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Citric Passivation of 410/420 Stainless

Anyone know the proper way to citric passivate 410/420 CRES stainless? We are using a proprietary citric-acid based solution, but after a while see rust after doing a corrosion test. I'm sure it has to do with how our process is set up. If an alkaline is necessary, any suggestions for an environmentally friendly one?

Thanks.

Ed Mendoza
medical device - Rancho Santa Margarita, California, United States
2004

Ed:

We get excellent results with the correct product using citric acid on these grades. We have customers with these grades who require the use of these products because of 80% reduction in corrosion problems compared to nitric passivation. Best overall results according to some steel manufacturers is AAA method, Alkaline/Citric/Alkaline.

You need to be using the best formulation of citric on these grades and at the correct time, concentration and temperature. Ultrasonics can benefit also. There are a variety of proprietary methods to achieve the best results.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2004

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