The gasoline resistance of the coating film can be determined according to the method in the national standard GB/T1734-93 "Determination of gasoline resistance of paint film". This standard specifies the method for the determination of the gasoline resistance of the paint film, including two methods: gasoline immersion method and gasoline pouring method. After reaching the specified time, the change of the surface of the paint film is used to express its gasoline resistance performance.
(1) Materials and equipment
① Bottom plate: The bottom plate should be flat and free of group paintings, and the surface of the board should be free of any visible grains and wrinkles. Unless otherwise specified, the bottom plate shall be 120mmx50mmx(0.2~0.3)mm tinplate.
②120 solvent oil (according to the regulations of GB1922): such as redistilled motor gasoline, whose distillation range meets the requirements of 120 solvent oil in GB1922, and can also be used.
③RH-75 aviation gasoline (according to the regulations of CB1787)
④ Iron block: Cylindrical, weighing about 500g, flat bottom, diameter 45mm ± 1mm.
⑤ Glass waste
(2) Treatment and coating of the bottom plate
Unless otherwise specified, prepare the paint film on three tinplate plates according to the provisions of (GB 1727.
(3) Test procedure
① Method A: Immersion gasoline method
a. Immersion of the test plate: Add No. 120 solvent oil or RH-75 aviation gasoline specified in the product standard to the glass tracing. Unless otherwise specified, adjust the temperature to 23 °C ± 2 °C and maintain this temperature throughout the test.
Put three test panels into it: 2/3 of the length of each test panel is immersed in the liquid.
b. Inspection of the test plate: After the immersion time specified in the product standard is over, take the test plate out of the tank, blot it dry with paper, and inspect the test plate visually immediately or after the time specified in the product standard. Record whether there are wrinkles, blisters, peeling, softening, discoloration, loss of light, etc. on the surface of the paint film.
At least two of the three test panels shall be considered qualified if they meet the requirements of the product standard. The 5mm wide part above and below the soaking line is not used as the result evaluation.
② Method B: Pour gasoline method
a. Test conditions: Unless otherwise specified, the field test should be carried out under the constant temperature and heavy humidity conditions stipulated in GB1727.
b. Operation steps: pour 5mL of 120 solvent oil or RH-75 aviation gasoline on each test plate according to the product standard, and immediately make it cover the surface of the test plate paint film. Place it at an angle of 45° for 30 minutes. Then lay it flat, put a piece of gauze with two layers and one thickness on the surface of the paint film, put an iron block on it, keep it for 1min, and then take it off. Turn over the test panel and the gauze should not stick to the paint film, or tap a few times on the back of the sample with your fingers, and the gauze can fall freely.
At least two of the three test panels shall be considered qualified if they meet the above requirements.
