GB/T 1720 Determination of paint film adhesion: Circle method

In the field of painting, the adhesion of coatings is a crucial performance indicator, which is directly related to the durability and service life of coatings. The GB/T 1720 standard specifies an effective method for the determination of paint film adhesion. This article will introduce the test principle of the method, required materials and equipment, operation points and precautions.

1. Test principle

GB/T 1720 Paint film adhesion measurement method evaluates the adhesion of coatings by marking the lines of overlapping circular rolls on the paint film. During the test, the sample is fixed on a front and rear movable platform, while the stylus cuts the paint film during the circular movement. This test method takes into account the destructive effect of vertical pressure and swirl/spin motion of the steel needle on the paint film, which enables a more accurate assessment of the adhesion performance of the paint film.

2. Materials and equipment

• Adhesion tester: using QFZ type paint film adhesion tester, the instrument is equipped with three or five brand stylus, no-load pressure is 200g, load weight is 100g, 200g, 500g, 1000g, the rotation radius of the rotary needle is adjustable, and the standard rotation radius is 5.25mm.

• Horse iron plate: as a test sample, the size is 120mm x 50mm, and the thickness is between (0.2~ 0.3) mm.

3. Operation points

• Preparation of the test plate: Use the Film Applicator to place the Paints Spreader on the horse iron plate, and after the paint film is dried, ensure that the paint film is flat.

• Adhesion measurement: Fix the test plate on the test bench, make the tip of the stylus contact the paint film, shake the handle evenly, and control the Rotation speed at (80~ 100) rpm. The standard scratch drawing length is (7.5 + 0.5) cm. After scratching, take out the test plate and remove the paint on the scratch.

• The results show that the 7 parts on the upper side of the scratch are observed by magnifying glass or visually, and the grades 1, 2, 3, 4, 5, 6, and 7 are marked respectively. Check the integrity of the paint film at each part in sequence, and indicate the adhesion of the paint film with the lowest level of intact paint film. Test at least two templates to determine the conformity of the results.

4. Precautions

• Stylus needles must be kept sharp to ensure effective scratching of the paint film.

• The standard radius of rotation should meet the requirements to ensure the accuracy and conformity of the test.

5. Significance and application

Film adhesion is an important parameter for evaluating coating mass, which directly affects the performance and service life of coatings. The film adhesion measurement method specified in GB/T 1720 standard can accurately evaluate the adhesion performance of coatings by simulating the scratching and torsion under actual use conditions. This test method is widely used in the painting industry for quality control, process improvement and painting formulation optimization.

6. Conclusion

GB/T 1720 film adhesion measurement method is one of the important methods to evaluate the adhesion performance of coatings. By simulating the scratching and torsion under actual use conditions, this method can accurately evaluate the adhesion performance of coatings, thus providing a scientific and reliable quality control method for the painting industry. This test method is of great significance in the guarantee of mass painting and the optimization of coating process.