Plate-temperature-resistant chromium-free passivation solution for batch hot galvanizing as well as preparation method and application of plate-temperature-resistant chromium-free passivation solution

Abstract

The invention discloses a plate temperature-resistant chromium-free passivation solution for batch hot galvanizing and a preparation method and application thereof, and the plate temperature-resistant chromium-free passivation solution comprises the following raw materials in parts by mass: 30-80 parts of 3-aminopropyltriethoxysilane, 1-10 parts of molybdate, 50-100 parts of phosphate, 5-15 parts of weak acid, 30-100 parts of a complexing agent, 1-20 parts of water-based resin, 0.1-10 parts of a pH regulator and 800-1000 parts of water. The plate-temperature-resistant chromium-free passivation solution disclosed by the invention can appear white rust after lasting for 72 hours under a neutral salt mist condition, and the corrosion resistance of the plate-temperature-resistant chromium-free passivation solution is improved by 1-2 times compared with that of most batch hot galvanizing chromium-free passivation solutions on the market; according to the plate-temperature-resistant chromium-free passivation solution, when the plate temperature is too high after water washing, the passivation solution can be rapidly solidified into a film through waste heat of the plate temperature, the passivation solution on the surface of a galvanized plate can be prevented from falling off from the surface when the temperature is low, the poor passivation effect is avoided, the production efficiency is improved, and oxidation of galvanized steel is reduced.

Description

Technical Field

[0001] The invention relates to a plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing and a preparation method and application thereof, belonging to the technical field of metal surface treatment. Background Art

[0002] In the field of metal surface treatment, especially in the passivation treatment of hot-dip galvanized parts, the traditional chromic acid passivation process once dominated. This technology significantly improves the corrosion resistance and decorativeness of the metal by forming a chromium-containing passivation film on the surface of the galvanized layer. However, with the enhancement of environmental awareness and strict regulations, the chromic acid passivation process has been gradually eliminated due to the heavy metal pollution it produces. In order to replace the chromic acid passivation process, chromium-free passivation technology came into being. The chromium-free passivation solution is mainly composed of a chromium-free film-forming agent, corrosion inhibitor, stabilizer and pH regulator, etc., which aims to form a dense passivation film on the metal surface through chemical reaction, thereby achieving the purpose of corrosion prevention. At present, there are many chromium-free passivation solution products on the market, which are widely used in metal surface treatment in the construction, automobile, home appliance and other industries. Although the existing chromium-free passivation technology has made significant progress in environmental protection, it still has shortcomings in high temperature stability, corrosion resistance, process adaptability, cost and environmental protection treatment. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the present invention provides a plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing and a preparation method and application thereof, which meet the high performance and environmental protection requirements of metal surface treatment.

[0004] In order to achieve the above-mentioned purpose, the present invention adopts a plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing, which includes the following raw materials, by mass: 30-80 parts of 3-aminopropyltriethoxysilane, 1-10 parts of molybdate, 50-100 parts of phosphate, 5-15 parts of weak acid, 30-100 parts of complexing agent, 1-20 parts of water-based resin, 0.1-10 parts of pH regulator, and 800-1000 parts of water.

[0005] As an improvement, the molybdate is any one of ammonium molybdate and sodium molybdate.

[0006] As an improvement, the phosphate is any one of sodium dihydrogen phosphate and sodium monohydrogen phosphate.

[0007] As an improvement, the weak acid is any one of glacial acetic acid, citric acid and phosphoric acid.

[0008] As an improvement, the complexing agent is any one of HEDP and EDTA.

[0009] As an improvement, the water-based resin is any one of water-soluble acrylic resin and water-soluble polyurethane.

[0010] As an improvement, the pH adjuster is ammonia water or acetic acid.

[0011] The second aspect of the present invention also provides a method for preparing the plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing, comprising the following steps: 1) hydrolyzing 3-aminopropyltriethoxysilane to prepare solution a; 2) After solution a is completely hydrolyzed, molybdate and phosphate are added to prepare solution b; 3) After solution b is completely clarified, add a weak acid to prepare solution c; 4) After solution c is completely dissolved, add a complexing agent to prepare solution d; 5) After solution d is completely dissolved, add water-based resin to prepare solution e; 6) After solution e is stabilized, a pH regulator is added to adjust the pH to 3-4 to prepare solution f, which is the plate temperature resistant chromium-free passivation solution after stabilization.

[0012] The third aspect of the present invention also provides an application of the plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing or the plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing obtained by the preparation method in batch hot-dip galvanizing, wherein the plate temperature resistant chromium-free passivation solution is added to the chromium-free passivation solution working solution at a mass percentage of 1%-1.5%.

[0013] Compared with the prior art, the plate temperature resistant chromium-free passivation liquid of the present invention can persist in the formation of white rust for 72 hours under neutral salt spray conditions, and its corrosion resistance is 1-2 times higher than that of most batch hot-dip galvanizing chromium-free passivation liquids on the market; the plate temperature resistant chromium-free passivation liquid of the present invention can use the residual heat of the plate temperature to quickly solidify the passivation liquid into a film when the plate temperature is too high after washing, and can prevent the passivation liquid on the surface of the galvanized plate from falling off the surface when the temperature is low, thereby avoiding poor passivation effect. The present invention improves production efficiency and reduces oxidation of galvanized steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a neutral salt spray test diagram of the steel plate surface after passivation with the plate temperature resistant chromium-free passivation solution of an embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to make the objectives, technical solutions and advantages of the present invention more clear, the technical solutions of the present application are described in detail below with the help of accompanying drawings and specific embodiments. It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical solutions of the present application, rather than limitations on the technical solutions of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0016] A method for preparing a plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing, comprising the following steps: 1) 3-aminopropyltriethoxysilane is subjected to a hydrolysis reaction until it is complete to obtain a solution a. This step ensures the effective activation of the silane molecules and lays the foundation for subsequent reactions; 2) After solution a is completely hydrolyzed, slowly add molybdate and phosphate, stir thoroughly until completely dissolved, and form solution b. This step is to introduce necessary metal ions and phosphate groups to enhance the corrosion resistance of the passivation film. 3) After solution b reaches a completely clear state, add weak acid and continue stirring until it is completely dissolved to obtain solution c. The addition of weak acid helps to adjust the pH of the system and promote the dissolution and reaction of subsequent components; 4) After solution c is dissolved, add a complexing agent and stir to ensure complete dissolution to obtain solution d. The function of the complexing agent is to stabilize the metal ions in the solution and prevent them from precipitating, while improving the uniformity and stability of the passivation solution; 5) After solution d is stable, continue to add water-based resin and stir thoroughly until the resin is completely dispersed in the solution to form solution e. The addition of water-based resin not only enhances the adhesion and flexibility of the passivation film, but also further improves the passivation effect; 6) After solution e forms a stable homogeneous system, the pH value of the solution is adjusted to 3-4 using a pH adjuster to obtain the final solution f. The control of this step is crucial to ensure the performance of the passivation solution. The optimization of the pH value can significantly improve the passivation efficiency and the corrosion resistance of the film layer.

[0017] The plate temperature resistant chromium-free passivation liquid prepared by the present invention can be easily added into a suitable solvent (such as water) at a mass percentage of 1%-1.5%, so as to easily prepare a high-efficiency and environmentally friendly chromium-free passivation working liquid to meet the needs of industrial production. Example 1

[0018] A method for preparing a plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing, comprising the following steps: 1) 30 g of 3-aminopropyltriethoxysilane was hydrolyzed in 1000 ml of water until completion to obtain solution a; 2) After solution a is completely hydrolyzed, slowly add 2g ammonium molybdate and 80g sodium dihydrogen phosphate, stir thoroughly until completely dissolved, to form solution b; 3) After solution b reaches a completely clear state, add 5 g of glacial acetic acid and continue stirring until it is completely dissolved to obtain solution c; 4) After solution c is dissolved, add 30 g EDTA and stir to ensure complete dissolution to obtain solution d; 5) After solution d is stable, continue to add 2g of water-soluble acrylic resin and stir thoroughly until the resin is completely dispersed in the solution to form solution e; 6) After solution e forms a stable homogeneous system, use 0.5-2 ml of ammonia water to adjust the pH value of the solution to 3 (a pH tester is required to test and add the solution at the same time) to obtain the final solution f, which is the plate temperature resistant chromium-free passivation solution.

[0019] The plate temperature resistant chromium-free passivation solution prepared in Example 1 was added to water at a mass percentage of 1%, and passivation experiments were carried out at plate temperatures of 30°C, 40°C, 50°C, and 60°C, respectively, with a passivation time of 30 s; the steel plate material used was Q355, with a specification of 50×80×5mm; The above four sample coatings were placed in a neutral salt spray chamber for salt spray testing at the same time. The test showed that white rust appeared on the surface of the 30℃ and 40℃ samples after 24 hours of salt spray, and the corrosion area was greater than 5%; white rust appeared on the surface of the 50℃ sample after 48 hours of salt spray, and the corrosion area was greater than 5%; white rust appeared on the surface of the 60℃ sample after 72 hours of salt spray, and the corrosion area was greater than 5%. The experimental results show that the plate temperature resistant chromium-free passivation liquid of the present invention has better inhibition of surface corrosion when the plate surface temperature is higher. Among them, Figure 1 The following is a graph showing the effects of sample coating at 0h, 24h and 48h at a plate temperature of 60°C.

[0020] At present, the temperature of the steel after galvanizing in the hot-dip galvanizing process is very high, and the surface temperature is generally maintained at about 50-70°C after water cooling, and the galvanized steel needs to be passivated after the temperature continues to drop in the air. The plate temperature resistant chromium-free passivation liquid of the present invention can reduce the air cooling step, keep the plate temperature at 60-80°C before passivation, and make the passivation liquid quickly solidify into a film on the surface of the galvanized plate, thereby improving the passivation efficiency, avoiding the damage of the passivation film due to weather or construction reasons after passivation, and reducing the oxidation of the galvanized steel in the air. Example 2

[0021] A method for preparing a plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing, comprising the following steps: 1) 50 g of 3-aminopropyltriethoxysilane was hydrolyzed in 1000 ml of water until completion to obtain solution a; 2) After solution a is completely hydrolyzed, slowly add 5g sodium molybdate and 90g sodium monohydrogen phosphate, stir thoroughly until completely dissolved, to form solution b; 3) After solution b reaches a completely clear state, add 10 g of citric acid and continue stirring until it is completely dissolved to obtain solution c; 4) After solution c is dissolved, add 50 g of HEDP and stir to ensure complete dissolution to obtain solution d; 5) After solution d is stable, continue to add 5g of water-soluble polyurethane and stir thoroughly until the polyurethane is completely dispersed in the solution to form solution e; 6) When solution e forms a stable homogeneous system, add 0.5-1.5 ml of ammonia water with a dropper to adjust the pH value of the solution to 3.5 to obtain the final solution f.

[0022] The plate temperature resistant chromium-free passivation solution prepared in Example 2 was added into water at a mass percentage of 1.2%, and then batch hot-dip galvanizing was performed. The steel plate material used was Q355 with a specification of 50×80×5 mm. Example 3

[0023] A method for preparing a plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing, comprising the following steps: 1) 80 g of 3-aminopropyltriethoxysilane was hydrolyzed in 1000 ml of water until completion to obtain solution a; 2) After solution a is completely hydrolyzed, slowly add 10g sodium molybdate and 100g sodium dihydrogen phosphate, stir thoroughly until completely dissolved, to form solution b; 3) After solution b reaches a completely clear state, add 15 g of phosphoric acid and continue stirring until it is completely dissolved to obtain solution c; 4) After solution c is dissolved, add 100 g EDTA and stir to ensure complete dissolution to obtain solution d; 5) After solution d is stable, continue to add 15g of water-soluble acrylic resin and stir thoroughly until the resin is completely dispersed in the solution to form solution e; 6) When solution e forms a stable homogeneous system, add 0.5-1.5 ml of ammonia water with a dropper to adjust the pH value of the solution to 4 to obtain the final solution f.

[0024] The plate temperature resistant chromium-free passivation solution prepared in Example 3 was added into water at a mass percentage of 1.5%, and then batch hot-dip galvanizing was performed. The steel plate material used was Q355 with a specification of 50×80×5 mm.

[0025] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

Claims

1. A plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing, characterized in that: The raw materials include the following by mass: 30-80 parts of 3-aminopropyltriethoxysilane, 1-10 parts of molybdate, 50-100 parts of phosphate, 5-15 parts of weak acid, 30-100 parts of complexing agent, 1-20 parts of water-based resin, 0.1-10 parts of pH regulator and 800-1000 parts of water.

2. The plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing according to claim 1, characterized in that: The molybdate is any one of ammonium molybdate and sodium molybdate.

3. The plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing according to claim 1, characterized in that: The phosphate is any one of sodium dihydrogen phosphate and sodium monohydrogen phosphate.

4. The plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing according to claim 1, characterized in that: The weak acid is any one of acetic acid, citric acid and phosphoric acid.

5. The plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing according to claim 1, characterized in that: The complexing agent is any one of HEDP and EDTA.

6. The plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing according to claim 1, characterized in that: The water-based resin is any one of water-soluble acrylic resin and water-soluble polyurethane.

7. The plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing according to claim 1, characterized in that: The pH regulator is ammonia water or acetic acid.

8. A method for preparing the plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) hydrolyzing 3-aminopropyltriethoxysilane to prepare solution a; 2) After solution a is completely hydrolyzed, molybdate and phosphate are added to prepare solution b; 3) After solution b is completely clarified, add a weak acid to prepare solution c; 4) After solution c is completely dissolved, add a complexing agent to prepare solution d; 5) After solution d is completely dissolved, add water-based resin to prepare solution e; 6) After solution e is stabilized, a pH regulator is added to adjust the pH to 3-4 to prepare solution f, which is the plate temperature resistant chromium-free passivation solution after stabilization.

9. Use of the plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing according to any one of claims 1 to 7 or the plate temperature resistant chromium-free passivation solution for batch hot-dip galvanizing obtained by the preparation method according to claim 8 in batch hot-dip galvanizing, characterized in that: Add the plate temperature resistant chromium-free passivation liquid into the chromium-free passivation liquid working solution at a mass percentage of 1%-1.5%.

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