The scratch test of color coated steel plate is mainly used to evaluate the adhesion between the initial coating of the sample and the substrate or the anti-separation ability of the coatings in the multi-layer coating system.
Adhesion is the basic index for evaluating coating quality. At present, the gridding method is widely used in the domestic color coating industry. The gridding test is usually carried out by the gridding tester (Figure 4-16) according to the national standard. When the cross-cutting coating is adopted, the following test technical requirements are required: the blade spacing is 0-50um for the sample with coating thickness, 11 edge grinding instruments are selected, and the blade spacing is 1mm, which is a smooth method. Eleven parallel cutting lines are drawn, and for the samples with coating thickness of 50-125 um, six edge grinding instruments are selected, with tool spacing of 2 mm, and six parallel cutting lines are drawn by a smooth method. Then, 11 or 6 parallel cutting lines are drawn vertically intersecting with the original cutting line at 90 angle to form a lattice pattern. Finally, 600 adhesive tape is used to adhere to the coating. Then, the tape is pulled down rapidly with the force at 60 angle to test whether the coating peels off the substrate.
The adhesion of coatings is mainly determined by the formulation properties of coatings, but the cleanliness of the substrate surface can also seriously affect the adhesion of coatings, especially when there are oil stains, paraffin, silicone oil and other release agents, organosilicon additives on the substrate surface, the surface polarity is very weak, and the direct contact between coatings and the substrate surface is hindered, and the adhesion will be seriously reduced. Drop. Therefore, strict control of degreasing and cleaning of the substrate surface treatment can greatly improve the adhesion. Strengthen the surface polarity to ensure the adhesion of the paint.
The results of the grading test in China's color coatings industry are mostly evaluated by comparing the surface damage state of the coatings after being cut and torn off by adhesive tape with the "grading of test results" in the national standard CB/T13448-2006. The grading of test surfaces is expressed by six grades: 01, 2, 3, 4 and 5.
There are many kinds of specifications (6-edge and 11-edge) in China. Users can choose and use them reasonably according to their test needs and technical standards.