Novel preparation method of Hopeite zinc phosphate conversion coating

Abstract

The invention discloses a novel preparation method of a Hopeite zinc phosphate conversion coating, and belongs to the technical field of steel phosphating. Comprising the following steps: 1, preparing zinc phosphate crystals from a phosphorus source and a zinc source; step 2, carrying out amorphization treatment on the zinc phosphate crystal to obtain amorphous zinc phosphate; and 3, coating the amorphous zinc phosphate on the surface of the steel sheet substrate, and carrying out crystal transformation and film preparation to obtain the zinc phosphate conversion film. The novel preparation method of the Hopeite zinc phosphate conversion coating has the beneficial effects that the cost is lower, and the preparation process is more environment-friendly.

Description

Technical Field

[0001] The present application relates to the technical field of steel phosphating, and in particular to a novel preparation method of Hopeite zinc phosphate conversion film. Background Art

[0002] Hopeite zinc phosphate conversion film is the most widely used steel phosphating technology in the world, and is often used in combination with electrophoresis technology in the automotive and other industrial fields. The current mature zinc phosphate conversion film preparation process is wet synthesis, that is, the workpiece is immersed in a solution containing phosphate, zinc ions and other substances to react and form a film. The wet synthesis can refer to a phosphating solution and phosphating method for preparing a high alkali-resistant phosphating film on the surface of a galvanized sheet disclosed in Chinese patent document CN115537790B.

[0003] However, there are the following shortcomings when using this process to prepare zinc phosphate conversion coating:

[0004] 1. A lot of waste sediment: During the preparation process, a large amount of wastewater containing phosphorus and zinc heavy metals and a large amount of solid waste will be generated, which will increase the processing cost and affect the quality of the conjunctiva.

[0005] 2. Serious waste: The bath liquid temperature is required to be high during preparation, which consumes a large amount of resources.

[0006] 3. High pollution: The waste sediment generated during the preparation is difficult to handle and highly polluting.

[0007] 4. High cost: This process has high requirements on equipment, is difficult to operate, has high maintenance and labor costs, and has high environmental costs, and is easily restricted by relevant environmental regulations.

[0008] Therefore, a new method for preparing Hopeite zinc phosphate conversion coating with lower cost and more environmentally friendly preparation process is needed. Summary of the invention

[0009] The content of this application is used to introduce concepts in a brief form, which will be described in detail in the detailed implementation section below. The content of this application is not intended to identify the key features or essential features of the technical solution claimed for protection, nor is it intended to limit the scope of the technical solution claimed for protection.

[0010] In order to solve the technical problems mentioned in the above background technology section, some embodiments of the present application provide a novel preparation method of Hopeite zinc phosphate conversion coating, comprising the following steps:

[0011] Step 1: Take a phosphorus source and a zinc source to prepare zinc phosphate crystals;

[0012] Step 2: amorphizing the zinc phosphate crystals to obtain amorphous zinc phosphate;

[0013] Step 3: coating amorphous zinc phosphate on the surface of the steel sheet substrate to perform crystal conversion and obtain a zinc phosphate conversion film.

[0014] Furthermore, in step 1, the process of preparing zinc phosphate crystals is as follows: dissolving a phosphorus source and a zinc source in distilled water respectively, mixing and stirring the phosphorus source solution and the zinc source solution, reacting to generate a zinc phosphate precipitate, and filtering the zinc phosphate precipitate to obtain zinc phosphate crystals.

[0015] Furthermore, in step 2, the process of amorphizing the zinc phosphate crystals is as follows: placing the zinc phosphate crystals in a ball mill, adding ethanol and grinding balls to the ball mill, and performing a primary ball milling treatment on the zinc phosphate crystals to obtain zinc phosphate powder; and performing a second ball milling treatment on the zinc phosphate powder to obtain amorphous zinc phosphate powder.

[0016] Furthermore, in step 3, the amorphous zinc phosphate powder is spread on the steel sheet substrate, distilled water is added, the amorphous zinc phosphate powder is evenly coated on the surface of the steel sheet substrate, a wetting agent mixed solution is added, and the steel sheet substrate with a zinc phosphate conversion film is obtained after drying.

[0017] Furthermore, the molar ratio of the phosphorus source to the zinc source is 1:1.

[0018] Furthermore, the stirring time is 0.5-1h.

[0019] Furthermore, agate grinding balls are used in the initial ball milling treatment; the rotation speed of the initial ball milling treatment is set to 500-700 r / min; and the time of the initial ball milling treatment is 1-6 hours.

[0020] Furthermore, the second ball milling treatment uses zirconium oxide grinding balls; the second ball milling treatment is set to a rotation speed of 900-1100 r / min; and the second ball milling treatment time is 20-26 hours.

[0021] Furthermore, the wetting agent mixed solution is a mixed solution of deionized distilled water and Tween-20 wetting agent.

[0022] Furthermore, the temperature of the wetting agent mixed solution is 60-80°C.

[0023] The beneficial effect of the present application is that it provides a new method for preparing Hopeite zinc phosphate conversion film with lower cost and more environmentally friendly preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting a part of this application are used to provide a further understanding of this application, so that other features, purposes and advantages of this application become more obvious. The illustrative embodiment drawings and their descriptions of this application are used to explain this application and do not constitute an improper limitation on this application.

[0025] In addition, throughout the drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and that the components and elements are not necessarily drawn to scale.

[0026] In the attached picture:

[0027] Figure 1 It is a schematic diagram of the overall process according to an embodiment of the present application;

[0028] Figure 2 is the Hopeite zinc phosphate conversion coating prepared in Example 1;

[0029] Figure 3 is the Hopeite zinc phosphate conversion coating prepared in Example 2;

[0030] Figure 4 is the Hopeite zinc phosphate conversion coating prepared in Example 3;

[0031] Figure 5 It is a Hopeite zinc phosphate conversion coating prepared by conventional wet synthesis. DETAILED DESCRIPTION

[0032] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure.

[0033] It should also be noted that, for ease of description, only the parts related to the invention are shown in the drawings. In the absence of conflict, the embodiments and features in the embodiments of the present disclosure can be combined with each other.

[0034] It should be noted that the concepts such as "first" and "second" mentioned in the present disclosure are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0035] It should be noted that the modifications of "one" and "plurality" mentioned in the present disclosure are illustrative rather than restrictive, and those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0036] The present disclosure will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0037] Example 1, a novel method for preparing Hopeite zinc phosphate conversion coating, referring to Figure 1 , including the following steps:

[0038] Step 1: Take 0.1791g sodium dihydrogen phosphate (NaH2PO4·12H2O) as a phosphorus source and 0.1487g zinc nitrate (Zn(NO3)2·6H2O) as a zinc source to prepare zinc phosphate crystals; in step 1, the process of preparing zinc phosphate crystals is as follows: dissolve the phosphorus source and zinc source in 25ml of distilled water respectively, mix the phosphorus source solution and the zinc source solution, add a stirrer and place it on a magnetic stirrer for stirring, react for 0.5-1h to generate zinc phosphate precipitate, and filter the zinc phosphate precipitate to obtain zinc phosphate crystals. The molar ratio of the phosphorus source to the zinc source is 1:1.

[0039] Step 2: amorphizing the zinc phosphate crystals to obtain amorphous zinc phosphate; in step 2, the process of amorphizing the zinc phosphate crystals is as follows: weigh 0.8g of zinc phosphate crystals and put them into a 50mL ball mill, add ethanol, 25 agate grinding balls with a diameter of 6mm, 6 agate grinding balls with a diameter of 8mm and 6 agate grinding balls with a diameter of 10mm into the ball mill, set the rotation speed to 600r / min, ball mill for 1h and 6h respectively, perform the initial ball milling treatment on the zinc phosphate crystals, and filter to obtain zinc phosphate powder; put the zinc phosphate powder into a 50mL ball mill, add 25ml of anhydrous ethanol, 100 zirconium oxide grinding balls with a diameter of 2mm and 50 zirconium oxide grinding balls with a diameter of 6mm into the ball mill, set the rotation speed to 1000r / min, ball mill for 24h, perform the second ball milling treatment on the zinc phosphate powder, and filter to obtain amorphous zinc phosphate powder.

[0040] Step 3: coating amorphous zinc phosphate on the surface of a steel sheet substrate, performing crystal conversion film formation, and obtaining a zinc phosphate conversion film; in step 3, taking 0.04 g of amorphous zinc phosphate powder and spreading it on a pre-treated steel sheet substrate, adding a small amount of distilled water, uniformly coating the amorphous zinc phosphate powder on the surface of the steel sheet substrate, adding a 70° C. wetting agent mixed solution, so that the surface coating of the amorphous zinc phosphate powder remains moist, and after drying, the following is obtained: Figure 2 The Hopeite zinc phosphate conversion coating shown is from Figure 2 It can be seen that the film is mainly composed of small grains of about 2-5 microns. Due to the unevenness, there are whitish areas. The film is complete and continuous as a whole, with high coverage and no exposed iron matrix.

[0041] Example 2, a novel method for preparing Hopeite zinc phosphate conversion coating, referring to Figure 1 , including the following steps:

[0042] Step 1: Take 0.1901g of trisodium phosphate (Na3PO4·12H2O) as a phosphorus source and 0.1487g of zinc nitrate (Zn(NO3)2·6H2O) as a zinc source to prepare zinc phosphate crystals; in step 1, the process of preparing zinc phosphate crystals is as follows: dissolve the phosphorus source and zinc source in 25ml of distilled water respectively, mix the phosphorus source solution and the zinc source solution, add a stirrer and place it on a magnetic stirrer for stirring, react for 0.5-1h to generate zinc phosphate precipitate, and filter the zinc phosphate precipitate to obtain zinc phosphate crystals. The molar ratio of the phosphorus source to the zinc source is 1:1.

[0043] Step 2: amorphize the zinc phosphate crystals to obtain amorphous zinc phosphate; in step 2, the process of amorphizing the zinc phosphate crystals is as follows: weigh 0.8g of zinc phosphate crystals and put them into a 50mL ball mill, add 25ml of anhydrous ethanol, 100 zirconium oxide grinding balls with a diameter of 2mm and 50 zirconium oxide grinding balls with a diameter of 6mm into the ball mill, set the speed to 1000r / min, and ball mill for 4h, 6h, 8h, 24h and 36h respectively, perform a single ball milling treatment on the zinc phosphate crystals, and obtain amorphous zinc phosphate powder after filtration.

[0044] Step 3: coating amorphous zinc phosphate on the surface of a steel sheet substrate, performing crystal conversion film formation, and obtaining a zinc phosphate conversion film; in step 3, taking 0.04 g of amorphous zinc phosphate powder and spreading it on a pre-treated steel sheet substrate, adding a small amount of distilled water, uniformly coating the amorphous zinc phosphate powder on the surface of the steel sheet substrate, adding a 70° C. wetting agent mixed solution, so that the surface coating of the amorphous zinc phosphate powder remains moist, and after drying, the following is obtained: Figure 3 The Hopeite zinc phosphate conversion coating shown is from Figure 3 It can be seen that the film is mainly composed of small grains of about 2-5 microns. The zinc phosphate conversion film prepared under the conditions of Example 2 has low continuity and has an exposed iron matrix.

[0045] Example 3, a novel method for preparing Hopeite zinc phosphate conversion coating, referring to Figure 1 , including the following steps:

[0046] Step 1: Take 0.1791g of disodium hydrogen phosphate (Na2HPO4·12H2O) as a phosphorus source and 0.1487g of zinc nitrate (Zn(NO3)2·6H2O) as a zinc source to prepare zinc phosphate crystals; in step 1, the process of preparing zinc phosphate crystals is as follows: dissolve the phosphorus source and zinc source in 25ml of distilled water respectively, mix the phosphorus source solution and the zinc source solution, add a stirrer and place on a magnetic stirrer for stirring, react for 0.5-1h to generate zinc phosphate precipitate, and filter the zinc phosphate precipitate to obtain zinc phosphate crystals. The molar ratio of the phosphorus source to the zinc source is 1:1.

[0047] Step 2: amorphizing the zinc phosphate crystals to obtain amorphous zinc phosphate; in step 2, the process of amorphizing the zinc phosphate crystals is as follows: weigh 0.8g of zinc phosphate crystals and put them into a 50mL ball mill, add 25ml of anhydrous ethanol, 25 agate grinding balls with a diameter of 6mm, 6 agate grinding balls with a diameter of 8mm, and 6 agate grinding balls with a diameter of 10mm to the ball mill, set the rotation speed to 600r / min, and ball mill for 1h and 6h respectively, perform initial ball milling on the zinc phosphate crystals, and obtain zinc phosphate powder after filtration; put the zinc phosphate powder into a 50mL ball mill, add 25ml of anhydrous ethanol, 100 zirconium oxide grinding balls with a diameter of 2mm, and 50 zirconium oxide grinding balls with a diameter of 6mm to the ball mill, set the rotation speed to 1000r / min, ball mill for 24h, perform a second ball milling on the zinc phosphate powder, and obtain amorphous zinc phosphate powder after filtration.

[0048] Step 3: coating amorphous zinc phosphate on the surface of a steel sheet substrate, performing crystal conversion film formation, and obtaining a zinc phosphate conversion film; in step 3, taking 0.04 g of amorphous zinc phosphate powder and spreading it on a pre-treated steel sheet substrate, adding a small amount of distilled water, uniformly coating the amorphous zinc phosphate powder on the surface of the steel sheet substrate, adding a 70° C. wetting agent mixed solution, so that the surface coating of the amorphous zinc phosphate powder remains moist, and after drying, the following is obtained: Figure 4 The Hopeite zinc phosphate conversion coating shown is from Figure 4 It can be seen that the film is mainly composed of small grains of about 2-5 microns. Compared with the Hopeite zinc phosphate conversion film of Example 2, the continuity of the conversion film is improved and the film coverage is increased. However, compared with the Hopeite zinc phosphate conversion film of Example 1, the continuity and film coverage are still insufficient.

[0049] Comparative Example: Hopeite zinc phosphate conversion film prepared by conventional wet synthesis Figure 5 As shown, the film is a zinc phosphate conversion film prepared by immersion in a conventional 75°C aqueous solution in the literature (Corrosion Science, 2015, 94, 428-437). Figure 5 It can be seen that the film layer is also composed of grains of about 5 microns, and the film layer is continuous but not dense. It can be seen that in terms of film quality, the Hopeite zinc phosphate conversion film prepared by the method of the present application is complete and continuous, with high coverage; in terms of production cost and environmental protection, the method of the present application has the advantages of lower cost and more environmentally friendly preparation process.

[0050] In summary, the method of the present application prepares Hopeite zinc phosphate conversion film, and directly uses water-assisted solid-phase crystallization reaction to prepare zinc phosphate conversion film, avoiding the process of preparing complex phosphating solution, and only needs two chemical raw materials, and the method of the present application has low requirements for equipment, simple operation, and low maintenance and labor costs; when the method of the present application prepares Hopeite zinc phosphate conversion film, no complex waste liquid is generated, and no large amount of solid phosphating residue is generated, which greatly reduces the cost of environmental governance; at the same time, the method of the present application has lower temperature requirements, lower energy consumption, and is more environmentally friendly; because the method of the present application does not generate a large amount of solid phosphating waste residue, the influence of the outside world on the growth of the zinc phosphate conversion film is reduced, so that the conversion rate of the zinc phosphate conversion film is higher and the quality is better; the method of the present application has a stable production environment, simple and easy operation and control, less environmental pollution, and safer and more reliable production.

[0051] The above descriptions are only some preferred embodiments of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in the embodiments of the present disclosure (but not limited to) and the technical solutions formed.

Claims

1. A novel method for preparing Hopeite zinc phosphate conversion coating, characterized in that: The following steps are involved: Step 1: Take a phosphorus source and a zinc source to prepare zinc phosphate crystals; Step 2: amorphizing the zinc phosphate crystals to obtain amorphous zinc phosphate; Step 3: coating amorphous zinc phosphate on the surface of the steel sheet substrate to perform crystal conversion and obtain a zinc phosphate conversion film.

2. The novel method for preparing the Hopeite zinc phosphate conversion coating according to claim 1, characterized in that: In step 1, the process of preparing zinc phosphate crystals is as follows: a phosphorus source and a zinc source are respectively dissolved in distilled water, the phosphorus source solution and the zinc source solution are mixed and stirred to react to generate zinc phosphate precipitate, and the zinc phosphate precipitate is filtered to obtain zinc phosphate crystals.

3. The novel method for preparing Hopeite zinc phosphate conversion coating according to claim 2, characterized in that: In step 2, the process of amorphizing the zinc phosphate crystals is as follows: placing the zinc phosphate crystals in a ball mill, adding ethanol and grinding balls to the ball mill, and performing a primary ball milling treatment on the zinc phosphate crystals to obtain zinc phosphate powder; and performing a second ball milling treatment on the zinc phosphate powder to obtain amorphous zinc phosphate powder.

4. The novel method for preparing the Hopeite zinc phosphate conversion coating according to claim 3, characterized in that: In step 3, the amorphous zinc phosphate powder is spread on the steel sheet substrate, distilled water is added, the amorphous zinc phosphate powder is evenly coated on the surface of the steel sheet substrate, a wetting agent mixed solution is added, and the steel sheet substrate with a zinc phosphate conversion film is obtained after drying.

5. The novel method for preparing Hopeite zinc phosphate conversion coating according to claim 2, characterized in that: The molar ratio of the phosphorus source to the zinc source is 1:

1.

6. The novel method for preparing the Hopeite zinc phosphate conversion coating according to claim 2, characterized in that: The stirring time is 0.5-1h.

7. The novel method for preparing Hopeite zinc phosphate conversion coating according to claim 3, characterized in that: The initial ball milling process uses agate grinding balls; the initial ball milling process is set at a rotation speed of 500-700r / min; and the initial ball milling process lasts for 1-6h.

8. The novel method for preparing Hopeite zinc phosphate conversion coating according to claim 3, characterized in that: The second ball milling process uses zirconium oxide grinding balls; the second ball milling process is set to have a rotation speed of 900-1100 r / min; and the second ball milling process lasts for 20-26 hours.

9. The novel method for preparing Hopeite zinc phosphate conversion coating according to claim 4, characterized in that: The wetting agent mixed solution is a mixed solution of deionized distilled water and Tween-20 wetting agent.

10. The novel method for preparing Hopeite zinc phosphate conversion coating according to claim 4, characterized in that: The temperature of the wetting agent mixed solution is 60-80°C.

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