What other theoretical explanations are there for the adhesion of paint coatings?

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The available public information already covers the mainstream theories for explaining paint adhesion. As for the supplementary theories you mentioned, apart from the mechanical adhesion theory and the aforementioned theories such as van der Waals forces, chemical bonds, hydrogen bonds, diffusion, and electrostatic forces, there are no other widely recognized theories that form an independent system. However, the details of the mechanical adhesion theory within the existing theories can be further elaborated upon: Full details of the mechanical adhesion theory (mechanical interlocking theory). This is the earliest observed and confirmed mechanism of adhesion, and it applies to all situations where painting is done on surfaces with irregularities. When there are pores, cracks, pits, or rough textures resulting from grinding on the surface of the substrate, the liquid paint can flow into these spaces. Once the paint dries and solidifies, the parts that have penetrated these spaces form a mechanical interlocking structure similar to “nails” or “mortise-and-tenon joints,” which, through geometric interlocking, helps to hold the paint firmly to the substrate and prevent it from peeling off. Practical application principle: After the substrate is roughened (through sandblasting or grinding), its surface area increases and there are more gaps, which results in a significant improvement in adhesion ； However, if the coating cannot penetrate the gaps completely, the remaining bubbles will cause moisture to accumulate, thereby reducing adhesion. Typical application scenarios: Coating on sandblasted metal substrates, interlayer adhesion between old and new coatings, and the adhesion of electroplated metals to plastics all follow this mechanism. In the case of steel plates that have undergone phosphating treatment, the interlaced structure of the phosphating layer also provides numerous mechanical bonding points to enhance adhesion. All the theories recognized in the industry to explain the adhesion of paint coatings have been covered; there are no other independent mainstream theories. In actual painting processes, it is usually multiple mechanisms working together that provide adhesion.