For the salt spray test of the paint film, the nozzle type YQ-26 and YQ-30 salt spray box tests are mostly used at present. The measurement process mainly includes:
(1) The preparation of the sample is the same as that of the damp heat test.
(2) Prepare salt water or artificial sea water. One is pure salt water solution with a concentration of 3%, 5% and 20%; the other is artificial sea water. The artificial seawater formula is:
| NaC1 | 27 g/l |
| CaCl2 | 1 g/l |
| MgCl2 | 6 g/L |
| KCI | 1 g/l |
Control the pH value of the brine between 6.5 and 7.2. If it is not within this range, it can be adjusted with dilute hydrochloric acid or sodium hydroxide.
(3) Test temperature. 47 ± 2°C
(4) Spray cycle. Spray continuously for 15 minutes every hour, stop spraying for 45 minutes. During the time of stopping spraying, the humidity in the box should be kept above 90%.
(5) Test period. Check every 24 hours. Test until the destruction of the paint film reaches failure.
(6) Sample placement. The painted surface of the model is placed at an angle of 3 mines to the direction of salt spray settlement. After each inspection, the position of the sample should be exchanged to eliminate the error caused by the uneven spray volume and temperature in the equipment .
(7) Xiang board inspection. When inspecting the sample plate, take out the sample plate carefully, rinse the salt deposited on the surface of the test sample plate with running cold water, and perform visual inspection and rating after it is dry.
Pay attention to the following when testing:
(1) During the continuous test, it is necessary to check the nozzle frequently to ensure the normal spraying.
(2) The compressed air used needs to be degreased.
(3) During the spraying process, agents such as salt water cannot be recycled.
(4) The spray pressure needs to be constant so as not to affect the reproducibility of the test.