The adhesion of the paint coating includes two aspects: the adhesion between the organic coating and the metal surface of the substrate; the cohesion of the organic coating itself, the greater the adhesion strength between the organic coating and the metal surface, the better; The combination of the two films can better block the corrosion of the metal by external corrosion factors, so as to achieve good protection for the metal.
The paint coating cannot be firmly attached to the metal surface, and no matter how good the coating is, it will not work; the coating itself has poor cohesion, and the paint film is easy to crack and lose its effect. The above two jointly determine the adhesion of the coating and constitute the key factor determining the protective effect of the coating.
Cross-cut method
The standards for the cross-hatch method are: ASTM D 3359 Method B and ISO 2409, and the national standard GB/T 9286-98 is equivalent to ISO 2409. The test methods and descriptions of the two are basically the same, but the order of the adhesion level is just the opposite: ASTM D 3359 is 5B~0B (from good to bad), ISO12944 is 0~5 (from good to bad).
Use a single-sided safety blade to draw eleven parallel cuts on the paint film of the sample or workpiece to be tested; then draw eleven perpendicular cuts in the same way, thus forming 100 small squares . Then touch lightly with your fingers, the paint film does not fall off from the grid, it is qualified, and then rub it again with your hands, if it is still firmly combined with the bottom plate, it is good; if it falls off, it is expressed as a percentage that cannot be retained. This method is relatively simple and intuitive, and does not require special instruments and equipment. It is especially suitable for use on the construction site, but the result is relatively rough.
circle method
This is the adhesion determination method stipulated in the national standard. my country's national standard GB/T1720-1998 and Japanese industrial standard JISK6894 respectively make clear technical regulations on the evaluation of coating film adhesion performance by overlapping circular rolling line scratch method, which has become a long-term traditional test method used in CHINA, Japan and other Asian countries . This method uses a paint film adhesion Tester, uses a phonograph needle as a needle, and fixes the model on a movable test bench. During the test, while the test bench moves forward at a constant speed, the steel needle pierces the paint film and makes a circular motion with a radius of 5.25 mm, so that overlapping curved circular rolling lines appear on the surface, and the paint is observed from the lines of the circular rolling lines. The damaged position of the paint film, and evaluate the adhesion of the paint film according to the requirements.
