The reasons for pitting suppression with the application of US can be explained in terms of passivation mechanism. When stainless steel is exposed to water the protective layer is formed on the surface. This protective layer is believed to contain oxides of iron as well as alloying components. The addition of Cl ions into the solution leads to the destruction of the protective layer either with the formation of soluble substances or the replacement of adsorbed oxygen with Cl. When the concentration of Cl reaches certain value, the pittings are formed and corrosion starts. At this specific point further corrosion can be prevented if pits would be cleaned from Cl. This is done by US vibration. The vibrating plate accelerates the flow of solution along the surface and thus cleans forming pits from chloride.