Paint film adhesion and test method thereof

Paint film adhesion and its testing

The adhesion of the paint film is an important indicator for evaluating the quality of the bond between the paint film and the substrate. It covers the physical and chemical binding force between the coating film and the surface of the substrate, which is directly related to the stability and performance of the coating film. In coating engineering, adhesion is a key factor to ensure that the coating film adheres stably to the surface of the substrate without falling off or cracking. This article will introduce the concept of paint film adhesion, test methods and the importance of these test methods in the evaluation of paint films.

The concept of paint film adhesion

Paint film adhesion refers to the strength of the physical and chemical bond between the paint film and the substrate. It comprehensively considers factors such as the affinity and wettability of the coating film and the surface of the substrate, as well as the surface roughness of the substrate. Excellent adhesion means that the coating film can adhere tightly to the surface of the substrate and will not fall off or crack due to external impact or stress.

Test method for paint film adhesion

Adhesion testing methods can be divided into two categories according to their directness and indirectness: direct methods and indirect methods .

• Direct method - pull-away method (GB 5210-85) : This method mainly measures the force required to peel the coating film from the surface of the substrate by applying pulling force. Measuring the force required during the process of pulling the coating film apart can reflect the adhesion of the coating film. However, this method may suffer from instability during operation.

• Indirect methods - circle method and cross-hatch method : circle method and cross-hatch method are a type of commonly used indirect methods. The circle drawing method (GB/T 1720-89) uses a circle drawing adhesion tester to draw the coating film into a circular line with a scoring needle, and evaluate the adhesion based on the completeness of the drawing line. The cross-hatch method (GB/T 9286) uses a high-alloy steel cross-hatch tool to cut a grid on the coating film, and the adhesion is evaluated by the integrity of the cuts.

  
  

  
  

  
  

  
  

The significance of paint film adhesion test

Paint film adhesion testing is of great significance in coating film evaluation. Good adhesion ensures that the coating film can adhere firmly to the surface of the substrate and is not affected by external stress. The adhesion test results can guide the selection, application and quality control of coatings to ensure that the coating film has stable performance in actual use.

Summarize

Paint film adhesion is one of the key factors in evaluating the quality and performance of a paint film. Adhesion testing methods can be carried out through direct methods and indirect methods, among which the circle method and the cross-hatch method are commonly used indirect methods. Through paint film adhesion testing, we can understand the bonding between the paint film and the substrate, thereby providing strong support for the selection, application and quality control of paint. Excellent adhesion can ensure that the coating film remains intact under various environmental conditions, extend the service life of the coating film and improve the appearance quality.