What is Passivation?

Passivation is a treatment and cleaning process used to remove iron from the surface of corrosion resistant steel parts. Chemical passivation forms a more uniform passive layer thus enhancing the corrosion resistance of the metal’s surface. The passive layer, which is sometimes called the passive film, is responsible for providing corrosion resistance at the surface of the metal. It is a very thin layer of highly stable metal atoms that do not easily corrode or rust.

Stainless steel is different from other metals in that as you move from deep within the alloy and get closer to the surface, the composition of the metal actually changes.  In the passivation process, free iron is removed from the surface, leaving behind a higher chromium to iron ratio.  For the most common austenitic stainless steels such as 304L and 316L, a good chrome to iron ratio is usually considered to be 1.5 to 1 or higher. The chrome to iron ratio does vary with different stainless steel alloys. Chromium is very stable and corrosion-resistant, but iron is prone to corrosion, so improving the chromium to iron ratio improves the corrosion resistance of the surface.


Benefits of Passivation:

There are many benefits of passivation on equipment and systems:

1.) Removal of surface contamination (metal oxides, inclusions, fabrication debris and tramp iron).

2). Improvement of the passive (inert) layer for increased corrosion resistance (higher chrome to iron ratio and a thicker passive film)

3). Reduce corrosion vulnerability and decreases product contamination potential.

4.) Passivation also extends system maintenance intervals as well as meets cGMP/BPE surface quality requirements


Trust the Experts in Passivation

For over 50 years, Astro Pak has been perfecting the chemistry and cleaning process of Passivation. Our proprietary chemistry, UltraPass® is a chemical treatment for stainless steel and other metals that enhances the ability of the treated surfaces to resist corrosion.

Astro Pak delivers chemical cleaning & passivation services to installed systems: pre-operational, pre-commissioning of new construction, post modification, or for maintenance during shut-downs. Whether it is UltraPass®, nitric acid, or other chemistries, we can process piping, fittings, vessels or other types of equipment. In addition to our expertise in circulating chemistry through facility equipment, tanks, and distribution systems, we also have a Gel Passivation process to address surface discoloration, spot rouge, HAZ of welds, or corrosion on most exterior surfaces. We can perform our work at customer facilities or in one of our shops which are located nationwide.

We routinely respond to emergency situations for critical utilities, systems and equipment. When our job is completed, you will receive cGMP compliant documentation packages for your systems and equipment maintenance records.

Systems & Equipment Experience

  • Process and Storage Vessels and Tanks
  • Product and Distribution Piping
  • Water for Injection (WFI) Tanks and Stills
  • Bioreactors, Fermenters, Lyophilizes
  • Clean Steam Generators and Clean Steam Systems
  • Sterilizers and Autoclaves
  • Reverse Osmosis, DI, Pure Water
  • Clean in Place (CIP)
  • Boilers
  • Heat Exchangers
  • Tubing and Hoses
  • Spools, Flanges, Gaskets
  • Valves (Relief, Ball, Butterfly, Needle, Gate)
  • Gauges (Pressure, Flow meter, Hydraulic, Cryogenic)
  • Fittings, Fasteners
  • Components and Hardware
  • Transducers and Sensors
  • Any stainless steel parts, equipment or systems


  • ASTM A380
  • ASTM A967
  • ASME BPE 2012 Bioprocessing Equipment
  • SEMATECH Passivation requirements
  • AMS 2700
  • ASTM F86
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