“Pooja Pickling and Passivation Standard Practice for Cleaning, Descaling and Passivation of Stainless Steel Parts, Equipment and Systems is a valuable source of information on pickling and passivation treatments. Other sources of information may be obtained by contacting Pooja Pickling and Passivation.”
Passivation Services is a process that is separate from pickling, which can be performed on its own or after pickling. Unlike pickling, the passivation process does not remove any metal. Instead, the surface of the stainless steel is treated with an oxidizing acid, to dissolve carbon steel, sulfide inclusions and remove iron and other surface contaminants from the stainless.
Passivation is the treatment of the surface of stainless steels, often with acid solutions (or pastes), to remove contaminants and promote the formation of the passive film on a freshly created surface (e.g. through grinding, machining or mechanical damage).
Common passivation treatments include nitric acid (HNO3) solutions or pastes which will clean the steel surface of free iron contaminants. Care must be taken in selecting and using passivation treatments to ensure the selected treatment will target the contaminant. Passivation will also aid in the rapid development of the passive oxide film on the steel's surface. Passivation does not usually result in a marked change in appearance of the steel surface.
Both pickling and passivation solutions can employ dangerous acids that can damage both the operator and the environment if not handled correctly. Stainless pickling acids are highly corrosive to carbon steel. It is essential that all acids are thoroughly removed by rinsing the component after completing the process. Residual hydrofluoric acid will initiate pitting corrosion.