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Parameters for nitric acid passivation of piping by circulation

I have been working with pharmaceutical equipments manufacturer for last couple of years. We manufacture WFI and RO plants and we do passivation of pipings internal product contact surface by circulation nitirc acid in pipings. But I don't know what should be the concentration of nitric acid solution, temperature of solution and what should be acid circulation time to achieve right passivation results.

I would be grateful if some one can answer my question.

Manoj Jangid
Water management solution company employee - Ahmedabad, Gujarat, India
April 28, 2008

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Manoj,
The best references, as alway, are the industry specifications. In this case ASTM A967. You can also use a copy of the now defunct mil spec QQ-P-35C [link is to free spec at Defense Logistics Agency, dla.mil]c, as the nitric procedures listed within remain largely unchanged in the specs that replaced it.

You may also chose to passivate your pipe systems with a citric acid based formulation. Let us know if we can help.

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois

June 3, 2008