Promoting stainless steel’s natural corrosion resistance through passivation

New England Electropolishing

Promoting stainless steel’s natural corrosion resistance through passivation

Passivation restores the corrosion-resistant layer on the surface of stainless steel manufactured parts.

Stainless steel’s reputation for corrosion resistance is due to a thin, oxygen-enriched layer of chromium that normally occurs on the metal’s surface. When manufacturers cut, weld and machine stainless steel to create a product, they embed free iron and other impurities in the metal. Those impurities react with harsh environments, such as salt-water, chlorine and other chemicals, and eventually cause parts to rust.

Passivation removes contaminants from the metal’s surface that inhibit the formation of the protective chromium oxide layer, which makes stainless steel highly corrosion resistant.

What is the most effective passivation method? Scientific studies point to electropolishing. An abbreviated cycle meets or exceeds the results of such traditional means as nitric acid immersion and citric acid immersion.

That is because electropolishing removes all free iron, reaching impurities embedded below the surface that traditional methods can’t treat. 

By eliminating free iron completely, the process immediately terminates the potential for free iron corrosion and enables stainless steel to form a greater protective layer than chemical passivation methods allow.

Morevover, the corrosion resistance is compliant with ASTM B 912-02 and ASTM A967-13, “Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts.”

At New England Electropolishing, we recommend electropolishing to enable the growth of a natural, inert, oxide layer on all grades of stainless steel. We also offer the nitric and citric acid immersion passivation, however, and recognize there are times when they might be preferable. We look forward to talking to you about which process is best suited for your stainless steel products.


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