Chemical Considerations

Limitations of Traditional Stainless-Steel Passivation Methods

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For decades, the pharmaceutical, biotechnology, and medical device industries have relied on nitric acid, phosphoric acid, and electropolishing to clean and passivate austenitic stainless steel. While these methods may deliver short-term results, they frequently fail in long-term corrosive service environments, including WFI and clean steam systems.

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Why Mineral Acids Fall Short

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Research shows that most stainless-steel pitting corrosion originates at sulfide inclusions, particularly manganese sulfide (MnS). Nitric acid effectively removes these inclusions from the surface, but it cannot dissolve aluminum—a major contaminant in modern stainless steels. Once sulfide sites are removed, aluminum inclusions become the primary corrosion initiation points, accelerating localized attack.

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Phosphoric acid removes ferric oxide and can increase surface chromium by selectively dissolving iron. However, like nitric acid, it does not address aluminum inclusions, leaving critical corrosion mechanisms unresolved.

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The Misconception of Electropolishing

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Electropolishing is often mistaken for a true passivation solution. In reality, it is a chemical-electrical surface leveling process that smooths surface roughness without dissolving embedded impurities. In many cases, contaminated electrolytes can introduce new surface contaminants, further compromising corrosion resistance.

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The C.I.P. Chelation-Based Passivation Advantage

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Consultation In Passivation (C.I.P.) utilizes biodegradable organic chelation chemistry to remove corrosion products, inclusions, and sub-surface contaminants. This approach is non-toxic, non-corrosive, and significantly safer than mineral acids—and remains the only proven method for achieving true, long-term stainless-steel passivity.

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Our processes integrate advanced chemical and metallurgical principles, targeting the root causes of corrosion rather than masking symptoms.

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Precision Passivation—Not “Standard Recipes”

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No two stainless-steel systems are identical. Assuming a single “standard procedure” can produce consistent passivation results is technically unsound. Passivity is not visually detectable and must be confirmed using scientific instrumentation and quantitative analysis.

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C.I.P.’s pH-controlled, multi-stage precision cleaning and passivation process is tailored through on-site metallurgical evaluation. Chemistry, sequencing, and operating parameters are fine-tuned for each system to ensure reproducible, verifiable results.

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Critical Process Controls for Long-Term Corrosion Resistance

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Effective passivation requires strict control of:

• Chemical concentration

• Operating temperature

• Flow velocity and contact time

• Buffered formulations and pH stability

• Elimination of halogens

• Prevention of ferric ion corrosion

• Control of iron precipitation

• Proper rinsing between stages

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These controls are essential—not optional—for achieving durable corrosion resistance and maintaining critical stainless-steel systems.