Citric Passivation



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 Q. Mr. Schulte, I read with interest the item in your column, “Wicked Passivation Fumes,” in the Sept. 2009 issue of Products Finishing magazine.

  You explained very well the necessary steps for proper ventilation of a nitric acid passivation tank. There is another solution that C.D. might consider, using instead a citric acid based passivation bath. Citric acid solutions produce no hazardous fumes.
Perhaps he has been required by his customer to use nitric acid. Unfortunately, that is still common. C.D. and your other readers may be interested in a report by the State of New York discussing the environmental advantages of citric acid passivation over nitric acid passivation. It can be accessed on the Web at controlelectropolishing.com/CEC_Pollution_Prevention.pdf.   R.K.
A. Thank you for your response, R.K. I am familiar with citric acid passivation and its environmental benefits, especially in terms of reduced air pollution. Thanks for the link to the informative R&D report.