Sponsored What is Passivation?

Passivation is a critical process in the maintenance and enhancement of stainless-steel equipment. It is indispensable for new stainless-steel equipment.

The passivation process is a chemical treatment process that effectively transforms the top layer of stainless steel. The process allows the surface to bond with oxygen and create a protective Chromium Oxide layer. This shifts the stainless steel surface from an “active” to a “passive” state. The transformation significantly diminishes the metal’s reactivity, reducing the likelihood of rust formation.

During the manufacturing and handling of stainless steel, its surface can get contaminated with iron particles and other impurities. These contaminants can compromise the naturally corrosion-resistant properties of stainless steel by providing sites for rust and corrosion to initiate. Passivation effectively cleans the surface and allows the metal to form its protective oxide layer more uniformly and effectively.

Passivation is not just a recommended treatment, it’s a necessary step in the lifecycle of stainless steel equipment. It plays a pivotal role in maximizing the performance and durability of stainless steel, particularly when it is newly manufactured and most vulnerable to surface contamination.

Why is Passivation Necessary?

1. Removing Contaminants – During fabrication, stainless steel surfaces become contaminated with iron particles or other foreign matter. These contaminants act as initiation sites for corrosion. Passivation removes these contaminants, reducing the risk of rust and corrosion.
2. Restoring Chromium Oxide Layer – Manufacturing processes like welding, machining, or forming can disrupt the natural chromium oxide layer on stainless steel. Passivation helps re-establish this protective layer.
3. Increasing Equipment Lifespan – By preventing premature corrosion, passivation extends the functional life of stainless steel equipment. This is particularly crucial in industries where equipment reliability and longevity are a necessity.
4. Ensuring Cleanliness and Hygiene – Industries like food and beverage processing, pharmaceuticals, and cosmetics require cleanliness of equipment. Passivation ensures that the surfaces of stainless steel equipment are free from contaminants. This creates a sanitary, safe, and hygienic environment.
5. Compliance with Industry Standards – Many industries have strict standards and regulations regarding equipment maintenance, sanitation, and safety. Passivation is often a required process to comply with these standards, especially for new equipment.
6. Optimizing Performance – The long-term performance of stainless steel equipment is closely linked to its surface condition. Passivation ensures that the surface is in optimal condition. This is critical in applications where sanitation is essential.

Preparing for Passivation

Preparing for the passivation of stainless steel is a meticulous process involving several key steps to ensure the treatment is effective and safe. Here is a thorough guide to preparing for stainless steel passivation.

1. Safety Precautions

• • Personal Protective Equipment (PPE): Ensure all personnel involved in the passivation process are equipped with appropriate PPE. This includes gloves, goggles, face shields and protective clothing.
  • Ventilation: Provide adequate ventilation in the area where passivation is to be performed, especially when using acid-based solutions.
  • Prepare for Emergencies: Have emergency equipment like eyewash stations, water hoses, and neutralizing agents readily available in case of accidental spills or exposure.

2. Initial Inspection 

• • Inspect the Equipment: Before passivation, thoroughly inspect the stainless steel equipment for any signs of contamination, damage, or imperfections. Look for rust, corrosion, scratches, pitting, or other surface defects.
  • Identify Parts for Manual Cleaning: Some parts may need to be disassembled for manual cleaning and passivation.
  • Check Gaskets and Seals: Make sure the materials used in gaskets and seals on equipment can withstand the passivation chemicals, temperatures, and durations of the process.

3. Cleaning and Degreasing

• • Clean the Surface: The stainless steel must be cleaned of any dirt, grease, and other contaminants. This can be done using appropriate cleaning agents and methods suited to the type of contamination.
  • Apply Degreaser: Use a suitable degreasing agent to remove any oils, lubricants, or greases from the surface. The choice of degreaser will depend on the specific contaminants. Please refer to your chemical supplier’s recommendations.
  • Rinse Thoroughly: After degreasing, rinse the equipment thoroughly with water to remove any residual cleaning agent. The rinse water should be of high purity, as impurities in water can lead to staining or corrosion.

4. Surface Evaluation

• • Visual Inspection: After cleaning and degreasing, visually inspect the surface again to ensure it is free from contaminants. Any remaining residues can affect the passivation process.
  • Repeat if Necessary: Before proceeding with the passivation process, it is imperative to thoroughly check the surface of the stainless steel for any signs of dirt or contamination. If the inspection reveals residual contaminants or grime, it is necessary to repeat the cleaning and degreasing cycle to ensure the surface is optimally prepared for effective passivation.

5. Reviewing Protocols and Procedures

• • Follow Manufacturer Guidelines: Review the guidelines provided by the chemical supplier for specific instructions on the passivation process.
  • Training: Ensure that all personnel involved are trained and familiar with the passivation process and safety procedures.

6. Final Checks

• • Leak Testing: If the passivation process involves circulating the solution through a CIP system, check for leaks before adding the passivation solution.
  • Documentation: Have all necessary documentation and record-keeping materials ready for noting down observations and results.

Passivation Procedure

After successfully completing the preparation phase, you’re now ready to embark on the actual passivation process. It’s crucial to contact your local chemical supplier for specific chemical dosing ratios and recommended procedures. These can vary based on the product’s heat and time requirements. We strongly encourage you to consult with local suppliers to explore chemical options that suit your unique requirements or preferences.

1. Prepare Acid Solution – Typically, a nitric acid or citric acid solution is used. Nitric acid is traditional choice for its effectiveness. However, it requires careful handling due to its corrosive nature. Citric acid is milder and more environmentally friendly option. The concentration of the acid and the duration of the treatment vary based on the type of stainless steel and the specific requirements of the equipment.
   Mix acid with water according to the recommended ratio. Always add acid to water, not the other way around to prevent dangerous reactions.
2. Circulation and Treatment – The acid solution is circulated through the system at a specified temperature (usually around 60°C or 140°F) for a set duration. Refer to your chemical supplier for appropriate heat and time requirements.
3. Rinsing and Neutralizing: – After the acid treatment the system must be thoroughly rinsed with water to remove all traces of the acid. The acid solution should be neutralized before disposal according to environmental regulations.
4. Drying – Allow the equipment to air dry completely, typically for 24 hours. This ensures the formation of the passive layer.
5. Post-Passivation Steps – Before starting the equipment for its intended use, perform a complete cleaning and sanitizing program.
6. Safety and Environmental Considerations – Dispose of or neutralize chemicals in an environmentally responsible manner according to requirements of local and state authorities.

Preparing for passivation requires attention to detail, strict adherence to safety standards, and a comprehensive understanding of the equipment and materials involved. The general guidelines and detailed procedures outlined above will provide you with a solid foundation. It is always imperative to consult with chemical suppliers for specific, tailored advice. Proper passivation is a strategic investment in the integrity and long-term performance of stainless steel.

For further details or inquiries about the passivation process, we encourage you to contact a representative at MARKS. Our team comprises experienced professionals who are well-versed in the passivation process. We can provide you with advice and facilitate connections with the appropriate experts. At MARKS, we are committed to assisting you in maximizing the efficiency and longevity of your new equipment. Our goal is to guide and support you every step of the way, ensuring you get the best possible return on your investment.

About MARKS: MARKS Design and Metalworks is a manufacturer of American-made brewery equipment.  We are proud to build equipment using stainless steel sheet goods manufactured in U.S. steel mills.  Our highly skilled American welders and fabricators craft the finest brewery equipment on the market.  We take pride in our craftsmanship.