Determination of the stability of the coating film to the detoxification agent
The disinfectants used for railway vehicles and wooden gondolas transporting perishable goods can use dilute solutions such as soda ash (carbonic acid blunt), alkali or milk of lime.
The paint films used to finish the interior of these compartments shall be tested in a 2 % hydroxide inert solution. For this purpose, a pine board with a size of 200x125 mm and a thickness of 10 mm must be coated with the tested color paint twice, and the drying time shall be specified in the technical conditions. After the second layer dries for 1 day and night, put a cotton ball soaked (fumigated) in 2% hydroxide blunt solution on the coating film. After 2 hours, remove the cotton ball and rinse the film effectively with water. After drying, there should be no cracks, blisters or other damage on the coating film. (Related instrument: drying time Tester)
Determination of the stability of coating films to detergents
To test films which should be stable to periodic washing with dilute soda ash solution or soap, the following methods may be used:
1. Coat the iron or wood board with two layers of paint samples, and the drying time between the two layers must meet the technical conditions.
After the second coat has dried for 5 days and nights (when using an air-drying paint material), immerse half of the test panel in a 5% sodium-alkali solution for 1 hour. Then take out the test panel, and after drying in the air for half an hour, measure the hardness of the coating film. At the same time, the hardness of the upper half of the coating film was measured in parallel. (Related instrument: Hardness Tester)
The hardness of the stabilized coating film after the test shall not be lower than the hardness of the coating film before the test. Exactly the same as in this case the appearance of the coating film should not change after the test.
2. Place a cotton ball moistened with a 3.% soda ash solution on the film to be tested. After a while, remove the cotton ball and wash the place where the cotton ball was placed with water. The stable coating film should not show any changes.
