Plating Q&A: Citric Acid Passivation
How to passivate stainless steel electrodes with citric acid.
Q. We want to passivate stainless steel electrodes using citric acid. We have some information that suggests the process should be performed at approximately 150°F for 30 minutes using a 10 percent solution of citric acid. This temperature is higher than we would like. Can we modify the operating conditions, such as lowering the temperature, and still get satisfactory results?
A. You should be able to reduce the temperature by 10°F, and by doubling or tripling the process time, get satisfactory results. Citric acid passivation is now widely used in the metal finishing industry. You can find a lot of information on this process by going to the PFonline.com database and searching under citric acid passivation. I am aware of at least one vendor that manufactures a complete line of citric acid-based passivation materials. An added benefit when you use a commercial product is the ability to talk to the vendor and get technical support.
Originally published in the October 2015 issue.