Electrophoresis test method for inner cavity of automobile body

Abstract

The invention discloses an automobile body inner cavity electrophoresis test method which comprises the following steps: S1, manufacturing a test device which comprises a first pretreatment steel plate and a second pretreatment steel plate; s2, putting the test device into an electrophoresis tank, enabling the first pretreatment steel plate to be opposite to an anode electrode in the electrophoresis tank, and then carrying out an electrophoresis test; s3, the second pretreatment steel plate is taken out, and a circulating salt spray test is conducted; s4, treating after the test; s5, removing corrosives on the surface of the second pretreatment steel plate; and S6, measuring the height of a paint film on the surface of the second pretreatment steel plate. According to the electrophoresis test method for the inner cavity of the automobile body, the inner cavity anti-corrosion condition can be visually evaluated by using the inner cavity upper film sample plate to carry out the circulating salt mist experiment, circulating salt mist is introduced into the normal-temperature, normal-humidity, high-temperature and high-humidity environment compared with neutral salt mist, the circulating salt mist is closer to the atmospheric environment use condition, and it is ensured that the inner film electrophoresis anti-corrosion condition can be correctly evaluated.

Description

Technical Field

[0001] This invention belongs to the field of automotive technology. Specifically, this invention relates to a method for electrophoresis testing of the interior cavity of an automotive body. Background Technology

[0002] The quality of the electrophoretic coating in the inner cavity of the car body is particularly important for the corrosion protection of the car body. The film thickness and the corrosion resistance of the paint film directly affect the corrosion protection capability of the inner cavity of the car body electrophoretic coating. Therefore, the control of the inner cavity electrophoretic film formation is especially important.

[0003] Existing technologies mostly use electrophoresis samples with fixed film thickness to conduct neutral salt spray tests. Fixed film thickness cannot directly reflect the condition of the film on the inner cavity of the car body, and the correlation between neutral salt spray and actual corrosion is low, so it cannot accurately evaluate the corrosion protection of the inner film electrophoresis.

[0004] The aim is to provide an improved method for electrophoretic testing of automotive body cavities, particularly regarding how to conveniently measure the ability of electrophoretic cavities to form films and to intuitively assess the corrosion resistance of the films after coating. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a method for electrophoretic coating testing of automotive body cavities, with the purpose of ensuring convenient measurement of the film-forming ability of the electrophoretic cavity and intuitive evaluation of the corrosion resistance after film application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: an electrophoresis test method for the inner cavity of an automobile body, comprising the following steps:

[0007] S1. Fabricate a test apparatus, which includes a first pretreatment steel plate and a second pretreatment steel plate;

[0008] S2. Place the test apparatus into the electrophoresis tank, with the first pretreatment steel plate facing the anode electrode in the electrophoresis tank, and then perform the electrophoresis test.

[0009] S3. Remove the second pre-treated steel plate and conduct a cyclic salt spray test;

[0010] S4. Post-test processing;

[0011] S5. Remove corrosion from the surface of the steel plate after the second pretreatment.

[0012] S6. Measure the height of the paint film on the surface of the second pre-treatment steel plate.

[0013] The electrophoresis tank contains a pre-treated electrophoresis solution. The test device is placed in the electrophoresis solution, and the distance between the bottom edge of the test device and the bottom of the electrophoresis tank is 45±5mm.

[0014] The distance between the test device and the anode electrode is 150±2mm.

[0015] The testing apparatus also includes adhesive strips disposed between the first pretreatment steel plate and the second pretreatment steel plate, with multiple adhesive strips disposed thereon.

[0016] The adhesive strip is made of polyvinyl chloride.

[0017] The first pretreatment steel plate and the second pretreatment steel plate are fixedly connected by tape.

[0018] Step S3 includes:

[0019] S301. Conduct a neutral salt spray test;

[0020] S302, Cooling;

[0021] S303, Place in a constant temperature and humidity environment for a set time.

[0022] In step S301, the neutral salt spray test is conducted for 3 to 5 hours, the salt solution concentration is 45 to 55 g / L, the pH value is 6.5 to 7.2, and the test temperature is 30 to 40°C.

[0023] In step S302, the cooling temperature is set to 18–28°C and the relative humidity is set to 40–60%.

[0024] In step S303, the temperature is set to 40±3℃, the relative humidity is set to 100%, and the set time is 16h.

[0025] The electrophoretic coating test method for automotive body cavities of the present invention can directly evaluate the corrosion protection of the cavity by using the inner membrane sample to carry out a cyclic salt spray test. The cyclic salt spray introduces a normal temperature and humidity environment and a high temperature and high humidity environment compared with the neutral salt spray, which is closer to the atmospheric environment and ensures that the electrophoretic corrosion protection of the inner membrane can be accurately evaluated. Attached Figure Description

[0026] This manual includes the following figures, which illustrate the following:

[0027] Figure 1 This is a flowchart of the electrophoresis test method for the inner cavity of an automobile body according to the present invention;

[0028] Figure 2 This is a schematic diagram of the location of the experimental setup;

[0029] Figure 3 This is a cross-sectional view of the experimental setup;

[0030] The diagram is marked as follows:

[0031] 1. Anode electrode; 2. Cathode electrode; 3. Test apparatus. Detailed Implementation

[0032] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solutions of the present invention, and to facilitate its implementation.

[0033] It should be noted that in the following embodiments, the terms "first" and "second" do not represent an absolute distinction in structure and / or function, nor do they represent the order of execution, but are merely for the convenience of description.

[0034] like Figure 1 As shown, the present invention provides a method for electrophoresis testing of the interior cavity of an automobile body, comprising the following steps:

[0035] S1. Fabricate a test apparatus, which includes a first pretreatment steel plate and a second pretreatment steel plate;

[0036] S2. Place the test apparatus into the electrophoresis tank, with the first pretreatment steel plate facing the anode electrode in the electrophoresis tank, and then perform the electrophoresis test.

[0037] S3. Remove the second pre-treated steel plate and conduct a cyclic salt spray test;

[0038] S4. Post-test processing;

[0039] S5. Remove corrosion from the surface of the steel plate after the second pretreatment.

[0040] S6. Measure the height of the paint film on the surface of the second pre-treatment steel plate.

[0041] Specifically, in this invention, a specially structured test device is used to simulate the internal cavity structure of a car body, such as the upper side beam of the A-pillar and small gap cavities of the B-pillar; laboratory electrophoresis and rectified electrophoresis are carried out on the device; a cyclic salt spray experiment is conducted and evaluated under specific conditions and for a specific time period; the evaluation is expressed by quantitatively representing the degree of blistering or corrosion.

[0042] In step S1 above, the first pretreatment steel plate and the second pretreatment steel plate are two steel plates made of steel. The first pretreatment steel plate and the second pretreatment steel plate are the same size. The length of the first pretreatment steel plate and the second pretreatment steel plate is 350mm, the width is 105mm, and the thickness is 0.8mm. When fabricating the experimental setup, a 15mm wide adhesive tape was used to seal the two long sides and the lower short side of the first and second pretreatment steel plates. Specifically, the first tape was used to bond the two long sides (350mm section) of the first and second pretreatment steel plates together, sealing the gap between them. A second tape was used to bond the bottom short side (105mm section) of the first and second pretreatment steel plates together, sealing the gap between them. The top short sides of the first and second pretreatment steel plates were not bonded, leaving a gap between their tops to ensure that the electrophoresis bath solution could enter between them during subsequent experiments.

[0043] Preferably, the testing apparatus also includes multiple adhesive strips disposed between the first and second pretreatment steel plates, with a certain distance between adjacent strips. The adhesive strips are made of polyvinyl chloride (PVC), which has stable chemical properties. It can resist acid and alkali corrosion and salt erosion, maintaining the stability of its physical and chemical properties. This ensures that the gap between the first and second pretreatment steel plates meets the testing requirements, facilitates film formation on the surfaces of the first and second pretreatment steel plates, and ensures sufficient film thickness, thus contributing to the accuracy of the test results.

[0044] The adhesive strip is 350mm long, 10mm wide, and 1-10mm thick. It is sandwiched between the first and second pretreatment steel plates, separating them. The strip's length is the same as that of both plates, and its two ends are aligned with the lengths of both plates, with the strip's length direction parallel to that of both plates.

[0045] In step S1 above, when making the test device, the first pretreatment steel plate and the second pretreatment steel plate are fixedly connected by a third tape. The first pretreatment steel plate and the second pretreatment steel plate are bound together by the third tape. The two pretreatment steel plates are aligned and fixed in this way, which helps to ensure the accuracy of the test results.

[0046] In this embodiment, two adhesive strips are provided.

[0047] like Figure 2 As shown, in step S2 above, the electrophoresis tank contains a pre-treated electrophoresis solution. The test device is placed in the electrophoresis solution, with the first and second pretreatment steel plates in a vertical position. The test device is positioned between the anode and cathode electrodes, with the first pretreatment steel plate facing the anode electrode and the second pretreatment steel plate facing the cathode electrode. The distance between the bottom edge of the test device and the bottom of the electrophoresis tank is 45±5 mm, the distance between the test device and the anode electrode is 150±2 mm, and the liquid level in the electrophoresis tank is 320±5 mm. This setup helps ensure the accuracy of the test results.

[0048] In step S2 above, the voltage or anode electrode is adjusted so that the electrophoretic film thickness on the front side of the first pretreatment steel plate (i.e. the surface of the first pretreatment steel plate facing the anode electrode) reaches 18±1μm. This thickness of the first pretreatment steel plate is comparable to the film thickness of the outer body panel of the electrophoretic line, which can ensure that the film thickness of the second pretreatment steel plate is closer to the film thickness of the inner cavity of the body, thus helping to ensure the accuracy of the test results.

[0049] Step S3 above includes:

[0050] S301. Conduct a neutral salt spray test;

[0051] S302, Cooling;

[0052] S303, Place in a constant temperature and humidity environment for a set time.

[0053] In step S301 above, a paint film is formed on the surface of the second pretreated steel plate. After separating the first and second pretreated steel plates, a neutral salt spray test is performed on the second pretreated steel plate. The neutral salt spray test time is set to 3-5 hours, exemplarily 4 hours; the salt solution concentration is set to 45-55 g / L, exemplarily 50 g / L; the pH value is 6.5-7.2; the test temperature is 30-40℃, exemplarily 35℃; the sedimentation rate is 1.5 ± 0.5 ml / (80 cm²·h); the test surface of the second pretreated steel plate faces upwards, forming an angle of 15-30° with the vertical. This setting can reduce abnormal accumulation of salt spray on the sample surface, making the experimental phenomena more stable and reliable.

[0054] In step S302 above, the cooling temperature is set to 18–28°C and the relative humidity is set to 40–60%. Under these conditions, the second pre-treated steel plate is placed under cooling conditions for 4 hours. This setting helps to ensure the accuracy of the test results.

[0055] In step S303 above, the temperature is set to 40±3℃ and the relative humidity is set to 100%. Under these constant temperature and humidity conditions, the storage time for the second pre-treatment steel plate is set to 16 hours. This setting helps to ensure the accuracy of the test results.

[0056] Step S3 can be performed multiple times, for example, 22 to 25 times. Currently, the salt spray test intensity results in a bare steel plate corrosion rate of 70 micrometers per 7 cycles, with 22 to 25 cycles. This is estimated to assess the rust condition of the external cavities of the vehicle body over approximately 8 years, a setting that aligns well with current passenger vehicle corrosion protection requirements.

[0057] In step S4 above, after the test is completed, the second pre-treated steel plate is taken out and naturally dried at room temperature for 1 hour. Then, the surface of the second pre-treated steel plate is lightly brushed with running clean water at a temperature not higher than 40°C to remove the residual salt solution on the surface of the second pre-treated steel plate. Finally, the second pre-treated steel plate is dried.

[0058] In step S5 above, the second pre-treatment steel plate is rinsed clean and air-dried indoors for 1 hour. The scratches on the paint film of the second pre-treatment steel plate are completely covered with tape, and the tape is flattened and compacted to ensure that there are no air bubbles and good contact between the tape and the paint film on the second pre-treatment steel plate. Then the tape is quickly peeled off (peeling angle is 60°), and the maximum value of the bilateral corrosion width at the scratches is recorded.

[0059] In step S6 above, the height of the paint film on the surface of the second pretreated steel plate without blistering or rust is measured after the test to evaluate the film-forming ability of the cavity.

[0060] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method for electrophoresis testing of the interior cavity of an automobile body, characterized in that, Including the following steps: S1. Fabricate a test apparatus, which includes a first pretreatment steel plate and a second pretreatment steel plate; S2. Place the test apparatus into the electrophoresis tank, with the first pretreatment steel plate facing the anode electrode in the electrophoresis tank, and then perform the electrophoresis test. S3. Remove the second pre-treated steel plate and conduct a cyclic salt spray test; S4. Post-test processing; S5. Remove corrosion from the surface of the steel plate after the second pretreatment. S6. Measure the height of the paint film on the surface of the second pre-treatment steel plate.

2. The method for electrophoresis testing of the inner cavity of an automobile body according to claim 1, characterized in that, The electrophoresis tank contains a pre-treated electrophoresis solution. The test device is placed in the electrophoresis solution, and the distance between the bottom edge of the test device and the bottom of the electrophoresis tank is 45±5mm.

3. The method for electrophoresis testing of the inner cavity of an automobile body according to claim 1, characterized in that, The distance between the test device and the anode electrode is 150±2mm.

4. The method for electrophoresis testing of automotive body cavities according to any one of claims 1 to 3, characterized in that, The testing apparatus also includes adhesive strips disposed between the first pretreatment steel plate and the second pretreatment steel plate, with multiple adhesive strips disposed thereon.

5. The method for electrophoresis testing of the inner cavity of an automobile body according to claim 4, characterized in that, The adhesive strip is made of polyvinyl chloride.

6. The method for electrophoresis testing of automotive body cavities according to any one of claims 1 to 5, characterized in that, The first pretreatment steel plate and the second pretreatment steel plate are fixedly connected by tape.

7. The method for electrophoresis testing of automotive body cavities according to any one of claims 1 to 5, characterized in that, Step S3 includes: S301. Conduct a neutral salt spray test; S302, Cooling; S303, Place in a constant temperature and humidity environment for a set time.

8. The method for electrophoresis testing of the inner cavity of an automobile body according to claim 7, characterized in that, In step S301, the neutral salt spray test is conducted for 3 to 5 hours, the salt solution concentration is 45 to 55 g / L, the pH value is 6.5 to 7.2, and the test temperature is 30 to 40°C.

9. The method for electrophoresis testing of the inner cavity of an automobile body according to claim 7, characterized in that, In step S302, the cooling temperature is set to 18–28°C and the relative humidity is set to 40–60%.

10. The method for electrophoresis testing of the inner cavity of an automobile body according to claim 7, characterized in that, In step S303, the temperature is set to 40±3℃, the relative humidity is set to 100%, and the set time is 16h.

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