperature range is -18℃ to -15℃. Step 4: After thawing in a natural environment, a gel brush plating medium is obtained.

2. The method for preparing a gel brush zinc plating medium according to claim 1, characterized in that: The sodium or potassium salt solid is one of sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate.

3. The method for preparing a gel brush zinc plating medium according to claim 2, characterized in that: The concentration of sodium or potassium salts in the milky white solution is 25 g / L to 40 g / L.

4. The method for preparing a gel brush zinc plating medium according to claim 1, characterized in that: The concentration of zinc ions in the milky white solution ranges from 15 g / L to 48 g / L.

5. The method for preparing a gel brush zinc plating medium according to claim 1, characterized in that: The concentration of the complexing agent is 0.8 to 5.0 times the concentration of zinc ions. Furthermore, the concentration of the complexing agent is 2.5 to 5 times the concentration of zinc ions.

6. The method for preparing a gel brush zinc plating medium according to claim 1, characterized in that: In step 1, after adding the complexing agent, the mixture is stirred and heated to a temperature above 80°C.

7. The method for preparing a gel brush zinc plating medium according to claim 1, characterized in that: The concentration of the polymer additive in the milky white solution is 80 g / L to 150 g / L.

8. The method for preparing a gel brush zinc plating medium according to claim 1, characterized in that: In step 2, after the addition is complete, continue stirring and heating for at least 30 minutes.

9. A method of using the gel brush zinc plating medium prepared according to claims 1-8, comprising the following steps: Step 1: Wipe the surface of the parts with an organic solvent to remove surface marks or dirt; after degreasing with organic solvent, immerse the parts in a degreasing solution containing alkaline substances, then rinse with water to remove alkaline substances from the surface of the parts, and then dry them. Step 2: Apply the gel plating medium described above to the surface of the part to be plating. The thickness of the applied gel plating medium should be 5mm to 20mm. Select a suitable electrode for electroplating. The electroplating time should be adapted to the plating thickness. The cathode current density should be 2 to 4 A / dm³. 2 ; Step 3: After electroplating, rinse with water, brighten with 3% dilute nitric acid, rinse with clean water, passivate with trivalent chromium passivating agent, keep the passivation solution in place for 15s to 30s, rinse with water and dry.

10. The method of using the gel brush zinc plating medium according to claim 9 uses ethanol or methyl ethyl ketone as the organic solvent. Further, the alkaline substance in the degreasing solution containing an alkaline substance is sodium hydroxide, sodium carbonate, or trisodium phosphate.