Chemical Passivation
Chemical Passivation Services in Houston, Texas
Harrison Electropolishing provides precision chemical passivation services for stainless steel and corrosion-resistant alloys. Our ISO 9001-certified facility in Houston uses both nitric and citric acid processes to restore corrosion resistance by removing free iron and surface contaminants left behind from machining, welding, or handling. We serve clients in aerospace, semiconductor, pharmaceutical, petrochemical, food-grade manufacturing, and more—helping ensure your components perform as engineered.
When to Passivate?
Because real-world fabrication and handling operations degrade the surface properties of the material, all corrosion-resistant alloys benefit from passivation prior to going into service. Passivation may also be performed on a routine preventative maintenance schedule. Some companies schedule routine passivation once a year while others passivate more frequently as a result of frequent high chloride levels.
What Is Chemical Passivation?
Passivation is a chemical process that enhances the natural corrosion resistance of stainless steel by removing surface contaminants—most notably free iron—that compromise the naturally occurring, protective oxide layer. These contaminants are often introduced during fabrication, welding, machining, or handling.
Passivation does not deposit a coating or change surface geometry. Instead, it restores stainless steel’s ability to self-protect in corrosive environments.
Key benefits of passivation:
- Removes embedded iron and surface contamination
- Restores the chromium-rich oxide layer on stainless steel
- Enhances long-term corrosion resistance
- Prepares the material to perform as it is engineered to perform.
When & Why to Passivate
Even when the correct alloy is selected for an application, it may still corrode if the surface is compromised. Passivation is critical after operations like grinding, welding, or forming, where free iron and oxides are introduced. Its is also essential for parts used in cleanroom, food, medical, or marine environments where any corrosion is unacceptable.
You should passivate when:
- Components undergo machining, welding, or abrasive finishing
- Parts will be used in harsh or corrosive environments
- Industry or customer standards require post-fabrication cleaning
- You're preparing stainless steel for high-purity applications
Passivation Specifications
| Name | Description |
|---|---|
| ASTM A967 | Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts |
| ASTM A380 | Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems |
| QQ-P-35C | Federal Specification: Passivation Treatments for Corrosion-Resistant Steel (replaced by ASTM A967) |
| ASTM B912 | Standard Specification for Passivation of Stainless Steel Using Electropolishing |
| ASTM B600 | Standard Guide for Descaling and Cleaning Titanium and Titanium Alloy Surfaces |
| MIL-S-5002 | Surface Treatments and Inorganic Coatings for Metal Surfaces of Weapon Systems |
| SAE AMS 2700E |
Passivation of Corrosion Resistant Steels |
Industry Standards We Meet
We adhere to stringent passivation standards to ensure full regulatory compliance and high-performance results. Our team can also accommodate custom specs for specialized applications.
Standards we follow:
- ASTM A967 – Chemical passivation treatments for stainless steel
- ASTM A380 – Cleaning and descaling of stainless steel parts
- AMS 2700 – Aerospace passivation requirements
- QQ‑P‑35 (obsolete, still referenced) – Federal passivation standard
- ATM B600 – Descaling and cleaning of Titanium
- Customer-specific specs – Medical, semiconductor, defense industry
Our Passivation Process
At Harrison Electropolishing, our process is designed to deliver, quality, consistency and traceability. Each part is handled in a controlled environment and treated to remove contaminants and ensure a clean, corrosion-resistant surface.
Our typical process includes:
- Pre-cleaning – Alkaline or ultrasonic cleaning to remove oils and particulates
- Passivation bath – Immersion in nitric or citric acid depending on material and requirements
- Final Cleaning – Rinsing in deionized water to remove residual acid
- Drying – Filtered Air or nitrogen drying or cleanroom drying depending on criticality
- Inspection – Visual and chemical testing based on standards and client specs
Nitric vs. Citric Acid Passivation
Choosing the right acid depends on the application, material, and environmental considerations. Both offer effective passivation, but have different properties and use cases.
Comparison of acid types:
- Nitric Acid: Traditional, aggressive cleaning; effective on heavy contamination; regulated for environmental concerns
- Citric Acid: Biodegradable, non-toxic, safer for sensitive applications (medical, food, pharmaceutical); growing industry preference
Alloy-Specific: Some materials respond better to one acid type over the other (e.g., 300-series stainless vs. 400-series)
Passivation Applications
Harrison is a leader in passivation services for the following industries and applications:
- Marine
- Paper & Pulp
- Petrochemical
- Pharmaceutical
- Semiconductor
- Oil & Gas
- Biotech
- Polymer
- Solar
- Nuclear
Testing & Quality Assurance
We perform thorough inspection and testing to ensure parts meet or exceed industry standards after passivation. This is critical for safety, compliance, and performance.
Our testing capabilities include:
- Copper sulfate test – Visual test for free iron on stainless steel surfaces. A brown or copper-colored deposit indicates the presence of free iron.
- Ferroxyl test – Visual test for free iron on stainless steel surfaces. A blue coloration indicates the presence of free iron.
- Documentation – Certificates of compliance, inspection records, and traceability reports available
Clean Packaging & Traceability
Once passivated, parts are carefully packaged to prevent recontamination. We offer cleanroom packaging for critical components and assemblies.
Packaging options:
- Clean, double-bagged packaging for medical or food-grade parts
- Vacuum-sealed packaging
- Labeling for full traceability
- Customer-specified packaging instructions accommodated
Materials We Passivate
We work with a wide range of corrosion-resistant materials commonly used in industrial and high-purity environments. Whether it’s a small fitting or a large tank, we have the capability and experience to deliver high-quality results.
Common materials include:
- Stainless steels (200, 300 and 400 Series)
- Duplex and super duplex stainless steel
- Nickel alloys (Inconel, Hastelloy)
Passivation vs. Pickling vs. Electropolishing
While all three processes improve surface condition, they serve different functions.
Know the difference:
- Passivation: Removes free iron without changing surface finish
- Pickling: Removes scale, weld oxides, and surface damage (often pre-passivation)
- Electropolishing: Smooths the surface, removes metal, and enhances appearance and corrosion resistance
We often combine processes for optimal results depending on part condition and application.
