Multi-parameter metal coating corrosion accelerated detection method

Abstract

The embodiment of the invention provides an accelerated detection method for corrosion of a multi-parameter metal coating. The method comprises the following steps: pretreating the surface of a sample; a corrosive medium stock solution is prepared, the corrosive medium stock solution comprises hygroscopic chloride, a pH regulator and water, and the pH of the stock solution is within the range of 9.5 + / -0.5; preparing test slurry, namely mixing the soil-based medium with the stock solution to form the test slurry, and mixing a part of the test slurry with the same volume of water to obtain the diluted test slurry with the pH value within the range of 7.0 + / -0.5; carrying out corrosion acceleration detection under an environment control condition, and contacting the surface of the sample with the test slurry at a temperature in a range of 60 + / -3 DEG C and a relative humidity in a range of 23 + / -5%; and evaluating the corrosion degree. The technical problem that an existing detection method is not matched with an actual corrosion scene and lacks a detection system is solved.

Description

Technical Field

[0001] This application relates to the field of corrosion detection of chromium-plated parts, and more particularly to an accelerated detection method and evaluation method for chloride ion corrosion resistance of chromium-plated layers. Background Technology

[0002] As a widely used means of transportation outdoors, automobiles are subject to aging, corrosion and failure due to climatic environmental factors such as sunlight, rain, temperature and humidity. This affects the appearance and performance of the car, and in severe cases, can even create safety hazards and reduce the reputation of the car brand.

[0003] Countries like Europe, America, and Japan started research on automotive weather resistance earlier, forming a complementary system of industry standards and enterprise standards, with professional service organizations providing weather resistance testing and evaluation services to automakers. Some domestic car brands lag behind in weather resistance performance, mainly manifested in a high number of failures, short failure cycles, and high degrees of failure. A significant reason for this is the incomplete aging standard system of some domestic brands, fragmented standard management, failure to adapt standard content to the actual needs of automakers, and the lack of utilization of the third-party role of professional service organizations. Furthermore, some domestic automakers, due to a lack of technological accumulation and limitations, have not conducted targeted research on the automotive service environment and have not proposed differentiated technical requirements, resulting in insufficient weather resistance in their automotive products.

[0004] Existing technologies have significant limitations in assessing the chloride ion corrosion resistance of chrome-plated parts, especially in simulating real-world and variable overseas usage environments, where they cannot accurately predict and evaluate the long-term stability of the plating. Therefore, developing new testing methods and technical systems to more accurately evaluate the corrosion resistance of chrome-plated coatings is of great significance for enhancing the competitiveness of China's automotive industry and protecting consumer rights.

[0005] There are still problems in this field, such as the mismatch between traditional testing methods for the corrosion resistance of chrome-plated parts and actual corrosion scenarios, as well as the lack of testing systems. Summary of the Invention

[0006] This application provides a method for accelerating the detection of corrosion in metal coatings, which at least solves the technical problems of existing detection methods not matching actual corrosion scenarios and lacking a detection system.

[0007] According to one aspect of the embodiments of this application, a method for accelerating corrosion detection of metal coatings is provided, comprising: sample surface pretreatment, cleaning the sample surface with a mixture of organic solvent and water; preparation of a corrosive medium reserve solution, the corrosive medium reserve solution comprising a hygroscopic chloride, a pH adjuster and water, wherein the pH of the reserve solution is in the range of 9.5 ± 0.5 and is used to form a test slurry; preparation of the test slurry, mixing a soil-based medium with the reserve solution to form a test slurry, wherein a portion of the test slurry is mixed with an equal volume of water, and the resulting diluted test slurry has a pH value in the range of 7.0 ± 0.5; conducting accelerated corrosion detection under environmentally controlled conditions, exposing the sample surface to corrosion by contacting the test slurry at a temperature in the range of 60 ± 3°C and a relative humidity in the range of 23 ± 5%; and corrosion degree assessment, assessing the corrosion degree of the sample at specified time intervals according to a preset standard rating scale.

[0008] Furthermore, the metal plating layer is an electroplated chromium layer; and / or the organic solvent is selected from one or more of isopropanol, ethanol, methanol or acetone, and the volume ratio of the organic solvent to water in the mixture is 50:50.

[0009] Furthermore, the hygroscopic chloride is one or more selected from calcium chloride dihydrate, sodium chloride, potassium chloride, or mixtures thereof.

[0010] Furthermore, the pH adjuster is one or more of sodium hydroxide solution and sulfuric acid solution.

[0011] Furthermore, the soil substrate is kaolin.

[0012] Furthermore, in the preparation of the corrosive medium reserve solution, the pH adjuster is a 0.25 N sodium hydroxide solution.

[0013] Furthermore, in the preparation of the test slurry, 5 mL of the stock solution was mixed with 3 g of kaolin.

[0014] Furthermore, accelerated corrosion testing involves placing the sample inside a test chamber and maintaining the sample under controlled environmental conditions throughout the testing process until the evaluation time point.

[0015] Furthermore, the corrosion assessment also includes removing the sample from the test chamber, wiping the sample to remove the test slurry, and evaluating each area where the test slurry was removed.

[0016] Furthermore, the storage solution has a shelf life of 1 month, and the test slurry has a shelf life of 12 hours.

[0017] This application provides a method for accelerating the detection of corrosion in metal plating. The method (chromium plating resistance to chloride slurry test) simulates the corrosive effect of a thin film containing hygroscopic chlorides (such as calcium chloride dihydrate) and solid materials (such as kaolin) on electroplated chromium in a laboratory setting. This method can be used for standardized acceptance testing, simulated service assessment, manufacturing control, and research and development. It targets electrodeposited chromium coated parts exposed to hygroscopic chlorides (such as calcium chloride dihydrate). The test method of this invention simulates the loss of decorative and functional chromium deposits when exposed to "slurry / solid materials" and hygroscopic chlorides (such as calcium chloride dihydrate), establishing a standardized test method.

[0018] By introducing multi-parameter coupling technology, a corrosion simulation closer to the real environment was achieved, effectively evaluating the corrosion resistance of chromium plating layers under complex conditions. This method not only improves the accuracy and reliability of detection but also shortens the evaluation cycle and reduces costs. In particular, the application of this system and method is of great significance for promoting the development and application of environmentally friendly materials in the automotive industry, improving the weather resistance of automotive parts, and enhancing the international competitiveness of Chinese automotive brands. Through accurate corrosion assessment, automakers can more effectively optimize material selection and process flows, reduce product recalls due to corrosion problems, maintain brand image, and ensure consumer safety. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0020] Figure 1 These are photographs of the chromium loss levels during the implementation of the corrosion acceleration test of this invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0023] As described in the background section, existing detection methods suffer from incompatibility with actual corrosion scenarios and a lack of comprehensive detection systems. To address these issues, this application provides a method for accelerating corrosion detection of metal coatings, comprising: sample surface pretreatment, cleaning the sample surface with a mixture of organic solvent and water; preparation of a corrosive medium reserve solution, comprising hygroscopic chloride, pH adjuster, and water, wherein the pH of the reserve solution is within the range of 9.5 ± 0.5 and is used to form a test slurry; test slurry preparation, mixing a soil-based medium with the reserve solution to form a test slurry, and after mixing a portion of the test slurry with an equal volume of water, the resulting diluted test slurry has a pH value within the range of 7.0 ± 0.5; accelerated corrosion detection under controlled environmental conditions, exposing the sample surface to the test slurry at a temperature within the range of 60 ± 3°C and a relative humidity within the range of 23 ± 5% to expose the sample to corrosion; and corrosion degree assessment, evaluating the corrosion degree of the sample at specified time intervals according to a pre-set standard rating scale.

[0024] The technical solution of this embodiment solves the problems of mismatch between traditional testing methods for the corrosion resistance of chrome-plated parts and actual corrosion scenarios, as well as the technological gap in the testing system. Specifically, this invention combines multiple environmental factors such as temperature, humidity, pH value, and hygroscopic chlorides to form a multi-parameter coupled corrosion testing system. This multi-parameter environmental simulation technology can more realistically simulate the stress changes and corrosion processes of chrome-plated parts in outdoor environments, especially in environments containing hygroscopic chlorides. Through sample surface pretreatment, the sample surface is cleaned using a mixture of organic solvent and water, ensuring no impurities remain and improving the accuracy and reliability of the test. In the test slurry formulation, the specific ratio of soil-based medium to corrosive medium reserve solution and the precise control of its pH value form a corrosion test slurry representative of actual environments. This slurry can effectively simulate the mud deposited on chrome-plated coatings in overseas winter road environments, especially the presence of hygroscopic chlorides such as calcium chloride, which significantly enhances the corrosive effect of the medium. Environmental control conditions were set at a temperature of 60±3°C and a relative humidity of 23±5%, ensuring the consistency and repeatability of the tests while accelerating the corrosion process of the chromium plating layer and rapidly assessing its corrosion resistance. Corrosion degree assessment was based on a pre-set standard rating scale, quantifying the corrosion degree of the samples at specified time intervals. This method not only directly reflects the corrosion state of the plating layer but also provides a scientific basis for subsequent product optimization and quality control. In summary, the technical solution of this application, through multi-parameter coupled corrosion detection of the chromium plating layer, achieves effective assessment and prediction of the corrosion resistance of chromium-plated parts, filling a gap in the industry's testing system. This contributes to improving the weather resistance and extending the service life of automotive parts, while also promoting the development and application of environmentally friendly materials in the automotive industry.

[0025] Specifically, the multi-parameter environmental simulation technology in this embodiment uses hygroscopic chlorides as corrosion promoters and sodium hydroxide or sulfuric acid as pH adjusters to ensure that the pH value of the diluted test slurry is stable at 7.0±0.5. This near-neutral pH value is beneficial for simulating the corrosion conditions of chromium-plated parts in real environments, especially the corrosion effect of calcium chloride slurry on roads in overseas winters. Sample surface pretreatment involves cleaning with a mixture of organic solvent and water to remove surface grease and dust, ensuring that the corrosive medium can directly act on the coating, improving the realism and effectiveness of the test. The precise proportioning and pH control of the test slurry, combined with environmental control conditions, create an environment that accelerates corrosion, which helps to assess the stability and durability of the coating in a shorter time. Standardization of corrosion degree assessment ensures the comparability and interpretability of test results, providing a basis for subsequent material selection, coating process optimization, and product quality control. Therefore, the technical solution provided by this invention can effectively evaluate and predict the corrosion resistance of chromium-plated parts in environments containing hygroscopic chlorides, providing the automotive industry with a scientific, reliable, and efficient method for corrosion detection and evaluation.

[0026] The metal coating can be an electroplated chromium layer. This invention provides a targeted corrosion detection method, especially for evaluating the corrosion resistance of chromium-plated parts in environments containing hygroscopic chlorides, thereby further improving the effectiveness of material research and quality control for specific coatings.

[0027] The organic solvent can be selected from one or more of isopropanol, ethanol, methanol, or acetone, and the volume ratio of organic solvent to water in the mixture is 50:50. For example, the organic solvent can be isopropanol, ethanol, methanol, or acetone. The types of organic solvents within the above range have good degreasing and cleaning capabilities, effectively removing grease, dust, and other impurities from the sample surface, ensuring direct contact between the corrosive medium and the coating, and further improving the authenticity and reliability of the test. In addition, the 50:50 volume ratio of organic solvent to water not only ensures thorough cleaning of the sample surface but also avoids the potential adverse effects of excessive use of organic solvents on the environment or the sample itself, achieving a balance between cleaning efficiency and environmental safety. By limiting the type of metal coating and the specific conditions for sample surface pretreatment, the specificity and effectiveness of the detection method are enhanced, and the comparability and universality of the test results are ensured, thus providing the automotive industry with a more reliable and efficient means of detecting and evaluating the corrosion resistance of coatings.

[0028] Furthermore, the hygroscopic chloride is selected from one or more of calcium chloride dihydrate, sodium chloride, potassium chloride, or mixtures thereof. For example, the hygroscopic chloride is calcium chloride dihydrate, sodium chloride, or potassium chloride. Within the scope of this invention, the detection method for hygroscopic chloride can more accurately reflect the corrosion scenarios that the coating may suffer in actual use, improve the reliability and reference value of test results, and also help to establish unified testing standards, reduce result deviations caused by differences in testing conditions, promote the standardization of corrosion detection and evaluation systems within the industry, and through standardized corrosion promoters, test results from different laboratories and at different time periods can be mutually used and compared, providing data support for academic research and industrial applications.

[0029] Furthermore, the pH adjuster is one or more of sodium hydroxide solution and sulfuric acid solution. Within the above-mentioned range, the pH adjuster can precisely adjust the pH value of the test slurry to ensure that it meets the specified range of 7.0±0.5. Precise control can further make the test environment closer to the actual corrosion conditions, thereby improving the accuracy and consistency of the test.

[0030] Furthermore, the soil-based medium is kaolin. Choosing kaolin as the soil-based medium in this invention helps to more effectively simulate the complex composition of soil in real-world environments, especially the fine particles in road slurry. This further helps to more accurately assess the corrosion behavior of the coating under actual service conditions, providing a reliable basis for the corrosion-resistant design of the product. Moreover, it can form a stable suspension system in the test slurry, ensuring uniform contact between the corrosive medium and the coating surface, reducing random errors during the testing process, and improving the predictability and repeatability of corrosion test results.

[0031] Furthermore, in the preparation of the corrosive medium stock solution, a 0.25 N sodium hydroxide solution is used as the pH adjuster. Using a 0.25 N sodium hydroxide solution as a standardized pH adjuster allows for more effective and precise adjustment of the pH value of the test slurry to the target range, i.e., 7.0 ± 0.5. Precise pH control helps ensure the consistency and repeatability of the corrosion testing environment, thereby obtaining more reliable corrosion data.

[0032] Furthermore, in the preparation of the test slurry, 3 g of kaolin is mixed with every 5 mL of the stock solution. Using the specific mixing ratio of this invention stabilizes the physical properties of the test slurry, including viscosity and suspension, ensuring that the corrosive medium uniformly covers and adheres to the coating surface during the test. It also ensures that the composition of the test slurry prepared for each test is consistent, thereby further improving the repeatability and reliability of the test results.

[0033] Furthermore, accelerated corrosion testing involves placing samples within a test chamber, maintaining controlled environmental conditions throughout the testing process until the evaluation point. This causes the metal coating to undergo a faster corrosion process than in natural environments, thus shortening the testing cycle and allowing for the acquisition of information on the material's long-term performance in a shorter time. The controlled environment within the test chamber ensures consistent conditions for each test, improving the consistency and repeatability of test results. This further facilitates the establishment of standardized testing procedures, the comparison of the performance of different coatings, and the reproduction of experimental results. In addition, compared to natural corrosion testing, accelerated testing within a test chamber reduces the time spent observing corrosion phenomena and lowers the cost of maintaining long-term outdoor testing sites, thereby improving economic efficiency.

[0034] Furthermore, the corrosion assessment also includes removing the sample from the test chamber, wiping the sample to remove the test slurry, and evaluating each area where the test slurry was removed.

[0035] Furthermore, the storage period for the stock solution is one month, and the storage period for the test slurry is 12 hours. Using these storage periods for the stock solution and test slurry ensures their chemical activity and stability, improves the accuracy and efficiency of testing, optimizes resource utilization, simplifies operational procedures, ensures standardized testing and safe laboratory management, and more effectively lays the foundation for the effective implementation of accelerated corrosion detection and the establishment of industry standards.

[0036] The present application will be further described in detail below with reference to specific embodiments. The embodiments should not be construed as limiting the scope of protection claimed in this application.

[0037] Test instruments

[0038] The testing apparatus consists of an environmental chamber capable of controlling temperature and humidity within specified ranges. The chamber is large enough to accommodate the test samples without them contacting each other or the chamber walls. The chamber maintains the test sample environment at a temperature of 60±3°C and a relative humidity of 23±5%. Reaction products formed on one sample do not transfer to another. The test sample does not affect the corrosivity of the test environment, nor does it affect its own corrosivity by the test environment.

[0039] Reagents and materials

[0040] Table 1 below lists the laboratory-grade consumables used in the experiment.

[0041] Table 1

[0042]

[0043] Preparation of corrosive media stock solutions

[0044] Stock Solution – Using the consumables listed in Table 1, dissolve 57.5 g of calcium chloride dihydrate in 94 mL of water and 8 mL of 0.25 N NaOH solution to prepare a stock solution containing dissolved calcium chloride. The pH of the solution is 9.5 ± 0.5. If the pH of the solution is outside this range, investigate the possibility of contaminated or low-purity consumables.

[0045] Test slurry preparation

[0046] Test slurry - Using the consumables listed in Table 1, mix the stock solution and kaolin at a ratio of 3 g kaolin per 5 mL of stock solution.

[0047] Take 10 mL of the test slurry and dilute it with an equal volume of water. Measure the pH of the diluted test slurry using a calibrated digital pH meter. The pH of the diluted test slurry should be 7.0 ± 0.5. If the pH of the diluted test slurry is not within the range of 7.0 ± 0.5, titrate with a standard sodium hydroxide or sulfuric acid solution until the desired pH is obtained.

[0048] The stock solution has a shelf life of 1 month. The test slurry has a shelf life of 12 hours.

[0049] The standard test method for preparing a stock solution sufficient to last for one month and then conducting a chloride resistance test on chrome-plated parts.

[0050] Corrosion Acceleration Detection Procedure

[0051] Select high-priority automotive components for sample preparation. Clean the sample using a non-abrasive cloth soaked in a 50:50 volume ratio mixture of isopropanol and water. Ensure the chrome-plated part is completely dry before proceeding.

[0052] Using a pipette or dropper, apply approximately 0.6 mL of the test slurry to a circular dot at each designated location. Apply the solution to the center of the dot and allow it to spread naturally. No manual application is necessary after the test slurry has been applied to the surface. Space each dot at least 1 cm apart from the others in all directions. If there is sufficient space at any location, apply up to three replicates to observe potential variability in the test results.

[0053] The samples are placed in a test chamber with a temperature controlled at 60±3°C and a relative humidity of 23±5%, so that the test slurry is as horizontal as possible, so that the test slurry does not flow from one sample to another, and each sample is fully exposed to the test environment without interfering with each other.

[0054] Corrosion assessment

[0055] Before the test begins, the applicant and the laboratory must specify and agree on the test duration, minimum number of test sites, evaluation frequency, and test results.

[0056] At each evaluation interval, remove the specimen from the test chamber and close the chamber. Wipe the test slurry at the circular spot on each specimen with hot tap water and a clean, non-abrasive cloth. Evaluate each area where the test slurry was removed under 10x magnification. Score each circular spot according to the grades in Table 2 below. The applicant specifies the acceptance criteria for the evaluation. Continue testing in the controlled chamber until the next inspection interval or the end of the test.

[0057] The total time for daily inspections of the test chamber shall not exceed 60 minutes. An inspection shall be conducted once daily.

[0058] After each evaluation, records of the test evaluation points are saved by marking the samples and taking photos.

[0059] Records and reports

[0060] Unless the applicant and the laboratory reach a prior agreement, the test report shall include the following information:

[0061] (I) Identification of the sample and its source, including the electroplating cycle and source.

[0062] (1) Electroplating cycle, including the thickness and type of chromium layer.

[0063] (2) Identification of plating before and after chromium plating (if applicable).

[0064] (II) Temperature and relative humidity of the test chamber.

[0065] (III) The frequency of the assessment, including the time interval.

[0066] (IV) Photographs of the test sites after each assessment.

[0067] (V) The test results were evaluated using the following Table 2.

[0068] Table 2 Grades of Chromium Loss During Accelerated Corrosion Tests

[0069]

[0070] As can be seen from the above description, the method of this invention effectively simulates the corrosive effect of a thin film containing hygroscopic chlorides and solid materials (kaolin) on electroplated chromium parts in the laboratory (chromium plating parts chloride slurry resistance test). This standardized testing method can be effectively used to test samples, establishing a standardized testing method to regulate acceptance, simulate service evaluation, manufacturing control, and research and development.

[0071] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for accelerating corrosion detection of metal coatings, characterized in that, Includes the following steps: The sample surface was pretreated by cleaning the sample surface with a mixture of organic solvent and water; Preparation of a corrosive media stock solution, the corrosive media stock solution comprising a hygroscopic chloride, a pH adjuster and water, wherein the pH of the stock solution is in the range of 9.5 ± 0.5 and is used to form a test slurry; The test slurry was prepared by mixing the soil-based medium with the reserve solution to form the test slurry. After a portion of the test slurry was mixed with an equal volume of water, the pH value of the resulting diluted test slurry was within the range of 7.0 ± 0.

5. Corrosion acceleration testing was performed under controlled environmental conditions, with the sample surface in contact with the test slurry at a temperature range of 60±3°C and a relative humidity range of 23±5% to expose the sample to corrosion. as well as The degree of corrosion is assessed by evaluating the corrosion level of the sample at specified time intervals according to a pre-set standard rating scale.

2. The method for accelerating corrosion detection of metal coatings according to claim 1, characterized in that, The metal plating is an electroplated chromium layer; and / or The organic solvent is selected from one or more of isopropanol, ethanol, methanol or acetone, and the volume ratio of the organic solvent to water in the mixture is 50:

50.

3. The method for accelerating corrosion detection of metal coatings according to claim 1, characterized in that, The hygroscopic chloride is one or more selected from calcium chloride dihydrate, sodium chloride, potassium chloride, or mixtures thereof.

4. The method for accelerating corrosion detection of metal coatings according to claim 3, characterized in that, The pH adjuster is one or more of sodium hydroxide solution and sulfuric acid solution.

5. The method for accelerating corrosion detection of metal coatings according to claim 1, characterized in that, The soil base medium is kaolin.

6. The method for accelerating corrosion detection of metal coatings according to claim 4, characterized in that, In the preparation of the corrosive medium reserve solution, the pH adjuster is a 0.25 N sodium hydroxide solution.

7. The method for accelerating corrosion detection of metal coatings according to claim 1, characterized in that, In the preparation of the test slurry, 5 mL of the stock solution was mixed with 3 g of kaolin.

8. The method for accelerating corrosion detection of metal coatings according to claim 1, characterized in that, The accelerated corrosion detection involves placing the sample in a test chamber and maintaining the environmental control conditions throughout the detection process until the evaluation time point.

9. The method for accelerating corrosion detection of metal coatings according to claim 8, characterized in that, The corrosion assessment also includes removing the sample from the test chamber, wiping the sample to remove the test slurry, and assessing each area where the test slurry was removed.

10. The method for accelerating corrosion detection of metal coatings according to claim 1, characterized in that, The storage solution has a shelf life of 1 month, and the test slurry has a shelf life of 12 hours.

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