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 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 or Citrajet 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 must 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.
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