Reverse impact test of color coated sheet is used to evaluate the anti-cracking or peeling ability of coatings under rapid deformation. Impact strength is also called impact strength. It refers to the rapid deformation of coatings on specimens and the formation of convex areas under the impact of free-falling weight, so as to check whether the coatings in convex areas are coated or not. Cracking or shedding occurs to evaluate the anti-cracking or shedding ability of the coating. Without cracking or falling off from the metal substrate, it shows the flexibility and adhesion of the tested coating to the substrate.
The instrument used in reverse impact test is impact tester, which usually uses special instrument. According to the national standard GB/T 1348-2006, the diameter of punch is 15.87 mm (5/8in). The test results are expressed by "qualified/unqualified" and "maximum impact work". The former uses tearing tape method to check whether the coating is peeled off after the impact of weight and falling height, and observes whether the coating is cracked by magnifying glass; the latter finds out the maximum mass and height of the coating without cracking or peeling by changing the impact of weight and falling height, and takes the product of the two as the maximum impact. Hit Gong. The principle of the test is to let the hammer drop freely and impact the sample to deform, and gradually increase the height or mass of the hammer drop. The anti-rapid deformation ability of the coating is the product of the height and the weight of the hammer, expressed as Joule (J). The impact resistance index of coil coatings is generally controlled at impact energy not less than 9J.
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