Product contact surfaces should be of base material without the use of coatings such as paint, powder coating, or plating. The materials most commonly used today are stainless steel and food grade plastics like UHMW. The surface finish of stainless steel that is fastest to clean would be smooth and polished. Standard 2B mill finish is fairly smooth, but (4B finish) produces a finer surface, while surfaces that undergo actual polishing treatments are the smoothest and most expensive of all. Passivation or some form of pickling process can remove or deactivate carbons that rise to the surface during welding or in the base metal itself to slow down or prevent the formation of oxides (rust) that create rough surfaces which can harbor bacteria. Bead-blasting that produces an attractive, uniform finish actually roughens the surface of the steel, and may not be considered a smooth finish. UHMW has natural lubricity and sheds itself of surface contaminants very quickly when acted upon by high pressure water.