Categorized | Citrajet, Citranox, Medical Device

Passivation of Stainless Steel: Citric Acid Option

Q. Surface contamination interferes with formation of protective oxide coating on stainless steel thereby leaving it open to corrosion. The stainless steel needs passivation.  Can Alconox, Inc. help?

A. Stainless steels are autopassivating in the sense that the protective oxide passive film is formed spontaneously on exposure to air or moisture. Surface contamination, may interfere with the formation of the passive film. The cleaning of these contaminants from the stainless steel surface with citric acid detergent will facilitate passivation by allowing the oxygen access to the surface.

Passivate by immersing the stainless steel in either a 30% solution (300mL/L) of Citranox® Liquid Acid Cleaner and Detergent or Citrajet® Low-Foam Liquid Acid Cleaner/Rinse at any of the following combination of time and temperature: 70-120 deg F (21-49 deg C)/20 min, 120-140 deg F (49-60 deg C)/10 min, or 140-160 deg F (60-71 deg C)/4 minutes.

Rinse thoroughly immediately after passivation. Final rinse should be in clean water with a final reading of less than 200 ppm total solids. Neutralization is not required. Air oxidation will complete passivation.  Note that this process conforms to ASTM A967-01 Standard Specification for Chemical Passivation Treatments of Stainless Steel Parts.

If desired, Ferritic and Martensitic steels can be treated with 5% sodium dichromate at 150 deg F (65 deg C) for 30 min to accelerate surface oxidation to form passive oxide layer.

To request these, or any Alconox, Inc. detergents for free, please complete the questionnaire at Get Sample.  For more information about any one of our Alconox, Inc. detergents, consult the technical bulletin for each product. Or click here to access each of our detergent’s  Safety Data Sheets.

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Contact us any time: cleaning@alconox.com