ASTM F22-21 Standard Test Method for Hydrophobic Surface Films by Water Breaking Test specifies a method for determining hydrophobic surface films by water breaking test. This test is used to evaluate the hydrophobic performance of a coating or film on a material's surface, particularly with regard to surface moisture diffusion characteristics. The water breaking test detects whether the coating is effective in preventing the infiltration and diffusion of water by observing the behavior of water droplets on the surface. The fact that the water droplets do not break and remain in their original state indicates that the surface has strong hydrophobicity, while the diffusion or rupture of water droplets indicates poor surface hydrophobicity. This method is widely used in industries such as Coatings, Nano coatings, Plastics and Glass to help evaluate the effect of coatings or surface materials in waterproof, anti-corrosion and other applications, and provide a scientific basis for the quality control and technology development of related products.