Rapid and accurate quantitative evaluation method for corrosion performance of steel electrophoresis plate for vehicle body

Abstract

The invention relates to a rapid and accurate quantitative evaluation method for the corrosion performance of a steel electrophoresis plate for a vehicle body, which comprises the following steps of: preparing and pretreating a standardized sample, and cooperatively controlling specific chemical components, surface appearance and coating process parameters; and then carrying out a short-period accelerated corrosion test, and accurately predicting a 1000-hour long-term corrosion behavior by utilizing an original prediction formula model based on performance detection data. According to the method, the industrial problems of long period, high cost and low efficiency of a traditional evaluation method are solved, the evaluation period as long as 42 days is shortened to 10 days, and the efficiency is improved by 76% or above. According to the method, the plate with the best adaptability to the target coating system can be rapidly and accurately screened out and directly used for final certification sample delivery, meanwhile, a scientific basis is provided for material selection optimization and coating process improvement of the electrophoresis plate of the vehicle body, and the method has remarkable engineering application value.

Description

Technical Field

[0001] This patent application belongs to the field of metal material corrosion protection technology. More specifically, it relates to a rapid evaluation method for the corrosion performance of electrophoretic steel plates for car bodies based on accelerated corrosion testing and mathematical modeling. It is particularly suitable for the quantitative evaluation of the corrosion resistance of cold-rolled steel plate coating systems in the automotive manufacturing field. Background Technology

[0002] As a crucial material in automobile manufacturing, the corrosion performance of steel electrophoretic coatings used in car bodies directly affects the vehicle's service life, safety, and appearance quality. With the rapid development of the automotive industry and increasingly fierce market competition, higher demands are being placed on the corrosion performance of steel electrophoretic coatings used in car bodies. Traditional corrosion performance evaluation methods often suffer from problems such as long evaluation cycles, complex operations, and highly subjective results, making it difficult to meet the needs of modern automobile manufacturing for rapid and accurate evaluation.

[0003] Currently, the evaluation of the corrosion performance of electrophoretic coatings for automotive steel mainly relies on long-term corrosion tests under laboratory conditions, such as neutral salt spray tests (generally greater than or equal to 1000 hours for cold-rolled steel, hot-formed steel, etc.) and cyclic salt spray tests (generally greater than or equal to 552 hours for cold-rolled steel, galvanized steel, hot-formed steel, etc.). While these traditional methods can realistically simulate the corrosion environment of electrophoretic coatings for automotive steel during actual use, they suffer from drawbacks such as long testing cycles and high costs.

[0004] These traditional methods have fatal flaws: extremely long testing cycles (especially for neutral salt spray, which typically lasts over 42 days), high labor and material costs, results heavily influenced by human factors, and poor consistency. This makes material certification a bottleneck in R&D progress, particularly during new material development, new vehicle certification, or supplier switching. Engineers are unable to quickly select the best-performing material from a variety of candidate materials, choosing the one with the best compatibility with the coating system, and are forced to passively wait for lengthy testing results, severely slowing down the overall R&D pace.

[0005] Therefore, creatively developing a method that can quickly and accurately quantify the corrosion performance of steel electrophoretic plates for car bodies, and can be directly used to guide the selection of materials for certification samples, is of great significance for improving the efficiency of automotive sheet manufacturing, reducing production costs, and ensuring the quality of automotive products. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a rapid and accurate quantitative evaluation method for the corrosion performance of steel electrophoretic plates for car bodies. The aim is to establish a quantitative relationship model between corrosion performance and corrosion conditions through statistical analysis of corrosion test data, so as to achieve a rapid, objective and accurate evaluation of the corrosion performance of steel electrophoretic plates for car bodies.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows: A rapid and accurate quantitative evaluation method for the corrosion performance of electrophoretic coatings for automotive bodies includes the following steps: a. Sample preparation steps: Select newly produced cold-rolled steel sheets. Before coating, wipe the grease off the surface of the sheets with alcohol. Coating and attach the sheets on the target car manufacturer's coating production line. Select multiple representative samples from the electrophoretic steel sheets of the car body to be evaluated. b. Pretreatment steps: The surface of the electrophoresis plate sample is wiped with alcohol and dried to remove surface oil, impurities, and other contaminants. The surface of the electrophoresis plate is then scored using a tool width required by the target automaker, just enough to break through the paint film and expose the steel substrate.

[0008] c. Corrosion test procedure: Place the pretreated sample in a preset corrosion environment for corrosion testing. The corrosion environment includes the corrosive medium, temperature and corrosion time. d. Performance Testing Procedure: After the corrosion test, the corrosion performance of the sample is tested, including the maximum unilateral corrosion width. After testing, the maximum corrosion width on the surface of the electrophoretic plate sample is evaluated and denoted as xi, where i can take values ​​of 1, 2, 3, ... e. Data analysis steps: Substitute the detected data into the prediction formula model, y = α1 + (α2-α1) / (1 +10^((lgβ-x) *γ)), where α1=1.26494, α2=3.66763, β=98.72110, γ=2.23978, and the maximum single-sided erosion width y of the plate after 1000h can be predicted.

[0009] f. Quantitative evaluation steps: Based on the prediction formula model, the corrosion performance of the steel electrophoretic plate for the car body is rapidly and accurately quantitatively evaluated, and the quantitative evaluation results are output.

[0010] Furthermore, in the method of the present invention, the plate material is particularly suitable for continuous annealing plates (without coating) produced by humidification in a continuous annealing furnace, and its chemical composition satisfies C≤0.003wt%, Mn:0.05-0.20wt%, Si:0.002-0.010wt%; the belt speed during annealing of the continuous annealing steel plate is 125-200 m / min.

[0011] Furthermore, the method of the present invention is particularly suitable for plates with a surface roughness range of 0.7-1.5μm and an RPC range of 60-110 particles / cm.

[0012] Furthermore, in the method of the present invention, the prediction formula model is particularly limited to the pretreatment of a thin film, the film weight range of 20-35 mg / m2, and the paint film thickness range of 15-25 μm.

[0013] Furthermore, in the method described in this invention, the corrosive environment is a neutral salt spray corrosion environment, the corrosive medium is a 10 wt.% sodium chloride solution, the temperature is 40°C, and the detection time is 240 hours. Other test conditions are performed according to GB / T10125-2021 Artificial Atmosphere Corrosion Test - Salt Spray Test.

[0014] This method also includes a step of verifying the quantitative evaluation results by comparing them with the results of neutral salt spray testing after 1000 hours of artificial atmosphere corrosion test according to GB / T10125-2021, in order to verify the accuracy and reliability of the prediction formula model.

[0015] The method also includes classifying the corrosion resistance of steel electrophoretic plates for vehicle bodies based on quantitative evaluation results, selecting the plates with the best surface quality as the final plates supplied to customers, and proposing corresponding improvement suggestions.

[0016] Due to the adoption of the above technical solution, the beneficial effects achieved by this invention are: This invention, by establishing a standardized accelerated corrosion testing process and mathematical prediction model, can significantly shorten the testing cycle and reduce testing costs, effectively improving the accuracy and repeatability of corrosion performance evaluation. Through a systematic quantitative analysis system, it not only achieves accurate prediction of long-term corrosion behavior but also provides direct guidance for production process improvement, thereby comprehensively improving the quality control level and corrosion resistance evaluation efficiency of automotive body electrophoretic panels. It has broad application prospects and industry promotion value. Attached Figure Description

[0017] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the embodiments.

[0019] A rapid and accurate quantitative evaluation method for the corrosion performance of electrophoretic coatings for automotive steel, such as... Figure 1 This includes the following steps: a. Sample preparation steps: Select newly produced cold-rolled steel sheets as the sheet material. Before coating, wipe the grease off the surface of the sheet material with alcohol. Coating and hanging the sheet material is carried out on the coating production line of the target car company. Select multiple representative electrophoretic sheet samples from the body steel electrophoretic sheets to be evaluated. b. Pretreatment steps: The surface of the electrophoresis plate sample is wiped with alcohol and dried to remove oil, impurities and other contaminants. The surface of the electrophoresis plate sample is scratched with a tool width required by the target car manufacturer, just enough to break through the paint film and expose the steel substrate. c. Corrosion test procedure: Place the pretreated electrophoretic plate sample in a preset corrosion environment for corrosion test, wherein the corrosion environment includes the corrosive medium, temperature and corrosion time; d. Performance testing steps: After the corrosion test, the corrosion performance of the electrophoretic plating sample is tested, including the maximum single-sided corrosion width y; after the test, the maximum corrosion width on the surface of the electrophoretic plating sample is evaluated and recorded as x. i i can take the values ​​1, 2, 3, ...; e. Data analysis steps: Substitute the data obtained from the performance test into the prediction formula model, y = α1+ (α2-α1) / (1 + 10^((lgβ-x) *γ)), α1=1.26494, α2=3.66763, β=98.72110, γ=2.23978, and the maximum single-sided erosion width y of the plate after 1000h can be predicted, where x is the maximum erosion width; f. Quantitative evaluation steps: Based on the prediction formula model, the corrosion performance of the steel electrophoretic plate for the car body is rapidly and accurately quantitatively evaluated, and the quantitative evaluation results are output.

[0020] In step a, the plate is suitable for continuous annealing plates produced by humidification in a continuous annealing furnace. The surface of the continuous annealing plate has no coating, and its chemical composition meets the following requirements: C≤0.003wt%, Mn:0.05-0.20wt%, Si:0.002-0.010wt%. The belt speed during annealing of the continuous annealing steel plate is 125-200 m / min.

[0021] The surface roughness of the plate ranges from 0.7 to 1.5 μm, and the RPC ranges from 60 to 110 particles / cm.

[0022] In step c, the corrosive environment is a neutral salt spray corrosion environment, the corrosive medium is a sodium chloride solution with a mass fraction of 10 wt.%, the temperature is 40℃, and the corrosion time is 240h.

[0023] In step e, the prediction formula model is specifically limited to pretreatment of a thin film with a film weight range of 20-35 mg / m³. 2 The film thickness ranges from 15 to 25 μm.

[0024] The method further includes step g. g. Verification of the quantitative evaluation results: The accuracy and reliability of the prediction formula model are verified by comparing it with the results of the neutral salt spray test after 1000 hours of artificial atmosphere corrosion test according to GB / T10125-2021.

[0025] The method further includes step h. h. Corrosion resistance rating: The corrosion resistance of the steel electrophoretic plates for car bodies is rated based on the quantitative evaluation results. The plates with the best surface quality are selected as the final plates to be supplied to customers, and corresponding improvement suggestions are made.

[0026] The technical solution of the present invention will be further described in detail below through embodiments.

[0027] Examples 1-6 Cold-rolled steel sheets produced by a certain company were selected as test materials. Test material A was used in Example 1 and Comparative Example 1, test material B was used in Example 2 and Comparative Example 2, and test material C was used in Example 3 and Comparative Example 3 to verify the reliability of the endpoint and intermediate values ​​of the parameters. Test material D was used in Example 4 and Comparative Example 4, test material E was used in Example 5 and Comparative Example 5, and test material F was used in Example 6 and Comparative Example 6 to verify the reliability of each key influencing factor.

[0028] Examples 1, 2, and 3 used the plates treated with this technical solution. Comparative Examples 1, 2, and 3 underwent a neutral salt spray test for 1000 hours in an artificial atmosphere according to GB / T 10125-2021, and the maximum single-sided corrosion width of the electrophoretic plate was evaluated.

[0029] Example 4 removes the control of chemical composition, and the chemical composition is not within the scope of this invention; other processing procedures and parameters are performed according to the technology of this invention. Example 5 removes the control of surface roughness-related parameters, and surface roughness-related parameters are not within the scope of this invention; other processing procedures and parameters are performed according to the technology of this invention. Example 6 removes the control of film weight and paint film thickness, and film weight and paint film thickness-related parameters are not within the scope of this invention; other processing procedures and parameters are performed according to the technology of this invention. Comparative Examples 4, 5, and 6 were subjected to a neutral salt spray test for 1000 hours using GB / T 10125-2021 artificial atmosphere corrosion test, and the maximum single-sided corrosion width of the electrophoretic plate was evaluated.

[0030] The rapid and accurate quantitative evaluation method for assessing the corrosion performance of electrophoretic steel plates used in car bodies, using this technical solution, includes sample preparation, pretreatment, corrosion testing, performance detection, data analysis, and quantitative evaluation steps, as detailed below: (1) Sample preparation steps: Select newly produced cold-rolled steel sheets, especially those produced by continuous annealing furnace with humidification (without coating), whose chemical composition meets the following requirements: C≤0.003wt%, Mn:0.05-0.20wt%, Si:0.002-0.010wt%; the annealing speed of the continuous annealing steel sheet is 125-200 m / min. The sheet is especially suitable for sheet surfaces with a roughness range of 0.7-1.5μm and an RPc range of 60-110 peaks / cm. RPc range is a professional term, which we usually call "peak and trough number". This is described in detail in the national standard "GBT2523-Method for measuring surface roughness and peak number of cold-rolled metal sheets (strips).pdf". In this standard, it is called "peak number", which is on page 4 of the PDF, page 2 in the document, 3.4 Peak number.

[0031] Before coating, the surface grease of the sheet metal was wiped off with alcohol. Coating was then performed on the target automaker's coating production line. Several representative electrophoretic coating samples were selected from the steel electrophoretic coating sheets to be evaluated for the vehicle body. The predictive model is specifically limited to pretreatment as a thin film, with a film weight range of 20-35 mg / m³. 2 The film thickness ranges from 15 to 25 μm.

[0032] (2) Pretreatment steps: The surface of the electrophoresis plate sample is wiped with alcohol and dried to remove oil, impurities and other contaminants. The surface of the electrophoresis plate is scratched with a tool width required by the target car manufacturer, just enough to break through the paint film and expose the steel substrate.

[0033] (3) Corrosion test procedure: The pretreated sample is placed in a preset corrosion environment for corrosion testing. The corrosion environment includes the corrosive medium, temperature, and corrosion time. The corrosion environment is a neutral salt spray corrosion environment, the corrosive medium is a 10 wt.% sodium chloride solution, the temperature is 40℃, and the corrosion time is 240h. Other experimental conditions are in accordance with GB / T10125-2021 Artificial Atmosphere Corrosion Test - Salt Spray Test.

[0034] (4) Performance testing steps: After the corrosion test, the electrophoretic plate samples are subjected to corrosion performance testing, including the maximum single-sided corrosion diffusion width y. After the test, the maximum corrosion diffusion width on the parallel test plate surface is evaluated and denoted as xi, where i can take values ​​of 1, 2, 3, ... (5) Data analysis steps: Substitute the data obtained from the performance test into the prediction formula model, y = α1 + (α2-α1) / (1 + 10^((lgβ-x) *γ)), where α1=1.26494, α2=3.66763, β=98.72110, γ=2.23978, and the maximum single-sided erosion width y of the plate after 1000h can be predicted.

[0035] (6) Quantitative evaluation steps: Based on the quantitative relationship model, the corrosion performance of the steel electrophoretic plate for the car body is quickly and accurately evaluated, and the quantitative evaluation results are output.

[0036] In addition, it also includes step g, g. Verification of the quantitative evaluation results: The accuracy and reliability of the prediction formula model are verified by comparing it with the results of the neutral salt spray test after 1000 hours of artificial atmosphere corrosion test according to GB / T10125-2021.

[0037] It also includes step h, h. Corrosion resistance rating: The corrosion resistance of the steel electrophoretic plates for car bodies is rated based on the quantitative evaluation results. The plates with the best surface quality are selected as the final plates to be supplied to customers, and corresponding improvement suggestions are made.

[0038] 1. What are some suggestions for improvement? Based on the quantitative evaluation results, the following improvement suggestions can be provided: (1) Recommendations for the board itself: If the predicted y value of a certain board is consistently high, it is recommended to adjust its chemical composition (such as reducing the C and Si content and optimizing the Mn content) or production process (such as optimizing the annealing process and the surface roughness Ra and RPc values).

[0039] (2) Recommendations for coating process: If the predicted y values ​​of all boards are too high, the problem may be due to the coating process. It is recommended to optimize the pretreatment (such as adjusting the film weight) or electrophoresis process parameters (such as adjusting the voltage and penetration force to optimize the film thickness and its uniformity).

[0040] (3) Recommendations for detection and model: If there is a systematic deviation between the short-term prediction result y and the long-term verification result y', it is recommended to calibrate and iteratively optimize the parameters (α1, α2, β, γ) in the prediction model to adapt to the new production line or material system.

[0041] 2. How to choose the best quality board material? Based on the quantitative evaluation results output in step (f), i.e., the predicted maximum single-sided erosion width y value over 1000 hours, the optimal selection is made. The plate corresponding to the electrophoretic plate sample with the smallest y value is determined to be the plate with the best compatibility with the target coating system and the best surface quality.

[0042] Meanwhile, the y-value must meet the automaker's internal quality control standards (for example, y is usually required to be ≤ 1.5 or 2.0 mm). The preferred order is: among the samples that meet the quality standards, select the sheet material with the smallest y-value; if all samples fail to meet the standards, select the sheet material with the smallest y-value as the benchmark for process improvement.

[0043] 3. This patent is not just a "detection method", but also an "intelligent screening and optimization guidance system".

[0044] This invention replaces time-consuming long-term experiments with short-term experiments and model predictions. The ultimate goal is to quickly and scientifically select the best materials and provide directions for improvement, thereby saving a lot of time and money.

[0045] The detection parameters for each detection item in each embodiment are shown in Table 1; the detection results for each embodiment are shown in Table 2; and the effect comparison is shown in Table 3.

[0046] Table 1 Key parameters of each embodiment

[0047] Table 2 Detection results of each embodiment

[0048] Table 3 Comparison of Results

[0049] As shown in Tables 1-3, this invention, through the combination of standardized accelerated corrosion testing and mathematical models, significantly improves the efficiency, accuracy, consistency, and effectiveness of evaluating the corrosion performance of electrophoretic steel plates for automotive bodies, while saving experimental and time costs. In particular, the implementation effects of Examples 4-6 highlight the advantages, uniqueness, and inventiveness of the key factor control technology of this invention, and demonstrate that changes in these factors result in inferior effects compared to this patent application. This invention creatively provides a scientific basis and research direction for coating process optimization and plate material selection, possessing broad engineering application value and promising industry promotion prospects.

[0050] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for rapid and accurate quantitative evaluation of the electrophoretic panel corrosion performance of a steel for a vehicle body, characterized by, The method comprises the following steps: a. Sample preparation step: select a newly produced cold rolled steel plate as the plate, before painting, use alcohol to wipe the surface grease of the plate, and paint the hanging piece on the target vehicle enterprise painting production line, select a plurality of representative electrophoresis plate samples from the electrophoresis plate to be evaluated; b. Pretreatment step: alcohol wiping and drying treatment are performed on the surface of the electrophoresis plate sample to remove surface oil stains, impurities and other pollutants, and a knife width required by the target vehicle enterprise is used to scratch the surface of the electrophoresis plate sample, and the paint film is required to be just scratched to expose the steel substrate; c. Corrosion test step: the pretreated electrophoresis plate sample is placed in a predetermined corrosion environment for corrosion test, and the corrosion environment includes corrosion medium, temperature and corrosion time; d.The performance detection step: after the end of the corrosion test, the electrophoresis plate sample is subjected to corrosion performance detection, and the detection items involve the maximum single-side corrosion width y; after the detection is completed, the maximum corrosion width of the surface of the electrophoresis plate sample is evaluated, and is respectively recorded as x i , i can take values 1, 2, 3,...; e. Data analysis step: the data obtained by performance detection is brought into the prediction formula model, y = α1+ (α2-α1) / (1 +10^((lgβ-x) *γ)), α1=1.26494, α2=3.66763, β=98.72110, γ=2.23978, the maximum single-side corrosion width y of the plate after 1000h can be predicted, and x is the maximum corrosion width; f. Quantitative evaluation step: according to the prediction formula model, the corrosion performance of the electrophoresis plate of the vehicle body steel is quickly and accurately quantitatively evaluated, and the quantitative evaluation result is output.

2. The method according to claim 1, characterized in that, In step a, the plate is suitable for continuous annealing furnace with humidification production, and the continuous annealing plate has no plating layer, and the chemical composition meets C≤0.003wt%, Mn: 0.05-0.20wt%, Si: 0.002-0.010wt%; the strip speed of the continuous annealing steel plate is 125-200 m / min.

3. The method according to claim 2, characterized in that, The surface roughness of the plate ranges from 0.7 to 1.5 μm, and the RPc range is 60-110 per / cm.

4. The method according to claim 1, characterized in that, In step c, the corrosion environment is neutral salt spray corrosion environment, the corrosion medium is 10wt.% sodium chloride solution, the temperature is 40℃, and the corrosion time is 240h.

5. The method according to claim 1, characterized in that, In step e, the prediction formula model is especially limited to a film before the finishing treatment, with a film weight in the range of 20-35 mg / m 2 , and a paint film thickness in the range of 15-25 μm.

6. The method according to any one of claims 1-5, characterized in that, The method further comprises step g, g. Verify the quantitative evaluation result: compare the neutral salt spray detection result after 1000h with the GB / T10125-2021 artificial atmosphere corrosion test salt spray test to verify the accuracy and reliability of the prediction formula model.

7. The method according to claim 6, characterized in that, The method further comprises step h, h. Corrosion resistance grading: according to the quantitative evaluation result, the corrosion resistance of the electrophoresis plate of the vehicle body steel is graded, the plate with the best surface quality is selected as the final plate supplied to the customer, and the corresponding improvement suggestions are put forward.

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