GB2631629A - Method for evaluating outdoor service life of coating - Google Patents
Method for evaluating outdoor service life of coating Download PDFInfo
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- GB2631629A GB2631629A GB2413974.3A GB202413974A GB2631629A GB 2631629 A GB2631629 A GB 2631629A GB 202413974 A GB202413974 A GB 202413974A GB 2631629 A GB2631629 A GB 2631629A
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- G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N19/04—Measuring adhesive force between materials, e.g. of sealing tape, of coating
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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 temperature and humidity aging equivalent of the coating during hygrothermal accelerated aging in each month of twelve months of one year; setting a condition for an accelerated aging test on the basis of the ultraviolet irradiation equivalent and the temperature and humidity aging equivalent in each month, taking one year as a cycle unit, and taking each month as one stage, wherein each cycle unit, i.e. one year, comprises twelve stages; and after the aging in each cycle unit ends, measuring an adhesive force of the coating, performing data fitting on a test result of the adhesive force, and thereby obtaining a service life time when the outdoor coating fails. A method for evaluating the service life of an outdoor coating is established, the theoretical basis and means for coating evaluation are improved, the data is accurately obtained, and a result is accurate.
Description
EVALUATION METHOD OF OUTDOOR SERVICE LIFE OF COATING
TECHNICAL FIELD
[0001] The present invention relates to the field of coating evaluation technologies in reliability engineering, and specifically, to an evaluation method of a service life of an outdoor coating.
BACKGROUND
[0002] After a coating material is applied to a surface of an object and dried and hardened, a tough and elastic covering layer formed on the surface of the object is a coating, which provides the object with protection and/or decoration. A coating used outdoors is exposed to outdoor atmospheric environments and needs to withstand effects such as wind blowing, sun exposure, raining, salt-spray corrosion, and temperature fluctuation. Under the long-term repeated action of these external natural environments, aging phenomena such as cracking, powdering, peeling, and discoloration are prone to occur on the coating, causing the coating to lose original decorative and protective functions. Therefore, in engineering application, an aging test needs to be performed on an outdoor coating in a design and selection phase according to a specific use requirement, to determine environmental aging resistance of the outdoor coating, and even evaluate and predict a service life of the outdoor coating. [0003] Currently, there are mainly two methods for evaluating an aging life of a material: One of the two methods is a natural aging test, and the other is a laboratory artificial climate accelerated aging test. The natural aging test refers to direct exposure to a natural environment, and can truly reflect an environmental condition endured by a material, and an obtained test result is accurate and reliable, but a test period is long, which is often several years or even decades. In the laboratory artificial climate accelerated aging test, an experimental box is used to simulate effects of a natural environment, and a test result can be obtained in a short period in the accelerated aging test. However, the laboratory artificial climate accelerated aging test often cannot correspond to an actual use environment, and cannot accurately reflect an impact of all environmental factors.
[0004] Therefore, how to establish an equivalent correspondence between a natural aging environment and a laboratory accelerated aging environment, to use a laboratory accelerated aging method to quickly evaluate long-term natural aging performance of an outdoor coating becomes a problem to be resolved urgently.
SUMMARY
[0005] In view of this, to overcome a defect in the conventional technology and achieve the foregoing objective, an objective of the present invention is to provide an evaluation method of a service life of an outdoor coating.
[0006] To achieve the foregoing objective, the following technical solutions are used in the present invention.
[0007] An evaluation method of an outdoor service life of a coating is provided, and includes the following steps: [0008] calculating, for the coating, an ultraviolet irradiation equivalent in ultraviolet aging and a temperature-humidity aging equivalent in hygrothermal accelerated aging for each of twelve months of one year; [0009] setting an accelerated aging test condition based on the ultraviolet irradiation equivalent and the temperature-humidity aging equivalent of each month, and taking a year as a cycle unit and each month as a phase, where each cycle unit year includes twelve phases; and [0010] measuring adhesion of the coating after aging of each cycle unit is completed, and performing data fitting on a test result of the adhesion, to obtain a service life of an outdoor coating.
[0011] According to some preferred implementation aspects of the present invention, calculation of the ultraviolet irradiation equivalent of the coating in outdoor ultraviolet aging includes the following steps: [0012] querying an ultraviolet irradiation quantity UV; of a target region for each of January to December in a specific year, where i=1, 2, 3, ..., or 12; and [0013] performing ultraviolet accelerated aging in an ultraviolet aging box, querying an ultraviolet irradiation power P of the ultraviolet aging box, and calculating an equivalent ultraviolet accelerated aging time tuvi of each month according to Formula (1), to obtain the ultraviolet irradiation equivalent (P, tuvi) of each month, where i=1, 2, 3, ..., or 12; uvi tuvi = P (1).
[0014] According to some preferred implementation aspects of the present invention, calculation of the temperature-humidity aging equivalent of the coating in hygrothermal accelerated aging includes the following steps: [0015] calculating an aging effect time of hygrothermal accelerated aging according to Formula (2):
--
t2 e-c/crt(pt,
K
e-cm292) (2) [0016] where in the formula, K is a time acceleration coefficient, ti and t2 are respectively a laboratory hygrothermal aging time and a natural aging time, Ti and T2 are a hygrothermal aging temperature and a natural aging temperature, (pi and cp2 are respectively hygrothermal aging humidity and natural aging humidity, and C is an equivalent accelerated aging coefficient; [0017] querying an average temperature Ti and average humidity pi of a target region for each of January to December in a specific year, where i=1, 2, 3, ..., or 12; and [0018] calculating, according to Formula (2), a time t required for accelerated aging after equivalent at a target temperature and target relative humidity that correspond to each month, to obtain the temperature-humidity aging equivalent if setting+(setting, ti) of each month, where i=1, 2, 3, ..., or 12, and setting and 9setting are respectively an environmental temperature and relative humidity that are set based on a service temperature of the coating.
[0019] According to some preferred implementation aspects of the present invention, determining of an equivalent accelerated aging coefficient C includes the following steps: [0020] preliminarily determining Ci; [0021] determining a time when a hygrothermal aging test needs to be performed, and querying an average temperature Tt and average humidity (pt of test periods in the past three years in a target region; [0022] calculating a hygrothermal aging equivalent time tt according to Formula (2), and obtaining a hygrothermal accelerated aging program based on highest service temperature and humidity designed for the coating and the hygrothermal aging equivalent time tt; [0023] performing the hygrothermal aging test according to the hygrothermal aging program, and simultaneously performing an indoor natural aging test; and [0024] performing an adhesion test on the outdoor coating after the tests are completed, synchronously correcting the equivalent accelerated aging coefficient Cl according to a test result, and performing an accelerated aging test again; wherein [0025] when an actual accelerated aging test result is equivalent to a natural aging result, obtained Ci is an optimal equivalent accelerated aging coefficient C of the outdoor coating.
[0026] According to some preferred implementation aspects of the present invention, a temporal variation rule of the adhesion is shown in Formula (3), S = So -win(1 + Ot) (3) [0027] where in the formula, S is adhesion after aging is performed for a time t, So is initial adhesion, w represents an aging resistance parameter of the coating, and B is an environmental aging erosion coefficient.
[0028] According to some preferred implementation aspects of the present invention, data fitting is performed on the test result of the adhesion of the coating obtained after aging of each cycle period, and the aging resistance parameter (A) and the environmental aging erosion coefficient 8 of the coating are obtained according to Formula (3).
[0029] According to some preferred implementation aspects of the present invention, the service life of the outdoor coating is a service life Tf of the outdoor coating that is calculated according to a fitting equation obtained by fitting the adhesion of the coating and according to a value Ff of lowest adhesion specified in a coating failure technical requirement.
[0030] Compared with the conventional technology, the present invention has the following beneficial effects because of using the foregoing technical solutions: According to the evaluation method of an outdoor service life of a coating in the present invention, an evaluation method of a service life of an outdoor coating is established, theoretical basis and means of coating evaluation are improved, and precise data and an accurate result are obtained.
BRIEF DESCRIPTION OF DRAWINGS
[0031] To describe the technical solutions in embodiments of the present invention more clearly, accompanying drawings required for describing the embodiments are briefly described below. Obviously, the accompanying drawings in the following description show merely some embodiments of the present invention, and a person of ordinary skill in the art can further derive other accompanying drawings from these accompanying drawings without creative efforts.
[0032] FIG. 1 shows a correction procedure of an equivalent acceleration coefficient C of an outdoor coating according to a preferred embodiment of the present invention; [0033] FIG. 2 shows a temporal variation rule of adhesion of an outdoor coating after artificial accelerated aging according to a preferred embodiment of the present invention; [0034] FIG. 3 shows a temporal variation rule of adhesion of a coating A' after artificial accelerated aging according to a preferred embodiment of the present invention; and [0035] FIG. 4 shows a temporal variation rule of adhesion of a coating B' after artificial accelerated aging according to a preferred embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
[0036] To enable a person skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are merely some rather than all of the embodiments of the present invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0037] A coating is affected by factors such as sun exposure, raining, a temperature and humidity, wind blowing, and salt spray outdoors, where main factors are sun exposure (solar irradiation) as well as the temperature and the humidity. Ultraviolet light has the most significant impact on coating aging in sunlight. Therefore, when outdoor aging is artificially simulated in a laboratory, ultraviolet light as well as the temperature and the humidity are selected as environmental factors for accelerated aging.
[0038] Alternative and cyclical changes are performed monthly based on the ultraviolet light as well as the temperature and the humidity to reflect an impact of natural environment changes (for example, alternation of sunny and rainy days). An ultraviolet irradiation quantity as well as the temperature and the humidity change greatly in each of 12 months of a year, but for each year, changes in an ultraviolet irradiation quantity as well as the temperature and the humidity are often negligible. Therefore, a service life of a coating may be evaluated through a degradation effect of 12 months, and an impact of aging is superimposed in the unit of year. Specific annual aging and degradation calculation includes the following steps.
[0039] Step 1: Calculation of an ultraviolet irradiation equivalent of an outdoor coating in ultraviolet aging [0040] For aging caused by ultraviolet light, it is usually believed that a degree of aging is related to a total irradiation quantity. Therefore, an ultraviolet irradiation quantity in an ultraviolet accelerated aging test only needs to be consistent with that in natural aging. [0041] Step 101: Query an ultraviolet irradiation quantity UVi for each of January to December in a specific year, where i=1, 2, 3, ..., or 12.
[0042] Step 102: Perform ultraviolet accelerated aging in an ultraviolet aging box, query an ultraviolet irradiation power P of the ultraviolet aging box, and calculate an equivalent ultraviolet accelerated aging time tuvi of each month according to Formula (1), to obtain the ultraviolet irradiation equivalent (P, tuvi) of each month, where i=1, 2, 3, ..., or 12. UVi
tUVi = p (1) [0043] Step 2: Calculation of a temperature-humidity aging equivalent of the outdoor coating in hygrothermal accelerated aging [0044] For aging caused by a temperature and humidity, the outdoor coating mainly suffers from performance declines such as hydrolysis and swelling, and a heated aging test may be selected to be performed in a high-temperature and high-humidity environment. An effect time of hygrothermal accelerated aging may be calculated according to Formula (2).
-c/(Ti(pi) ce_ /(T29 2) K --e (2) [0045] In the formula, K is a time acceleration coefficient, ti and t2 are respectively a laboratory hygrothermal aging time and a natural aging time, Ti and T2 are a hygrothermal aging temperature and a natural aging temperature, (pi and cp2 are respectively hygrothermal aging humidity and natural aging humidity, and C is an equivalent accelerated aging coefficient.
[0046] Since a highest service temperature designed for a coating required for study is 60°C, an environment selected for accelerated hygrothermal aging is a constant temperature and humidity environment with a temperature of 55°C and relative humidity cp of 95%. If a highest service temperature designed for another coating is different, other setting temperature and setting relative humidity may be selected, or the setting temperature +.
setting may be fixed to 55°C and the setting relative humidity (Netting may be fixed to 95%, to form a uniform standard for ease of result comparison.
[0047] Step 201: Determine an equivalent accelerated aging coefficient C of the outdoor coating.
[0048] The equivalent accelerated aging coefficient C is closely related to composition and performance of the coating, and equivalent accelerated aging coefficients C of various types of outdoor coatings are different. This coefficient has a great impact on a prediction result of the coating. It is necessary to use phased aging test data collected in a natural service process to correct an equivalent acceleration coefficient. In this way, a more accurate aging prediction result is obtained. Specific steps are as follows: [0049] Step 2011: Preliminarily determine CI (CI may be a value, or may be several values) according to experience, a manual, or literature data.
[0050] Step 2012: Determine a time when a hygrothermal aging test needs to be performed, and query an average temperature Tt and average humidity pt of test periods in the past three years in a region according to information from a meteorological department.
[0051] The test periods of three years herein indicate three full years, which means that each year spans from January to December without crossing over into a next year. [0052] Step 2013: Calculate a hygrothermal aging equivalent time tt according to Formula (2), to obtain a hygrothermal accelerated aging program (55°C-Fp95%, tt). [0053] Step 2014: Perform the hygrothermal aging test according to the hygrothermal aging program (55°C+w95%, tt), and simultaneously perform an indoor natural aging test.
[0054] Step 2015: Perform an adhesion test on the outdoor coating after the tests in step 2014 are completed, synchronously correct the equivalent accelerated aging coefficient Ci according to a test result, and perform an accelerated aging test again. When an actual accelerated aging test result is equivalent to a natural aging result, obtained Ci is an optimal equivalent accelerated aging coefficient C of the outdoor coating. An adjustment procedure of the coefficient is shown in FIG. 1.
[0055] The equivalent herein means that the actual accelerated aging test result differs from the natural aging result by less than 5%, the result is usually the test result of the adhesion.
[0056] Step 202: Query an average temperature Ti and average humidity pi for each of January to December in a specific year, where i=1, 2, 3, ..., or 12.
[0057] Step 203: Calculate, according to Formula (2), a time t required for accelerated aging after equivalent at the temperature of 55°C and the relative humidity cp of 95% that correspond to each month in step 201, to obtain the temperature-humidity aging equivalent of each month (55°C+05%, ti), where i=1, 2, 3, ..., or 12.
[0058] Step 3: Determining of an artificial accelerated aging test method [0059] Based on step 1 and step 2, a natural aging effect of each month is replaced by artificial ultraviolet accelerated aging and hygrothermal accelerated aging. An environmental spectrum of a one-year accelerated aging test is shown in Table 1.
Table 1 Environmental spectrum of an artificial accelerated aging test for the outdoor coating Accelerated tests in phase i Where Ultraviolet accelerated aging Hygrothermal accelerated aging Test device parameters Irradiation power P Temperature and humidity 55°C+p95% Each phase [hour] Irradiation equivalent time tuvi Equivalent acceleration time ti Note: 1. i = 1, 2, 3, ..., or 12 (A year is taken as a unit, each month is one phase, and there are 12 phases in total).
2. A natural aging effect in each phase is simulated through ultraviolet accelerated aging and hygrothermal accelerated aging.
3. An annual aging effect is a superposed sum of effects of the 12 phases.
[0060] Step 4: Evaluation of a service life of the outdoor coating [0061] Step 401: Perform an accelerated aging test on the outdoor coating according to the environmental spectrum of the artificial accelerated aging test in Table 1, where each test cycle period is one year, which includes 12 months.
[0062] Step 402: The adhesion of the coating is one of the most important properties of various properties of the coating. Failure and damage of the coating that are caused under the environmental action mainly start from electrochemical corrosion occurring on a coating/metal interface, causing the coating to lose the adhesion either completely or partially. Therefore, measuring the adhesion of the coating may effectively quantitatively represent a degree of aging of the coating.
[0063] In an aging test process, a test piece is taken out periodically for the adhesion test in each cycle period. A temporal variation rule of the adhesion is shown in FIG. 2. This variation rule is subject to a Gunyev's formula, and may be expressed by Formula (3) after simplification: S = So -(An(1 + Ot) (3) [0064] In the formula, S is adhesion after aging is performed for a time t, So is initial adhesion, w represents an aging resistance parameter of the coating, and e is an environmental aging erosion coefficient.
[0065] Data fitting is performed on the test result of the adhesion of the coating in each period in step 401 to obtain the aging resistance parameter w and the environmental aging erosion coefficient 6 of the coating. w reflects aging resistance of the coating. A larger value of w indicates worse aging resistance of the coating. e reflects a degree of an impact of a simulated environment. A larger value of 0 indicates a larger degree of impact.
[0066] Step 403: Calculate a service life Tf of the outdoor coating according to a fitting equation of the adhesion of the coating in step 402 and a value Ff of lowest adhesion specified in a coating failure technical requirement.
[0067] The following further describes the technical solutions of the present invention by using implementation cases with specific values.
[0068] Embodiment 1 [0069] This implementation case relates to a steel plate-based outdoor coating A' in a region A. Both parties agree that adhesion of the coating shall not be less than 3.5 MPa, and a useful life of the coating needs to be evaluated.
[0070] Step 1: Calculation of an ultraviolet irradiation equivalent in an ultraviolet accelerated aging test [0071] Ultraviolet aging is performed in an ultraviolet aging box with an ultraviolet irradiation power of 0.60 W/m2. An ultraviolet irradiation quantity UVi of each month in the past year in the region A is queried, and an equivalent ultraviolet accelerated aging time tuvi of each month is calculated according to Formula (1). For a result, refer to Table 2.
Table 2 Ultraviolet accelerated aging test parameter table Month January February March April May June Ultraviolet irradiation quantity of each month UViNV/m2 5.85 10.13 16.73 19.86 22.17 23.61 Equivalent ultraviolet aging time tuvi/h 9.75 16.88 27.88 33.1 36.95 39.35 Month July August September October November December Ultraviolet irradiation quantity of each month UVIW/m2 25.83 24.15 20.06 13.55 9.11 5.28 Equivalent ultraviolet aging time tuvi/h 43.05 40.25 33.43 22.58 15.18 8.8 Note: The ultraviolet aging box with the ultraviolet irradiation power of 0.6 W/m2 is used.
[0072] Step 2: Calculation of a humidity aging equivalent in a hygrothermal accelerated aging test [0073] After test verification and correction are performed according to the procedure in FIG. 1, an equivalent accelerated aging parameter C is equal to 87.2. An average temperature Ti and average humidity pi of each month in the past year in the region A are queried, and a time ti required for accelerated aging after equivalent at a temperature of 55°C and relative humidity cp of 95% that correspond to each month is calculated according to Formula (2). For a result, refer to Table 3.
Table 3 Hygrothermal accelerated aging test parameter table Month January February March April May June Average temperature Ti/°C 5 8 13 19 22 25 Average humidity pi 67% 53% 60% 73% 75% 81% Acceleration time t/h 0.00 0.05 0.06 7.11 20.01 51.52 Acceleration coefficient K 38003770853.5 12876.7 13501.9 101.3 37.2 14.0 Month July August September October November December Average temperature Ti/°C 29 29 24 19 12 8 Average humidity pi 84% 79% 77% 86% 81% 76% Acceleration time ti/h 110.09 87.77 34.11 19.00 0.49 0.00 Acceleration coefficient Ki 6.8 8.5 21.1 39.2 1483.7 319082.7 [0074] In Table 3, the acceleration time obtained for January and December is excessively short, resulting in no significance of testing. Therefore, the acceleration time obtained for January and December is set to 0.
[0075] Step 3: Determining of an artificial accelerated aging test method [0076] Based on step 1 and step 2, a natural aging effect of each month is replaced by artificial ultraviolet accelerated aging and hygrothermal accelerated aging. An environmental spectrum of a one-year accelerated aging test is shown in Table 4.
Table 4 Environmental spectrum of the artificial accelerated aging test Phase i 1 2 3 4 5 6 Ultraviolet acceleration time tuvi/h 9.75 16.88 27.88 33.1 36.95 39.35 Hygrothermal acceleration time ti/h 0.00 0.05 0.06 7.11 20.01 51.52 Phase i 7 8 9 10 11 12 Ultraviolet acceleration time tuvi/h 43.05 40.25 33.43 22.58 15.18 8.8 Hygrothermal acceleration time ti/h 110.09 87.77 34.11 19.00 0.49 0.00 Note: 1. In each phase, there are two steps: ultraviolet accelerated aging and hygrothermal accelerated aging.
2. An ultraviolet aging irradiation power is 0.60 W/m2, and a temperature and humidity for hygrothermal aging are 55°C+9=95%.
[0077] In Table 4, the acceleration time obtained for January and December is excessively short, resulting in no significance of testing. Therefore, the acceleration time obtained for January and December is set to 0.
[0078] Step 4: Service life evaluation [0079] An accelerated aging test is performed on the coating A' according to the environmental spectrum of the artificial accelerated aging test in Table 4. A test period is one year. The test is performed for six periods in total. After the test of each period, a test piece is taken out for an adhesion test. Test data is fitted according to a Gunyev's formula, as shown in FIG. 3. A curve formula after fitting is Formula 4 and a correlation coefficient R is equal to 0.972.
S = 35.29 -3.041n(1 + 3033.24t) (4) [0080] It may be learned from comparison between Formula (3) and Formula (4) that, for the coating, an aging resistance parameter w is equal to 3.04 and an environmental aging erosion coefficient B is equal to 3033.24.
[0081] According to the agreement of both parties that the adhesion of the coating shall not be less than 3.5 MPa, 35.29 -3.041n(1 + 3033.24t) > 3.5, and ts11.5.
[0082] That is, the coating A' may be used for 11.5 years when the adhesion is not less than 3.5 MPa in a natural environment of the region A. [0083] Embodiment 2 [0084] This implementation case relates to a concrete-based outdoor wall coating B' in a region B. Both parties agree that adhesion of the coating shall not be less than 2 MPa, and a useful life of the coating needs to be evaluated.
[0085] Step 1: Calculation of an ultraviolet irradiation equivalent in an ultraviolet accelerated aging test [0086] Ultraviolet aging is performed in an ultraviolet aging box with an ultraviolet irradiation power of 0.60 W/m2. An ultraviolet irradiation quantity UVi of each month in the past year in the region A is queried, and an equivalent ultraviolet accelerated aging time tuvi of each month is calculated according to Formula (1). For a result, refer to Table 5.
Table 5 Ultraviolet accelerated aging test parameter table Month January February March April May June Ultraviolet irradiation quantity of each month UV/VV/m2 7.32 15.45 20.37 25.68 32.75 35.13 Equivalent ultraviolet aging time 12.2 25.75 33.95 42.80 54.58 58.55 tuvi/h Month July August September October November December Ultraviolet irradiation quantity of each month UVNV/m 2 40.86 41.51 33.26 26.55 18.71 9.82 Equivalent ultraviolet aging time 68.10 69.18 55.72 44.25 31.18 16.37 tuvi/h Note: The ultraviolet aging box with the ultraviolet irradiation power of 0.6 W/m2 is used.
[0087] Step 2: Calculation of a humidity aging equivalent in a hygrothermal accelerated aging test [0088] After test verification and correction are performed according to the procedure in FIG. 1, an equivalent accelerated aging parameter C is equal to 75.8. An average temperature Ti and average humidity pi of each month in the past year in the region B are queried, and a time t required for accelerated aging after equivalent at a temperature of 55°C and relative humidity p of 95% that correspond to each month is calculated according to Formula (2). For a result, refer to Table 6.
Table 6 Hygrothermal accelerated aging test parameter table Month January February March April May June Average temperature Ti/°C 4 6 14 19 24 28 Average humidity pi 70 60 66 57 67 58 Acceleration time ti/h 0.00 0.00 0.87 2.80 28.47 28.86 Acceleration coefficient Ki 133947111418.5 326793114.8 856.4 256.8 26.1 24.9 Month July August September October November December Average temperature Ti/°C 30 29 25 19 15 8 Average humidity 9i 70 76 69 51 65 66 Acceleration time ti/h 85.90 101.86 37.93 1.27 1.29 0.00 Acceleration coefficient K 8.7 7.3 19.0 585.1 557.6 402456.7 [0089] In Table 6, the acceleration time obtained for January and December is excessively short, resulting in no significance of testing. Therefore, the acceleration time obtained for January and December is set to 0.
[0090] Step 3: Determining of an artificial accelerated aging test method [0091] Based on step 1 and step 2, a natural aging effect of each month is replaced by artificial ultraviolet accelerated aging and hygrothermal accelerated aging. An environmental spectrum of a one-year accelerated aging test is shown in Table 7.
Table 7 Environmental spectrum of the artificial accelerated aging test Phase i 1 2 3 4 5 6 Ultraviolet acceleration time tuvi/h 12.2 25.75 33.95 42.80 54.58 58.55 Hygrothermal acceleration time Uri 0.00 0.00 0.87 2.80 28.47 28.86 Phase i 7 8 9 10 11 12 Ultraviolet acceleration time tuvi/h 68.10 69.18 55.72 44.25 31.18 16.37 Hygrothermal acceleration time ti/h 85.90 101.86 37.93 1.27 1.29 0.00 Note: 1. In each phase, there are two steps: ultraviolet accelerated aging and hygrothermal accelerated aging.
2. An ultraviolet aging irradiation power is 0.60 W/m2, and a temperature and humidity for hygrothermal aging are 55°C+9=95%.
[0092] In Table 7, the acceleration time obtained for January and December is excessively short, resulting in no significance of testing. Therefore, the acceleration time obtained for January and December is set to 0.
[0093] Step 4: Service life evaluation [0094] An accelerated aging test is performed on the coating A' according to the environmental spectrum of the artificial accelerated aging test in Table 7. A test period is one year. The test is performed for six periods in total. After the test of each period, a test piece is taken out for an adhesion test. Test data is fitted according to a Gunyev's formula, as shown in FIG. 4. A curve formula after fitting is Formula 5 and a correlation coefficient R is equal to 0.979.
S = 29.74 -2.861n(1 + 1865.520 (5) [0095] It may be learned from comparison between Formula (3) and Formula (5) that, for the coating, an aging resistance parameter w is equal to 2.86 and an environmental aging erosion coefficient 0 is equal to 1865.52.
[0096] According to the agreement of both parties that the adhesion of the coating shall not be less than 2 MPa, 29.74 -2.861n(1 + 1865.520 > 2, and [0097] That is, the coating B' may be used for 8.7 years when the adhesion is not less than 2 MPa in a natural environment of the region B. [0098] The foregoing embodiments are merely intended to describe the technical concepts and features of the present invention, are intended to enable a person skilled in the art to understand and implement the content of the present invention, and are not intended to limit the protection scope of the present invention. Any equivalent change or modification made in accordance with the present invention shall fall within the protection scope of the present invention.
Claims (11)
- WHAT IS CLAIMED IS: 1. An evaluation method of an outdoor service life of a coating, comprising the following steps: calculating, for the coating, an ultraviolet irradiation equivalent in ultraviolet aging and a temperature-humidity aging equivalent in hygrothermal accelerated aging for each of twelve months of one year; setting an accelerated aging test condition based on the ultraviolet irradiation equivalent and the temperature-humidity aging equivalent of each month, and taking a year as a cycle unit and each month as a phase, wherein each cycle unit year comprises twelve phases corresponding to January to December; and measuring adhesion of the coating after aging of each cycle unit is completed, and performing data fitting on a test result of the adhesion, to obtain a service life of an outdoor coating when the coating fails.
- 2. The evaluation method according to claim 1, wherein calculation of the ultraviolet irradiation equivalent of the coating in outdoor ultraviolet aging comprises the following steps: querying an ultraviolet irradiation quantity UV; of a target region for each of January to December in a specific year, wherein i=1, 2, 3, ..., or 12; and performing ultraviolet accelerated aging in an ultraviolet aging box, querying an ultraviolet irradiation power P of the ultraviolet aging box, and calculating an equivalent ultraviolet accelerated aging time tuv; of each month according to Formula (1), to obtain the ultraviolet irradiation equivalent (P, tuv;) of each month, wherein i=1, 2, 3, ..., or 12; uvi tuvi = P (1).
- 3. The evaluation method according to claim 1, wherein calculation of the temperature-humidity aging equivalent of the coating in hygrothermal accelerated aging comprises the following steps: calculating an aging effect time of hygrothermal accelerated aging according to Formula (2): t2 e Q -C/(T11)K --t, e-cAT2(p2) wherein in the formula, K is a time acceleration coefficient, ti and t2 are respectively a laboratory hygrothermal aging time and a natural aging time, Ti and T2 are a hygrothermal aging temperature and a natural aging temperature, pi and p2 are respectively hygrothermal aging humidity and natural aging humidity, and C is an (2) equivalent accelerated aging coefficient; querying an average temperature Ti and average humidity plof a target region for each of January to December in a specific year, wherein i=1, 2, 3, ..., or 12; and calculating, according to Formula (2), a time ti required for accelerated aging after equivalent at a target temperature and target relative humidity that correspond to each month, to obtain the temperature-humidity aging equivalent it setting+(psetting, t) of each month, wherein i=1, 2, 3, ..., or 12, and tsetting and 9setting are respectively an environmental temperature and relative humidity that are set based on a service temperature of the coating.
- 4. The evaluation method according to claim 3, wherein a highest service temperature designed for the coating is 60°C, and an environment selected for accelerated hygrothermal aging is a constant temperature and humidity environment with a temperature of 55°C and relative humidity 9 of 95%.
- 5. The evaluation method according to claim 1, wherein determining of an equivalent accelerated aging coefficient C comprises the following steps: preliminarily determining Ci; determining a time when a hygrothermal aging test needs to be performed, and querying an average temperature Tt and average humidity cpt of test periods in the past three years in a target region; calculating a hygrothermal aging equivalent time tt according to Formula (2), and obtaining a hygrothermal accelerated aging program based on highest service temperature and humidity designed for the coating and the hygrothermal aging equivalent time tt; performing the hygrothermal aging test according to the hygrothermal aging program, and simultaneously performing an indoor natural aging test; and performing an adhesion test on the outdoor coating after the tests are completed, synchronously correcting the equivalent accelerated aging coefficient Ci according to a test result, and performing an accelerated aging test again; wherein when an actual accelerated aging test result is equivalent to a natural aging result, obtained Ci is an optimal equivalent accelerated aging coefficient C of the outdoor coating.
- 6. The evaluation method according to claim 5, wherein the equivalent means that the actual accelerated aging test result differs from the natural aging result by less than 5%.
- 7. The evaluation method according to claim 5, wherein the past three years are January to December of each of the past three years.
- 8. The evaluation method according to claim 5, wherein Ci is preliminarily determined based on experience, a manual, or literature data.
- 9. The evaluation method according to claim 1, wherein a temporal variation rule of the adhesion is shown in Formula (3): S = So -60111(1 + et) (3) wherein in the formula, S is adhesion after aging is performed for a time t, So is initial adhesion, w represents an aging resistance parameter of the coating, and 9 is an environmental aging erosion coefficient.
- 10. The evaluation method according to claim 9, wherein data fitting is performed on the test result of the adhesion of the coating obtained after aging of each cycle period, and the aging resistance parameter w and the environmental aging erosion coefficient 6 of the coating are obtained according to Formula (3).
- 11. The evaluation method according to claim 10, wherein the service life of the outdoor coating is a service life Tr of the outdoor coating that is calculated according to a fitting equation obtained by fitting the adhesion of the coating and according to a value Ff of lowest adhesion specified in a coating failure technical requirement.
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