During processing operations such as forming, machining, tumbling, and lapping, iron particles
or other foreign particles may become smeared over or imbedded into the surface of stainless
steel parts. These particles must be removed or they will appear as rust or stain spots. This
condition may be prevented by passivating the parts to remove the iron particles or other
foreign particles, and then allowing the passive film to form on the cleaned surface, with or
without chemical enhancement of the formation of this oxide film.