The reverse impact test of printed color steel plate is used to evaluate the anti cracking or peeling ability of the coating when the sample is subjected to rapid deformation. The impact resistance is also called impact strength. It refers to that the coating on the sample will deform rapidly and form a convex area under the impact of the free falling weight. Check whether the coating on the convex area has cracking or falling off, so as to evaluate the coating anti cracking The ability to crack or fall off. It shows the flexibility of the tested coating and the adhesion to the substrate.The instrument used in reverse impact test is impact tester. Printing color steel plate is tested by common special instruments. According to the national standard GB / t13448-2006, the punch diameter is 15.87mm (5 / 8in), and the test results are expressed in two ways of "qualified / unqualified" and "large impact energy". In the former, the adhesive tape method is used to check whether the coating impacted by the weight and falling height of the hammer is peeled, and whether the coating is cracked is observed with a magnifying glass; the latter is to find out the large mass and height of the coating without cracking or peeling by changing the impact of the weight and falling height of the hammer, and the product of the two is the large impact energy. The principle of the test is to let the heavy hammer fall freely to impact the sample, denaturate the sample, and gradually increase the falling height or mass of the heavy hammer. The rapid deformation resistance of the color steel plate coating is the product of this height and the weight of the hammer, expressed in Joule (J). The impact resistance index of printing color steel plate is generally controlled at the impact energy of no less than 9j.