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Passivation

A chemical treatment that restores stainless steel's corrosion resistance after machining by removing embedded free iron.

What is Passivation?

A chemical treatment for stainless steel that removes free iron and other surface contaminants left behind by machining, restoring the material's natural corrosion resistance.

How it works

Parts are immersed in a nitric or citric acid bath per ASTM A967, which dissolves free iron particles embedded in the surface during machining without attacking the base chromium-nickel matrix. This lets the chromium oxide layer that gives stainless steel its corrosion resistance reform cleanly across the whole surface.

Benefits

  • Restores full corrosion resistance after machining
  • No visual or dimensional change to the part
  • Required by many medical and food-contact stainless specs
  • Inexpensive relative to plating

Applications

Standard finishing step for stainless steel medical, food-contact, and marine-environment parts, and commonly specified by default on any close-tolerance stainless component.

Passivation example

Applicable Materials & Colors

Steel, stainless steel. Full applicable-materials list, color range, and which finishes can combine are confirmed per order — see the Materials & Finishes page →

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