High-temperature-resistant anti-tarnish agent for cyanide-free galvanized passivation film

Abstract

The invention discloses a cyanide-free galvanized passivation film high-temperature-resistant anti-tarnishing agent, which is characterized in that the anti-tarnishing agent is composed of a water-soluble compound of n-octylamine and 1-aminopropane, and the mass ratio of the water-soluble compound of n-octylamine to the water-soluble compound of 1-aminopropane is (1.25-5.25): 1. According to the cyanide-free zinc plating solution of the anti-tarnish agent, after electroplating, the high temperature resistance and tarnish resistance of a passivation film of a zinc coating are greatly improved, the appearance of the cyanide-free zinc plating passivation film is improved, and the addition of the anti-tarnish agent does not generate adverse effects on other properties of the plating solution. The appearance requirement of a passive film after the cyanide-free zinc coating is baked at high temperature is met, and the method can be used for production.

Description

Technical Field

[0001] The invention relates to the technical field of electroplating, and more particularly to a high temperature resistant and anti-discoloration agent for a cyanide-free zinc plating passivation film. Background Art

[0002] Zinc coating has a remarkable bluish-white appearance in industrial applications, and its standard electrode potential is -0.76V. Zinc, as a typical amphoteric metal, is easily soluble in acid and alkali, which means that it can show good solubility in various chemical environments. Since the standard potential of zinc is more negative than that of iron, zinc coating can provide reliable electrochemical protection as an anodic coating in steel products. This anodic coating can form a protective zinc layer on the surface of steel to prevent steel corrosion by sacrificing zinc. In the electroplating industry, electroplating zinc occupies a very important position, accounting for nearly 50% of the total electroplating volume. Whether in industrial atmosphere, rural atmosphere or marine atmosphere, steel products using zinc as a protective layer have shown good protective performance. In particular, the thickness of the zinc layer is almost proportional to its protective life, which makes it possible to effectively extend the service life of steel products by controlling the thickness of the zinc layer.

[0003] In order to further improve the corrosion resistance of the zinc coating, the zinc coating is usually subjected to chromate passivation treatment. After passivation treatment, the corrosion resistance of the zinc coating can be increased by 6 to 8 times. Therefore, passivation treatment is an indispensable step in the zinc plating process. In my country, as early as the cyanide-free electroplating movement in the 1970s, the cyanide-free zinc plating process has become mature. Up to now, cyanide-free zinc plating has become one of the most mature processes in cyanide-free electroplating. Realizing cyanide-free zinc plating can significantly reduce the use of cyanide in the electroplating industry, so it has good environmental significance and technical background.

[0004] In high-demand fields such as aerospace, the treatment of zinc coating is more stringent, usually requiring dehydrogenation treatment to eliminate hydrogen embrittlement, followed by chromate passivation; however, traditional cyanide-free zinc coating is often difficult to passivate into a good quality passivation film after dehydrogenation treatment, and the appearance is difficult to meet the requirements; therefore, the improved cyanide-free zinc plating process must not only ensure the quality and corrosion resistance of the coating, but also overcome the technical difficulties of the traditional process in the dehydrogenation and passivation process to ensure that high standards of appearance and performance are met. Summary of the invention

[0005] The purpose of the invention is to provide a high temperature resistant anti-discoloration agent for a cyanide-free zinc plating passivation film, so as to solve the problems that it is difficult to passivate a passivation film of good quality and the appearance is difficult to meet the requirements in the prior art.

[0006] The above technical purpose of the present invention is achieved through the following technical scheme: a high temperature resistant anti-discoloration agent for a cyanide-free zinc passivation film, wherein the anti-discoloration agent is composed of a water-soluble compound of mono-n-octylamine and 1-aminopropane, and the mass ratio of the compound of mono-n-octylamine and 1-aminopropane is 1.25-5.25:1.

[0007] By adopting the above technical scheme, the mono-n-octylamine in the present invention has good chemical stability and adhesion performance, can form a stable chemical bond on the galvanized surface, and the substance can react with the zinc surface during the passivation treatment to form a dense passivation film, thereby enhancing the corrosion resistance of the coating; the 1-aminopropane of the present invention is a polymer compound with multiple functional groups, which can form a stable molecular structure in an aqueous solution, and these functional groups can further interact with the zinc surface and the mono-n-octylamine to enhance the compactness and adhesion of the passivation film;

[0008] The present invention can form a dense and uniform passivation film on the galvanized surface through the synergistic effect of the above-mentioned compounds, significantly improving the quality and stability of the passivation film. The anti-discoloration agent can still maintain its chemical stability in a high temperature environment, prevent the passivation film from discoloring or decomposing, and improve the high temperature resistance of the galvanized layer. The cyanide-free process avoids the use of highly toxic cyanide, greatly reduces pollution to the environment, and meets modern environmental protection requirements. The surface of the galvanized layer after the passivation treatment is smooth and uniform, and has a good appearance, meeting the high requirements of appearance quality standards, and is particularly suitable for high-end application fields such as aerospace. Due to the high efficiency and environmental protection of the passivator, it has broad application prospects in the fields of steel products, automotive parts, electronic equipment, etc.

[0009] Another object of the present invention is to provide an electroplating solution to which a high temperature resistant anti-discoloration agent is added to a cyanide-free zinc plating passivation film, wherein the electroplating solution comprises zinc oxide, sodium hydroxide, a brightener and an anti-discoloration agent.

[0010] The present invention is further configured as follows: the mass concentration of the zinc oxide is 8-20 g / L, the mass concentration of the sodium hydroxide is 80-150 g / L, the mass concentration of the brightener is 1-20 g / L, and the mass concentration of the anti-discoloration agent is 1-10 g / L.

[0011] The present invention is further configured as follows: the brightener is a 3-methoxy-4-hydroxybenzaldehyde organic compound.

[0012] By adopting the above technical scheme, the zinc oxide in the electroplating solution with a cyanide-free zinc plating passivation film high temperature resistant anti-discoloration agent provided by the present invention provides zinc ions in the electroplating solution, which is the main source of the zinc coating in the zinc plating process; the sodium hydroxide is used to adjust the pH value of the electroplating solution, provide an alkaline environment, enhance the conductivity of the electrolyte solution, and ensure the smooth progress of the zinc plating process; 3-methoxy-4-hydroxybenzaldehyde as an organic brightener can promote the uniform deposition of the coating during the electroplating process, improve the brightness and smoothness of the coating, and make the coating more beautiful in appearance; the anti-discoloration agent is composed of a mixture of mono-n-octylamine and 1-aminopropane, which enhances the compactness and adhesion of the passivation film of the coating through chemical reactions;

[0013] After adding the anti-discoloration agent, a dense passivation film is formed on the surface of the coating, which significantly improves the quality and stability of the coating and makes it have excellent corrosion resistance. The active ingredients in the anti-discoloration agent form stable chemical bonds on the surface of the coating, which improves the stability of the coating under high temperature conditions and prevents the coating from discoloring or fading in a high temperature environment. The addition of the brightener makes the surface of the coating smooth, uniform and bright, and the appearance quality is significantly improved, meeting the high-demand appearance standards. The cyanide-free electroplating solution avoids the use of highly toxic cyanide, greatly reduces the pollution to the environment, meets modern environmental protection requirements, and is conducive to the promotion and application of the process. Due to its excellent high temperature resistance, anti-discoloration and corrosion resistance, the electroplating solution is suitable for various fields requiring high-quality coatings, such as automobiles, aerospace, electronic equipment, etc., and has broad application prospects. The formation of high-quality coatings can extend the service life of products, reduce maintenance and replacement costs, increase product added value, and bring significant economic benefits.

[0014] In summary, the present invention has the following beneficial effects:

[0015] 1. The introduction of mono-n-octylamine and 1-aminopropane in the present invention expands the polarization range of the plating solution and increases the cathode polarization capacity. The expansion of the polarization range and the increase of the cathode polarization capacity further refine the coating grains and improve the microstructure quality of the coating. After the zinc coating is dehydrogenated at high temperature, the appearance of the passivation film is significantly improved, avoiding the problem of darkening of the traditional coating after high-temperature treatment.

[0016] 2. The addition of the anti-discoloration agent of the present invention has no negative impact on other properties of the plating solution, ensuring the overall performance stability of the plating solution. The cyanide-free zinc plating solution containing the anti-discoloration agent can form a dense and stable passivation film on the surface of the coating, thereby improving the appearance quality and corrosion resistance of the coating. The present invention significantly improves the comprehensive benefits of the coating by refining the grains, improving the appearance, ensuring stable performance and other improvements, and is suitable for high-demand applications such as aerospace, automobiles, and electronic equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1This is a schematic diagram of the appearance of the coating without adding the anti-discoloration agent of Example 1 in the present invention;

[0018] Figure 2 Schematic diagram of the appearance of the coating layer in which the anti-discoloration agent of Example 1 is added in the present invention;

[0019] Figure 3 This is a schematic diagram of the appearance of the coating without adding the anti-discoloration agent of Example 2 in the present invention;

[0020] Figure 4 Schematic diagram of the appearance of the coating layer in which the anti-discoloration agent of Example 2 is added in the present invention;

[0021] Figure 5 This is a schematic diagram of the appearance of the coating without adding the anti-discoloration agent of Example 3 in the present invention;

[0022] Figure 6 Schematic diagram of the appearance of the coating with the anti-discoloration agent added in Example 3 of the present invention. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. The experimental methods without specific conditions in the embodiments are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0024] Example 1: A high temperature resistant anti-discoloration agent for a cyanide-free zinc plating passivation film. The anti-discoloration agent in Example 1 is composed of the following components in terms of mass ratio (the anti-discoloration agent is represented by a):

[0025] Anti-discoloration agent a: The mass ratio of the mixture of mono-n-octylamine and 1-aminopropane is 1.25:1. When used, deionized water is used to prepare a solution and then added to the zinc plating solution according to the corresponding working concentration.

[0026] Test method:

[0027] Preparation before the experiment: Make sure all equipment and containers have been cleaned to avoid contamination of the electroplating solution, and place the experimental tank in a well-ventilated area to prevent sodium hydroxide vapor from affecting the health of operators;

[0028] Prepare the electroplating solution: accurately weigh 20g zinc oxide and 240g sodium hydroxide, place them in clean containers, add 400ml deionized water to the experimental tank, and then carefully add 240g sodium hydroxide. Use a stirring device such as a magnetic stirrer to ensure that the sodium hydroxide is completely dissolved to form a transparent solution;

[0029] Add zinc oxide: In another container, add appropriate amount of water to make 20g zinc oxide into a paste to avoid lumps. Slowly add the zinc oxide paste to the solution containing sodium hydroxide and continue stirring until it is completely dissolved;

[0030] Adjust the volume and temperature: Continue to add water until the volume of the plating solution reaches 2L, ensure that the zinc oxide is completely dissolved, use a thermometer to monitor the solution temperature, and wait for it to cool to room temperature (about 20°C);

[0031] Add brightener: Accurately weigh 3g of 3-methoxy-4-hydroxybenzaldehyde as brightener, add the brightener to the plating solution at room temperature, and ensure sufficient stirring to evenly disperse;

[0032] Electroplating operation: Use the pre-treated steel parts as cathodes and stainless steel as anodes, hang and fix them in the experimental tank, adjust the parameters of the electroplating equipment, and set the current density to 1A / dm 2 , temperature is 20℃, and plating time is 40 minutes;

[0033] High-temperature dehydrogenation and passivation treatment: After the electroplating is completed, the steel parts are taken out and dehydrogenated at 200°C for 4 hours. Subsequently, the steel parts are subjected to chromate passivation treatment to enhance their corrosion resistance;

[0034] Test and record: Test the treated workpiece and record the performance indicators such as appearance, corrosion resistance, hardness, etc. The test results are as attached. Figure 1 shown.

[0035] According to the formula of the above cyanide-free zinc plating solution, add 5g / L anti-discoloration agent a, and also conduct the experiment in a 2L experimental tank. The electroplating parameters are the same as above. After electroplating, remove hydrogen and passivate to observe the color change. The test results are shown in the attached Figure 2 shown.

[0036] Example 2: A high temperature resistant anti-discoloration agent for a cyanide-free zinc plating passivation film. The components of the anti-discoloration agent in Example 2 are composed of the following components in terms of mass ratio (the anti-discoloration agent is represented by b):

[0037] Anti-discoloration agent b: The mass ratio of the mixture of mono-n-octylamine and 1-aminopropane is 2.5:1. When used, it is prepared into a solution with deionized water and then added into the zinc plating solution according to the corresponding working concentration.

[0038] The test method is the same as that in Example 1, and the test results are shown in the attached Figure 3 According to the formula of the above cyanide-free zinc plating solution, add 8g / L anti-discoloration agent b, and conduct the experiment in a 2L experimental tank. The electroplating parameters are the same as above. After electroplating, dehydrogenation passivation is performed to observe the color change. The test results are shown in the attached Figure 4 shown.

[0039] Example 3: A high temperature resistant anti-discoloration agent for a cyanide-free zinc plating passivation film. The anti-discoloration agent in Example 3 is composed of the following components in terms of mass ratio (the anti-discoloration agent is represented by c):

[0040] Anti-discoloration agent C: The mass ratio of the mixture of mono-n-octylamine and 1-aminopropane is 5.25:1. When used, it is prepared into a solution with deionized water and then added into the zinc plating solution according to the corresponding working concentration.

[0041] The test method is the same as that in Example 1, and the test results are shown in the attached Figure 5 According to the above formula of cyanide-free zinc plating solution, add 10g / L anti-discoloration agent c, and conduct the experiment in a 2L experimental tank. The electroplating parameters are the same as above. After electroplating, remove hydrogen and passivate to observe the color change. The test results are shown in the attached Figure 6 shown.

[0042] Experimental conclusion: Based on the above experimental results and graphical analysis, the following conclusions can be drawn:

[0043] Without anti-tarnish agent:

[0044] Appearance: From the attached Figure 1 , 3 As can be seen from Figure 5, if no anti-discoloration agent is added, the passivation film of the workpiece will be dull and lack luster and brightness after cyanide-free zinc plating and passivation treatment. This dull appearance cannot meet the production requirements for product aesthetics and quality, especially in application scenarios with high requirements for appearance.

[0045] After adding anti-discoloration agent:

[0046] Appearance: From the attached Figure 2 , 4 As can be seen in Figure 6, the appearance of the passivation film of the workpiece after adding the cyanide-free zinc plating high temperature resistant anti-discoloration agent has been significantly improved. The color is bright and bright, with better visual effects, which can meet the high standard appearance requirements of production. This obvious appearance improvement not only improves the beauty of the product, but also enhances its market competitiveness.

[0047] In summary, the application of adding anti-discoloration agent in cyanide-free zinc plating solution can significantly improve the appearance color of the workpiece passivation film by expanding the polarization range of the plating solution and increasing the cathode polarization capacity, and refining the plating layer grains, making it bright and bright to meet production requirements. At the same time, the other properties of the plating solution remain unchanged, ensuring the overall quality and effect of the electroplating process. This improvement provides a new solution for cyanide-free zinc plating technology and enhances the market competitiveness of the product.

[0048] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A cyanide-free zinc plating passivation film high temperature resistant anti-discoloration agent, characterized by: The anti-discoloration agent is composed of a water-soluble compound of mono-n-octylamine and 1-aminopropane.

2. A cyanide-free zinc plating passivation film high temperature resistant anti-discoloration agent as claimed in claim 1, characterized in that: Calculated by mass concentration, the concentrations of the components in the anti-discoloration agent are: 20-50 g / L of mono-n-octylamine and 15-25 g / L of 1-aminopropane.

3. An electroplating solution to which the cyanide-free zinc plating passivation film high temperature resistant anti-discoloration agent as claimed in claim 1 is added, characterized in that: The electroplating solution comprises zinc oxide, sodium hydroxide, a brightener and an anti-discoloration agent.

4. The electroplating solution according to claim 3, wherein the electroplating solution comprises a cyanide-free zinc plating passivation film high temperature resistant anti-discoloration agent, wherein: The mass concentration of the zinc oxide is 8-20 g / L, the mass concentration of the sodium hydroxide is 80-150 g / L, the mass concentration of the brightener is 1-20 g / L, and the mass concentration of the anti-discoloration agent is 1-10 g / L.

5. The electroplating solution as claimed in any one of claims 3 to 4, wherein the electroplating solution comprises a cyanide-free zinc plating passivation film high temperature resistant anti-discoloration agent, wherein: The brightener is a 3-methoxy-4-hydroxybenzaldehyde organic compound.

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