Coating is traditionally called paint in China. Coating is coated on the surface of the object to be protected or decorated, and can form a continuous film that is firmly attached to the object. The authoritative book "Coating Technology" in Chinese coating industry defines it as follows: coating is a material that can be coated on the surface of objects by different construction techniques to form a solid, continuous firm with certain strength. This kind of film is generally called a coating film, also known as a paint film or a coating. Coatings generally consist of four basic components: film-forming substances (resins), pigments (including extenders), solvents and additives. The main functions of coatings are: protection, decoration, concealing product defects and other special functions.