At US Corrosion Services, we believe stainless steel should stay stainless. That’s why we offer the ASTM A380 Ferroxyl Test—a simple but powerful technique for detecting iron contamination or improper passivation on stainless steel components.
Whether you’re fabricating new vessels, repairing legacy piping systems, or verifying surface treatments on architectural elements, the Ferroxyl Test is your early-warning system for rust-prone surprises. If you’ve ever seen a “tea stain” on stainless steel and wondered why?, this test holds the answer.
What Is the Ferroxyl Test?
The Ferroxyl Test, as described in ASTM A380 and ASTM A967, is used to detect free iron particles or iron residues on the surface of stainless steel. These tiny traces – left behind during fabrication, grinding, machining, or exposure to carbon steel – can act like a corrosion starter kit, especially in harsh service environments.
The test works by applying a solution containing a mixture of:
- Potassium ferricyanide
- Nitric acid
- Deionized water
If free iron is present on the surface, the solution reacts and forms Prussian Blue, a distinct blue stain that shows up like a crime scene for corrosion.
🔍 Translation: If it’s turning blue, it’s contaminated – and that’s bad news for your stainless steel.
Why Use It?
✅ Quality Assurance for Welded or Machined Parts
Confirm that welding, grinding, or heat treatment hasn’t introduced rogue iron particles that could later cause pitting or crevice corrosion.
✅ Post-Cleaning and Pickling Validation
Verify that passivation or chemical cleaning was effective and left the surface iron-free.
✅ Field Checks for In-Service Equipment
Spot-check suspect components on-site—especially those showing signs of staining or discoloration—to determine if maintenance is needed.
Ferroxyl Test Applications
The ferroxyl test can be used in a wide range of applications and industries. A few examples of locations we’ve tested include:
- Heat Exchangers
- Food & Pharma Equipment
- Architectural Stainless Features
- Pressure Vessels & Piping
- Power Generation Systems
- Marine & Coastal Installations
Basically, if your component lives in a wet, warm, or salty environment, it’s worth checking!
But Wait—There’s More: Ferroxyl Testing Beyond Stainless Steel
While originally developed for stainless, Ferroxyl can also help in non-traditional applications, including:
🎨 Coating Adhesion Checks
Use the test to assess whether a coating system is fully covered and preventing underfilm corrosion. If iron appears beneath a coating, it’s a signal that the bond is failing—or worse, corrosion is already at work.
🔍 Surface Prep Validation
Use before and after blasting or chemical cleaning to detect whether embedded iron has been effectively removed from substrates like aluminum or non-ferrous metals.
⚠️ Cross-Contamination Detection
Working in a mixed-metal environment? Ferroxyl is a quick, visual way to confirm that stainless hasn’t been contaminated by nearby carbon steel processing.
Ferroxyl testing of a welded stainless component in which steel was accidentally used for welding.
Our Ferroxyl Testing Process
At US Corrosion Services, we tailor our approach based on your equipment and industry:
- In-Lab Testing – Bring us your parts or coupons and we’ll perform controlled testing with high-resolution documentation.
- Field Testing – Our portable Ferroxyl assessments allow us to test in refineries, plants, or fabrication shops, delivering real-time answers and immediate remediation advice.
- Digital Reporting – Every test comes with annotated photos, interpretations, and clear next steps—perfect for QA documentation or maintenance planning.
Related Standards & Guidelines
- ASTM A380 – Cleaning, Descaling, and Passivation of Stainless Steel Parts
- ASTM A967 – Chemical Passivation Treatments for Stainless Steel Parts
- NACE MR0175 / ISO 15156 – Use in sour service applications
- SSPC-SP COM – Guidelines on coating surface prep
- AMPP Coating Inspection Practices – Optional follow-up coating verification
Why Choose US Corrosion Services?
🎓 Deep Technical Knowledge
We’re not just doing the test—we understand the metallurgy behind it. If you’ve got surface contamination, we can trace it back to the root cause and help you mitigate the problem.
🛠️ Versatility in the Field
Our team is trained for on-site corrosion testing, even in high-security or hazardous locations like power plants and offshore platforms.
📷 Visual Proof
We deliver crystal-clear photo evidence with marked problem areas, perfect for reports, maintenance planning, or warranty claims.
🧪 Integrated Services
If we find iron, we can help you clean it, re-passivate it, or protect it—with expert coating evaluation, cathodic protection design, and integrity management strategies.
Let’s Catch Corrosion Before It Starts
If you suspect surface contamination, don’t wait until rust appears. The Ferroxyl Test is fast, affordable, and highly effective—and US Corrosion Services has the expertise to go beyond test results and into real-world corrosion solutions.
📞 Contact us today to schedule a lab test, request a field inspection, or ask us about integrating Ferroxyl testing into your QA program: