Galvanized sheet rapid coating system for simulating coating process and method thereof

Abstract

The invention belongs to the technical field of galvanized sheet coating, and particularly relates to a galvanized sheet rapid coating system for simulating a coating process and a method thereof. The system comprises a spraying device, a spraying device and a heating device, the spraying device is used for respectively spraying a degreasing agent, a surface conditioning agent and a phosphating solution on the to-be-detected galvanized sheet, so that the to-be-detected galvanized sheet is sequentially subjected to degreasing, surface conditioning and phosphating treatment; the spraying device is used for carrying out electrostatic spraying treatment on the to-be-detected galvanized plate subjected to phosphating treatment; and the heating device is used for heating and curing the to-be-detected galvanized sheet after electrostatic spraying treatment. The coating system simulates a coating test for evaluation, the detection and evaluation period of the coating performance of the galvanized sheet is greatly shortened, and therefore efficient and accurate coating performance detection and evaluation of the galvanized sheet continuously produced by a galvanizing line can be completed.

Description

Technical Field

[0001] The invention belongs to the technical field of galvanized sheet coating, and in particular relates to a galvanized sheet rapid coating system and method for simulating a coating process. Background Art

[0002] Galvanized steel sheet is coated with zinc layer on the surface of the steel sheet to prevent corrosion and extend its service life. The steel sheet with zinc layer on the surface is called galvanized sheet. It is generally widely used in construction, home appliances, vehicles and ships, container manufacturing, electromechanical industry, etc. It is an important steel anti-corrosion sheet. With the development of industry, users have higher and higher requirements for the surface performance of galvanized sheet. High-end home appliances and other manufacturing industries often paint galvanized sheet materials during processing. Therefore, coating performance has become an important process indicator of galvanized sheet. The prior art "CN110252630A" proposes a thin plate hot-dip galvanized resin powder coating production line and its production process. The coating production line removes the coating after galvanizing. Before coating, the coating film must be removed by phosphating. The reeling and unwinding of the two lines are changed from 2 sets to 1 set each. The original two production lines are merged into one production line, which solves the shortcomings of the two production lines in the prior art, such as large area occupation, high energy consumption, high production cost and environmental protection.

[0003] From the perspective of the existing technology, for newly trial-produced galvanized products, it is necessary to take samples on site and mail them to users. The users then process the galvanized sheets into parts and arrange for batch coating on the on-site coating line. Finally, the batch of products is evaluated to see if they are qualified. The entire evaluation cycle is about one week. If the batch of galvanized sheets is found to be unqualified after the evaluation cycle, all the galvanized sheets processed into parts will be scrapped. This wastes resources and takes time. Summary of the invention

[0004] The purpose of the present invention is to address the problem that the galvanized sheet in the prior art needs to be processed into parts within a long evaluation cycle, and then the parts are coated and evaluated, resulting in a waste of resources and time, thereby proposing a galvanized sheet rapid coating system and method that simulates the coating process. The coating system of the present invention integrates degreasing, cleaning, surface conditioning and phosphating in one device, and a solution tank is set in the device, which is used to hold the solutions required for degreasing, cleaning, surface conditioning and phosphating, and a nozzle is opened on the side wall of the device, and a hanging component is set on the top of the device. During use, the galvanized sheet is placed in the device using the hanging component, and the nozzle is located at the same level as the top area of ​​the galvanized sheet so that the nozzle sprays the surface of the galvanized sheet. The system also includes a powder spraying device, which uses electrostatic spraying to spray powder on the surface of the galvanized sheet. The coating system of the present invention is used to simulate the coating test for evaluation, which greatly shortens the detection and evaluation cycle of the coating performance of the galvanized sheet, so that the efficient and accurate coating performance detection and evaluation of the galvanized sheet continuously produced by the galvanizing line can be completed.

[0005] The first aspect of the present invention proposes a galvanized sheet rapid coating system that simulates a coating process, the system comprising a spraying device, a spraying device and a heating device; the spraying device is used to spray a degreasing agent, a surface conditioning agent and a phosphating solution on the galvanized sheet to be tested respectively, so that the galvanized sheet to be tested is degreased, surface conditioned and phosphated in sequence; the spraying device is used to electrostatically spray the galvanized sheet to be tested after the phosphating treatment; the heating device is used to heat and solidify the galvanized sheet to be tested after the electrostatic spraying treatment.

[0006] Preferably, a solution tank is installed inside the spray device, and the solution tank is used to hold a degreaser, a surface conditioner and a phosphating solution respectively. A hanging component is provided on the top of the spray device, and the hanging component is used to place the galvanized sheet to be tested in the spray device. The side wall of the spray device is provided with a nozzle opening inward, and the top area of ​​the galvanized sheet to be tested is located at the same level as the nozzle. When in use, the solution tanks containing the degreaser, the surface conditioner and the phosphating solution are respectively connected to the nozzle, and the degreaser, the surface conditioner and the phosphating solution are sprayed on the galvanized sheet to be tested in turn using the nozzle.

[0007] Preferably, nozzles opening inwards are symmetrically arranged on the side walls of the spray device.

[0008] Preferably, a hanging component is installed on the top of the spraying device, and the hanging component is used to place the galvanized sheet to be tested after phosphating treatment in the spraying device. The spraying device is installed with an electrostatic spray gun, and the electrostatic spray gun is used to electrostatically spray the galvanized sheet to be tested after phosphating treatment.

[0009] The second aspect of the present invention provides a method for rapid coating of galvanized sheet using a simulated coating process implemented by the above-mentioned system, the method comprising the following steps:

[0010] Punching one end of the galvanized sheet to be tested, and hanging the punched end in the spraying device, spraying the degreasing agent, the surface conditioning agent and the phosphating solution on the galvanized sheet to be tested respectively, so that the galvanized sheet to be tested is degreased, surface conditioned and phosphated in sequence;

[0011] The galvanized sheet to be tested after being sprayed with the phosphating solution is hung in the spraying device, and the galvanized sheet to be tested is subjected to powder spraying treatment by using an electrostatic spray gun in the spraying device;

[0012] The galvanized sheet to be tested which has been subjected to the powder spraying treatment is hung in the heating device, and the galvanized sheet to be tested is subjected to a heating and curing treatment.

[0013] Preferably, the concentration of the degreasing agent is 2-4%, the concentration of the surface conditioning agent is 4-6%, and the concentration of the phosphating solution is 9-11%.

[0014] Preferably, the conditions for degreasing treatment include: temperature of 40-50°C and time of 110-130s; the conditions for surface conditioning treatment include: temperature of 30-40°C and time of 20-40s; the conditions for phosphating treatment include: temperature of 40-60°C and time of 110-130s.

[0015] Preferably, the galvanized sheet to be tested is subjected to powder spraying treatment so that the thickness of the powder spraying coating is controlled to be 50 to 80 μm.

[0016] Preferably, the conditions for the heat curing treatment include: a temperature of 170 to 190° C. and a time of 10 to 30 minutes.

[0017] Preferably, the method further comprises: cleaning and drying the degreased galvanized sheet to be tested; the cleaning time is 10 to 20 seconds, and the drying conditions include: the temperature is 70 to 90° C., and the time is 5 to 15 minutes.

[0018] In a galvanized sheet rapid coating system and method for simulating a coating process described in the present invention, the following beneficial effects are achieved: in the present invention, degreasing, cleaning, surface conditioning and phosphating are integrated into one device, and a nozzle with an inward opening is opened on the side wall of the device. During use, the galvanized sheet is placed in the device using a hanging component, and the nozzle is at the same level as the top area of ​​the galvanized sheet, so that the nozzle can effectively spray the surface of the galvanized sheet to complete the degreasing, surface conditioning and phosphating treatment of the galvanized sheet. Electrostatic spraying is also used to perform powder spraying on the surface of the galvanized sheet, so that the surface spraying of the galvanized sheet can be more uniform, effectively improving the coating performance. The present invention adopts an internal simulated coating test for evaluation, and the entire cycle from on-site sampling to laboratory evaluation only takes one day, which greatly shortens the detection and evaluation cycle of the coating performance of the galvanized sheet, thereby completing efficient and accurate coating performance detection and evaluation of the galvanized sheet continuously produced by the galvanizing line. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a galvanized sheet rapid coating system for simulating a coating process in the present invention;

[0020] Figure 2 It is a schematic structural diagram of a spray device according to one embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the dimensions of a galvanized sheet to be tested after punching in one embodiment of the present invention;

[0022] Figure 4 This is a graph showing the results of the hundred-grid test of A-1 and A-2 after coating in Example 1 of the present invention;

[0023] Figure 5 This is a graph showing the results of the 100-grid test of B-1 and B-2 after coating in Example 1 of the present invention.

[0024] Reference numerals

[0025] 1. Spraying device; 2. Spraying device; 3. Heating device; 4. Solution tank; 5. Suspension component; 6. Nozzle. DETAILED DESCRIPTION

[0026] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0027] The first aspect of the present invention provides a galvanized sheet rapid coating system that simulates a coating process, such as Figure 1As shown, the system includes a spraying device 1, a spraying device 2 and a heating device 3; the spraying device 1 is used to spray a degreasing agent, a surface conditioning agent and a phosphating solution on the galvanized sheet to be tested respectively, so that the galvanized sheet to be tested is degreased, surface conditioned and phosphated in sequence; the spraying device 2 is used to electrostatically spray the galvanized sheet to be tested after the phosphating treatment; the heating device 3 is used to heat and solidify the galvanized sheet to be tested after the electrostatic spraying treatment.

[0028] In a specific embodiment of the system of the present invention, Figure 2 As shown, a solution tank 4 is installed inside the spray device 1, and the solution tank 4 is used to contain a degreasing agent, a surface conditioning agent and a phosphating solution respectively. A hanging component 5 is provided on the top of the spray device 1, and the hanging component 5 is used to place the galvanized sheet to be tested in the spray device 1. Specifically, the top of the galvanized sheet to be tested has a hole, a hook is introduced into the hole, and the galvanized sheet to be tested is hung inside the spray device 1 by the hook.

[0029] The side wall of the spray device 1 is provided with a nozzle 6 opening inward, and the top area of ​​the galvanized sheet to be tested is located at the same level as the nozzle 6. When in use, the solution tank 4 containing the degreasing agent, the surface conditioning agent and the phosphating solution is connected to the nozzle 6 through a connecting pipe, and the degreasing agent, the surface conditioning agent and the phosphating solution are sprayed on the galvanized sheet to be tested in turn by using the nozzle 6.

[0030] Specifically, the solution tank 4 is also used to contain water. After the galvanized sheet to be tested is degreased and phosphated, the nozzle 6 is used to spray water on the surface of the galvanized sheet to be tested to remove grease and solvent residues on the surface of the galvanized sheet to be tested.

[0031] In a preferred embodiment of the system of the present invention, the side wall of the spray device 1 is symmetrically provided with nozzles 6 opening inwards, which can effectively improve the coating efficiency.

[0032] In a specific embodiment of the system of the present invention, a hanging component is installed on the top of the spray device 2, and the hanging component is used to place the galvanized sheet to be tested after phosphating treatment in the spray device 2. The spray device 2 is equipped with an electrostatic spray gun, and the electrostatic spray gun is used to electrostatically spray the galvanized sheet to be tested after phosphating treatment. In this article, the structure of the hanging component on the top of the spray device 2 is the same as the structure of the hanging component of the spray device 1, and will not be repeated here.

[0033] In a specific embodiment of the system of the present invention, the top of the heating device 3 is also equipped with a hanging component similar to the top of the spraying device 1 and the spraying device 2. During actual operation, the galvanized sheet to be tested after electrostatic spraying is placed in the heating device 3 through the hanging component.

[0034] In the specific operation process of the system of the present invention, the galvanized sheet to be tested is placed in the spraying device 1 through the hanging component 5, a degreasing agent is first added to the solution tank 4, the degreasing agent is heated to a certain temperature, and the degreasing agent is sprayed on the surface of the galvanized sheet to be tested through the nozzle 6, then pure water is added to the solution tank 4, and the surface of the galvanized sheet to be tested is sprayed and cleaned through the nozzle 6 at room temperature, then a surface conditioner is added to the solution tank 4, the surface conditioner is heated to a certain temperature, and the surface conditioner is sprayed on the surface of the galvanized sheet to be tested through the nozzle 6, and then the solution tank 4 is added. A phosphating solution is added into the solution tank 4, the phosphating solution is heated to a certain temperature, and the phosphating solution is sprayed on the surface of the galvanized sheet to be tested through the nozzle 6; finally, pure water is added into the solution tank 4, and the surface of the galvanized sheet to be tested is sprayed and cleaned through the nozzle 6 at room temperature; then, the galvanized sheet to be tested is placed in the heating device 3 for drying; the dried galvanized sheet to be tested is hung in the spraying device 2, and the galvanized sheet to be tested is electrostatically sprayed by an electrostatic spray gun; finally, the galvanized sheet to be tested after the electrostatic spraying is hung in the heating device 3, and the galvanized sheet to be tested after the electrostatic spraying is heated and cured.

[0035] The second aspect of the present invention provides a method for rapid coating of galvanized sheet using a simulated coating process implemented by the above-mentioned system, the method comprising the following steps:

[0036] Punch one end of the galvanized sheet to be tested. The structure and size of the galvanized sheet to be tested after punching are as follows: Figure 3 As shown, the end that has been punched is hung in the spraying device 1, and the degreasing agent, the surface conditioning agent and the phosphating solution are sprayed on the galvanized sheet to be tested in turn, so that the galvanized sheet to be tested is degreased, surface conditioned and phosphated in turn; the galvanized sheet to be tested after being sprayed with the phosphating solution is hung in the spraying device 2, and the galvanized sheet to be tested is powder-sprayed by the electrostatic spray gun in the spraying device 2; the galvanized sheet to be tested after the powder spraying treatment is hung in the heating device 3, and the galvanized sheet to be tested is heated and cured.

[0037] In a specific implementation of the method of the present invention, firstly, the surface of the galvanized sheet to be tested after the punching treatment is cleaned with ethanol, and then the galvanized sheet to be tested is hung in the spray device 1 through a hook.

[0038] In a specific embodiment of the method of the present invention, the concentration of the degreasing agent is 2-4%. When the concentration of the degreasing agent is less than 2%, the cleaning is not thorough. When the concentration of the degreasing agent is greater than 4%, slight discoloration occurs on the surface. The concentration of the surface conditioner is 4-6%. When the concentration of the surface conditioner is less than 4%, the surface activity of the steel plate is insufficient, affecting subsequent phosphating. When the concentration of the surface conditioner is greater than 6%, residues are easily formed on the surface of the steel plate. The concentration of the phosphating solution is 9-11%. When the concentration of the phosphating solution is less than 9%, it is not easy to form a film. When the concentration of the phosphating solution is greater than 11%, the stability of the phosphating solution is threatened and additional residue is generated.

[0039] In this article, the degreasing agent model is FC-364S, and the phosphating liquid model is PB-139M.

[0040] In a specific embodiment of the method of the present invention, the conditions for degreasing treatment include: temperature of 40-50°C, time of 110-130s; the conditions for surface conditioning treatment include: temperature of 30-40°C, time of 20-40s; the conditions for phosphating treatment include: temperature of 40-60°C, time of 110-130s.

[0041] In a specific implementation of the method of the present invention, the galvanized sheet to be tested is powder-sprayed to control the thickness of the powder coating to be 50-80 μm. When the thickness of the powder coating is less than 50 μm, the protectiveness of the coating is insufficient. When the thickness of the powder coating is greater than 80 μm, the roughness and unevenness of the coating will be increased.

[0042] In a specific embodiment of the method of the present invention, the conditions for the heating and curing treatment include: a temperature of 170 to 190° C. and a time of 10 to 30 minutes.

[0043] In a specific embodiment of the method of the present invention, the method further comprises: cleaning and drying the galvanized sheet to be tested after degreasing treatment; the cleaning time is 10 to 20 seconds, and the drying conditions include: temperature of 70 to 90°C and time of 5 to 15 minutes.

[0044] The experimental methods or test methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0045] Example 1

[0046] A galvanized sheet rapid coating system that simulates the coating process, such as Figure 1 As shown, the system includes a spray device 1, a spray device 2 and a heating device 3; the structure of the spray device 1 is as follows Figure 2As shown, a solution tank 4 is installed inside the spray device 1, and the solution tank 4 is used to contain a degreasing agent, a surface conditioning agent and a phosphating solution respectively. A hanging component 5 is provided on the top of the spray device 1, and the hanging component 5 is used to place the galvanized sheet to be tested in the spray device 1. The side wall of the spray device 1 is symmetrically provided with nozzles 6 with inward openings, and the top area of ​​the galvanized sheet to be tested is located at the same level as the nozzle 6; a hanging component is installed on the top of the spraying device 2, and the hanging component is used to place the galvanized sheet to be tested after phosphating treatment in the spraying device 2, and the spraying device 2 is installed with an electrostatic spray gun, and the electrostatic spray gun is used to electrostatically spray the galvanized sheet to be tested after phosphating treatment; the heating device 3 is a heating box, and a hanging component is installed on the top of the heating box.

[0047] A method for rapid coating of a galvanized sheet using a simulated coating process implemented by the system described in Example 1, the method comprising the following steps:

[0048] Select two galvanized sheets after passivation treatment produced by the galvanizing line of a steel plant, take two pieces of each, cut the two galvanized sample sheets into two pieces of 150*50mm in size, record them as A-1, A-2, B-1 and B-2, punch holes (diameter 6mm) on the top of A-1, A-2, B-1 and B-2 respectively, and the size requirements are as follows Figure 3 As shown, clean the surface of the sample with ethanol;

[0049] First, add 3% concentration (FC-364S) degreasing agent to the solution tank 4, raise the temperature to 48°C, hang the samples A-1, A-2, B-1 and B-2 in the spray device 1, and use the nozzle 6 to spray the samples A-1, A-2, B-1 and B-2 for 120s respectively; add pure water to the solution tank 4, and spray and clean the samples A-1, A-2, B-1 and B-2 at room temperature for 30s; then add 5% concentration of FC-364S to the solution tank 4. Surface conditioning, heating to 35°C, using the nozzle 6 to spray samples A-1, A-2, B-1 and B-2 for 30 seconds; then adding 10% concentration (PB-139M) phosphating solution to the solution tank 4, heating to 52°C, using the nozzle 6 to spray samples A-1, A-2, B-1 and B-2 for 120 seconds; finally adding pure water to the solution tank 4, spraying and cleaning samples A-1, A-2, B-1 and B-2 at room temperature for 30 seconds;

[0050] Place the sprayed samples A-1, A-2, B-1 and B-2 in the heating box, set the heating box to 80°C, dry and heat the samples A-1, A-2, B-1 and B-2, heat for 10 minutes and then take them out to cool;

[0051] Subsequently, the samples A-1, A-2, B-1 and B-2 are hung in the spraying device 2, and the galvanized sheets to be tested are powder-sprayed using an electrostatic spray gun so that the coating thickness of the steel sheets is controlled to be 60 μm; finally, the galvanized sheets to be tested after powder spraying are hung in the heating box, the temperature is set to 180°C and heated for 20 minutes, and then taken out and cooled to obtain the coated A-1, A-2, B-1 and B-2.

[0052] Test Case

[0053] A-1, A-2, B-1 and B-2 were subjected to a 100-grid test after coating. Specifically, a 10×10 square grid was scratched on the surface coating of A-1, A-2, B-1 and B-2 after coating. For A-1 and B-1 after coating, 3M tape was used to stick to the grid, and the tape was quickly pulled up perpendicular to the substrate after 90±30s. For A-2 and B-2 after coating, a cupping test machine was used to perform a 6mm cupping on the 100-grid position, and the coating surface shedding of A-2 and B-2 after coating was observed. If the 100-grid shedding area of ​​the coating surface is less than 5% of the total area, it is considered to have passed the test, otherwise the test is unqualified. When both A-2 and B-2 after coating are qualified, the coating performance is determined to meet the standard.

[0054] The results of the 100-grid test of A-1, A-2, B-1 and B-2 after coating are as follows: Figures 4-5 As shown, according to the experimental results, A-1 and A-2 after painting are qualified, and the coating performance of sample A is judged to be up to standard; B-1 after painting is qualified, and B-2 after painting is unqualified, so the coating performance of sample B is judged to be unqualified.

[0055] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A galvanized sheet rapid coating system simulating a coating process, characterized in that: The system comprises a spraying device (1), a spraying device (2) and a heating device (3); The spraying device (1) is used to spray a degreasing agent, a surface conditioning agent and a phosphating solution respectively on the galvanized sheet to be tested, so that the galvanized sheet to be tested is degreased, surface conditioned and phosphated in sequence; The spraying device (2) is used to perform electrostatic spraying on the galvanized sheet to be tested after phosphating treatment; The heating device (3) is used to heat and solidify the galvanized sheet to be tested after the electrostatic spraying treatment.

2. The galvanized sheet rapid coating system according to claim 1 is characterized in that: A solution tank (4) is installed inside the spray device (1), and the solution tank (4) is used to contain a degreasing agent, a surface conditioning agent, and a phosphating solution, respectively. A hanging component (5) is provided on the top of the spray device (1), and the hanging component (5) is used to place the galvanized sheet to be tested in the spray device (1). A nozzle (6) with an inward opening is provided on the side wall of the spray device (1), and the top area of ​​the galvanized sheet to be tested and the nozzle (6) are located at the same level. When in use, the solution tanks (4) containing the degreasing agent, the surface conditioning agent, and the phosphating solution are connected to the nozzle (6), and the degreasing agent, the surface conditioning agent, and the phosphating solution are sprayed on the galvanized sheet to be tested in sequence by using the nozzle (6).

3. The galvanized sheet rapid coating system according to claim 2 is characterized in that: The side wall of the spray device (1) is symmetrically provided with nozzles (6) opening inwards.

4. The galvanized sheet rapid coating system according to claim 1, characterized in that: A hanging component is installed on the top of the spraying device (2), and the hanging component is used to place the galvanized sheet to be tested after phosphating treatment in the spraying device (2). The spraying device (2) is installed with an electrostatic spray gun, and the electrostatic spray gun is used to perform electrostatic spraying treatment on the galvanized sheet to be tested after phosphating treatment.

5. A method for rapid coating of galvanized sheet by simulating coating process implemented by the system according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: Punching one end of the galvanized sheet to be tested, and hanging the punched end in the spraying device (1), spraying the galvanized sheet to be tested with a degreasing agent, a surface conditioning agent, and a phosphating solution in sequence, respectively, so that the galvanized sheet to be tested is degreased, surface conditioned, and phosphated in sequence; The galvanized sheet to be tested, which has been sprayed with the phosphating solution, is hung in the spraying device (2), and the galvanized sheet to be tested is subjected to powder spraying treatment using an electrostatic spray gun in the spraying device (2); The galvanized sheet to be tested that has been subjected to the powder spraying treatment is hung in the heating device (3), and the galvanized sheet to be tested is subjected to a heating and curing treatment.

6. The method for rapid coating of galvanized sheet according to claim 5, characterized in that: The concentration of the degreasing agent is 2-4%, the concentration of the surface conditioning agent is 4-6%, and the concentration of the phosphating solution is 9-11%.

7. The rapid coating method for galvanized sheet according to claim 5, characterized in that: The conditions for degreasing treatment include: temperature of 40 to 50°C and time of 110 to 130 seconds; The conditions for surface conditioning treatment include: temperature of 30-40°C, time of 20-40s; The conditions of phosphating treatment include: temperature of 40 to 60° C. and time of 110 to 130 seconds.

8. The method for rapid coating of galvanized sheet according to claim 5, characterized in that: The galvanized sheet to be tested is powder-sprayed to control the thickness of the powder-sprayed coating to be 50-80 μm.

9. The method for rapid coating of galvanized sheet according to claim 5, characterized in that: The conditions of the heat curing treatment include: a temperature of 170 to 190° C. and a time of 10 to 30 minutes.

10. The method for rapid coating of galvanized sheet according to claim 5, characterized in that: The method also includes: cleaning and drying the degreased galvanized sheet to be tested; the cleaning time is 10 to 20 seconds, and the drying conditions include: the temperature is 70 to 90° C. and the time is 5 to 15 minutes.

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