Paint and Varnish - Determination of resistance to liquid media
Determination of the resistance of paints and varnishes to liquid media (GB/T9274-88) This standard is equivalent to the international standard 1S0 2812-1974 «Paints and varnishes - Determination of resistance to liquid media».
(1) Main content and scope of application
This standard specifies the test methods for the resistance of paint films (single coat or composite coat) or painted specimens to liquid action of paints and varnishes. There are three test methods: immersion method, absorbent medium method and spot method. The use is determined by the requirements of the test material and the resistance of the paint.
(2) Test piece
① Unless otherwise specified or agreed. The test plate is specified as tinplate quilt (GB2520) 50mmx120mmx (0.2~0.3)mm, steel plate (GB912) ordinary carbon cold-rolled steel plate: 50mmx120mmx (0.45~0.55)mm, aluminum plate (GB3880LYl2) 50mmx120mmx ( 1~2) mm.
②Test rod: only applicable to soaking method. One end of the test bar shall be ground back with a radius close to the radius of the bar itself, and the other end shall have a hole or ring. Unless otherwise specified, the bar shall be steel or aluminum and measure φ15m x 150mm.
③ Treatment and painting: For the test panel, unless otherwise specified or agreed, it shall be carried out in accordance with the provisions of GB/T9271. It is usually better to apply a suitable protective paint or test paint on the backside of the test panel, and the edges of the test panel should be sealed in this way. For the test rod, unless otherwise specified or agreed, it shall be carried out in accordance with the provisions of GB/T 1727.
(3) Test procedure of method A (soaking method)
① Liquid material for testing: the testing liquid specified in the product standard.
②Test temperature: Unless otherwise specified, the test should be carried out at 23°C±2°C
③Test Precautions
a. It is better to use the method of separate test piece liquid tank, because when using high conductivity test liquid, there may be electrolysis effect, so it is more necessary to do so.
b. It may be more convenient to immerse the entire test piece in the test solution tank, but the test pieces should be of the same nature, so as to ensure that the test solution is not affected by the test piece.
c. The immersed test piece is at least 30mm away from the inner wall of the test piece. If several test pieces are immersed in the same test piece, the distance between them should be at least 30mm. The test piece should be insulated from its support.
④ Use a single-phase liquid
a. Pour a sufficient amount of test solution into an appropriate container to fully or partially (2/3) immerse the specified test piece (test bar or test plate), and use a suitable support to immerse the test piece in an almost vertical position .
b. In order to reduce the loss of test solution due to evaporation or splashing, the container should be increased.
c. If air blowing is specified to agitate or circulate the liquid, the blowing shall use a degreasing slow air flow. If there is such a requirement, the test solution or distilled water should be added at an appropriate time to compensate for the loss of the liquid, with the purpose of maintaining the original volume or concentration.
d. When the specified immersion period set point is reached, if an aqueous solution is used, rinse the test piece with a water substrate. If it is a non-aqueous test solution, rinse with a solvent known to be harmful to the coating, wipe the surface with a suitable moisture-absorbing paper or cloth to remove residual liquid, and immediately inspect the test piece for coating changes. Can be compared with unsoaked test pieces For comparison, if a recovery period is specified, the inspection and comparison shall be repeated after the specified recovery period.
e. If it is necessary to check the erosion of the substrate, remove the coating with the specified method.
⑤ Using two-phase liquid
a. Put the paint removal test piece into a suitable container with a suitable support so that it is in a nearly vertical position. For the test panel, its broad side is horizontal.
b. Prepare each test solution immediately before use.
c. Unless otherwise specified, pour the dense liquid from the side of the container until the test piece (structure or root) is covered to a depth of 6lhn. Be careful when operating, and be sure not to contaminate the test piece above this level.
d. Unless otherwise specified, add the second liquid in the same way until the test piece is completely submerged, cover the container, do not stir, and let it discharge.
e. After reaching the specified immersion period, take out the test piece from the test solution, gently wipe off the test solution on the surface with a suitable moisture-absorbing paper or cloth, and immediately check the change of the contact part between the test piece and each liquid phase Phenomenon. If necessary, compare with a similarly prepared unsoaked test piece. If a recovery period is specified, repeat the inspection and comparison after the specified recovery period.
f. During the midway inspection of the test piece, the sample does not need to be taken out, otherwise it should be cleaned immediately and the soaking operation should be repeated.
g. If it is necessary to check the leaching of the substrate, remove the coating by the specified method.
