Stone chip resistance
Stone chip resistance refers to the ability of automotive coatings to resist the impact of sand and stones. It is a very important indicator of automotive composite coatings (primers, primers, topcoats), and cannot be used as a technical indicator of a single topcoat. . Because of the level of stone chip resistance, in addition to the performance of the topcoat, the performance of the middle coating also plays a decisive role. The middle coating has good elasticity and is well combined with the top coat, which can act as a buffer, thereby greatly improving the stone chip resistance of the coating. The method of anti-stone impact test is as follows: under the pressure of 0.1 MPa, use irregular multi-angular Υ≈4 ~ 5 mm iron sand to impact the coating, stick it with adhesive tape, and check the number or number of coating peeling points after tearing off. The weight loss of the coating is used to determine the level of stone chip resistance.
Scratch resistance
Scratch resistance is the ability of automotive coatings to resist scratching by hard tools, and it is one of the technical indicators with great practical application value. It is measured by a special scratch resistance Tester. Under a certain gravity, use a specified steel needle to scratch the surface of the coating to see if the coating is damaged. Its measurement method is similar to that of the pencil hardness of the coating, but the hardness index refers to the index of a single coating at a certain thickness, which is the characteristic index of the coating itself, and the scratch resistance is the index of the composite coating. They cannot be substituted for each other. The factors affecting the scratch resistance of the coating are not only related to the hardness of the top coat, but also the elasticity of the middle coating. The use of additives that improve slip in the topcoat, such as BYK 310 and 320, can also improve the scratch resistance of the coating.
The performance indicators of the above three kinds of coatings are important indicators for comprehensive evaluation of automotive coatings. Most domestic and foreign automobile manufacturers have their own standards, and they are not suitable as indicators for coating factory products. For this reason, many foreign automotive coating manufacturers mostly simulate the actual situation of automotive coating, and conduct coating tests of primers, intermediate coatings, and topcoats to provide reliable reference data for automobile factories and meet the needs of automobile factories.
For more details, please refer to the full text of "A Brief Discussion on the Current Situation and Development of Automotive Coating Performance in my country" (Zhou Guangya)
