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Metal Passivation Services
SR MFG provides chrome-free passivation to remove free iron and machining contaminants from stainless steel and other metals, restoring and stabilizing the passive layer to deliver more consistent corrosion resistance and reduce the risk of pitting or tea staining. We can align to specifications such as ASTM A967 and AMS 2700 as required, and provide lot-level processing records, traceability, and supporting verification reports—such as salt spray or copper sulfate testing—based on project-defined criteria. We also offer a free sample evaluation and can propose a material- and process-specific plan within 48 hours; to confirm the route and quote quickly, please share the alloy/grade, current surface condition, service environment, and corrosion-resistance target.
Passivation vs. Pickling/Descaling
Passivation and pickling are both chemical treatments, but they solve different problems. Neither is effective at removing heavy oils or grease, so parts typically need degreasing/cleaning first before pickling or passivation.
Pickling / descaling is used to remove rust products, oxide scale, and weld heat tint (heat-affected discoloration). It works by chemically stripping the affected surface layer and usually removes a very thin amount of base metal. For stainless steel, pickling commonly uses nitric + hydrofluoric acid chemistries.
Passivation is primarily used to remove surface contamination and free iron (including carbon-steel contamination) and to promote the formation or restoration of a continuous, stable chromium-rich passive film on stainless steel. Unlike pickling, passivation typically does not remove the base metal and usually has minimal impact on appearance.
In practical terms, pickling is the more aggressive process and often results in a more noticeable surface change (such as a duller, matte look) because it removes the affected surface layer. Passivation is generally less aggressive and is aimed at cleaning the surface and stabilizing the passive condition; it is not typically used to remove heat tint or oxide scale—that’s usually pickling/descaling.
For reference, the passive film on stainless steel is nanometer-scale, typically about 1–5 nm thick (roughly 0.00000004–0.0000002 inches).
Passivation Process Options We Offer
Chemical passivation (immersion or spray)
Parts are treated in a passivation solution—commonly nitric-based, citric-based, or an equivalent chemistry—to remove free iron and surface contaminants and to promote the formation or restoration of a stable passive state, improving corrosion-resistance consistency.
Pickling/descaling + passivation (pickling & passivation)
When the surface shows oxide scale, weld heat tint, or corrosion products, we perform pickling/descaling first (removing an extremely thin surface layer and stripping oxides), then passivate to remove free iron and restore corrosion performance.
Electrochemical finishing + passivation (optional)
For higher requirements on cleanliness, roughness, cleanability, or cosmetic uniformity, electrochemical finishing (such as electropolishing, which removes a very thin surface layer and refines the micro-surface) can be applied, followed by passivation and the required verification.
Note: The specific process route—chemistry, parameters, and verification methods (e.g., salt spray, high-humidity exposure, copper sulfate testing, etc.)—is determined by the alloy, surface condition, service environment, and applicable standards.
Metal Passivation FAQs
Metal Passivation Technical Resources
