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High Purity Water and Passivation

I am working on a document to decide when to passivate 316 stainless steel parts. We currently have a passivation tester that has ranges for when the metal is passive and non-passive. I was wondering if there was any data on stainless steel and High Purity Water systems. Information such as corrosion data and at what concentration and time frame does the part need to be passivated. Also, how big of a factor is temperature in HPW systems and stainless steel?

Adam Musulin
- Boulder, Colorado, USA
2002

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2002

Adam:

This is a complex question. I am not sure what method you are using to measure whether the surface is passive or not. Some of these methods are not very good and not recognized by ASTM, SAE and other organizations. HP systems usually require a chrome oxide: iron oxide ratio of at least 2.0, and sometimes 3.0. The only accurate way to measure this is with ESCA and AES tests, which are quite expensive. There are simpler, GO/NO GO tests itemized in ASTM A967, ASTM F86 or ASTM F1089. These are the tests that are recognized in the industry. In order to provide the maximum in corrosion resistance ALL HP grade stainless steel needs to be passivated or electropolished and passivated. We can supply you data to show the difference if you need it. Good 316 ss or better grades will normally not corrode unless stressed in some way (like disinfecting with bleach), but to attain the best in corrosion resistance requires passivation.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois