Method for rapidly evaluating appearance of electrophoretic coating

Abstract

The invention relates to a method for rapidly evaluating the appearance of an electrophoretic coating, which measures the appearance of the electrophoretic coating by dip-coating varnish on the surface of the electrophoretic coating to be measured, and specifically comprises a pretreatment step, a coating step and an evaluation step. According to the method, the thickness of the varnish layer dip-coated on the electrophoresis layer is controlled by adjusting the viscosity of the varnish and controlling the vertical leveling time, so that the effect of measuring the appearance is achieved. Compared with a traditional spraying process, the method is simpler, the cost is saved, meanwhile, the conditions that the orange peel of the plate surface is serious, data measurement is not facilitated and the like due to the fact that the coating film thickness is reduced in the spraying process are avoided, meanwhile, compared with a composite coating, a single coating is less in interference factor, and the data accuracy is higher.

Description

Technical Field

[0001] This invention relates to the field of automotive coating technology, and more specifically to a method for rapidly evaluating the appearance of electrophoretic coatings. Background Technology

[0002] As the automotive market continues to expand, the requirements for passenger vehicle coatings are also constantly increasing, demanding both high corrosion resistance and high aesthetic appeal. For example, ordinary sedan coatings are required to prevent perforation corrosion for more than 10 years and also possess characteristics such as high gloss and vibrant colors.

[0003] In existing technologies, electrophoretic coatings play a crucial role in improving corrosion resistance. However, since coating films are usually composed of multiple layers, the surface quality of the electrophoretic coating also affects the appearance quality of the intermediate coat and topcoat. Compared to the evaluation of topcoat quality, the evaluation of the surface quality of electrophoretic coatings lacks indicators and control methods, and it has not received sufficient attention and process monitoring. In production, the short-wave orange peel problem of the entire vehicle topcoat often occurs due to poor electrophoretic surface quality. There is an urgent need to introduce quantitative evaluation methods to objectively and quantitatively characterize the quality of electrophoretic coatings.

[0004] Currently, roughness and orange peel texture are commonly used as evaluation indicators for electrophoretic paint film quality. However, extensive experimental verification has shown that the level of roughness is not necessarily positively correlated with the overall vehicle appearance; rather, it is subject to chance. Low roughness may result in a poor overall vehicle appearance, while high roughness may result in a better overall appearance. Roughness alone is insufficient to reflect the overall appearance of the coating. Furthermore, due to the low gloss of a single electrophoretic coating, an orange peel texture analyzer cannot accurately measure the electrophoretic appearance. Conventional evaluation of electrophoretic appearance requires applying a color varnish or clear varnish during the electrophoretic layer spraying, followed by evaluation using an orange peel texture analyzer. This method is time-consuming, consumes a large amount of paint, and is subject to numerous interfering factors during the spraying process, affecting the accuracy of the data.

[0005] In view of this, there is an urgent need in the field to develop a method for rapidly evaluating the appearance of electrophoretic coatings in order to solve the problems existing in the prior art. Summary of the Invention

[0006] Based on the above facts, the purpose of this invention is to provide a method for rapidly evaluating the appearance of electrophoretic coatings. This method measures the appearance of the electrophoretic coating by dipping it into a clear varnish layer. The thickness of the clear varnish layer on the electrophoretic coating is controlled by adjusting the viscosity of the clear varnish and controlling the vertical leveling time, thereby achieving the desired appearance measurement. This method is simple, convenient, and fast, providing high data accuracy while also saving costs.

[0007] A first aspect of the present invention provides a method for rapidly evaluating the appearance of an electrophoretic coating, comprising the following steps:

[0008] S1: Preprocessing steps;

[0009] S2: Painting steps;

[0010] S3: Evaluation steps.

[0011] In some embodiments of the present invention, the pretreatment steps include, but are not limited to, pretreatment of the plate with the electrophoretic coating to be tested, pretreatment of the construction environment, and preparation of the coating; preferably, the pretreatment of the plate with the electrophoretic coating to be tested includes wiping the surface and edges of the plate with an alcohol solution; more preferably, the pretreatment of the plate with the electrophoretic coating to be tested involves wiping the edges of the plate surface multiple times in one direction with lint-free paper soaked in alcohol solution, and then wiping the surface of the plate surface multiple times in one direction; the pretreatment of the construction environment includes treating the construction environment to a dust-free environment; the preparation of the coating includes sampling the varnish according to the GB / T 3186-2006 standard method and diluting the varnish with an oil-based solvent to reduce the viscosity of the varnish; more preferably, before diluting the varnish with an oil-based solvent in the preparation of the coating, the varnish is further filtered with a clean filter cloth.

[0012] In some preferred embodiments of the present invention, the alcohol solution is ethanol or isopropanol.

[0013] In some preferred embodiments of the present invention, the construction environment temperature is 20℃-24℃; more preferably, the construction environment temperature is 21-23℃.

[0014] In some preferred embodiments of the present invention, when diluting the varnish with an oil-based solvent during the coating preparation, a T-4 cup is used to measure the viscosity of the varnish, and the viscosity of the varnish is controlled at 8-12s; more preferably, the viscosity of the varnish is controlled at 10s.

[0015] In some preferred embodiments of the present invention, the oily solvent is ethyl acetate or butyl acetate.

[0016] In some embodiments of the present invention, the coating step includes, but is not limited to, using a dip coating method, in which a clear varnish is dipped onto the surface of the electrophoretic coating to be tested after pretreatment in step S1; preferably, the coating step also includes a vertical leveling step, and in practice, the coating thickness can be ultimately controlled by controlling the vertical leveling time.

[0017] In some preferred embodiments of the present invention, the immersion time in the coating step is 20-22s, and the vertical leveling time is controlled between 0-60s.

[0018] In some preferred embodiments of the present invention, the final coating thickness is controlled to be 2-5 μm in the coating step.

[0019] In some preferred embodiments of the present invention, after coating the pretreated board by dip coating in the coating step, a baking step is also included. If the coating step includes a vertical leveling step, the baking step is performed after the vertical leveling step. The baking environment is a dust-free environment. More preferably, in the baking step, the board is placed at a horizontal angle, the baking temperature is 130-145℃, and the baking time is 15-20 minutes.

[0020] In some embodiments of the present invention, the evaluation steps include, but are not limited to, measuring the appearance of the varnish layer with an orange peel meter. The larger the short-wave value obtained by the orange peel meter, the worse the appearance of the electrophoretic coating.

[0021] Beneficial effects of the present invention

[0022] This invention addresses the shortcomings of existing technologies by providing a rapid method for evaluating the appearance of electrophoretic coatings. The method involves immersing the surface of the electrophoretic coating under test with a clear varnish to measure its appearance. The method controls the thickness of the clear varnish layer by adjusting the varnish viscosity and controlling the vertical leveling time, thereby achieving the desired appearance measurement. Compared to the traditional 3C1B spraying process, this method is simpler, saves costs, and avoids the severe orange peel effect on the board surface caused by reduced coating thickness during spraying, which is detrimental to measurement data. Furthermore, single-coat coatings are less susceptible to interference factors than composite coatings, resulting in higher data accuracy. Detailed Implementation

[0023] To more clearly illustrate the present invention, specific embodiments are described below. Those skilled in the art should understand that the following description is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0024] Fabrication of plates with electrophoretic coatings to be tested

[0025] Four plates with the electrophoretic coating to be tested were prepared using two electrophoresis apparatuses, A and B, respectively, and denoted as electrophoresis A1-A4 and electrophoresis B1-B4. The roughness of electrophoresis A1-A4 and electrophoresis B1-B4 was measured and recorded. It should be noted that, in order to ensure the consistency of the plates and reduce experimental errors, the obtained electrophoresis A1-A4 and B1-B4 were each cut in half in the implementation method. One half was used for dip coating in the example, and the other half was used for conventional 3C1B coating in the comparative example. Therefore, the plates used in Example 1 and Comparative Example 1 were both electrophoresis A1 and electrophoresis B1, and the same applies to Examples 2-4 and Comparative Examples 2-4.

[0026] Example 1: Evaluation of the appearance of electrophoretic coating 1

[0027] S1: Preprocessing steps:

[0028] (1) Pretreatment of the board: Use lint-free paper containing ethanol or isopropanol to wipe the edge of the board surface of the electrophoresis A1 and electrophoresis B1 in one direction multiple times, and then wipe the surface of the board surface in one direction multiple times.

[0029] (2) Construction environment pretreatment: The construction environment is treated to be a dust-free environment, and the ambient temperature is maintained at 20-24℃;

[0030] (3) Coating preparation: In accordance with the requirements of GB / T 3186-2006, 1860-X varnish was selected as the sample, filtered with a clean filter cloth, and an appropriate amount of ethyl acetate or butyl acetate was added to control the viscosity of the varnish at 10s.

[0031] S2: Coating steps: Immerse the electrophoretic plates A1 and B1 treated in step S1 in the diluted clear varnish for 20 seconds. Then lift the electrophoretic plates out of the liquid and level them vertically for 60 seconds. Finally, place them horizontally in a clean oven and bake at 140℃ for 20 minutes.

[0032] S3: Evaluation steps: Use an orange peel meter to measure the appearance of the coating and record the shortwave value.

[0033] Comparative Example 1: Standard Evaluation Test 1

[0034] Electrophoretic coating A1 and electrophoretic coating B1 were applied using the 3C1B coating method. The appearance of the coating was then measured using an orange peel analyzer, and the short-wavelength values ​​were recorded.

[0035] Examples 2-4: Repeat the steps of Example 1 to evaluate the appearance of the electrophoretic coatings for electrophoresis A2-4 and electrophoresis B2-4.

[0036] Comparative Examples 2-4: Repeat the steps of Comparative Example 1 to evaluate the appearance of the electrophoretic coatings for electrophoresis A2-4 and electrophoresis B2-4.

[0037] The test results of Examples 1-4 and Comparative Examples 1-4 are shown in Table 1. The higher the shortwave value, the worse the appearance of the electrophoretic coating.

[0038] Table 1 Test Results

[0039]

[0040] As shown in Table 1, even with consistent electrophoretic roughness, the overall vehicle appearance can vary significantly. Therefore, a single roughness level cannot accurately reflect the appearance. Furthermore, the short wavelength trend of the 3C1B coating is similar to that of the dip coating described in this invention, and the appearance of the electrophoretic coating can be determined by measuring the short wavelength value.

[0041] The coating thickness was measured using a film thickness gauge. The required construction time and coating amount for Examples 1-4 and Comparative Examples 1-4 are shown in Table 2 below.

[0042] Table 2 Construction Time and Coating Consumption Table

[0043] Painting method Coating equipment Construction time Paint usage Coating thickness Comparative Example (3C1B) robot 120min 3000g 70-80μm Example (Dipping Coating) none 25min 500g 2-5μm

[0044] As can be seen from the results in Table 1-2, the evaluation method described in this invention is simple, fast, and accurate, and can save on paint.

[0045] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for rapidly evaluating the appearance of an electrophoretic coating, characterized in that, The appearance of an electrophoretic coating is measured by dipping a varnish onto the surface of the coating to be tested, including the following steps: S1: Pretreatment steps; the pretreatment steps include, but are not limited to, pretreatment of the plate with the electrophoretic coating to be tested, pretreatment of the construction environment, and preparation of the coating; S2: Coating step; The coating step includes, but is not limited to, using dip coating, in which a clear varnish is dipped onto the surface of the electrophoretic coating to be tested after pretreatment in step S1, and the dip coating time is preferably 20-22s; S3: Evaluation steps; the evaluation steps include, but are not limited to, measuring the appearance of the clear coat with an orange peel meter; the larger the short-wave value obtained by the orange peel meter, the worse the appearance of the electrophoretic coating.

2. The method for rapidly evaluating the appearance of an electrophoretic coating according to claim 1, characterized in that, The pretreatment of the plate with the electrophoretic coating to be tested includes wiping the surface and edges of the plate with an alcohol solution; the pretreatment of the construction environment includes treating the construction environment to a dust-free environment; the coating preparation includes sampling the varnish using a standard method and diluting the varnish with an oil-based solvent to reduce the viscosity of the varnish; preferably, before diluting the varnish with an oil-based solvent in the coating preparation, the varnish is filtered with a clean filter cloth.

3. The method for rapidly evaluating the appearance of an electrophoretic coating according to claim 2, characterized in that, The alcohol solution is ethanol or isopropanol. The pretreatment of the plate with the electrophoretic coating to be tested is preferably to wipe the edge of the plate surface multiple times in one direction with lint-free paper soaked in alcohol solution, and then wipe the plate surface multiple times in one direction. The construction environment temperature is 20℃-24℃. Preferably, the construction environment temperature is 21-23℃.

4. The method for rapidly evaluating the appearance of an electrophoretic coating according to claim 2, characterized in that, The viscosity of the diluted varnish is preferably 8-12s; more preferably, the viscosity of the diluted varnish is 10s.

5. The method for rapidly evaluating the appearance of an electrophoretic coating according to claim 2, characterized in that, The oily solvent is ethyl acetate or butyl acetate.

6. The method for rapidly evaluating the appearance of an electrophoretic coating according to any one of claims 1-5, characterized in that, The coating process includes a vertical leveling step after dipping in varnish to control the coating thickness.

7. The method for rapidly evaluating the appearance of an electrophoretic coating according to claim 6, characterized in that, The vertical leveling time is controlled between 0 and 60 seconds; the coating thickness is preferably 2-5 μm.

8. The method for rapidly evaluating the appearance of an electrophoretic coating according to any one of claims 1-5, characterized in that, In the coating step, after dipping a clear varnish onto the surface of the electrophoretic coating to be tested using a dip-coating method, a baking step is also included, wherein the baking environment is a dust-free environment.

9. The method for rapidly evaluating the appearance of an electrophoretic coating according to claim 8, characterized in that, In the baking step, the board is placed at a horizontal angle, the baking temperature is 130-145℃, and the baking time is 15-20 minutes.

10. The method for rapidly evaluating the appearance of an electrophoretic coating according to any one of claims 1-5, characterized in that, The coating process includes a vertical leveling step and a baking step after the varnish dip coating to control the coating thickness. The baking step is performed after the vertical leveling step. Preferably, the vertical leveling time is controlled between 0 and 60 seconds. The coating thickness is preferably 2-5 μm. In the baking step, the board is placed at a horizontal angle, the baking temperature is 130-145℃, and the baking time is 15-20 minutes.

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