Method for evaluating outdoor service life of coating

Abstract

A method for evaluating the outdoor service life of a coating. The method comprises the following steps: calculating an ultraviolet irradiation equivalent of a coating during ultraviolet aging and a t

Description

Evaluation method for outdoor service life of coatings Technical Field

[0001] The present invention relates to the technical field of coating evaluation in reliability engineering, and in particular to a method for evaluating the service life of an outdoor coating. Background Art

[0002] After being applied to an object and drying and hardening, paint forms a tough and somewhat elastic covering layer, or coating, on the surface, providing protection and / or decoration. Coatings used outdoors are exposed to the outdoor atmosphere and are subject to wind, sun, rain, salt spray corrosion, and temperature fluctuations. Under the long-term and repeated effects of these external natural environments, the coating is prone to aging phenomena such as cracking, powdering, flaking, and discoloration, causing the coating to lose its original decorative and protective functions. Therefore, in engineering applications, during the design and selection phase, outdoor coatings need to be subjected to aging tests based on specific usage requirements to determine their resistance to environmental aging and even to evaluate and predict their service life.

[0003] Currently, there are two main methods for assessing material aging lifespan: natural aging testing and laboratory accelerated aging testing using artificial climates. Natural aging testing involves direct exposure to the natural environment, truly reflecting the environmental conditions to which the material is subjected. The resulting test results are accurate and reliable, but the testing cycle is long, often requiring several years or even decades. Laboratory accelerated aging testing uses a test chamber to simulate the effects of the natural environment. While accelerated aging testing can yield results in a shorter timeframe, it often fails to correspond to the actual use environment and cannot accurately reflect the full impact of environmental factors.

[0004] Therefore, how to establish an equivalent correspondence between the natural aging environment and the laboratory accelerated aging environment and use the laboratory accelerated aging method to quickly evaluate the long-term natural aging performance of outdoor coatings has become an urgent problem that needs to be solved.

[0005] Summary of the Invention

[0006] In view of this, in order to overcome the defects of the prior art and achieve the above-mentioned purpose, the purpose of the present invention is to provide a method for evaluating the service life of outdoor coatings.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for evaluating the outdoor service life of a coating comprises the following steps:

[0009] Calculate the UV radiation equivalent of the coating in UV aging and the temperature and humidity aging equivalent in wet heat accelerated aging for each of the twelve months of the year;

[0010] The accelerated aging test conditions are set according to the ultraviolet radiation equivalent and temperature and humidity aging equivalent of each month, and one year is a cycle unit, one month is a stage, and each cycle unit includes twelve stages within a year;

[0011] After each cycle unit aging, the adhesion of the coating is measured, and the test results of the adhesion are fitted to obtain the service life of the outdoor coating failure.

[0012] According to some preferred embodiments of the present invention, the calculation of the UV radiation equivalent of the coating during outdoor UV aging comprises the following steps:

[0013] Query the monthly UV radiation amount in the target area from 1 to 12 months of a year i , where i = 1, 2, 3, ..., 12;

[0014] Carry out UV accelerated aging in the UV aging box, query the UV irradiation power P of the UV aging box, and calculate the equivalent UV accelerated aging time t per month using formula (1) UVi , so the monthly UV radiation equivalent is (P,t UVi ), where i = 1, 2, 3, ..., 12;

[0015] According to some preferred embodiments of the present invention, the calculation of the temperature and humidity aging equivalent of the coating in the damp heat accelerated aging comprises the following steps:

[0016] The aging time of damp heat accelerated aging is calculated according to formula (2):

[0017] Where: K is the time acceleration coefficient; t1 and t2 are the laboratory hygrothermal aging and natural aging times, respectively; T1 and T2 are the hygrothermal aging and natural aging temperatures, respectively. and are the humidity of hygrothermal aging and natural aging, respectively, and C is the equivalent accelerated aging coefficient;

[0018] Query the average temperature T of the target area from 1 to 12 months in a certain year i and average humidity Where i = 1, 2, 3, ..., 12;

[0019] According to formula (2), the time t required for equivalent accelerated aging under the temperature and humidity corresponding to the target temperature and target relative humidity in each month is calculated. i , so the temperature and humidity aging equivalent of each month is where i = 1, 2, 3, ..., 12; t 设定 and They are the ambient temperature and relative humidity set according to the operating temperature of the coating.

[0020] According to some preferred implementation aspects of the present invention, determining the equivalent accelerated aging coefficient C includes the following steps:

[0021] Preliminary draft C j ;

[0022] Determine the time when the damp heat aging test needs to be carried out, and query the average temperature T of the target area during the test period in the past three years t and average humidity

[0023] Calculate the equivalent time of wet heat aging t according to formula (2) t , and according to the maximum operating temperature and humidity of the coating design and the equivalent time of damp heat aging t t Get the damp heat accelerated aging program;

[0024] Conduct damp heat aging test according to damp heat aging procedure and conduct indoor natural aging test simultaneously;

[0025] After the test, the adhesion of the outdoor coating is tested and the equivalent accelerated aging coefficient C is corrected according to the test results. j , and re-conduct the accelerated aging test;

[0026] When the actual accelerated aging test results are equivalent to the natural aging results, the C j This is the optimal equivalent accelerated aging coefficient C of the outdoor coating.

[0027] According to some preferred embodiments of the present invention, the variation of adhesion over time is shown in formula (3): S = S0 - ωln(1 + θt) (3)

[0028] Where: S is the adhesion after aging time t, S0 is the initial adhesion, ω represents the coating anti-aging ability parameter, and θ is the environmental aging erosion coefficient.

[0029] According to some preferred embodiments of the present invention, data fitting is performed on the coating adhesion test results after each cycle of aging, and the coating anti-aging ability parameter ω and environmental aging corrosion coefficient θ are obtained according to formula (3).

[0030] According to some preferred embodiments of the present invention, the service life of the outdoor coating failure is the fitting equation obtained by fitting the coating adhesion and the minimum adhesion value F specified in the technical requirements for coating failure. f , calculate the service life time T of outdoor coating failure f .

[0031] Due to the adoption of the above technical solution, compared with the existing technology, the benefits of the present invention are: the evaluation method of the outdoor service life of the coating of the present invention establishes a method based on evaluating the service life of the outdoor coating, improves the theoretical basis and means of coating evaluation, and the data is obtained accurately and the results are accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] FIG1 is a correction process of the equivalent acceleration coefficient C of an outdoor coating in a preferred embodiment of the present invention;

[0034] FIG2 shows the change of adhesion of the outdoor coating over time after artificial accelerated aging in a preferred embodiment of the present invention;

[0035] FIG3 shows the change of adhesion of coating A' over time after artificial accelerated aging in a preferred embodiment of the present invention;

[0036] FIG. 4 shows the change of adhesion of coating B' over time after artificial accelerated aging in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0038] Coatings are affected outdoors by factors such as sunlight, rain, temperature and humidity, wind, and salt spray. The most important factors are sunlight (solar radiation) and temperature and humidity. Ultraviolet light has the most significant impact on coating aging. Therefore, when artificially simulating outdoor aging in the laboratory, ultraviolet light and temperature and humidity are selected as environmental factors to accelerate aging.

[0039] The effects of natural environmental changes (such as alternating sunny and rainy days) are reflected by alternating monthly cycles of UV radiation, temperature, and humidity. The UV radiation and temperature and humidity vary greatly over the 12 months of the year, while the annual changes in UV radiation and temperature and humidity are often negligible. Therefore, the coating service life can be evaluated by the degradation effect over 12 months and the aging effect is superimposed on an annual basis. The specific annual aging degradation calculation includes the following steps:

[0040] Step 1: Calculation of UV radiation equivalent for outdoor coatings during UV aging:

[0041] For aging caused by ultraviolet light, it is generally believed that the degree of aging is related to the total amount of radiation. Therefore, in the ultraviolet accelerated aging test, it is sufficient to keep the ultraviolet radiation amount consistent with the ultraviolet radiation amount of natural aging.

[0042] Step 101: Query the UV radiation amount for each month from 1 to 12 months of a certain year i , where i = 1, 2, 3, ..., 12;

[0043] Step 102: UV accelerated aging is performed in a UV aging box. The UV irradiation power P of the UV aging box is queried and the equivalent UV accelerated aging time t per month is calculated using formula (1). UVi , so the monthly UV radiation equivalent is (P,t UVi ), where i = 1, 2, 3, ..., 12.

[0044] Step 2: Calculation of temperature and humidity aging equivalents of outdoor coatings in accelerated aging under damp heat

[0045] For aging caused by temperature and humidity, outdoor coatings mainly experience performance degradation such as hydrolysis and swelling. Heat aging tests can be performed in a high temperature and high humidity environment. The aging time accelerated by heat and humidity can be calculated according to formula (2).

[0046] Where: K is the time acceleration coefficient; t1 and t2 are the laboratory hygrothermal aging and natural aging times, respectively; T1 and T2 are the hygrothermal aging and natural aging temperatures, respectively. and are the humidity of damp heat aging and natural aging respectively, and C is the equivalent accelerated aging coefficient.

[0047] Since the maximum operating temperature of the coating required for the study is 60°C, the environment for accelerated damp heat aging is selected to be 55°C and relative humidity If the maximum operating temperature of other coatings is different, you can choose other set temperatures and relative humidity, or you can fix the set temperature t 设定At 55°C and relative humidity In order to form a unified standard to facilitate the comparison of results.

[0048] Step 201: Confirmation of the equivalent accelerated aging coefficient C of outdoor coating

[0049] The equivalent accelerated aging coefficient C is closely related to the composition and performance of the coating. The equivalent accelerated aging coefficient C of each type of outdoor coating is different to a certain extent. This coefficient has a great influence on the estimated results of the coating. It is necessary to use the staged aging test data collected during the natural service process to correct the equivalent accelerated coefficient. In this way, the aging prediction results obtained are more accurate. The specific steps are as follows:

[0050] Step 2011: First, based on experience, manuals or literature data, preliminarily formulate C j (C j It can be one value or several values);

[0051] Step 2012: Determine the time when the damp heat aging test needs to be carried out, and query the average temperature T of the test period in the past three years in the area based on the information from the meteorological department. t and average humidity

[0052] The three-year trial period here is three full years, that is, each year is from January to December, and cannot cross the year.

[0053] Step 2013: Calculate the damp heat aging equivalent time t according to formula (2) t , that is, the damp heat accelerated aging program is

[0054] Step 2014: According to the damp heat aging procedure Conduct damp heat aging test and indoor natural aging test simultaneously;

[0055] Step 2015: After the test in step 2014, the adhesion of the outdoor coating is tested and the equivalent accelerated aging coefficient C is corrected according to the test results. j , re-carry out the accelerated aging test. When the actual accelerated aging test results are equivalent to the natural aging results, the C j is the optimal equivalent accelerated aging coefficient C of the outdoor coating. The adjustment process of this coefficient is shown in Figure 1.

[0056] The equivalent here means that the difference between the actual accelerated aging test results and the natural aging results is within 5%, usually the adhesion test results.

[0057] Step 202: Query the average temperature T from 1 to 12 months in a certain year i and average humidity Where i = 1, 2, 3, ..., 12.

[0058] Step 203: Calculate the temperature 55°C and relative humidity for each month in step 201 according to formula (2). The time required for accelerated aging after equivalent temperature and humidity t i , so the temperature and humidity aging equivalent of each month is Where i = 1, 2, 3, ..., 12.

[0059] Step 3: Determination of artificial accelerated aging test method

[0060] Based on steps one and two, the natural aging effects of each month are replaced by artificial UV accelerated aging and damp heat accelerated aging. The environmental spectrum of the one-year accelerated aging test is shown in Table 1.

[0061] Step 4: Evaluation of the service life of outdoor coatings

[0062] Step 401: Performing an accelerated aging test on the outdoor coating according to the artificial accelerated aging test environment spectrum in Table 1, where each test cycle lasts for one year, including 12 months;

[0063] Step 402: Coating adhesion is one of the most important properties of a coating. Failure of a coating due to environmental influences mainly starts with electrochemical corrosion at the coating / metal interface, causing the coating to lose all or part of its adhesion. Therefore, measuring the coating adhesion can effectively quantitatively characterize the degree of coating aging.

[0064] During the aging test, the test pieces were taken out regularly for adhesion test in each cycle. The variation of adhesion over time is shown in Figure 2. This variation obeys the Gunyev formula, which can be expressed by formula (3) after simplification: S = S0 - ωln(1 + θt) (3)

[0065] Where: S is the adhesion after aging time t, S0 is the initial adhesion, ω represents the coating anti-aging ability parameter, and θ is the environmental aging erosion coefficient.

[0066] Data fitting is performed on the coating adhesion test results of each cycle in step 401 to obtain the coating anti-aging ability parameter ω and the environmental aging corrosion coefficient θ. ω reflects the coating's inherent anti-aging ability; a larger ω value indicates a lower aging resistance; θ reflects the degree of impact of the simulated environment; a larger θ value indicates a greater impact.

[0067] Step 403: Based on the fitting equation of coating adhesion in step 402 and the minimum adhesion value F specified in the technical requirements for coating failure, f , calculate the service life time T of outdoor coating failuref .

[0068] The technical solution of the present invention is further illustrated below with reference to implementation examples with specific numerical values.

[0069] Example 1

[0070] This implementation case is a coating A' on an outdoor steel plate in Region A. The agreement between Parties A and B requires that the coating adhesion must not be less than 3.5 MPa, and the service life of the coating needs to be evaluated.

[0071] Step 1: Calculate the UV radiation equivalent in the UV accelerated aging test

[0072] The UV irradiation power is 0.60W / m 2 UV aging box for UV aging. Query the UV radiation amount UV in area A every month in the past year i And calculate the equivalent UV accelerated aging time t per month by formula (1) UVi , the results are shown in Table 2:

[0073] Step 2: Calculate the humidity aging equivalent in the damp heat accelerated aging test

[0074] According to the process in Figure 1, after experimental verification and correction, the equivalent accelerated aging parameter C = 87.2. Query the average temperature T of each month in area A over the past year i and average humidity And calculate the corresponding temperature of 55℃ and relative humidity for each month according to formula (2) The time required for accelerated aging after equivalent temperature and humidity t i , the results are shown in Table 3:

[0075] The acceleration times obtained in January and December in Table 3 are too short to be meaningful for the experiment, so they are set to 0.

[0076] Step 3: Determine the artificial accelerated aging test method

[0077] Based on steps one and two, the natural aging effects of each month are replaced by artificial UV accelerated aging and damp heat accelerated aging. The environmental spectrum of the one-year accelerated aging test is shown in Table 4 below:

[0078] The acceleration times obtained in January and December in Table 4 are too short to be meaningful for the experiment, so they are set to 0.

[0079] Step 4: Evaluation of service life

[0080] According to the artificial accelerated aging test environment spectrum in Table 4, the coating A' was subjected to an accelerated aging test. The test cycle was one year, and a total of 6 cycles were carried out. After each cycle, the test piece was taken out for adhesion test, and the test data was fitted with the Gunyev formula, as shown in Figure 3. The curve formula after fitting is Formula 4, and the correlation coefficient R = 0.972. S = 35.29-3.04ln(1+3033.24t) (4)

[0081] Comparing formula (3) and formula (4), we can know that the coating anti-aging ability parameter ω = 3.04, and the environmental aging corrosion coefficient θ = 3033.24.

[0082] According to the agreement between Party A and Party B, the coating adhesion should not be less than 3.5MPa, that is, 35.29-3.04ln(1+3033.24t)≥3.5

[0083] Then t≤11.5

[0084] That is, coating A' can be used for 11.5 years if its adhesion is not less than 3.5 MPa in the natural environment of area A.

[0085] Example 2

[0086] This implementation case is an outdoor concrete-based exterior wall coating B' in area B. The agreement between parties A and B requires that the coating adhesion cannot be less than 2MPa, and the service life of the coating needs to be evaluated.

[0087] Step 1: Calculate the UV radiation equivalent in the UV accelerated aging test

[0088] The UV irradiation power is 0.60W / m 2 UV aging box for UV aging. Query the UV radiation amount UV in area A every month in the past year i And calculate the equivalent UV accelerated aging time t per month by formula (1) UVi , the results are shown in Table 5:

[0089] Step 2: Calculate the humidity aging equivalent in the damp heat accelerated aging test

[0090] According to the process in Figure 1, after experimental verification and correction, the equivalent accelerated aging parameter C = 75.8. Query the average temperature T of each month in area B in the past year i and average humidity And calculate the corresponding temperature of 55℃ and relative humidity for each month according to formula (2) The time required for accelerated aging after equivalent temperature and humidity t i , the results are shown in Table 6:

[0091] The acceleration times obtained in January and December in Table 6 are too short to be meaningful for the experiment, so they are set to 0.

[0092] Step 3: Determine the artificial accelerated aging test method

[0093] Based on steps one and two, the natural aging effects of each month are replaced by artificial UV accelerated aging and damp heat accelerated aging. The environmental spectrum of the one-year accelerated aging test is shown in Table 7 below:

[0094] The acceleration times obtained in January and December in Table 7 are too short and have no experimental significance, so they are set to 0.

[0095] Step 4: Evaluation of service life

[0096] According to the artificial accelerated aging test environment spectrum in Table 7, the coating A' was subjected to an accelerated aging test. The test cycle was one year, and a total of 6 cycles were carried out. After each cycle, the test piece was taken out for adhesion test, and the test data was fitted with the Gunyev formula, as shown in Figure 4. The curve formula after fitting is Formula 5, and the correlation coefficient R = 0.979. S = 29.74-2.86ln(1+1865.52t) (5)

[0097] Comparing formula (3) and formula (5), we can know that the coating anti-aging ability parameter ω = 2.86, and the environmental aging erosion coefficient θ = 1865.52.

[0098] According to the agreement between Party A and Party B, the coating adhesion should not be less than 2MPa, that is, 29.74-2.86ln(1+1865.52t)≥2

[0099] Then t≤8.7

[0100] That is, coating B' can be used for 8.7 years when its adhesion is not less than 2 MPa in the natural environment of area B.

[0101] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for evaluating the outdoor service life of a coating, characterized in that: The steps include: Calculate the UV radiation equivalent of the coating in UV aging and the temperature and humidity aging equivalent in wet heat accelerated aging for each of the twelve months of the year; The accelerated aging test conditions are set according to the ultraviolet radiation equivalent and temperature and humidity aging equivalent of each month, and one year is a cycle unit, one month is a stage, and each cycle unit includes twelve stages corresponding to January to December in a year; After each cycle unit aging, the adhesion of the coating is measured, and the test results of the adhesion are fitted to obtain the service life of the outdoor coating failure.

2. The evaluation method according to claim 1, wherein: The calculation of UV radiation equivalent of coating in outdoor UV aging includes the following steps: Query the monthly UV radiation amount in the target area from 1 to 12 months of a year i , where i = 1, 2, 3, ..., 12; Carry out UV accelerated aging in the UV aging box, query the UV irradiation power P of the UV aging box, and calculate the equivalent UV accelerated aging time t per month using formula (1) UVi , so the monthly UV radiation equivalent is (P,t UVi ), where i = 1, 2, 3, ..., 12; 3. The evaluation method according to claim 1, wherein: The calculation of the temperature and humidity aging equivalent of the coating in the damp heat accelerated aging includes the following steps: The aging time of damp heat accelerated aging is calculated according to formula (2): Where: K is the time acceleration coefficient; t1 and t2 are the laboratory hygrothermal aging and natural aging time, T1 and T2 are the hygrothermal aging and natural aging temperatures, respectively. and are the humidity of hygrothermal aging and natural aging, respectively, and C is the equivalent accelerated aging coefficient; Query the average temperature T of the target area from 1 to 12 months in a certain year i and average humidity Where i = 1, 2, 3, ..., 12; According to formula (2), the time t required for equivalent accelerated aging under the temperature and humidity corresponding to the target temperature and target relative humidity in each month is calculated. i , so the temperature and humidity aging equivalent of each month is where i = 1, 2, 3, ..., 12; t 设定 and They are the ambient temperature and relative humidity set according to the operating temperature of the coating.

4. The evaluation method according to claim 3, wherein: The coating is designed to have a maximum operating temperature of 60°C, and the environment selected for accelerated damp heat aging is 55°C and relative humidity Constant temperature and humidity environment.

5. The evaluation method according to claim 1, wherein: The determination of the equivalent accelerated aging coefficient C includes the following steps: Preliminary draft C j ; Determine the time when the damp heat aging test needs to be carried out, and query the average temperature T of the target area during the test period in the past three years t and average humidity Calculate the equivalent time of wet heat aging t according to formula (2) t , and according to the maximum operating temperature and humidity of the coating design and the equivalent time of damp heat aging t t Get the damp heat accelerated aging program; Conduct damp heat aging test according to damp heat aging procedure and conduct indoor natural aging test simultaneously; After the test, the adhesion of the outdoor coating is tested and the equivalent accelerated aging coefficient C is corrected according to the test results. j , and re-conduct the accelerated aging test; When the actual accelerated aging test results are equivalent to the natural aging results, the C j This is the optimal equivalent accelerated aging coefficient C of the outdoor coating.

6. The evaluation method according to claim 5, characterized in that The equivalent is that the difference between the actual accelerated aging test results and the natural aging results is within 5%.

7. The evaluation method according to claim 5, characterized in that The past three years refer to January to December of each year in the past three years.

8. The evaluation method according to claim 5, characterized in that The C j It is preliminarily formulated based on experience, manuals or literature data.

9. The evaluation method according to claim 1, wherein: The variation of adhesion with time is shown in formula (3): S=S0-ωln(1+θt) (3) Where: S is the adhesion after aging time t, S0 is the initial adhesion, ω represents the coating anti-aging ability parameter, and θ is the environmental aging erosion coefficient.

10. The evaluation method according to claim 9, characterized in that: The coating adhesion test results after each aging cycle are fitted, and the coating anti-aging ability parameter ω and environmental aging corrosion coefficient θ are obtained according to formula (3).

11. The evaluation method according to claim 10, characterized in that: The service life of outdoor coating failure is the fitting equation obtained based on the coating adhesion and the minimum adhesion value F specified in the technical requirements for coating failure. f , calculate the service life time T of outdoor coating failure f .

Images