Passivation

Applicable specifications

Frequently Asked Questions

• WHAT INDUSTRIES BENEFIT FROM PASSIVATION?
  • Medical and Pharmaceutical: Passivated stainless steel is crucial in manufacturing surgical instruments, implants, and medical devises, as it ensures sterility and prevents corrosion in critical applications.
  • Food and Beverage Processing: Stainless steel equipment used in food preparation must be corrosion-resistant and free of contaminants to maintain hygiene standards. Passivation ensures the cleanliness and durability of these surfaces.
  • Aerospace: In high-stakes applications like aerospace engineering, corrosion resistance is vital for the safety and longevity of aircraft components. Passivation ensures the integrity of metal parts used in these environments.
  • Marine: Marine environments are highly corrosive due to the presence of salt water. Passivated stainless steel is commonly used in shipbuilding, offshore structures, and other marine applications to prevent rust and degradation.
  • Chemical Processing: Equipment used in chemical processing must withstand exposure to corrosive substances. Passivation helps ensure the metal surfaces remain resistant to chemical attacks, extending the equipment’s service life.
  • Manufacturing and Industrial: In general manufacturing, stainless steel components that undergo passivation are more durable, Making them ideal for use in machines, tools, and equipment in a variety of industrial environments.
• WHAT ARE THE BENEFITS OF PASSIVATION?
  • Enhanced Corrosion Resistance: By removing surface impurities, passivation enables the stainless steel to self-heal and form a protective layer, significantly improving its resistance to rust and corrosion in harsh environments.
  • Increased Durability: Passivation extends the lifespan of stainless steel products, ensuring that they maintain their integrity and performance over time.
  • Improved Cleanliness: By eliminating contaminants, the process ensures a cleaner surface, which is particularly important where hygiene and contamination control are essential.
  • Aesthetic and Functional Integrity: The process preserves the appearance and smooth finish of stainless steel, ensuring it remains both visually appealing and functional.
• WHAT IS STAINLESS STEEL PASSIVATION?

  Stainless passivation is the process by which stainless steel will spontaneously form a chemically inactive surface when exposed to air or other oxygen-containing environments. Some important facts to know when considering passivating stainless steel:

  • Steels containing more than 11% Chromium can form an invisible, inert or passive, self-repairing oxide film on their surface. It is this passive layer that gives stainless steels their corrosion resistance.
  • If a stainless-steel surface is scratched, then more Chromium is exposed which reacts with oxygen allowing the passive layer to reform. However, if a particle of carbon steel is embedded in the scratch, then the passive layer cannot re-form, and corrosion will occur when the metal is wet or exposed to a corrosive environment.
  • Stainless passivation is the chemical treatment of a stainless-steel surface with a mild oxidant such as citric acid passivation solution. This process is to accelerate the process noted above.
  • Passivating stainless steel is the removal of exogenous iron or iron compounds from the surface by means of a chemical reaction, most typically by a treatment with a nitric acid passivation solution that will remove the surface contamination but will not significantly affect the stainless steel itself.
  • Passivation is also accomplished by stainless steel electropolishing. Electropolishing is an electrochemical process that is a super passivator of stainless steel and results in a more passive surface than the other methods mentioned above.

  This last step is necessary because during handling and processing such as rolling, forming, machining, pressing, tumbling, and lapping, particles of iron or tool steel or abrasive particles may be embedded in or smeared on or into the surfaces of stainless-steel components. If allowed to remain, these particles may corrode and produce rust spots on the stainless steel. This is due to the formation of a galvanic couple between two dissimilar metals that can promote a corrosive reaction. To dissolve the embedded or smeared iron and prevent this condition, as well as restore the original corrosion-resistant surface, semi-finished or finished parts are given a ‘passivation’ treatment.

• HOW STAINLESS STEEL IS PASSIVATED?

  The passivation of stainless steel is performed when free iron, oxide scale, rust, iron particles, metal chips or other nonvolatile deposits might adversely affect the metallurgical or sanitary condition or stability of the surface, the mechanical operation of a part, component, or system, or contaminate the process fluid. Stainless steel is passivated through a cleaning cycle to remove oils, grease, compounds, lubricants, and residue followed by a nitric or a citric acid bath or a by an oxidant that removes free iron and contaminates.

  Passivation is performed on clean stainless steel, providing the surface has been thoroughly cleaned or descaled. Since the term “passivation” is used to describe distinctly different operations or processes relating to stainless steels, it is necessary to define precisely what is meant by passivation.

  Electrolurgy is an industry leader in passivation services, delivering the highest quality passivated products to our customers since 1969. Here at Electrolurgy, we offer stainless steel passivation services with a focus on ASTM A967, ASTM A380, ASTM B912, and QQ-P-35C specifications. Call or contact us today to speak to a specialist at Electrolurgy about stainless steel passivating.