Passivation in Biopharma: Protecting Stainless Steel to Protect Product Quality
In biopharmaceutical manufacturing, stainless steel is everywhere, from reactors and vessels to piping, valves, and clean-in-place (CIP) systems. But simply installing stainless steel equipment isn’t enough to provide product safety or regulatory compliance. Without proper treatment, stainless steel can corrode, leach metals, harbor contaminants, and eventually compromise product quality.
That’s where passivation comes in. Passivation is a critical but often misunderstood process that protects stainless steel surfaces, preserves sterility, and supports consistent, high-quality biopharma production. The Gl Technologies team takes a look at what passivation is, why it matters in biopharma, how it works, and what happens when it’s overlooked.
What Is Passivation?
Passivation is a chemical treatment process that improves the natural corrosion resistance of stainless steel. While stainless steel already forms a thin chromium oxide layer when exposed to oxygen, manufacturing, fabrication, welding, and handling can damage or contaminate this protective film.
During passivation, stainless steel is treated with an acid solution, typically nitric acid or citric acid, to remove free iron and surface contaminants. This allows a uniform, stable chromium-rich oxide layer to re-form, creating a passive surface that resists corrosion and contamination.
In biopharma environments, where purity is non-negotiable, passivation is not optional, it’s foundational.
Why Passivation Is Critical in Biopharmaceutical Manufacturing
1. Prevents Corrosion and Metal Contamination
Even high-grade stainless steel can corrode under harsh conditions. Acids, cleaning chemicals, heat, and moisture used in biopharma processing can break down unprotected surfaces. When corrosion occurs, metal ions such as iron, nickel, or chromium may leach into the product stream, putting batches at risk.
Passivation dramatically reduces this risk by stabilizing the steel surface and preventing reactive metal exposure.
2. Protects Product Quality and Patient Safety
Biopharmaceutical products are extremely sensitive. Trace contaminants can impact protein stability, potency, and sterility. A compromised stainless steel surface can introduce particulates or catalyze unwanted chemical reactions.
By maintaining a clean, inert surface, passivation helps make sure drug products meet purity and safety expectations from development through commercialization.
3. Supports GMP and Regulatory Compliance
Regulatory bodies such as the U.S. Food and Drug Administration require manufacturers to demonstrate control over materials, equipment, and processes that contact pharmaceutical products. Proper passivation aligns with Good Manufacturing Practices (GMP) by:
Minimizing contamination risk
Improving cleanability and inspectability
Supporting validated CIP and SIP (steam-in-place) processes
Reducing deviations, investigations, and batch failures
In audits, poorly maintained stainless steel surfaces are a common red flag.
Common Causes of Stainless Steel Degradation in Biopharma
Even well-designed systems can lose passivity over time. Common contributors include:
Welding and heat-affected zones that disrupt oxide layers
Mechanical polishing or abrasion during maintenance
Aggressive CIP chemicals such as chlorides and acids
High-purity water exposure, including WFI and RO systems
Extended downtime in humid or oxygen-deprived conditions
Without routine evaluation and re-passivation, stainless steel surfaces can silently deteriorate.
How the Passivation Process Works
While procedures may vary by facility and application, passivation typically involves the following steps:
1. Pre-Cleaning
Before passivation, surfaces must be thoroughly cleaned to remove oils, greases, weld residue, and organic contaminants. Inadequate cleaning can prevent proper oxide layer formation.
2. Acid Treatment
An acid solution, most commonly nitric or citric acid, is circulated or applied to the stainless steel surface. This step dissolves free iron and embedded particles without damaging the base metal.
Nitric acid: Traditional, highly effective, but more hazardous
Citric acid: Safer, more environmentally friendly, increasingly popular
3. Rinsing and Neutralization
After acid exposure, systems are thoroughly rinsed with high-purity water to remove residual chemicals. Neutralization ensures no acid remains that could affect subsequent processes.
4. Verification and Testing
Passivation effectiveness is often verified using surface tests such as:
Water break tests
Copper sulfate tests
Advanced surface analysis (when required)
Documentation is essential for GMP compliance.
When Should Passivation Be Performed?
Passivation is not a one-time event. In biopharma environments, it should be performed:
After new equipment installation
Following welding, repairs, or modifications
During system commissioning and validation
If rouging, corrosion, or discoloration is observed
As part of preventive maintenance programs
Facilities that treat passivation as routine maintenance, not an emergency fix, experience fewer compliance issues and longer equipment life.
Passivation vs. Cleaning: What’s the Difference?
A common misconception is that CIP cleaning replaces passivation. It doesn’t.
Cleaning removes product residues and organic contaminants
Passivation restores and protects the metal surface itself
Cleaning keeps equipment sanitary; passivation keeps it chemically stable. Both are necessary for a robust contamination-control strategy.
The Cost of Skipping Passivation
Failing to properly passivate stainless steel can lead to:
Product contamination or batch loss
Unexpected corrosion and equipment failure
Failed audits and regulatory findings
Increased maintenance and downtime
Damage to brand reputation and patient trust
Compared to these risks, passivation is a relatively low-cost investment with high returns.
Best Practices for Biopharma Passivation Programs
To get the most value from passivation, biopharma manufacturers should:
Use qualified vendors experienced in GMP environments
Maintain clear SOPs for passivation and verification
Integrate passivation into asset management and CMMS systems
Document all activities for audit readiness
Coordinate passivation with CIP, calibration, and validation schedules
Proactive planning ensures passivation supports—not disrupts—production timelines.
Protect the Steel, Protect the Product
In biopharmaceutical manufacturing, product quality is inseparable from equipment integrity. Stainless steel may look flawless on the surface, but without proper passivation, unseen risks can undermine even the most advanced processes.
By investing in effective passivation programs, biopharma facilities protect their equipment, preserve product purity, and uphold the standards patients and regulators demand. In short, protecting stainless steel is protecting product quality—and passivation is the silent guardian that makes it happen.
About GL Technologies
GL Technologies, based in San Diego, is a specialized service provider catering to the highly regulated industries of biopharmaceuticals, pharmaceuticals, medical devices, and government sectors. The company focuses on delivering expert solutions in equipment calibration, validation, and compliance services, ensuring that clients meet stringent GMP (Good Manufacturing Practice) and FDA regulations. GL technologies is a trusted partner from commissioning new plants to decommissioning with compliance. GL can place dedicated motivated quality personnel on site anywhere. A program can be designed or revamped for the customers needs from design of CMMS to SOP development, specification development and performance of calibrations.
With a dedicated team of 29 technicians, GL Technologies offers precision calibration, preventative maintenance, and qualification services for laboratory and production equipment used in critical manufacturing and research processes. The company’s expertise is supporting its clients in maintaining regulatory compliance and operational efficiency.
As a full-service company specializing in equipment calibration, repair, and certification services for biopharmaceutical, pharmaceutical, and medical device industries. Our team has extensive experience working with sPRT calibrations along with CMMS software, HPLC OQ validation, and fume hood certifications. Companies of all sizes rely on our team to implement, maintain, and keep their research and manufacturing processes compliant with regulatory standards. Other specialties include building maintenance systems, and mass spectrometry calibrations. GL Tec specializes in IQ OQ PQ services for clients throughout San Diego, San Francisco, Los Angeles, Orange County, and Riverside!