When the ink is applied on the surface of the object to be coated, the ability of the paint film to be firmly connected with the bottom layer is called adhesion. Adhesion is one of the important performances to assess the paint film. If the adhesion of a kind of paint is not good, it is impossible to talk about the problem of good performance such as mechanical strength.
Adhesion determination, generally use two types of test methods. One is a comprehensive measurement method, such as the cross-hatch method, cross-cut method and circle method; the other is a peel test method, such as the twisting method and the pulling method. Examples are as follows:
(1) cross-cut method
Apply the sample on the sample board (usually a zinc-coated iron sheet model), and once it dries, use a safety knife to cut six parallel incisions on the paint film (about 10-20 mm , and the distance between the incisions is 1 mm), should cut through the entire paint film; then use the same method to cut six, perpendicular to the former, forming many small squares, and then touch it lightly with your fingers. The paint film should not fall off from the grid, but is still firmly combined with the bottom plate, which is qualified, and it is calculated as 100%.
(2) circle method
my country's national standard adopts the circle method. This method uses an adhesion Tester , uses a phonograph needle as a needle, and fixes on a movable test bench. When the crank handle is turned, the needle point makes a uniform circular motion on the paint film , and depicts the pattern of overlapping circular rolling lines. The adhesion of the paint film can be determined by observing the peeling position of the paint film from the texture of the circular rolling line. There are seven levels of adhesion in the circle drawing method, the first level is better, the second level is slightly worse, and the rest are analogous, and the seventh level is the worst.
