As defined in MIL-STD-753C, the Passivation process is the final treatment/cleaning process used to remove iron from the surface of corrosion resistant steel parts such that a more uniform formation of a passive surface is obtained thus enhancing corrosion resistance.
Stainless steel is different from other metals in that as you get closer to the surface the composition of the metal actually changes. In the passivation process, free iron is removed from the surface into solution, leaving behind a higher chromium level. A good chrome to iron ratio is usually considered to be 1.5 to 1 or higher.
Passivation Achieves 3 Things:
1). Removal of surface contamination (metal oxides, inclusions, fabrication debris and bio-contamination).
2). Improvement or formation of the passive (inert) layer for increased corrosion resistance.
3). Reduce corrosion vulnerability and lower product contamination potential.
This treatment process of course also extends system maintenance intervals as well as meets cGMP/BPE surface quality requirements
Astro Pak Services and Capabilities
Ultrapass passivation is provided in our state of the art cleanroom facilities and at Clients high purity locations. Nitric acid as well as citric acid chelant passivation modalities can be utilized based on site specific requirements. Cleaning and passivation can be provided for pre-commissioning of new construction or maintenance and shutdown efforts. Immediate response for emergency outages and critical utilities are routinely provided. Passivation is performed in conjunction with pickling of weld area defects, derouging of corrosion coloration films, and new additions or replacement equipment. Professional consulting by our known industry experts with many years of experience, benefits our clients with their difficult issues.