Preparation method of matte color coating

Abstract

The zinc-iron alloy electroplating process is applied to electroplating processing production of the alloy with the matte color appearance. Compared with a common alkaline zinc-iron alloy electroplating process, the matte color appears on the surface of the plating layer, the matte color alloy coating is more decorative and attractive, the corrosion resistance of the plating layer is improved, and the service life is longer. Besides, according to the content of iron in the zinc-iron alloy, the content of iron in a plating layer is changed by changing the content of iron salt in the plating solution and the type of a complexing agent, and iron ions in the plating solution can be stably coordinated by adding organic acid ascorbic acid and malic acid in the plating solution and are prevented from precipitating or forming insoluble substances; the preparation method of the low-iron-content alloy matte color plating layer is provided, the decoration performance is improved, more excellent corrosion resistance is achieved, and the production process is green and environmentally friendly.

Description

Technical Field

[0001] The invention relates to the field of metal surface treatment, in particular to a method for preparing a matte color coating. Background Art

[0002] In the field of steel protective electroplating, the amount of zinc plating is large and the surface is wide. It has become a consensus that the protective performance of a single metal lock layer is not as good as that of an alloy coating. At present, the single metal zinc coating has developed into a zinc alloy coating, such as Zn-Fe, Zn-Ni, Zn-Co, etc. Among them, Zn-Fe alloy has two acid and alkali systems. According to the mass fraction of iron in the coating, there are two processes with high iron content and low iron content. 0.3%~1% is a low iron process, and 3%~25% is a high iron process. The former is more widely used than the latter. The corrosion resistance of the zinc-iron alloy coating is 5-20 times that of the pure zinc layer, and the hardness is 110-130HV. It is also widely used in hardware in the automotive, home appliance and construction industries.

[0003] Matt zinc-iron alloy raw materials have good high temperature resistance and excellent mechanical properties. Its low gloss gives people a soft texture and non-glaring visual effect. This raw material not only has excellent impact resistance, but also has excellent weather resistance and corrosion resistance, so that the products can still maintain good performance under harsh environmental conditions. In industry, it is widely used as a material in the automotive field, office equipment such as printers, and electrical and electronic fields such as home appliances and mobile phones.

[0004] In the preparation method of the related low-iron zinc-iron alloy coating, the invention patent application number CN202010545064 is an alkaline electroplating zinc-iron alloy plating bath additive for low-iron coating and its application. The first point is that this invention mainly discusses the alkaline electroplating zinc-iron alloy plating bath additive for low-iron coating and its application. The plating bath additive of this invention patent is composed of 50-80% heterocyclic organic amine and 20-50% solvent, wherein the heterocyclic organic amine is one or more of pyrazine, piperazine, pyridine, pyrimidine or pyrrole. The present invention mainly discusses a method for preparing a matte color coating, the main purpose of which is to obtain a matte color coating with decorative and aesthetic features and high corrosion resistance, and the additive of the present invention is relatively simple, the complexing agent malic acid and the like are commonly used complexing agents, and the plating bath additive used is a commonly used brightener. Secondly, the present invention mainly obtains a matte color coating with excellent corrosion resistance, coating performance, spot welding performance, wear resistance, low hydrogen embrittlement and thermal stability, which is widely used in the fields of automobiles, construction, home appliances, etc., and can absorb light and reduce reflection, thereby presenting a soft luster and delicate touch, and can also improve the performance of the coating to a certain extent. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a technical solution, a method for preparing a matte color coating, which improves the corrosion resistance of the coating and adopts a zinc-iron alloy low iron content process, so that the matte color alloy is more decorative and aesthetic. The complexing agent can form a complex with the metal ions, stably cooperate with Fe²⁺ and Fe³⁺, and can strongly complex Zn²⁺ to improve the chemical properties of the metal ions in the aqueous solution, which helps to maintain the stable ratio of iron and zinc in the zinc-iron alloy coating, and ensure the uniformity and consistency of the coating. Malic acid has reducing properties, which can prevent Fe 2+ Oxidation, its special molecular structure can interact with metal ions at the molecular level, thereby improving or changing the chemical and physical properties of metal ions. The present invention provides the following technical solutions: a method for preparing a matte color coating, characterized in that the electroplating process includes: pickling, degreasing, two water washings, electroplating, two water washings, polishing, two water washings, and water sealing; the plating solution formula is: ZnO 13g / L, NaOH 120g / L, ascorbic acid 16g / L, plating solution additive 8ml / L, FeCl21.6g / L, plating solution complexing agent 8-20g / L; the electroplating process conditions are as follows: pH value is 14, temperature 25°C, electroplating time 10min; The plating solution preparation process is as follows: S1. Pour the calculated amount of NaOH into beaker a, add water and stir to fully dissolve it; S2. Pour the calculated amount of ZnO into beaker b, add water and stir to fully dissolve it; S3, add the solution in beaker b into beaker a; S4. Pour the calculated amount of FeCl2 into beaker c, add water and stir to fully dissolve it; S5. Pour the calculated amount of ascorbic acid into beaker d, add water and stir to fully dissolve it; S6. Add the solution in beaker d into beaker c; S7, pour the calculated amount of plating solution complexing agent into beaker e, add water and stir to fully dissolve it; S8, add the solution in beaker e into beaker c; S9, add the solution in beaker c into beaker a; S10, pouring the calculated amount of plating solution additive into beaker a; Add the calculated amount of water to make up to volume, stir for 5 minutes, and let stand for 7 minutes.

[0006] Preferably, the plating solution additives are commonly used brighteners BH-336 and DPE-III. A small amount of plating solution brightener can facilitate and better obtain a matte color coating.

[0007] Preferably, the plating solution complexing agent is a commonly used complexing agent malic acid, potassium sodium tartrate, tetraethylenepentamine, triethanolamine, and EDTA. The present invention changes the iron content in the coating by changing the type of complexing agent in the plating solution. Five commonly used complexing agents are implemented. When the complexing agent used is malic acid, malic acid can stably coordinate the iron ions in the plating solution and prevent them from precipitating or forming insoluble substances. The iron content of the obtained coating is 0.597%, which is a low iron content. The coating color is matte, and the obtained coating thickness is 4.26um, which is the highest and has the best corrosion resistance.

[0008] Preferably, ascorbic acid can be used as a reducing agent during the electroplating process to inhibit the oxidation of Fe²⁺ in the plating solution, thereby maintaining the stability of the plating solution, preventing the oxidation and precipitation of metal ions, thereby extending the service life of the plating solution and improving the corrosion resistance of the coating.

[0009] Compared with the prior art, the present invention has the following benefit effects: a 4 μm thick zinc-iron alloy matte color alloy coating is obtained only by bare plating, which is not only decorative and aesthetically pleasing but also has increased corrosion resistance of the coating and a longer service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a scanning electron microscope morphology image of the obtained coating at 5,000 times magnification; Figure 2 This is a scanning electron microscope morphology image of the obtained coating at 10,000 times; Figure 3 This is a scanning electron microscope morphology image of the obtained coating at 30,000 times. DETAILED DESCRIPTION

[0011] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0012] The present invention provides a technical solution: A method for preparing a matte color coating, characterized in that the electroplating process comprises: pickling, degreasing, two water washings, electroplating, two water washings, polishing, two water washings, and water sealing; the plating solution formula is: ZnO 13g / L, NaOH 120g / L, ascorbic acid 16g / L, plating solution additive 8ml / L, FeCl21.6g / L, plating solution complexing agent 8-20g / L; the electroplating process conditions are as follows: pH value is 14, temperature is 25°C, and electroplating time is 10min; The plating solution preparation process is as follows: S1. Pour the calculated amount of NaOH into beaker a, add water and stir to fully dissolve it; S2. Pour the calculated amount of ZnO into beaker b, add water and stir to fully dissolve it; S3, add the solution in beaker b into beaker a; S4. Pour the calculated amount of FeCl2 into beaker c, add water and stir to fully dissolve it; S5. Pour the calculated amount of ascorbic acid into beaker d, add water and stir to fully dissolve it; S6. Add the solution in beaker d into beaker c; S7, pour the calculated amount of plating solution complexing agent into beaker e, add water and stir to fully dissolve it; S8, add the solution in beaker e into beaker c; S9, add the solution in beaker c into beaker a; S10, pouring the calculated amount of plating solution additive into beaker a; Add the calculated amount of water to make up to volume, stir for 5 minutes, and let stand for 7 minutes. Example 1

[0013] a 45 mm × 40 mm × 2 mm annealed low carbon steel was used as the cathode, the flat sample was activated with 15% dilute hydrochloric acid, and the zinc sheet was used as the anode; b. Polish the electrode and rinse the sample with deionized water; c. Pour 30 g of NaOH into beaker 1, add water and stir to fully dissolve it; d. Pour 3.25 g ZnO into beaker 2, add water and stir to fully dissolve it; e. Add the solution in beaker 2 into beaker 1; f. Pour 0.4 g of FeCl2 into beaker 3, add water and stir to fully dissolve it; g Pour 4 g of ascorbic acid into beaker 4, add water and stir to fully dissolve; h Add the solution in beaker 4 into beaker 3; i Pour 3 g of tetraethylenepentamine into beaker 5, add water and stir to fully dissolve it; j. Add the solution in beaker 5 into beaker 3; k Add the solution in beaker 3 into beaker 1; l Pour 2 ml of plating solution additive into beaker 1, add water to make up to 250 ml, stir for 5 minutes, and let stand for 7 minutes; m. DC electroplating was performed at a temperature of 28°C, using a cathode current density of 3.7A / dm², and the electroplating time was 10 minutes; Rinse the sample with deionized water and dry it with a hair dryer. Example 2

[0014] a 45 mm × 40 mm × 2 mm annealed low carbon steel was used as the cathode, the flat sample was activated with 15% dilute hydrochloric acid, and the zinc sheet was used as the anode; b. Polish the electrode and rinse the sample with deionized water; c. Pour 30 g of NaOH into beaker 1, add water and stir to fully dissolve it; d. Pour 3.25 g ZnO into beaker 2, add water and stir to fully dissolve it; e. Add the solution in beaker 2 into beaker 1; f. Pour 0.4 g of FeCl2 into beaker 3, add water and stir to fully dissolve it; g Pour 4 g of ascorbic acid into beaker 4, add water and stir to fully dissolve; h Add the solution in beaker 4 into beaker 3; i Pour 4.5 g of sodium potassium tartrate into beaker 5, add water and stir to fully dissolve; j. Add the solution in beaker 5 into beaker 3; k Add the solution in beaker 3 into beaker 1; l Pour 2 ml of plating solution additive into beaker 1, add water to make up to 250 ml, stir for 5 minutes, and let stand for 7 minutes; m. DC electroplating was performed at a temperature of 28°C, using a cathode current density of 3.7A / dm², and the electroplating time was 10 minutes; Rinse the sample with deionized water and dry it with a hair dryer. Example 3

[0015] a 45 mm × 40 mm × 2 mm annealed low carbon steel was used as the cathode, the flat sample was activated with 15% dilute hydrochloric acid, and the zinc sheet was used as the anode; b. Polish the electrode and rinse the sample with deionized water; c. Pour 30 g of NaOH into beaker 1, add water and stir to fully dissolve it; d. Pour 3.25 g ZnO into beaker 2, add water and stir to fully dissolve it; e. Add the solution in beaker 2 into beaker 1; f. Pour 0.4 g of FeCl2 into beaker 3, add water and stir to fully dissolve it; g Pour 4 g of ascorbic acid into beaker 4, add water and stir to fully dissolve; h Add the solution in beaker 4 into beaker 3; i Pour 2.4 g of triethanolamine into beaker 5, add water and stir to fully dissolve it; j. Add the solution in beaker 5 into beaker 3; k Add the solution in beaker 3 into beaker 1; l Pour 2 ml of plating solution additive into beaker 1, add water to make up to 250 ml, stir for 5 minutes, and let stand for 7 minutes; m. At a temperature of 28°C, a cathode current density of 3.7A / dm² was used for DC electroplating, and the electroplating time was 10 minutes; Rinse the sample with deionized water and dry it with a hair dryer. Example 4

[0016] a 45 mm × 40 mm × 2 mm annealed low-carbon steel was used as the cathode, the flat sample was activated with 15% dilute hydrochloric acid, and the zinc sheet was used as the anode; b. Polish the electrode and rinse the sample with deionized water; c. Pour 30g of NaOH into beaker 1, add water and stir to fully dissolve it; d. Pour 3.25 g ZnO into beaker 2, add water and stir to fully dissolve it; e. Add the solution in beaker 2 into beaker 1; f. Pour 0.4 g of FeCl2 into beaker 3, add water and stir to fully dissolve it; g Pour 4 g of ascorbic acid into beaker 4, add water and stir to fully dissolve; h Add the solution in beaker 4 into beaker 3; i Pour 2.1 g of malic acid into beaker 5, add water and stir to fully dissolve; j. Add the solution in beaker 5 into beaker 3; k Add the solution in beaker 3 into beaker 1; l Pour 2 ml of plating solution additive into beaker 1, add water to make up to 250 ml, stir for 5 minutes, and let stand for 7 minutes; m. At a temperature of 28°C, a cathode current density of 3.7A / dm² was used for DC electroplating, and the electroplating time was 10 minutes; n Rinse the sample with deionized water and then dry it with a hair dryer; The surface morphology of the sample obtained in Example 4 was observed using a scanning electron microscope. Figure 1 , Figure 2 and Figure 3 shown. Example 5

[0017] a 45 mm × 40 mm × 2 mm annealed low-carbon steel was used as the cathode, the flat sample was activated with 15% dilute hydrochloric acid, and the zinc sheet was used as the anode; b. Polish the electrode and rinse the sample with deionized water; c. Pour 30g of NaOH into beaker 1, add water and stir to fully dissolve it; d. Pour 3.25 g ZnO into beaker 2, add water and stir to fully dissolve it; e. Add the solution in beaker 2 into beaker 1; f. Pour 0.4 g of FeCl2 into beaker 3, add water and stir to fully dissolve it; g Pour 4 g of ascorbic acid into beaker 4, add water and stir to fully dissolve; h Add the solution in beaker 4 into beaker 3; i Pour 2 g of EDTA into beaker 5, add water and stir to fully dissolve it; j. Add the solution in beaker 5 into beaker 3; k Add the solution in beaker 3 into beaker 1; l Pour 2 ml of plating solution additive into beaker 1, add water to make up to 250 ml, stir for 5 minutes, and let stand for 7 minutes; m. At a temperature of 28°C, a cathode current density of 3.7A / dm² was used for DC electroplating, and the electroplating time was 10 minutes; Rinse the sample with deionized water and dry it with a hair dryer.

[0018] The thickness and iron content of the material were tested using an X-ray thickness gauge. The measurement results are shown in Table 1. The iron content of the malic acid complexing agent is 0.597%, which is low iron, and it has the highest thickness and good corrosion resistance.

Claims

1. A method for preparing a matte color coating, characterized in that: The electroplating process includes: pickling, degreasing, two water washings, electroplating, two water washings, polishing, two water washings, and water sealing; the plating solution formula is: ZnO 13g / L, NaOH 120g / L, ascorbic acid 16g / L, plating solution additive 8ml / L, FeCl21.6g / L, plating solution complexing agent 8-20g / L; the electroplating process conditions are as follows: pH value is 14, temperature is 25℃, and electroplating time is 10min; The plating solution preparation process is as follows: S1. Pour the calculated amount of NaOH into beaker a, add water and stir to fully dissolve it; S2. Pour the calculated amount of ZnO into beaker b, add water and stir to fully dissolve it; S3, add the solution in beaker b into beaker a; S4. Pour the calculated amount of FeCl2 into beaker c, add water and stir to fully dissolve it; S5. Pour the calculated amount of ascorbic acid into beaker d, add water and stir to fully dissolve it; S6. Add the solution in beaker d into beaker c; S7, pour the calculated amount of plating solution complexing agent into beaker e, add water and stir to fully dissolve it; S8, add the solution in beaker e into beaker c; S9, the solution in beaker c is added to beaker a; S10, pouring the calculated amount of plating solution additive into beaker a; Add the calculated amount of water to make up to volume, stir for 5 minutes, and let stand for 7 minutes.

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