The effect of substrate roughness on the adhesion strength of a polymer coating can be significant. The adhesion strength between a substrate and a polymer coating is influenced by several factors, including the surface roughness of the substrate, the chemical composition of the substrate and the coating, and the application method of the coating.In general, increasing the surface roughness of a substrate can lead to improved adhesion strength of a polymer coating. This is because a rougher surface provides a larger surface area for the coating to bond with, as well as more opportunities for mechanical interlocking between the coating and the substrate. Mechanical interlocking occurs when the coating penetrates into the valleys and asperities of the rough surface, creating a stronger bond between the two materials.However, there is an optimal level of roughness for achieving maximum adhesion strength. If the surface roughness is too high, it can lead to defects in the coating, such as voids or pinholes, which can compromise the overall performance of the coating. Additionally, if the surface is too rough, the coating may not be able to fully penetrate into the valleys of the rough surface, leading to weaker adhesion.The optimal level of substrate roughness for maximum adhesion strength depends on the specific polymer coating and substrate materials being used, as well as the application method. In general, it is important to carefully control and optimize the surface roughness of the substrate to achieve the desired adhesion strength and overall performance of the polymer coating.