Tin salt electrolytic coloring additive and bath solution

Abstract

The invention belongs to the technical field of electrolytic coloring, and discloses a tin salt electrolytic coloring additive and a bath solution. The tin salt electrolytic coloring additive comprises a complexing agent, conductive salt, an antioxidant, a surfactant, a stabilizer and a self-cleaning functional component, the complexing agent comprises sulfamic acid and tartaric acid, the antioxidant comprises an iron complex and diamine sulfate, and the stabilizer comprises modified amino amide zinc phosphate. The self-cleaning functional component comprises sorbitol and / or sodium polycarboxylate. According to the tin salt electrolytic coloring additive provided by the invention, the stability of a tin salt electrolytic coloring process can be remarkably improved, an electrolytic coloring bath solution is kept in a good state in a long-term use process, the hydrolysis rate of tin salt is reduced, and the coloring uniformity and stability are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic coloring, and particularly relates to a tin salt electrolytic coloring additive and a bath solution. Background Art

[0002] Aluminum and its alloys are widely used in fields such as aerospace, architectural decoration, electronic equipment, and transportation due to their excellent light weight, corrosion resistance, and workability. In order to further improve the decorative performance and weather resistance of aluminum alloys, an anodic oxidation process is often used to form a dense oxide film on their surfaces, and electrolytic coloring is used to endow the products with diverse colors. Among them, the tin salt electrolytic coloring technology is widely used in industries such as building curtain walls, automotive parts, and high-end electronic product casings because it can form stable black, bronze, and other dark tones.

[0003] Currently, the common tin salt electrolytic coloring processes on the market are mainly based on stannous sulfate as the main coloring salt. Under certain pH values, current densities, temperatures, and the assistance of additives, tin ions are deposited in the pores of the anodic oxide film to form colors of different depths. However, in practical applications, the electrolytic coloring bath solutions generally have problems such as poor stability, high hydrolysis rate of tin salts, and accumulation of precipitates. The instability of the bath solution not only leads to color differences during the coloring process, but also after long-term electrolysis, the precipitates will affect the normal operation of the equipment and increase production and maintenance costs.

[0004] Therefore, developing an additive that can improve the stability of the electrolytic coloring bath solution, reduce the hydrolysis of tin salts, and improve the coloring uniformity is of great significance for optimizing the aluminum alloy electrolytic coloring process. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. For this purpose, the present invention provides a tin salt electrolytic coloring additive and a bath solution. The tin salt electrolytic coloring additive provided by the present invention can significantly improve the stability of the tin salt electrolytic coloring process, keep the electrolytic coloring bath solution in good condition during long-term use, reduce the hydrolysis rate of tin salts, and improve the coloring uniformity and stability.

[0006] In the first aspect of the present invention, a tin salt electrolytic coloring additive is provided. The tin salt electrolytic coloring additive includes a complexing agent, a conductive salt, an antioxidant, a surfactant, a stabilizer, and a self-cleaning functional component. The complexing agent includes sulfamic acid and tartaric acid. The antioxidant includes an iron complex and hydrazine sulfate. The stabilizer includes modified amino amide zinc phosphate. The self-cleaning functional component includes sorbitol and / or sodium polycarboxylate.

[0007] Specifically, tartaric acid has multiple hydroxyl and carboxyl groups, which can form a multidentate coordination structure with tin ions. Sulfamic acid not only inhibits the hydrolysis of tin ions to form Sn(OH)2 by forming stable complexes such as Sn(HNSO3)2, but also has excellent pH buffering ability due to its weak acidity (pKa≈1.0). In the present invention, sulfamic acid and tartaric acid are used to complex tin ions synergistically to form stable complexes, effectively reducing the hydrolysis rate of tin salts, reducing the current edge effect, reducing the color difference (ΔE), improving the coloring uniformity, and is particularly suitable for deep color processes such as bronze and black, ensuring the long-term stability of the system. In addition, sulfamic acid has weak acidity (pKa≈1.0) and good pH buffering ability, reducing the amount of sulfuric acid used in the preparation of the bath and stabilizing the acidity of the entire coloring system.

[0008] Specifically, the main function of the antioxidant is to ensure that tin ions are not oxidized during long-term electrolysis, thereby preventing the formation of insoluble precipitates and ensuring the clarity and stability of the bath. For this purpose, in the present invention, an iron complex and hydrazine sulfate are used in combination to achieve synergistic effects; among them, the iron complex provides strong reduction protection and can cooperate with the complexing agent in the system of the present invention (for example, the amino group of sulfamic acid complexes with iron ions to form an iron sulfamate complex, which is purple-red, making the bath turn red, and the colored workpiece shows a unique color system of black with a red tint) to form stable metal complexes, further inhibiting the oxidation of tin ions; hydrazine sulfate can provide an additional reducing environment for the system under appropriate pH conditions. When used in combination with the iron complex, it can further improve the overall antioxidant capacity of the electrolytic coloring bath, avoiding the harm of traditional phenolic reducing agents to the human body and the environment.

[0009] Specifically, the main function of the stabilizer is to regulate the ionic strength and polarity of the solution, ensure the uniform dispersion of tin ions during the entire electrolysis process, thereby preventing the formation of local supersaturation and precipitation, and balancing the current distribution. In the present invention, a specific modified amino amide zinc phosphate is selected, which is a high molecular compound containing zinc ions and organic amine groups, and has good water solubility and the ability to regulate the ionic environment through chemical modification. In addition, the modified amino amide zinc phosphate can cooperate with other components in the system (such as ferrous sulfate, weakening the polarity of ferrous sulfate), further enhancing the overall stability of the system.

[0010] Specifically, the modified amino amide zinc phosphate of the present invention can be prepared by the following steps:

[0011] 1) Prepare a phosphoric acid amino amide complex solution: Mix an aqueous phosphoric acid solution with a mass concentration of 50% with ethanolamine, heat it to 50-60 °C while stirring, control the pH at 2.5-3.5, and react for 30 minutes to form a transparent or light yellow complex solution;

[0012] 2) Introduce a zinc source and carry out complexation precipitation: Slowly add zinc oxide to the complexing solution, control the temperature at 60 - 70 °C and the pH at 3.5 - 4.5, stir and react for 1 hour to form a stable zinc organophosphate complex system, which is milky white colloid or transparent liquid. After the reaction, cool to room temperature, filter to remove unreacted impurities, and spray dry to obtain the modified amino amide zinc phosphate solution;

[0013] Among them, the molar ratio of phosphoric acid, ethanolamine, and zinc oxide is 1:(1 - 1.5):1.

[0014] Specifically, in the present invention, by adding a self - cleaning functional component, during the downtime or under low - load conditions, the tiny precipitates generated in the bath solution can quickly aggregate, flocculate, and settle to the bottom, thereby achieving automatic self - cleaning and reducing the frequency of manual maintenance. During the downtime, through the solubilization and viscosity regulation of sorbitol, the tiny precipitates quickly aggregate into larger particles; sodium polycarboxylate then assists these particles to quickly flocculate and settle. After the self - cleaning process, the suspended solids in the bath solution are significantly reduced, ensuring that the solution remains clear and transparent before the next continuous electrolytic coloring, thus avoiding problems such as decreased electrolysis efficiency and uneven coloring caused by excessive precipitates. The automatic self - cleaning function significantly reduces the frequency and workload of manual cleaning of the bath solution, improves the continuity and stability of the overall production, and at the same time reduces the waste liquid treatment cost, meeting the requirements of green environmental protection.

[0015] In some embodiments of the present invention, by mass, the tin salt electrolytic coloring additive comprises 25 - 40 parts of a complexing agent, 30 - 40 parts of a conductive salt, 15 - 30 parts of an antioxidant, 5 - 10 parts of a surfactant, 1 - 2 parts of a stabilizer, and 3 - 5 parts of a self - cleaning functional component.

[0016] In some embodiments of the present invention, the conductive salt comprises at least one of magnesium sulfate, ferrous sulfate, and ammonium sulfate.

[0017] Specifically, the conductive salt mainly improves the conductivity of the bath solution and regulates the ion balance, and acts together with other components to effectively improve the problem of uneven current distribution during the electrolytic coloring process. The conductive salt can significantly increase the conductivity of the bath solution during electrolysis, reduce the phenomenon of too high or too low local current density, thereby ensuring uniform deposition of metal ions and meeting the requirement of coloring uniformity.

[0018] In some embodiments of the present invention, the surfactant comprises at least one of polyethylene glycol, glycerol, and sodium dodecylbenzenesulfonate.

[0019] Specifically, the emulsifying and solubilizing effects of surfactants can significantly improve the wetting effect on the workpiece surface, ensuring that the metal surface is clean and oil-free before electrolytic coloring, thereby improving the coloring quality. The lubricating effect of surfactants can prevent the hydrogen gas evolved from accumulating on the workpiece surface, avoiding pitting, pinholes, and film bursting phenomena caused by hydrogen interference, and ensuring that the coloring layer has a full, stable color and good appearance quality.

[0020] In some embodiments of the present invention, the iron complex includes ferrous sulfate and / or ammonium ferrous sulfate.

[0021] In some embodiments of the present invention, the mass ratio of sulfamic acid to tartaric acid is 1:(1 - 5), preferably 1:(1 - 2).

[0022] In some embodiments of the present invention, the mass ratio of the iron complex to hydrazine sulfate is (2 - 6):1, preferably (3 - 5):1.

[0023] In a second aspect of the present invention, there is provided a tin salt electrolytic coloring bath solution, which includes the tin salt electrolytic coloring additive described in the first aspect of the present invention.

[0024] In some embodiments of the present invention, the concentration of the tin salt electrolytic coloring additive is 45 - 55 g / L.

[0025] In some embodiments of the present invention, the tin salt electrolytic coloring bath solution further includes sulfuric acid and stannous sulfate.

[0026] In some embodiments of the present invention, the concentration of sulfuric acid is 15 - 23 g / L, and the concentration of stannous sulfate is 6 - 13 g / L. If mainly light colors are electrolytically colored, it is 6 - 8 g / L, and for dark colors to black, it is 8 - 13 g / L.

[0027] In some embodiments of the present invention, the tin salt electrolytic coloring bath solution further includes nickel sulfate, and the concentration of nickel sulfate is 18 - 25 g / L.

[0028] In some embodiments of the present invention, the process parameters for electrolytic coloring using the tin salt electrolytic coloring bath solution include: the coloring voltage is 16 - 20 V, and the coloring temperature is 18 - 23 °C.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The tin salt electrolytic coloring additive provided by the present invention synergistically complexes tin ions through sulfamic acid and tartaric acid to inhibit the hydrolysis of tin ions. The hydrolysis rate of the tin salt is stably lower than 1% / month, and the edge effect of the current is effectively reduced, improving the coloring uniformity. The color difference ΔE can be controlled within ≤1.0. By using an iron complex and hydrazine sulfate in combination, the overall antioxidant capacity of the system is enhanced, making it difficult for tin ions to be oxidized. The specific stabilizer modifies amino amide zinc phosphate to effectively prevent the formation of local supersaturation and precipitation. Through the self-cleaning functional component, small precipitates are quickly aggregated, flocculated, and settled during the shutdown period, ensuring that the electrolytic coloring bath solution remains clear, prolonging the service life of the electrolytic coloring bath solution, and significantly reducing the maintenance frequency. Detailed implementation manners

[0031] The content of the present invention will be further described in detail through specific embodiments below. The raw materials, reagents, or devices used in the embodiments can be obtained from conventional commercial channels or can be obtained by existing technical methods without special instructions. Unless otherwise specified, the test or measurement methods are conventional methods in the art.

[0032] Example 1

[0033] A tin salt electrolytic coloring additive includes the following components in parts by mass: 10 parts of sulfamic acid, 20 parts of L-tartaric acid, 15 parts of magnesium sulfate, 20 parts of ammonium sulfate, 16 parts of ferrous sulfate, 4 parts of hydrazine sulfate, 8 parts of polyethylene glycol, 2 parts of modified amino amide zinc phosphate, 2.5 parts of sorbitol, and 2.5 parts of sodium polycarboxylate.

[0034] An electrolytic coloring bath solution containing the above tin salt electrolytic coloring additive: 20 g / L of sulfuric acid, 50 g / L of tin salt electrolytic coloring additive, 8 g / L of stannous sulfate, and the balance is water. The coloring process parameters are: the coloring voltage is 18 V, and the coloring temperature is 20 °C.

[0035] Example 2

[0036] A tin salt electrolytic coloring additive includes the following components in parts by mass: 15 parts of sulfamic acid, 20 parts of L-tartaric acid, 15 parts of magnesium sulfate, 15 parts of ammonium sulfate, 20 parts of ferrous sulfate, 5 parts of hydrazine sulfate, 5 parts of polyethylene glycol, 1 part of modified amino amide zinc phosphate, 2 parts of sorbitol, and 2 parts of sodium polycarboxylate.

[0037] An electrolytic coloring bath solution containing the above tin salt electrolytic coloring additive: 15 g / L of sulfuric acid, 45 g / L of tin salt electrolytic coloring additive, 6 g / L of stannous sulfate, and the balance is water. The coloring process parameters are: the coloring voltage is 16 V, and the coloring temperature is 18 °C.

[0038] Example 3

[0039] A tin salt electrolytic coloring additive, comprising the following components in parts by mass: 20 parts of sulfamic acid, 20 parts of L-tartaric acid, 15 parts of magnesium sulfate, 20 parts of ammonium sulfate, 12 parts of ferrous sulfate, 3 parts of hydrazine sulfate, 5 parts of polyethylene glycol, 1 part of modified amino amide zinc phosphate, 2 parts of sorbitol, and 2 parts of sodium polycarboxylate.

[0040] An electrolytic coloring bath containing the above tin salt electrolytic coloring additive: 23 g / L of sulfuric acid, 55 g / L of tin salt electrolytic coloring additive, 13 g / L of stannous sulfate, and the balance is water. The coloring process parameters are: the coloring voltage is 20 V, and the coloring temperature is 23 °C.

[0041] Comparative Example 1 (without self-cleaning functional components)

[0042] A tin salt electrolytic coloring additive, comprising the following components in parts by mass: 10 parts of sulfamic acid, 20 parts of L-tartaric acid, 15 parts of magnesium sulfate, 20 parts of ammonium sulfate, 20 parts of ferrous sulfate, 5 parts of hydrazine sulfate, 8 parts of polyethylene glycol, and 2 parts of modified amino amide zinc phosphate.

[0043] An electrolytic coloring bath containing the above tin salt electrolytic coloring additive: 20 g / L of sulfuric acid, 50 g / L of tin salt electrolytic coloring additive, 8 g / L of stannous sulfate, and the balance is water. The coloring process parameters are: the coloring voltage is 18 V, and the coloring temperature is 20 °C.

[0044] Comparative Example 2 (without stabilizer)

[0045] A tin salt electrolytic coloring additive, comprising the following components in parts by mass: 10 parts of sulfamic acid, 20 parts of L-tartaric acid, 15 parts of magnesium sulfate, 20 parts of ammonium sulfate, 18 parts of ferrous sulfate, 4 parts of hydrazine sulfate, 8 parts of polyethylene glycol, 2.5 parts of sorbitol, and 2.5 parts of sodium polycarboxylate.

[0046] An electrolytic coloring bath containing the above tin salt electrolytic coloring additive: 20 g / L of sulfuric acid, 50 g / L of tin salt electrolytic coloring additive, 8 g / L of stannous sulfate, and the balance is water. The coloring process parameters are: the coloring voltage is 18 V, and the coloring temperature is 20 °C.

[0047] Comparative Example 3 (using a single L-tartaric acid as a complexing agent)

[0048] A tin salt electrolytic coloring additive, comprising the following components in parts by mass: 30 parts of L-tartaric acid, 15 parts of magnesium sulfate, 20 parts of ammonium sulfate, 16 parts of ferrous sulfate, 4 parts of hydrazine sulfate, 8 parts of polyethylene glycol, 2 parts of modified amino amide zinc phosphate, 2.5 parts of sorbitol, and 2.5 parts of sodium polycarboxylate.

[0049] An electrolytic coloring bath containing the above-mentioned tin salt electrolytic coloring additive: 20 g / L of sulfuric acid, 50 g / L of tin salt electrolytic coloring additive, 8 g / L of stannous sulfate, and the balance is water. The coloring process parameters are: the coloring voltage is 18 V, and the coloring temperature is 20 °C.

[0050] Comparative Example 4 (using a single hydrazine sulfate as an antioxidant)

[0051] A tin salt electrolytic coloring additive, comprising the following components in parts by mass: 10 parts of sulfamic acid, 20 parts of L-tartaric acid, 15 parts of magnesium sulfate, 20 parts of ammonium sulfate, 20 parts of hydrazine sulfate, 8 parts of polyethylene glycol, 2 parts of modified amino amide zinc phosphate, 2.5 parts of sorbitol, and 2.5 parts of sodium polycarboxylate.

[0052] An electrolytic coloring bath containing the above-mentioned tin salt electrolytic coloring additive: 20 g / L of sulfuric acid, 50 g / L of tin salt electrolytic coloring additive, 8 g / L of stannous sulfate, and the balance is water. The coloring process parameters are: the coloring voltage is 18 V, and the coloring temperature is 20 °C.

[0053] Performance test

[0054] Electrolytic coloring was carried out on an aluminum alloy sample with a conventional anodic oxidation film, and coloring was carried out according to the electrolytic coloring baths containing the tin salt electrolytic coloring additive provided in Examples 1-3 and Comparative Examples 1-4. The test results are shown in Table 1.

[0055] Table 1

[0056]

[0057]

[0058] As can be seen from Table 1:

[0059] 1) Clarity and stability of the bath

[0060] The bath of Example 1 is completely transparent and has extremely low residue, and the hydrolysis rate of the tin salt is stable at ≤1% / month, which proves that for the electrolytic coloring bath using the tin salt electrolytic coloring additive of the present invention, the synergistic effect of each component is obvious and the long-term stability of the system is excellent.

[0061] Due to the lack of self-cleaning functional components in Comparative Example 1, the precipitation is not easy to dissipate, resulting in obvious turbidity of the bath after long-term operation and a significant decrease in stability.

[0062] 2) Coloring uniformity and color difference

[0063] In Examples 1-3, the color difference ΔE≤1.0 is achieved and the coloring is uniform, indicating that the tin salt electrolytic coloring additive of the present invention can effectively improve the current distribution and reduce the difference between the electrodeposition regions.

[0064] In Comparative Example 2, due to the lack of a stabilizer, the local ion concentration was uneven, and obvious color differences (ΔE>2.0) occurred during the coloring process, affecting the coloring consistency of the product.

[0065] 3) Coloring rate and bath service life

[0066] The coloring rates of Examples 1-3 were fast and the colors were full. At the same time, the bath service life was extended (>6 months). This indicates that after improving the solubility and self-cleaning function of the entire system, the efficiency and continuity of the electrolytic coloring process have been significantly improved.

[0067] The coloring rates of Comparative Examples 1-4 decreased, and the bath service life was short, requiring frequent replacement or adjustment.

[0068] 4) Solubility and operation control

[0069] The tin salt electrolytic coloring additives of Examples 1-3 could be quickly and fully dissolved, had high transparency, and were convenient for operation control; while in Comparative Examples 1-2, due to the lack of key components, the solubility was poor, there were undissolved particles or flocculent precipitates, and frequent adjustments were required during the operation process, increasing the production difficulty and cost.

[0070] By comparing the examples with the comparative examples, Examples 1-3 of the present invention showed significant advantages in bath stability, coloring uniformity, solubility, self-cleaning function, and overall operation control, demonstrating the importance of the synergistic effect of the key components of the present invention and the superiority of the technical solution of the present invention. This provides a reliable, stable, and environmentally friendly solution for the high-quality electrolytic coloring of anodic oxidation films on aluminum and its alloys.

[0071] The preferred embodiments of the present invention have been specifically described above, but the present invention is not limited to the described embodiments. Those skilled in the art can also make various equivalent variations or substitutions without departing from the spirit of the present invention, and these equivalent variations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A tin salt electrolytic coloring additive, characterized in that, The tin salt electrolytic coloring additive includes a complexing agent, a conductive salt, an antioxidant, a surfactant, a stabilizer and a self-cleaning functional component. The complexing agent includes sulfamic acid and tartaric acid. The antioxidant includes an iron complex and hydrazine sulfate. The stabilizer includes modified amino amide zinc phosphate. The self-cleaning functional component includes sorbitol and / or sodium polycarboxylate.

2. The stannous salt electrolytic coloring additive according to claim 1, characterized in that, By mass, the tin salt electrolytic coloring additive includes 25-40 parts of a complexing agent, 30-40 parts of a conductive salt, 15-30 parts of an antioxidant, 5-10 parts of a surfactant, 1-2 parts of a stabilizer and 3-5 parts of a self-cleaning functional component.

3. The stannous salt electrolytic coloring additive according to claim 1, wherein The conductive salt includes at least one of magnesium sulfate, ferrous sulfate and ammonium sulfate.

4. The stannous salt electrolytic coloring additive according to claim 1, characterized in that, The surfactant includes at least one of polyethylene glycol, glycerol and sodium dodecylbenzenesulfonate.

5. The stannous salt electrolytic coloring additive according to claim 1, wherein The iron complex includes ferrous sulfate and / or ammonium ferrous sulfate.

6. The stannous salt electrolytic coloring additive according to claim 1, wherein The mass ratio of the sulfamic acid to the tartaric acid is 1:(1-5).

7. The stannous salt electrolytic coloring additive according to claim 1, characterized in that, The mass ratio of the iron complex to the hydrazine sulfate is (2-6):

1.

8. A tin salt electrolytic coloring bath solution, characterized in that, The tin salt electrolytic coloring bath includes the tin salt electrolytic coloring additive according to any one of claims 1-7.

9. The stannous salt electrolytic coloring bath solution according to claim 8, characterized in that, The concentration of the tin salt electrolytic coloring additive is 45-55 g / L.

10. The stannous salt electrolytic coloring bath solution according to claim 8, characterized in that, The tin salt electrolytic coloring bath further includes sulfuric acid and stannous sulfate.

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