Coating Conditioning performance inspection

The aging performance of the coating refers to the performance of the coating being damaged due to aging in various climates (such as sunlight, wind, rain, snow, base, dew, atmosphere and industrial gases, etc.). Therefore, the aging performance of the coating is also It is called weather resistance. It reflects the use value of the product to a large extent. The aging performance of the inspection layer is one of the important contents of the original quality inspection.

The test methods for the aging performance of coatings mainly include atmospheric aging and artificial accelerated aging test. The former test results are more accurate, but the test cycle is longer, and the latter test period is shorter, but there is a certain gap between the test results and the atmospheric aging test. .

1. Atmospheric aging test

The atmospheric aging test of the coating is carried out in an atmospheric exposure field that meets certain conditions. After the atmospheric exposure test, the aging performance of the coating is evaluated by the appearance inspection of the sample.

(1) Test conditions

a. The type of atmosphere. The atmosphere is divided into four types: industrial atmosphere, marine atmosphere, rural atmosphere and suburban atmosphere, which are the same as the coating atmospheric exposure test.

b. Climate type. According to the geographical division of our country, the climate is divided into temperate tropical climate, subtropical climate, temperate climate and cold temperate climate.

c. Season. The season has a great influence on the opponent's self-made coating, generally:

When spring hands are exposed to the sun, the method layer is not yet fully firm, and the method layer is easily deformed due to the sharp change of temperature difference;

When exposed to the sun in summer, strong external light and a large amount of commercial water will further damage the dharma layer;                                                         

When exposed to the sun in autumn, due to the stable temperature, the intensity of outside light decreases day by day, and there is a period of hardening process in the law layer;

When exposed to the sun in winter, the temperature is low, but the coating will be damaged to a certain extent when it is wet by normal, snow and rain. From strong to weak.

D. Exposure angle (azimuth). The angle of long-term sun exposure is generally preferable; the latitude.

For short-term snail drying, in order to quickly obtain the results of the atmospheric base dew test, the drying angle should be adjusted as follows: from January to June, use the local latitude minus 25° exposure; from July to December, use 0.893 times the local latitude plus 24° ° Exposure. e. Sample frame tilt. In order to improve the yield of the sample, the sample frame tilt angle of the heavy-duty sample is generally 45° from the horizontal direction.                                    

f. Atmospheric-based open field environment. The site selection for the atmospheric aging test of the coating is the same as the requirements for the 9 field of the atmospheric storm of the coating.                                                     

(2) Sample preparation

 According to the requirements of the standard, the sample preparation for the atmospheric aging test should meet the following conditions:

①Material and inch. Ordinary low-breaking steel plate, the specification is 70mmx150:mm x0.8-1.5mm; LY12 aluminum plate, the specification is 70mmx150mmx1-2mm

②Surface treatment. The steel plate is degreased with solvent, and after manual derusting with sandpaper, it is wiped with solvent and dried, and it can be painted. Aluminum plate can be surface treated by normal temperature positive plate gasification method.

③Requirements for the sample. The prepared sample should have a flat, smooth surface, no porosity, and the coarse particles should be minimized.

(3) Test method  

The method of the atmospheric aging test of the coating is basically the same as that of the atmospheric base dew test of the coating.

(4) Result evaluation  

After the atmospheric aging test of the coating, the content of the evaluation of the results of the sample includes the loss of gloss, discoloration, powdering, graining, blistering, rust, etc. of the coating. Unless otherwise specified, the evaluation and grading standards can generally be Follow the criteria below for evaluation.

a. Gloss loss of the coating. After the aging test of the coating, use the visual method to check the degree of gloss loss and the percentage of gloss loss on the surface of the coating.

b. Coating discoloration. After the coating aging test, check the degree of discoloration , and compare with standard color plates if necessary.

c. Coating pulverization. After the coating aging test, use pulverization test equipment or methods such as quality method, gloss method, finger method, etc. to check the degree of pulverization of the coating.

d. Number of cracks. After the aging test of the coating, check the texture depth, density and percentage of the coating by visual inspection .

e. Blistering. After the coating aging test, check the size, density and distribution area of ​​the blisters .

f. Rust candle. After the coating aging test, use the visual method to check the number and size of rust spots on the coating surface , take the area of ​​the sample as 10 grids, and count the number of grids of rust candles as a percentage.             

2. Artificial accelerated aging test               

The artificial accelerated aging test is an accelerated test method that uses an artificial accelerated weather resistance Test Chamber to simulate the atmospheric aging test conditions and conduct an aging test on the coating. It has the characteristics of quickly measuring the aging of the coating. There are still some deviations in the test results. Another atmospheric accelerated aging test method, through the reflection of sunlight, increasing sunlight and other means, makes it more consistent with the atmospheric aging conditions, thereby accelerating the determination of delamination aging performance.

(1) Artificial weathering accelerated aging test  

This method is used for accelerated aging test of paint film.

a. Test equipment. The artificial accelerated aging test is carried out by the artificial accelerated weather resistance test. The main test conditions are: the light source is a 6 kw water-cooled tube xenon lamp; the distance between the sample and the light source is 35-40cm; the stabilizing device adopts a magnetic saturation stabilizer or other Voltage stabilizing device; the test water is the valence water circulation for xenon lamp cooling, and the high ion exchange resin is used to purify the water for rainfall.

b. Test conditions. The air temperature in the working room is 45°C ± 2°C; the relative humidity is 70%, 5%; the two periods of fall are 12 minutes of rainfall per hour; the test conditions for special-purpose paint films can be selected according to different use environments and product standards .                        

c. Sample preparation. It is the same as the sample preparation for atmospheric aging test.

e. Test procedure. Place the sample prepared according to the regulations on the sample fixture rack, insert it into the climate Test Chamber and turn it on. Then start the instrument according to the instrument manual, and control the test temperature, humidity, and rainfall cycle test under the same conditions.

f. At the beginning of the inspection, stop for inspection every h, 192 h (8 days)

After that, stop the machine for inspection every 96 hours. After each stop for inspection, the upper and lower positions of the sample are exchanged. The stop index should be determined according to the degree of aging and damage of various paint films and specific requirements. Any one of the "poor grades" in the product standard evaluation.      

h. Result evaluation. After the artificial accelerated aging test, take the sample out of the weather resistance Test Chamber , dry the water traces on the back with a towel, and place it on the test bench facing upwards to dry, then conduct inspection and rating .It can also be graded according to the provisions of the atmospheric aging test results.

(2) Atmospheric accelerated aging test

a. Test preparation. The atmospheric accelerated aging test is used to test the aging performance of the coating, which is carried out by an atmospheric accelerated aging machine.

The atmospheric accelerated aging machine uses a frame that can rotate with the sun, and there are 10 pieces of 150mmx1500mm aluminum plates on the frame as reflectors. Each reflector will reflect sunlight and concentrate it on a 15ommx1 5oo front sample holder. The aluminum plate is a specular reflector that has been electro-approved, and it can reflect 85% of visible light and 70%-81% of ultraviolet light.

A blower is installed above the test frame to make the surface temperature of the sample close to the drying temperature at an angle of 45° facing south. A water spray pipe is installed under the sample frame to spray distilled water on the sample regularly to further accelerate the aging of the legal layer. speed.

Since the test is directly irradiated by natural light, the difference of artificial light source is eliminated, and with the increase of reflection intensity and sunshine time, it can accelerate the aging of the coating and shorten the test period. It has been proved by the test that the atmospheric accelerated aging test As a result, its aging speed is equivalent to 6-12 times of the result of exposure to the sun at a 45' angle facing south in the atmospheric aging test, so a more satisfactory effect can be obtained.   

b. Sample preparation. The sample standard is the same as that of the atmospheric aging test.

c Test method. After the sample (usually two sets of samples for each variety) is carefully checked before the test and its original state is recorded, it is then required to be placed on the sample surface of the atmospheric accelerated aging machine. Then the use of the equipment is followed. According to the requirements specified in the manual, start the equipment, turn on the spray system, and carry out the aging test on the sample under the specified temperature, humidity and other conditions. The termination index of the test should be determined according to the degree of aging damage of the paint film and the specific conditions. (Related instruments: aging Test Chamber)

d. Result evaluation. Refer to the evaluation method of atmospheric aging test results.