Passivation for SST
Stainless steels are auto-passivating in the sense that the protective passive film is formed spontaneously on exposure to air or moisture. The presence of exogenous surface contamination may interfere with the formation of the passive film. The cleaning of these contaminants from the stainless steel surface will facilitate the spontaneous passivation by allowing the oxygen uniform access to the surface. The passive film may be augmented by chemical treatments that provide an oxidizing environment for the stainless steel surface.
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.
Different types of stainless steel are selected on a basis of properties required, for example, corrosion resistance and design criteria, and fabrication requirements.
Passivation process is suitable for many sectors of industry :
- The Food industry
- The aircraft industry
- Pharmaceutical and medical instrument technology
- The automotive sector
- Machine and precision engineering (corrosion protection)